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13/14 PSI - String Theory Review - Lecture 14

Davide Gaiotto Perimeter Institute for Theoretical Physics

February 14, 2014

PIRSA:14020034
A unification of symmetric Z2 spin liquids on kagome lattice

Yuan-Ming Lu

February 14, 2014

PIRSA:14020118
Introduction to Effective Field Theories - Lecture 11

Cliff Burgess McMaster University

February 14, 2014

PIRSA:14020089
How universal is the entanglement spectrum?

Anushya Chandran Perimeter Institute for Theoretical Physics

February 14, 2014

PIRSA:14020132
13/14 PSI - Condensed Matter Review - Lecture 14

Alioscia Hamma University of Naples Federico II

February 14, 2014

PIRSA:14020107
Introduction to Quantum Field Theory for Cosmology - Lecture 12

Achim Kempf University of Waterloo

February 13, 2014

PIRSA:14020005
Introduction to Quantum Field Theory for Cosmology - Lecture 11

Achim Kempf University of Waterloo

February 13, 2014

PIRSA:14020001
Probabilistic protocols in quantum information

Joshua Combes University of Colorado Boulder
February 13, 2014

PIRSA:14020138
Quantum Information
Firewall evasion by quantum gravity

Ted Jacobson University of Maryland, College Park
February 13, 2014

PIRSA:14020136
Quantum Gravity
Are non-Fermi-liquids stable to pairing?

Max Metlitski Massachusetts Institute of Technology (MIT) - Department of Physics

February 13, 2014

PIRSA:14020143
On null singularities in general relativity

Mihalis Dafermos Princeton University
February 13, 2014

PIRSA:14020133
Strong Gravity
Gauging symmetry of 2D topological phases

Zhenghan Wang Microsoft Corporation

February 13, 2014

PIRSA:14020125

13/14 PSI - String Theory Review - Lecture 14

Davide Gaiotto Perimeter Institute for Theoretical Physics

February 14, 2014

PIRSA:14020034
A unification of symmetric Z2 spin liquids on kagome lattice

Yuan-Ming Lu

February 14, 2014

PIRSA:14020118

While there is mounting numerical evidence for a gapped Z2 spin liquid in the kagome Heisenberg model, a complete characterization of this topological phase remains to be accomplished. A defining property, the projective symmetry group (PSG) which fixes how the emergent excitations of the spin liquid phase transform under symmetry, remains to be determined. Following a Chern-Simons field theory, we show how PSG determines measurable properties of a Z2 spin liquid, such as the existence of symmetry protected gapless edge states. This fact enables us to unify two distinct types of projected wavefunctions for Z2 spin liquids: the Schwinger-boson states and the fermionic spinon states. We also provide concrete predictions for identifying the spin liquid ground state on the kagome lattice.
Introduction to Effective Field Theories - Lecture 11

Cliff Burgess McMaster University

February 14, 2014

PIRSA:14020089
How universal is the entanglement spectrum?

Anushya Chandran Perimeter Institute for Theoretical Physics

February 14, 2014

PIRSA:14020132

It is now commonly believed that the ground state entanglement spectrum (ES) exhibits universal features characteristic of a given phase. In this talk, I will present evidence to the contrary. I will show that the entanglement Hamiltonian can undergo quantum phase transitions in which its ground state and low energy spectrum exhibit singular changes, even when the physical system remains in the same phase. For broken symmetry problems, this implies that the ES and the Renyi entropies can mislead entirely, while for quantum Hall systems the ES has much less universal content than assumed to date. I will also discuss the consequences of the eigenstate thermalization hypothesis for the entanglement Hamiltonian, showing that a pure state in a sub-system can capture the properties of the reduced density matrix.
13/14 PSI - Condensed Matter Review - Lecture 14

Alioscia Hamma University of Naples Federico II

February 14, 2014

PIRSA:14020107
Introduction to Quantum Field Theory for Cosmology - Lecture 12

Achim Kempf University of Waterloo

February 13, 2014

PIRSA:14020005
Introduction to Quantum Field Theory for Cosmology - Lecture 11

Achim Kempf University of Waterloo

February 13, 2014

PIRSA:14020001
Probabilistic protocols in quantum information

Joshua Combes University of Colorado Boulder
February 13, 2014

PIRSA:14020138
Quantum Information
Probabilistic protocols in quantum information are an attempt to improve performance by occasionally reporting a better result than could be expected from a deterministic protocol. Here we show that probabilistic protocols can never improve performance beyond the quantum limits on the corresponding deterministic protocol. To illustrate this result we examine three common probabilistic protocols: probabilistic amplification, weak value amplification, and probabilistic metrology. In each of these protocols we show explicitly that the optimal deterministic protocol is better than the corresponding probabilistic protocol when the probabilistic nature of the protocol is correctly accounted for.
Firewall evasion by quantum gravity

