Skew field :
multiple . not
.Commutative
Quaternions
(
' '- 4. din complex
: field
- r skew field
DESARGUES 's than
^
Hue
in Prog:
Geom
.- ver)
- |P
Y
near-field
¥¥÷÷*⇒*
. do b
cGa
y=ax+b
|P in Prog : Geom Hue . - * * Y near-field . do b c - - PDF document
Skew field : multiple . not . Commutative ' ' " ) Quaternions 4. din complex ( or skew field : field over ) ^ DESARGUES 's than |P in Prog : Geom Hue . - * * Y near-field . do b c y=ax+b Ga 's plane prog DESARGUES
Skew field :
multiple . not
.Commutative
Quaternions
(
' ': field
DESARGUES 's than
^
Hue
in Prog:
Geom
.Y
near-field
. do b
cGa
y=ax+b
prog
's plane
DESARGUES ← division ring
Finite division rig
are fields
EDDERBURN
finite
2→ Galois
non - DES . planes
h
htt
= #pts on a line117=111
n'tntl
W={ n ftp.p
. of order n}N z { prime powers )
✓ = {orders of finite pp
. }N Z {prime powers }
all
known f.pp
. s haveprime
power order
TAM
Tf
n =L
mod 4
⇒ (Fa
,b) ( n= a't b
')
3 45 6 7 89
10
11
12
✓ u
r -
X
u r - f
175
1990
10 EIN
2
LATIN
SQUARE
hxn
11
2-332
2231
13
33
12.21
ORTHOGONAL
I.Squares
EI
. Ifn odd 23
⇒ 7- pair of orthog. L
.SquaresEX .
F
. .4×4
i .EI
.F
"axa
bxb
→ ab
x ab
missing
:h
2141
EULER h=6
"36 officers problem
"1903
:No
6×6
HE 2 (4)
1960 's
BOSE-SHRIKHANDE- PARKER
Hn E 2 (4)
,n > G
F pair of ortho L Sgs
n = 6If
n - pk
⇒ Fn- I
pairwise orth Lsgs
Sf
L
, . . ( mare
rainworth
.nxn
L . Sgs
⇒
m En
← Ffpp ardern .
LATIN
RECTANGLE
kxn
rows :
2312
perm's of
I?
Col's
:all el's distinct
THI
Every Latin rectangle
can
completed to a L
. Sq .SYSTEMS
SDR
DISTINCT REPRESENTATIVES
H=(V. E)
E={ E ,
. . . Em }ve
. EE,all vi. distinct
SDR
if
←
m > n
ease
I !f¥il4I
!
Hall
KENG
3- SDR ⇒ * Hale .gs#oSDRG6oDCHARACT
DENYING
1916
kzl
k - uniform
, k-regular hyp .EI
→ satisfies
Hall condita.
(§ obstacle)
ftp.iI-SDRE#kxnL.Recfayle
Ken
→ extend to
date) x n
L . Rect .
m=n4
i
Et
.?
k
bk4k=
M /¥¥/
k¥0
⑨ ④ nk
÷
. .tn : Fwm =LE
, EjEm Col
# SDRS
= # rook placements
A = Cag
.)nxn
Permanent
per CAKE
IT ai sci)
GE pen
= per M
I
incid . matrix
* row : prob
. distributionaij to ¥
, ai;=/
A
doubly stochastic
:& same for columns
Iho
' . .? )( i ! ! )
perm
. motor .A doubly Stoch:
aij 20
A Sow a l
tf
Solemn =L
EXAMPLES
permutation matrices
n !
! ! : it
a-
=
= 1
Der ( I J )
=
h '
Per (T )
= h !
hi
> In
Per A- § Tain!
( ( a ) - ha
2THM
Per CI) =L
are"
Vander Woerden's
permanent confect
.PERMANENT IN EQ .
h
"1976
EGTRYCHEVTIALIKMAN ER
per A
E t
=L ⇐ A permit
.matrix
→ MANY
SDR
K- unit
, k -reg→ MANY
Lat . Sg
Llnl
"
STS