Weak bisimilarity is one of the most studied behavioural equivalences. This equivalence is undecidable for pushdown processes (PDA), process algebras (PA), and multiset automata (MSA, also known as parallel pushdown processes, PPDA). Its decidability is an open question for basic process algebras (BPA) and basic parallel processes (BPP). We move the undecidability border towards these classes b...

Harmonic Analysis [59] N. Bourbaki. Théories spectrales, Chapitres 1 et 2. Éléments de Mathématique,Réimpression inchangée de l’édition originale de 1967, Springer-Verlag, 2007[60] G. B. Folland. A Course in Abstract Harmonic Analysis. CRC Press, 1995[61] L. H. Loomis. An Introduction to Abstract Harmonic Analysis. van Nostrand,1953[62] M. A. Năımark. Normed Algebras. Third ...

In this essay, we immerse into the framework of normed division algebras as a suitable arena to accommodate standard model elementary particles, and explore some applications cosmology. Remarkably, they permit interesting non-trivial realisations cosmological principle with an interplay between symmetry groups quaternions octonions. We also argue how these give rise potentially observational si...