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Events for March – July

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Tue, Mar. 4 1:25pm (online)	Algebra/Logic Moritz Schöbi (TU Wien, Austria) View Online:https://cuboulder.zoom.us/j/96896272260 X The Bodirsky-Pinsker conjecture is an infinite counterpart to the Feder-Vardi dichotomy conjecture for Constraint Satisfaction Problems (CSPs) with finite templates. While the latter has been confirmed independently by Bulatov and Zhuk, the former remains wide open. In this talk, we shed light on three meta-problems regarding the scope of this conjecture. Our first result provides a significant structural simplification of this scope: we prove that the conjecture is equivalent to its restriction to templates without algebraicity, a crucial assumption in many powerful classification methods. The second result provides a simplification of algebraic nature: any algebraic condition characterizing any complexity class within the conjecture must be satisfiable by injections. In particular, this offers insight into which universal-algebraic conditions for the complexity of finite-template CSPs may be successfully lifted to the infinite case. The third result we are going to explore links the conjecture to so-called Promise Constraint Satisfaction Problems (PCSPs): using the construction from the first result, virtually every structure from the scope of the conjecture allows us to construct a sandwich structure for a non-finitely tractable finite-domain PCSP. This is joint work with Michael Pinsker, Jakub Rydval and Christoph Spiess. Eliminating algebraicity and enforcing injectivity in infinite-domain constraint satisfaction
Tue, Mar. 4 2:30pm (MATH 3…	Lie Theory Richard Green (CU) X We will show how to use root systems of types E6, E7, and E8 to construct generalizations of quantum Pfaffians and quantum Hafnians. These constructions are closely related to the combinatorics of del Pezzo surfaces, and they give rise to new q-analogues of an invariant cubic polynomial in type E6,and a quartic polynomial in type E7. This is work in progress with Tianyuan Xu (University of Richmond). Generalized quantum Pfaffians and quantum Hafnians
Tue, Mar. 4 2:30pm (MATH 2…	Grad Algebra/Logic Keith Kearnes (CU) View Online:https://cuboulder.zoom.us/j/96896272260 The structure of finite algebras, 6
Tue, Mar. 4 3:30pm (MATH 3…	Topology James Woodcock TBD
Wed, Mar. 5 5pm (Math 350)	Math Club Clyde Kertzer X Circle packing is the study of arranging circles on a surface so that no overlap occurs and no circle can be enlarged without creating overlap. This interactive talk was developed by the speaker as part of an Experimental Math Lab and the content of the talk is based on work he did with Dr. Kate Stange for his honor's thesis. Circle Packing
Thu, Mar. 6 11:15am (MATH …	Algebraic Geometry Nolan Schock (UIC) X The moduli space of marked cubic surfaces is one of the most classical moduli spaces in algebraic geometry, dating back to the nineteenth century work of Cayley and Salmon. I will discuss a number of results describing geometrically meaningful and interesting compactifications of the moduli space of marked cubic surfaces from the perspectives of modern moduli theory, birational geometry, tropical geometry, classical algebraic geometry, and Hodge theory. These results include explicit descriptions of the combinatorics, intersection theory, and birational geometry of these compactifications, as well as a complete, detailed description of the surfaces they parameterize. Geometry of moduli of marked cubic surfaces Sponsored by the Meyer Fund
Fri, Mar. 7 11:15am (Math …	Math Edu Lee Roberson X As teachers, we use the power of questions to assess and build our students’ mathematical understanding. The questions we ask can determine how our students think about concepts, respond to inquiry, collaborate with others, connect ideas, and ask their own questions. Because of this, we will take time to pause and reflect on the questions we ask in our classes. We will question the purpose of our questions, the types of questions we ask, and the questioning strategies we use to better understand our own pedagogical practices so that we can improve our students’ mathematical understanding. Questioning Our Questions
