# 2-Nested Simulation Is Not Finitely Equationally Axiomatizable

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## Abstract

2-nested simulation was introduced by Groote and Vaan- drager [10] as the coarsest equivalence included in completed trace equiv- alence for which the tyft/tyxt format is a congruence format. In the linear time-branching time spectrum of van Glabbeek [8], 2-nested simulation is one of the few equivalences for which no finite equational axiomati- zation is presented. In this paper we prove that such an axiomatization does not exist for 2-nested simulation.

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