14,348 reputation
23286
bio website sci.ccny.cuny.edu/~benjamin
location New York City
age 41
visits member for 3 years, 4 months
seen 1 hour ago

I am an algebraist interested in a broad range of areas. I've worked on semigroups, geometric group theory, algebraic combinatorics, representation theory, self-similar groups (aka automaton groups), profinite groups and random walks on semigroups and groups. I've been particularly interested in interactions between these areas and Computer Science and am fond of algorithmic questions. I've also dabbled with operator algebras associated to etale groupoids and inverse semigroups. Currently, I am interested in applications of finite semigroup theory to finite state Markov chains.

My blog is http://bensteinberg.wordpress.com/author/bsteinbg/


1h
comment Marshall Hall's theorem for surface groups
voting to close as no longer relevant because it is answered in comments.
1h
answered Which groups are LERF?
Oct
21
accepted What version of the wreath product embedding theorem is actually stated in the famous paper of Kaloujnine and Krasner?
Oct
20
comment What version of the wreath product embedding theorem is actually stated in the famous paper of Kaloujnine and Krasner?
Thanks for locating it. I will have to read this on a bigger screen then my phone.
Oct
20
revised What version of the wreath product embedding theorem is actually stated in the famous paper of Kaloujnine and Krasner?
Typo
Oct
20
revised What version of the wreath product embedding theorem is actually stated in the famous paper of Kaloujnine and Krasner?
added 53 characters in body
Oct
20
revised What version of the wreath product embedding theorem is actually stated in the famous paper of Kaloujnine and Krasner?
edited title
Oct
20
asked What version of the wreath product embedding theorem is actually stated in the famous paper of Kaloujnine and Krasner?
Oct
20
comment How to find or constrain “particularly good” (two-sided) spectral expanders?
@Asaf, I heard Lubotzky speak about 4 weeks ago and he definitely said psl2 gives 2-sided expanders.
Oct
9
comment Pseudovarieties of monoids
Is there a uniform bound on the number of variables needed to define any subvariety?
Oct
8
comment Two questions about axiomatic rank of groups
For question 2 Mark Sapir proved a finite semigroup is finitely based iff it has finite axiomatic rank in your sense. He may have used that all finite groups are finitely based though. So most likely the answer is no.
Oct
8
comment Two questions about axiomatic rank of groups
For question 1 what do you mean by equivalent.
Oct
7
comment Two questions about axiomatic rank of groups
What is axiomatic rank? Number of identities or variables?
Oct
2
comment Reference request for generalization of groups with out identity element?
If by divisibility you mean $ax=b$ and $ya=b$ have solutions for all a,b then you have a group.
Sep
30
awarded  Explainer
Sep
28
comment A question about transitivity
The numbers $1/n$ together with $0$ is compact in the usual metric and countable.
Sep
26
revised Finite Dimensional Simple nonunital associative Algebras
edited body
Sep
26
revised Finite Dimensional Simple nonunital associative Algebras
added 13 characters in body
Sep
26
answered Finite Dimensional Simple nonunital associative Algebras
Sep
25
comment Finite Dimensional Simple nonunital associative Algebras
This can be found in Curtis and Reiner. I believe it was first proved by Burnside, maybe assuming algebraically closed.