# Low Energy Challenges for High Energy Physicists

Conference Date:
Monday, May 26, 2014 (All day) to Friday, May 30, 2014 (All day)
Scientific Areas:
Condensed Matter

Throughout the history of quantum field theory, there has been a rich cross-pollenation coming from the interaction between high-energy and condensed matter theory. Beginning with Dirac's positron and including such triumphs as spontaneous symmetry breaking and renormalization, this cross-talk has been instrumental in shaping our understanding of the universe. We propose to reinvigorate this fruitful collaboration by bringing together high-energy and condensed matter physicists. Scientists wtih a high-energy background have often attracted to condensed matter systems because, simply put, they are so much richer. Rather than having a single Lagrangian which describes all elementary particles and fundamental interactions we observe at colliders, the myriad of possible phases of condesed matter systems allow for a whole host of different and unusual (from a high-energy perspective) behaviour. Many high-energy physicists have recently expanded their horizons in this direction, but often at the cost of working in relative isolation. We believe that bringing together these like-minded individuals in the presence of leading condensed matter theorists will unite, focus and inspire this new community to try and tackle some of the most interesting problems in modern physics.

Carlo Barenghi, Newcastle University
Tomas Brauner, Vienna University of Technology
J.C. Seamus Davis, Cornell University
Russell Donnelly, University of Oregon
Sergei Dubovsky, New York University
Liam Fitzpatrick, Stanford University
Lam Hui, Columbia University
Sean Hartnoll, Stanford University
William Irvine, University of Chicago
Emanuel Katz, Boston University
Zohar Komargodski, Weizmann Institute
Sung-Sik Lee, Perimeter Institute
Andre LeClair, Cornell University
John McGreevy, University of California, San Diego
Sergej Moroz, University of Washington
Hitoshi Murayama, University of California, Berkeley
Riccardo Penco, Columbia University
Frederico Piazza, University of Paris
Sri Raghu, Stanford University
Rachel Rosen, Columbia University
Ira Rothstein, Carnegie Mellon University
Subir Sachdev, Harvard University
Igor Shovkovy, Arizona State University
Sergey Sibiryakov, INR Moscow
Brian Swingle, Harvard University
Dam Thanh Son, University of Chicago

• Carlo Barenghi, New Castle University
• J.C. Seamus Davis, Cornell University
• Claudia de Rham, Case Western University
• Russell Donnelly, University of Oregon
• Sergei Dubovsky, New York University
• Astrid Eichhorn, Perimeter Institute
• Solomon Endlich, École polytechnique fédérale de Lausanne
• Matteo Fasiello, Case Western Reserve University
• Liam Fitzpatrick, Stanford University
• Sean Hartnoll, Stanford University
• Lavinia Heisenberg, Case Western Reserve University
• Kurt Hinterbichler, Perimeter Institute
Lam Hui, Columbia University
• Lisa Huijse, Stanford Univerisity
• William Irvine, University of Chicago
• Austin Joyce, University of Chicago
• Jared Kaplan, Johns Hopkins University
• Emanuel Katz, Boston University
• Zohar Komargodski, Weizmann Institute
• David Kubiznak, Perimeter Institute
• Andre LeClair, Cornell University
• John McGreevy, University of California, San Diego
• Sergej Moroz, University of Washington
• Hitoshi Murayama, University of California, Berkeley
• Alberto Nicolis, Columbia University
• Riccardo Penco, Columbia University
• Frederico Piazza, University of Paris
• Raquel H. Ribeiro, Case Western University
• Rachel Rosen, Columbia University
• Ira Rothstein, Carnegie Mellon University
• Subir Sachdev, Harvard University
Igor Shovkovy, Arizona State University
• Sergey Sibiryakov, INR Moscow
• Dan Thanh Son, University of Chicago
• Brian Swingle, Harvard University
• Junpu Wang, Johns Hopkins University
• Omar Zanusso, Radboud Univeristy Nimegan

