  We prove the case t = 2 of a conjecture of Bruns-Conca-Varbaro, describing
the minimal relations between the t x t minors of a generic matrix.
Interpreting these relations as polynomial functors, and applying transpose
duality as in the work of Sam-Snowden, this problem is equivalent to
understanding the relations satisfied by t x t generalized permanents. Our
proof follows by combining Koszul homology calculations on the minors side,
with a study of subspace varieties on the permanents side, and with the
Kempf-Weyman technique (on both sides).
