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X-WR-CALDESC:Events for CMSA
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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20210901T183100
DTEND;TZID=America/New_York:20210901T193100
DTSTAMP:20260715T074358
CREATED:20240214T093606Z
LAST-MODIFIED:20240301T100331Z
UID:10002639-1630521060-1630524660@cmsa.fas.harvard.edu
SUMMARY:Naturalness and muon anomalous magnetic moment
DESCRIPTION:Title: Naturalness and muon anomalous magnetic moment \nAbstract: We study a model for explaining the apparent deviation of the muon anomalous magnetic moment\, (g-2)\, from the Standard Model expectation. There are no new scalars and hence no new hierarchy puzzles beyond those associated with the Standard model Higgs; the only new particles that are relevant for (g-2) are vector-like singlet and doublet leptons. Interestingly\, this simple model provides a calculable example violating the Wilsonian notion of naturalness: despite the absence of any symmetries prohibiting its generation\, the coefficient of the naively leading dimension-six operator for (g−2) vanishes at one-loop. While effective field theorists interpret this either as a surprising UV cancellation of power divergences\, or as a delicate cancellation between matching UV and calculable IR corrections to (g−2) from parametrically separated scales\, there is a simple explanation in the full theory: the loop integrand is a total derivative of a function vanishing in both the deep UV and IR. The leading contribution to (g−2) arises from dimension-eight operators\, and thus the required masses of new fermions are lower than naively expected\, with a sizable portion of parameter space already covered by direct searches at the LHC. All of the the viable parameter can be probed by the LHC and planned future colliders.
URL:https://cmsa.fas.harvard.edu/event/9-1-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20210902T183400
DTEND;TZID=America/New_York:20210902T193400
DTSTAMP:20260715T074358
CREATED:20240214T093431Z
LAST-MODIFIED:20240301T095944Z
UID:10002634-1630607640-1630611240@cmsa.fas.harvard.edu
SUMMARY:Exotic quantum matter: From lattice gauge theory to hyperbolic lattices
DESCRIPTION:Title: Exotic quantum matter: From lattice gauge theory to hyperbolic lattices \nAbstract: This talk\, in two parts\, will discuss two (unrelated) instances of exotic quantum matter. In the first part\, I will discuss quantum critical points describing possible transitions out of the Dirac spin liquid\, towards either symmetry-breaking phases or topologically ordered spin liquids. I will also comment on the role of instanton zero modes for symmetry breaking in parton gauge theories. In the second part\, I will propose an extension of Bloch band theory to hyperbolic lattices\, such as those recently realized in circuit QED experiments\, based on ideas from algebraic geometry and Riemann surface theory.
URL:https://cmsa.fas.harvard.edu/event/9-2-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20210908T183700
DTEND;TZID=America/New_York:20210908T193700
DTSTAMP:20260715T074358
CREATED:20240214T093235Z
LAST-MODIFIED:20240301T095658Z
UID:10002632-1631126220-1631129820@cmsa.fas.harvard.edu
SUMMARY:Cornering the universal shape of fluctuations and entanglement
DESCRIPTION:Title: Cornering the universal shape of fluctuations and entanglement \nAbstract: Understanding the fluctuations of observables is one of the main goals in physics. We investigate such fluctuations when a subregion of the full system can be observed\, focusing on geometries with corners. We report that the dependence on the opening angle is super-universal: up to a numerical prefactor\, this function does not depend on anything\, provided the system under study is uniform\, isotropic\, and correlations do not decay too slowly. The prefactor contains important physical information: we show in particular that it gives access to the long-wavelength limit of the structure factor. We illustrate our findings with several examples: classical fluids\, fractional quantum Hall (FQH) states\, scale invariant quantum critical theories\, and metals. Finally\, we discuss connections with the entanglement entropy\, including new results for Laughlin FQH states. \nRef: arXiv:2102.06223
URL:https://cmsa.fas.harvard.edu/event/9-8-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20210909T183800
DTEND;TZID=America/New_York:20210909T193800
DTSTAMP:20260715T074358
CREATED:20240214T092815Z
LAST-MODIFIED:20240301T095523Z
UID:10002628-1631212680-1631216280@cmsa.fas.harvard.edu
SUMMARY:Quantum gravity from quantum matter
DESCRIPTION:Title: Quantum gravity from quantum matter \nAbstract: We present a model of quantum gravity in which dimension\, topology and geometry of spacetime are collective dynamical variables that describe the pattern of entanglement of underlying quantum matter. As spacetimes with arbitrary dimensions can emerge\, the gauge symmetry is generalized to a group that includes diffeomorphisms in general dimensions. The gauge symmetry obeys a first-class constraint operator algebra\, and is reduced to a generalized hypersurface deformation algebra in states that exhibit classical spacetimes. In the semi-classical limit\, we find a saddle-point solution that describes a series of (3+1)-dimensional de Sitter-like spacetimes with the Lorentzian signature bridged by Euclidean spaces in between.
