
Speaker: Han YanTitle: Fracton orders in hyperbolic space and its excitations with fractal mobilityVenue: virtualQuantum Matter Seminar Speaker: Han Yan (Rice U) Title: Fracton orders in hyperbolic space and its excitations with fractal mobility Abstract: Unlike ordinary topological quantum phases, fracton orders are intimately dependent on the underlying lattice geometry. In this work, we study a generalization of the Xcube model, on lattices embedded in a stack of hyperbolic planes. We demonstrate that for certain hyperbolic lattice tesselations, this model hosts a new kind of subdimensional particle, treeons, which can only move on a fractalshaped subset of the lattice. Such an excitation only appears on hyperbolic geometries; on flat spaces, treeons become either a lineon or a planeon. Additionally, we find intriguingly that for certain hyperbolic tessellations, a fracton can be created… 

Speaker: Igor R. KlebanovTitle: Group Invariant States as ManyBody ScarsVenue: virtualQuantum Matter Seminar Title: Group Invariant States as ManyBody Scars Speaker: Igor R. Klebanov (Princeton University) Abstract: Quantum manybody scars have been an active area of research in Condensed Matter Physics for several years. In some manybody systems, the Hilbert space breaks up into a large ergodic sector and a much smaller scar subspace. It has been suggested [K. Pakrouski et al., Phys. Rev. Lett. 125 (2020) 230602] that the two sectors may be distinguished by their transformation properties under a large group whose rank grows with the system size (this group is not a symmetry of the Hamiltonian). The scars are invariant under this group, while all other states are not. We begin by reviewing some manybody… 

Speaker: Jacob McNamara (Caltech) and Matthew Reece (Harvard)Title: Reflections on Parity BreakingVenue: virtualQuantum Matter Seminar Speakers: Jacob McNamara (Caltech) and Matthew Reece (Harvard) Title: Reflections on Parity Breaking Abstract: One approach to the Strong CP Problem (known as NelsonBarr models) is to assume that parity is a gauge symmetry, which is spontaneously broken in the world around us. In this talk, we will describe the formal meaning of parity as a gauge symmetry, and argue that the domain walls formed from spontaneous parity breaking are exactly stable. This stability can be understood as the result of an unusual sort of conserved charge, which has features in common with both gauge charges and global charges. We will explain how these charges are compatible with the expected absence of global symmetries in… 

Speaker: Yang QiTitle: Phase Fluctuations in TwoDimensional Superconductors and Pseudogap PhenomenonVenue: virtualQuantum Matter Seminar Speaker: Yang Qi (Fudan) Title: Phase Fluctuations in TwoDimensional Superconductors and Pseudogap Phenomenon Abstract: We study the phase fluctuations in the normal state of a general twodimensional (2d) superconducting system with swave pairing. The effect of phase fluctuations of the pairing fields can be dealt with perturbatively using disorder averaging, after we treat the local superconducting order parameter as a static disordered background. It is then confirmed that the phase fluctuations above the 2d BerenzinskiiKosterlitzThouless (BKT) transition give birth to the pseudogap phenomenon, leading to a significant broadening of the singleparticle spectral functions. Quantitatively, the broadening of the spectral weights at the BCS gap is characterized by the ratio of the superconducting coherence length and… 

Speaker: Federico BonettiTitle: NonInvertible Symmetries from Holography and BranesVenue: virtualQuantum Matter Seminar Speaker: Federico Bonetti (Oxford) Title: NonInvertible Symmetries from Holography and Branes Abstract: The notion of global symmetry in quantum field theory (QFT) has witnessed dramatic generalizations in the past few years. One of the most exciting developments has been the identification of 4d QFTs possessing noninvertible symmetries, i.e. global symmetries whose generators exhibit fusion rules that are not grouplike. In this talk, I will discuss realizations of noninvertible symmetries in string theory and holography. As a concrete case study, I will consider the KlebanovStrassler setup for holographic confinement in Type IIB string theory. The global symmetries of the holographic 4d QFT (both invertible and noninvertible) can be accessed by studying the topological couplings of the… 

