Dear GAP Forum,

My apologies if these are easy questions, but I’m very new to computing with 
GAP.

I would like to construct a nilpotent endomorphism N acting on an even 
dimensional vector space V, that is self-adjoint with respect to a symplectic 
form.

Up to conjugacy, the Jordan blocks of a nilpotent matrix N are given by a 
partition \lambda of some non-negative integer.  So I would like to be able to 
construct the nilpotent endomorphism as follows:

  *   Given a partition \lamba, construct nilpotent matrix N whose Jordan 
blocks have size the parts of the doubled partition \lambda \cup \lambda 
(doubled partition because the vector space is even dimensional);
  *   A bilinear form on the (preferably rational) vector space such that N is 
self-adjoint with respect to this bilinear form  (I understand that while GAP 
can construct vector spaces over the rationals, it only constructs bilinear 
forms on vector spaces over finite fields?) I was trying to use the 
BilinearFormByMatrix function, but was finding it hard to control the basis 
with respect to the matrix N in that case.

Any help/tips with GAP’s inbuilt functions would be greatly appreciated. Again, 
apologies if these are naive questions but I’ve not done any serious 
computation in GAP before and am doing my best to learn the ropes.

Best wishes,
Neil

University of Greenwich, a charity and company limited by guarantee, registered 
in England (reg no. 986729). Registered Office: Old Royal Naval College, Park 
Row, Greenwich SE10 9LS.
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