Hypercubes and star graphs are widespread topologies of interconnection networks. The class of hyper-stars was introduced as a new type of interconnection network to compete with both hypercubes and star graphs, and the class of folded hyper-stars is a strengthened variation of hyperstars with additional links to connect nodes with complemented 0/1-strings. Constructing independent spanning tre...

(Received) We study the Weyl closure Cl(L) = K(x)h@iL \ D for an operator L of the rst Weyl algebra D = Khx;@i. We give an algorithm to compute Cl(L) and we describe its initial ideal under the order ltration. Our main application is an algorithm for constructing a Jordan-HH older series for a holonomic D-module and a formula for its length. Using the closure, we also reproduce a result of Strr...

In this article we prove an analogue of Bauer’s theorem from algebraic number theory in the context of hyperbolic systems. 0. Introduction Let φ : X → X be a hyperbolic dynamical system and, for a finite G, let φ̃ : X̃ → X̃ be a G-extension for which φ̃ is also hyperbolic. Given φ we are interested in describing the possibilities for φ̃ in terms of the closed φ-orbits. This is analogous to a classic...

We pursue the study of the computational power of Piecewise Constant Derivative PCD systems started in PCD systems are dynamical systems de ned by a piecewise constant di erential equation and can be considered as computational machines working on a continuous space with a continuous time We prove that the languages recognized by rational PCD systems in dimension d k respectively d k k in nite ...

We construct a canonical free resolution for arbitrary monomial modules and lattice ideals. This includes monomial ideals and defining ideals of toric varieties, and it generalizes our joint results with Irena Peeva for generic ideals [BPS],[PS]. Introduction Given a field k, we consider the Laurent polynomial ring T = k[x 1 , . . . , x ±1 n ] as a module over the polynomial ring S = k[x1, . . ...

We consider the following “field descent problem” for principal ideals I of number fields K. Assume that I is invariant under a Galois automorphism σ of K; decide wether there is a generator g of I with gσ = g, i.e., wether I can be generated by an element of Fix σ. We solve this problem for certain ideals by elementary methods. As a consequence, we are able to exhibit large explicit subgroups ...

One of the unfulfilled aims of the authors of the preceding paper [W. Parry and M. Pollicott. An analogue of Bauer’s theorem for closed orbits of skew products. Ergod. Th. & Dynam. Sys. 28 (2008), 535–546] was to find a dynamical analogue of Artin reciprocity. In this addendum, we present one such version, suggested by work of Sunada. 0. Introduction In algebraic number theory, one of the most ...