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“TNE ANALYTIC REPRESENTA LION OF SUB.
STITUTIONS ON . POWER OF A PRIME
NUMBER OF LETTERS WITH A. DIS
CUSSION OF THE LINEAR GROUP.
=
A DISSERTATION PRESENTED TO THE FACULTY OF ARTS,
LITERATURE, AND ~CIENCE, OF THE UNIVERSITY OF
CHICAGO, IN CANDIDACY FOR THE
PEGIREE.-+OF. “ROC TOR )F
PHILOSOPHY.
By
LEONARD EUGENE DICKSON.
Reprinted srom the Annals of Mathematics, 1897.
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THE ANALYTIC REPRESENTATION OF SUBSTITUTIONS ON A
POWER OF A PRIME NUMBER OF LETTERS WITH A DIS-
CUSSION OF THE LINEAR GROUP.*
By Dr. Leonarp Eveene Dickson, Chicago, Ill.
_ TABLE OF CONTENTS.
Preface with literature.
PART I.—AwnatytTic REPRESENTATION OF SUBSTITUTIONS.
Section I.— General Theory.
Arts. 1- 2. Definitions.
3. Uniqueness of representation.
4— 5. Lagrange’s interpolation formula,
6— 7. De Polignac’s result anticipated.
8. Matrix property of substitution quantic.
9-11. Generalization of Hermite’s Theorem.
12. Reciprocal of a substitution quantic.
13-15. Residue of a multinomial coefficient (mod p).
16. Reduced form of substitution quantic.
17. Degree not a divisor of p” — 1.
18. &* a substitution quantic if % is prime to p" — 1.
Szotion Il.—Quanties of degree prime to p.
20-45. Complete determination of reduced quantics of degree = 6 suitable on p” letters.
46-50. Preliminary study of septics.
51-56. Quantics with an infinite range of suitability.
Section ITI.— Quantics of degree a power of p.
57-59. Quantics with all exponents powers of p.
60-68. General theorems on quantics of degree p”.
69-74. Determination of all reduced SQ[p"; p"], for p” = 7 and partially for p” = 11.
75-77, General types of SQ[ p”; p”].
Section 1V.—Degree a multiple, not a power, of p.
78-82. Determination of all reduced SQ [6; 3%].
82-86. Special results on SQ[6; 2”].
Miscellany.
87. Table of all reduced SQ[%; p”"], k= 6.
88-89. Analytic generators of substitutions on 7 and 5 letters.
90. Enumerative proof of Wilson’s theorem.
* Dissertation accepted by the University of Chicago in partial fulfilment of the requirement
for the degree Doctor of Philosophy.
149084
66 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
PART II.—Linzar Grovp.
Section I.—Linear homogeneous group.
1. Definition of a linear homogeneous substitution.
2. Literal and analytic composition ; group.
3. Restriction to prime modulus.
4, Order of linear homogeneous group.
5. Transformation of indices; determinant invariant.
— 7. Decomposition of a linear homogeneous substitution.
2. Factors of composition of linear homogeneous group.
3. A triply infinite system of simple groups.
Srotion IIl.— Linear fractional group.
14. Definition, exhibition, and order.
15. Group of linear fractional substitutions with determinant unity is simple.
16-17. Remarks on systems of simple groups.
Section III.— The Betti-Mathieu group.
18-19. Identification with the linear group.
20. Order of the group.
21-24. Mathieu’s special type of substitutions.
PREFACE.
This paper is an application of the Galois Field theory, a conception of
fundamental importance in Higher Algebra. This theory is here presupposed
and will be used in the abstract form given it by E. H. Moore.’ Reference
may also be made to Galois,’ Serret’, Jordan*, Borel et Drach’, in a note by
the latter the Galois Field being developed in its abstract form.
The aim in Part I is two-fold: (1) the complete determination of all
quantics up to as high a degree as practicable which are suitable to represent
substitutions on p” letters, p being a prime, 2 an integer; (2) the determi-
nation of special quantics suitable on p” letters, where for each quantic the
combination ( p, 2) takes infinitely many values.
It is a remarkable fact that, on the one hand, the conditions necessary
and sufficient to determine a substitution quantic are found by multinomial
expansions,—on the other hand, one of the observed types of substitution
quantics having an infinite range of suitability is a multinomial expansion
‘Moore, Proceedings of the Congress of Mathematics of 1893, at Chicago.
* Galois, Bulletin des Sciences mathématiques de M. Férussac, vol. 13, p. 428, 1830; reprinted
in Liouville’s Journal de Mathématiques, vol. 11, pp. 398-407, 1846.
*Serret, Algebre supérieure, fifth edition, vol. 2, pp. 122-189.
‘Jordan, 7’raité des substitutions, pp. 14-18.
°Borel et Drach, 7'héorie des Nombres e¢ Algébre supériewre, 1895, pp. 42-50, 58-62; Note, pp.
343-350. f
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 67
(multiplied by a power of the variable) and the other type a reverse-binomial
expansion (see $§ 53-54).
The results of this investigation warrant the conjecture that there exist a
small number of types of substitution quantics of such wide ranges that together
they represent all the py”! substitutions on p” letters. Examples where appar-
ently isolated quantics fall under a general type (when it is not reduced) are
given in § 77.
While the aim in Part II* is primarily to generalize the work of Jordan
on the linear homogeneous group, the treatment has been considerably modi-
fied to render the subject more accessible. The desire being chiefly non-¢yclic¢
simple groups, the modulus is supposed prime, which affords much simplifica-
tion. On the other hand, many amplifications occur and also the correction
of several errors (indicated by foot-notes).
In the same investigation there may occur marks of the Galois Fields of
orders p', p”, amd p”™, n > 1, m > 1, when (as a useful notation) we use
small Roman, small Greek, and capital Roman letters respectively.
Literature on the analytic representation of substitutions :
M. Hermite, Sur les fonctions de sept lettres, Comptes Rendus des Seances
de L’ Académie des Sciences, vol. 57, pp. 750-757, 1863.
Hermite’s results (in whole or part) are given by:
Serret, Cours D’ Algébre supérieure, vol. 2, pp. 883-389 and 405-412 ;
Netto, Swbstitutionentheorie, ch. 8 ;
Jordan, 7raité des Substitutions, pp. 88-91 ;
Borel et Drach, Zhéorte des Nombres et Algebre supérieure, pp. 305-807,
1895.
Enrico Betti, Sopra la risolubilita per radicali delle equazioni algebriche
irriduttibili di grado primo, Annali di Scienze Matematiche e Fisiche, vol. 2,
pp. 5-19, 1851; Sudla risoluzione delle Equazioni algebriche, ibid, vol, 3, pp.
49-115, 1852 ; Sopra la teorica delle sostituzioni, ibid, vol. 6, pp. 5-34, 1855.
Emile Mathieu, J/émoire sur le nombre de valeurs que peut acquérir une
Jonction quand on y permute ses variables de toutes les maniéres possibles,
Journal de Mathématiques pure et appliquées, second series, vol. 5, pp. 9-42,
1860 ; Mémoire sur Vetude des fonctions de plusieurs quantités, sur la maniére
de les former et sur les substitutions qui les laissent invariables, ibid, vol. 6,
pp. 241-323, 1861.
F. Brioschi. Des substitutions de la forme
n—3
I iy he ul en
* For the suggestion of this generalization as leading to a triply infinite system of simple
groups, as also for much yaluable aid throughout the investigation, I am indebted to Professor
Moore.
68 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
pour un nombre n premier de lettres, Mathematische Annalen, vol. 2, pp. 467-
470, 1870.
De Polignac, Sur la représentation analytique des substitutions, Bulletin
de la Societé Mathématique de France, vol. 9, pp. 59-67, 1881.
A. Grandi, Un teorema sulla rappresentazione analitica delle sostituziont
sopra un numero primo di elementi, Giornale Matematico del Prof. G. Batta-
glini, vol. 19, pp. 288-245. The conditions are found under which
5 gies
eP-*§ 4 an 2 -+ ba
shall represent a substitution on p letters. A generalization by the same writer
is given in’ Reale Istituto Lombardo di scienze e lettere, Leendiconti, Milano,
vol. 16, pp. 101-111. For abstracts of each see Fortschritte der Mathematik,
vol. 13, p. 118, 1881, and vol. 15, p. 116, 1883.
J. L. Rogers, On the Analytical [representation of Heptagrams, London
Mathematical Society, vol. 22, pp. 87-52, 1890.
L. E. Dickson, Analytic Functions Suitable to Represent Substitutions,
American Journal of Mathematics, vol. 18, pp. 210-218, 1896.
PART I.—AnatytTic REPRESENTATION OF SUBSTITUTIONS ON A POWER OF A PRIME
NuMBER OF LETTERS.
Section I.—General Theory.
1. Let ¢ be any mark of the Galois Field of order p”, p being a prime and
n a positive integer. Also let ~(&) be an integral function of ¢ having as
coefficients certain marks of the @#'[p"]. The replacing of the letter lz by
the letter dy. defines a substitution on p” letters, in notation,
e == O45).
2. In order that ¢ (¢) shall indeed be suitable to represent a substitution
on the marks
Vi ie OM ee po)
it is necessary and sufficient that v (™), ¢ (M4), ---, Y (Mp1), be identical with
Moy Py +++ Upn—1 except as to order. If an integral function of degree / belong-
ing to the GF’ | p”"| satisfies these conditions, it will be called a substitution
quantic of degree & on p" letters and denoted thus
SQ[z; p").
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 69
The degree /# will be supposed < p” owing to the equation
eee,
satisfied by every mark of the field.
3. Theorem. Two different quantics ¢(&) and $(§) belonging to the
GH'[ p"| cannot represent the same literal substitution.
For if the substitution replace the index yp; by py, fori = 0,1,..., p? —1,
then must
Gh Wee tip i hh ( 14,) (tee Oe ps 1);
CO ie) ae U
is of degree p" — 1 at most but has ~” distinct roots y; It is thus an identity
in &.
Thus
4. The most evident substitution quantic is the integral function ¢ (¢)
which gives Lagrange’s interpolation formula:
n—]l es
egg D vl)
¢ (é) ; = (= ms ti) Fm) (1)
where @), 4, ..., @pn_; is any permutation of 0,1,..., py’ —1, and where
pr—1
UES) = af (¢ —
and /” denotes its derivative. Thus
represents the substitution
Me. Pee rise gees |
Cae Pays «+> ig ee J
5. Following Hermite’s method* for the case n = 1, we may give (1) a
simpler form. ;
In the G/F'[ p"),
Le vie Pa or (eet Le
pl 5, pt may é)
is : VW fa\>
Mats oan
a i=0 Ser vi
Taking 4, = 0, so that
pe = 1 = 0 (Hee ey 2 1)
- * Cf Serret, 1. c. 2, pp. 384-5.
70 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
and performing the division by § — yy,
pr—]
L > © =
g (E) = — pa, (€?" — 1) — 2 Halen te fee ee ees
‘i=
Arranging according to powers of ¢ and noting that*
prt
fa eas
=
we reach the desired quantic,
pr—2
es eee
¢ (§) = os" (2)
j=
where
pr—
= v a ee a
a; ne ed ai . be ij (7 : 0, ix a fie <> 2). (3)
i=0
It follows from § 3 that every substitution quantic on p” letters which
belongs to the G/’[ p”] is contained in the form (2).
6. The conditions on a, that an arbitrary quantic
n—]
g(§)= = af!
j=0
belonging to the G/’[ p"] shall represent a substitution on its p" marks yp, are
pr—l1
v pees es :
2, Gps SOX) (ee eee)
j=0
where o(4,) — fq, form a permutation of y, Applying the lemma proven in
§ 10, we have on adding the p” equations (4),
pr—l
aS ss
ee Opn a D (fi) =.0,
i=0
Taking a,,_, zero and dropping the first one of the equations (4), we have the
system of conditions
fy Gp = 04) ie Lee , pn —1). (4)
j=0
The determinantt ;
| | = Th, — 8
where’?,. 8 S12)... pa ere
We may thus express a; linearly in terms of 4, By equation (2) of § 5,
this is done by formula (3).
* pr—1 pr—1
s% sy
“ a= + My = 0 by § 10.
i=) : i=0
+ Baltzer, Theorie und Anwendung der Determinanten, p. 85.
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. (io
7. The gist of De Polignae’s paper is to actually solve equations (4) for
the case 2 = 1. Using @ and m for the integers corresponding to the marks
a and yp, his result is given in the form
Lay teen be RE oe
a= 2 {(—1)’ —2 } m
eed |
aid
where previously m,, has been taken to be zero. Subtracting
pot
(—1). 2 m,, = 0 (mod p),
i=l
re Pens
= (= 1 Cae ra = aes We ae — es ers THU ake foe)
— =
8. We may independently verify the inverse character of the linear rela-
tions (3) and (4) between the coefticients a; of any substitution quantic ¢ (¢)
and the marks ¢(4;) = ,, By (4’) the matrix
4
2 r—? ~
(hee ST Ae ee ee ee
ine je ee ? : VF
2 pr—2
el b] pr» UL pr—1) eine e) <9 (Tres
expresses 9(1;), 9 (M2), ---, G (Mp1) linearly in terms of @, %, ..., Gn»
Inversely, by (3) the cine
So ee ea DS ae en ee ee |
me pr—2 pr—2 eos, pr—2 |
ty és me 925) 3 3 Tae Upn-1
* " « ©
at pr-3 = p"--3 nae 3 pr—3 ee
| eae P LE ha ea ean
‘9 —— 'y ; == 2 ) Sino! Sty L Ayyn—1 J
expresses the latter linearly in terms of the former. To prove that the product
of the two matrices is the identity, let c’ denote the term in the product derived
from the 7th row of the first and the jth column of the second matrix. Then
pr—2 te Ae pr— 3 a. pr—2
ij pe M5 aes fi Kj ‘
Cy =—_—- i L
Thus
C= (pl) 4 1 (tg et nee 1 77 ere hs)
72 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
For 4,7 =.) 2). De oe
ee pn
i Ls
i) als pr—l pr—2 pr—2 pr—1
es a =—- IF shat SUR Sih peti ew UTE + By és
ae 2 J
i Nee
Hence ¢, = 0.if ¢ 9:
Fromrthe matrix expressing ¢ (y,) in terms of @, G,..., Gn—2, We derive
by reflection on its main diagonal and change of sign of all its elements a
matrix which expresses 4, Gpn_o, Zyn_3, ---, @, In terms of
gM) (i 1) Oe ep eed
9. Lemma. , 4), +--+ Mp1, being the marks of the G/’'[ p"] and ¢a posi-
tive integer,
n—] ;
—1l1fort?=p"—1
hier
i=0
For let ¢, denote the sum of the ¢th powers of the roots of the equation
belonging to the G/'[ p”]
Bye" =0 (yw =1). (5)
i=0
Applying Newton’s identity (as is allowable)
Opt Yi Fe + Ye Opn Fe HAG + hy, HO. (hl)
If for (5) we take the equation whose roots are y,,
ae eo eae
the proof of the lemma follows. |
10. Lemma. If, in the notation of § 9,
ss (teal oe, oon
Toad ae Girone) |z + 0, (mod p) Ube
and if all the roots of equation (5) be marks of the G/’{ p"], then will (5)
take the form
prs yee dae 0s
Applying Newton’s identity cited above, we find
Wa Sat, (ae Pye
Ves (2 + 0 (mod p) ey
CP ge ips 8h aide ee iN
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 73
To determine ¥,, Yop, - ++» Ypn—p» apply the identity
Dre Oe tke eo Vg be = O (AS p");
which reduces to
Oy, oa YnFk—p > YopFr—2p si\3 pases oe @ pn—1F pnt af Y pr F —pn — 0 .
