BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Cristina Sernadas (Universidade de Lisbona) DTSTART:20210902T180000Z DTEND:20210902T190000Z DTSTAMP:20260423T035716Z UID:OLS/64 DESCRIPTION:Title: Dec idability via Reduction in Logics and Their Combinations\nby Cristina Sernadas (Universidade de Lisbona) as part of Online logic seminar\n\n\nAb stract\nDecision problems in logic include semantic based problems like th e satisfiability and the validity problems\nand deductive problems like th e theoremhood and the consequence problems. Satisfaction systems and reduc tions between \nthem are presented as an appropriate context for analyzing the satisfiability and the validity problems. \nThe notion of reduction is generalized in order to cope with the meet-combination of logics.\nRed uctions between satisfaction systems induce reductions between the respect ive satisfiability problems and (under mild conditions) also between their validity problems. Sufficient conditions are provided for relating satisf iability problems to validity problems. Reflection results for decidabilit y in the presence of reductions are established. The validity problem in t he meet-combination is proved to be decidable\nwhenever the validity prob lems for the components are decidable. Some examples are discussed\, name ly\, the meet-combination of modal logic and intuitionistic logic. Some o ngoing work related to consequence problems in the context of consequence systems and their combination is pointed out. \nThis talk reports on joint work with João Rasga and Walter Carnielli.\n LOCATION:https://researchseminars.org/talk/OLS/64/ END:VEVENT END:VCALENDAR