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X-WR-CALDESC:Events for CMSA
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DTSTART:20210314T070000
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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220302T103000
DTEND;TZID=America/New_York:20220302T120000
DTSTAMP:20260626T173728
CREATED:20240214T105827Z
LAST-MODIFIED:20240301T070805Z
UID:10002688-1646217000-1646222400@cmsa.fas.harvard.edu
SUMMARY:Exactly Solvable Lattice Hamiltonians and Gravitational Anomalies
DESCRIPTION:Abstract: We construct infinitely many new exactly solvable local commuting projector lattice Hamiltonian models for general bosonic beyond group cohomology invertible topological phases of order two and four in any spacetime dimensions\, whose boundaries are characterized by gravitational anomalies. Examples include the beyond group cohomology invertible phase “w2w3” in (4+1)D that has an anomalous boundary topological order with fermionic particle and fermionic loop excitations that have mutual statistics. Finally\, we will demonstrate a few examples of fermionic loop excitations.
URL:https://cmsa.fas.harvard.edu/event/3-2-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:MA
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-03.02.2022-1544x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220303T093000
DTEND;TZID=America/New_York:20220303T110000
DTSTAMP:20260626T173728
CREATED:20240214T105412Z
LAST-MODIFIED:20240813T163614Z
UID:10002684-1646299800-1646305200@cmsa.fas.harvard.edu
SUMMARY:Callan Rubakov Effect and Higher Charge Monopoles
DESCRIPTION:Abstract: In this talk we will discuss the interaction between magnetic monopoles and massless fermions. In the 1980’s Callan and Rubakov showed that in the simplest example and that fermion-monopole interactions catalyze proton decay in GUT completions of the standard model. Here we will explain how fermions in general representations interact with general spherically symmetric monopoles and classify the types of symmetries that are broken: global symmetries with ABJ-type anomalies.
URL:https://cmsa.fas.harvard.edu/event/3-3-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-03.03.2022-1544x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220309T103000
DTEND;TZID=America/New_York:20220309T120000
DTSTAMP:20260626T173728
CREATED:20240214T105142Z
LAST-MODIFIED:20240301T070302Z
UID:10002682-1646821800-1646827200@cmsa.fas.harvard.edu
SUMMARY:Anomalies\, topological insulators and Kaehler-Dirac fermions
DESCRIPTION:Abstract: Motivated by a puzzle arising from recent work on staggered lattice fermions we introduce Kaehler-Dirac fermions and describe their connection both to Dirac fermions and staggered fermions. We show that they suffer from a gravitational anomaly that breaks a chiral U(1) symmetry specific to Kaehler-Dirac fermions down to Z_4 in any even dimension. In odd dimensions we show that the effective theory that results from integrating out massive Kaehler-Dirac fermions is a topological gravity theory. Such theories generalize Witten’s construction of (2+1) gravity as a Chern Simons theory. In the presence of a domain wall massless modes appear on the wall which can be consistently coupled to gravity due to anomaly inflow from the bulk gravitational theory. Much of this story parallels the usual discussion of topological insulators. The key difference is that the twisted chiral symmetry and anomaly structure of Kaehler-Dirac theories survives intact under discretization and governs the behavior of the lattice models. $Z_4$ invariant four fermion interactions can be used to gap out states in such theories without breaking symmetries and in flat space yields the known constraints on the number of Majorana fermions needed symmetric mass generation namely eight and sixteen Majorana spinors in two and four dimensions.
URL:https://cmsa.fas.harvard.edu/event/3-9-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-03.09.2022-1544x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220310T200000
DTEND;TZID=America/New_York:20220310T213000
DTSTAMP:20260626T173728
CREATED:20240214T104900Z
LAST-MODIFIED:20240813T163724Z
UID:10002680-1646942400-1646947800@cmsa.fas.harvard.edu
SUMMARY:Resonant side-jump thermal Hall effect of phonons coupled to dynamical defects
DESCRIPTION:Abstract: We present computations of the thermal Hall coefficient of phonons scattering off defects with multiple energy levels. Using a microscopic formulation based on the Kubo formula\, we find that the leading contribution perturbative in the phonon-defect coupling is of the ‘side-jump’ type\, which is proportional to the phonon lifetime. This contribution is at resonance when the phonon energy equals a defect level spacing. Our results are obtained for different defect models\, and include models of an impurity quantum spin in the presence of quasi-static magnetic order with an isotropic Zeeman coupling to the applied field. \nThis work is based on arxiv: 2201.11681
URL:https://cmsa.fas.harvard.edu/event/3-10-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-03.10.2022-1544x2048-1-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220316T103000
DTEND;TZID=America/New_York:20220316T120000
DTSTAMP:20260626T173728
CREATED:20240214T104642Z
LAST-MODIFIED:20240301T065907Z
UID:10002679-1647426600-1647432000@cmsa.fas.harvard.edu
SUMMARY:Summing Over Bordisms In 2d TQFT
DESCRIPTION:Abstract: Some recent work in the quantum gravity literature has considered what happens when the amplitudes of a TQFT are summed over the bordisms between fixed in-going and out-going boundaries. We will comment on these constructions. The total amplitude\, that takes into account all in-going and out-going boundaries can be presented in a curious factorized form. This talk reports on work done with Anindya Banerjee and is based on the paper on the e-print arXiv  2201.00903.