Speaker: Sungwoo HongTitle: Neutrino Masses from Generalized Symmetry BreakingVenue: virtualQuantum Matter Seminar Speaker: Sungwoo Hong (U Chicago & KAIST) Title: Neutrino Masses from Generalized Symmetry Breaking Abstract: We explore generalized global symmetries in theories of physics beyond the Standard Model. Theories of Z′ bosons generically contain ‘noninvertible’ chiral symmetries, whose presence indicates a natural paradigm to break this symmetry by an exponentially small amount in an ultraviolet completion. For example, in models of gauged lepton family difference such as the phenomenologically wellmotivated U(1)Lμ−Lτ, there is a noninvertible lepton number symmetry which protects neutrino masses. We embed these theories in gauged nonAbelian horizontal lepton symmetries, e.g. U(1)Lμ−Lτ⊂SU(3)H, where the generalized symmetries are broken nonperturbatively by the existence of lepton family magnetic monopoles. In such theories, either Majorana or… 

Speaker: Junkai DongTitle: Exact ManyBody Ground States from Decomposition of Ideal Higher Chern Bands: Applications to Chirally Twisted Graphene MultilayersVenue: virtualQuantum Matter Seminar Speaker: Junkai Dong (Harvard University) Title: Exact ManyBody Ground States from Decomposition of Ideal Higher Chern Bands: Applications to Chirally Twisted Graphene Multilayers Abstract: Motivated by the higher Chern bands of twisted graphene multilayers, we consider flat bands with arbitrary Chern number C with ideal quantum geometry. While C>1 bands differ from Landau levels, we show that these bands host exact fractional Chern insulator (FCI) ground states for short range interactions. We show how to decompose ideal higher Chern bands into separate ideal bands with Chern number 1 that are intertwined through translation and rotation symmetry. The decomposed bands admit an SU(C) action that combines real space and momentum space translations. Remarkably, they also allow… 

Speaker: Gabriel WongTitle: D gravity and gravitational entanglement entropyVenue: virtualQuantum Matter Seminar Speaker: Gabriel Wong (Harvard CMSA) Title: 3D gravity and gravitational entanglement entropy Abstract: Recent progress in AdS/CFT has provided a good understanding of how the bulk spacetime is encoded in the entanglement structure of the boundary CFT. However, little is known about how spacetime emerges directly from the bulk quantum theory. We address this question in an effective 3d quantum theory of pure gravity, which describes the high temperature regime of a holographic CFT. This theory can be viewed as a $q$deformation and dimensional uplift of JT gravity. Using this model, we show that the BekensteinHawking entropy of a twosided black hole equals the bulk entanglement entropy of gravitational edge modes. These edge modes transform… 

Speaker: Pok Man TamTitle: Topology of the Fermi sea: Ordinary metals as topological materialsVenue: VirtualQuantum Matter Seminar Speaker: Pok Man Tam (University of Pennsylvania) Title: Topology of the Fermi sea: Ordinary metals as topological materials Abstract: It has long been known that the quantum ground state of a metal is characterized by an abstract manifold in momentum space called the Fermi sea. Fermi sea can be distinguished topologically in much the same way that a ball can be distinguished from a donut by counting the number of holes. The associated topological invariant, i.e. the Euler characteristic (χ_F), serves to classify metals. Here I will survey two recent proposals relating χ_F to experimental observables, namely: (i) equaltime density/number correlations [1], and (ii) Andreev state transport along a planar Josephson junction [2]. Moreover, from the perspective… 

Speaker: Daniel S. FreedTitle: Topological symmetry in field theoryVenue: virtualQuantum Matter Seminar Speaker: Daniel S. Freed (U Texas) Title: Topological symmetry in field theory Abstract: Recently there has been lots of activity surrounding generalized notions of symmetry in quantum field theory, including “categorical symmetries,” “higher symmetries,” “noninvertible symmetries,” etc. Inspired by definitions of abstract (finite) groups and algebras and their linear actions, we introduce a framework for these symmetries in field theory and a calculus of topological defects based on techniques in topological field theory. This is joint work with Constantin Teleman and Greg Moore. 

