< 2023 >
November
  • 01
    11/01/2023

    Unveiling Correlated Topological Insulators through Fermionic Tensor Network States

    10:30 am-11:30 am
    11/01/2023

    Topological Quantum Matter Seminar

    Speaker: Shenghan Jiang, Kavli Institute for Theoretical Sciences UCAS

    Title: Unveiling Correlated Topological Insulators through Fermionic Tensor Network States

    Abstract: The study of topological band insulators has revealed fascinating phases characterized by band topology indices, harboring extraordinary boundary modes protected by anomalous symmetry actions. In strongly correlated systems, it has been established that topological insulator phases persist as stable phases. However, due to the inability to express the ground states of such systems as Slater determinants, the formulation of generic variational wavefunctions for numerical simulations is highly desirable.
    In this talk, we tackle this challenge by developing a comprehensive framework with fermionic tensor network states. Starting from simple assumptions, we write down tensor equations, construct edge theories and extract quantum anomaly data for topological insulators. By exhaustively exploring all possible sets of equations, we achieve a systematic classification of topological insulator phases. Imposing the solutions of a given set of equations onto local tensors, we obtain generic variational wavefunctions for corresponding topological insulator phases. Our methodology provides a crucial first step towards simulating topological insulators in strongly correlated systems.

     

  • 01
    11/01/2023

    Universality of max-margin classifiers

    3:30 pm-4:30 pm
    11/01/2023
    CMSA Room G10
    CMSA, 20 Garden Street, Cambridge, MA 02138 USA

    Probability Seminar

    Speaker: Youngtak Sohn (MIT)

    Title: Universality of max-margin classifiers

    Abstract: Many modern learning methods, such as deep neural networks, are so complex that they perfectly fit the training data. Despite this, they generalize well to the unseen data. Motivated by this phenomenon, we consider high-dimensional binary classification with linearly separable data. First, we consider Gaussian covariates and characterize linear classification problems for which the minimum norm interpolating prediction rule, namely the max-margin classification, has near-optimal prediction accuracy. Then, we discuss universality of max-margin classification. In particular, we characterize the prediction accuracy of the non-linear random features model, a two-layer neural network with random first layer weights. The spectrum of the kernel random matrices plays a crucial role in the analysis. Finally, we consider the wide-network limit, where the number of neurons tends to infinity, and show how non-linear max-margin classification with random features collapse to a linear classifier with a soft-margin objective.

    Joint work with Andrea Montanari, Feng Ruan, Jun Yan, and Basil Saeed.

  • 02
    11/02/2023

    Landscape of quantum phases in quantum materials

    4:30 pm-6:00 pm
    11/02/2023
    CMSA Room G10
    CMSA, 20 Garden Street, Cambridge, MA 02138 USA

    Joint Quantum Matter in Mathematics and Physics and Topological Quantum Matter Seminar

    Speaker: Liujun Zou (Perimeter Institute)

    Title: Landscape of quantum phases in quantum materials

    Abstract: A central goal of condensed matter physics is to understand which quantum phases of matter can emerge in a quantum material. For this purpose, one should be able to not only describe the quantum phases using some effective field theories, but also capture the important microscopic information of the material via mathematical formulation. In this talk, I will present a framework to classify quantum phases in quantum materials, where the microscopic information of a material is encoded in its quantum anomaly. I will talk about the application of this framework to classify various exotic quantum phases of matter in different lattice systems. Using our framework, we have obtained many results unexpected from the previous literature.

  • 03
    11/03/2023

    Symmetry and many-body topology in mixed states

    10:00 am-11:30 am
    11/03/2023
    CMSA Room G10
    CMSA, 20 Garden Street, Cambridge, MA 02138 USA

    Quantum Matter Seminar

    Speaker: Meng Cheng (Yale)

    Title: Symmetry and many-body topology in mixed states

    Abstract: It is by now well-understood that gapped ground states of local Hamiltonians can be classified topologically, and the nontrivial states exhibit many interesting topological phenomena. In this talk I’ll discuss recent developments in generalizing the topological classification to mixed states. Global symmetry plays a key role in understanding phases in pure states. For mixed states, certain “weak” symmetries may hold “on average” for the entire ensemble, in contrast to “strong” symmetries respected by each state in the ensemble. I will show that the interplay between these two kinds of symmetries lead to a rich landscape of symmetry-protected mixed states, and can also be used to characterize mixed state topological order.

     

  • 03
    11/03/2023

    Deformations of Landau-Ginzburg models and their fibers

    12:00 pm-1:00 pm
    11/03/2023
    CMSA Room G10
    CMSA, 20 Garden Street, Cambridge, MA 02138 USA

    Member Seminar

    Speaker: Zi Yang Kang

    Title: Deformations of Landau-Ginzburg models and their fibers

    Abstract: In mirror symmetry, the dual object to a Fano variety is a Landau-Ginzburg model. Broadly, a Landau-Ginzburg model is quasi-projective variety Y with a superpotential function w, but not all such pairs correspond to Fano varieties under mirror symmetry, so a very natural question to ask is: Which Landau-Ginzburg models are mirror to Fano varieties? In this talk, I will discuss a cohomological characterization of mirrors of (semi-)Fano varieties, focusing on the case of threefolds. I’ll discuss how this characterization relates to the deformation and Hodge theory of (Y,w), and in particular, how the classification of (semi-)Fano threefolds is related to questions about moduli spaces of lattice polarized K3 surfaces.

< 2023 >
November
«
»
  • 01
    11/01/2023

    SPACETIME AND QUANTUM MECHANICS, TOTAL POSITIVITY AND MOTIVES

    9:48 pm
    11/01/2023-12/31/2010

    Recent developments have poised this area to make serious advances in 2019, and we feel that bringing together many of the relevant experts for an intensive semester of discussions and collaboration will trigger some great things to happen. To this end, the organizers will host a small workshop during fall 2019, with between 20-30 participants. They will also invite 10-20 longer-term visitors throughout the semester. Additionally, there will be a seminar held weekly on Thursdays at 2:30pm in CMSA G10.

    Organizers:

    .

    Workshops:

     

    Here is a partial list of the mathematicians and physicists who have indicated that they will attend part or all of this special program as a visitor:

  • 01
    11/01/2023

    Mathematical Biology

    9:45 pm-9:46 pm
    11/01/2023-12/31/2010

    During Academic year 2018-19, the CMSA will be hosting a Program on Mathematical Biology.

    Just over a century ago, the biologist, mathematician and philologist D’Arcy Thompson wrote “On growth and form”. The book was a visionary synthesis of the geometric biology of form at the time. It also served as a call for mathematical and physical approaches to understanding the evolution and development of shape.