URL:https://cmsa.fas.harvard.edu/event/9-9-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20210910T184400
DTEND;TZID=America/New_York:20210910T194400
DTSTAMP:20260715T074358
CREATED:20240214T092532Z
LAST-MODIFIED:20240301T095315Z
UID:10002624-1631299440-1631303040@cmsa.fas.harvard.edu
SUMMARY:More Exact Results in Gauge Theories: Confinement and Chiral Symmetry Breaking
DESCRIPTION:Title: More Exact Results in Gauge Theories: Confinement and Chiral Symmetry Breaking \nAbstract: In this follow-up to Hitoshi Murayama’s talk “Some Exact Results in QCD-like and Chiral Gauge Theories”\, I present a detailed analysis of the phases of $SO(N_c)$ gauge theory.\nStarting with supersymmetric $SO(N_c)$ with $N_F$ flavors\, we extrapolate to the non-supersymmetric limit using anomaly-mediated supersymmetry breaking (AMSB). Interestingly\, the abelian Coulomb and free magnetic phases do not survive supersymmetry breaking and collapse to a confining phase. This provided one of the first demonstrations of true confinement with chiral symmetry breaking in a non-SUSY theory.
URL:https://cmsa.fas.harvard.edu/event/9-10-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20210915T184600
DTEND;TZID=America/New_York:20210915T194600
DTSTAMP:20260715T074358
CREATED:20240214T092313Z
LAST-MODIFIED:20240301T094948Z
UID:10002623-1631731560-1631735160@cmsa.fas.harvard.edu
SUMMARY:Three-particle mechanism for pairing and superconductivity
DESCRIPTION:Title: Three-particle mechanism for pairing and superconductivity \nAbstract: I will present a new mechanism and an exact theory of electron pairing due to repulsive interaction in doped insulators. When the kinetic energy is small\, the dynamics of adjacent electrons on the lattice is strongly correlated. By developing a controlled kinetic energy expansion\, I will show that two doped charges can attract and form a bound state\, despite and because of the underlying repulsion. This attraction by repulsion is enabled by the virtual excitation of a third electron in the filled band. This three-particle pairing mechanism leads to a variety of novel phenomena at finite doping\, including spin-triplet superconductivity\, pair density wave\, BCS-BEC crossover and Feshbach resonance involving “trimers”. Possible realizations in moire materials\, ZrNCl and WTe2 will be discussed. \n[1] V. Crepel and L. Fu\, Science Advances 7\, eabh2233 (2021)\n[2] V. Crepel and L. Fu\, arXiv:2103.12060\n[3] K. Slagle and L. Fu\,  Phys. Rev. B 102\, 235423 (2020)
URL:https://cmsa.fas.harvard.edu/event/9-15-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20210916T184700
DTEND;TZID=America/New_York:20210916T194700
DTSTAMP:20260715T074358
CREATED:20240214T092053Z
LAST-MODIFIED:20240301T094752Z
UID:10002619-1631818020-1631821620@cmsa.fas.harvard.edu
SUMMARY:The Hilbert Space of large N Chern-Simons matter theories
DESCRIPTION:Title: The Hilbert Space of large N Chern-Simons matter theories \nAbstract: We demonstrate that all known formulae for the thermal partition function for large N Chern Simons matter theory admit a simple Hilbert Space interpretation. In each case this quantity equals the partition function of an associated ungauged large $N$ matter theory with a particular local Lagrangian with one additional element: the Fock Space of this associated theory is projected down to the subspace of its WZW singlets. This projection\, in particular\,  implies the previously encountered `Bosonic Exclusion Principle’\, namely that no single particle state can be occupied by more than $k_B$ particles ($k_B$ is the Chern Simons level). Unlike its Gauss Law counterpart\, the WZW constraint does not trivialize in the large volume limit. However thermodynamics does simplify in this limit;  the final partition function reduces to a product of partition functions associated with each single particle state. These individual single particle state partition functions are a one parameter generalizations of their free boson and free fermion counterparts\, and reduce to the later at extreme values of the ‘t Hooft coupling. At generic values of the rank and the level the occupation statistics of each energy level is given by a $q$ deformation of the usual free formulae of Bose and Fermi statistics.