<
By our assumption on the roots,
IF, = Ferpn-i+
Hence fork = p, + p—1,
YpF pp = 0.
Generally, for k = p" + Ilp—1, le p™ —1,
yl, Fyn == 0 =
Since o,,_, $ 0 by hypothesis, ¥,, = 0.
11. Generalization of Hermite’s Theorem.
The necessary and sufficient conditions that ¢(&) shall be suitable to
represent a substitution on p” letters are :
(1) Every tth power of ¢(&), for i << p" —1 and prime to p, shall reduce
to a degree = p"™ — 2 when we lower the exponents of € below p” by means of
the equation
Epn — = = O .
> = >
(2) There shall be but one distinct root of
3 p»—1
7 =;
g (§) ome
jem D
Proof: Suppose
After reducing exponents below p” let
rn
x p =f as
[y is S= > ames! ;
1=0
Give to € the values of the p” marks yw; of the field and add the resulting
equalities.
pr—l1 pr—1
re [e(y)]™ —— pra” — a,” 2 yy af kp =f. ag, ay ip
= [=
Hence by § 9, form < p" —1,
yn—]
(m)
~ [eo (4) = — ay .
j=—O
74 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
But if g (€) represents a substitution,
pr—l pr—1
2 [¢y (4) |" = py ign ee 0
7=0 7=0
ifm < p"—1. Hence a necessary condition is
Co Oe (Wie lion a Oe ce)
wr —-1
Also there must be one and only one of the marks ¢ (y;) equal to zero, i. e.
but one distinct root of g(¢) = 0. ‘
Inversely, suppose (1) and (2) are satisfied, so that
pel te Ne ae sa)
p ee 4) ( te : 4
= l¢ (4) | = Apr = ( ¢ $ O (mod Pp) j
pr—
I
[eo (4) ]?"7* = —140.
LY
vO
Then by § 10 the equation
pr—1
ff [7 — ¢ (w)l= 9
j=
takes the form
ea a Yor 7] + Yon == 0
7] (1 “= Won 4) ae Yoon == 0 *
or
If y,,_, + — 1, this linear equation is satisfied by the p” marks ¢(y,). These
must therefore be equal, and since their sum is zero, each must be zero. But
in this case the equation belonging to our field,
pr—2
gE) ==. 50,5 = 0
1=0
would have p” distinct roots ¢ = y; (i = 0, 1, ..., p” —1) which is impossible.
Hence y,,_, = — 1 and then, since one of the ¢ (,)’s are zero, y,, = 0. Thus
the marks (#,) are identical apart from order to the roots y; of
7" re y) —s @) ,
12. Reciprocal* of a substitution quantic. Given a substitution quantic
pr—2 ,
z = OAS) eee eer
* Rogers, l. ec. for p» = 7. His proof is objectionable, since he makes £° — 1 (mod 7) while
~ is to be taken = 0.
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 75
Suppose its reciprocal is
pr—2
Ee VS Q.pr—1-—t
= 2 pyr.
11
Then
yn—]
Sy = S [gy (E) = 2 aor",
I
after reduction of exponents asin $11. On the other hand,
pr—2
ft SV Q.-,p"—1—i+2z Q -t—1 9 --t—2 QD ag pr—I i2 agtt1
eee oe Sapna et pa se Pp
i=!
epr—1
Since 7 = ¢(€) is a SQ[ ; p”], then 7’ contains no term ¢’"” as long as
j
1. For on raising it
to the power ( 7” — 1)/k the coefticient of ¢”""' is 1 + 0.
18. Theorem. €*is a SQ [k; p"] if and only if k be relatively prime
to p” — 1.
For, / being any integer < p” — land prime to p, // must not be a mul-
tiple of p” — 1 (by § 11).
Corollary.—The extraction of /th roots in the GP’ py is always possible
(and then uniquely) if and only if / be prime to p” — 1.
Secrion Il.— Degree k prime to p.
19. Using the same method as in my papert giving a complete list of
SQ [(k; p'] for & < 7 and p any prime, I shall first determine all SQ[k; p”]
for k < 7, p any prime not a divisor of #, and n any integer. After a pre-
liminary study of septics, I shail conclude Section II with the derivation of a
remarkable class of substitution quantics of arbitrary odd degree /.
Complete determination of reduced quantics of degree k < 7 suitable to
represent substitutions on p" letters, p being prime not a divisor of k, $$ 20-45.
20. S is suitable for every p”.
21. is the reduced quadratic and is rejected by $17 since p” is odd.
22. zs Ae On.
(a) The case p” of the form 3m + 1 is rejected by § 17.
(b) The case p” = 38m + 2.
Then (& + a€)"t! gives (m + 1) aas the coefficient of ¢”"t'. Hence, by
* By making use of the indeter aay By ® further reduction may often be. made in ¢,(&).
The simplest form thus obtainable is called ultimately reduced. Thus 4 + 35 reduce to £4 + 32,
+ American Journal of Mathematics, Vol. 18, pp. 210-218, 1896.
78 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
§$11,a = 0; forif m + 1 were divisible by p, then would also 3m + 3 or
p" +1. The remaining form & is suitable by § 18.
23. ¢¢ + a& + Bé.
The only case to consider here is p" = 4m + 3.
The m + Ist power requires (m + 1)a=0 ora = 0.
(& + &)"+? requires Mee ah ie soda) f* = 0, provided p" > 7. Hence
8 = 0; for if m + 2 be divisible by p then is also 4m + 8 or p” + 5,1. €.
p = 5, while p must be of the form 4/ + 3.
But & is rejected by § 18, viz, by the power / = 2m be
J J > P WF
For the case above excluded, p = 7,” = 1, we have Hermite’s result,
the suitable quartics € + 36.
Reduced quintic & + a& + B& + 7&, S$ 24-44.
24. The case p” = 5m + 2. Hence v is odd.
The power m + I requires
(m+ 1)7 + Me. genie a= ();,
But m + 1 is divisible by p only ifp = 3. Thusif p ¢ 3,
By = (1)
The power m + 2 requires if p” > 7
(m + 2)(m
Toa
1)” (6apy + f+ (im — 1) 088} = 0.
Hence if p + 2 and p” > 7,
5 (6af7 + #) —Ta fs = 0. (2)
From (1) and (2), if p + 2 and ¢ 3 and if p” ¢ 7,
Ye am Ti he (3)
The power 7 + 3 requires if p” > 7
hes doy? + 66%)? + = F (100%? + 30a%8% + 5465)
(m —1)(m — 2 ne 2 m —1)(m — 2)(m — 3),
4 zat *) (Gaby + bata") + | Aire Ue
Now m + 3 is divisible by p only if» = 13. Hence if p is neither 2 nor 13
we may divide off the binomial factor ¢,"**. Multiplying the resulting equa-
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 19
tion by 5*, replacing 5 (m — 1) by — 7, etc., we have for p” not 2”, 7', 13” the
condition
20a (5y)* + 1508? (57)? — 700? (57)? — 1050026? (57) — 875u/f' + 8405 (57)
+ 10500%f? — 3407 — 0. (4)
Applying (1) to (4):
15006? — 8750p = 0,
from which by (3) we find # = 0.
For the proof that the resulting form
Be + Bas? + aff
does represent a substitution on p” = 5m + 2 letters, a being arbitrary, see
Secbe.
2h. ne case p” == 13" == Ben + 2.
The powers m + 3, m + 4, m + 5 give identities. The power m + 6
requires
Co else nr =.0 or a B=. 0:
For, 5m + 2 — 0 (mod 13)1. e. m = 10 (mod 13). Thus c¢/"* or ¢/%** is + 0
Oily 0K cal 2 o.10, 14, 15,°16,26,...,, by §'14.
It follows from this equation and (3) that 8 = 0.
26, Che. case p —- 1, n= 1.
Hermite gave the complete list of suitable forms :
SVy
Snes
& + af + & + 8s, a = quadratic non-residue of 7.
& + af + 3a, a = arbitrary.
The last may be written 5& + 5a& + a6.
27. The case p” = 3” = 5m + 2.
The powers m + 2 and m + 3 require by (2) and (4)
2h = ap (2’)
a — oP + afft—a = 0. (4')
Since n S 3, 5m + 2 = 0 (mod 27) or m = 5 (mod 27). Hence e"** or of"*"
IocteOnl yl Awaeeeleeneo, LOLI or. 27.
The power m + 6 thus requires, if 2 > 3,
Gye Up eens 3 OK (5’)
80 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
Thus § = 0 and (4’) becomes
a(iyt@)(7+y7e? —a)=—0.
Ifa+0,7 = — @; for if the last factor vanishes,
(Com ene ee ;
while — 1 is a not-square in the G/’[3'] and hence in the GF [8"], n being
odd.
If a = 0, the power m + 9 of & + 7€ requires
MOA alae ca eee
ete ge ty pt a)
The possible form is thus 5 + 506 + o&& when n > 3.
28. The case p” = 3°.
The powers 11 and 13 require
B+ af =0 (5”)
et deo wT aes ae eo (6")
Suppose § +0. Then by (2’), # = — a’, so that (5’) is satisfied and (4’)
becomes
Og i ee
But if either 7 = 0 or 7 = @, (6”) requires that 8 =0. Since f = 0 we have
y = — @ as in the case n > 3.
29. The case p” = 2" = 5m + 2.
Since 7 S 5, m = 6 (mod 32). The power m + 5 requires
Cite ee mt bot ae (oregon
Applying (1), 7 = a’, this becomes
e+) =O. © (7)
The power m + 7 requires Ligtre tO,
af+a¢h + a*=—0.
Applying (1) this becomes a’f* = 0. Hence # = 0.
For n = 5, the 13th power requires a condition which on applying (1)
becomes exactly the fourth power of (7).
For n = 5, the 15th power requires
P+ BP + all + BP + ah + byt + BP + by + RP + By + aft = 0.
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 81
Applying (1) this becomes
aft (a + aG* + BY) —0. (8)
If 6 + 0, #° = @ by (7), whence (8) becomes a’ = 0. Hence must 8 = 0.
30. Summary of §$§ 24-29. The only possible reduced substitution quintic
on p” == 5m + 2 letters is
beverebas 4 aes) « arbitrary,
except for p = 7, = 1 when we have two additional forms :
£4 of
t
P4 ah + 4 80%,
where @ is a quadratic non-residue of 7.
31. The case p” = 5m + 3.
The power m + 1 requires (m+ 1)f8=0. Hence ifp+2,8=0. The
power m + 2 of & + a& + 7€ requires
Cae - ae Ae : Say ae ee a = 0) , (1)
If p + 7 we may divide out ¢,’"**, giving readily
257? — l5dey + 2a = 0.
Hence, if p + 2, + 7, either 57 = @ or 57 = 2a”.
The power m + 4 requires for p” > 13,
Oy ero eee LUC a la 4 Cot, Sale Gt a == 0. (2)
If p is not 2,3, 7 or 17, we may divide out (m + 4) (m + 3) (m + 2)
(m + 1)m, multiply by 5*.7! and replace 5(m — 1) by — 8, ete., giving
2104 (57)* — 8 .140a' (57)? + 8. 13. 21a (57)? — 8.13 . 18a’ (57) + 23. 260° — 0.
If 5; = @’, this becomes
a’ (210 — 8.140 + 8.13.21 —8.13.18 + 23.26) =—0,
in which the coefficient of @ is identically zero. If 5; = 2a’, the coefficient
of a’ reduces to — 10. Hence in this case 4 = 7 = 0.
Thus for p” not 2”, 3", 7, 17" or 18, the only possible quintic on py” =
5m + 3 letters is reducible to
SIS Ya ST aie
82 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
32. For p = 13, n = 1, I have elsewhere* shown that the only suitable
quintics are
56° + 5u& + a&, a@ = arbitrary.
5& + 5a& + 2a, a = quadratic non-residue of 13.
33. The case p” = 17" = 5m + 3.
The value 57 = 2a’ is rejected since the equation
be? - halt = Aas = 0
has a solution + 0 for every a when p = 17. Thus
5 (€* + a& — 3a’) = 0
has the solutions ¢? = 44 and — 5a. Now — 5isa not-square in the G/’[17']
and hence also in the G/’[17"], x being odd. Thus whether a be a square or
a not-square, we have a solution ¢ + 0 belonging to the field.
34. The case yp" = 7” = 5m + 3d.
The condition (2) of § 31 becomes
5.8. 9a, — 230 = 0.
Thus either == 0) ory ion,
But the power m + 6 of © + 7€ requires 7’ =
The only possible form is thus 5& + 5aé* + a6.
35. The case p” = 3” = 5m-+8.
The condition (2) of § 31 becomes since m — 21 (mod 27),
Oe ; 200°? - oh = a + ii — O .
Hence 57 = a’.
36. The case p” = 2” = 5m + 3, supposing x > 3. Thus 5m — — 3
(mod 2’) or m — 25 (mod 128).
The powers m + 2 and m + 4 of & + a& + B& + 7€ give
7 ay + af? = 0
at +a=0.
Heneaif.a == 0,7 =.0 Sila 2100 eee
But the power m + 22 of & + #¢ requires
Cue ‘ jes — p® — O :
The only possible form is again 5& + 5a& + a.
* American Journal of Mathematics, vol. 18, p. 213.
DICKSON.
ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 83
37. The case p” = 2°.
The third and fifth powers require respectively
Yta@ayrit+ af = 0
TY ay' + a8 ==1()7
of which the former is the square of the latter. Hence either 4 = 7 = 0 or
Die pate
But & + f¢* vanishes for ¢ = f®, every mark in the GH [2°] being a
cube by § 18.
By replacing = by a'*¢ and 7 by a’, the quintic
becomes
=
-
Y (é) == ra aE ae -- (a*y ae aty*) &2 at ve
OUP +O + +E + rh
Hence the quintic ¢(€) will vanish only for ¢ = 0 if the resultant of
P+&E + (747) 4 7é and & = 1
is +0. This resultant may be written as a cyclic determinant whose first
row is
Ore Oe ee 7 eer Oe
On expansion it becomes
rete tae fae he DG aH)»
which is + 0 only when 7 = 1.
The only suitable quintic on 8 letters is thus
e 4 06° + ws.
