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DTSTART;TZID=America/New_York:20230303T100000
DTEND;TZID=America/New_York:20230303T113000
DTSTAMP:20260528T185848
CREATED:20230802T164922Z
LAST-MODIFIED:20240819T145549Z
UID:10001169-1677837600-1677843000@cmsa.fas.harvard.edu
SUMMARY:Strongly coupled ultraviolet fixed point and symmetric mass generation in four dimensions with 8 Kähler-Dirac fermions
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Anna Hasenfratz (University of Colorado) \nTitle: Strongly coupled ultraviolet fixed point and symmetric mass generation in four dimensions with 8 Kähler-Dirac fermions\n\nAbstract: 4-dimensional gauge-fermion systems exhibit a quantum phase transition from a confining\, chirally broken phase to a conformal phase as the number of fermions is increased. While the existence of the conformal phase is well established\, very little is known about the nature of the phase transition or the strong coupling phase.\n\nLattice QCD methods can predict the RG $\beta$ function\, but the calculations are often limited by non-physical bulk phase transition that prevent exploring the strong coupling region of the phase diagram. Even the critical flavor number is controversial\, estimates vary between $N_f=8$ and 14 for fundamental fermions.\n\nUsing an improved lattice actions that include heavy Pauli-Villars (PV) type bosons to reduce ultraviolet fluctuations\, I was able to simulate an SU(3) system with 8 fundamental flavors at much stronger renormalized coupling than previously possibly. The numerical results indicate a smooth phase transition from weak coupling to a strongly coupled phase.\nI investigate the critical behavior of the transition using finite size scaling. The result of the scaling analysis is not consistent with a first order phase transition\, but it is well described by   Berezinsky-Kosterlitz-Thouless or BKT scaling. BKT scaling could imply that the 8-flavor system is the opening of the conformal window\, an exciting possibility that warrants further investigations.\n\nThe strongly coupled phase appear to be chirally symmetric but gapped\, suggesting symmetric mass generation (SMG). This could be the consequence of the lattice fermions used in this study. Staggered fermions in the massless limit are known to be anomaly free\, allowing an SMG phase in the continuum limit.\n  \n\n\nReferences:\nPhys.Rev.D 106 (2022) 1\, 014513 • e-Print: 2204.04801\nPhys.Rev.D 104 (2021) 7\, 074509 • e-Print: 2109.02790\nFor anomalies and staggered fermion\, see\nPhys.Rev.D 104 (2021) 9\, 094504 • e-Print: 2101.01026\n\nhttps://www.youtube.com/watch?v=3jtNsFGszjE&list=PL0NRmB0fnLJQAnYwkpt9PN2PBKx4rvdup&index=14
URL:https://cmsa.fas.harvard.edu/event/qm_3323/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-03.03.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230310T100000
DTEND;TZID=America/New_York:20230310T110000
DTSTAMP:20260528T185848
CREATED:20230802T165201Z
LAST-MODIFIED:20240110T054801Z
UID:10001170-1678442400-1678446000@cmsa.fas.harvard.edu
SUMMARY:Quantum entropy thermalization
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Yichen Huang (Harvard) \nTitle: Quantum entropy thermalization \nAbstract: In an isolated quantum many-body system undergoing unitary evolution\, the entropy of a subsystem (smaller than half the system size) thermalizes if at long times\, it is to leading order equal to the thermodynamic entropy of the subsystem at the same energy. We prove entropy thermalization for a nearly integrable Sachdev-Ye-Kitaev model initialized in a pure product state. The model is obtained by adding random all-to-all 4-body interactions as a perturbation to a random free-fermion model. In this model\, there is a regime of “thermalization without eigenstate thermalization.” Thus\, the eigenstate thermalization hypothesis is not a necessary condition for thermalization. \nReferences: arXiv:2302.10165\, 2209.09826; Joint work with Aram W. Harrow \n 
URL:https://cmsa.fas.harvard.edu/event/qm_31023/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-03.10.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230317T100000
DTEND;TZID=America/New_York:20230317T113000
DTSTAMP:20260528T185848
CREATED:20230802T165348Z
LAST-MODIFIED:20240228T091308Z
UID:10001171-1679047200-1679052600@cmsa.fas.harvard.edu
SUMMARY:Tensorial TQFT and disentangling modular Walker-Wang models
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Andreas Bauer  (Freie Universität Berlin) \nTitle: Tensorial TQFT and disentangling modular Walker-Wang models \nAbstract: I will introduce simple “tensorial” definitions for many algebraic and categorical structures appearing in the classification of topological phases of matter. Such “tensorial TQFTs” will be defined as maps that associate tensors to geometric/topological objects of some type\, subject to gluing axioms. Tensorial TQFTs are very directly related to microscopic physical models in terms of discrete path integrals. I will use those tensorial definitions to construct invertible boundaries which disentangle modular Walker-Wang models. \n 
URL:https://cmsa.fas.harvard.edu/event/qm_31723/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230324T100000
DTEND;TZID=America/New_York:20230324T113000
DTSTAMP:20260528T185848
CREATED:20230802T165633Z
LAST-MODIFIED:20240110T055248Z
UID:10001172-1679652000-1679657400@cmsa.fas.harvard.edu
SUMMARY:Traversable wormhole dynamics on a quantum processor
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Alexander Zlokapa\, MIT \nTitle: Traversable wormhole dynamics on a quantum processor \nAbstract: The holographic principle\, theorized to be a property of quantum gravity\, postulates that the description of a volume of space can be encoded on a lower-dimensional boundary. The anti-de Sitter (AdS)/conformal field theory correspondence or duality is the principal example of holography. The Sachdev–Ye–Kitaev (SYK) model of N >> 1 Majorana fermions has features suggesting the existence of a gravitational dual in AdS2\, and is a new realization of holography. We invoke the holographic correspondence of the SYK many-body system and gravity to probe the conjectured ER=EPR relation between entanglement and spacetime geometry through the traversable wormhole mechanism as implemented in the SYK model. A qubit can be used to probe the SYK traversable wormhole dynamics through the corresponding teleportation protocol. This can be realized as a quantum circuit\, equivalent to the gravitational picture in the semiclassical limit of an infinite number of qubits. Here we use learning techniques to construct a sparsified SYK model that we experimentally realize with 164 two-qubit gates on a nine-qubit circuit and observe the corresponding traversable wormhole dynamics. Despite its approximate nature\, the sparsified SYK model preserves key properties of the traversable wormhole physics: perfect size winding\, coupling on either side of the wormhole that is consistent with a negative energy shockwave\, a Shapiro time delay\, causal time-order of signals emerging from the wormhole\, and scrambling and thermalization dynamics. Our experiment was run on the Google Sycamore processor. By interrogating a two-dimensional gravity dual system\, our work represents a step towards a program for studying quantum gravity in the laboratory. Future developments will require improved hardware scalability and performance as well as theoretical developments including higher-dimensional quantum gravity duals and other SYK-like models. \n 
URL:https://cmsa.fas.harvard.edu/event/qm_32423/
LOCATION:Hybrid – G10
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-03.24.23.png
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