URL:https://cmsa.fas.harvard.edu/event/3-16-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-03.16.2022-1544x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220317T093000
DTEND;TZID=America/New_York:20220317T110000
DTSTAMP:20260626T173728
CREATED:20240214T104122Z
LAST-MODIFIED:20240813T163816Z
UID:10002678-1647509400-1647514800@cmsa.fas.harvard.edu
SUMMARY: A Hike through the Swampland
DESCRIPTION:Abstract: The Swampland program aims at uncovering the universal implications of quantum gravity at low-energy physics. I will review the basic ideas of the Swampland program\, formal and phenomenological implications\, and provide a survey of the techniques commonly used in Swampland research including tools from quantum information\, holography\, supersymmetry\, and string theory.
URL:https://cmsa.fas.harvard.edu/event/3-17-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:MA
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-03.17.2022-1-1544x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220323T103000
DTEND;TZID=America/New_York:20220323T120000
DTSTAMP:20260626T173728
CREATED:20240214T103754Z
LAST-MODIFIED:20240301T064719Z
UID:10002677-1648031400-1648036800@cmsa.fas.harvard.edu
SUMMARY:Non-zero momentum requires long-range entanglement
DESCRIPTION:Youtube Video \n  \nAbstract: I will show that a quantum state in a lattice spin (boson) system must be long-range entangled if it has non-zero lattice momentum\, i.e. if it is an eigenstate of the translation symmetry with eigenvalue not equal to 1. Equivalently\, any state that can be connected with a non-zero momentum state through a finite-depth local unitary transformation must also be long-range entangled. The statement can also be generalized to fermion systems. I will then present two applications of this result: (1) several different types of Lieb-Schultz-Mattis (LSM) theorems\, including a previously unknown version involving only a discrete Z_n symmetry\, can be derived in a simple manner; (2) a gapped topological order (in space dimension d>1) must weakly break translation symmetry if one of its ground states on torus has nontrivial momentum – this generalizes the familiar physics of Tao-Thouless in fractional quantum Hall systems.
URL:https://cmsa.fas.harvard.edu/event/3-23-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:MA
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-03.23.2022-1583x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220324T093000
DTEND;TZID=America/New_York:20220324T110000
DTSTAMP:20260626T173728
CREATED:20240214T103248Z
LAST-MODIFIED:20240813T162724Z
UID:10002675-1648114200-1648119600@cmsa.fas.harvard.edu
SUMMARY:Edge physics at the deconfined transition between a quantum spin Hall insulator and a superconductor
DESCRIPTION:Youtube Video \n  \nAbstract: I will talk about the edge physics of the deconfined quantum phase transition (DQCP) between a spontaneous quantum spin Hall (QSH) insulator and a spin-singlet superconductor (SC). Although the bulk of this transition is in the same universality class as the paradigmatic deconfined Neel to valence-bond-solid transition\, the boundary physics has a richer structure due to proximity to a quantum spin Hall state. We use the parton trick to write down an effective field theory for the QSH-SC transition in the presence of a boundary and calculate various edge properties in a large-N limit. We show that the boundary Luttinger liquid in the QSH state survives at the phase transition\, but only as fractional degrees of freedom that carry charge but not spin. The physical fermion remains gapless on the edge at the critical point\, with a universal jump in the fermion scaling dimension as the system approaches the transition from the QSH side. The critical point could be viewed as a gapless analogue of the QSH state but with the full SU(2) spin rotation symmetry\, which cannot be realized if the bulk is gapped. This talk reports on the work done with Liujun Zou and Chong Wang (arxiv:2110.08280).
URL:https://cmsa.fas.harvard.edu/event/3-24-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:MA
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-03.24.2022-1583x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220330T103000
DTEND;TZID=America/New_York:20220330T120000
DTSTAMP:20260626T173728
CREATED:20240214T103058Z
LAST-MODIFIED:20240301T064220Z
UID:10002673-1648636200-1648641600@cmsa.fas.harvard.edu
SUMMARY:Renormalization group flow as optimal transport
DESCRIPTION:Youtube Video \n  \nAbstract: We show that Polchinski’s equation for exact renormalization group flow is equivalent to the optimal transport gradient flow of a field-theoretic relative entropy.  This gives a surprising information-theoretic formulation of the exact renormalization group\, expressed in the language of optimal transport.  We will provide reviews of both the exact renormalization group\, as well as the theory of optimal transportation.  Our results allow us to establish a new\, non-perturbative RG monotone\, and also reformulate RG flow as a variational problem.  The latter enables new numerical techniques and allows us to establish a systematic connection between neural network methods and RG flows of conventional field theories.  Our techniques generalize to other RG flow equations beyond Polchinski’s.
URL:https://cmsa.fas.harvard.edu/event/3-30-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:MA
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-03.30.2022-1583x2048-1.jpg
END:VEVENT
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