URL:https://cmsa.fas.harvard.edu/event/9-16-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20210917T185400
DTEND;TZID=America/New_York:20210917T195400
DTSTAMP:20260715T074358
CREATED:20240214T091836Z
LAST-MODIFIED:20240301T094616Z
UID:10002617-1631904840-1631908440@cmsa.fas.harvard.edu
SUMMARY:Strong Coupling Theory of Magic-Angle Graphene: A Pedagogical Introduction
DESCRIPTION:Title: Strong Coupling Theory of Magic-Angle Graphene: A Pedagogical Introduction \nAbstract: In this talk\, I will review a recently developed strong coupling theory of magic-angle twisted bilayer graphene. An advantage of this approach is that a single formulation can capture both the insulating and superconducting states\, and with a few simplifying assumptions\, can be treated analytically. I begin by reviewing the electronic structure of magic angle graphene’s flat bands\, in a limit that exposes their peculiar band topology and geometry. I will show how similarities between the flat bands and the lowest Landau level can provide valuable insights into the effect of interactions and form the basis for an analytic treatment of the problem. At integer fillings\, this approach points to flavor ordered insulators\, which can be captured by a sigma-model in its ordered phase. Remarkably\, topological textures of the sigma model carry electric charge which enables the same theory to describe the doped phases away from integer filling. I will show how this approach can lead to superconductivity on disordering the sigma model\, and estimate the Tc for the superconductor. I will highlight the important role played by an effective super-exchange coupling both in pairing and in setting the effective mass of Cooper pairs. At the end\, I will show how this theory provides criteria to predict which multilayer graphene stacks are expected to superconduct including the recently discovered alternating twist trilayer platform.
URL:https://cmsa.fas.harvard.edu/event/9-17-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20210922T113300
DTEND;TZID=America/New_York:20210922T133300
DTSTAMP:20260715T074358
CREATED:20240214T091602Z
LAST-MODIFIED:20240301T094449Z
UID:10002615-1632310380-1632317580@cmsa.fas.harvard.edu
SUMMARY:Symmetry types in QFT and the CRT theorem
DESCRIPTION:Title: Symmetry types in QFT and the CRT theorem \nAbstract: I will discuss ideas around symmetry and Wick rotation contained in joint work with Mike Hopkins (https://arxiv.org/abs/1604.06527). This includes general symmetry types for relativistic field theories and their Wick rotation.  I will then indicate how the basic CRT theorem works for general symmetry types\, focusing on the case of the pin groups.  In particular\, I expand on a subtlety first flagged by Greaves-Thomas.
URL:https://cmsa.fas.harvard.edu/event/9-22-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20210923T114700
DTEND;TZID=America/New_York:20210923T134700
DTSTAMP:20260715T074358
CREATED:20240214T091227Z
LAST-MODIFIED:20240301T093540Z
UID:10002612-1632397620-1632404820@cmsa.fas.harvard.edu
SUMMARY:Applications of instantons\, sphalerons and instanton-dyons in QCD
DESCRIPTION:Title: Applications of instantons\, sphalerons and instanton-dyons in QCD \nAbstract: I start with a general map of gauge topology\, including monopoles\, instantons and instanton-dyons. Then comes reminder of the “topological landscape”\, the minimal energy gauge field configurations\, as a function of Chern-Simons number Ncs and r.m.s. size. It includes “valleys” at integer Ncs separated by mountain ridges. The meaning of instantons\, instanton-antiinstanton “streamlines” or thimbles\, and sphalerons are reminded\, together with some proposal to produce sphalerons at LHC and RHIC. \nApplications of instanton ensembles\, as a model of QCD vacuum\, are mostly related to their fermionic zero modes  and t’Hooft effective Lagrangian\, which explains explicit and spontaneous breaking of chiral symmetries. Recent applications are related with hadronic wave functions\, at rest and in the light front (LFWFs). Two application would be spin-dependent forces and the so called “flavor asymmetry of antiquark sea” of the nucleons. At temperatures comparable to deconfinement transition\, instantons get split into constituents called instanton-dyons. Studies of their ensemble explains both deconfinement and chiral transitions\, in ordinary and deformed QCD.
URL:https://cmsa.fas.harvard.edu/event/9-23-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20210929T114800
DTEND;TZID=America/New_York:20210929T134800
DTSTAMP:20260715T074358
CREATED:20240214T090955Z
LAST-MODIFIED:20240301T093415Z
UID:10002610-1632916080-1632923280@cmsa.fas.harvard.edu
SUMMARY:Oscillations in the thermal conductivity of a spin liquid*
DESCRIPTION:Title: Oscillations in the thermal conductivity of a spin liquid* \nAbstract: The layered honeycomb magnet alpha-RuCl3 orders below 7 K in a zigzag phase in zero field. An in-plane magnetic field H||a suppresses the zigzag order at 7 Tesla\, leaving a spin-disordered phase widely believed to be a quantum spin liquid (QSL) that extends to ~12 T. We have observed oscillations in the longitudinal thermal conductivity Kxx vs. H from 0.4 to 4 K. The oscillations are periodic in 1/H (with a break-in-slope at 7 T). The amplitude function is maximal in the QSL phase (7 –11.5 T). I will describe a benchmark for crystalline disorder\, the reproducibility and intrinsic nature of the oscillations\, and discuss implications for the QSL state. I will also show detailed data on the thermal Hall conductivity Kxy measured from 0.4 K to 10 K and comment on recent half-quantization results. \n*Czajka et al.\, Nature Physics 17\, 915 (2021). \nCollaborators: Czajka\, Gao\, Hirschberger\, Lampen Kelley\, Banerjee\, Yan\, Mandrus and Nagler.
URL:https://cmsa.fas.harvard.edu/event/9-29-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
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