Monday, May 26th, 2014

 Time Event Location 8:30 – 9:00am Registration Reception 9:00 – 9:05am Welcome and Opening Remarks Bob Room 9:05 – 10:00am Liam Fitzpatrick, Stanford University Wilsonian and Large N Approaches to Non-Fermi Liquids Bob Room 10:00 – 10:30am Coffee Break Bistro – 1st Floor 10:30 – 11:30am Ira Rothstein, Carnegie Mellon University Sudakov Form Factor and Von-Hove Singularities Bob Room 11:30 – 12:30pm Tomas Brauner, Vienna University of Technology Nambu–Goldstone bosons: classification and effective actions Bob Room 12:30 – 2:30pm Lunch Bistro – 2nd Floor 2:30 – 3:30pm Brian Swingle, Harvard University Einstein's equations from qubits Bob Room 3:30 – 4:00pm Coffee Break Bob Room 4:00 – 5:00pm Igor Shovkovy, Arizona State University Quantum Magnetic Phenomena: From QCD to Dirac semimetals Bob Room

Tuesday, May 27th, 2014

 Time Event Location 9:00 – 10:00am J.C. Seamus Davis, Cornell University Visualizing Quantum Matter Bob Room 10:00 – 10:30am Coffee Break Bistro – 1st Floor 10:30 – 11:30am Sergej Moroz, University of Washington Effective field theory of two-dimensional nonrelativistic chiral superfluid Bob Room 11:30 – 12:30pm Sean Hartnoll, Stanford University Universal incoherent metallic transport Bob Room 12:30 – 12:40pm Conference Photo Atrium 12:40 – 3:00pm Lunch Break Bistro – 2nd Floor 3:00 – 4:00pm Condensed Matter Seminar Andrea Allais, Harvard University Phenomenology of Charge Order In Underdoped Cuprates Bob Room 4:00 – 4:30pm Coffee Break Bistro – 1st Floor 4:30 - 5:30pm Zohar Komargodski, Weizmann Institute Some Exact Results for Conformal Field Theories in d>2 Bob Room 5:30 Onwards Banquet Bistro – 2nd Floor

Wednesday, May 28th, 2014

 Time Event Location 9:00 – 10:00am Sergey Sibiryakov, EPFL, CERN From scale invariance to Lorentz symmetry Bob Room 10:00 – 10:30am Coffee Break Bistro – 1st floor 10:30 – 11:30am Russell Donnelly, University of Oregon Carlo Barenghi, Newcastle University Quantum Turbulence Bob Room 11:30 – 12:30pm Hitoshi Murayama, University of California, Berkeley What's wrong with Goldstone? Bob Room 12:30 – 2:00pm Lunch Bistro – 2nd Floor 2:00 – 3:30pm Dam Thanh Son, University of Chicago Hydrodynamics and anomalies Theatre

Thursday, May 29th, 2014

 Time Event Location 9:00 – 10:00am William Irvine, University of Chicago TBA Bob Room 10:00 – 10:30am Coffee Break Bistro – 1st Floor 10:30 – 11:30am Subir Sachdev, Harvard University Quantum matter without quasiparticles Bob Room 11:30 – 12:30pm Riccardo Penco, Columbia University Effective theories of vortex lines Bob Room 12:30 – 2:30pm Lunch Bistro – 2nd Floor 2:30 – 3:30pm Solomon Endlich, EFPL Spontaneous symmetry breaking, gravity, and spinning objects Bob Room 3:30 – 4:00pm Coffee Break Bistro – 1st Floor 4:00 - 5:00pm John McGreevy, University of California, San Diego Lattice models for anomalous field theories Bob Room 5:00 Onwards Pub Night Bistro – 1st Floor

Friday, May 30th, 2014

 Time Event Location 9:00 – 10:00am Federico Piazza, University of Paris Relativity of non relativistic systems Bob Room 10:00 – 10:30am Coffee Break Bistro – 1st floor 10:30 – 11:30am Omar Zanusso, Radboud University Functional renormalization group and statistical mechanics of membranes Bob Room 11:30 – 12:30pm Emanuel Katz, Boston University Dynamical trapping near a quantum critical point Bob Room 12:30 – 12:40pm Closing Remarks Bistro – 2nd Floor 12:40pm Onwards Lunch Bistro - 2nd  Floor

Carlo Barenghi, Newcastle University
Russell Donnelly, University of Oregon

Quantum Turbulence

This hour will be devoted to a description of quantum turbulence,that is turbulence in superfluids.  The first talk (~20 minutes) will be given by Russell Donnelly.  He will describe briefly the problem of classical turbulence and  how turbulence in superfluids is different.  The second talk will be given by Carlo Barenghi who will discuss progress in the simulation of quantum turbulence which is capable of suggesting insights so far inaccessible to experiment.

Tomas BraunerVienna University of Technology

Nambu–Goldstone bosons: classification and effective actions

I will review the development in understanding Nambu–Goldstone bosons in quantum many-body systems. Particular emphasis will be put on two topics of my recent work: spontaneous breaking of spacetime symmetries and construction of topological effective Lagrangians.

