35,357 reputation
545111
bio website math.temple.edu/~rivin
location USA
age
visits member for 3 years, 4 months
seen 8 hours ago

Professor of Mathematics at Temple University. This year the ICERM Visiting Professor at Brown (and ICERM).


15h
revised Is the diameter of a centrally symmetric convex body realized by a pair of antipodal points?
fixed name spelling
23h
reviewed Approve suggested edit on “Limited angle” in n-dimensional Radon transform?
23h
reviewed Approve suggested edit on Partial recovery from Radon transform
23h
answered Linear Programm with matrix
1d
answered Random walk in a convex body or convex polytope
Apr
19
comment Subgroups of $SL_3(\mathbb{Z})$ that are finitely generated, Zariski-dense, infinite index, and torsion-free
Actually, the subject of discrete subgroups with opposite unipotents was started in the (now classical) paper of T.N.Venkataramana in the late '80s. I am not quite certain what the value added in Oh's thesis is, maybe @YvesCornulier knows...
Apr
18
reviewed Approve suggested edit on What was the Question that led Euler to his Investigations on Polyhedra?
Apr
18
comment Characterization(?) of coersive(?) elements in the special linear group
Great, waiting with bated breath! Re finiteness, the set of elements in $SL(n, \mathbb{Z})$ of norm (any norm) bounded by $x$ is asymptotic to $x^{n^2-n}$ -- this is due to Morris Newman for $n=2$ and Duke, Rudnick, Sarnak in general (so $S_x$ is strictly smaller).
Apr
18
answered What was the Question that led Euler to his Investigations on Polyhedra?
Apr
18
comment Subgroups of $SL_3(\mathbb{Z})$ that are finitely generated, Zariski-dense, infinite index, and torsion-free
@YvesCornulier I was doing this late at night, so I should have added a "morally" -- my thinking is that Venky's result could probably be extended to do what you suggest...
Apr
18
comment Characterization(?) of coersive(?) elements in the special linear group
@GeoffRobinson In fact, I REALLY care about $SL(n, \mathbb{Z})$ so if you can say something about that case, please do :) Submultiplicative norm (e.g. operator norm, I guess) works fine for me...
Apr
18
comment Subgroups of $SL_3(\mathbb{Z})$ that are finitely generated, Zariski-dense, infinite index, and torsion-free
And another edit...
Apr
18
revised Subgroups of $SL_3(\mathbb{Z})$ that are finitely generated, Zariski-dense, infinite index, and torsion-free
added more
Apr
18
comment Subgroups of $SL_3(\mathbb{Z})$ that are finitely generated, Zariski-dense, infinite index, and torsion-free
See the edit to my answer.
Apr
18
comment Subgroups of $SL_3(\mathbb{Z})$ that are finitely generated, Zariski-dense, infinite index, and torsion-free
@YvesCornulier see the edit.
Apr
18
revised Subgroups of $SL_3(\mathbb{Z})$ that are finitely generated, Zariski-dense, infinite index, and torsion-free
added extensive explanation
Apr
17
answered Subgroups of $SL_3(\mathbb{Z})$ that are finitely generated, Zariski-dense, infinite index, and torsion-free
Apr
17
answered Is the diameter of a centrally symmetric convex body realized by a pair of antipodal points?
Apr
17
comment Links between Geometric Group Theory and Number Theory
I don't think Church/Farb found a new proof of the prime number theorem, but rather a way to count irreducible polynomials (of given degree) over $F_q,$ which was first done by Dedekind [I believe], and is a matter of simple combinatorics (it is an exercise in Knuth volume 2). Also, I would not call this Church/Farb work "geometric".
Apr
17
asked Characterization(?) of coersive(?) elements in the special linear group