Cost register automata (CRA) and its subclass, copyless CRA, were recently proposed by Alur et al. as a new model for computing functions over strings. We study structural properties, expressiveness, and closure properties of copyless CRA. We show that copyless CRA are strictly less expressive than weighted automata and are not closed under reverse operation. To find a better class we impose re...

We show that the class of groups with k-multiple context free word problem is closed under amalgamated free products over finite subgroups. We also show that the intersection of two context free languages need not be multiple context free.

Context-free language theory is a well-established area of mathematics, relevant to computer science foundations and technology. This paper presents the preliminary results of an ongoing formalization project using context-free grammars and the Coq proof assistant. The results obtained so far include the representation of context-free grammars, the description of algorithms for some operations ...

We study various properties of closed relativistic strings. In particular, we characterize their closure under uniform convergence, extending a previous result by Y. Brenier on graph-like unbounded strings, and we discuss some related examples. Then we study the collapsing profile of convex planar strings which start with zero initial velocity, and we obtain a result analogous to the well-known...

We show that if a complexity class C is closed downward under polynomialtime majority truth-table reductions (≤pmtt), then practically every other “polynomial” closure property it enjoys is inherited by the corresponding bounded 2-sided error class BP[C]. For instance, the Arthur-Merlin game class AM [Bab85] enjoys practically every closure property of NP. Our main lemma shows that for any rela...

Separations, Collapses, and Closure Properties Holger Spakowski1?, Mayur Thakur2??, and Rahul Tripathi2? ? ? 1 Institut für Informatik, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany. [email protected] 2 Department of Computer Science, University of Rochester, Rochester, NY 14627, USA. fthakur,[email protected] Abstract. We study the complexity of quantum c...

Closed semirings are algebraic structures that provide a unified approach to a number of seemingly unrelated problems of computer science and operations research. For example, semirings can be used to describe the algebra related to regular expressions, graph-theoretical path problems, and linear equations. We present a new axiomatic formulation of semirings. We introduce the concept of elimina...

We compare the general notion of regularity deened in FM02] for languages of pomsets (with autoconcurrency) with the deenability in MSOL of such languages. We show that for the class of bounded languages, deenability implies regularity. It shows that for bounded languages of pomsets without autoconcurrency, the recognisability by Asynchronous Cellular Automata as deened in DGK00] implies regula...

In concurrency theory, there are several examples where the interleaved model of concurrency can distinguish between execution sequences which are not signiicantly diierent. One such example is sequences that diier from each other by stuttering, i. e., the number of times a state can adjacently repeat. Another example is executions that diier only by the ordering of independently executed event...

1. Let A be a fixed compact Hausdorff space, C the Banach lattice of continuous real functions on X, L its dual, and M its second dual. The closure of C in M under the weak topology wiM, L) determined by L is, as is well known, M itself. In fact, the closure of C under the Mackey topology riM, L) is M itself, by the Grothendieck Theorem. A deeper property is that this relationship between C and...