A generalized monoid of infinite words: asymptotic prefix-suffix quotients and algebraic structure

Abstract

A generalized monoid of words tilde{Sigma}* is constructed as the quotient of moderate nets of finite words by an asymptotic equivalence relation based on a bidirectional prefix-suffix metric. The main algebraic result is that this quotient is a monoid containing Sigma* faithfully, with a reversal involution, a natural divisibility preorder, failure of cancellation, and nontrivial idempotents. The construction is designed so that any functional depending only on a logarithmic prefix descends to the quotient, yielding a well-defined action of logarithmic-prefix functionals. Finite scalar values arise only after applying an additional renormalization functional, which depends on the chosen mould and window. With respect to the fixed truncation injection, the monoid strictly enlarges the classical set Sigma^{infty}: an explicit oscillating net is exhibited that has no limit in the Cantor space but defines a genuine element of tilde{Sigma}* not coming from a finite or right-infinite word under that injection.