    In the century since its publication, we have seen a revolution in biology following the discovery of the genetic code, which has uncovered the molecular and cellular basis for life, combined with the ability to probe the chemical, structural, and dynamical nature of molecules, cells, tissues and organs across scales. In parallel, we have seen a blossoming of our understanding of spatiotemporal patterning in physical systems, and a gradual unveiling of the complexity of physical form. And in mathematics and computation, there has been a revolution in terms of posing and solving problems at the intersection of computational geometry, statistics and inference.  So, how far are we from realizing a descriptive, predictive and controllable theory of biological shape?

    In Fall 2018, CMSA will focus on a program that aims at recent mathematical advances in describing shape using geometry and statistics in a biological context, while also considering a range of physical theories that can predict biological shape at scales ranging from macromolecular assemblies to whole organ systems

    The CMSA will be hosting three workshops as part of this program. The Workshop on Morphometrics, Morphogenesis and Mathematics will take place on October 22-26. 

    A workshop on Morphogenesis: Geometry and Physics will take place on December 3-6, 2018.

    A workshop on Invariance and Geometry in Sensation, Action and Cognition will take place on April 15-17, 2019.

  • 01
    11/01/2023

    THE SIMONS COLLABORATION IN HOMOLOGICAL MIRROR SYMMETRY

    9:49 pm
    11/01/2023-12/23/2010

    The Simons Collaboration program in Homological Mirror Symmetry at Harvard CMSA and Brandeis University is part of the bigger Simons collaboration program on Homological mirror symmetry (https://schms.math.berkeley.edu) which brings to CMSA experts on algebraic geometry, Symplectic geometry, Arithmetic geometry, Quantum topology and mathematical aspects of high energy physics, specially string theory with the goal of proving the homological mirror symmetry conjecture (HMS) in full generality and explore its applications. Mirror symmetry, which emerged in the late 1980s as an unexpected physical duality between quantum field theories, has been a major source of progress in mathematics. At the 1994 ICM, Kontsevich reinterpreted mirror symmetry as a deep categorical duality: the HMS conjecture states that the derived category of coherent sheaves of a smooth projective variety is equivalent to the Fukaya category of a mirror symplectic manifold (or Landau-Ginzburg model). We are happy to announce that the Simons Foundation has agreed to renew funding for the HMS collaboration program for three additional years.

    A brief induction of the Brandeis-Harvard CMSA HMS/SYZ research agenda and team members are as follow:


    Directors:


    Shing-Tung Yau (Harvard University)

    Born in Canton, China, in 1949, S.-T. Yau grew up in Hong Kong, and studied in the Chinese University of Hong Kong from 1966 to 1969. He did his PhD at UC Berkeley from 1969 to 1971, as a student of S.S. Chern. He spent a year as a postdoc at the Institute for Advanced Study in Princeton, and a year as assistant professor at SUNY at Stony Brook. He joined the faculty at Stanford in 1973. On a Sloan Fellowship, he spent a semester at the Courant Institute in 1975. He visited UCLA the following year, and was offered a professorship at UC Berkeley in 1977. He was there for a year, before returning to Stanford. He was a plenary speaker at the 1978 ICM in Helsinki. The following year, he became a faculty member at the IAS in Princeton. He moved to UCSD in 1984. Yau came to Harvard in 1987, and was appointed the Higgins Professor of Mathematics in 1997. He has been at Harvard ever since. Yau has received numerous prestigious awards and honors throughout his career. He was named a California Scientist of the Year in 1979. In 1981, he received a Oswald Veblen Prize in Geometry and a John J. Carty Award for the Advancement of Science, and was elected a member of the US National Academy of Sciences. In 1982, he received a Fields Medal for “his contributions to partial differential equations, to the Calabi conjecture in algebraic geometry, to the positive mass conjecture of general relativity theory, and to real and complex MongeAmpre equations”. He was named Science Digest, America’s 100 Brightest Scientists under 40, in 1984. In 1991, he received a Humboldt Research Award from the Alexander von Humboldt Foundation in Germany. He was awarded a Crafoord Prize in 1994, a US National Medal of Science in 1997, and a China International Scientific and Technological Cooperation Award, for “his outstanding contribution to PRC in aspects of making progress in sciences and technology, training researchers” in 2003. In 2010, he received a Wolf Prize in Mathematics, for “his work in geometric analysis and mathematical physics”. Yau has also received a number of research fellowships, which include a Sloan Fellowship in 1975-1976, a Guggenheim Fellowship in 1982, and a MacArthur Fellowship in 1984-1985. Yau’s research interests include differential and algebraic geometry, topology, and mathematical physics. As a graduate student, he started to work on geometry of manifolds with negative curvature. He later became interested in developing the subject of geometric analysis, and applying the theory of nonlinear partial differential equations to solve problems in geometry, topology, and physics. His work in this direction include constructions of minimal submanifolds, harmonic maps, and canonical metrics on manifolds. The most notable, and probably the most influential of this, was his solution of the Calabi conjecture on Ricci flat metrics, and the existence of Kahler-Einstein metrics. He has also succeeded in applying his theory to solve a number of outstanding conjectures in algebraic geometry, including Chern number inequalities, and the rigidity of complex structures of complex projective spaces. Yau’s solution to the Calabi conjecture has been remarkably influential in mathematical physics over the last 30 years, through the creation of the theory of Calabi-Yau manifolds, a theory central to mirror symmetry. He and a team of outstanding mathematicians trained by him, have developed many important tools and concepts in CY geometry and mirror symmetry, which have led to significant progress in deformation theory, and on outstanding problems in enumerative geometry. Lian, Yau and his postdocs have developed a systematic approach to study and compute period integrals of CY and general type manifolds. Lian, Liu and Yau (independently by Givental) gave a proof of the counting formula of Candelas et al for worldsheet instantons on the quintic threefold. In the course of understanding mirror symmetry, Strominger, Yau, and Zaslow proposed a new geometric construction of mirror symmetry, now known as the SYZ construction. This has inspired a rapid development in CY geometry over the last two decades. In addition to CY geometry and mirror symmetry, Yau has done influential work on nonlinear partial differential equations, generalized geometry, Kahler geometry, and general relativity. His proof of positive mass conjecture is a widely regarded as a cornerstone in the classical theory of general relativity. In addition to publishing well over 350 research papers, Yau has trained more than 60 PhD students in a broad range of fields, and mentored dozens of postdoctoral fellows over the last 40 years.