Tue, Mar. 11 11am (MATH 350)	Number Theory Sarah Arpin X The isogeny-based cryptographic protocol CSIDH is based on the group action of the class group of a particular imaginary quadratic order on certain elliptic curves. The efficiency and security of CSIDH has inspired variant protocols, such as SCALLOP and OSIDH. Such protocols are based on the vectorization problem: Given elliptic curves E, E', find the ideal class whose action on E yields E'. In this work, we provide a general understanding of this question in the context of orientations and level structure on elliptic curves. In particular, we study a large family of generalized class groups of imaginary quadratic orders O and prove that they act freely and (essentially) transitively on the set of primitively O-oriented elliptic curves over a field k (assuming this set is non-empty) equipped with appropriate level structure. This is joint work with Wouter Castryck, Jonathan Komada Eriksen, Gioella Lorenzon, and Frederik Vercauteren. Generalized class group actions on oriented elliptic curves with level structure
Tue, Mar. 11 12:10pm (MATH …	Kempner Edmund Harriss (University of Arkansas) X Euclid's elements is regarded as an early example of proof and axiomatic methods but it also has a tradition within carpentry and construction. The straight line and circle can just as easily be regarded as abstract representations of the action of straight edge and compass just as easily as the other way round. Today we have many machines that can play the same role creating a bridge between the abstract and the physical. What potentials do they provide for realising mathematical concepts in physical space and creating manufacturing techniques? In this talk I will look at several examples of machines with mathematical models, including affine spaces, ruled and developable surfaces and the gradient present in the grain of wood. Mathematical Manufacturing since Euclid
Tue, Mar. 11 1:15pm (MATH 3…	Geometry/Analysis Tristan Léger (Yale University) X In this talk I will discuss recent and upcoming results on the boundedness of spectral projectors. The seminal work of C. Sogge gives the optimal result on any Riemannian manifold with bounded geometry for spectral windows of size 1. However when the width is smaller, the spectral projector bounds become sensitive to the global geometry of the underlying manifold. I will focus on the case of hyperbolic surfaces of infinite area, and present new estimates that hold universally in that setting. This is joint work with Jean-Philippe Anker and Pierre Germain. Spectral projector bounds on hyperbolic surfaces of infinite area Sponsored by the Meyer Fund
Wed, Mar. 12 3:30pm (MATH350)	Math Phys Ezzeddine El Sai (CU Boulder) X In this talk, we will introduce the basic tools and terminology for future talks on Machine Learning and Statistical Applications. Fitting with the theme of this seminar, we will also touch on concepts regarding the physical meaning of "information" and its connections with Statistics. Statistics and Mathematical Physics
Wed, Mar. 12 3:30pm (MATH 2…	Algebra/Logic Joel David Hamkins (Notre Dame University) X I shall introduce and describe the subject of modal model theory, in which one studies a mathematical structure within a class of similar structures under an extension concept, giving rise to mathematically natural notions of possibility and necessity, a form of mathematical potentialism. We study the class of all graphs, or all groups, all fields, all orders, or what have you; a natural case is the class of all models of a fixed first-order theory. In this talk, I shall describe some of the resulting elementary theory, particularly the remarkable expressive power of modal graph theory. This is joint work with my Oxford student Wojciech Woloszyn. Introduction to modal model theory
Thu, Mar. 13 11:15am (MATH …	Algebraic Geometry Leo Herr (Virginia Tech) X Joint work with Sara Mehidi, Marta Pieropan, Thibault Poiret Let X --> Y be a morphism of varieties and k a field. Consider the set X(k) of k-points, or solutions to the equations defining X with coordinates in k. If X = V(x^2 + y^2 - 1) for example, then the set of Q-points consists of primitive Pythagorean triples and the geometry of X shows there are infinitely many solutions. According to Hindry-Silverman, "Geometry determines Arithmetic." We want to determine the image of the map on k-points X(k) --> Y(k). Suppose X --> Y arises as the fiber over 0 of a family of varieties X' --> Y'. The geometry of the family X' --> Y' can also constrain the type of k-points that land in the image of X(k) --> Y(k), as Campana observed. Abramovich generalized this notion in a beautiful, incomplete manuscript called "birational geometry for number theorists" and gave us permission to realize this vision using log geometry. Log structures on X, Y remember enough about the families X', Y' to constrain the rational points. "Birational geometry for number theorists" for log geometers
Thu, Mar. 13 1:30pm (MATH 2…	Grad Student Seminar Édouard Heitzmann X A districting of a graph G is a partition of G into simply connected subgraphs P_i. MCMC methods are frequently used to sample the space of districtings, with Recombination Steps being a computationally inexpensive and rapidly mixing transition rule to run such a chain. This talk will define Recombination Steps, survey the literature surrounding them, and outline the proof of an irreducibility result for this proposal when G is a triangular subset of the triangular lattice. An irreducibility result for districtings of triangular subsets of the triangular lattice
