3 research outputs found
Canonical matrices of bilinear and sesquilinear forms
Canonical matrices are given for
(a) bilinear forms over an algebraically closed or real closed field;
(b) sesquilinear forms over an algebraically closed field and over real
quaternions with any nonidentity involution; and
(c) sesquilinear forms over a field F of characteristic different from 2 with
involution (possibly, the identity) up to classification of Hermitian forms
over finite extensions of F.
A method for reducing the problem of classifying systems of forms and linear
mappings to the problem of classifying systems of linear mappings is used to
construct the canonical matrices. This method has its origins in representation
theory and was devised in [V.V. Sergeichuk, Math. USSR-Izv. 31 (1988) 481-501].Comment: 44 pages; misprints corrected; accepted for publication in Linear
Algebra and its Applications (2007
Canonical matrices of isometric operators on indefinite inner product spaces
We give canonical matrices of a pair (A,B) consisting of a nondegenerate form
B and a linear operator A satisfying B(Ax,Ay)=B(x,y) on a vector space over F
in the following cases:
(i) F is an algebraically closed field of characteristic different from 2 or
a real closed field, and B is symmetric or skew-symmetric;
(ii) F is an algebraically closed field or the skew field of quaternions over
a real closed field, and B is Hermitian or skew-Hermitian with respect to any
nonidentity involution on F.
We use a method that admits to reduce the problem of classifying an arbitrary
system of forms and linear mappings to the problem of classifying
representations of some quiver. This method was described in [V.V. Sergeichuk,
Math. USSR-Izv. 31 (1988) 481-501].Comment: 57 page