38. Summary of $$ 51-37. The only possible substitution quantic on
p” = 5m + 3 letters is reducible to the form
Bot bak oe, a arbitrary ,
except for p” = 13 when we have the additional form
Dee tOUs 20,
a being a quadratic non-residue of 13.
39. Theorem.
5 + 5as3 + oS, where «a is an arbitrary mark of the
GF'{ p], is suitable to represent a substitution on its p® marks, if p is a prime:
number of the form 5m + 2 and n is odd.
84 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
For if not we must have for two different values of €, say 7 and g, the
following equation :
57? aN Sax? SE an — dy? a 5ag® =" ao
or
(9 — 9) {50 eet IG Ora Ne Para erate earn
Hence since 7 ¢ ¢,
Sift Ee +e +ae+yg+¢)p+e=0. (1)
(a) Suppose p > 2.
Making the substitution
i oe i ee
5 {5M + LOR? + pt + 8a”? 4+ av?} + & = 0.
Multiply by 16 and substitute
202 = 40—a, 4 = 46 —a4.
We thus reach the simple form ,
16 (eo? + 1006 + 50°) = 0,
or
(0 -|- 5a) = 2007 = 5 (20) F
But* + 5 is a quadratic residue of no odd number of the form 5m + 2
or 5m + 8. Hence 5 is a not-square in the G/'[ p"], n being odd and
Dp = OM. seas
(b) Suppose p = 2.
Making in (1) the substitution
Pa Para a reals
M+ ah + a = (Ph + pt a). (2)
Put ? = v and multiply through by » + pw:
Ytar+av=w + a/+ en. (3)
But, by § 18, = is suitable to represent a substitution on 2” letters, 2 odd, and
hence is also
§+a~pt+@[8 4 a 4+ @.
Hence (3) has no solution in the G/’[2”] except » = yp, when by (2) we find
y= pL == @;
* Gauss, Disquisitiones Arithmetical, Art. 121.
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 85
Hence if (1) is satisfied, we have
2
Ths a Ue
But this set of values for 7 and ¢ is impossible since
wo + afw + a0
has no root in the GF'[2"], n odd, if a+0, i. e. if 7 +g. For writing
w = @4, it becomes
eee ee OF
We thus need only prove that # — 1 = 0 has no root other than 6 = 1 in
the G/F’ [2"], n odd. But if there exists a root + 1 of
Ce 1)
(and thus having the exponent 3) which is also a root of
Goan Lea
then* must 2 be even.
A general theorem comprising the one here proven is given in § 54.
40. The case p” = 5m + 4.
The power m + 1 of & + a& + BE + yé gives a = 0.
The power m + 2 of & + fs + 7€ requires
Geen Oe,
Hence if p + 2, + 3, we have fy = 0.
The power m + 3 requires, if p” > 9,
(Pah gap aa reed ott UF
Now m + 3 is divisible by p only if p = 11, when p” is not of the form
5m + 4. If p = 2 (and thus n S 6, we have m — 12 (mod 64). Hence for
every p” > 9,
SF pice =e oe
Thus for p + 2, + 3, 8 = y = 0 and © is the only suitable form.
41. The case p” = 3" = 5m + 4,2 > 2.
The power m + 4 requires, since m — 1 (mod 9),
oh4 1087 = B= 0.
Hence © is the only suitable quintic.
*Moore, 1. c. § 46.
86
tively,
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
42. The case p” = 37.
The fourth, fifth, and seventh powers of ¢ + f€ + 7€ require respec-
rdit+r)+F#=0
Pau+/7)=0
aad +7) =0.
The solutions of these equations are
B30 Sy s=0 Gand. OFS 0 eal eee
The suitable forms are thus
SUC CNY ete igh a
since if the latter vanished for ¢ + 0, €* = 2. Indeed # + 23° represents the
literal substitution,
(0) (1,1 =e O19) (= 0 ee eee
43. The case p” = 2" = 5m + 4.
The power m + 11 requires, since m = 64/ 4+ 12,
Cee F has == Bon ee 0) :
Hence § = 7 = 0 and © is the only suitable form.
44. Summary of $$ 40-43. © is the only reduced substitution quintic on
nr
Pp
= 5m + 4 letters, except for p” = 3’ when we have also ¢ + 2c.
45. & + af + BE + 7s? + O86.
p” = 6m + 5, since here p is prime to 6 and since p” + 6m + 1.
The power m + 1 requires 4 = 0.
The power m + 2 of & + fe" + 7& + OF requires
230 + 7? = 0.
The power m + 3 requires, if p” > 11,
6y0" + m (20 + 3/7”) = 0.
The power m + 4 requires, if p” > 17,
o +2 (20pa* + 208/49 + 7°) + M4) emo + 15044) = 0.
(1)
(2)
(3)
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 87
Substituting 7° from (1) into (2) and (3),
670? — 4mf?o = 0 (4)
A OWbie oss m\(m — 1) a5
eH ae Bd? — 4m il 1) os = 0. (5)
I 5 :
From (4) and (5)
M4 4m (2m == 1)
Oa
5
od = 0. (6)
Multiplying (1) by m° and subtracting from (2),
670? + 2m??? — 0.
Ii p = 5, m = 0 (mod 5), so that yo? = 0 and then by (6)0 = 0. Ifp: 5,
suppose; +0. Then
mPr = — 30.
Substituting this in (5),
230* — 4m(m — 1) f'0 = 0.
Combining with (6),
(41m — 18) ot = 0 or 3130 = 0.
Since 313 is a prime not of the form 6m + 5,¢0 = 0. Hence must 7 = 0, so
that fo = 0 and by (6) d= 0. But the power 3m + 2 of & + f& gives
get? and no other term with exponent divisible by 6m + 4. Hence there is
no suitable sextic when p” > 17. I have shown* that p = 17, = 1 leads to
no suitable septic ; while p = 11,7 = 1 leads to the following substitution
quantics :
A preliminary study of septics, $$ 46-50.
ay £5 Q&4 We Ne2 oe
Set Ose ee oun 11 oe rr Okeer tet,
46. The case p” = Tm + 6.
The power m + 1 requires a = 0.
The power m + 2 requires, if p + 2,
Tpe + Tyo — B= 0. (1)
~ American Journal of Mathematics, Vol. 18, pp. 216-217.
88 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
The power m + 3 requires, if p > 5 and p” + 13,
9 9 a2 la¥. Dw) 20 gt ia la
(xe? + Oe) — 7 (6Pre + 38/0" + 68770 4 9 7) + 9 Cer (2)
Rejecting the special values, 2, 5, 13, etc., we may prove that if any one
of the four coefficients /, 7, 0, ¢ be zero, then all are zero. To handle (1), (2)
and the very lengthy conditions given by the powers m + 4 and m + 5;
when f, 7, 0, ¢ are all + 0, is perhaps impracticable.
Suppose, for example, 7 = 0. Then (1) and (2) become
Thus =-0 4 foriiynot
Te 32 and thusggy—= of -
The power m + 5 of & + fé + e€ requires
Teo — 7! 15 Ret + 73. 6522 — 7, 180 fhe? + a 27 g, _ 13.51
- Pe — 14 Baie)
If # + 0, # = Te and the last equation becomes — f° = 0. Thus if 7 = 0,
then 8 = 0 = ¢ = 0, certain values of p” being excepted.
47. The case p” = 7m + 5.
The power m + 1 requires 6 = 0. If either a, 7, or ¢ be zero, we can
prove that all are zero. If 0 = 0, the conditions given by the powers m -++ 2
and m -++ 4 (of 5 and 19 terms respectively) are satisfied by
Cte) 2G" ite aes.
48. The case p” = 7m + 4.
The power m + 1 requires, if p + 3,
7 = 20".
We may prove that if a ='0, then B= jy =6 =e = 0; thatil p — 0 then
0 =) andre = 0%
49. The case p” = Tm + 3.
The power m + 1 requires, if p ¢ 2, 70 = 3af.
We may prove that if a = 0, then B = 7 = 0 =e = 0; if 8 = 0 then
0 = 0 and the conditions given by the powers m + 2 and m + 4 (containing
seven and twenty-one terms respectively) are seen to be satisfied by
\ Yemen Lee ees
50. The case p® = Tm + 2.
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 89
The conditions are quite unwieldly even when a = 0. If 3 = 0, then
GeO ma AOS eS Oe
Quantics with an infinite range of suitability, $$ 51-56.
51. We have found that the quintic
b=” 4 bak? aE ,
a. being an arbitrary mark of the G/’'[ p"], is suitable to represent a substitu-
tion on its p” marks, if and only if p" be of the form 5m + 2. Also in our
preliminary survey of septics, the quantic
CE ae 2. Take? 4 ae ,
a. being an arbitrary mark of the G/'[ p"], stood out in a prominent way as
probably suitable on its py” marks if and only if p” be of the form 7m + 2 or
7m + 3. Note further that there is no suitable cubic other than €. Thus is
suggested the possible existence of a quantic of odd prime degree & which is
suitable to represent a substitution on the marks of every G/'[ p"], except
when p” is of the form Am + 1.
52. Suppose the reduced quantic belonging to the G/’[ p"],
Si SAC a ks es Co eae SiR ad a (1)
whose degree / is an odd prime number ¢ 7, is suitable to represent a substi-
tution on the p” marks of the field for every p” of the form Am + 2, km + 38,
km + 4, ..., or, km + (k — 3). We do not at first assume it suitable on
p" = km + (k — 2) letters, in which case the power m + 1 requires
(m4 Ly a, == a, == 0, 1f pt 2.
For p” = km + (k — 3), the power m + 1 requires
(m +1)a,+ (m = 1)m fit ee A),
or, if p + 3,
k= 33
2
9
hie Ce
For p" = km + (k — 4), the power m + 1 requires if p ¢ 2,
ka, = (k — 4) aa, .
For p" = km + (k — 5), the power (m + 1) requires, if p + 5,
_ k(k—5)
: ger as iy
Ka, 9 (45° + 20,44) + ( Z ase ) Gees
90 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
or
2 A) : kik —5
; kG, = ( kts E ») Os ae ( 7 5) Oy
For:p” = km + (& — 6), the power m + 1 requires, if p + 2, + 3,
ka, — k (k —B6) (020 + O04) + (ie) ee ay eer Ae
or
Ka. = (
aes
k — 5)(k—6) _,
9 a.
Similarly, for p” = km + (k& — 7), the power m + 1 requires, if p ¢ 7,
(ees 31.2) @—T) 1 4 b= 8) UB a
Ka, =
for p" = km + (k — 8), p ¢ 2, the power m + 1 requires
io, — 4 —9) © cil (k= 8) p54 4 Bk =e ws BS)
for p" = km + (k — 9), p + 8, the power m + 1 requires
5 he
ee ee ( Cate
ae (he — 6) (eB) ee) 4 k— T){k— 8) (k—9)
ee 2.3.4.5 4
It would be impracticable to attempt to calculate the general coefficient in this
way. Itis to be noted that if p > & every coefficient is expressed uniquely
in terms of a, and 4.
53. The sum s, of the /th powers of the roots of the cubic
e Os
is given by Waring’s formula thus :
DY m(A or A, sic A, — 1) r ne
Bae tin p ye - 285} 3
* acre (Apes ea SPOS SES (3)
where z (¢) = ¢! with the convention that z(0) = 1, and where the summation
extends over /,, 4,, 4, such that
peas Say yee Bee 7
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 91
Arranging according to descending powers of €, we have
> feo) i ‘ e383
Pia Se dace se “Egy
apa , K—A =
azgk—t 1 © gg Eb-s
ke
Ne es ah eek Os deal See Ie 2y,Ek—7
ba oth 0) (el k —6)(k—T7 2) ses
iE DIO, er WED caste
k — 6) (k — 7) (k—8) k — 7) (k — ay
ESSE DE) 3, PDR 8) 0} on
(k — 6) (k —1) (k —8)(k—9) 5 , (E—T)(k—8)(k—9
= BI A ho 4h
Thus the first ten coefticients in s, are exactly the corresponding coefii-
cients of the quantic (1) as calculated in § 52. A complete identification of
s, with (1) will be carried out for the most interest case, viz, when a, = 0,
which happens when the range of suitability of (1) excludes only the com-
binations p” = km + 1. For then by § 54 the quantic s,(€) will satisfy the
conditions derived by the method of § 52 which have an unique solution in
terms of 4.
For a, = 0, (3) reduces to
Pe (k —1—1) oe.
AG Zest \ ; Ek-2l
i eh esa i
Thus
Cee ead (i ba) i(k cae eat) Ek a
k ay 0 ae lh >
ein ee TA c= a Dea a
(5
where 7, and 7, are the roots of the quadratic
7 — iy —7 = 0. (6)
a
54. Theorem. Zhe quantic
(k—-1)/2 i af :
AG ajae+ oP EID 20+ 1) aera
where k is any odd integer® not divisible by p, and a any mark except} zero of
the GF'[ p"), is suitable to represent a substitution on its p” marks, if and only
ego: be be relatively prime to k.
* kis ast necessarily prime. ‘The proof in § 52 that 0, .(&, @) is the on ly quantic w Ay ‘the range
of suitability p" = km-+ 2, +3,...-+ (k — 2) requires that & be a prime number.
+See § 18.
) Oia Sager it Ae
(4)
92 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
We are to prove that under the named restrictions
0.8, a) = 8 (7)
has a solution € in the G/’[ p”], § being an arbitrary mark of that field.
Now by the transformation
Coal : Hone Aee a. /
Sa hart (6)
the quantic is given the form
ee la ;
Coie a (5’)
Thus equation (7) becomes
77* — Byk — at = 0. (7)
Substituting Y = 7, this becomes
Y?— BY +4 (—af¥=0,
which belongs to the G/'[ p"] and is for every § resolvable in the G/’'[ p*”"] but
not in the GF'[ p"). Call its roots Y and Y.
_Now the equation
pn Ve
is solvable in the G/F'[ pp], Y being an arbitrary mark of that field, if and
only if p’” — 1 be relatively prime to 4.
Then if 7 be a mark of the G/’'[ p*"| satisfying (7), we must prove that
falls into the lower field G/’'[ p"]. Since Y and ¥ are conjugate marks with
respect to the G/'[ p"] whose product is (— a)*, we have
= — 4.
Hence
f= 9 —a/gaygt+a=F
so that indeed* € belongs to the G/'[ p"].
55. The algebraic roots of (7) are
pene ge” (iON Lea ey
where
ots h ila/2 el Gaara
: * Moore, 1. ChsipLs 7
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 93
and ¢ is a primitive “th root of unity. This is a straight generalization of
Cardan’s formula for the roots of the cubic and also of Vallés’ solution of the
quintic*
a ,
at Pa).
m we Oa? = 5
It is evident that the algebraic solution of (7) for a and arbitrary is
equivalent to the extraction of the Ath root of an arbitrary complex quantity
and hence equivalent to the partitioning of an arbitrary angle into /# equal
parts.