J.C. Seamus Davis, Cornell University

Visualizing Quantum Matter

Recently developed techniques allow imaging of electronic quantum matter directly at the atomic scale. I will introduce the basic principles and describe the set of observables available from these techniques.  As examples, I will survey visualization of exotic forms of electronic quantum matter including heavy fermions, quantum critical electrons, topological surface states, electronic liquid crystals, and high temperature superconductors.

Solomon Endlich, EFPL

Spontaneous symmetry breaking, gravity, and spinning objects

Space-time symmetries are a crucial ingredient of any theoretical model in physics. Unlike internal symmetries, which may or may not be gauged and/or spontaneously broken, space-time symmetries do not admit any ambiguity: they are gauged by gravity, and any conceivable physical system (other than the vacuum) is bound to break at least some of them. Motivated by this observation, I will sketch how to couple gravity with the Goldstone fields that non-linearly realize spontaneously broken space-time symmetries by weakly gauging the Poincare symmetry group in the context of the coset construction. To illustrate the power of this perspective I will build a low energy effective action that describes spinning objects coupled to gravity and describe its interpretation.

Liam Fitzpatrick, Stanford University

Wilsonian and Large N Approaches to Non-Fermi Liquids

We study the problem of metals near a quantum critical point using a local Wilsonian effective field theory of Fermi surface fermions coupled to massless boson (i.e. order parameter) fields, in particular in a large N limit where the boson is matrix-valued.  We focus on regions of parameter space where the boson dresses the fermions into a non-Fermi liquid while the bosons are approximately controlled by the Wilson-Fisher fixed point.

Sean Hartnoll, Stanford University

Universal incoherent metallic transport

In an incoherent metal, transport is controlled by the collective diffusion of energy and charge rather than by quasiparticle or momentum relaxation. We explore the possibility of a universal bound D \gtrsim \hbar v_F^2 /(k_B T) on the underlying diffusion constants in an incoherent metal. Such a bound is loosely motivated by results from holographic duality, the uncertainty principle and from measurements of diffusion in strongly interacting non-metallic systems. Metals close to saturating this bound are shown to have a linear in temperature resistivity with an underlying dissipative timescale matching that recently deduced from experimental data on a wide range of metals. The phenomenology of universal incoherent transport is found to reproduce various further observations in strongly correlated metals, and motivates direct probes of diffusive processes and measurements of charge susceptibilities. We suggest that this bound may be responsible for the ubiquitous appearance of high temperature regimes in metals with T-linear resistivity.

Emanuel Katz, Boston University

Dynamical trapping near a quantum critical point

We consider a closed system where the parameter controlling a quantum phase transition is promoted to a dynamical field interacting with the quantum critical theory.  In the case that the field has an energy extensive in the volume we can treat its evolution classically.  We find that the field can become trapped near the phase transition point due to its interactions with the degrees of freedom of the quantum critical theory.  The trapping/untrapping transition can be understood using Kibble-Zurek scaling arguments. We check the general framework numerically in the particular case of the 1D transverse field Ising chain, where the transverse magnetic field is dynamical.  This constitutes a dynamical mechanism for tuning a relevant parameter to zero through a non-equilibrium process.

Zohar Komargodski, Weizmann Institute

Some Exact Results for Conformal Field Theories in d>2

John McGreevy, University of California, San Diego

Lattice models for anomalous field theories

Sergej Moroz, University of Washington

Effective field theory of two-dimensional nonrelativistic chiral superfluid

Due to the current search of Majorana fermions, the physics of two-dimensional identical fermions with short-range p-wave interactions is of considerable interest. My talk will be about the effective theory of a chiral p+ip fermionic superfluid at zero temperature. This theory naturally incorporates the parity and time reversal violating effects such as the Hall viscosity and the edge current. I will present some applications of this theory such as the linear response to external electromagnetic and gravitational fields and the density profile of an isolated vortex. Finally, the dual gauge reformulation of this theory will be presented.

Hitoshi Murayama, University of California, Berkeley

What's wrong with Goldstone?

Spontaneous Symmetry Breaking is a very universal concept applicable for a wide range of subjects: crystal, superfluid, neutron stars, Higgs boson, magnets, and many others. Yet there is a variety in the spectrum of gapless excitations even when the symmetry breaking patterns are the same. We unified all known examples in a single-line Lagrangian of the low-energy effective theory.

