Results 1 - 10 of 1,892

UNDECIDABLE PROBLEMS

by Marcel Jackson, Mikhail V. Volkov, For Completely -simple Semigroups, Marcel Jackson, Mikhail Volkov
"... semigroups ..."
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semigroups

Undecidable Problems in Unreliable Computations

by Richard Mayr - THEORETICAL COMPUTER SCIENCE , 2000
"... Lossy counter machines are defined as Minsky n-counter machines where the values in the counters can spontaneously decrease at any time. While termination is decidable for lossy counter machines, structural termination (termination for every input) is undecidable. This undecidability result has f ..."
Abstract - Cited by 59 (3 self) - Add to MetaCart
far reaching consequences. Lossy counter machines can be used as a general tool to prove the undecidability of many problems, for example (1) The verification of systems that model communication through unreliable channels (e.g. model checking lossy fifo-channel systems and lossy vector addition

AN UNDECIDABLE PROBLEM FOR REGULAR EQUATIONS

by unknown authors
"... This is a continuation of our note [4]. We deal with two kinds of special equa-tions: normal and regular (see [4]). Our aim is to point an undecidable problem on regular (normal) equations. An extended version is submitted to Algebra Universalis. Preliminaries Our nomenclature and notation is basica ..."
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This is a continuation of our note [4]. We deal with two kinds of special equa-tions: normal and regular (see [4]). Our aim is to point an undecidable problem on regular (normal) equations. An extended version is submitted to Algebra Universalis. Preliminaries Our nomenclature and notation

UNDECIDABLE PROBLEMS: A SAMPLER

by Bjorn Poonen , 2012
"... After discussing two senses in which the notion of undecidability is used, we present a survey of undecidable decision problems arising in various branches of mathematics. ..."
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After discussing two senses in which the notion of undecidability is used, we present a survey of undecidable decision problems arising in various branches of mathematics.

Decidable and Undecidable Problems in Matrix Theory

by Vesa Halava , 1997
"... This work is a survey on decidable and undecidable problems in matrix theory. The problems studied are simply formulated, however most of them are undecidable. The method to prove undecidabilities is the one found by Paterson [Pat] in 1970 to prove that the mortality of finitely generated matrix mon ..."
Abstract - Cited by 8 (2 self) - Add to MetaCart
This work is a survey on decidable and undecidable problems in matrix theory. The problems studied are simply formulated, however most of them are undecidable. The method to prove undecidabilities is the one found by Paterson [Pat] in 1970 to prove that the mortality of finitely generated matrix

HIGHLY UNDECIDABLE PROBLEMS FOR INFINITE COMPUTATIONS

by Olivier Finkel - THEORETICAL INFORMATICS AND APPLICATIONS , 2009
"... We show that many classical decision problems about 1-counter ω-languages, context free ω-languages, or infinitary rational relations, are Π 1 2-complete, hence located at the second level of the analytical hierarchy, and “highly undecidable”. In particular, the universality problem, the inclusion ..."
Abstract - Cited by 10 (8 self) - Add to MetaCart
We show that many classical decision problems about 1-counter ω-languages, context free ω-languages, or infinitary rational relations, are Π 1 2-complete, hence located at the second level of the analytical hierarchy, and “highly undecidable”. In particular, the universality problem, the inclusion

Undecidable Problems of Decentralized Observation and Control

by Stavros Tripakis , 2001
"... We introduce a new notion of decentralized observability for discrete-event systems, which we call joint observability. We prove that checking joint observability of a regular language w.r.t. one observer is decidable, whereas for two (or more) observers the problem becomes undecidable. Based on thi ..."
Abstract - Cited by 52 (4 self) - Add to MetaCart
We introduce a new notion of decentralized observability for discrete-event systems, which we call joint observability. We prove that checking joint observability of a regular language w.r.t. one observer is decidable, whereas for two (or more) observers the problem becomes undecidable. Based

Undecidable problems about timed automata

by Olivier Finkel - IN PROCEEDINGS OF THE 4TH INTERNATIONAL CONFERENCE ON FORMAL MODELING AND ANALYSIS OF TIMED SYSTEMS, FORMATS 2006 , 2006
"... We solve some decision problems for timed automata which were raised by S. Tripakis in [Tri04] and by E. Asarin in [Asa04]. In particular, we show that one cannot decide whether a given timed automaton is determinizable or whether the complement of a timed regular language is timed regular. We show ..."
Abstract - Cited by 13 (2 self) - Add to MetaCart
show that the problem of the minimization of the number of clocks of a timed automaton is undecidable. It is also undecidable whether the shuffle of two timed regular languages is timed regular. We show that in the case of timed Büchi automata accepting infinite timed words some of these problems are Π

Undecidable Problems of Decentralized Observation and Control

by unknown authors
"... We introduce a new notion of decentralized observability for discrete-event systems, which we call joint observability. We prove that checking joint observability of a regular language w.r.t. one observer is decidable, whereas for two (or more) observers the problem becomes undecidable. Based on thi ..."
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We introduce a new notion of decentralized observability for discrete-event systems, which we call joint observability. We prove that checking joint observability of a regular language w.r.t. one observer is decidable, whereas for two (or more) observers the problem becomes undecidable. Based

Undecidable problems concerning densities of languages

by Jakub Kozik
"... In this paper we prove that the question whether a language presented by a context free grammar has density, is undecidable. Moreover we show that there is no algorithm which, given two unambiguous context free grammars on input, decides whether the language defined by the first grammar has a relati ..."
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relative density in the language defined by the second one. Our techniques can be extended to show that this problem is undecidable even for languages given by grammars from LL(k) (for sufficiently large fixed k ∈ N).
Results 1 - 10 of 1,892