Thu, Mar. 13 2:30pm (MATH 3…	Functional Analysis Jordan Watts (University of Central Michigan) X Moving from finite-dimensional calculus to an infinite-dimensional setting immediately forces one to contend with a lot of point-set topology and analysis that was less of a concern before. In this talk, we examine a classical way of taking derivates of a function between locally convex spaces from a diffeological and Sikorski perspective. We apply our results by studying several infinite-dimensional groups of relevance to symplectic topologists. Joint work with Yael Karshon. Infinite-Dimensional Calculus and Symplectic Topology
Fri, Mar. 14 11:15am (Math …	Math Edu Rebekah Jones & Courtney Hauf X In this interactive seminar, we will be discussing excerpts from Building Thinking Classrooms by Peter Liljedahl. This book focuses on research-backed strategies to foster engagement and critical thinking in the mathematics classroom. Participants will reflect on their own experiences and discuss practical ways to implement the strategies discussed in excerpts, so please look at the reading ahead of time ( link to reading). Building Thinking Classrooms Discussion
Tue, Mar. 18 2:30pm (MATH 2…	Grad Algebra/Logic Keith Kearnes (CU) View Online:https://cuboulder.zoom.us/j/96896272260 The structure of finite algebras, 7
Tue, Mar. 18 3:30pm (MATH 3…	Topology Alex LaJeunesse (CU Boulder) X Topological K-theory was the first seriously studied example of a generalized cohomology theory, leading to the incredibly rich world of spectra and stable homotopy theory that we see today. In this talk we will give a remarkable description of the spectrum KU representing this theory, due to Snaith. We will also look at a generalization of this construction to chromatic homotopy theory due to Westerland, and sketch how it relates to the failure of Ravenel’s Telescope Conjecture. Snaith's Theorem
Wed, Mar. 19 3:30pm (MATH350)	Math Phys Ezzeddine El Sai (CU Boulder) X TBA Statistical Learning
Thu, Mar. 20 11:15am (MATH …	Algebraic Geometry Ruijie Yang (Kansas) X We will discuss some number theoretic motivation for studying minimal exponent of a hypersurface, which is the nonarchimedean counterpart of the Archimedean zeta function. Then I will explain a toy model, i.e. Milnor fiber of an isolated singularity, for the proof of the main theorem. We will see why Hodge theory naturally enters into the picture. Minimal exponent of hypersurfaces, p-adic integration and Milnor fibers Sponsored by the Meyer Fund
Thu, Mar. 20 2:30pm (MATH 3…	Functional Analysis Laura Scull (Fort Lewis College) X One common way of representing spaces with singularities is via topological groupoids. However, such a representation is not unique, and a space may be represented by many different groupoids, leading to the idea of Morita equivalence of groupoids. To work with these spaces, we define a localised bicategory of groupoids in which Morita equivalences become isomorphisms. This localisation can be done in several equivalent ways, as developed by Pronk and Roberts. Our interest lies in a particularly nice and ubiquitous class of examples, the action groupoids which represent the quotient of a space by an action of a group. Such groupoids come with their own notion of morphisms given by equivariant functors. Our aim is to connect these two viewpoints. We create a localised bicategory built on equivariant functors of groupoids, and show that for action groupoids, this is equivalent to the bicategories of Pronk and Roberts. Using this viewpoint, Morita equivalences may be defined using a certain class of equivariant projection functors, and many common conditions on the singularities can be integrated into this construction. This also gives us a way of examining invariants from equivariant homotopy to see if they can be made Morita invariant and extended to our setting. This talk is based on joint work with J. Watts and C. Farsi. The talk will include many pictures and examples illustrating the underlying geometric intuition behind the abstraction of the bicategories. Localising Action Groupoids
Thu, Mar. 20 3:35pm (MATH 3…	Probability Giorgio Cipolloni (University of Arizona) X We study the Brownian evolution of large non-Hermitian matrices and show that their log-determinant converges to a 2+1 dimensional Gaussian field in the Edwards-Wilkinson regularity class, i.e. logarithmically correlated for the parabolic distance. This gives a dynamical extension of the celebrated result by Rider and Virag (2006) proving that the fluctuations of the eigenvalues of Gaussian non-Hermitian matrices converge to a 2 dimensional log-correlated field. Our result, previously not known even in the Gaussian case, holds out of equilibrium for general matrices with i.i.d. entries. We also study the extremal values of these fields and demonstrate their logarithmic dependence on the matrix dimension. Logarithmically correlated fields from non-Hermitian random matrices
