共查询到20条相似文献,搜索用时 31 毫秒
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Md. Ali Zinna 《Journal of Pure and Applied Algebra》2019,223(2):783-793
Let R be a commutative Noetherian ring of dimension two with and let . Let P be a projective A-module of rank 2. In this article, we prove that P is cancellative if is cancellative. 相似文献
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Federico Galetto Anthony V. Geramita Yong-Su Shin Adam Van Tuyl 《Journal of Pure and Applied Algebra》2019,223(6):2709-2731
Let I be a homogeneous ideal of . To compare , the m-th symbolic power of I, with , the regular m-th power, we introduce the m-th symbolic defect of I, denoted . Precisely, is the minimal number of generators of the R-module , or equivalently, the minimal number of generators one must add to to make . In this paper, we take the first step towards understanding the symbolic defect by considering the case that I is either the defining ideal of a star configuration or the ideal associated to a finite set of points in . We are specifically interested in identifying ideals I with . 相似文献
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Mi Hee Park 《Journal of Pure and Applied Algebra》2019,223(9):3980-3988
There are many Noetherian-like rings. Among them, we are interested in SFT-rings, piecewise Noetherian rings, and rings with Noetherian prime spectrum. Some of them are stable under polynomial extensions but none of them are stable under power series extensions. We give partial answers to some open questions related with stabilities of such rings. In particular, we show that any mixed extensions over a zero-dimensional SFT ring R are also SFT-rings, and that if R is an SFT-domain such that is integrally closed for each prime ideal P of R, then is an SFT-ring. We also give a direct proof that if R is an SFT Prüfer domain, then is an SFT-ring. Finally, we show that the power series extension over a Prüfer domain R is piecewise Noetherian if and only if R is Noetherian. 相似文献
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Let R be a polynomial ring over a field and I an ideal generated by three forms of degree three. Motivated by Stillman's question, Engheta proved that the projective dimension of is at most 36, although the example with largest projective dimension he constructed has . Based on computational evidence, it had been conjectured that . In the present paper we prove this conjectured sharp bound. 相似文献
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《Journal of Pure and Applied Algebra》2019,223(11):5030-5048
Take positive integers m, n and d. Let Y be an m-fold cyclic cover of ramified over a general hypersurface of degree md. In this paper we study the space of lines in Y and show that it is smooth of dimension if and . When , our result gives a formula on the number of m-contact order lines of X (see Definition 1.2). 相似文献
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Let X be a hyperbolic Riemann surface and let μ be an extremal Beltrami differential on X with . It is proved that, if is a Hamilton sequence of μ, then must be a Hamilton sequence of any extremal Beltrami differential ν contained in . This result proved a conjecture of the first author of this paper in 1996. This result is also a generalization of two known results. 相似文献
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Charles Almeida Aline V. Andrade Rosa M. Miró-Roig 《Journal of Pure and Applied Algebra》2019,223(4):1817-1831
Let be a minimal monomial Togliatti system of forms of degree d. In [4], Mezzetti and Miró-Roig proved that the minimal number of generators of lies in the interval . In this paper, we prove that for and , the integer values in cannot be realized as the number of minimal generators of a minimal monomial Togliatti system. We classify minimal monomial Togliatti systems of forms of degree d with or 3n (i.e. with the minimal number of generators reaching the border of the non-existence interval). Finally, we prove that for , and there exists a minimal monomial Togliatti system of forms of degree d with . 相似文献
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Let be the finite field of order q. Let G be one of the three groups , or and let W be the standard n-dimensional representation of G. For non-negative integers m and d we let denote the representation of G given by the direct sum of m vectors and d covectors. We exhibit a minimal set of homogeneous invariant polynomials such that for all cases except when and or . 相似文献
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Nursel Erey 《Journal of Pure and Applied Algebra》2019,223(7):3071-3080
Let G be a -free graph with edge ideal . We show that has linear resolution for every . Also, we show that every power of the vertex cover ideal of G has linear quotients. As a result, we describe the Castelnuovo–Mumford regularity of powers of in terms of the maximum degree of G. 相似文献