Riccardo Penco, Columbia University

Effective theories of vortex lines

Vortex lines are a distinctive feature of superfluids and are characterized by a very peculiar dynamics. In this talk, I will first discuss the behavior of vortex lines in a non-relativistic superfluids in the incompressible limit. I will then introduce an effective theory of vortex lines coupled to sound which applies to relativistic superfluids. I will conclude by briefly discussing the similarities between the effective theory for vortex lines and non-relativistic General Relativity.

Federico Piazza, University of Paris

Relativity of non relativistic systems

To the best of our knowledge, the fundamental laws of physics are Lorentz invariant. This means that condensed matter systems at finite density still display full Lorentz symmetry: it is just spontaneously broken (i.e. by state considered) and thus non-linearly realized. This simple observation allows to derive exact results about the spectrum of theories at finite charge density and suggests to classify condensed matter systems according to all the inequivalent ways in which boosts can be spontaneously broken.

Ira Rothstein, Carnegie Mellon University

Sudakov Form Factor and Von-Hove Singularities

In this talk I will discuss the analogies between high energy scattering  of nucleons
and Fermi Liquid theory. In particular I will elucidate the relation between the
rapidity renormalization group utilized in such observables as transverse momentum
distribution and the effect of Von-Hove singularities on the low energy properties
of metals.

Subir Sachdev, Harvard University

Quantum matter without quasiparticles

Modern materials abound in systems to which the quasiparticle picture does not apply, and developing their theoretical description remains an important challenge in condensed matter physics. I will describe recent progress in understanding the dynamics of two systems without quasiparticles: (i) ultracold atoms in optical lattices, and (ii) the nematic quantum critical point of metals with applications to the strange metal’ found in the high temperature superconductors. A combination of field-theoretic, holographic, and numerical methods will be used.

Igor Shovkovy, Arizona State University

Quantum Magnetic Phenomena: From QCD to Dirac semimetals

Studies of relativistic matter in strong magnetic fields attracted a lot of attention in recent years. Such studies are primarily motivated by the phenomenology of compact stars, the evolution of the Early Universe, and the physics of relativistic heavy ion collisions. Additionally, the outcomes of such research result in deeper understanding of a large class of novel condensed matter materials (e.g., graphene and Dirac semimetals. I will review recent surprises, ideas, and the progress made in understanding physical properties of relativistic matter in strong magnetic fields.

Sergey Sibiryakov, EPFL, CERN

From scale invariance to Lorentz symmetry

I will discuss the enhancement of space-time symmetries to Lorentz (rotation) invariance at the renormalization group fixed points of non-relativistic (anisotropic) field theories. Upon describing examples from the condensed matter physics, I will review the general argument for the stability of the infrared fixed points with the enhanced symmetry. Then I will focus on unitary field theories in (1+1) space-time dimensions which are invariant under translations, isotropic scale transformations and satisfy the requirement that the velocity of signal propagation is bounded from above. No a priori Lorentz invariance will be assumed. Still, I will prove that above properties are sufficient to ensure the existence of an infinite dimensional symmetry given by one or a product of several copies of conformal algebra. In particular, this implies presence of one or several Lorentz groups acting on the operator algebra of the theory. I will conclude by discussing the challenges in extending this result to higher space-time dimensions.

Dan Thanh Son, University of Chicago

Hydrodynamics and anomalies

Recently its has been found that relativistic hydrodynamics requires modifications in the presence of quantum anomalies. We will follow the theoretical developments that leads to this discovery and look at modern applications of hydrodynamics with anomalies.

Brian Swingle, Harvard University

Einstein's equations from qubits

I will outline a path by which a semi-classical geometry obeying Einstein's equations emerges holographically from elementary quantum mechanical objects undergoing local dynamics.  The key idea is that entanglement between the quantum degrees of freedom leads to the emergence of a dynamical geometry, that entanglement is the fabric of spacetime. Furthermore, although important technical challenges remain, I will argue that the conceptual ideas are in place.  The core of the talk will be two new results that are crucial to this program, one establishing a new representation of entanglement in RG tensor networks and the other showing that the equivalence principle is encoded in the universality of entanglement.

Omar Zanusso, SISSA

Functional renormalization group and statistical mechanics of membranes

We will first review the rich variety of universality classes of membranes and the various models developed to describe their mechanical properties. We will then discuss the recent applications of the non-perturbative renormalization group to these models aimed at improving the understanding of the membranes' phase-space beyond the epsilon-expansion. Finally, we will comment on the implications of these results on various physical systems.