Speaker: Francisco MachadoTitle: KardarParisiZhang dynamics in integrable quantum magnetsVenue: virtualQuantum Matter Seminar Speaker: Francisco Machado (Berkeley/Harvard) Title: KardarParisiZhang dynamics in integrable quantum magnets Abstract: Although the equations of motion that govern quantum mechanics are wellknown, understanding the emergent macroscopic behavior that arises from a particular set of microscopic interactions remains remarkably challenging. One particularly important behavior is that of hydrodynamical transport; when a quantum system has a conserved quantity (i.e. total spin), the latetime, coarsegrained dynamics of the conserved charge is expected to follow a simple, classical hydrodynamical description. However the nature and properties of this hydrodynamical description can depend on many details of the underlying interactions. For example, the presence of additional dynamical constraints can fundamentally alter the propagation of the conserved quantity and induce slowerthandiffusion propagation. At the… 

Speaker: João CaetanoTitle: Unorientable Quantum Field Theories: From crosscaps to holographyVenue: virtualQuantum Matter Seminar Speaker: João Caetano (CERN) Title: Unorientable Quantum Field Theories: From crosscaps to holography Abstract: In two dimensions, one can study quantum field theories on unorientable manifolds by introducing crosscaps. This defines a class of states called crosscap states which share a few similarities with the notion of boundary states. In this talk, I will show that integrable theories remain integrable in the presence of crosscaps, and this allows to exactly determine the crosscap state. In four dimensions, the analog is to place the quantum field theory on the real projective space, the simplest unorientable 4manifold. I will show how to do this in the example of N=4 Supersymmetric YangMills, discuss its holographic description and present a… 

Speaker: Ethan LakeTitle: Insulating BECs and other surprises in dipoleconserving systemsVenue: virtualQuantum Matter Seminar Speaker: Ethan Lake (MIT) Title: Insulating BECs and other surprises in dipoleconserving systems Abstract: I will discuss recent work on bosonic models whose dynamics conserves both total charge and total dipole moment, a situation which can be engineered in strongly tilted optical lattices. Related models have received significant attention recently for their interesting outofequilibrium dynamics, but analytic and numeric studies reveal that they also possess rather unusual ground states. I will focus in particular on a dipoleconserving variant of the BoseHubbard model, which realizes an unusual phase of matter that possesses a BoseEinstein condensate, but which is nevertheless insulating, and has zero superfluid weight. Time permitting, I will also describe the physics of a regime in which these models… 

Speaker: Michele Del ZottoTitle: On the sixdimensional origin of noninvertible symmetriesVenue: virtualQuantum Matter Seminar Speaker: Michele Del Zotto (Uppsala University) Title: On the sixdimensional origin of noninvertible symmetries Abstract: I will present a review about recent progress in charting noninvertible symmetries for fourdimensional quantum field theories that have a sixdimensional origin. These include in particular N=4 supersymmetric YangMills theories, and also a large class of N=2 supersymmetric theories which are conformal and do not have a conventional Lagrangian description (the socalled theories of “class S”). Among the main results, I will explain criteria for identifying examples of systems with intrinsic and nonintrinsic noninvertible symmetries, as well as explore their higher dimensional origin. This seminar is based on joint works with Vladimir Bashmakov, Azeem Hasan, and Justin Kaidi. 

Speaker: Liang KongTitle: Topological Wick Rotation and Holographic dualityVenue: virtualQuantum Matter Seminar Speaker: Liang Kong (Sustech) Title: Topological Wick Rotation and Holographic duality Abstract: I will explain a new type of holographic dualities between n+1D topological orders with a chosen boundary condition and nD (potentially gapless) quantum liquids. It is based on the idea of topological Wick rotation, a notion which was first used in arXiv:1705.01087 and was named, emphasized and generalized later in arXiv:1905.04924. Examples of these holographic dualities include the duality between 2+1D toric code model and 1+1D Ising chain and its finitegroup generalizations (independently discovered by many others); those between 2+1D topological orders and 1+1D rational conformal field theories; and those between n+1D finite gauge theories with a gapped boundary and nD gapped quantum… 