    Professor Bong Lian (Brandeis University)

    BongBorn in Malaysia in 1962, Bong Lian completed his PhD in physics at Yale University under the direction of G. Zuckerman in 1991. He joined the permanent faculty at Brandeis University in 1995, and has remained there since. Between 1995 and 2013, he had had visiting research positions at numerous places, including the National University of Taiwan, Harvard University, and Tsinghua University. Lian received a J.S. Guggenheim Fellowship in 2003. He was awarded a Chern Prize at the ICCM in Taipei in 2013, for his “influential and fundamental contributions in mathematical physics, in particular in the theory of vertex algebras and mirror symmetry.” He has also been co-Director, since 2014, of the Tsinghua Mathcamp, a summer outreach program launched by him and Yau for mathematically talented teenagers in China. Since 2008, Lian has been the President of the International Science Foundation of Cambridge, a non-profit whose stated mission is “to provide financial and logistical support to scholars and universities, to promote basic research and education in mathematical sciences, especially in the Far East.” Over the last 20 years, he has mentored a number of postdocs and PhD students. His research has been supported by an NSF Focused Research Grant since 2009. Published in well over 60 papers over 25 years, Lian’s mathematical work lies in the interface between representation theory, Calabi-Yau geometry, and string theory. Beginning in the late 80’s, Lian, jointly with Zuckerman, developed the theory of semi-infinite cohomology and applied it to problems in string theory. In 1994, he constructed a new invariant (now known as the Lian- Zuckerman algebra) of a topological vertex algebra, and conjectured the first example of a G algebra in vertex algebra theory. The invariant has later inspired a new construction of quantum groups by I. Frenkel and A. Zeitlin, as semi-infinite cohomology of braided vertex algebras, and led to a more recent discovery of new relationships between Courant algebroids, A-algebras, operads, and deformation theory of BV algebras. In 2010, he and his students Linshaw and Song developed important applications of vertex algebras in equivariant topology. Lian’s work in CY geometry and mirror symmetry began in early 90’s. Using a characteristic p version of higher order Schwarzian equations, Lian and Yau gave an elementary proof that the instanton formula of Candelas et al implies Clemens’s divisibility conjecture for the quintic threefold, for infinitely many degrees. In 1996, Lian (jointly with Hosono and Yau) answered the so-called Large Complex Structure Limit problem in the affirmative in many important cases. Around the same year, they announced their hyperplane conjecture, which gives a general formula for period integrals for a large class of CY manifolds, extending the formula of Candelas et al. Soon after, Lian, Liu and Yau (independently by Givental) gave a proof of the counting formula. In 2003, inspired by mirror symmetry, Lian (jointly with Hosono, Oguiso and Yau) discovered an explicit counting formula for Fourier-Mukai partners, and settled an old problem of Shioda on abelian and K3 surfaces. Between 2009 and 2014, Lian (jointly with Bloch, Chen, Huang, Song, Srinivas, Yau, and Zhu) developed an entirely new approach to study the so-called Riemann-Hilbert problem for period integrals of CY manifolds, and extended it to general type manifolds. The approach leads to an explicit description of differential systems for period integrals with many applications. In particular, he answered an old question in physics on the completeness of Picard-Fuchs systems, and constructed new differential zeros of hypergeometric functions.


    Denis Auroux (Harvard University)

    AurouxDenis Auroux’s research concerns symplectic geometry and its applications to mirror symmetry. While his early work primarily concerned the topology of symplectic 4-manifolds, over the past decade Auroux has obtained pioneering results on homological mirror symmetry outside of the Calabi-Yau setting (for Fano varieties, open Riemann surfaces, etc.), and developed an extension of the SYZ approach to non-Calabi-Yau spaces.After obtaining his PhD in 1999 from Ecole Polytechnique (France), Auroux was employed as Chargé de Recherche at CNRS and CLE Moore Instructor at MIT, before joining the faculty at MIT in 2002 (as Assistant Professor from 2002 to 2004, and as Associate Professor from 2004 to 2009, with tenure starting in 2006). He then moved to UC Berkeley as a Full Professor in 2009.
    Auroux has published over 30 peer-reviewed articles, including several in top journals, and given 260 invited presentations about his work. He received an Alfred P. Sloan Research Fellowship in 2005, was an invited speaker at the 2010 International Congress of Mathematicians, and in 2014 he was one of the two inaugural recipients of the Poincaré Chair at IHP. He has supervised 10 PhD dissertations, won teaching awards at MIT and Berkeley, and participated in the organization of over 20 workshops and conferences in symplectic geometry and mirror symmetry.




    Senior Personnel:

    Artan Sheshmani (Harvard CMSA)

    unnamedArtan Sheshmani’s research is focused on enumerative algebraic geometry and mathematical aspects of string theory. He is interested in applying techniques in algebraic geometry, such as, intersection theory, derived category theory, and derived algebraic geometry to construct and compute the deformation invariants of algebraic varieties, in particular Gromov-Witten (GW) or Donaldson-Thomas (DT) invariants. In the past Professor Sheshmani has worked on proving modularity property of certain DT invariants of K3-fibered threefolds (as well as their closely related Pandharipande-Thomas (PT) invariants), local surface threefolds, and general complete intersection Calabi-Yau threefolds. The modularity of DT/PT invariants in this context is predicted in a famous conjecture of  string theory called S-duality modularity conjecture, and his joint work has provided the proof to some cases of it, using degenerations, virtual localizations, as well as wallcrossing techniques. Recently, Sheshmani has focused on proving a series of dualities relating the various enumerative invariants over threefolds, notably the GW invariants and invariants that arise in topological gauge theory. In particular in his joint work with Gholampour, Gukov, Liu, Yau he studied DT gauge theory and its reductions to D=4 and D=2 which are equivalent to local theory of surfaces in Calabi-Yau threefolds. Moreover, in a recent joint work with Yau and Diaconescu, he has studied the construction and computation of DT invariants of Calabi-Yau fourfolds via a suitable derived categorical reduction of the theory to the DT theory of threefolds. Currently Sheshmani is interested in a wide range of problems in enumerative geometry of CY varieties in dimensions 3,4,5.

    Artan has received his PhD and Master’s degrees in pure mathematics under Sheldon Katz and Thomas Nevins from the University of Illinois at Urbana Champaign (USA) in 2011 and 2008 respectively. He holds a Master’s degree in Solid Mechanics (2004) and two Bachelor’s degrees, in Mechanical Engineering and Civil Engineering from the Sharif University of Technology, Tehran, Iran.  Artan has been a tenured Associate Professor of Mathematics with joint affiliation at Harvard CMSA and center for Quantum Geometry of Moduli Spaces (QGM), since 2016. Before that he has held visiting Associate Professor and visiting Assistant Professor positions at MIT.

    An Huang (Brandeis University)

    unnamedThe research of An Huang since 2011 has been focused on the interplay between algebraic geometry, the theory of special functions and mirror symmetry. With S. Bloch, B. Lian, V. Srinivas, S.-T. Yau, X. Zhu, he has developed the theory of tautological systems, and has applied it to settle several important problems concerning period integrals in relation to mirror symmetry. With B. Lian and X. Zhu, he has given a precise geometric interpretation of all solutions to GKZ systems associated to Calabi-Yau hypersurfaces in smooth Fano toric varieties. With B. Lian, S.-T. Yau, and C.-L. Yu, he has proved a conjecture of Vlasenko concerning an explicit formula for unit roots of the zeta functions of hypersurfaces, and has further related these roots to p-adic interpolations of complex period integrals. Beginning in 2018, with B. Stoica and S.-T. Yau, he has initiated the study of p-adic strings in curved spacetime, and showed that general relativity is a consequence of the self-consistency of quantum p-adic strings. One of the goals of this study is to understand p-adic A and B models.