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Let be a Noetherian local ring and M a finitely generated R-module. The invariants and of M were introduced in [3] and [17] in order to measure the non-Cohen–Macaulayness and the non-sequential-Cohen–Macaulayness of M, respectively. Let be the filtration of M such that is the largest submodule of M of dimension less than for all and . In this paper we prove that if , then there exists a constant c such that for all good parameter ideals of M with respect to this filtration. Here is the reducibility index of on M. This is an extension of the main results of [19], [20], [24]. 相似文献
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《Discrete Mathematics》2022,345(7):112866
Let G be a graph with n vertices. A path decomposition of G is a set of edge-disjoint paths containing all the edges of G. Let denote the minimum number of paths needed in a path decomposition of G. Gallai Conjecture asserts that if G is connected, then . If G is allowed to be disconnected, then the upper bound for was obtained by Donald [7], which was improved to independently by Dean and Kouider [6] and Yan [14]. For graphs consisting of vertex-disjoint triangles, is reached and so this bound is tight. If triangles are forbidden in G, then can be derived from the result of Harding and McGuinness [11], where g denotes the girth of G. In this paper, we also focus on triangle-free graphs and prove that , which improves the above result with . 相似文献
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In this paper, we generalize the notion of functional graph. Specifically, given an equation with variables X and Y over a finite field of odd characteristic, we define a digraph by choosing the elements in as vertices and drawing an edge from x to y if and only if . We call this graph as equational graph. In this paper, we study the equational graph when choosing with a polynomial over and λ a non-square element in . We show that if f is a permutation polynomial over , then every connected component of the graph has a Hamiltonian cycle. Moreover, these Hamiltonian cycles can be used to construct balancing binary sequences. By making computations for permutation polynomials f of low degree, it appears that almost all these graphs are strongly connected, and there are many Hamiltonian cycles in such a graph if it is connected. 相似文献
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Abraham Rueda Zoca 《Journal of Mathematical Analysis and Applications》2022,505(1):125447
We study the presence of L-orthogonal elements in connection with Daugavet centers and narrow operators. We prove that if and is a Daugavet center with separable range then, for every non-empty -open subset W of , it follows that contains some L-orthogonal to Y. In the context of narrow operators, we show that if X is separable and is a narrow operator, then given and any non-empty -open subset W of then W contains some L-orthogonal u so that . In the particular case that is separable, we extend the previous result to . Finally, we prove that none of the previous results holds in larger density characters (in particular, a counterexample is shown for under the assumption ). 相似文献
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《Discrete Mathematics》2022,345(12):113079
A set D of vertices of a graph is irredundant if each non-isolated vertex of has a neighbour in that is not adjacent to any other vertex in D. The upper irredundance number is the largest cardinality of an irredundant set of G; an -set is an irredundant set of cardinality .The IR-graph of G has the -sets as vertex set, and sets D and are adjacent if and only if can be obtained from D by exchanging a single vertex of D for an adjacent vertex in . An IR-tree is an IR-graph that is a tree. We characterize IR-trees of diameter 3 by showing that these graphs are precisely the double stars , i.e., trees obtained by joining the central vertices of two disjoint stars . 相似文献
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《Discrete Mathematics》2022,345(12):113083
Let G be a graph, the order of G, the connectivity of G and k a positive integer such that . Then G is said to be k-extendable if it has a matching of size k and every matching of size k extends to a perfect matching of G. A Hamiltonian path of a graph G is a spanning path of G. A bipartite graph G with vertex sets and is defined to be Hamiltonian-laceable if such that and for every pair of vertices and , there exists a Hamiltonian path in G with endpoints p and q, or and for every pair of vertices , there exists a Hamiltonian path in G with endpoints p and q. Let G be a bipartite graph with bipartition . Define to be a maximum integer such that and (1) for each non-empty subset S of X, if , then , and if , then ; and (2) for each non-empty subset S of Y, if , then , and if , then ; and (3) if there is no non-negative integer satisfying (1) and (2).Let G be a bipartite graph with bipartition such that and . In this paper, we show that if , then G is Hamiltonian-laceable; or if , then for every pair of vertices and , there is an -path P in G with . We show some of its corollaries in k-extendable, bipartite graphs and a conjecture in k-extendable graphs. 相似文献