56. The study of the quantic ¢, (€, a, a,) derived as in § 52, or conjec-
turally (when a, + 0) as in § 53, is made here only for the case a4, = 0. It is
to be expected that, for a, + 0, it is a substitution quantic at least for certain
special values of &, p, n, a4, and a, Thus if & = 5, p = 7, we find
oo oe = Gas “ts BOy Ss
which by § 30 includes the three types of quintics suitable on 7 letters, as well
as the one suitable on 7” letters, » being odd.
Section III.— Degree a Power of p.
Quantics with all exponents powers of p, $$ 57-59.
57. Theorem.t The reduced quantic
m & :
¥ (x ) = D: A,X a Re
it
belonging to the G/’[ p’"], will represent a substitution on its p”” marks if
and only if
7(X) = 0 EL}
has no root in the GF'[ p””] other than XY = 0.
For it will be a substitution quantic if and only if it be impossible to find
two different marks A, and X, of the G/'[ p””] such that
1(X,) = 1 (44)
Veet 0.
or
Corollary. A?" — AA” represents a substitution on p”” letters if and
only if A = O or A isa not (p — p") power in the Cie.
*M. F. Valles, Formes imaginaires en Algebre, Vol. i pp. 90-92, 1869,
+ I reached this result independently. Cf. Mathieu, 1. c. Vol. 6, 1861, p. 275 ; also Betti, 1. ¢.
Vol. 3, p. 74, 1852. For the connection with linear substitutions see Part II, Section III.
94 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
58. Since every mark except Y = 0 of the G/'[ p”"] satisfies the equa-
tion
Xr eee (2)
it follows from § 57 that y(X) will represent a substitution on p”” letters if
and only if the resultant of (2) and (1) is different from zero. This resultant
is
A 1 ? A 2 ’ ae A m
¥
AD See oA
UP os A ae ee eee (3)
nim—)) nim—I1) n(m—1)
a in ’ A ‘ ’ ae) A ain —1)
The proof is analogous to Sylvester’s dialytic method. I set up m equa-
tions linear and homogeneous in the m quantities
>) n(m—i) °
ae —1, (Zens A tae?)
such that the system of 7 equations is equivalent to the system (1) and (2).
Thus, raising 7 (X ) to the p™ power,
si A ~ DC kant! = 0 .
i=l
Applying (2) multiplied by X to the first / terms,
Ft ica pa > yrk—i) \" pak Yrpnntk—i)
_ A i a + ad A 2 oA — 0 .
ii] : i=kh+1 4
Introducing in each a new summation index,
at
m—k E
\' pk i 7 ym—J) v prk } x pnim—))
J ~ Pek ste om Xx +- a OL jtk va —— 0 ’
j=m—k+1 j=1
Combining and replacing the index 7 by 7,
v k 7 mWn—1)
= Oe Rails Gey Ged Ue (4)
=
where, if 7 + 4 > m, we are to understand
, A isp — Agia, :
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 95
Dividing out. X from (4) we obtain for & = 0,1, 2,..., m — 1a system
of m equations equivalent to the system (1) and (2), since from the former we
can pass back to the latter.
59. Owing to the objection that may be made against the usual proof of
Sylvester’s dialytic method of elimination, the following proof that (3) is the
resultant of (1) and (2) is given.
Lemma.* The necessary and sufficient condition that m marks 2, %,...,
2, of the GF[p””"] shall be linearly independent with respect to the
GF'| p"| is that the determinant
O O (
oF es ae ees,
QQ pn QQ p” Qp
AoE peed, ad eegige rae ee
QO p» QO p> Op —!| Qpr | 7 5
Coy > Ih | ) Ct Gs of ts ea | ee bly \9 () —— 0, hi LE) Le —— 1) (5)
O pran—1) O prm—1) O prm—1)
— 0 9 -_— 1 eT el BAe _— m—tl
shall + 0.
It is sufficient; for if 2, 2, ..., 2,_, be linearly dependent in the
GF’ [ p"),i. e. if a relation :
peepee (6)
holds where 7, 7, ---; 7m—1 are marks of the GF'[ p"] not all zero, then will
the determinant (5) vanish.
It is necessary ; for if (5) be zero, write
m—1
= 9 > j ee
Repairs Syd eR! Cea OF ee i)
iO
where /? is a primitive root of the G/’[ p””"] and the y,;s are marks of the
ie
Gio [pela Len
Co enon. ble is (ig == 0, 1. me — 1)
*A more general theorem is given by E. H. Moore, A two-fold generalization of Fermat's
theorem, Bulletin of the American Mathematical Society, second series, Vol. 2, April, 1896.
96 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
where, writing in full the determinant in /?, we have*
ager ul Re fer
Sie ; fr : ¥ pe
PR? Re pwn) = || CPs — Wrap)
b] | oe eee ‘
Sot aU, le ee eS
eS t
es face aks ne Roeper)
which ¢ 0, # being a primitive root in the G/’'[ p™”"]. Hence | »,,| = 0, so
that a linear relation (6) exists, in which not every 7; is zero, or 2,
2,,, are linearly dependent in the GF'[ p"].
The condition on A,, Az, i254, that
ta Ip pe)
a ee A" > ymin—i)
aN Mies i A,A (8)
shall represent a substitution on p”” letters is the same as the condition under
which 7 Ay,..., 4,’ shall be linearly independent with respect to the
Gi[p")|, when it is given that 4), X,,..., X,, are similarly independent.
By our lemma, the latter condition is
| AG S25 (597 == 0, 18 oe 5 Me 1)
Applying (8) this determinant becomes
>) nim— 1) > n(m—?2) r > ,n(m—1) r
Aix? ys A,X? +- eee + ASA eae JA iA? -+- aie at + BAe
ny n pprum—i n Vpn an a ?
AY Xx, ee A PN OS ee SA A es ee ee eee
Db m7
Ae Yom = a omy, 1 etd YPN Aap Nae eee
m m ML
which equals the product of determinant (3) of § 58 by
yar %
7 »ynm—)) Me prm—l)
er 2 > ee ey m
1 3
”
“pr ym—2)
Ad
Aue _9
yee 2) y pas 2)
41) ’ “12 ’ PL m
CEE TP GIT PG ats ee
* Baltzer, Determinanten, p. 85.
DICKSON. ANALYTIC REPRESENTATION
U7
But by (5) this ¢ 0, Ay, ..., 4, being supposed linearly independent in the
Cel pg" |:
OF SUBSTITUTIONS.
General theorems on SQ [ p”; p"], $$ 60-68.
60. In studying the quantic belonging to the G/’[ p”],
jie aa Epr—k iL (e
= = Oy? re Bigs? =F og ee = i DyyAS 5)
in which «, + 0, and & < p” — 1 it is found desirable to compute the power
ite = hire +. re = Any. =I Di) =| hs
where ¢ is the least positive residue of x modulo 7 and 4 < p’*’.
Let the general term of the expansion be
(EP"\%o . (4,6? *)% : (ayer en ;
Cpe) leat
where we thus have
© PO Ga +. + Oy y= pp’ + kp s+... th,
(1)
9= pa, + (p'— hk) a + (p" — & — 1) Gey +... + Ayr = p"
- —1. (2)
I shall use the abbreviations
& = pay + (p" — &) ty + Ops + Apyg +--+ Opa
S5= pty + (p" — Bae + (PP — 1) (ten + deg + + ys)
61. By equation (2)
dy = ( p” es 1)/p" = poe ;
Hence by an application of § 14 to (1),
Be gD ily sea ee el dae eee ea Np
Suppose at first
Ny = k : yale = if ; ee ! :
where
tee) town ott
ire ee ts ee Ee oh hy.
Then by (1)
Gy = Opa pe se A Ope = pO
If a, = p”" + y, where 0 < y < 2, we readily find
8, =p” + kp + kp +... + Ap’ —(p"— let (p’—k—ly
Sp t+ kph? +...+ hp" —pe>p —1.
Hence s 5
> 8 > p” — 1, contrary to (2).
98 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
lf a, = y, then
8 = (p—YDp rth. pr t+kp’4+...+hp—(k+1)e+y.
Hence s < s, << p" — 1.
Applying § 14, we conclude that a < Ap" *’ and thus
a =< (kK—1)p*" + kp? * +... +k. prt +h.
62. We may prove by induction the theorem
a Z(k—V (wee ee
Thus, to make the general step, suppose
by =k 1) Ce ae ee |
so ea ay Onegai acim y Meth BI) <2
where
0 2S a! = ke ( Cae. + yp cs 2 a eae — pido ae A ‘
Then ;
Ly, + nay + ieee a Gard — oad a8 Daan + “aie —- y Lee § a. a ‘
Ife, =p? tp 4p” sy, 0 a ee then
By OP cee pe a DO a MT ee
Hence s Ss, > p"— 1.
If a, —. (is | yma ms et a Daan | Ys
oe = 7 al + ki Cp ees + Pe ee + yaaa + hp” ee (hk + 1) a’ ae y ‘
Hence s = s, < p”® — 1.
If a, have a value less than that last supposed, much more will s be <
p" —1. Hence
a, <(k al} (gr Eg pe ) Eee
Hence finally,
ay (k—1) (po 4 2 pe he eee eee
63. Let g denote a positive integer and write
dy (bh L) O™ y aiit) ea (3)
Here g is not a multiple of p, since then would also @, + a4; +... + G1
and by § 14 s would likewise be a multiple of p.
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 99
From (1), (2) and (3) we readily find
Op Oya oe or ApS Pe pn eet pag (4)
(p —kh)a, + (p" —k Vga t+... + a4 =p" —1 — pra,
ee eee aa Pt ee (ep + gh) 1 « * (5)
Multiplying (4) by p” — & and subtracting (5),
Ops + 2dgre + BQy43 +... (p" —k— 1)a,_, =p" (A — kp) — kg +1. (6)
Thus
g 1 when the equality sign holds.
For by (8),
Ay, Say # pani “f- youre’ a ay und:
and hence by (4),
ay ey a8 gosta? ae x See ae go - i} :
Then
3; = pe oad 1) Cpe + | et + ts a atl ot hp” — kh =e ee Co Ss k — 1) ;
Hence
8 = fe
1.
* H(«) denotes the greatest integer in @.
100 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
65. Theorem. Jf ¢ = 0,i.e. n be a multiple of r, the coefficient a, =
For p" = 2, € + 4 is suitable on 2” letters (by § 57) if and only if it
vanishes only when ¢ = 0i.e. if a4, = 0.
For p’ > 2, consider the power
aD ae =e pi a me ae p ae ik ;
Making 4 = £ = 1, ¢t = 0, we have g = 1 and hence
@= 0) aS Pp" 7 |] ea DO Le Og
The condition is thus
Par see fp ti ==) }
66. Theorem. Jf the quantic belonging to the GF [ p"\, p > 2,
7 . — “ " = . © . is
opr || £( pr—1)/2 &( pr—3)/2 je
g ft Dayr4 $ -+ Qe pr+3)Q -- Shane -j- Oyr3S
be suitable on p” letters, then Gran = 9.
Consider the power
; ret ne a .
jie + 1Y eh Gy cease + Vb ea ar | Dae DP) f 1 ,
Thus
ko(p st D2, p=2 eS pogo
Hence by (6) and (4)
Qisy = Oyyy Se Ope ee Og a ee
The condition is thus a,“ = 0.
67. Less frequently will be studied the power
g ube Al kh es au aan =} Ly: — pe a h :
where g and £ are < p" andi < p"*’.
Similarly as in $$ 61 and 62 we may prove that
Og <9 TO Oe at ia
Taking s = ¢ (p” — 1), we find as in § 63,
p= (g TD) BOL) ea hat ae) ty ee
Oks, + 2p, + 8Gny3 +... + (p" —k—1)a,_, =p" (h— kp’) —ko + 9,
where g > 0, g + 0 (mod p).
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 101
The parts of the condition given by
s=n(p"—l), n 1. The remaining value g = » gives in equation (6) of § 63,
AG ees es ced OL? gee LY
Then by (4)
a = 2? 4+ Qr4*4...4+3 42.
The condition is thus
o9n—2 93
Oe +5242 42 gn a),
Hence would 4, = 0. But ¢ + a,é vanishes for =a,. Hence a, ¢ 0 leads
to no substitution quantic.
102 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
Our quantic thus becomes
>: “f- nS = CRS
which is suitable on 2” letters if and only if a determinant of the form (3) in
§ 58 is + 0.
dene at oe
Cases depending on which is the first coefficient + 0.
(ayan:
Suitable on 5” letters by § 18.
(b) & + af, a, + 0.
Suitable by corollary to § 57 if — a, is a not fourth power in the GF'[5"}.
(c) & + a€* + a,§, a, + 0.
Rejected by § 66.
(d) & 4+ 46° + af, a, ¢ 0.
The coefficient of ¢? has been removed by a linear transformation. The
lowest power giving a condition is
fet 2 bt 2 een
Thus g = 2or8=# | 5-), since g > 1 by § 64.
J
For 9, = 2,0, 1p0,.= 5°70" = eer
for. g== 3,00 eas
The condition is thus (using § 15)
Qn-2 31 ae +e F541 pee» Qn—2 ge te F548 3%)
or
-
4, > 40,7 -
The quintic is thus ¢ (€’ — 2a,)*, which is indeed suitable on the 5” marks of
the G/’[5"], if 2a, be a not-square in the field. For if, when 7 ¢ g,
7 (7 — 2a,)’ = ¢ (¢? — 2a,)"
on dividing out 7 — 9g,
(7—¢) + a(7 + 4¢ + @) + 4a2 = 0.
Substituting
ZA Sf, CSL — Bs
(w — 2a,)? = 24,7? .
(e) The case a, + 0 is rejected by § 65.
yb Py se
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 103
(a) € is suitable on 7” letters.
(b) 67 + a,€.
Suitable if — a, is a not-sixth power in the G/’[7"].
(oye ae a £0.
Consider the power
My -- ae — 2, : 71 + A(T*? + 7n—3 ap set 28 7) = 5 ;
If 7a, + 2a, = 2(7" — 1), then we find
Fo aa ey (aoe Ry fare 0 a
contrary to the method of partition required by § 14.
If 7a, + 2a, = 7” — 1, we find
ee ONT ee TOs a ee OOP OTP 87 4 8.
Hence a, = 0.
or
or
(d) & + 4,8 + 4,8 + a,€.
Rejected by § 66.
(e) & +. 4,€* + 4,67 + af, a, + 0.
For the power 7" + 3 (777? + 77% 4+ ...4+ 7) + 4,9 = 2 giving
“n—l by
ae aCe ha 2 a; = 0, or a; = 0 A
For the power 7"? + 3(7"? + ...+ 7) + 5,g =3, 4, or 5, giving
ee er (mA ae TES (fae ae AE
(31)"2. 5! Ae ae oie 6 Oe Coes ? = 0,
? Qn on—2 3) ae Qn-2 5 5! )
(lie oo ace (4, —- 2a") = 0 ;
The only possible form is thus
& (&° — 3a,)’.
