Benjamin Steinberg
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 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?