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Mathematics -- Commutative Algebra (math.AC) updates on the e-print archive

Published: 2017-09-19T20:30:00-05:00


On Bergeron's positivity problem for $q$-binomial coefficients. (arXiv:1709.06187v1 [math.CO])

F. Bergeron recently asked the intriguing question whether $\binom{b+c}{b}_q -\binom{a+d}{d}_q$ has nonnegative coefficients as a polynomial in $q$, whenever $a,b,c,d$ are positive integers, $a$ is the smallest, and $ad=bc$. We conjecture that, in fact, this polynomial is also always unimodal, and combinatorially show our conjecture for $a\le 3$ and any $b,c\ge 4$. The main ingredient will be a novel (and rather technical) application of Zeilberger's KOH theorem.

Properties of Extended Robba Rings. (arXiv:1709.06221v1 [math.NT])

We extend the analogy between the extended Robba rings of p-adic Hodge theory and the one-dimensional affinoid algebras of rigid analytic geometry, proving some fundamental properties that are well known in the latter case. In particular, we show that these rings are regular and excellent. The extended Robba rings are of interest as they are used to build the Fargues-Fontaine curve.

On asymptotic depth of integral closure filtration and an application. (arXiv:1709.06244v1 [math.AC])

Let $(A,\mathfrak{m})$ be an analytically unramified formally equidimensional Noetherian local ring with $\ depth \ A \geq 2$. Let $I$ be an $\mathfrak{m}$-primary ideal and set $I^*$ to be the integral closure of $I$. Set $G^*(I) = \bigoplus_{n\geq 0} (I^n)^*/(I^{n+1})^*$ be the associated graded ring of the integral closure filtration of $I$. We prove that $\ depth \ G^*(I^n) \geq 2$ for all $n \gg 0$. As an application we prove that if $A$ is also an excellent normal domain containing an algebraically closed field isomorphic to $A/\m$ then there exists $s_0$ such that for all $s \geq s_0$ and $J$ is an integrally closed ideal \emph{strictly} containing $(\mathfrak{m}^s)^*$ then we have a strict inequality $\mu(J) < \mu((\mathfrak{m}^s)^*)$ (here $\mu(J)$ is the number of minimal generators of $J$).

Asymptotic Associate Primes. (arXiv:1709.06253v1 [math.AC])

We investigate three cases regarding asymptotic associate primes. First, assume $ (A,\mathfrak{m}) $ is a Cohen-Macaulay (CM), non-regular local ring, and $ M = {\rm Syz}^A_1(L) $ for some maximal CM $ A $-module $ L $ which is free on the punctured spectrum. Let $ I $ be a normal ideal. In this case, we examine when $ \mathfrak{m} \notin {\rm Ass}(M/I^nM) $ for all $ n \gg 0 $. We give sufficient evidence to show that this occurs rarely. Next, assume that $ (A,\mathfrak{m}) $ is Gorenstein, non-regular isolated singularity, and $ M $ is a CM $ A $-module with ${\rm projdim}_A(M) = \infty $ and $ {\rm dim}(M) = {\rm dim}(A) -1 $. Let $ I $ be a normal ideal with analytic spread $ l(I) < {\rm dim}(A) $. In this case, we investigate when $\mathfrak{m} \notin {\rm Ass} {\rm Tor}^A_1(M, A/I^n)$ for all $n \gg 0$. We give sufficient evidence to show that this also occurs rarely. Finally, suppose $ A $ is a local complete intersection ring. For finitely generated $ A $-modules $ M $ and $ N $, we show that if $ {\rm Tor}_i^A(M, N) \neq 0 $ for some $ i > {\rm dim}(A) $, then there exists a non-empty finite subset $ \mathcal{A} $ of $ {\rm Spec}(A) $ such that for every $ \mathfrak{p} \in \mathcal{A} $, at least one of the following holds true: (i) $ \mathfrak{p} \in {\rm Ass}\left( {\rm Tor}_{2i}^A(M, N) \right) $ for all $ i \gg 0 $; (ii) $ \mathfrak{p} \in {\rm Ass}\left( {\rm Tor}_{2i+1}^A(M, N) \right) $ for all $ i \gg 0 $. We also analyze the asymptotic behaviour of ${\rm Tor}^A_i(M, A/I^n)$ for $i,n \gg 0$ in the case when $I$ is principal or $I$ has a principal reduction generated by a regular element.

Riesz space-valued states on pseudo MV-algebras. (arXiv:1709.06502v1 [math.AC])

We introduce Riesz space-valued states, called $(R,1_R)$-states, on a pseudo MV-algebra, where $R$ is a Riesz space with a fixed strong unit $1_R$. Pseudo MV-algebras are a non-commutative generalization of MV-algebras. Such a Riesz space-valued state is a generalization of usual states on MV-algebras. Any $(R,1_R)$-state is an additive mapping preserving a partial addition in pseudo MV-algebras. Besides we introduce $(R,1_R)$-state-morphisms and extremal $(R,1_R)$-states, and we study relations between them. We study metrical completion of unital $\ell$-groups with respect to an $(R,1_R)$-state. If the unital Riesz space is Dedekind complete, we study when the space of $(R,1_R)$-states is a Choquet simplex or even a Bauer simplex.

Positivity of divisors on blown-up projective spaces, II. (arXiv:1709.05012v2 [math.AG] UPDATED)

We construct log resolutions of pairs on the blow-up of the projective space in an arbitrary number of general points and we discuss the semi-ampleness of the strict transforms. As an application we prove that the abundance conjecture holds for an infinite family of such pairs. For $n+2$ points, these strict transforms are F-nef divisors on the moduli space $\overline{\mathcal{M}}_{0,n+3}$ in a Kapranov's model: we show that all of them are nef.