In this paper we consider Z-actions, d ≥ 1, by automorphisms of compact connected abelian groups which contain at least one expansive automorphism (such actions are called algebraic Z-actions of expansive rank one). If α is such a Z-action on an infinite compact connected abelian group X, then every expansive element α of this action has a dense group ∆αn(X) of homoclinic points. For different ...

We look at the relationships between class numbers of quadratic structures (orders and fields) and the solutions of exponential Diophantine equations. We conclude with necessary and sufficient conditions for a class group to have an element of a given order. 1. Notation and Preliminaries If D is a squarefree integer, then its discriminant is given by ( ) ( )    ≡ ≡/ = ∆ . 4 mod 1 if , 4 mod ...

We improve the zeroizing attack on the multilinear map of Garg, Gentry and Halevi (GGH). Our algorithm can solve the Graded Decisional Diffie-Hellman (GDDH) problem on the GGH scheme when the dimension n of the ideal lattice Z[X]/(X+1) is O(κλ) as suggested for the κ-linear GGH scheme. The zeroizing attack is to recover a basis of an ideal generated by a secret element g ∈ Z[X]/(X + 1) from the...

In this paper, we give two applications of the theory of multiplier ideals to vector bundles over complex projective manifolds, generalizing to higher rank results already established for line bundles. The first addresses the existence of sections of (suitable twists) of symmetric powers of a very ample vector bundle, vanishing on a given subvariety. The second is a vanishing theorem of Gri‰ths...

The security of many efficient cryptographic constructions, e.g. collision-resistant hash functions, digital signatures, identification schemes, and more recently public-key encryption has been proven assuming the hardness of worst-case computational problems in ideal lattices. These lattices correspond to ideals in the ring Z[ζ], where ζ is some fixed algebraic integer. Under the assumption th...

Let R = ⊕ d∈N0 Rd be a positively graded commutative Noetherian ring which is standard in the sense that R = R0[R1], and set R+ := ⊕ d∈N Rd, the irrelevant ideal of R. (Here, N0 and N denote the set of non-negative and positive integers respectively; Z will denote the set of all integers.) Let M = ⊕ d∈Z Md be a non-zero finitely generated graded R-module. This paper is concerned with the behavi...

Let R be a ring with center Z and I a nonzero ideal of R. An additive mapping F : R → R is called a generalized derivation of R if there exists a derivation d : R → R such that F xy F x y xd y for all x, y ∈ R. In the present paper, we prove that if F x, y ± x, y for all x, y ∈ I or F x ◦ y ± x ◦ y for all x, y ∈ I, then the semiprime ring R must contains a nonzero central ideal, provided d I /...

Suppose X is a nonsingular arithmetically Cohen-Macaulay projective scheme, Z a nonsingular closed subscheme of X, and˜I the ideal sheaf of Z in X. Let˜X be the blowup of X along˜I, E0 the pull-back of a general hyperplane in X, and E the exceptional divisor. In this paper, we study projective embeddings of˜X given by the divisors De,t = tE0 − eE. We give explicit values of d and δ such that fo...

We generalize the notions of F-regular and F-pure rings to those for a pair (R, a) of a ring R and an ideal a ⊂ R with real exponent t > 0, and investigate those properties. Those “F-singularities of pairs” correspond to singularities of pairs of arbitrary codimension in birational geometry. Via this correspondence, we prove Inversion of Adjunction of arbitrary codimension, which states that fo...

Let p be a prime number and let K be a finite extension of Qp. Let R be the valuation ring of K, P the maximal ideal of R, and K̄ = R/P the residue field of K. Let q denote the cardinality of K̄, so K̄ ≃ Fq. For z in K, let ord z denote the valuation of z, and set |z| = q . Let f be a non constant element of K[x1, . . . , xm]. The p-adic Igusa local zeta function Z(s) associated to f (relative to ...