    An Huang received his PhD in Mathematics from the University of California at Berkeley in 2011. He was a postdoctoral fellow at the Harvard University Mathematics Department, and joined Brandeis University as an Assistant Professor in Mathematics in 2016.



    Siu Cheong Lau (Boston University)
    unnamed

    The research interest of Siu Cheong Lau lies in SYZ mirror symmetry, symplectic and algebraic geometry.  His thesis work has successfully constructed the SYZ mirrors for all toric Calabi-Yau manifolds based on quantum corrections by open Gromov-Witten invariants and their wall-crossing phenomenon.  In collaboration with N.C. Leung, H.H. Tseng and K. Chan, he derived explicit formulas for the open Gromov-Witten invariants for semi-Fano toric manifolds which have an obstructed moduli theory.  It has a beautiful relation with mirror maps and Seidel representations.   Recently he works on a local-to-global approach to SYZ mirror symmetry.  In joint works with C.H. Cho and H. Hong, he developed a noncommutative local mirror construction for immersed Lagrangians, and a natural gluing method to construct global mirrors.  The construction has been realized in various types of geometries including orbifolds, focus-focus singularities and pair-of-pants decompositions of Riemann surfaces.

    Siu-Cheong Lau has received the Doctoral Thesis Gold Award (2012) and the Best Paper Silver Award (2017) at the International Congress of Chinese Mathematicians.  He was awarded the Simons Collaboration Grant in 2018.  He received a Certificate of Teaching Excellence from Harvard University in 2014.


    Affiliates:

    • Netanel Rubin-Blaier (Cambridge)
    • Kwokwai Chan (Chinese University of Hong Kong)
    • Mandy Cheung (Harvard University, BP)
    • Chuck Doran (University of Alberta)
    • Honsol Hong (Yonsei University)
    • Shinobu Hosono (Gakushuin University, Japan)
    • Conan Leung (Chinese University of Hong Kong)
    • Yu-shen Lin (Boston University)
    • Hossein Movassati (IMPA Brazil)
    • Arnav Tripathhy (Harvard University, BP)

     

    Postdocs:

    • Dennis Borisov
    • Tsung-Ju Lee
    • Dingxin Zhang
    • Jingyu Zhao
    • Yang Zhou

    Jobs:

    Postdoctoral Fellowship in Algebraic Geometry

    Postdoctoral Fellowship in Mathematical Sciences

     

    To learn about previous programming as part of the Simons Collaboration, click here.

  • 01
    11/01/2023

    TOPOLOGICAL ASPECTS OF CONDENSED MATTER

    9:44 pm
    11/01/2023-12/28/2013

    During Academic year 2018-19, the CMSA will be hosting a Program on Topological Aspects of Condensed Matter. New ideas rooted in topology have recently had a big impact on condensed matter physics, and have highlighted new connections with high energy physics, mathematics and quantum information theory. Additionally, these ideas have found applications in the design of photonic systems and of materials with novel mechanical properties. The aim of this program will be to deepen these connections by foster discussion and seeding new collaborations within and across disciplines.

    As part of the Program, the CMSA will be hosting two workshops:

    .

    Additionally, a weekly Topology Seminar will be held on Mondays from 10:00-11:30pm in CMSA room G10.

    Here is a partial list of the mathematicians who have indicated that they will attend part or all of this special program
    NameTentative Visiting Dates

    Jason Alicea

    11/12/2018-11/16/2018
    Maissam Barkeshli4/22/2019 – 4/26/2019
    Xie Chen4/15-17/2019 4/19-21/2019 4/24-30/2019

    Lukasz Fidkowski

    1/7/2019-1/11/2019

    Zhengcheng Gu

    8/15/2018-8/30/2018 & 5/9/2019-5/19/2019

    Yin Chen He

    10/14/2018-10/27/2018
    Anton Kapustin8/26/2018-8/30/2018 & 3/28/2019-4/5/2019

    Michael Levin

    3/11/2019-3/15/2019
    Yuan-Ming Lu4/29/2019-6/01/2019

    Adam Nahum

    4/2/2019- 4/19/2019

    Masaki Oshikawa

    4/22/2019-5/22/2019
    Chong Wang 10/22/2018-11/16/2018

    Juven Wang

    4/1/2019-4/16/2019
    Cenke Xu 8/26/2018-10/1/2018

    Yi-Zhuang You

    4/1/2019-4/19/2019

    Mike Zaletel

    5/1/2019-5/10/2019
  • 01
    11/01/2023

    Topological Insulators and Mathematical Science – Conference and Program

    2:00 pm-7:00 pm
    11/01/2023-09/17/2014

    The CMSA will be hosting a conference on the subject of topological insulators and mathematical science on September 15-17.  Seminars will take place each day from 2:00-7:00pm in Science Center Hall D, 1 Oxford Street, Cambridge, MA.

< 2023 >
November
«
»
  • 28
    11/28/2023

    Remarkable symmetries of rotating black holes

    11:00 am-12:00 pm
    11/28/2023
    CMSA, 20 Garden St, G10
    20 Garden Street, Cambridge, MA 02138 USA

    General Relativity Seminar

    Speaker: David Kubiznak (Charles University)

    Title: Remarkable symmetries of rotating black holes

    Abstract: It is well known that the Kerr geometry admits a non-trivial Killing tensor and its ‘square root’ known as the Killing-Yano tensor. These two objects stand behind Carter’s constant of geodesic motion as well as allow for separability of test field equations in this background. The situation is even more remarkable in higher dimensions, where a single object — the principal Killing-Yano tensor — generates a tower of explicit and hidden symmetries responsible for integrability of geodesics and separability of test fields around higher-dimensional rotating black holes. Interestingly, similar yet different structure is already present for the slowly rotating black holes described by the `magic square’ version of the Lense-Thirring solution, giving rise to a geometrically preferred spacetime that can be cast in the Painleve-Gullstrand form and admits a tower of exact rank-2 and higher rank Killing tensors whose number rapidly grows with the number of spacetime dimensions.