Speaker: Justin KulpTitle: Holomorphic Twists and Confinement in N= SYMVenue: virtualQuantum Matter Seminar Speaker: Justin Kulp (Perimeter Institute) Title: Holomorphic Twists and Confinement in N=1 SYM Abstract: Supersymmetric QFT’s are of longstanding interest for their high degree of solvability, phenomenological implications, and rich connections to mathematics. In my talk, I will describe how the holomorphic twist isolates the protected quantities which give SUSY QFTs their potency by restricting to the cohomology of one supercharge. I will briefly introduce infinite dimensional symmetry algebras, generalizing Virasoro and KacMoody symmetries, which emerge. Finally, I will explain a potential novel UV manifestation of confinement, dubbed “holomorphic confinement,” in the example of pure SU(N) super YangMills. Based on arXiv:2207.14321 and 2 forthcoming works with Kasia Budzik, Davide Gaiotto, Brian Williams, Jingxiang Wu,… 

Speaker: Avner KarasikTitle: Candidates for NonSupersymmetric DualitiesVenue: virtualQuantum Matter in Mathematics and Physics Speaker: Avner Karasik (University of Cambridge, UK) Title: Candidates for NonSupersymmetric Dualities Abstract: In the talk I will discuss the possibility and the obstructions of finding nonsupersymmetric dualities for 4d gauge theories. I will review consistency conditions based on Weingarten inequalities, anomalies and large N, and clarify some subtle points and misconceptions about them. Later I will go over some old and new examples of candidates for nonsupersymmetric dualities. The will be based on 2208.07842 

Speaker: Yichul ChoTitle: Noninvertible Symmetries in NatureVenue: VirtualQuantum Matter in Mathematics and Physics Speaker: Yichul Cho (SUNY Stony Brook) Title: Noninvertible Symmetries in Nature Abstract: In this talk, I will discuss noninvertible symmetries in familiar 3+1d quantum field theories describing our Nature. In massless QED, the classical U(1) axial symmetry is not completely broken by the ABJ anomaly. Instead, it turns into a discrete, noninvertible symmetry. The noninvertible symmetry operator is obtained by dressing the naïve U(1) axial symmetry operator with a fractional quantum Hall state. We also find a similar noninvertible symmetry in the massless limit of QCD, which provides an alternative explanation for the neutral pion decay. In the latter part of the talk, I will discuss noninvertible timereversal symmetries in 3+1d… 

Speaker: Zhengyan Darius ShiTitle: Gifts from anomalies: new results on quantum critical transport in non Fermi liquidsVenue: CMSA Room G10Quantum Matter in Mathematics and Physics Seminar Speaker: Zhengyan Darius Shi (MIT) Title: Gifts from anomalies: new results on quantum critical transport in nonFermi liquids Abstract: NonFermi liquid phenomena arise naturally near Landau ordering transitions in metallic systems. Here, we leverage quantum anomalies as a powerful nonperturbative tool to calculate optical transport in these models in the infrared limit. While the simplest such models with a single boson flavor (N=1) have zero incoherent conductivity, a recently proposed large N deformation involving flavorrandom Yukawa couplings between N flavors of bosons and fermions admits a nontrivial incoherent conductivity (z is the boson dynamical exponent) when the order parameter is odd under inversion. The presence of incoherent conductivity in the random flavor… 

Speaker:Title: Transport in largeN critical Fermi surfaceVenue: virtualSpeaker: Haoyu Guo (Harvard) Title: Transport in largeN critical Fermi surface Abstract: A Fermi surface coupled to a scalar field can be described in a 1/N expansion by choosing the fermionscalar Yukawa coupling to be random in the Ndimensional flavor space, but invariant under translations. We compute the conductivity of such a theory in two spatial dimensions for a critical scalar. We find a Drude contribution, and show that a previously proposed \omega^{2/3} contribution to the optical conductivity at frequency \omega has vanishing coefficient. We also describe the influence of impurity scattering of the fermions, and find that while the self energy resembles a marginal Fermi liquid, the resistivity behaves like a Fermi liquid. Arxiv references: 2203.04990, 2207.08841 