If the arity of a maximal irreducible retractof an n-quasigroup M belongs to {3, . . . , n − 3}, then M is reducible.

We discuss an algorithm computing the push-forward to projective space of several classes associated to a (possibly singular, reducible, nonreduced) projective scheme. For example, the algorithm yields the topological Euler characteristic of the support of a projective scheme S, given the homogeneous ideal of S. The algorithm has been implemented in Macaulay2.

Cofiniteness of the generalized local cohomology modules $H^{i}_{mathfrak{a}}(M,N)$ of two $R$-modules $M$ and $N$ with respect to an ideal $mathfrak{a}$ is studied for some $i^{,}s$ witha specified property. Furthermore, Artinianness of $H^{j}_{mathfrak{b}_{0}}(H_{mathfrak{a}}^{i}(M,N))$ is investigated by using the above result, in certain graded situations, where $mathfrak{b}_{0}$ is an idea...

Let f : X ! IR f+1g be a lower semicontinuous function on a Banach space X. We show that f is quasiconvex if and only if its Clarke subdiierential @f is quasimonotone. As an immediate consequence, we get that f is convex if and only if @f is monotone.

We establish the following result: if the graph of a lower semicontinuous real-extendedvalued function f : Rn → R ∪ {+∞} admits a Whitney stratification (so in particular if f is a semialgebraic function), then the norm of the gradient of f at x ∈ dom f relative to the stratum containing x bounds from below all norms of Clarke subgradients of f at x. As a consequence, we obtain a Morse-Sard typ...

We establish necessary and sufficient conditions for a quadratic polynomial to be irreducible in the ring Z[[x]] of formal power series with integer coefficients. For n,m ≥ 1 and p prime, we show that p+pβx+αx is reducible in Z[[x]] if and only if it is reducible in Zp[x], the ring of polynomials over the p-adic integers.

In this paper, we attempt to investigate the connection between various types of ideals (for examples $(m, n)$-ideal, bi-ideal, interior ideal, quasi ideal, prime ideal and maximal ideal) of an ordered semigroup $(S,cdot ,leq)$ and the correspond hyperideals of its EL-hyperstructure $(S,*)$ (if exists). Moreover, we construct the class of EL-$Gamma$-semihypergroup associated to a partially orde...

By means of a result on the semi-global C solution, we establish the exact boundary controllability for the reducible quasilinear hyperbolic system if the C norm of initial data and final state is small enough. Mathematics Subject Classification. 35L50, 49J20, 49N50. Received: October 28, 1999. Revised: November 22, 1999.

This paper studies one of the problems concerning Dehn fillings producing reducible or toroidal 3-manifolds. Let M be an orientable, irreducible, atoroidal, anannular 3-manifold with T as a torus boundary component. Let γ be an essential simple loop on T . Denote by M(γ) the manifold obtained by Dehn filling along the curve γ, i.e. M(γ) = M ∪φ J , where J is a solid torus, and φ : T ∼= ∂J is a ...