семинар Алгебра и логика

На 11 март 2022 г. (петък) от 14:00 ч. ще се проведе дистанционно заседание на семинара по „Алгебра и логика”. Доклад на тема: Multi-summation in difference rings and applications ще изнесе Carsten Schneider (Research Institute for Symbolic Computation, Johannes Kepler University, Linz, Austria). Резюме. Symbolic summation in difference fields started with Karr's summation algorithm (1981) which can be considered as the discrete version of Risch's indefinite integration algorithm in differential fields. In the last 20 years this approach has been generalized and enhanced to a constructive summation theory of difference rings. In general, one can represent algorithmically any expression in terms of indefinite nested sums defined over hypergeometric products in such rings. As a crucial by-product one obtains optimal representations where the arising sums [...]

На 18 март 2022 г. (петък) от 16:00 ч. ще се проведе дистанционно заседание на семинара по „Алгебра и логика”. Доклад на тема: Absorbing ideal structures of commutative rings ще изнесе Ece Yetkin Celikel (Hasan Kalyoncu University, Turkey). Резюме. Let R be a commutative ring with nonzero identity. As generalizations of prime ideals, the absorbing ideals were first defined and studied by A. Badawi in 2007. A proper ideal I of R is said to be 2-absorbing if whenever a, b, c ∈ R with abc ∈ I, then either ab ∈ I or ac ∈ I or bc ∈ I. After this date, many researches have been done to introduce various extensions of this concept. In this talk, we present some absorbing ideals [...]

На 25 март 2022 г. (петък) от 13:00 ч. ще се проведе дистанционно заседание на семинара по „Алгебра и логика”. Доклад на тема: An Application of Separation in Discrete Time Interval Temporal Logic to Branching Time ще изнесе Димитър Гелев (ИМИ - БАН). Резюме. In this talk we make an application of our separation theorem for discrete time Interval Temporal Logic (ITL) to the study of Interval-based Computation Tree Logic (ICTL*). We prove that the expressibility of the expanding modalities and, most importantly, propositional quantification, carry over from linear time ITL to the branching time system of ICTL*. The relevance of this follows from the fact that point-based propositionally quantified CTL* (QCTL*) is the established intermediate language for temporal logics of agency as propositional [...]

На 1 април 2022 г. (петък) от 13:00 ч. ще се проведе дистанционно заседание на семинара по „Алгебра и логика”. Доклад на тема: Automorphisms of simple quotients of the Poisson and universal enveloping algebras of sl_2 ще изнесе Altyngul Naurazbekova (L. N. Gumilyov Eurasian National University, Nur-Sultan, Kazakhstan). Резюме. Let P(sl_2(K)) be the Poisson enveloping algebra of the Lie algebra sl_2(K) over an algebraically closed field K of characteristic zero. U. Umirbaev, V. Zhelyabin proved that the quotient algebras P(sl_2(K))/(C_P - λ), where C_P is the standard Casimir element of sl_2(K) in P(sl_2(K)) and 0 ≠ λ ∈K, are simple. Using a result by L. Makar-Limanov on groups of automorphisms of a class of surfaces, we describe generators of the automorphism group of P(sl_2(K))/(C_P [...]