Operads, quasiorders, and regular languages
  We generalize the construction of multitildes in the aim to provide multitilde operators for regular languages. We show that the underliying algebraic structure involves the action of some operads. An operad is an algebraic structure that mimics the composition of the functions. The involved operads are described in terms of combinatorial objects. These operads are obtained from more primitive objects, namely precompositions, whose algebraic counter-parts are investigated. One of these operads acts faithfully on languages in the sense that two different operators act in two different ways. 
Samuele Giraudo, Jean-Gabriel Luque, Ludovic Mignot and Florent Nicart
cs.FL math.CO