Mike Blake (MIT)
10/4/17, 9:00 AM
In this talk I will discuss recent developments that have suggested new connections between the transport properties of quantum matter and many-body chaos. In particular I will describe how in many holographic theories there are simple relationships between the thermoelectric diffusion constants and the butterfly velocity, which describes the speed at which chaos propagates.
10/4/17, 9:45 AM
I will show that the thermal diffusivity is closely related to the butterfly velocity and the Lyapunov exponent in a large class of holographic theories at low temperature. I will explain how this is a consequence of the fact that the thermal conductivity in these theories depends only on the metric near the horizon of the dual black hole, and is otherwise independent of the...
10/4/17, 10:30 AM
Raghu Mahajan (IAS)
10/4/17, 11:00 AM
The linear growth of operators in local quantum systems leads to an effective lightcone even if the system is non-relativistic. We show that consistency of diffusive transport with this lightcone places an upper bound on the diffusivity: D<=v^2 \tau_eq. The operator growth velocity v defines the lightcone and \tau_eq is the local equilibration timescale, beyond which the dynamics of...
Vaios Ziogas (Durham University)
10/4/17, 11:30 AM
In this talk I will consider transport of conserved charges in strongly coupled quantum systems with broken translations, using holographic techniques. Such systems are relevant in condensed matter physics in the context of spontaneous symmetry breaking as well as in the context of momentum relaxation through a lattice. In this setup of reduced symmetry, I will give the precise...
Alexander Krikun (Leiden University)
10/4/17, 12:00 PM
As soon as one considers the holographic model with spontaneous translation symmetry breaking on top of the background, which posses explicit modulation of the chemical potential, one encounters a broad range of interesting physical phenomena related to the commensurate lock in between these two spacial structures. I will show that in this holographic framework one can relyiably address...
10/4/17, 12:30 PM
Gurau Razvan (Ecole Polytechnique and CNRS)
10/4/17, 2:00 PM
Random Tensors generalize random matrices to higher dimensions. In the large N limit random tensors exhibit a new universal behavior dominated by melonic graphs. In this talk I will review the basics of Random Tensor theory and discuss this new universal behavior.
Aurelio Romero-Bermudez (Leiden University)
10/4/17, 2:45 PM
I will show that a generalised SYK model with an additional one-body infinite-range random interaction, which is a relevant perturbation in the infrared, is still quantum chaotic for a fixed value of the perturbation and sufficiently high temperature. I will also show that, at low temperature, this model shows a chaotic-to-integrable transition. [arXiv:1707.02197]
10/4/17, 3:15 PM
Christiana Pantelidou (Durham University)
10/4/17, 3:45 PM
I will discuss the holographic dual of strongly coupled, four-dimensional SYM with massless flavour in the Veneziano limit at finite quark density and finite temperature. The fundamental degrees of freedom are modelled by a distribution of D7-branes with a non-vanishing electric field on their worldvolume that backreacts on the geometry of a stack of colour D3-branes. I will present the...
10/4/17, 6:30 PM
10/5/17, 9:00 AM
In this talk I will present some recent progress in studying thermalisation in low-dimensional systems with holographic duals. Firstly I will describe first-principles field theory calculations in pure states dual to collapsing black holes, highlighting the role of non-perturbative corrections in the information-loss problem. Secondly, I will show how eigenstate thermalisation supplies a...
10/5/17, 9:45 AM
In this talk I will examine transport in a holographic model in which the dynamics of the charged degrees of freedom is described by the non-perturbative Dirac--Born--Infeld (DBI) action. The generic structure of the DC conductivity matrix for these theories is extremely rich. When the momentum relaxation is strong, the model reproduces the anomalous temperature dependence of the...
10/5/17, 10:30 AM
10/5/17, 11:00 AM
Renormalization group flows between fixed points provide a powerful framework for both exploring and cataloging the myriad ways in which field theories can behave at low energies. Under favorable conditions, the physics of such flows can be reformulated geometrically, and examined in the context of gauge/gravity duality. I will discuss an interesting class of such flows, driven by...
10/5/17, 11:30 AM
Adherence to a strict top-down framework in holography imposes tight constraints when computing for example fermionic spectral weights. I will discuss some holographic computations in finite density ABJM theory where these constraints translate into interesting physical properties, such as Fermi surfaces, without well-defined quasiparticles, that become gapped when the U(1) charge...
10/5/17, 12:00 PM
Many materials that behave as so-called non-relativistic fluids with strong interactions exhibit interesting properties, such as non-conventional superconductivity and superfluidity. The fact that non-relativistic fluids do not necessarily allow for boost symmetries poses a problem for making predictions using hydrodynamics, in which normally Lorentz or Galilean boosts are assumed. Me...
10/5/17, 12:30 PM
10/5/17, 2:00 PM
The emergent integrability of the many-body localized phase can be understood in terms of localized quasiparticles. As a result, the occupations of the one-particle density matrix in eigenstates show a Fermi-liquid like discontinuity. Furthermore, in the steady state reached at long times after a global quench from a perfect density wave state, this occupation discontinuity is absent but...