() 4 af 4 of + af + af, #0.
The power 777! + 2.7%? + 2.7"% + ...+ 2.7 + 3 requires
9 - —1 719 -n—I = ‘ ~n—1 -
2r 3tf{4 eee arta lai pe mee af Ser eee tls Meaney == ()
Oga, + a2 + 2a,0, = 0. (1)
The power 7°71? 4 2.7"? 4+ 2.7" % + ...4 2.7 + 4 requires
‘ 7ni—l - ¢ ¢ ¢ * 5
Qn Alat t- Masta? + aa,+4 aa? +440} = 0.
,
104 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
(Disgaea re [s : fo : ; so that by the partition requirements we have
J
L
from (4) § 63 that g = / or 4.)
Applying (1), either a, = 0 or else
O20; = — Ont, (802 + 5a, (2)
vo
and thus — a,4, would be a square in the G/'[7"].
Consider the power 2.7" + 2.7"*% + ...42.7+4 2.
For s = 2(7" — 1), we apply $67 for ¢ = 4 =k 2 oe ence
9g 1, 4, Sa, 6, =", 0) Soa ee eee
> - fe . wN—1 ‘
The coefficient of 2 (7 — 1) is this 2%," >
For s = 7" — 1, we have
4t+ata+a+a=2(M1+...4+7+41)
Ta + 5a, + 3a,+ 2a, +4a,=6(714+...4+741))=7"—-1.
Hence
4a, + 2a, — a, — 2a,= 0.
Using the notation
iat SES hae oN tl (S="0, 2, 45: 6)
we know by § 14 that each ¢” is 0, 1, or 2 such that
10 (2) 4 5 ee. reehe
Cp” se 6 bee el oh Cia (gree Oe ett |)
We have immediately
46 + 26° — 6, — 2¢,° = Tm
m being an integer. But m must be zero. By induction,
46 + 22 — of == Deh == 0 2 tg OF ae)
Then c® = 0 or2. Butifc® = 2,c = ¢® = ¢® = 0 and the last equa-
tion is not satisfied. Finally, ¢ = 0.. Hence @, = a4, =—0 and a, = q,.
Then
2a, + & = 2784 4-7. ot
from which it follows that a, takes exactly the 2” values
nm = 5 ;
Be C. f ”) . 7)
jJ=0
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 105
where c;? = 0 or 1. We thus obtain 2” terms,
(48°) (63) (a8)
or
(Ay)? ( oe) gs a ree ora
Hence, as far as their literal parts, these 2” terms are identical with those
’ b]
given by the expansion
(24,0, + geet ge att é
In order that the numerical coefficients be congruent modulo 7, we must
have by § 15,
Dt on Sy, (4) |
Sate (6!)
/ j=0 >
But if Z of the ¢,°’s are = 1, / of the c¢;*”s are zero and hence n —// ure = 2,
Hence
R=) :
Le AN SS 28
5D
n—1 Fe {2) n—1 2)
Dee OU ae TT (Dynes OF
j=0 x
vi
The identification is thus complete.
The complete condition given by the above power is thus
Raine oS + (24% + Ciiene = Ue
Applying (1) and remembering that «@, + 0,
= (— may oo" EE ee (3)
ence
(= Pie Ete (25\" i eet i
so that — a,a, is a not-square in the G/’[7"]. Hence by (2) a, = 0.
The power 777! + 2.7"? + 2.77% 4 ...4+ 2.7-+ 5 requires
m1 n—2 2 7 ; .
ae i al {24° + 4a,0,’4, + Ga;'a, + a,°a,' + 4a,'a,0,' + a,'a,'a,
+ 6a,°a7a,’ + 20,4,’ + 2a,'0, + @,"a,’ + 3a,'°a, + 4a,°} = 0,
the last four.terms not occurring when 7 = 2.
Applying (1) to eliminate «,,
4a3 + 40,70,’ + ata + 2a,°a) + 2a,8a,! + 50°F + 2a,4a, + 4a,°=—0, (4)
the last two terms not occurring when n = 2.
106 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
For n = 2, we may give (4) the form
4a; Clore 2a,”) (a, — 40,”) (a, — 5a”) [4,— (1p 3) ay"| [a, — te 3) dy f= Oy
But by (3) .
(0,0, ) == 2a
Hence «a, is a not-square in the G/’[7’] and
aS 2a? .
Thus (+ 2)? = 4; 44 = 2; (1 + /3)* = 5, each modulo 7.
For n > 2, (4) may be written
4 (a, + 2a,”) (a — 2ufa,? + 3a,a,* + 2a,°)=0,
the last factor being irreducible in the G/'[7'].
By using § 68, I find that the power
(et 200? fo 2a PB ST
(4’)
gives for zn > 2 a condition of six terms which on applying (1) to eliminate a,
reduces to an identity. But the power 7"? +4 2.7"?4...4+2.7+3.7+4
requires for n > 2
-n—1 2 - 7 2 - 7 ooo x
a +...47 {4a,a,°a,' =e 2a,/a, | 40,270,085 a 645) 06a, eis 5a,‘a,'a,! - 34,4,
+ 24," + a.a,/a"2 + 2a,'a,a,4 + a,/a,'° + 20,"a,'a, + 24,94,
+ 64,"*a,’ + 3a,"4a,%a,5 + 6a,."a,"} =0.
Applying (1) to eliminate a, (the 4th, 6th and 14th terms cancel),
a, {6a,° + aa, + 3a,"4a2 + 4a,'%a,' + 3a,%a, + 42,%) = 0,
4 a, (a4, + 64,”) (a, + 2a,”)* = 0.
Hence by (4’) the only possible values, when 2 > 2, are
iy i
The same holds also for n = 2, since the set of values
bi = i DGS 0 =
is excluded by the condition, given by the 18th power,
Ut, + Ba, a0,' + 5a,)a,' + 34,5474, + Lala’ + 4a) + 3a,4,'4,°
+ 5a,a,' -+ 3a,%a8a,! + a,'aya.° + 2a,'a,'0,' + 4a,%a,2 = 0,
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 107
which reduces to 6a," = 0 by substituting the latter set of values, is an
identity for
t= 20, a4,=— aS:
The only possible form is thus ¢ (€’ — 2a,)*, which may be proved suitable on
7” letters, if 24, be a not-square, by the method used in § 39 or as below.
NAcep cen Lh.
(a) Et A aye S.
Suitable if — a, be a not-tenth power in the G/’[11"].
(b) " + af, a +0.
The power 3 .11"* 4+ 7(11"? + ...+ 11) + 9 requires a, = 0.
(c) &" + a,§* + a, a, t 0.
For the power 2. 11" + 6(11"? + ... + 11) + 8, we must have
s = 11" — 1 and then a, = 6(11"7 4+ ...+11)+ 8. We may prove by
induction that
ape Ali 11? + 11) 8.
Thus suppose
a =4(11"? + 117% 4+...4 11"") + 6(11" *'+...+11) +8 —a,
Oe ee FICS Olt * 4 a 11) 4 8.
Then
Cait ee ree 2 Lt tot aD LL te,
lide elie. ed. 1" fy. where 0 = y = @,
ere Le OL all) 8 Ll 10e Dy S110.
Tide et Le oe BLL eH Le ty,
Pe Let ere et) 6 Ie + 112)
+ 8.11 —10e + 24y< 11"—1.
Hence
ieee ere LL ee Ol Lt
and thus
pee ee te LIP ee OI et 1d) + 8.
It is now easily shown that
Gee eee Li 1) a 2 119 + ... 4 T1 8, a, = 1,
as a smaller value for a, would require s < 11" — 1. The condition is thus
Hiliah «2 Syne en = (Pe
fe ty = 0 or a = 0.
108 DICKSON.
ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
The power 2.11" + 6(11"? +... + 11) + 10 then requires that a, = 0.
(a) & $ an8! + a? + a8, @ #0.
The powers 11" + 7(11"? + ...+ 11) 4+ 9, 1177? +7(11"? +...+11)
+ 10, and 2.11"'+ 4(11"7 + ...+ 11) + 8, require in turn,
a—=0, a =9,
(e) €" + a€° + ...is rejected by § 66.
(f) €" + 4€ + af + a6 + a€ + af, a, + 0.
The power 11"7 + 5(11"7 +... + 11) + 6 requires a, = 0.
The powers 117 + 5(11"7 + ...+11) + Tand 11"1'+4 5(11"° 4+...
+ 11’) + 6.11 + 4 require respectively
tee is
=i
Gee ee (4y° + 2a.) + 5a;"a,) = 0
n—1 ©
ip) FIG. (g” + 2ag%) + 4a,'a,) = 0.
Hence a, = 0 and then a, = 0.
The power 11." + 5(11"° +... +11) + 9 of &" 4+ a6 + a,§ requires
n—1
qj 1+... 4141 (q,, — 3a,2)t = 0.
The only possible form is thus ¢ (© — 5a,).
(g) The cases a, + 0, u, + 0, a, #0 I have not attempted.
75. Theorem.*
a, =, 0 by.8-60.
Lf d be any divisor of p" — 1, the quantic
& (E4 — y)(Pr—lyd |
where vis a not dth power in the GF [| p"), represents a substitution on its p”
marks.
We are to show that
&(é4 _ y)\(pr-Did — 8 (1)
has a solution ¢ belonging to the G/’[ p"], § being an arbitrary mark of that
field. The statement being evident when / = 0, we will suppose that f/ + 0.
Writing ¢ = ¢* — » our quantic becomes
gpd : (¢ aH y)ua = (g?” -b yor) ;
It is then sufficient to prove that
g + vy? = ft = 6
* From the results of §§ 70, 72, 73, and 74, for ‘Di = 3, Osa and Nal respectively, I venture the
ple type
(2)
conjecture that all substitution quantics of degree p suitable on p” letters are reducible to the sim-
E (€4 — y)(p—-0e
where d is a divisor of p — 1.
DICKSON, ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 109
has a solution ¢ belonging to the G/’[ p"], ¢ being any dth power and » any
not dth power of the field. For if there be such a solution ¢ (which + 0, since
3 + 0), then
é — (¢ + y)ua = B/gP ne
will belong to the G/’[ p”| and satisfy (1).
Writing in (2)
¢ — 1/o
and multiplying by w”’, we obtain
Lee sur Dw”.
If we make
r
OO Lee baat ar
0 being thus a dth power and Y a not dth power in the field, the last equation
becomes
Go = Oa
But this always has a solution in the field ; for by § 57, corollary, the quantic
wo? — Yo
represents a substitution on p” letters, »’ being a not ¢th power and hence a
not (p” — 1)st power, d being a divisor of p” — 1.
For 7 = n, this theorem is a special case of the following theorem :*
16. Tf ris prime to and < p” —1,tfsisa divisor of p" — 1, and if
Ff (&) is a rational integral function of = belonging to the GF '| p"| which can
never vanish, then the quantic
er fe)
represents a substitution on p” letters.
For if the quantic be raised to the /th power, / being not divisible by s,
we have a set of terms whose exponents are of the form ms + dr and thus are
not divisible by s and hence not by p" — 1. But if
bes isi p= 1")
we get the term =”, since by the hypothesis on 7 (¢*) we have
Lee) = 1.
But /7 is not divisible by p" — 1.
* Proved for 2 — 1 by Rogers, |]. ¢. p. 41. I give a modified proof.
110 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
77. The substitution quantics given by § 76 and, when x < 7, by § 75 are
not reduced.
Thus, for p > 2, we have the suitable quantic
yp
mE pip ta : = 5
er(& 2 — yp)? = — Df EF —1/2(v+1/)
v being a not (p" — 1)/2 power in the G/’[p"] and thus any mark except
+1,—1,0. For the p” — 3 values of v, we get for each value of 7, (p" — 3)/2
different substitution quantics on p” letters. For if
ytlf=v4+1/V
then either »y = Y ory =1/. Alsovt1/v.
Examples of the above quantic :
== 1,” Dp Ses0 ean i
&¢+ 3¢ and €, + 2c, Hermite’s forms.
at eg a
Poms Lp aL ee NG ne Aeecsseao
nes 2D =o oe ee ae cuLsere seas
For the values » = 1, p = 7, we have if » = — l,
é (62 — yp)? = — By ( — v6 +4 82%)
& (E? — yp) = 2 {EE Ove 4B ue]
which together give the known quantic on 7 letters,
G4 gE 4 By, a = arbitrary.
Srorion LV.— Degree a multiple, but not a power, of p.
78. Attempting no general investigation, I will confine myself to the deter-
mination of all sertics suitable on 8” letters, together with a few special results
on sextics suitable on 2” letters.
g(§)=—& + af + a f* + a6 + af + a,€ on 8” letters, §§ 79-82
79. Applying a linear transformation (in the G/’[3"]),
g(F + y) =F + a8 + (a, + 2a) &* + (a, + an + ay? + 27?)
“(ag sk &7P) FS = (Gg a 2a 4 ag? aa) ae
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 11]
Hence if a, ¢ 0, either the coefficient of €* or that of €* can be removed by
choice of 7. But if 4, = 0, no other coefficient can be removed in general by
a linear transformation.
80. The case a, = 0.
w+
The second, fourth and fifth powers require respectively,
Ss a (1)
1l+ai+aéi=0 (2)
O° + 2a,a, + 4,5 + 2a3a, + 2aa,0, + a,°a, -+ 2a,a,4 + Zana; + 20,0;
+ 2a,aa; + aga" = 0. (3)
The seventh power requires exactly the cube of (3).
From (1) and (2), a, is a square ¢ 0 in the G/'[3?].
From (1) and (8),
(43 + 2ay%Gs0; + O°") + 2 (Gs + GHz) (4° + Gy4;") = O.
Multiplying by «,* and applying «,' = 1,
(a, + G0)? {a, + 2(a, + a,a,)?} = 0.
Hence either
Gx ht OL 0 Oa ee
The case 4, = 2a,4, is excluded below. The quantic
oo a ae a6 -- a6" + (2a,a, a 2,5") € (4)
becomes by writing ¢ = + a,'"7, a, = + a,Pa,
ie {7 ae 7 =a a7) ae 7 = (2a a 1) y) \ ;
The resultant of the equations
y+t7+ (Qa+1)y7=—0;7=1
is
oo t+ tol (e+ 1) (¢ —a— 1).
Hence « may have any value in the G/'[8"] except 2 and 2 + 2?”
112 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
The ultimately reduced form of (4)
es bape ate ees hg 1é
represents the following substitutions on the marks of the G/’[3"] :
(0) (1) (— 1) (212, 21 — 1, 918 +1) (— 918, _ 912 _1 _ 918 4 1) fora = 0.
(0) (1) (= 1). (2, = 218 1) ol 1) ok oi ee) fore
(0) (1) (— 1) (— 91) (_ 942 4.1) (— 912 1) (22, 22 4.1, 212 — 1) for a = 21,
(0) (1) ‘eo 1) (Q42, ne ils 42 1, 91/2 il. 91/2°__ 1 2/2) fora =—1 + 217,
(b) n > 2. Write 3" = 6m + 3, m being thus of the form 9% + 4.
