数学物理学报(英文版) ›› 2000, Vol. 20 ›› Issue (4): 515-521.
张显, 曹重光, 胡亚辉
ZHANG Xian, CAO Chong-Guang, HU E-Hui
摘要:
Suppose F is a field of characteristic not 2 and F its multiplicative group.
Let T
n(F) be the multiplicative group of invertible upper triangular n × n matrices over
F and ST±
n (F) its subgroup {(aij ) 2 T
n(F)|aii = ±1, 8i}. This paper proves that f :
T
n(F) ! T
n(F) is a group automorphism if and only if there exist a matrix Q in T
n(F)
and a field automorphism of F such that either
f(A) = (A)QAQ−1, 8A = (aij ) 2 T
n(F)
or
f(A) = (A−1)Q[J(A)−T J]Q−1, 8A = (aij) 2 T
n(F),
where A = ((aij)), A−T is the transpose inverse of A, J =
n
Pi=1
Ei n+1−i, and :
T
n(F) ! F is a homomorphism which satisfies { (xIn)(x)|x 2 F} = F and {x 2
F| (xIn)(x) = 1} = {1}. Simultaneously, they also determine the automorphisms of
ST±
n (F).
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