Thu, Mar. 27 12:30pm (Online)	Rep Theory Thomas Creutzig (FAU Erlangen-Nürnberg) X A while ago and with David Ridout a Verlinde formula for the affine VOAs of sl(2) at admissible level was conjectured. This is a VOA whose representation category is neither finite nor semisimple. Our idea was to replace the Verlinde S-matrix by an S-kernel and atypical modules by their resolutions of typical modules to get a natural Verlinde formula conjecture. I will explain why this formalism is true. Verlinde's formula in logarithmic CFT
Tue, Apr. 1 2:30pm (MATH 2…	Grad Algebra/Logic Keith Kearnes (CU) View Online:https://cuboulder.zoom.us/j/96896272260 The structure of finite algebras, 8
Tue, Apr. 1 3:30pm (MATH 3…	Topology XiaoLin Danny Shi (University of Washington) X I will talk about equivariant homotopy theory and its role in the proof of the Segal conjecture and the Kervaire invariant one problem. Then, I will talk about chromatic homotopy theory and its role in studying the stable homotopy groups of spheres. These newly established techniques allow one to use equivariant machinery to attack chromatic computations that were long considered unapproachable. Equivariant methods in chromatic homotopy theory
Wed, Apr. 2 3:30pm (MATH350)	Math Phys Markus Pflaum (CU Boulder) X TBA Born-Oppenheimer Approximation
Thu, Apr. 3 12:30pm (Online)	Rep Theory Arim Song (University of Denver) View Online:https://cuboulder.zoom.us/j/97927772782 X Supersymmetric(SUSY) W-algebras are vertex algebras constructed through SUSY Hamiltonian reduction based on Lie superalgebras with osp(1\|2) embeddings. By construction, they have a supersymmetric structure that naturally couples the generators of the algebras. Madsen and Ragoucy conjectured that SUSY W-algebras are isomorphic to W-algebras up to a tensor product with free field algebras. In recent joint work with Genra and Suh, we proved this conjecture for principal SUSY W-algebras. In this talk, I will introduce SUSY W-algebras and the concept of SUSY vertex algebras, which provides a mathematical framework for the study. Then, I will discuss key properties of SUSY W-algebras in comparison to W-algebras, a part of which contributes to the proof of the conjecture. This talk is based on my recent paper and the one with Genra and Suh. Supersymmetric W-algebras vs. W-algebras
Thu, Apr. 3 1:30pm (MATH 3…	Algebraic Geometry Patricio Gallardo (UC Riverside) X I will discuss my ongoing work with J. Mukherjee on the classification and moduli of varieties of general type constructed via abelian covers. In particular, I will describe the behavior of their numerical invariants, the ratio of their Chern numbers, and conditions under which abelian covers can be used to construct an open subset within a component of the corresponding moduli space. This is part of AG day: https://sites.google.com/colorado.edu/front-range-ag/ Invariants and moduli spaces of abelian covers Sponsored by the Meyer Fund
Fri, Apr. 4 2:30pm (MATH 3…	Functional Analysis Alonso Delfín (CU Boulder) X The talk will be about a generalization of Hölder duality to algebra-valued pairings. Roughly, Hölder duality states that if and satisfy . In finite dimension, this is easy to see as both and are algebraically isomorphic to and it’s just a matter of checking that the pairing does indeed define a linear functional that recovers the p’-norm of . In this talk we now take to be the -column direct sum of a fixed algebra and to be the -row direct sum of . We now naturally get an -valued dual pairing, so it makes sense to ask whether a version of Hölder duality still holds. I will present examples of A for which a Hölder-like duality still holds, but also discuss other examples for which it doesn’t. The talk is based on an REU project that ran in CU-Boulder during Summer 2024. C*-like modules and matrix p-operator norms
Fri, Apr. 4 3:35pm (MATH 2…	Geometry/Analysis Juhi Jang (University of Southern California) X We will discuss recent progress on the vacuum free boundary problems arising in the dynamics of isolated gases with or without gravity. We give an overview of the well-posedness and stability theory, and present some new results on waiting time solutions. Vacuum Free Boundary Problems in Gas Dynamics Sponsored by the Meyer Fund