The powers m + 1, m + 3, and m + 4 require respectively
GO, =a, (1)
a, (20° + a,°) = 0
Os! + Ogt0;° + aga? + afah + 2a,°0, + a°a.” + 24,47 + a,'a,°a,
+ a%d,'04-+ a,7d,° + 2a,%0, + 4''=0, (2)
the last two terms not occurring when 2 = 3.
Applying (1) to (2), we have whether 2 = 3,
Oy (Us! fF OglhgIs? + Oy°s'Us + Oy'Oy!) = Uy (U5 + Og)’ = 0.
Consider the power 3"! + 387 +...43+1 7 aq+a+4,+ 4+ 4.
For s — 6a, + 4a, + 3a, + 2a, + a, = 3 (8" — 1), we have
Gy Se BA Se 8 Se ae a a a re ee
For 6a, + 4a, + 3a, + 2a, + a, = 2 (8" — 1) = 3" 4+ 2.3"1 + 2,3"
+... + 2.3 + 1, it follows that a, = 0. For, in the notation of § 73 (f), if
of = 1, then of = 1, .. cf; == 1; while ah ote ewouldmives = 20.071),
Also a,.— 0; fornt cP? then 2 a
Thus 2a, = a, == 0, DIO, == 0, ee OF a ee
For s = 3" — 1, we have at once
Q, == 88) + BP ee BEAL, $a p= ee
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 113
The condition is thus
n—1 - an—1
jee i Fak OtT 4 ap” fins A OtE . ()
Hence by (1), 4 is a square ¢ 0 in the G/’[3"].
The only possible form is thus
& + gf + 46 + a2 + 2a, ,
which is nof suitable on 3” letters since it vanishes for ¢ = a,!? + 0.
81. The case v4, + 0. Removing the term a‘, we consider
Sta?+a484 46+ 4€.
(a) n = 2. The second, fourth and fifth powers require respectively,
Gp 20 Ore (1)
1+ a%a, + ae, + a46=0. (2)
a, + 2a, -+- 2a,%a, + 2a,?4, + 4,707 + 2a,4,%0, + 2a,aa,' + af307—=0. (3)
The seventh power requires the cube of (3).
First, a2 = 1. For if a4, = 0, then a, = 0 by (1) and then «a, = 0 by (8),
which is contrary to (2).
By squaring (2),
ads’ + Qafas + a%a° = af + 2a, + 1 = 2(a, + 1)
= 0,0, 1-20," ; (2 )
But a, +0; for if a, = 0, then by (3)
0° (03° 4- 2a,°0, + 2a,°a,* +- a,’a,') = 4, (a, — 4,°) (43° + 4°) = 0.
If either a, = a,° or a, = 2'a,°, then by (1) a,* = 1, contrary to (2)
for a.== (0!
Hence by (2’)
ieee Naas a a? ae Da® te Oa? 2.0),
Writing a, = ya,’ this becomes, aside from the factor @,’,
@+)@+)@—7-1) =0.
114 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
If 7 = — 1, a,4 = 1 by (2), while (3) becomes
a, + 2af%a, + 2a,°a,° + aa,* = a,’ (a, — a°)' = 0.
The resulting quantic
£6 ae a2 che ape wy ose PA ape
is suitable on 3° letters. Thus for a, = 1, it represents the following substi-
tion on the marks of the G/’[3?] :
(0) (1) (— 1) (277, — 2%?) (24? + 1, — 24 — 1, — 23? + 1, 23" 1).
If 7? = — 1, a, = 21a’, while (2) and (3) become
i — a
(1 — 21) g,? — 2¥¢° + 2a3a, — 234,34, + a,?a,4 = 0.
Multiplying by a,’, and placing a,'a,' = a, = — 1, « = ¢a,’,
‘tae Q12g8 a (1 ran 21/2) ¢? 29 al + 21/2) = 0 ’
whose roots are
Lie Ota eT ero ee 1 oe
But & + «4& + gas — gas? + 2%a,°€ vanishes for € = — 2'*a, when g =
— 1 — 2%", while for g = 1 — 2!” or gy = — 1 + 2%? it represents a substi-
tution on the marks of the G/’[3?]. Thus, taking ¢, = 1,
e446 1 (4 21/2) a abe Qu2) G2 4 gre
&6 as & (4 1 a 21) ra a (— il an 23) = ao yl aa
represent respectively the substitutions
(0) (— 1, 284 1) (1, 2 1, OR on oe ee
(0) (— 1) (1, 2%? — 1, 23”) (21? + 1, — 218, — 232 4 1, — 232— 1).
If 7? =7-+ 1, a, = (2'2 — 1) a’, and (2) and (3) become
ees
— 21g? + (1 — 2%*)a,° + 24a, + 2'a,°a,> + aa, = 0.
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 115
Multiplying by a,’ and placing a,‘a,4 = a, = 1, 4, = ga;
21g Le D122 roles (212 a 1) aed)
Its roots are — 1, 1 + (— 21? — 1)!”, of which the last two are not marks of
the G/F’ [37] since (— 21? — 1) = — 1.
The quantic given by ¢ = — 1,
6 as ae Pe (gas = ae oh (212 ~s 1) ae
represents when 4, = 1 the substitution on the marks of the G/’[3"] :
(0) (222) (21? — 1)( — 2'? + 1)(1, 24 4 1, — 1, — 2!", — 212 _ 1).
dee eae
The fifth, seventh, eighth and thirteenth powers require respectively,
& + aoa, +a*=0. (1)
a,0° + af + aa? + a70,%0, = 0. (2)
Osby | 2apas + 0°05? 4- 4,0,°0, 4- 20,°a, + o,'a,0,° + 2a,°a,'a,"
+ G70. + 24,0,’ = 0. (3)
I + afajfa, + aa + aafa,7 + a2 = 0. (4)
The tenth power gives an identity ; the eleventh requires exactly the 9th |
power of (2).
Applying (1) to (2)
a, (a> + 24,843 + a,"o,) = 0
or
pe 0, dy a 2a. (5)
(b,) If a, = 0, then a, = 0, a4, = — a,‘ and the sextic obtained, & + a,&°
— 4,'§ is suitable on the mark of the G/’[38*]. Thus &° + & — & represents
the substitution
OM (-Y)GP-L—F+7-L—-P+I4+LI-LP+4—7
—f-Ujt+he—j,—P-J-1L—P-J4+N(-h-F +3,
2 2 |
ee a ae Pa tL Pe 7 LL,
ume geririels J == 1).
where 7? = j + 1 is the irreducible equation defining the G/’ [3°].
116 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
(b,) If a, + 0, we have on applying (1) and (5) to (3),
a,°a, (24,5 + 2a,? + a,°a,? + a,'a,") = 0.
Writing «, = 72,°, this becomes
vi 7 i 1 — O :
Multiply by 7’, replace 7" by 7" +” and 7” by 1:
je te pects Awe
Extracting the ninth root,
ae ape Fa ee 2 fant eae apd 4 —
i ee Mel Meme Remcttergl pam UE oe 98 Oi iy hha
Now 7 = 1 is excluded since € + a,¢° + a,°¢° + a,'€? vanishes for § =
Again 7” + — I, since then 7* = — 1.
If7v=7 +7 +1, then 7? = — 7 + 7,7" = 1.
From (1) and (5)
Oy == 90, 0, = — (4 + Ta a, ey ee
Substituting these values in (4), using 7° = 1, we have
12
7 7°
FP a a ats ae
which is readily seen to be inconsistent with
Siecle hor ce he
(c) 2 > 3. Write 3” = 6m + 3.
The powers m + 1 and m + 2 require respectively,
a, + a0, + a = 0
aa° + af + afa? + afa,'a; + a,"a, 24,7’ 0-
From these
a (5° + 2a°a,° + a") = 0
or
O, = 0,74, + 2a,°.
But
oS G6 a5 Oar) f° + (4,"a, + 2a,°)¢
vanishes for € = — g, and is thus excluded.
— O,.
82. Summary of $$ 79-81. The only reduced SQ [6; 3”] are the last five
quantics in the table § 87.
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 117
Introductory study of sextics on 2” letters, $§ 83.
83. Ifig(@)=& +46 4+ «€f + 4,6 + a? + a6, then
¢g (¢ + 4) = Sa Cer e a9 + 4) Ss gs b ee sy + 44) oh
+ (ayy + 457? + 45) & + (7)
Hence in general no term can be removed. If a, = 0 we can make the coeffi-
cient of €' zero; if 4, = 0, we can make that of € zero.
84. The case n even. Then 2" — 6m + 4.
(a) n = 4. Of the “ power conditions,” two are independent,
err, 3
tly ac
aos + af + a, + ata, + asa? + a,° + afafa, + afaa,? + a%a." + afa,
+ 0370s! + G's) + O,°O,U, + asd; + aaa, + aao—0.
(b) n > 4.
The power 7 + 1 requires a, = «,°. Applying this to the condition given
by the power m + 5:
ads + OG, + afayas + aafa + 4,450; + 4,°o,'a,' + a°a'a, + 4,4,
+ a Mata, + afa$ + afafa?2 + 4” + a@afa2 + aa? + a'a8 + aja =0.
By the method of proof used in (f) § 73, we find the power
2m +1= 274 Or44 ...4+RP 41
requires
ee ee eae UOT Ot. 0%
85. The case n odd. Then 2” = 6m + 2.
(a) zn = 3. The third power requires
a, + a7 + a%a, + aa? + a,’a, + aa7 =0. (13)
The fifth power requires exactly the 4th power of this.
(b) » > 3. The power m + 2 requires
ads + sae + aa, + a,'u, + a°a, + aa, + a,'a70, + a 3a =0. (15)
The power m + 6 requires for rn > 5 and n = 5 respectively
(Og AO) (G, Ga” id,” ag) (43° Pa) (Qa, O02 4 a,fo,)—0. (2)
a, + a” + aa, + af (a, + a3) + a,° (a,0, + aaf + a,’a,)—0. (2;)
The powers m + 8 and m + 18 lead to (1).
(b,) Suppose a, = 0, so that by § 83 we can take a, = 0.
If a, + 0 and n > 5, then by (1) and (2) we find a, = a, = 0.
118 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
But & + a,€° vanishes for § = a,'%; while every mark in the G/’([2”"], n
odd, is a cube by § 18.
If a, + 0, and n = 5, (1) and (2,) give
7h tle . = 5, 4
Dai Tomes (0 Py lid 34 ren 0 a
Thusteither, a,’ Ss" a,%== Orca te Oe ee a
=6 £3 222 le} is S 1 as, ol, eee iS}
But & + a6 + a,”6 + a,"¢ vanishes for § = a,” = a,
If a, = 0, then the power 2m + 1 = 27 4+ 2744...42?4 241
requires 4, = 0. But & + a;€ vanishes for € = a;'", a mark of the G/'[2 ],
n odd.
Hence every suitable sextic on 2” letters, 2 odd and 738, in which the
coefficient of € is zero, is reducible to the form €°. ,
(b,) Suppose a, = 0,4,+0. Then we may take a, =—0. Then a, = 0
by (1). Bor 7 > bare 0 by (2h: for enone, elves
a, + 4°a" = 0,
hence either a, — 0 ora, = a;.
But & + a€ vanishes for 2 = «, and is excluded.
The sextic & + a,¢° + a, repr aa a substitution on the marks of the
Galt [2 viz tor aie ls
(URGORG TORN ce hm pncwy =o biyhiae UR ae Rypiccs) cath
oct bat ie sok vase om OLGA cr cee hal sai tea eh
PEPADE ED GT Ey Le eye a
PEP PIS LI ITA LRT Bee ee ee
FI LG oF es Fo) ee
the G/’[2°] being defined by the equation 7? = 7? + 1.
(b,) Suppose a, = a, +0. Then by (1)
On'=. a> + afd, 10,6,
(2) and (2;) and (1;) are seen to be satisfied ; but
OP OS a Ge GR (Gy a Oy ea
vanishes for § = 4.
86. Summary of §§ 83-85. If a sextic represent a substitution on the
marks of the G/’[2”"], then, for n even,
Us =O, ob 0s
for n odd and > 3,
at Oat A) at ae
except for the suitable quantics
e° on 2” -létters eS" oe” oe Ont a letbers:
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 119
87. Table.*
Except for sextics on 2” letters, the following is a complete list of all
reduced quantics o (€) of degree = 6 which are suitable to represent substitu-
tions on a power of a prime number of letters. From them (by § 16) all
suitable quantics whatsoever of degree = 6 are obtained by the formula
ap(§ + f)+7.
Reduced quantic. Suitable for p” =
E any
= 2”
c ; 3”, 3m + 2
— g& (a = not-square) : ; 3”
fi BE. : ; : 7
cA on
ot + Og” + TS . ; z 4 F
(when it vanishes oul fOr Go BE Gy
ge é : : ; 5", 5m + 2, 5m + 4
& —a§ (a= not 4th power) . , 5"
gF Bite ; 3?
Cceeedcoo, ; ; 7
eo teas? eS? aE 3a7E anes a Late Seranral f ; : 7
567 + 50? + oS (a = arbitrary). ; 5m + 2
& + a& + 30°F (a = not-square) . : : 13
oS UN LAE Ei a eiies = not-square) . ; 5?
eo : ; 4 . ; ; ; 2”, n odd.
Ves 2 ; : ; 11
G+ w+ ag? + 5E (a = square) 11
+ 40765 + af? + 45 (a = 0 or not-square) . “ Et
6° + a €* + ao? + a,7& + (2a a, + 0,5!) € : ; on
(a, = square +0; a, = 0, + 2¥%¢8?, + a3?) or + 2)? + 1) 2,37, the signs to
correspond to that of + a,°”).
& + a& — of (4 = arbitrary) : ; ; ; aha
Ge ae a oe eae (a =—arbitrary):. : 3°
4+ af + oa — pats? + 212a€ (4 = arbitrary) . 3”
(where g = + (1 — 2")).
f+ af — ofS? + aff + (212 — 1) a°F (a = arbitrary) 3°
In this table 21? occurs always as a symbol for ezther of the two marks of
the G/’ [37] satisfying the equation 2? — 2 = 0.
88. Theorem. Ad/ substitutions on T letters may be derived from the
two
C= ae 3b: we = 2.
[a | [a ) {2 An a ie 1
Le +5) Lat + BF) [Bota 4 208) = Lab — Bat + deat 4 Bbw)
ce Compare coe tcan Journal of Mathematics, vol. 18, p. 218, § 19.
120 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
so that we reach the form
e+ ae+a?+ 3a°x, aw = quadratic non-residue of 7.
pa ped ete vy )
La — b>} ba®J le He -- b8a:7 + 3d*z J | Bote | 3 J
te
i
= La? — bt at 3022 | a)
so that by writing 6 = c’ we reach the form
x — Can + 8cta.
