Let Mn,n denote the vector space over a field F=R or C of n×n matrices with entries in F. Given B∈Mn,n, consider the two linear transformations RB,LB:Mn,n→ Mn,n defined by
LB(A)=BA,RB(A)=AB
(a) Show that detLB=(detB)n.
[For parts (b) and (c), you may assume the analogous result detRB=(detB)n without proof.]
(b) Now let F=C. For B∈Mn,n, write B∗ for the conjugate transpose of B, i.e., B∗:=BˉT. For B∈Mn,n, define the linear transformation MB:Mn,n→Mn,n by
MB(A)=BAB∗
Show that detMB=∣detB∣2n.
(c) Again let F=C. Let W⊆Mn,n be the set of Hermitian matrices. [Note that W is not a vector space over C but only over R.] For B∈Mn,n and A∈W, define TB(A)=BAB∗. Show that TB is an R-linear operator on W, and show that as such,
detTB=∣detB∣2n