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Vladimir Dotsenko's user avatar
Vladimir Dotsenko's user avatar
Vladimir Dotsenko's user avatar
Vladimir Dotsenko
  • Member for 15 years, 1 month
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Reference request: Algebras over monoid objects in a monoidal category
It is certainly mentioned matter-of-factly as completely well known in "Coequalizers in categories of algebras" of Linton (link.springer.com/chapter/10.1007/BFb0083082). One may argue that this is already in "Functorial semantics of algebraic theories" of Lawvere (pnas.org/doi/abs/10.1073/pnas.50.5.869), though of course there it is mentioned (as obvious) for equational algebraic theories only.
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Solving a three-parameter recursive sequence
Can you solve the original recursion in the direction of $\beta$ and $\gamma$ also? Perhaps knowing all of them would help somehow. Or is $\alpha$ somehow special?
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Solving a three-parameter recursive sequence
If one substitutes this in the original recurrence and denotes $g(b,c)=f(0,b,c)$, we get, I believe, $g(b,c)=-(4b+6c-2)(4b+6c-3)g(b-1,c)-8(b+1)g(b+1,c-1)-12(c+1)g(b-2,c+1)$ - perhaps Mathematica can do miracles for this recurrence once again?
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Colloquial catchy statements encoding serious mathematics
@ZachTeitler what do you mean? Clicking on either of the links brings me to the correct PDF file.
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(Conceptual) proof and/or interpretation of a $q$-binomial identity
Dear Neil, I have been telling a lot of people about your argument, and I am informed that one of those conversations was fruitful, and there is an arXiv preprint that proves a much more intricate thing this way: arxiv.org/abs/2409.05605 !
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Real matrix rings and associative hypercomplex numbers
On the other hand, if one is concerned with the whole matrix algebra $M_n(\mathbb{R}$, the answer to the question is rather trivially "yes". Concretely, one can take the basis that consists of all off-diagonal matrix units $E_{ij}$ [which all square to $0$], the identity matrix $I_n$, and the matrices $A_i=\mathrm{diag}(1,1,\ldots,-1,\ldots,-1)$, that is, $i$ copies of $1$ followed by $n-i$ copies of $-1$, for $i=1,\ldots,n-1$ [which all square to $I_n$], since these $n$ diagonal matrices clearly form a basis in the space of all diagonal matrices.
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How do you define the composition of two $\mathbb{S}$-modules?
Well, if you realize this should be an MSE question, it is especially inappropriate to post it on MO.
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Is it known? A sum over lattice parallelograms of area one is equal to $\pi$
I'd say "reference-request" would be a more appropriate tag than "analytic-number-theory", but perhaps I am missing something.
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Fun applications of representations of finite groups
@valle what is your background? it is not easy to give this kind of advice without any context available
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Fun applications of representations of finite groups
@valle this is one of many motivations for representation theory of symmetric groups $S_n$. The subject is vast, but almost every treatment of that theory will have the answer shine through.
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Lie algebra cohomology of the space of vector fields
I am a bit surprised that you take $A/[A,A]$ as coefficients - at least if you want to imitate the divergence statement, since the conceptually meaningful divergence of a derivation takes values in the commutator quotient of the universal enveloping algebra, not in the commutator quotient of the algebra itself.
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Pairing on a Koszul dual pair
That vague statement does not really promise a pairing, it promises some analogue of a pairing. I do not think there is anything reasonable to expect. Already in the classical case of symmetric/exterior algebras, what would such a pairing be, in your opinion? Symmetric powers do not really pair with exterior powers.
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What's the explicit value of this determinant
Perhaps you can clarify what you mean by "formula". Expanding a determinant using $n!$ terms is also a formula. Already for $n=3$ the corresponding polynomial is irreducible, as I just checked, so no cute factorization to be expected.
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counting patterns in a word
I am confused that you do not mention 134 at all, which is also 3-step increasing. Can you please make your question sufficiently precise?
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