# Condensed Matter

This series consists of talks in the area of Condensed Matter.

## Seminar Series Events/Videos

Currently there are no upcoming talks in this series.

## Revivals imply quantum many-body scars

Friday Nov 22, 2019
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We derive general results relating revivals in the dynamics of quantum
many-body systems to the entanglement properties of energy eigenstates.
For a D-dimensional lattice system of N sites initialized in a
low-entangled and short-range correlated state, our results show that a
perfect revival of the state after a time at most poly(N) implies the
existence of "quantum many-body scars", whose number grows at least as
the square root of N up to poly-logarithmic factors. These are energy

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## Floquet quantum criticality

Thursday Nov 21, 2019
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It has recently been shown that quenched randomness, via the phenomenon of many-body localization, can stabilize dynamical phases of matter in periodically driven (Floquet) systems, with one example being discrete time crystals. This raises the question: what is the nature of the transitions between these Floquet many-body-localized phases, and how do they differ from equilibrium? We argue that such transitions are generically controlled by infinite randomness fixed points.

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## Non-invertible anomalies and Topological orders

Tuesday Nov 19, 2019
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## Dirty Quantum Criticality

Tuesday Nov 12, 2019
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## Numerical approach to infrared conformality and associated dualities in 2+1 dimensions

Tuesday Nov 05, 2019
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QFTs in 2+1 dimensions are powerful systems to understand the emergence of mass-gap and particle spectrum in QCD-like theories that describe our 3+1 dimensional world. Recently, these 2+1 dimensional systems have attracted even more attention due to conjectured dualities between seemingly very different theories and due to their applications to condensed matter systems. In this talk, I will describe our numerical investigations of the infrared behaviors of 2+1 dimensional U(1) and SU(N) gauge theories coupled to many favors of massless fermions using lattice regularization.

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## Hydrodynamics and (Pre)Thermalization in Floquet Systems

Friday Nov 01, 2019
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A tremendous amount of recent attention has focused on characterizing the dynamical properties of periodically driven many-body systems. Here, we use a novel numerical tool termed ‘density matrix truncation’ (DMT) to investigate the long-time dynamics of large-scale Floquet systems. By implementing a spatially inhomogeneous drive to a 1D quantum chain, we demonstrate that an interplay between Floquet heating and diffusive transport is crucial to understanding the system’s dynamics.

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## Symmetry indicators for topological materials

Tuesday Oct 22, 2019
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Many free-fermion topological phases can be diagnosed by analyzing a suitable collection of symmetry data. While the Fu-Kane parity criterion for topological insulators is an early example, the systematic generalization to cover all possible crystalline symmetries and their associated topological phases has only recently been achieved.

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## A Universal Operator Growth Hypothesis

Tuesday Oct 15, 2019
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Thanks to the Lanczos algorithm, the Hamiltonian dynamics of any operator can be written as a hopping problem on a semi-infinite one-dimensional chain. Our hypothesis states that the hopping strength grows linearly down the chain, with a universal growth rate $\alpha$ that is an intrinsic property of the system. This leads to an exponential motion of the operator down the chain, capturing the irreversible process of simple operators inevitably evolving into complex ones. This exponential growth exists for generic quantum systems, even away from large-$N$ or semiclassical limits.

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## Long-lived interacting phases of matter protected by multiple time-translation symmetries in quasiperiodically driven systems

Tuesday Oct 08, 2019
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The discrete time-translation symmetry of a periodically-driven (Floquet) system allows for the existence of novel, nonequilibrium interacting phases of matter. A well-known example is the discrete time crystal, a phase characterized by the spontaneous breaking of this time-translation symmetry.

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## Some aspects of the complex SYK model

Tuesday Oct 01, 2019
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Adding the global U(1) symmetry to the SYK model is a simple and fun exercise. I would like to explain how to obtain the charge and zero temperature entropy formulas solely from the IR parameters of the model. In particular, I will mention a free fermion interpretation of the zero temperature entropy. Work in progress with Kitaev, Sachdev, and Tarnopolsky.

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## LECTURES ON-DEMAND

### Gabriela González, Louisiana State University

Speaker: Gabriela Gonzalez