The University of Southampton
University of Southampton Institutional Repository

# An Infinite Automaton Characterization of Double Exponential Time

Record type: Conference or Workshop Item (Paper)

Infinite-state automata are a new invention: they are automata that have an infinite number of states represented by words, transitions defined using rewriting, and with sets of initial and final states. Infinite-state automata have gained recent interest due to a remarkable result by Morvan and Stirling, which shows that automata with transitions defined using rational rewriting precisely capture context-sensitive (NLinSpace) languages. In this paper, we show that infinite automata defined using a form of multi-stack rewriting precisely defines double exponential time (more precisely, 2ETime, the class of problems solvable in 22O(n) time). The salient aspect of this characterization is that the automata have no ostensible limits on time nor space, and neither direction of containment with respect to 2ETime is obvious. In this sense, the result captures the complexity class qualitatively, by restricting the power of rewriting.

PDF fulltext.pdf - Version of Record

## Citation

Torre, Salvatore La, Madhusudan, P. and Parlato, Gennaro (2008) An Infinite Automaton Characterization of Double Exponential Time At CSL, Italy. 16 - 19 Sep 2008. , pp. 33-48.

Published date: 2008
Additional Information: Event Dates: September 16-19, 2008
Venue - Dates: CSL, Italy, 2008-09-16 - 2008-09-19
Organisations: Electronic & Software Systems

## Identifiers

Local EPrints ID: 272460
URI: http://eprints.soton.ac.uk/id/eprint/272460
ISBN: 978-3-540-87530-7
PURE UUID: 3c2db79d-3360-41b5-aa4d-8646b01c9230

## Catalogue record

Date deposited: 13 Jun 2011 14:06

## Contributors

Author: Salvatore La Torre
Author: Gennaro Parlato