Ted Jacobson University of Maryland, College Park
February 13, 2014

PIRSA:14020136
Quantum Gravity
It has been argued that if black hole evaporation is a unitary quantum process, then a black hole horizon must be cloaked by a "firewall", i.e. a highly excited state of local quantum fields. This reasoning is based on factorizing the Hilbert space into interior and exterior degrees of freedom. Such factorization ignores the Wheeler-deWitt constraint equation, which arises from the diffeomorphism invariance of quantum gravity. I will argue that this constraint evades the firewall.
Are non-Fermi-liquids stable to pairing?

Max Metlitski Massachusetts Institute of Technology (MIT) - Department of Physics

February 13, 2014

PIRSA:14020143

States of matter with a sharp Fermi-surface but no well-defined Landau
quasiparticles are expected to arise in a number of physical systems.
Examples include i) quantum critical points associated with the onset
of order in metals, ii) the spinon Fermi-surface (U(1) spin-liquid)
state of a Mott insulator and iii) the Halperin-Lee-Read composite
fermion charge liquid state of a half-filled Landau level. In this
talk, I will use renormalization group techniques to investigate
possible instabilities of such non-Fermi-liquids to pairing. I will
show that for a large class of phase transitions in metals, the
attractive interaction mediated by order parameter fluctuations always
leads to a superconducting instability, which preempts the
non-Fermi-liquid effects. On the other hand, the spinon Fermi-surface
and the Halperin-Lee-Read states are stable against pairing for a
sufficiently weak attractive short-range interaction. However, once
the strength of attraction exceeds a critical value, pairing sets in.
I will describe the ensuing quantum phase transition between i) the
U(1) and the Z_2 spin-liquid states, and ii) the Halperin-Lee-Read and
Moore-Read states.
On null singularities in general relativity

Mihalis Dafermos Princeton University
February 13, 2014

PIRSA:14020133
Strong Gravity
This talk will discuss the formation, structure and interaction of null singularities for
the Einstein equations, as well as what this all means for the singular boundary
of generic space times within black hole regions.
Gauging symmetry of 2D topological phases

Zhenghan Wang Microsoft Corporation

February 13, 2014

PIRSA:14020125

I will discuss the mathematical framework for gauging a local unitary finite group symmetry of a 2D topological phase of matter.

Title	Date	Collection	Type	Info
13/14 PSI - String Theory Review - Lecture 14	2014‑02‑14	13/14 PSI - String Theory Review	Course	View details
A unification of symmetric Z2 spin liquids on kagome lattice	2014‑02‑14	Emergence in Complex Systems	Conference	View details
Introduction to Effective Field Theories - Lecture 11	2014‑02‑14	Introduction to Effective Field Theories	Course	View details
How universal is the entanglement spectrum?	2014‑02‑14	Emergence in Complex Systems	Conference	View details
13/14 PSI - Condensed Matter Review - Lecture 14	2014‑02‑14	13/14 PSI - Condensed Matter Review	Course	View details
Introduction to Quantum Field Theory for Cosmology - Lecture 12	2014‑02‑13	Quantum Field Theory for Cosmology - 2014	Course	View details
Introduction to Quantum Field Theory for Cosmology - Lecture 11	2014‑02‑13	Quantum Field Theory for Cosmology - 2014	Course	View details
Probabilistic protocols in quantum information	2014‑02‑13	Perimeter Institute Quantum Discussions	Scientific Series	View details
Firewall evasion by quantum gravity	2014‑02‑13	Quantum Gravity	Scientific Series	View details
Are non-Fermi-liquids stable to pairing?	2014‑02‑13	Emergence in Complex Systems	Conference	View details
On null singularities in general relativity	2014‑02‑13	Strong Gravity	Scientific Series	View details
Gauging symmetry of 2D topological phases	2014‑02‑13	Emergence in Complex Systems	Conference	View details

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