Logic Seminar

The Logic Seminar is a joint LOS/IMAR/ILDS seminar, featuring talks on mathematical logic, philosophical logic and logical aspects of computer science.

All seminars, except where otherwise indicated, will be on Thursdays between 14:00 and 16:00, Bucharest time. The seminars are held locally at Hall 203 of the Faculty of Mathematics and Computer Science, University of Bucharest (in the new PBTower location), but can also be occasionally held remotely.

To receive announcements about the seminar, please send an email to logic-seminar@ilds.ro.

Organizers: Laurențiu Leuștean, Andrei Sipoș

Past Talks in 2025-2026

Thursday, March 12, 2026

Gabriel Istrate (University of Bucharest)

Circumcenter-Restricted Colorings of the Plane

Abstract:

We investigate the colorings of the plane for which the color of a point p  is constrained by monochromatic sets of points on circles centered at p.  We study three classes of conditions, based on cardinality (of forcing  sets or admissible circles), on shapes of forcing triangles, and on admissible  lengths of sides of forcing convex polygons, for colorings that use finitely many or countable infinite colors. The focus is on determining whether a specific condition forces the coloring to be locally or globally monochromatic. Counterexamples constructed using existing results show that, for conditions based on shapes, we need to impose additional regularity conditions on color classes, and we study colorings for which every color class has the Baire property.

This is joint work with Cătălin Zara (UMass Boston).

Thursday, March 26, 2026

Roberto Giuntini (University of Cagliari and TU München)

Open Problems in Quantum Multi-valued Algebras

Abstract:

The talk is framed by the sharp/unsharp distinction and by the classical/quantum divide. Within this perspective, we consider the corresponding algebraic semantics — Boolean and Multi-Valued algebras (MV-algebras) on the classical side, orthomodular lattices and Quantum MV-algebras (QMV-algebras) on the quantum side — and we highlight a few axiomatization problems that emerge naturally. On the classical side, Boolean algebras represent sharp yes/no reasoning, while MV-algebras provide the standard algebraic semantics for graded (unsharp) truth in the Łukasiewicz tradition. On the quantum side, orthomodular lattices capture the algebra P(H) of sharp quantum events (projectors), whereas realistic measurements motivate unsharp quantum events (called effects) E(H) and their corresponding many-valued structure.

A key unifying role is played by QMV-algebras, intended as an algebraic environment where (i) sharp quantum structures can be recovered as special, idempotent cases, and (ii) classical many-valued reasoning can be recovered as cases where the generalized Sasaki conjunction commutes. Within this framework, we focus on the equational landscape generated by Hilbert-space-inspired structures. The concluding part is devoted to three open questions. In the sharp quantum setting, letting ℙ(ℍ) denote the variety generated by the class of all lattices P(H), one asks whether ℙ(ℍ) can be (finitely) axiomatized. In the unsharp quantum setting, two analogous problems arise for QMV-algebras: whether the variety 𝔼(ℍ) generated by the class of all algebras E(H) is (finitely) axiomatizable, and whether the variety generated by all quasi-linear QMV-algebras is (finitely) axiomatizable. These questions mark precise points where algebraic logic meets the structural complexity of quantum phenomena, and they provide a focused agenda for further work on quantum many-valued semantics.

Past Seminars