Reputation
Top tag
Next privilege 20,000 Rep.
Access 'trusted user' tools
Badges
2 43 101
Impact
~422k people reached

Apr
15
answered What is known about semigroups that are generated by (cyclic) subgroups?
Apr
14
comment What is the combinatorial data classifying non-normal affine toric varieties?
Is this very different than saying it reduces to looking at monoids or do they have combinatorial descriptions?
Apr
12
comment Find a square, stochastic matrix (w/ non-neg entries) of odd size, not a permutation matrix, with an eigenvalue other than 1 on the unit circle
Take a permutation matrix corresponding to an n-cycle
Apr
10
comment Reference request: exponential growth rates of subword-closed languages are integers
Yes shuffle. IPhones...
Apr
8
comment What word can I use for a poset with equivalences
I agree. I'm just pointing out both are in use.
Apr
8
comment What word can I use for a poset with equivalences
Some people also say quasiorder.
Apr
8
comment Reference request: exponential growth rates of subword-closed languages are integers
You might try the cs stackexchange. The buzzwords you want are shuttle ideal and piecewise testable
Apr
8
comment Reference request: exponential growth rates of subword-closed languages are integers
As the OP points out this is a well quasi order by Higman.
Apr
8
comment Reference request: exponential growth rates of subword-closed languages are integers
@IlyaBogdanov, subword in the op sense means deleting letters so subsequence if you view words as a sequence of letters. So bab is a subword if all $ba^{k+1}b$ and is the unique minimal forbidden subword.
Apr
6
revised How many monoids with $n$ arrows exist?
added 39 characters in body
Apr
6
answered How many monoids with $n$ arrows exist?
Apr
6
comment How many monoids with $n$ arrows exist?
You can build lots of semigroups by taking one element to be a zero (absorbing) and make all products of length 3 zero to get associativity. Conjecurally almost all semigroups of order n have this form
Apr
6
comment How many monoids with $n$ arrows exist?
I believe the record is now semigroups of order 12.
Apr
6
comment How many monoids with $n$ arrows exist?
There are billions of order 8 for semigroups do order 9 for monoids.
Apr
6
comment Generic set that is a proper subgroup
you want intersection in the numerator
Apr
5
awarded  gr.group-theory
Apr
4
awarded  Nice Answer
Apr
4
answered Cayley graphs of $A_n.$
Apr
3
comment Cyclic decomposition of an infinitely generated module
Q (the rationals) cannot be written as a direct sum of cyclic Z-modules.
Apr
1
comment Monoid prime ideals and prime congruences
What is a prime congruence?