[wc | [ w ae fee 2 | 3
Lae) Cae —b49% + i, Lave J La? + 2072? ++ 3 (20?)Pa J * ko]
Hence by (1) and (2) we reach the form
e + ae + 8e7x, a = arbitrary.
:
(x 1 fa Ta [ @ ) |; @)
| | w [x
La + 30°} La? +b) 1a? — be? + bo? + Sha) Lb’e. Ob? | =i + 46%x
ee)
so that we reach a* + 32.
[ # 7}
(21 fw er eee % 5
Aba is La® + Qe J? (5)
La?) Lat + 40%)
so that we reach a + 2z.
89. E. Betti proved (1. c. vol. 2, pp. 17-19, 1851) that all substitutions on
5 letters are derivable from
e = an + b> 7 = ws
90. Enumerative proof of Wilson’s theorem.
Of the p! literal substitutions on a prime number p of letters, p (p — 1)
have a linear representation
az+6, a0.
The remaining ones are represented by quantics of degree > 1 which fall into
sets of p’ (p — 1) each, viz,
ag(« + b)+e, a +0, 6 and ¢ arbitrary.
Hence p! — p( p —1)isa multiple of p’ 2 — 1), so that (p — 1)! + 1 is
divisible by p.
Enp oF Part I.
THE ANALYTIC REPRESENTATION OF SUBSTITUTIONS ON A
POWER OF A PRIME NUMBER OF LETTERS WITH A DIS-
CUSSION OF THE LINEAR GROUP.
[ CONTINUED. |
By Dr. Leonarp Evucrne Dickson, Chicago, Ill.
PART IJ.—LrygEar Grovprs.
Section L.—Linear Homogeneous Group.
1. We may define p”” letters
le. £., EIN, Em
characterized by m indices, each being an arbitrary mark of the Galois field
of order p"”. The general linear homogeneous substitution A on these letters
replaces /; .. t, DY 4z,,..., ems Where
v
joa Sg
o¢ =.
J
Ay; OR ee af) a
Il has
ANY
—
where the a,’s are marks of the G/’[ p"]. But (1) will indeed be a substitu-
tion on the p”” letters if and only if the determinant
|} A {=|a,;| 40. Cerveaen ly 2, ert 7e)
For there must be one and only one system of m indices ¢, which (1) replaces
by a given system &’; and hence an unique set of values ¢; satisfying the equa-
tions
ke
POT em ee (hee ee 970)
ga)
Remark. If the substitution (1) be identical with
m
ote sy (i ses, nv)
il
then must
Op Ops Cee WOR Pobre eri §)
This follows if we take in turn, for 7 = 1, 2,...m, the particular set of values
é=1;6=0. ES RO eee 8
122 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
2. Let & denote a second linear homogeneous substitution
= S iS i (7 se eae ner a) ad)
so that
|B) =} 8, £0-
The result of applying first the literal substitution
ey ien
Meee ey
and afterwards the literal substitution
A= (ls, | == (le, |
Pehla Wisk:
where by (1)
55 = & Aye,
is the same as applying the single substitution
bee
BA=| |,
&",
where
érr oe =
OS FS
V foot |
if
Tik = ~ OB - ”
=I]
We may think of this compounding of two substitutions analytically.
Laying aside the method of composition by matrices,* it will be found con-
venient here to think of the composition as follows. The result of applying
the analytic substitution A first and 6 afterwards is denoted by BA. A
replaces the index &; by
s Gish 4 »
j=
*Tn the matrix notation the substitution (1) is denoted by (a). The composition formula is
then
da ,
(4°) = (4 ij) (4%)
™m
where
vs te y ,
a nS = 4x y
je ja
provided the matrix (4,,) operates first.
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 123
which in turn B replaces by
eka et ee
< 4; [ = BaF | = 2 Vik? k »
j=) =i —
if
m
ss }.
lik = <= Bix
emt |
The compound /A is indeed a substitution since
| BA |=l\ral=lay!-| &el=lF St hea ea Vie
Moreover the 7,,'8 are marks of the G/’'[ p"}. ;
cae
The literal substitution product LA is thus the same as the analytic
Ppp!
substitution compound BA. The transformed of 7’ by S is always
CA! Foes iS pass
For literal substitutions, S~' operates first; while for analytic substitutions,
S operates first. The result is the same in both cases.
~It follows from the composition that the totality of linear homogeneous
substitutions (1) forms a group, which is called the linear homogeneous group
of degree p™. It is a generalization of Jordan’s linear homogeneous group*
of degree p” in which the m indices and m? coefficients are integral marks, i. e.
marks of the G/’[ p']. It is however contained in the Jordan group on mn
indices. It is identicalt with the group investigated by E. Betti in 1852-1855
and in more detail by E. Mathieu in 1861.
3. Necessarily the group I study is of degree a power of a prime. But
all that is of essential interest in Jordan’s general linear homogeneous group
of degree g” centers in the case when g is a prime. Thus by Jordan, l. ¢.
Arts. 127-131, the factors of composition of the linear group on m indices
modulo g are simply the factors of composition of the groups on m indices
taken respectively modulo p/* where
qT De,
t=1
Di Px» +++, Pr being the different prime factors of g. While by Arts. 132-134,
the factors of composition of the group modulo p/‘ are those of the group
modulo p; together with factors all equal to p;. Hence for the study of non-
cyclic simple linear groups the case of a composite modulus offers nothing
beyond that of a prime modulus.
* Jordan, T’raité des Substitutions, pp. 91-110, 1870.
+See Section III; also literature given in Preface.
124 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
4. Theorem.* The order 2(m, n, p) of the linear homogeneous group of
degree p"” on m indices is
Ouse Lae 1) Ges. PF. p”) Giese A oat » pr) 5 ir (ae ae. 2) 2
Let V be the number of linear substitutions
fi, = 1, Is fee CO) Ley,
which leave the index ¢, invariable, and let 7’ be a substitution which replaces
it by
eee
_ Dy 555 .
j=)
T TR, TR, ..., TRe,
The JY substitutions
will replace ¢, by this same linear function, and no other substitution has this
property ; for if (/ were such a one, 7’! UW would leave €, invariable and hence
be a certain /2,, so that
Ue Tie
The marks «,, may be taken arbitrary except that not all can be zero.
Hence the system a, is susceptible of p”" — 1 different sets of values. To
each set correspond JV substitutions. Hence
2im, 2,9) = (pw — 1).
But the substitutions 7, are of the form
™m
Sa Set le a (PeS2 ia. 5 72)
Yok
where the m — 1 coefficients a, are arbitrary and the coefticients a, a3, ...,
Aim are such that their determinant is ¢ 0, which can happen in 2 (m — 1, n, p)
ways. Hence
LV == PDO (ie ne) a
Thus
2(m, n, p) = pe (pm — 1) 2(m — 1, n, p)
— poo (ps ett 1) ; pe Ge: i 1) pick (p” — 1)
a Cee — 1) ie — p”) es Ga = oe) J
since evidently for a single index,
#2 (1, 2, p) =p" — 1.
* Stated Jordan, 1. c. Art. 169; proof for mn = 1, Art. 123.
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 125
5. Transformation of indices. Let A be the linear homogeneous substi-
tution on p”” letters :
™m
Fee (re Lean a ie) (1)
ied
We define m new quantities
Aono ie ms (eaaatl eA arate oa aT
k=1
where the £;,’s are marks of the G/’[ p”] such that
Beata Vr0 |
We may thus solve (2),
a?) 4" ik A =
Se ee By ates (Ihe ek a ed
where £,, denotes the adjoint of 8, in || =| P|.
Instead of distinguishing the letters 7; |. <,, from each other by the vari-
ation of the indices ¢,, we can distinguish then by the variation of the 7,’s con-
sidered as independent indices. Thus A will replace one of these new indices
4, by 22 By, a455;; So that, applying (3), we may write the substitution A
kj
qi Se tak (2 eee heey m) (4)
where
la B,,
ta Py Pin Beg + Z
ky j |B)
The coefficients £,, may be chosen to simplify the expression of the substitu-
tion A.
Remark. The transformation of indices (2) leaves the determinant | a, |
of the substitution A invariant.
For, applying (2) to (4),
a ies 2 Ya Pie SK (aa ear petie |
k=1 lk
Applying (1) and changing a summation index on the right,
»' Bin Og & = ~* ra By § - CS ee
kj l,j
Since this holds for arbitrary €/s, we have [see remark § 1]
= Pie Gy = ae By 5 (7 == Le 2, as m)
k=
ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
126 DICKSON.
Hence
Bi b= | pt 47 ball
or
| xs | == | Ta -
6. Denote by Bz, xs, the substitution
re i
mr ol = - = —_—
Sr — Spr =F AS 53 3 =
d
affecting only the index &,. Its determinant is 1 if 7 # s, butis 1 + Aifr=s.
Theorem. very linear homogencous substitution S can be placed under
the form* BL, where B is derived from the m(m — 1) ( p” —1) substitutions
Be. rte 5 (Fy os LD Rae)
1 being any mark +0 of the GF'[ p™], and where L is a substitution which
leaves unchanged every index except the last which it multiplies by the deter-
minant of S.
Let the given substitution S be
mm
cf = 4 0 F (2 = 1,2, , m)
i
Suppose
Dr¢ ¢ 0 5) O15 =0 2
If e > 1, the substitution
nm
‘7. 7
T= i Bg, Gijt;
j=e
will replace ¢, by
m™m = x" Ps
y’ a2 5° =
rig be eet a 4
8 Y=
If ¢ = 41; the substitution 7 >==
Bz, af, ° Bz,, se, Bz, yée ott Ds ee
will accomplish the same result if
1+ f=, ~+a(l + fy) = 4%,
which may be satisfied by any ; + 0, since a, + 0.
We thus have S = 7'S,, where S, is a new substitution which leaves ¢,
unchanged and thus has the form
"= 6; €/ = 3B, 6,. (tien 23 eae eee
5)
* The variation from Jordan, Art. 121, is due to the correction of 1. 17, p. 94, where S, 7’ should
read 7'S,.
ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 127
DICKSON.
To decompose S,, I build the substitution
if = II Be v8, viz.
Donna, 270)
|
fade fag 5 fag Ce ~ .
= 915 SH a HH (2
where the 7;,’s are chosen later.
Denoting by S, the substitution
Yo att at =e Ph
== Sis
(2: SS eer on 970)
dVyp
L
, m)
we will have S, = 7'S, provided
Pe Opie
m
c= By he = Ba :
I==2
oy 778))
But the 7's can be determined so as to satisfy these equations since
(2, yy = 2, oe
By | =| 8,) =| S| #0.
Hence
Pevdome AS RASS
Proceeding with S, as we did with S, etc.,
S = eds <6 Lees Tie Som—a ’
where S,,,,_, denotes the substitution
Sete Joel At We Lee, oe A lh Oe
7. Theorem. fa linear homogeneous substitution S is commutative with
all the m (m — 1) substitutions
ote wiensenes heb)
Bz, mel»
where pis a fixed mark ¢ 0 of the GE'| p"), then S simply multiplies all the
indices by the same mark.
Let the substitution S be
Ey (¢ =1,2,...,m)
Tt a
iS Susy
j=
We then find that S. B:, ,¢, and Lz, , . S are respectively
mm ,
j=
foal ’ °
si= 3 yé; 5 Le oe. ee ot 2-t Jc)
m
ee at ol
o, = ae + pay) §5 5
j=
™m
all 4 = \' »~
G4 SS MGS, = By; -
j=l
128 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
The conditions that the two expressions for &,’ shall be identical are, since
pt 0,
Gy = Gee Fy
=a C7 eae Ler Pe Ly
The conditions that the two expressions for €/ (i + £) shall be identical
are
Oem (ae LA eee eee)
Since the two sets of conditions are to hold for # and / = 1, 2,..., m,
k+l, S must be of the form
rie CRS SS re
where’@, == 0,)°== vas Cane
Factors of composition® of the generalized linear homogeneous group G of
degree p™, §§ 8-12.
8. Let p*»—_1l1—=p,.p,... py, where p,,...p, are equal or different
prime numbers. Let p be a primitive root of the equation
Ep" —1 —l1=0.
Denote by G,,, Gp», --. the sub-groups formed of those substitutions of
G whose determinant is a power of p”, p””,..., respectively ; finally, by
Gn = I that formed by the substitutions of G having determinant unity.
Let d be the greatest common divisor of mand p" —1; py, erat ie
the prime factors, equal or different, of d; p’ a primitive root of
Sti 02
Denote by //, //,,,, H,,,»,, ... the groups formed of those substitutions of
I which multiply all the indices by the same powert of p’, by the same power
of p?>,..., respectively.
9. Theorem. The factors of composition of G are
2 (m, n, p) raeitt: ;
Pir Por +++ Pres Ge Pris Pors++> Pi»
except when (m, n, p) = (2, 1, 2) or (2, I, 3).
*Some of the ideas used by Jordan in his decomposition of the linear group are to be found
in a different form in the earlier work of Betti, 1. c. vol. 3, pp 79-83, 1852, and vol. 6, p. 31, 1855.
The latter shows that his group of degree p” (see Section IIT) has as self-conjugate sub-group (of
index 2) the group Z of substitutions of determinant a square in the GF'[ p1]; that Z has as self-
conjugate sub-group of order p — 1 the group of those substitutions which multiply all the indices
by the same factor 2, a primitive root of p. He proves that in the case p” = 2° or 3? all the factors
of composition are prime [thus giving the exception in theorem § 9].
+ If a substitution of /’ multiplies all the m indices by the mark yp, then »”™ = 1, and hence
y* =1. Thus p is some power of p’.
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 129
Tt is clear from § 6 that the groups
Fa Gas Gia ee! aA fe iat Line lees COE: 1
have respectively the orders
DGnenen). Q(m,n, Pp) 2(m, n, P) eae ee 1p) See @ ad ahs,
Pr PiP2 pa) Pi PiPr
and that each is a self-conjugate sub-group of the preceding. Further, the
numbers p; and p,; being prime, there can be interpolated between G,, and
G,.». for example, no new group which contains @,,,, and is contained in
G,,- It remains therefore to prove that, aside from the two exceptional cases,
His a maximal self-conjugate sub-group of /. To prove this we show that
if a group J be self-conjugate under /' and yet more general than //, then J
will necessarily contain all the substitutions of /°
10. Let
oi B OS; CSA a)
jee
be a substitution S of J but not in /, which therefore does not multiply all
the indices by the same factor. Then by § 7, 8 is not commutative with every
B:z,,x¢. 4 being a particular mark + 0,e.g.4 = 1. To fix the ideas, suppose
Sis not commutative with BL: ,<,. The substitution
i ie See es Ly 1, Ae
will thus not reduce to the identity. Further 7’ belongs to 7; for the trans-
formed of S by Bz, ,¢, belongs to /, since Lz, ¢, has the determinant unity and
thus is in /*
To express the substitution Z, we note that, for 7 > 1, Bz, yz, leaves §;
ay os .
unchanged ; that S replaces ¢, by + 4,¢,, which B;',, replaces by
i fad .
e
ta,
2 Oy5; — Ady, ,
Sh
which in turn S~' replaces by ¢, — 4a,y, if g denotes the linear function by
which S~! replaces €,. Thus Z’ has the form
m
ay Spel te ae ee ’ eels
es = 2 Bess Gi, = 5; — Adin (ia eer oath)
j=
where it is not necessary to determine the /,,'s more closely. In this expres-
sion of 7’, which is the basis of the further developments, there is no longer
any trace of the ¢,-specialization in Bz, yz.