10/5/17, 2:45 PM
We study the strongly coupled theory of a Fermi surface in 2+1 dimensions coupled to a massless scalar in a general limit in which fermionic loops are suppressed such as a matrix large $N$ limit or a vector small $N_f$ limit. The case where the Fermi velocity equals the boson velocity gives extra symmetry to the low energy limit of all diagrams which allows us to make general statements...
10/5/17, 3:15 PM
I will discuss the concept of generalised global symmetry, which describe the conservation law associated to dynamical extended objects, and their implementation in holography. I will also discuss its application in the effective theory of matter in the presence of strong dynamical magnetic field as well as the incommensurate phase which breaks the translational symmetry spontaneously
10/5/17, 3:20 PM
We derive relations between viscosities and momentum conductivity in 2 + 1 dimensions by finding a generalization of holographic Ward identities for the energy-momentum tensor. The generalization is novel in the sense that it goes beyond the usual identities obtained from holographic renormalization. Our results are consistent with previous field theory analysis. The main tools we use...
10/5/17, 3:25 PM
We realize the weak momentum relaxation in Rindler fluid, which lives on the time-like cutoff surface in an accelerating frame of flat spacetime. The translational invariance is broken by massless scalar fields with weak strength. Both of the Ward identity and the momentum relaxation rate of Rindler fluid are obtained, with higher order correction in terms of the strength of...
10/5/17, 3:30 PM
10/5/17, 4:00 PM
A number of very recent experiments on strange metals in the cuprates have again highlighted the anomalous behavior of these materials compared to ordinary Fermi-liquid metals. Almost too good to be true, the displayed behavior shows remarkable similarities with the qualitative predictions from holography. I will briefly review these experiments probing the single electron spectrum,...
10/5/17, 6:30 PM
10/6/17, 9:00 AM
The simple moral of eigenstate thermalization is that what we think is the rattling of classical things producing heat is a delusion caused by our incapacity to keep track of the flow of quantum information in the enormous many-body Hilbert space. Are there circumstances where it is impossible to construct such a consistent classical metaphor? Helped by holography we stumbled...
10/6/17, 9:45 AM
In a holographic probe-brane model exhibiting a spontaneously spatially modulated CDW+SDW ground state, I will introduce explicit sources of symmetry breaking in the form of ionic and antiferromagnetic lattices. I will demonstrate pinning, in which the translational Goldstone mode is lifted by the introduction of explicit sources of translational symmetry breaking. The numerically...
10/6/17, 10:30 AM
261. Hydrodynamics, magnetohydrodynamics from generalised global symmetries and the holographic butterfly effect
10/6/17, 11:00 AM
In my talk, I will discuss various topics that will revolve around the subject of hydrodynamics. The first part of the talk will begin with a general discussion of hydrodynamics, its breakdown at weak coupling and the connection between hydrodynamics and many-body chaos. In particular, I will argue that at strong coupling, the holographic butterfly effect can be understood in terms...
Andrew Lucas (Stanford University)
10/6/17, 11:45 AM
Quantum chaos describes the dynamics of a many-body system at the onset of thermalization, while hydrodynamics describes the late time dynamics after thermalization has occurred locally. Consistency between these two descriptions provides constraints linking hydrodynamic data such as diffusion constants and sound speeds to quantum chaos. I will show that in large N quantum field...
10/6/17, 12:30 PM
10/6/17, 2:00 PM
Holography provides models where internal and spacetime symmetries can be explicitly broken, yet the breaking is dominated by the spontaneous generation of a symmetry- breaking VEV. The characterization and actual computation of low-energy correlators reveals the dynamical detail of (pseudo)Nambu-Goldsotne modes and accounts for generic features of CMT systems such as the...
10/6/17, 2:30 PM
We discuss the presence and the physical features of (pseudo)-phonons in the context of ''solid'' holographic massive gravity theories. We present a bottom-up model exhibiting for the first time in holography (gapped and damped) transverse phonons. We compute the elastic modulus and we determine the shear sound speed which turns out to be in good agreement with the theoretical...
10/6/17, 3:00 PM
10/6/17, 3:30 PM
Information scrambling and the butterfly effect in chaotic quantum systems can be diagnosed by out-of-time-ordered (OTO) commutators through an exponential growth and large late time value. We show that the latter feature shows up in a strongly correlated many-body system, a Luttinger liquid, whose density fluctuations we study at long and short wavelengths, both in equilibrium and...
266. Microscopic model of quantum butterfly effect: out-of-time-order correlators and traveling combustion waves
10/6/17, 4:15 PM
In a chaotic classical system a small perturbation leads to the exponential divergence of trajectories characterized by Lyapunov time. As a result, the observables in two copies of the system experiencing different perturbations quickly become uncorrelated. In a many body system a local perturbation initially destroys the correlations locally, then the region where the correlations...