Claudio Gorodski
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 2d reviewed Approve Can the work of Hardy & Ramanujan about partitions shed light on Hardy-Littlewood's k-tuple conjecture? Apr 11 comment Projections of orbifolds @Allen: it is true. In fact it is mentioned in Terng's paper. Apr 8 revised Projections of orbifolds These are not orbifolds. Apr 8 comment Projections of orbifolds By the way, these are not orbifolds, but generalized flag manifolds. Apr 8 revised Projections of orbifolds Added reference. Apr 8 answered Projections of orbifolds Mar 22 awarded Nice Answer Feb 21 awarded Necromancer Feb 1 awarded Good Answer Jan 13 comment embedding of quaternionic projective spaces The embedding can be geometrically described as follows. Let $V$ be the real vector space of $3\times3$ Hermitian quaternionic matrices with fixed (real) trace, say $1$. Note that $\dim V=14$. $\mathbb HP^2$ embeds into $V$ by mapping each quaternionic line in $\mathbb H^3$ to the matrix representing the corresponding orthogonal projection onto it. The image of the embedding in $V$ consists of the idempotent matrices, and it is also an orbit of the action of the group $Sp(3)$ on $V$ by conjugation. The image sits in the unit sphere of $V$, so it can be stereographically projected to $R^{13}$. Jan 8 revised Is there a formula for the Frobenius-Schur indicator of a rep of a Lie group? Added table. Jan 8 answered Is there a formula for the Frobenius-Schur indicator of a rep of a Lie group? Dec 24 reviewed Approve How to solve $f(f(x)) = \cos(x)$? Dec 24 comment Manifolds as simultaneous coset spaces The existence a $G$-equivariant map $F:X\to Y$, namely, one such that $F(gx)=gF(x)$ for all $g\in G$, $x\in X$, is a necessary and sufficient condition. Oct 25 reviewed Approve Computational complexity of low rank SDP Jul 27 revised Check symplectomorphism property on infinitesimal generators Added explanation. Jul 27 answered Check symplectomorphism property on infinitesimal generators Jul 22 accepted Calculation with weights of $E_6$ Jun 9 awarded Nice Answer May 16 awarded Yearling