  • 28
    11/28/2023

    A random matrix model towards the quantum chaos transition conjecture

    12:00 pm-1:00 pm
    11/28/2023

    Probability Seminar

    Speaker: Jun Yin (UCLA)

    Title: A random matrix model towards the quantum chaos transition conjecture

    Abstract: The Quantum Chaos Conjecture has long fascinated researchers, postulating a critical spectrum phase transition that separates integrable systems from chaotic systems in quantum mechanics. In the realm of integrable systems, eigenvectors remain localized, and local eigenvalue statistics follow the Poisson distribution. Conversely, chaotic systems exhibit delocalized eigenvectors, with local eigenvalue statistics mirroring the Sine kernel distribution, akin to the standard random matrix ensembles GOE/GUE.

    This talk delves into the heart of the Quantum Chaos Conjecture, presenting a novel approach through the lens of random matrix models. By utilizing these models, we aim to provide a clear and intuitive demonstration of the same phenomenon, shedding light on the intricacies of this long-standing conjecture.

  • 30
    11/30/2023

    A Gaussian convexity for logarithmic moment generating function

    4:00 pm-5:00 pm
    11/30/2023
    CMSA Room G10
    CMSA, 20 Garden Street, Cambridge, MA 02138 USA

    Probability Seminar

    Speaker: Wei-Kuo Chen (University of Minnesota)

    Title: A Gaussian convexity for logarithmic moment generating function

    Abstract: Convex functions of Gaussian vectors are prominent objectives in many fields of mathematical studies. In this talk, I will establish a new convexity for the logarithmic moment generating function for this object and draw two consequences. The first leads to the Paouris-Valettas small deviation inequality that arises from the study of convex geometry. The second provides a quantitative bound for the Dotsenko-Franz-Mezard conjecture in the Sherrington-Kirkpatrick mean-field spin glass model, which states that the logarithmic anneal partition function of negative replica is asymptotically equal to the free energy.

     

< 2023 >
November
«
»
  • 01
    11/01/2023

    SPACETIME AND QUANTUM MECHANICS, TOTAL POSITIVITY AND MOTIVES

    9:48 pm
    11/01/2023-12/31/2010

    Recent developments have poised this area to make serious advances in 2019, and we feel that bringing together many of the relevant experts for an intensive semester of discussions and collaboration will trigger some great things to happen. To this end, the organizers will host a small workshop during fall 2019, with between 20-30 participants. They will also invite 10-20 longer-term visitors throughout the semester. Additionally, there will be a seminar held weekly on Thursdays at 2:30pm in CMSA G10.

    Organizers:

    .

    Workshops:

     

    Here is a partial list of the mathematicians and physicists who have indicated that they will attend part or all of this special program as a visitor:

  • 01
    11/01/2023

    Mathematical Biology

    9:45 pm-9:46 pm
    11/01/2023-12/31/2010

    During Academic year 2018-19, the CMSA will be hosting a Program on Mathematical Biology.

    Just over a century ago, the biologist, mathematician and philologist D’Arcy Thompson wrote “On growth and form”. The book was a visionary synthesis of the geometric biology of form at the time. It also served as a call for mathematical and physical approaches to understanding the evolution and development of shape.

    In the century since its publication, we have seen a revolution in biology following the discovery of the genetic code, which has uncovered the molecular and cellular basis for life, combined with the ability to probe the chemical, structural, and dynamical nature of molecules, cells, tissues and organs across scales. In parallel, we have seen a blossoming of our understanding of spatiotemporal patterning in physical systems, and a gradual unveiling of the complexity of physical form. And in mathematics and computation, there has been a revolution in terms of posing and solving problems at the intersection of computational geometry, statistics and inference.  So, how far are we from realizing a descriptive, predictive and controllable theory of biological shape?

    In Fall 2018, CMSA will focus on a program that aims at recent mathematical advances in describing shape using geometry and statistics in a biological context, while also considering a range of physical theories that can predict biological shape at scales ranging from macromolecular assemblies to whole organ systems

    The CMSA will be hosting three workshops as part of this program. The Workshop on Morphometrics, Morphogenesis and Mathematics will take place on October 22-26. 

    A workshop on Morphogenesis: Geometry and Physics will take place on December 3-6, 2018.

    A workshop on Invariance and Geometry in Sensation, Action and Cognition will take place on April 15-17, 2019.

  • 01
    11/01/2023

    THE SIMONS COLLABORATION IN HOMOLOGICAL MIRROR SYMMETRY

    9:49 pm
    11/01/2023-12/23/2010

    The Simons Collaboration program in Homological Mirror Symmetry at Harvard CMSA and Brandeis University is part of the bigger Simons collaboration program on Homological mirror symmetry (https://schms.math.berkeley.edu) which brings to CMSA experts on algebraic geometry, Symplectic geometry, Arithmetic geometry, Quantum topology and mathematical aspects of high energy physics, specially string theory with the goal of proving the homological mirror symmetry conjecture (HMS) in full generality and explore its applications. Mirror symmetry, which emerged in the late 1980s as an unexpected physical duality between quantum field theories, has been a major source of progress in mathematics. At the 1994 ICM, Kontsevich reinterpreted mirror symmetry as a deep categorical duality: the HMS conjecture states that the derived category of coherent sheaves of a smooth projective variety is equivalent to the Fukaya category of a mirror symplectic manifold (or Landau-Ginzburg model). We are happy to announce that the Simons Foundation has agreed to renew funding for the HMS collaboration program for three additional years.

    A brief induction of the Brandeis-Harvard CMSA HMS/SYZ research agenda and team members are as follow:


    Directors:


    Shing-Tung Yau (Harvard University)

