BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Drupal iCal API//EN X-WR-CALNAME:Events items teaser X-WR-TIMEZONE:America/Toronto BEGIN:VTIMEZONE TZID:America/Toronto X-LIC-LOCATION:America/Toronto BEGIN:DAYLIGHT TZNAME:EDT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 DTSTART:20240310T070000 END:DAYLIGHT BEGIN:STANDARD TZNAME:EST TZOFFSETFROM:-0400 TZOFFSETTO:-0500 DTSTART:20231105T060000 END:STANDARD END:VTIMEZONE BEGIN:VEVENT UID:68cb9db5dbbf9 DTSTART;TZID=America/Toronto:20240403T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20240403T153000 URL:/pure-mathematics-logic/events/undecidable-extensio n-morleys-theorem-number-countable SUMMARY:An undecidable extension of Morley’s theorem on the number of\nco untable models CLASS:PUBLIC DESCRIPTION:Summary \n\nFRANKLIN TALL\, UNIVERSITY OF TORONTO\n\nWe show th at Morley’s theorem on the number of countable models of a\ncountable fi rst-order theory becomes an undecidable statement when\nextended to second -order logic. More generally\, we calculate the\nnumber of equivalence cla sses of equivalence relations obtained by\ncountable intersections of proj ective sets in several models of set\ntheory. Our methods include random a nd Cohen forcing\, large cardinals\,\nand Inner Model Theory.\n\nMC 5479\n DTSTAMP:20250918T055045Z END:VEVENT BEGIN:VEVENT UID:68cb9db5dde61 DTSTART;TZID=America/Toronto:20240327T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20240327T153000 URL:/pure-mathematics-logic/events/binding-groups-ratio nal-dynamics SUMMARY:Binding groups for rational dynamics CLASS:PUBLIC DESCRIPTION:Summary \n\nRAHIM MOOSA\, DEPARTMENT OF PURE MATHEMATICS\, UNIV ERSITY OF WATERLOO\n\nI will report on ongoing work with Moshe Kamensky to ward developing a\ntheory of binding groups for quantifier-free types in A CFA\,\nwell-suited for applications to rational algebraic dynamics.\n\nMC 5479\n DTSTAMP:20250918T055045Z END:VEVENT BEGIN:VEVENT UID:68cb9db5de713 DTSTART;TZID=America/Toronto:20240320T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20240320T153000 URL:/pure-mathematics-logic/events/klein-j-function-not -pfaffian-over-real-exponential-field SUMMARY:The Klein j-Function is not Pfaffian over the Real Exponential Fiel d CLASS:PUBLIC DESCRIPTION:Summary \n\nCHRISTOPH KESTING\, MCMASTER UNIVERSITY\n\nJames Fr eitag showed that the Klein j-function is not pfaffian over\nthe complex n umbers. In this talk\, I will give a brief introduction to\npfaffian funct ions\, their current place in model theory and Freitag's\nresult. Then I w ill discuss recent work expanding Freitag's result to\na restriction of th e j-function to the imaginary interval (0\, i) not\nbeing pfaffian over th e real exponential field.\n\nMC 5479\n DTSTAMP:20250918T055045Z END:VEVENT BEGIN:VEVENT UID:68cb9db5deea7 DTSTART;TZID=America/Toronto:20240313T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20240313T153000 URL:/pure-mathematics-logic/events/isomorphism-spectra- and-computably-composite-structures SUMMARY:Isomorphism Spectra and Computably Composite Structures CLASS:PUBLIC DESCRIPTION:Summary \n\nJOEY LAKERDAS-GAYLE\, DEPARTMENT OF PURE MATHEMATIC S\, UNIVERSITY OF\nWATERLOO\n\nIf $\\mathcal{A}$ and $\\mathcal{B}$ are tw o computable copies of a\nstructure\, their isomorphism spectrum is the se t of Turing degrees\nthat compute an isomorphism from $\\mathcal{A}$ to $\ \mathcal{B}$. We\nintroduce a framework for constructing computable struct ures with the\nproperty that the isomorphisms between arbitrary computable copies of\nthese structures are constructed from isomorphisms between com putable\ncopies of their component structures. We call these \\emph{comput ably\ncomposite structures}. We show that given any uniformly computable\n collection of isomorphism spectra\, there exists a pair of computably\ncom posite structures whose isomorphism spectrum is the union of the\noriginal isomorphism spectra. We use this to construct examples of\nisomorphism sp ectra that are not equal to the upward closure of any\nfinite set of Turin g degrees.\n\nMC 5479\n DTSTAMP:20250918T055045Z END:VEVENT BEGIN:VEVENT UID:68cb9db5df6f7 DTSTART;TZID=America/Toronto:20240306T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20240306T153000 URL:/pure-mathematics-logic/events/splitting-differenti al-logarithm-map-using-galois-theory SUMMARY:Splitting the differential logarithm map using Galois theory CLASS:PUBLIC DESCRIPTION:Summary \n\nCHRISTINE EAGLES\, DEPARTMENT OF PURE MATHEMATICS\, UNIVERSITY OF\nWATERLOO\n\nAn ordinary algebraic differential equation is said to be internal to\nthe constants if its general solution is obtained as a rational\nfunction of finitely many of its solutions and finitely ma ny constant\nterms. Such equations give rise to algebraic groups behaving as Galois\ngroups. In this talk I give a characterisation of when the pull back of\nthe differential logarithm of an equation is internal to the cons tants\nwhen the Galois group is unipotent or a torus. This is joint work in\nprogress with Leo Jimenez.