English

Unbounding Ext

Representation Theory 2012-08-31 v2 Group Theory Rings and Algebras

Abstract

We produce examples in the cohomology of algebraic groups which answer two questions of Parshall and Scott. Specifically, if G=SL2G=SL_2, then we show: (a) dim\ExtG2(L,L)\dim \Ext_G^2(L,L) can be arbitrarily large for a simple module LL; and (b) the sequence maxLirreddimHk(G,L)\max_{L-\text{irred}}\dim H^k(G,L) grows exponentially fast with kk.

Keywords

Cite

@article{arxiv.1101.3004,
  title  = {Unbounding Ext},
  author = {David I. Stewart},
  journal= {arXiv preprint arXiv:1101.3004},
  year   = {2012}
}

Comments

14 pages; version to appear in J. Alg

R2 v1 2026-06-21T17:12:36.394Z