    Born in Canton, China, in 1949, S.-T. Yau grew up in Hong Kong, and studied in the Chinese University of Hong Kong from 1966 to 1969. He did his PhD at UC Berkeley from 1969 to 1971, as a student of S.S. Chern. He spent a year as a postdoc at the Institute for Advanced Study in Princeton, and a year as assistant professor at SUNY at Stony Brook. He joined the faculty at Stanford in 1973. On a Sloan Fellowship, he spent a semester at the Courant Institute in 1975. He visited UCLA the following year, and was offered a professorship at UC Berkeley in 1977. He was there for a year, before returning to Stanford. He was a plenary speaker at the 1978 ICM in Helsinki. The following year, he became a faculty member at the IAS in Princeton. He moved to UCSD in 1984. Yau came to Harvard in 1987, and was appointed the Higgins Professor of Mathematics in 1997. He has been at Harvard ever since. Yau has received numerous prestigious awards and honors throughout his career. He was named a California Scientist of the Year in 1979. In 1981, he received a Oswald Veblen Prize in Geometry and a John J. Carty Award for the Advancement of Science, and was elected a member of the US National Academy of Sciences. In 1982, he received a Fields Medal for “his contributions to partial differential equations, to the Calabi conjecture in algebraic geometry, to the positive mass conjecture of general relativity theory, and to real and complex MongeAmpre equations”. He was named Science Digest, America’s 100 Brightest Scientists under 40, in 1984. In 1991, he received a Humboldt Research Award from the Alexander von Humboldt Foundation in Germany. He was awarded a Crafoord Prize in 1994, a US National Medal of Science in 1997, and a China International Scientific and Technological Cooperation Award, for “his outstanding contribution to PRC in aspects of making progress in sciences and technology, training researchers” in 2003. In 2010, he received a Wolf Prize in Mathematics, for “his work in geometric analysis and mathematical physics”. Yau has also received a number of research fellowships, which include a Sloan Fellowship in 1975-1976, a Guggenheim Fellowship in 1982, and a MacArthur Fellowship in 1984-1985. Yau’s research interests include differential and algebraic geometry, topology, and mathematical physics. As a graduate student, he started to work on geometry of manifolds with negative curvature. He later became interested in developing the subject of geometric analysis, and applying the theory of nonlinear partial differential equations to solve problems in geometry, topology, and physics. His work in this direction include constructions of minimal submanifolds, harmonic maps, and canonical metrics on manifolds. The most notable, and probably the most influential of this, was his solution of the Calabi conjecture on Ricci flat metrics, and the existence of Kahler-Einstein metrics. He has also succeeded in applying his theory to solve a number of outstanding conjectures in algebraic geometry, including Chern number inequalities, and the rigidity of complex structures of complex projective spaces. Yau’s solution to the Calabi conjecture has been remarkably influential in mathematical physics over the last 30 years, through the creation of the theory of Calabi-Yau manifolds, a theory central to mirror symmetry. He and a team of outstanding mathematicians trained by him, have developed many important tools and concepts in CY geometry and mirror symmetry, which have led to significant progress in deformation theory, and on outstanding problems in enumerative geometry. Lian, Yau and his postdocs have developed a systematic approach to study and compute period integrals of CY and general type manifolds. Lian, Liu and Yau (independently by Givental) gave a proof of the counting formula of Candelas et al for worldsheet instantons on the quintic threefold. In the course of understanding mirror symmetry, Strominger, Yau, and Zaslow proposed a new geometric construction of mirror symmetry, now known as the SYZ construction. This has inspired a rapid development in CY geometry over the last two decades. In addition to CY geometry and mirror symmetry, Yau has done influential work on nonlinear partial differential equations, generalized geometry, Kahler geometry, and general relativity. His proof of positive mass conjecture is a widely regarded as a cornerstone in the classical theory of general relativity. In addition to publishing well over 350 research papers, Yau has trained more than 60 PhD students in a broad range of fields, and mentored dozens of postdoctoral fellows over the last 40 years.


    Professor Bong Lian (Brandeis University)

    BongBorn in Malaysia in 1962, Bong Lian completed his PhD in physics at Yale University under the direction of G. Zuckerman in 1991. He joined the permanent faculty at Brandeis University in 1995, and has remained there since. Between 1995 and 2013, he had had visiting research positions at numerous places, including the National University of Taiwan, Harvard University, and Tsinghua University. Lian received a J.S. Guggenheim Fellowship in 2003. He was awarded a Chern Prize at the ICCM in Taipei in 2013, for his “influential and fundamental contributions in mathematical physics, in particular in the theory of vertex algebras and mirror symmetry.” He has also been co-Director, since 2014, of the Tsinghua Mathcamp, a summer outreach program launched by him and Yau for mathematically talented teenagers in China. Since 2008, Lian has been the President of the International Science Foundation of Cambridge, a non-profit whose stated mission is “to provide financial and logistical support to scholars and universities, to promote basic research and education in mathematical sciences, especially in the Far East.” Over the last 20 years, he has mentored a number of postdocs and PhD students. His research has been supported by an NSF Focused Research Grant since 2009. Published in well over 60 papers over 25 years, Lian’s mathematical work lies in the interface between representation theory, Calabi-Yau geometry, and string theory. Beginning in the late 80’s, Lian, jointly with Zuckerman, developed the theory of semi-infinite cohomology and applied it to problems in string theory. In 1994, he constructed a new invariant (now known as the Lian- Zuckerman algebra) of a topological vertex algebra, and conjectured the first example of a G algebra in vertex algebra theory. The invariant has later inspired a new construction of quantum groups by I. Frenkel and A. Zeitlin, as semi-infinite cohomology of braided vertex algebras, and led to a more recent discovery of new relationships between Courant algebroids, A-algebras, operads, and deformation theory of BV algebras. In 2010, he and his students Linshaw and Song developed important applications of vertex algebras in equivariant topology. Lian’s work in CY geometry and mirror symmetry began in early 90’s. Using a characteristic p version of higher order Schwarzian equations, Lian and Yau gave an elementary proof that the instanton formula of Candelas et al implies Clemens’s divisibility conjecture for the quintic threefold, for infinitely many degrees. In 1996, Lian (jointly with Hosono and Yau) answered the so-called Large Complex Structure Limit problem in the affirmative in many important cases. Around the same year, they announced their hyperplane conjecture, which gives a general formula for period integrals for a large class of CY manifolds, extending the formula of Candelas et al. Soon after, Lian, Liu and Yau (independently by Givental) gave a proof of the counting formula. In 2003, inspired by mirror symmetry, Lian (jointly with Hosono, Oguiso and Yau) discovered an explicit counting formula for Fourier-Mukai partners, and settled an old problem of Shioda on abelian and K3 surfaces. Between 2009 and 2014, Lian (jointly with Bloch, Chen, Huang, Song, Srinivas, Yau, and Zhu) developed an entirely new approach to study the so-called Riemann-Hilbert problem for period integrals of CY manifolds, and extended it to general type manifolds. The approach leads to an explicit description of differential systems for period integrals with many applications. In particular, he answered an old question in physics on the completeness of Picard-Fuchs systems, and constructed new differential zeros of hypergeometric functions.


    Denis Auroux (Harvard University)

    AurouxDenis Auroux’s research concerns symplectic geometry and its applications to mirror symmetry. While his early work primarily concerned the topology of symplectic 4-manifolds, over the past decade Auroux has obtained pioneering results on homological mirror symmetry outside of the Calabi-Yau setting (for Fano varieties, open Riemann surfaces, etc.), and developed an extension of the SYZ approach to non-Calabi-Yau spaces.After obtaining his PhD in 1999 from Ecole Polytechnique (France), Auroux was employed as Chargé de Recherche at CNRS and CLE Moore Instructor at MIT, before joining the faculty at MIT in 2002 (as Assistant Professor from 2002 to 2004, and as Associate Professor from 2004 to 2009, with tenure starting in 2006). He then moved to UC Berkeley as a Full Professor in 2009.
    Auroux has published over 30 peer-reviewed articles, including several in top journals, and given 260 invited presentations about his work. He received an Alfred P. Sloan Research Fellowship in 2005, was an invited speaker at the 2010 International Congress of Mathematicians, and in 2014 he was one of the two inaugural recipients of the Poincaré Chair at IHP. He has supervised 10 PhD dissertations, won teaching awards at MIT and Berkeley, and participated in the organization of over 20 workshops and conferences in symplectic geometry and mirror symmetry.