130 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
11. Let us first suppose that m > 2.
(1) Suppose a, = 0 (2 = 2, 3,...,m). ‘Then #,, = 1, the determinant
of 7 being 1; while f,, (7 = 2,..., m) are not all zero, since 7 is not the
identity. Let us take /,, + 0, changing if necessary the previous order of the
independent indices &,, €, ..., &n-
To simplify Z’ we take a new system of independent indices 7,in place of
the former ones ¢,, viz
is
(2 ==; Lae ete POET EOD
ss
IL he
mee)
Syyp
os)
=
SVp
which is permissible since the determinant of transformation is f,, +0. Then
ne m
ta Sn ay, af iS. i= LYN Ops fa yy
=! S40 = Pie Busi + = Sys; = 7 + 4
Yj 92
; =
‘4 ’ ald f) i _
43 = = PSs = = Puss = 4 -
j=2 4==2
AN Se akg pee ay a es ik 5
Hi ‘FZ Pe ee Cay Fae Big es AT
Hence 7’ becomes simply B,,,,. But by the Remark of § 5, [ contains
the substitution Z (of determinant unity)
PAE ae Pitter SUL eR tn 2 eC “ie
M =H 3 Gy = es Hi = 15 (2 = 3,..., m)
where / is an arbitrary mark + 0 of the G7 [p"]. Hence / contains Z7'7'Z,
i.e. B
nine Also / contains the substitution V7, of determinant unity,
am + Chad A 3d Spytita’ ps Agni ge ee “ aM ae coe (a= Sa eee et
De es Dh 8 Oh, ee a oe litk k>2
2}
Hence J contains /;;' B,,,,,U7;,, which gives for k = 3 the substitution
BG... xn, wad for > 3 the substitution B,,,,,. Likewise 7 contains the trans-
formed of these substitutions, etc., so that clearly 7 will contain all the substi-
tutions
hoe ae (0° = Fete ete)
But by § 6, these substitutions combine with each other to give every substi-
tution of /} i. e. of determinant unity.
(2) If not every a, (2 = 2,3, ..., m) is zero, suppose a, +0. Take
Tis Noy +++) Ym a8 independent indices where
pA eee ee en ain f eine ae |
Th Sie U2 as. haat, aoe eee (ire= ? sistema die)
“21
the determinant of transformation being unity.
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 131
The m — 2 indices 7; (i > 2) are unchanged by 7’ (of § 10); thus
wi 5 GC; — 5 f= G; .
je (5; sa 20,0) SAS coe hy) =< Hi
ees Foy
Hence the substitution 7’ takes the form
a
m
tik eee SY Lee Aus abet, Ree SS fia
ieee ee acer Tyla i eI 2),
a= =
where (by Remark of § 5) the determinant of 7’is
tute — fen = 1.
In this form of 7’ the indices 7,, 7, play the same role.
(2a) Suppose 7, and 7,; (2 = 3, ..., m) are not all zero. Changing if
necessary the order of 7, 7, .--, 4m, We may suppose that 7,, and 7., are not
both zero.
The text in Jordan (I. c. p. 108, 1°) is here incorrect, but may be modified
as follows, if our linear substitutions be on four or more indices ¢ :
I will contain the substitution
Wheel Fe I ste. TB.
N3y M4 Ns, MNa ?
(~ being an arbitrary mark + 0 of the GF'[ p"]) viz
I = — fT Te =e — Uw MH =. (1 =3,..., m)
Suppose for definiteness that 7,, + 0, and take w,,..., w,, a8 independent
indices, where
Op Fi Tin 5 Og = To — Ta/ M13 Ot = Em “(1 = 8; 2)
Then for the substitution 7) we find
~ , )
pe Se at ed BYE ee
{= — =:
hs 113
wO, + LO,
, , , : om |
Le ede = I == (2 — LY 3hs) — & Ditrs eo ihe
On Ne WO, (2 een a)
Hence 7) takes the form B,,,.,, which combined with its transformed by
the substitutions of J’ will give as in (1) all the substitutions of /.
152 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
For the case of three indices,* I contains the substitutions
Ti [AR em Ty viz
Nis PMNS Niy KN3)
~)
I = GL) OS i Sh
{jit = Yip aw GT 3 eee iand3» Fa = 43-
Now Z, and 7, are both of the form U:
=I + O35 Yo = Yo + F235 Ys = 7 -
If both Z} and 7; reduce to the identity, 7’ becomes
= + 113933 Ye = M2 + Fo3%33 Is = Ns»
which is of the form l/, Hence in any case we have a substitution of the
form Y and not the identity. We then take ,, ,, w,, defined above as inde-
pendent indices and obtain for U/ the form B,,....
(2b) Suppose
hi = 7x =O. (irs ov aye)
Since 7’ does not veduce to the identity, we can not have simultaneously
Yr = Ye = 1, Y= Yr =O.
Hence if we form 7, and 7’, above for m indices, e. g. 7 is
vie Seed epee 4 (gaia) 433 7 = Yo — PY¥n93 > Hi = 73 (a eta rye eC)
we see that one of the two must not be the identity and we proceed as in (2a).
12. The case m = 2.
Let S be a substitution of 7 but not in /7, which therefore does not mul-
tiply both indices by the same factor. Let 7, be a function of the indices §,
and € which S does not multiply by a constant factor, e. g. 7, = ¢, + &; let
7, be the new function by which S replaces 7,. Since 7, and 7, are linearly
independent, we may take them as new indices, when S becomes (having
determinant 1)
NM = hs Gy = —H + OH. ‘
Now / contains the substitution 7’
Wi 0s Ys a (a + 0)
*M. Jordan was kind enough to send mea correction of the error above mentioned. His proof
appears valid however only for three indices. It is given here with the usual modifications.
»
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 13%
Hence / will contain UV = 7 “1S7S, viz
My = — 2 5 YY = — O(1 + a”) 4 — O,.
(1) Suppose od ¢ 0.
Then / will contain (/*, which for 2 = 1 becomes
i =| 3 My = 409, + Ap.
If p > 2, we can replace 7, by another index
@ = Adn,.
Then U/? becomes G,, 5. But /' contains the substitution V,
ete se oe
Thus / contains V~*0*V or Bb, _.,,.
If Z denote the substitution belonging to [
CET AED p= AN, (A = any mark + 0)
f will contain the substitution Z“B,, 4 or By, a24:
By virtue of the property
Bie APp * ie Arh aaa ae (A? + Az) >
we must reach a substitution 2, ,4, where » is a not-square in the G/’[ p”),
p being > 2 by hypothesis. For, if not, the totality of the (p” — 1)/2 squares
in the G/'[ p"], together with the mark zero, would form not only a multipli-
cative but also an additive group and therefore* a Galois field of order say
p” included in the GF'[ p"]. But p’ = p, qua additive period of every mark
7 Ose Lbus
res . Deby seal De,
which is impossible.
Having one, we reach every not-square by the formula
—l i)
L No, vb L oe ae ae A2vp *
Thus for 0+0 and p > 2, Z will contain all the substitutions 5, ,4, and
By. ung -. being an arbitrary mark + 0 ef the GF [_p"], and hence all the sub-
stitutions of 1
(2) Suppose 0 = 0.
(2a) If p” = 2? or if p” > 5, we can find a mark a:0 of the GF'[7"]
such that a + 1 and then a mark / such that
B (at — 1) = pw = any mark : 0.
* Moore, l. c. § 40.
134 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
Then / contains the substitution
LB U B
| :
N1y BN2 U » VIZ
=
N15 Bn2
m= + BC —1)%3 He = ts
or B,. un,» Which combined with its transformed by the substitutions of J will
produce J.
(2b) If p" = 5, we may take as independent indices
wo, = 2m, + 3 Oy = — 2p +
Then S will become
WO; == 20,30 == AO
Thus / contains the substitution
27 BS yet
SB; S Das = Devas
19 2
and hence also its cube 5, .,.
(2c) For p" = 2, the linear homogeneous group on two indices has the
order (27 — 1) (2? — 2) = 6. It contains a subgroup of order 3 formed of
the powers of the substitution
These ea + &,
which represents the literal substitution (¢))) (4)4:/,)). The index of this sub-
group being 2, it is self-conjugate. The factors of composition are thus 2
and 3.
(2d) For p" = 3, we may prove that the (3? — 1) (3? — 3) = 48 substi-
tutions of the linear homogeneous group & of degree 9 are derived from
(A) Fo ae C3 Sc ee ee
(B) cies Pee sy ett
(C) Cee es eee
(D) Cf = Sa S25) Se Se ae
(E) Pee tes eS
Thus for the groups
{FEY {#, DEA, DOV AL, D, OC, By ED eC eeaa
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. 135
we may verjly the following generating relations :
Ae We
TB IK IND cee WOE.
OMe PAO eee OS GD ah DC..
Dim eb bee hee be DP.
Ae eee Ape) = GAN eA (1 DAs AB en Ob A.
From these relations it follows at once that the above groups have for orders
2, 4, 8, 24, 48, respectively, and that each is a self-conjugate subgroup of the
following. Hence the factors of composition of @ are 2, 3, 2, 2, 2.
13. Since the quotient-group* of any two consecutive groups in the series
of composition of any group is a simple group, we have the result that //H
is a simple group of order
2(m, n, Pp) Mi ies fen) 1) Co ws pe) a) you EEA Ea)
d(p"—1) d(p” — 1)
except in the cases (m, n, p) = (2, 1, 2) and (2, 1, 3).
Compare section IT.
Srcrion II.—Zinear Fractional Group.+
14. In our generalized linear homogeneous group @ of degree p™” on m
indices, let us class into the same system the p” — 1 letters
l
Men, Bega = oy bEm
where the €/s are fixed but » runs through all the marks except zero of the
GH { p"], or, otherwise expressed, the p” — 1 letters corresponding to the
same values of the ratios ¢,/&,, (¢ = 1, 2,..., m — 1).
Each substitution of G will replace the letters of any one system by letters
all of some one system. We have thus (p”” — 1)/(p” — 1) systems, whose .
displacements (by the substitutions of G) form a group // of degree ( p”” — 1)/
(p" —1). But there are exactly py" — 1 substitutions of G which do not dis-
place any system, viz,
. m Gs Lee eet)
: oe Lu = any mark ¢ 0}
wVy
!
* Holder, Mathematische Annalen, vol. 34.
+ Compare Jordan, 1. c. Arts. 315-317; Betti, 1. c. vol. 3, p. 74, 1852.
PM °
136 DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS.
The substitutions of /7 may be exhibited thus:
m nm mm”
(ex, pps hone a fant 8s Ve mlat 7 ge 8M is
Sy We ele es. \° bie a ae = AyjS5 . =F y5; om (et Ohne =F yjSj .
j-l yt Fil
,
es
Cae
can
The order of //, being the total number 2(m, n, p) of the substitutions
in G divided by the number of those leaving the systems invariant, is thus
Q(m, n, p)/(p” — 1).
15. The linear fractional group // is clearly meriedrically isomorphie with
the linear homogeneous group G. To the subgroup G” formed of those sub-
stitutions of G whose determinant is unity there corresponds a subgroup /T7’
formed of those substitutions of /7 whose determinant is unity, or, as is equiv-
alent, whose determinant is any th power in the G/’[ p"]. For the substi-
tutions of /7 remain unchanged by multiplying the m homogeneous indices by
the same mark yv, which multiplies the determinant by yp”.
Let d be the greatest common divisor of m and p" — 1. Then* the
proportion of marks (excluding zero) of the G/’[ p"|] which are mth powers
is 1:d. Hence the order of 7’ is 2(m, n, p)/d (p” — 1).
Now,t the maximal self-conjugate subgroup of G" is, for (sn, n, p) ¢ (2, 1, 2)
or (2, 1, 3), the group of substitutions which multiplies every index by the
same mark. The subgroup of 7’ isomorphic with it is evidently 1. Hence
the group //7’ of the linear fractional substitutions on mm — 1 indices having
determinant unity (or any mth power) is a stmple group of degree (p"" — 1)/
(p" — 1) and order 2 (m, n, p)/d (p” — 1), with the two exceptions (m, n, p)
= (2, 1 2jiand. (2515-3):
16. The triply-infinite system of simple groups thus reached affords a
direct generalization of the doubly-infinite system obtained} differently,
BOD) ep a tty eon)
P(e" —1), p=%, (wnt, 1).
*Proof. A mark / + 0 is an mth power in the GF'[p"] if and only if
(p” —1)/m
p = ih, @))
By raising (1) to the power m/d, we find a necessary condition,
p —1)/d
ui? ye 1a: (2)
But the condition (2) is sufficient. For, m/d being prime to p” — 1, the extraction in the G#H'[ p”]
of the root mid is (by Part I, § 18) always possible and indeed uniquely. Hence from (2) we
derive (1). Thus the ( p” —1)d marks satisfying (2) [cf. Moore, 1. c. § 32] give the mth powers
in the GF'[ p”].
t Section I, §§ 8-12.
{E. H. Moore, A doubly-infinite system of simple groups, Bulletin of the New York Mathemat-
ical Society, vol. 3, pp. 73-78, 1894.
DICKSON. ANALYTIC REPRESENTATION OF SUBSTITUTIONS. tor
Thus
2 (2, n, D) ra Gae ies 1) Gis tes Ve) rs p" Ge 1)
d(p" —1) d(p" — 1) d
where d is the greatest common divisor of 2 and p" — 1.
17. Our triply-infinite system of simple groups yields exactly 13 having
an order < 10,000, viz :*
60: = ((2, 1, 5)) = ((2, 2,2)) = 4.5!
TGS (els 1) ((8e162))
360 ent), 22 3)\=d 6!
504 = ((2, 8, 2)).
Gale (2.1 11).
1092 = ((2, 1, 18)).
2448 =- ((2, 1, 17)).
3420 = ((2, 1, 19)).
4080 = ((2, 4, 2)).
5616 = ((3, 1, 3)).
6072 = ((2, 1, 23)).
7800 = ((2, 2, 5)).
9828 — ((2, 3, 8)).
The simple group of order 4 . 7! = 2520 is not found in this list. Of interest
is that of order
20160 = ((4, 1, 2)) = ((8, 2, 2)) =4.8!
By noting that the number 2 (m, n, p)/d(p" — 1) contains the factor p
exactly to the power nm (m — 1)/2, we may prove that 4. V! is not of the
form ((m, %, 7)) for 8 3.
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