15,594 reputation
23594
bio website sci.ccny.cuny.edu/~benjamin
location New York City
age 42
visits member for 3 years, 10 months
seen 33 mins 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/


16h
accepted A question of terminology regarding integer partitions
Apr
24
comment A question of terminology regarding integer partitions
It will take me a moment to digest this. Thanks for the answer.
Apr
24
comment Profinite Topology
Some people found J*G=JmG weird. Perhaps I want V closed under extension and W locally finite
Apr
23
asked A question of terminology regarding integer partitions
Apr
23
comment Profinite Topology
Maybe it is not true but It's my feeling
Apr
23
comment How to prove that a projective module is not free?
Is A a finite dimensional algebra over a field or at least finitely generated over a field or over Z?
Apr
22
comment “Diagonalizing” an associative algebra
You need more than commutative and semisimple in the finite dimensional case: you need that the algebra splits over the ground field. If the ground field is not algebraically closed, you can get commutative semisimple algebras which are not diagonalized by just taking an finite extension.
Apr
20
revised Pro-G_p*G_q topology, profinite topology
edited tags
Apr
20
comment What is the mathematical structure called if we replace commutative group by commutative monoid in the definition of linear space?
These things really should be called modules over semirings. If you are over a ring, you will get a module anyway so it is clear that the "deficiency" (or semi) is in the ``ring'' not the module.
Apr
20
comment Pro-G_p*G_q topology, profinite topology
This is wide open
Apr
16
comment Sets of natural numbers such that sums of a bounded number of its elements form a semigroup
Regular subsets of N are the union of a finite set with an arithmetic progression. Can anything be said about other sets?
Apr
14
revised pseudovarieties and profinite group : do * and g() commute?
edited body
Apr
14
comment pseudovarieties and profinite group : do * and g() commute?
Here it should be mentioned that semidirect products of categories are defined via the Grothendieck construction
Apr
14
revised pseudovarieties and profinite group : do * and g() commute?
edited tags
Apr
14
revised pseudovarieties and profinite group : do * and g() commute?
Fixed link
Apr
14
comment pseudovarieties and profinite group : do * and g() commute?
@YCor, it is the pseudovariety of categories generated by the monoids in V viewed as one-object categories.
Apr
14
answered pseudovarieties and profinite group : do * and g() commute?
Apr
13
awarded  Necromancer
Apr
13
comment classifying pairs of idempotent matrices
If the characteristic is not 2, then A is an idempotent iff I-2A is an involution. So you are essentially looking at the representation type of the infinite dihedral group. Quick googling of representation type infinite dihedral group gave me a chapter of a book by Benson giving all indecomposables from which you can deduce tame
Apr
11
comment Groups acting on complexes
Usually people just remove the center instead of e. The 1-Skeleton is called the commuting graph. Lots of people look at this