    Senior Personnel:

    Artan Sheshmani (Harvard CMSA)

    unnamedArtan Sheshmani’s research is focused on enumerative algebraic geometry and mathematical aspects of string theory. He is interested in applying techniques in algebraic geometry, such as, intersection theory, derived category theory, and derived algebraic geometry to construct and compute the deformation invariants of algebraic varieties, in particular Gromov-Witten (GW) or Donaldson-Thomas (DT) invariants. In the past Professor Sheshmani has worked on proving modularity property of certain DT invariants of K3-fibered threefolds (as well as their closely related Pandharipande-Thomas (PT) invariants), local surface threefolds, and general complete intersection Calabi-Yau threefolds. The modularity of DT/PT invariants in this context is predicted in a famous conjecture of  string theory called S-duality modularity conjecture, and his joint work has provided the proof to some cases of it, using degenerations, virtual localizations, as well as wallcrossing techniques. Recently, Sheshmani has focused on proving a series of dualities relating the various enumerative invariants over threefolds, notably the GW invariants and invariants that arise in topological gauge theory. In particular in his joint work with Gholampour, Gukov, Liu, Yau he studied DT gauge theory and its reductions to D=4 and D=2 which are equivalent to local theory of surfaces in Calabi-Yau threefolds. Moreover, in a recent joint work with Yau and Diaconescu, he has studied the construction and computation of DT invariants of Calabi-Yau fourfolds via a suitable derived categorical reduction of the theory to the DT theory of threefolds. Currently Sheshmani is interested in a wide range of problems in enumerative geometry of CY varieties in dimensions 3,4,5.

    Artan has received his PhD and Master’s degrees in pure mathematics under Sheldon Katz and Thomas Nevins from the University of Illinois at Urbana Champaign (USA) in 2011 and 2008 respectively. He holds a Master’s degree in Solid Mechanics (2004) and two Bachelor’s degrees, in Mechanical Engineering and Civil Engineering from the Sharif University of Technology, Tehran, Iran.  Artan has been a tenured Associate Professor of Mathematics with joint affiliation at Harvard CMSA and center for Quantum Geometry of Moduli Spaces (QGM), since 2016. Before that he has held visiting Associate Professor and visiting Assistant Professor positions at MIT.

    An Huang (Brandeis University)

    unnamedThe research of An Huang since 2011 has been focused on the interplay between algebraic geometry, the theory of special functions and mirror symmetry. With S. Bloch, B. Lian, V. Srinivas, S.-T. Yau, X. Zhu, he has developed the theory of tautological systems, and has applied it to settle several important problems concerning period integrals in relation to mirror symmetry. With B. Lian and X. Zhu, he has given a precise geometric interpretation of all solutions to GKZ systems associated to Calabi-Yau hypersurfaces in smooth Fano toric varieties. With B. Lian, S.-T. Yau, and C.-L. Yu, he has proved a conjecture of Vlasenko concerning an explicit formula for unit roots of the zeta functions of hypersurfaces, and has further related these roots to p-adic interpolations of complex period integrals. Beginning in 2018, with B. Stoica and S.-T. Yau, he has initiated the study of p-adic strings in curved spacetime, and showed that general relativity is a consequence of the self-consistency of quantum p-adic strings. One of the goals of this study is to understand p-adic A and B models.

    An Huang received his PhD in Mathematics from the University of California at Berkeley in 2011. He was a postdoctoral fellow at the Harvard University Mathematics Department, and joined Brandeis University as an Assistant Professor in Mathematics in 2016.



    Siu Cheong Lau (Boston University)
    unnamed

    The research interest of Siu Cheong Lau lies in SYZ mirror symmetry, symplectic and algebraic geometry.  His thesis work has successfully constructed the SYZ mirrors for all toric Calabi-Yau manifolds based on quantum corrections by open Gromov-Witten invariants and their wall-crossing phenomenon.  In collaboration with N.C. Leung, H.H. Tseng and K. Chan, he derived explicit formulas for the open Gromov-Witten invariants for semi-Fano toric manifolds which have an obstructed moduli theory.  It has a beautiful relation with mirror maps and Seidel representations.   Recently he works on a local-to-global approach to SYZ mirror symmetry.  In joint works with C.H. Cho and H. Hong, he developed a noncommutative local mirror construction for immersed Lagrangians, and a natural gluing method to construct global mirrors.  The construction has been realized in various types of geometries including orbifolds, focus-focus singularities and pair-of-pants decompositions of Riemann surfaces.

    Siu-Cheong Lau has received the Doctoral Thesis Gold Award (2012) and the Best Paper Silver Award (2017) at the International Congress of Chinese Mathematicians.  He was awarded the Simons Collaboration Grant in 2018.  He received a Certificate of Teaching Excellence from Harvard University in 2014.


    Affiliates:

    • Netanel Rubin-Blaier (Cambridge)
    • Kwokwai Chan (Chinese University of Hong Kong)
    • Mandy Cheung (Harvard University, BP)
    • Chuck Doran (University of Alberta)
    • Honsol Hong (Yonsei University)
    • Shinobu Hosono (Gakushuin University, Japan)
    • Conan Leung (Chinese University of Hong Kong)
    • Yu-shen Lin (Boston University)
    • Hossein Movassati (IMPA Brazil)
    • Arnav Tripathhy (Harvard University, BP)

     

    Postdocs:

    • Dennis Borisov
    • Tsung-Ju Lee
    • Dingxin Zhang
    • Jingyu Zhao
    • Yang Zhou

    Jobs:

    Postdoctoral Fellowship in Algebraic Geometry

    Postdoctoral Fellowship in Mathematical Sciences

     

    To learn about previous programming as part of the Simons Collaboration, click here.

  • 01
    11/01/2023

    TOPOLOGICAL ASPECTS OF CONDENSED MATTER

    9:44 pm
    11/01/2023-12/28/2013

    During Academic year 2018-19, the CMSA will be hosting a Program on Topological Aspects of Condensed Matter. New ideas rooted in topology have recently had a big impact on condensed matter physics, and have highlighted new connections with high energy physics, mathematics and quantum information theory. Additionally, these ideas have found applications in the design of photonic systems and of materials with novel mechanical properties. The aim of this program will be to deepen these connections by foster discussion and seeding new collaborations within and across disciplines.

    As part of the Program, the CMSA will be hosting two workshops:

    .

    Additionally, a weekly Topology Seminar will be held on Mondays from 10:00-11:30pm in CMSA room G10.

