Symbolic powers of ideals are studied in the combinatorial context of monomial ideals. When the ideals are generated by quadratic squarefree monomials, the generators of the symbolic powers are obstructions to vertex covering in the associated graph and its blow-ups. As a result, perfect graphs play an important role in the theory, dual to the role played by perfect graphs in the theory of seca...

We study the class of analytic ideals on the set of natural numbers ordered under Tukey reducibility. We consider mostly structural issues: characterization of ideals which are Tukey above w”‘, extremal elements for the class of analytic P-ideals, etc. We prove that this class is very rich by embedding into it (P(N), (I,). We also study ideals associated to classical Banach spaces and ideals of...

Abstract. The interval-valued prime fuzzy ideals (in brevity, the iv. prime fuzzy ideals) of a semigroup have been recently studied by Kar, Sarkar and Shum [18]. As a continued study of i-v fuzzy ideals, we are going to investigate the properties of i-v fuzzy quasi-ideal and i-v fuzzy bi-ideal of a semiring and then we characterize the regularity and intra-regularity of a semiring in terms of t...

We compute the initial ideals, with respect to certain conveniently chosen term orders, of ideals of tangent cones at torus fixed points to Schubert varieties in orthogonal Grassmannians. The initial ideals turn out to be square-free monomial ideals and therefore StanleyReisner face rings of simplicial complexes. We describe these complexes. The maximal faces of these complexes encode certain s...

The notions of N-subalgebras and N-closed ideals in BCH-algebras are introduced, and the relation between N-subalgebras and N-closed ideals is considered. Characterizations of Nsubalgebras andN-closed ideals are provided. Using special subsets,N-subalgebras andN-closed ideals are constructed. A condition for anN-subalgebra to be anN-closed ideal is discussed. Given an N-structure, the greatestN...

Abstract. In this paper, intuitionistic fuzzy h-bi-ideals and intuitionistic fuzzy hquasi-ideals of hemirings are studied and some related properties are investigated. We characterize fully idempotent hemirings by the properties of their intuitionistic fuzzy h-ideals.We also characterize h-hemiregularity, h-intra-hemiregularity and h-quasi-hemiregularity in hemirings by the properties of their ...

We generalize the differential dimension polynomial from prime differential ideals to characterizable differential ideals. Its computation is algorithmic, its degree and leading coefficient remain differential birational invariants, and it decides equality of characterizable differential ideals contained in each other.

Squarefree monomial ideals arising from finite meet-semilattices and their free resolutions are studied. For the squarefree monomial ideals corresponding to poset ideals in a distributive lattice the Alexander dual is computed.

Right ternary near-rings (RTNR) are generalization of their binary counterpart and fuzzy soft sets are generalization of soft sets which are parameterized family of subsets of a universal set. In this paper fuzzy soft Nsubgroups, quasi-ideals and bi-ideals over a right ternary near-ring N are defined. The substructures N-subgroups, quasi-ideals and bi-ideals of an RTNR are characterized in term...

In a commutative f-ring, an 1-ideal I is called pseudoprime if ab = 0 implies a E I or b E I, and is called square dominated if for every a E I, lal < x2 for some x E A such that x2 E I. Several characterizations of pseudoprime 1-ideals are given in the class of commutative semiprime frings in which minimal prime 1-ideals are square dominated. It is shown that the hypothesis imposed on the f-ri...