## Dynamical trapping near a quantum critical point

Friday May 30, 2014
Speaker(s):

We consider a closed system where the parameter controlling a quantum phase transition is promoted to a dynamical field interacting with the quantum critical theory. In the case that the field has an energy extensive in the volume we can treat its evolution classically. We find that the field can become trapped near the phase transition point due to its interactions with the degrees of freedom of the quantum critical theory. The trapping/untrapping transition can be understood using Kibble-Zurek scaling arguments.

## Functional renormalization group and statistical mechanics of membranes

Friday May 30, 2014
Speaker(s):

We will first review the rich variety of universality classes of membranes and the various models developed to describe their mechanical properties. We will then discuss the recent applications of the non-perturbative renormalization group to these models aimed at improving the understanding of the membranes' phase-space beyond the epsilon-expansion. Finally, we will comment on the implications of these results on various physical systems.

## Relativity of non relativistic systems

Friday May 30, 2014
Speaker(s):

To the best of our knowledge, the fundamental laws of physics are Lorentz invariant. This means that condensed matter systems at finite density still display full Lorentz symmetry: it is just spontaneously broken (i.e. by state considered) and thus non-linearly realized. This simple observation allows to derive exact results about the spectrum of theories at finite charge density and suggests to classify condensed matter systems according to all the inequivalent ways in which boosts can be spontaneously broken.

## Lattice models for anomalous field theories

Thursday May 29, 2014
Speaker(s):

## Spontaneous symmetry breaking, gravity, and spinning objects

Thursday May 29, 2014
Speaker(s):

Space-time symmetries are a crucial ingredient of any theoretical model in physics. Unlike internal symmetries, which may or may not be gauged and/or spontaneously broken, space-time symmetries do not admit any ambiguity: they are gauged by gravity, and any conceivable physical system (other than the vacuum) is bound to break at least some of them.

## Effective theories of vortex lines

Thursday May 29, 2014
Speaker(s):

Vortex lines are a distinctive feature of superfluids and are characterized by a very peculiar dynamics. In this talk, I will first discuss the behavior of vortex lines in a non-relativistic superfluids in the incompressible limit. I will then introduce an effective theory of vortex lines coupled to sound which applies to relativistic superfluids. I will conclude by briefly discussing the similarities between the effective theory for vortex lines and non-relativistic General Relativity.

## Quantum matter without quasiparticles

Thursday May 29, 2014
Speaker(s):

Modern materials abound in systems to which the quasiparticle picture does not apply, and developing their theoretical description remains an important challenge in condensed matter physics. I will describe recent progress in understanding the dynamics of two systems without quasiparticles: (i) ultracold atoms in optical lattices, and (ii) the nematic quantum critical point of metals with applications to the strange metal’ found in the high temperature superconductors. A combination of field-theoretic, holographic, and numerical methods will be used.

## Hydrodynamics and anomalies

Wednesday May 28, 2014
Speaker(s):

Recently its has been found that relativistic hydrodynamics requires modifications in the presence of quantum anomalies. We will follow the theoretical developments that leads to this discovery and look at modern applications of hydrodynamics with anomalies.

## What's wrong with Goldstone?

Wednesday May 28, 2014

Spontaneous Symmetry Breaking is a very universal concept applicable for a wide range of subjects: crystal, superfluid, neutron stars, Higgs boson, magnets, and many others. Yet there is a variety in the spectrum of gapless excitations even when the symmetry breaking patterns are the same. We unified all known examples in a single-line Lagrangian of the low-energy effective theory.

## Quantum Turbulence

Wednesday May 28, 2014
Speaker(s):

This hour will be devoted to a description of quantum turbulence,that is turbulence in superfluids. The first talk (~20 minutes) will be given by Russell Donnelly. He will describe briefly the problem of classical turbulence and how turbulence in superfluids is different. The second talk will be given by Carlo Barenghi who will discuss progress in the simulation of quantum turbulence which is capable of suggesting insights so far inaccessible to experiment.

## Pages

Scientific Organizers:

Solomon Endlich, École polytechnique fédérale de Lausanne
Walter Goldberger, Yale University
Kurt Hinterbichler, Perimeter Institute
Alberto Nicolis, Columbia University
Riccardo Penco, Columbia University
Ricardo Rattazzi, École polytechnique fédérale de Lausanne