### ${\aleph}_{1}$-категоричные коммутативные кольца

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Let $R$ be a commutative ring with nonzero identity, let $\mathcal{I}\left(\mathcal{R}\right)$ be the set of all ideals of $R$ and $\delta :\mathcal{I}\left(\mathcal{R}\right)\to \mathcal{I}\left(\mathcal{R}\right)$ an expansion of ideals of $R$ defined by $I\mapsto \delta \left(I\right)$. We introduce the concept of $(\delta ,2)$-primary ideals in commutative rings. A proper ideal $I$ of $R$ is called a $(\delta ,2)$-primary ideal if whenever $a,b\in R$ and $ab\in I$, then ${a}^{2}\in I$ or ${b}^{2}\in \delta \left(I\right)$. Our purpose is to extend the concept of $2$-ideals to $(\delta ,2)$-primary ideals of commutative rings. Then we investigate the basic properties of $(\delta ,2)$-primary ideals and also discuss the relations among $(\delta ,2)$-primary, $\delta $-primary and...

The relative cohomology ${\mathrm{H}}_{\mathrm{diff}}^{1}(\mathbb{K}\left(1\right|3),\mathrm{\U0001d52c\U0001d530\U0001d52d}(2,3);{\mathcal{D}}_{\lambda ,\mu}\left({S}^{1|3}\right))$ of the contact Lie superalgebra $\mathbb{K}\left(1\right|3)$ with coefficients in the space of differential operators ${\mathcal{D}}_{\lambda ,\mu}\left({S}^{1|3}\right)$ acting on tensor densities on ${S}^{1|3}$, is calculated in N. Ben Fraj, I. Laraied, S. Omri (2013) and the generating $1$-cocycles are expressed in terms of the infinitesimal super-Schwarzian derivative $1$-cocycle $s\left({X}_{f}\right)={D}_{1}{D}_{2}{D}_{3}\left(f\right){\alpha}_{3}^{1/2}$, ${X}_{f}\in \mathbb{K}\left(1\right|3)$ which is invariant with respect to the conformal subsuperalgebra $\mathrm{\U0001d52c\U0001d530\U0001d52d}(2,3)$ of $\mathbb{K}\left(1\right|3)$. In this work we study the supergroup case. We give an explicit construction of $1$-cocycles of the group...

We study 2-frieze patterns generalizing that of the classical Coxeter-Conway frieze patterns. The geometric realization of this space is the space of $n$-gons (in the projective plane and in 3-dimensional vector space) which is a close relative of the moduli space of genus $0$ curves with $n$ marked points. We show that the space of 2-frieze patterns is a cluster manifold and study its algebraic and arithmetic properties.

R. Hartshorne and A. Hirschowitz proved that a generic collection of lines on ℙn, n≥3, has bipolynomial Hilbert function. We extend this result to a specialization of the collection of generic lines, by considering a union of lines and 3-dimensional sundials (i.e., a union of schemes obtained by degenerating pairs of skew lines).

Let A be a commutative unital Fréchet algebra, i.e. a completely metrizable topological algebra. Our main result states that all ideals in A are closed if and only if A is a noetherian algebra

We prove that a real or complex F-algebra has all left and right ideals closed if and only if it is noetherian.

It is proved that a Marot ring is a Krull ring if and only if its monoid of regular elements is a Krull monoid.

Let K be a unique factorization domain of characteristic p > 0, and let f ∈ K[x₁,...,xₙ] be a polynomial not lying in $K[x{\u2081}^{p},...,x{\u2099}^{p}]$. We prove that $K[x{\u2081}^{p},...,x{\u2099}^{p},f]$ is the ring of constants of a K-derivation of K[x₁,...,xₙ] if and only if all the partial derivatives of f are relatively prime. The proof is based on a generalization of Freudenburg’s lemma to the case of polynomials over a unique factorization domain of arbitrary characteristic.

Consider an experiment with d+1 possible outcomes, d of which occur with probabilities $x\u2081,...,{x}_{d}$. If we consider a large number of independent occurrences of this experiment, the probability of any event in the resulting space is a polynomial in $x\u2081,...,{x}_{d}$. We characterize those polynomials which arise as the probability of such an event. We use this to characterize those x⃗ for which the measure resulting from an infinite sequence of such trials is good in the sense of Akin.