    Here is a partial list of the mathematicians who have indicated that they will attend part or all of this special program
    NameTentative Visiting Dates

    Jason Alicea

    11/12/2018-11/16/2018
    Maissam Barkeshli4/22/2019 – 4/26/2019
    Xie Chen4/15-17/2019 4/19-21/2019 4/24-30/2019

    Lukasz Fidkowski

    1/7/2019-1/11/2019

    Zhengcheng Gu

    8/15/2018-8/30/2018 & 5/9/2019-5/19/2019

    Yin Chen He

    10/14/2018-10/27/2018
    Anton Kapustin8/26/2018-8/30/2018 & 3/28/2019-4/5/2019

    Michael Levin

    3/11/2019-3/15/2019
    Yuan-Ming Lu4/29/2019-6/01/2019

    Adam Nahum

    4/2/2019- 4/19/2019

    Masaki Oshikawa

    4/22/2019-5/22/2019
    Chong Wang 10/22/2018-11/16/2018

    Juven Wang

    4/1/2019-4/16/2019
    Cenke Xu 8/26/2018-10/1/2018

    Yi-Zhuang You

    4/1/2019-4/19/2019

    Mike Zaletel

    5/1/2019-5/10/2019
  • 01
    11/01/2023

    Topological Insulators and Mathematical Science – Conference and Program

    2:00 pm-7:00 pm
    11/01/2023-09/17/2014

    The CMSA will be hosting a conference on the subject of topological insulators and mathematical science on September 15-17.  Seminars will take place each day from 2:00-7:00pm in Science Center Hall D, 1 Oxford Street, Cambridge, MA.

< 2023 >
November
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  • 01
    11/01/2023

    Unveiling Correlated Topological Insulators through Fermionic Tensor Network States

    10:30 am-11:30 am
    11/01/2023

    Topological Quantum Matter Seminar

    Speaker: Shenghan Jiang, Kavli Institute for Theoretical Sciences UCAS

    Title: Unveiling Correlated Topological Insulators through Fermionic Tensor Network States

    Abstract: The study of topological band insulators has revealed fascinating phases characterized by band topology indices, harboring extraordinary boundary modes protected by anomalous symmetry actions. In strongly correlated systems, it has been established that topological insulator phases persist as stable phases. However, due to the inability to express the ground states of such systems as Slater determinants, the formulation of generic variational wavefunctions for numerical simulations is highly desirable.
    In this talk, we tackle this challenge by developing a comprehensive framework with fermionic tensor network states. Starting from simple assumptions, we write down tensor equations, construct edge theories and extract quantum anomaly data for topological insulators. By exhaustively exploring all possible sets of equations, we achieve a systematic classification of topological insulator phases. Imposing the solutions of a given set of equations onto local tensors, we obtain generic variational wavefunctions for corresponding topological insulator phases. Our methodology provides a crucial first step towards simulating topological insulators in strongly correlated systems.

     

  • 01
    11/01/2023

    Universality of max-margin classifiers

    3:30 pm-4:30 pm
    11/01/2023
    CMSA Room G10
    CMSA, 20 Garden Street, Cambridge, MA 02138 USA

    Probability Seminar

    Speaker: Youngtak Sohn (MIT)

    Title: Universality of max-margin classifiers

    Abstract: Many modern learning methods, such as deep neural networks, are so complex that they perfectly fit the training data. Despite this, they generalize well to the unseen data. Motivated by this phenomenon, we consider high-dimensional binary classification with linearly separable data. First, we consider Gaussian covariates and characterize linear classification problems for which the minimum norm interpolating prediction rule, namely the max-margin classification, has near-optimal prediction accuracy. Then, we discuss universality of max-margin classification. In particular, we characterize the prediction accuracy of the non-linear random features model, a two-layer neural network with random first layer weights. The spectrum of the kernel random matrices plays a crucial role in the analysis. Finally, we consider the wide-network limit, where the number of neurons tends to infinity, and show how non-linear max-margin classification with random features collapse to a linear classifier with a soft-margin objective.

    Joint work with Andrea Montanari, Feng Ruan, Jun Yan, and Basil Saeed.

  • 02
    11/02/2023

    Landscape of quantum phases in quantum materials

    4:30 pm-6:00 pm
    11/02/2023
    CMSA Room G10
    CMSA, 20 Garden Street, Cambridge, MA 02138 USA

    Joint Quantum Matter in Mathematics and Physics and Topological Quantum Matter Seminar

    Speaker: Liujun Zou (Perimeter Institute)

    Title: Landscape of quantum phases in quantum materials

    Abstract: A central goal of condensed matter physics is to understand which quantum phases of matter can emerge in a quantum material. For this purpose, one should be able to not only describe the quantum phases using some effective field theories, but also capture the important microscopic information of the material via mathematical formulation. In this talk, I will present a framework to classify quantum phases in quantum materials, where the microscopic information of a material is encoded in its quantum anomaly. I will talk about the application of this framework to classify various exotic quantum phases of matter in different lattice systems. Using our framework, we have obtained many results unexpected from the previous literature.

  • 03
    11/03/2023

    Symmetry and many-body topology in mixed states

    10:00 am-11:30 am
    11/03/2023
    CMSA Room G10
    CMSA, 20 Garden Street, Cambridge, MA 02138 USA

    Quantum Matter Seminar

    Speaker: Meng Cheng (Yale)

    Title: Symmetry and many-body topology in mixed states

    Abstract: It is by now well-understood that gapped ground states of local Hamiltonians can be classified topologically, and the nontrivial states exhibit many interesting topological phenomena. In this talk I’ll discuss recent developments in generalizing the topological classification to mixed states. Global symmetry plays a key role in understanding phases in pure states. For mixed states, certain “weak” symmetries may hold “on average” for the entire ensemble, in contrast to “strong” symmetries respected by each state in the ensemble. I will show that the interplay between these two kinds of symmetries lead to a rich landscape of symmetry-protected mixed states, and can also be used to characterize mixed state topological order.

     

  • 03
    11/03/2023

    Deformations of Landau-Ginzburg models and their fibers

    12:00 pm-1:00 pm
    11/03/2023
    CMSA Room G10
    CMSA, 20 Garden Street, Cambridge, MA 02138 USA

    Member Seminar

    Speaker: Zi Yang Kang

    Title: Deformations of Landau-Ginzburg models and their fibers

    Abstract: In mirror symmetry, the dual object to a Fano variety is a Landau-Ginzburg model. Broadly, a Landau-Ginzburg model is quasi-projective variety Y with a superpotential function w, but not all such pairs correspond to Fano varieties under mirror symmetry, so a very natural question to ask is: Which Landau-Ginzburg models are mirror to Fano varieties? In this talk, I will discuss a cohomological characterization of mirrors of (semi-)Fano varieties, focusing on the case of threefolds. I’ll discuss how this characterization relates to the deformation and Hodge theory of (Y,w), and in particular, how the classification of (semi-)Fano threefolds is related to questions about moduli spaces of lattice polarized K3 surfaces.

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