bio  website  sci.ccny.cuny.edu/~benjamin 

location  New York City  
age  42  
visits  member for  3 years, 11 months 
seen  17 mins ago  
stats  profile views  8,028 
I am an algebraist interested in a broad range of areas. I've worked on semigroups, geometric group theory, algebraic combinatorics, representation theory, selfsimilar 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/
2h

comment 
Idempotent ideal in ring of continuous functions
Continuous functions on what space? If your space is totally disconnected there can be lots of idempotents 
6h

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Are monoids with zero and partial homomorphisms related?
I mean if f(a) and f(b) and f(ab) are defined then they are equal. 
10h

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Are monoids with zero and partial homomorphisms related?
I don't require the domain of a partial homomorphism be the whole semigroup. I think one should allow the most lax notion of partial. Equality should only be required when everything is defined 
1d

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John Nash's Mathematical Legacy
I flagged for CW so that we can upvote. I am sorry to hear the news 
1d

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Earliest source for a Lie algebra construction
Making a new semigroup or of an old one by fixing an element x and mapping (a,b) to axb is called a variant and has been around since probably the 50s or sixties. 
1d

answered  Are monoids with zero and partial homomorphisms related? 
2d

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On sentences true in all finite groups
@JoelDavidHamkins, I am not sure whether it can be recoded 
2d

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On sentences true in all finite groups
cmi.univmrs.fr/~coulbois/articles/equation.pdf gives an equation which has a solution in all finite groups but not in the free group. 
May 22 
comment 
Different ways of having infinite global dimension
I think you can find such examples by googling but from what I read it is unknown if there is a ring which is both left and right noetherian whose simple modules all have finite projective dimension but who has infinite global dimension 
May 22 
revised 
Different ways of having infinite global dimension
added 211 characters in body 
May 22 
comment 
Different ways of having infinite global dimension
Let me think. But in any event this shows that if your hypothesis is true then all cyclic modules have finite projective dimension and your direct sum condition doesn't help. So what you really want is an example where each cyclic module has finite projective dimension which is unbounded. 
May 21 
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pseudovarieties and profinite group : do * and g() commute?
@user182085, By the way it is usual to accept an answer when somebody gives one. 
May 21 
comment 
Different ways of having infinite global dimension
Sometimes we miss something simple. 
May 21 
comment 
Different ways of having infinite global dimension
By the way for Artinian rings the global dimension is always carried by simples. 
May 21 
revised 
Different ways of having infinite global dimension
added 274 characters in body 
May 21 
comment 
Different ways of having infinite global dimension
Since Ext commutes with direct sums you get that a summand in a finite direct sun of modules of finite projective dimension has finite projective dimension. 
May 21 
comment 
Different ways of having infinite global dimension
If a cyclic Rmodules is a retract of a direct sum then it is a retract of a finite direct sum because the splitting takes the generator into finitely many of the summands. 
May 21 
answered  Different ways of having infinite global dimension 
May 21 
comment 
Different ways of having infinite global dimension
I seem to vaguely recall that by a result of Auslander the global dimension is the sup of the projective dimensions of all cyclic Rmodules. This would imply what you want can't happen if I am recalling correctly 
May 18 
reviewed  No Action Needed Counting ways to Arrange Variable Sized Objects into Fixed Number of Spaces 