\n\nMC 5479\n DTSTAMP:20250918T055045Z END:VEVENT BEGIN:VEVENT UID:68cb9db5dfeb1 DTSTART;TZID=America/Toronto:20240228T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20240228T153000 URL:/pure-mathematics-logic/events/computable-continuou s-logic-qwep-and-type-iii-factors SUMMARY:Computable Continuous Logic\, QWEP\, and Type III Factors CLASS:PUBLIC DESCRIPTION:Summary \n\nJANANAN ARULSEELAN\, MCMASTER UNIVERSITY\n\nBy the recent MIP*=RE result\, the QWEP conjecture is known to be\nfalse. Consequ ently\, the universal theory of the hyperfinite II_1\nfactor is not comput able. We will explain these results and their\ncontext and then discuss th e uncomputability of the universal theories\nof other Powers factors and t he lack of an effective axiomatization of\nQWEP C^∗ algebras. As an appl ication we show that there is a\nultraproduct of non-QWEP algebras with QW EP. This is joint work with\nIsaac Goldbring and Bradd Hart. \n\nMC 5479\ n DTSTAMP:20250918T055045Z END:VEVENT BEGIN:VEVENT UID:68cb9db5e0713 DTSTART;TZID=America/Toronto:20240214T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20240214T153000 URL:/pure-mathematics-logic/events/continuous-stable-re gularity SUMMARY:Continuous Stable Regularity CLASS:PUBLIC DESCRIPTION:Summary \n\nNICOLAS CHAVARRIA\, DEPARTMENT OF PURE MATHEMATICS\ , UNIVERSITY OF\nWATERLOO\n\nWe discuss joint work with G. Conant and A. P illay regarding a version\nof the Malliaris-Shelah stable regularity lemma realized in the\ncontext of continuous logic\, which allows us to speak a bout the\nstructure of stable functions of the form $f:V\\times W\\to [0\, 1]$\,\nwhere we think of $V$ and $W$ as the parts of a \"weighted'' bipart ite\ngraph. In the process\, we will also mention some results about the\n structure of local Keisler measures in this setting.\n\nMC 5479\n DTSTAMP:20250918T055045Z END:VEVENT BEGIN:VEVENT UID:68cb9db5e0f29 DTSTART;TZID=America/Toronto:20240131T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20240131T153000 URL:/pure-mathematics-logic/events/residually-finite-eq uational-theories SUMMARY:Residually finite equational theories CLASS:PUBLIC DESCRIPTION:Summary \n\nROSS WILLARD\, UNIVERSITY OF WATERLOO\n\nAn equatio nal theory T is said to be residually finite if every model\nof the theory can be embedded in a product of finite models of the\ntheory.  Equivalen tly\, T is residually finite if and only if its\nirreducible models (those that cannot be embedded in products of\n“simpler” models) are all fin ite.  In practice\, it seems that\nwhenever a theory is both “interesti ng” and residually finite\,\nthen there is a finite upper bound to the s izes of its irreducible\nmodels.  In other words\, we see a sort of compa ctness principle for\n“interesting” equational theories: if such a the ory has\narbitrarily large finite irreducible models\, then it must have a n\ninfinite irreducible model.  Whether or not this observation holds\nge nerally has been open for almost 50 years.  In this talk I will\ndiscuss some recent progress with collaborators Keith Kearnes and\nAgnes Szendrei. \n\nMC 5479\n DTSTAMP:20250918T055045Z END:VEVENT BEGIN:VEVENT UID:68cb9db5e174f DTSTART;TZID=America/Toronto:20240124T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20240124T153000 URL:/pure-mathematics-logic/events/generic-derivations- o-minimal-structures SUMMARY:Generic derivations on o-minimal structures CLASS:PUBLIC DESCRIPTION:Summary \n\nELLIOT KAPLAN\, MCMASTER UNIVERSITY\n\nLet T be a m odel complete o-minimal theory that extends the theory of\nreal closed ord ered fields (RCF). We introduce T-derivations:\nderivations on models of T which cooperate with T-definable functions.\nThe theory of models of T ex panded by a T-derivation has a model\ncompletion\, in which the derivation acts \"generically.\" If T = RCF\,\nthen this model completion is the the ory of closed ordered\ndifferential fields (CODF) as introduced by Singer. We can recover\nmany of the known facts about CODF (open core\, distality ) in our\nsetting. We can also describe thorn-rank for models of T with a\ ngeneric T-derivation. This is joint work with Antongiulio Fornasiero.\n\n MC 5479\n DTSTAMP:20250918T055045Z END:VEVENT BEGIN:VEVENT UID:68cb9db5e1f94 DTSTART;TZID=America/Toronto:20240117T143000 SEQUENCE:0 TRANSP:TRANSPARENT DTEND;TZID=America/Toronto:20240117T153000 URL:/pure-mathematics-logic/events/sparse-subsets-reals SUMMARY:Sparse subsets of the reals CLASS:PUBLIC DESCRIPTION:Summary \n\nJASON BELL\, DEPARTMENT OF PURE MATHEMATICS\, UNIVE RSITY OF WATERLOO\n\nWe look at the first-order theory of the real numbers augmented by a\npredicate X that is in some natural sense self-similar wi th respect to\na positive integer base. We show that there is a dichotomy: either we\ncan define a Cantor set in our structure or our expansion of t he reals\nis interdefinable with the real numbers augmented by a set of th e form\n{1/r\, 1/r^2\, 1/r^3\, …} for some integer r>=2.  In the latter case\,\nthis is equivalent to the structure having NIP and NTP_2.  This is\njoint work with Alexi Block Gorman.\n\nMC 5479\n DTSTAMP:20250918T055045Z END:VEVENT END:VCALENDAR