scholarly journals Pseudo-solutions of word equations

2020 ◽  
Vol 814 ◽  
pp. 13-18
Author(s):  
Štěpán Holub
Keyword(s):  
Word Equations

Studying Word Equations by a Method of Weighted Frequencies

2018 ◽  
Vol 162 (2-3) ◽  
pp. 223-235 ◽  
Author(s):  
Aleksi Saarela
Keyword(s):  
Word Equations

scholarly journals Unification Modulo Lists with Reverse Relation with Certain Word Equations

2019 ◽  
pp. 1-17
Author(s):  
Siva Anantharaman ◽  
Peter Hibbs ◽  
Paliath Narendran ◽  
Michael Rusinowitch
Keyword(s):  
Word Equations

scholarly journals Solutions to twisted word equations and equations in virtually free groups

2020 ◽  
Vol 30 (04) ◽  
pp. 731-819
Author(s):  
Volker Diekert ◽  
Murray Elder
Keyword(s):  
Free Groups ◽  
Expressive Power ◽  
Solution Set ◽  
Complexity Bound ◽  
Free Monoids ◽  
Word Equation ◽  
All Solutions ◽  
Standard Normal ◽  
Word Equations ◽  
Solving Equations

It is well known that the problem solving equations in virtually free groups can be reduced to the problem of solving twisted word equations with regular constraints over free monoids with involution. In this paper, we prove that the set of all solutions of a twisted word equation is an EDT0L language whose specification can be computed in PSPACE . Within the same complexity bound we can decide whether the solution set is empty, finite, or infinite. In the second part of the paper we apply the results for twisted equations to obtain in PSPACE an EDT0L description of the solution set of equations with rational constraints for finitely generated virtually free groups in standard normal forms with respect to a natural set of generators. If the rational constraints are given by a homomorphism into a fixed (or “small enough”) finite monoid, then our algorithms can be implemented in [Formula: see text], that is, in quasi-quadratic nondeterministic space. Our results generalize the work by Lohrey and Sénizergues (ICALP 2006) and Dahmani and Guirardel (J. of Topology 2010) with respect to both complexity and expressive power. Neither paper gave any concrete complexity bound and the results in these papers are stated for subsets of solutions only, whereas our results concern all solutions.

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