Tue, Apr. 8 2:30pm (MATH 3…	Lie Theory Shigenori Nakatsuka (FAU Erlangen-Nurnberg) X W-superalgebras are a large class of vertex algebras obtained from affine Lie algebras. Due to their duality, hook-type W-superalgebras have captured a lot of attention in the last decade. I will explain the duality in their representation theory and the phenomenon appearing at the level of characters. Duality of hook-type W-superalgebras and characters Sponsored by the Meyer Fund
Wed, Apr. 9 3:30pm (MATH350)	Math Phys Wilson Wu (CU Boulder) X TBA Neural Networks
Thu, Apr. 10 2:30pm (MATH 3…	Functional Analysis Angel Roman (University of Washington St Louis) X A double groupoid is a type of higher groupoid structure in which there are two distinct groupoid products on the same set of arrows and must satisfy a certain compatibility law. A particular example we will focus on is that of an irrational torus, and more generally, strict 2-groups. Since groupoid structures give rise to convolution algebras, a double groupoid gives rise to two convolution products. We ask, in what sense are the two convolution products compatible? This is based on joint work with Joel Villatoro. Convolution Algebras of Double Groupoids and Strict 2-Groups
Fri, Apr. 11 3:35pm (MATH 2…	Geometry/Analysis Willie Wong (Michigan State University) X Our understanding of cosmological processes, like many other predictions of physical theories, are based on studying regimes where the equations of motion reduce to a finite dimensional dynamical system. An example of a conclusion derived from such reductions is the idea of a big bang cosmology in general relativity. Such reductions are physically justified by the working assumption that when viewed from the largest scales, the inhomogeneities average out and the matter content can be approximated by a homogeneous compressible fluid. Jointly with Shih-Fang Yeh, we probe whether this working assumption is justified mathematically. Our results show that on the cosmological timescale, some big bang solutions are susceptible to instabilities generated through nonlinear self-interactions of the constituent matter when inhomogeneities are present. The goal of this talk is to present the mathematical context of this result and briefly describe the mechanism driving the instability, focusing on the relevance of the conformal (or causal) geometry of the big bang solutions. (No prior familiarity with mathematical relativity is assumed.) Some Big Bangs are Unstable Sponsored by the Meyer Fund
Mon, Apr. 14 3:35pm (MATH 3…	Grad Student Seminar Chris Eblen (CU Boulder) X Schur--Weyl duality is a fundamental paradigm in representation theory relating representations of the general linear group to those of the symmetric group. We will discuss the classical case of Schur--Weyl duality and an analog for the unipotent upper triangular matrix group over a finite field. Then we will define supercharacter theory and how a particular supercharacter theory for the unipotent upper triangulars, within the context of this Schur--Weyl duality analog, lead to a class of modules called beach modules and a collection of projection-like maps in the centralizer algebra. A Day at the Beach
Tue, Apr. 15 3:30pm (MATH 3…	Topology Stephanie Oh (CU Boulder) TBD
Wed, Apr. 16 3:30pm (MATH350)	Math Phys Noah Song (CU Boulder) X TBA Hartree-Fock Method
Thu, Apr. 17 2:30pm (MATH 3…	Functional Analysis Samantha Brooker (Virginia Tech) TBD
Fri, Apr. 18 11:15am (Math …	Math Edu Padi Fuster Aguilera X In this talk I will present two of my passion projects around the topic of belonging in mathematics: the Math For All conference and the Meet a Mathematician interview collection. Math For All is a conference with the goal of creating a welcoming environment to enjoy and discuss mathematics. Meet a Mathematician is a collection of video interviews to mathematicians mostly from historically excluded groups in mathematics. Both projects aim to spotlight role models for students from underrepresented groups in mathematics at the same time as highlighting their other identities and career life. Belonging in Mathematics
Tue, Apr. 22 2:30pm (MATH 3…	Lie Theory Juan Villarreal (University of Colorado Boulder) TBA
Tue, Apr. 22 3:30pm (MATH 3…	Topology Alexander Waugh (University of Washington) TBD
Wed, Apr. 23 3:30pm (MATH350)	Math Phys Noah Song (CU Boulder) X TBA Coupled Cluster Theory
Wed, Apr. 23 3:30pm (MATH350)	Math Phys Wilson Wu X TBA Mathematical Foundations of Deep Learning
Fri, Apr. 25 11:15am (Math …	Math Edu Peter Karanevich 5 practices of Orchestrating Productive Mathematics Discussions
Fri, Apr. 25 3:35pm (MATH 2…	Geometry/Analysis Maja Taskovic (Emory University) TBA Sponsored by the Meyer Fund
Tue, Apr. 29 3:30pm (MATH 3…	Topology Emily Montelius (CU Boulder) TBD
Wed, Apr. 30 3:30pm (Math350)	Math Phys Tim Schumacher Balls in bins
Thu, May. 1 2:30pm (MATH 3…	Functional Analysis David Blecher (University of Houston) TBA

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