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Apr
5
reviewed Close What is $2^{7!}\bmod{2987}$
Apr
5
reviewed Close If $p,q$ are prime, solve $p^3-q^5=(p+q)^2$.
Mar
31
comment Counter-example to exponential law for locally compact [non-Hausdorff] spaces
@Stefan (Re: last comment) No-no, I want a counter example where X is not Hausdorff (and $Y$ is locally compact).
Mar
30
comment Counter-example to exponential law for locally compact [non-Hausdorff] spaces
@user87690 Right, thank you (if one assumes a strong enough version of local compactness — for non-Hausdorff spaces there are different versions of the definition — one needn't assume that $Y$ is Hausdorff — I've updated the question).
Mar
30
revised Counter-example to exponential law for locally compact [non-Hausdorff] spaces
deleted 123 characters in body
Mar
30
comment Counter-example to exponential law for locally compact [non-Hausdorff] spaces
@johndoe ...And Sierpinski set is, perhaps, a good choice for $Z$ — AFAIR, there is some theorem along the lines 'if the exponential law hold for $Z=\text{Sierpinski}$ it holds for all $Z$'.
Mar
30
comment Counter-example to exponential law for locally compact [non-Hausdorff] spaces
...the idea of taking finite $X$ and $Y$ is quite tempting — because finite topological spaces are locally-compact (and I don't know many example of non-Hausdorff locally-compact spaces). I've tried to play with some examples — but haven't succeeded.
Mar
30
comment Counter-example to exponential law for locally compact [non-Hausdorff] spaces
@johndoe Well, if either $X$, $Y$ or $Z$ is discrete the statement seems to be more or less obviously true. But slightly more generally...
Mar
30
comment Counter-example to exponential law for locally compact [non-Hausdorff] spaces
Related (but not answering the question): @ n-Category Cafe
Mar
30
asked Counter-example to exponential law for locally compact [non-Hausdorff] spaces
Mar
21
comment Combinatorial definition of Hall–Littlewood polynomials (sum over SSYT?)
@IgorMakhlin (И про t-версию Бриона и т.п. мы бы с М.Б. с интересом послушали в какой-то момент.)
Mar
21
comment Combinatorial definition of Hall–Littlewood polynomials (sum over SSYT?)
@IgorMakhlin О, привет. Well, yes and no: there is an explicit description of the $t$-weight $\psi$ in Macdonald's book — but it's complicated and not terribly satisfying. So if you have a better answer, please explain it (here or iRL).
Mar
20
revised Algebraic tricks like componendo dividendo
edited tags
Mar
12
comment Geometric interpretation for sum of fourth powers
Well, yes, $1^k+2^k+...+n^k$ is the value of an Ehrhart polynomial for the 'hybercubic pyramid'. But does this help to compute the sum?
Jan
30
comment Is reduced homology a full functor on connected spaces?
The question is about the category of connected spaces.
Jan
30
comment Is reduced homology a full functor on connected spaces?
Uh? $\tilde H(pt)=0$.
Jan
23
reviewed Close In a group of order 21, every normal subgroup is cyclic
Jan
23
reviewed Close Separable spaces and functions that separate points
Jan
22
comment Curious Binomial Coefficient Identity
it's a (yet another) form of Vandermonde's identity
Jan
20
reviewed Close How to understand the regular cardinal?