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Protected edge modes without symmetry

Michael Levin University of Chicago
May 06, 2013

PIRSA:13050026
High Energy Physics
Emergent Fermionic Strings in Bosonic He4 Crystal

Baskaran Ganapathy Institute of Mathematical Sciences
May 06, 2013

PIRSA:13050025
Condensed Matter
Topological Order with a Twist: Ising Anyons from an Abelian Model

Hector Bombin PsiQuantum Corp.
May 06, 2013

PIRSA:13050024
Quantum Physics
Quantum spin liquid phases in the absence of spin-rotation symmetry

Yong-Baek Kim University of Toronto
May 06, 2013

PIRSA:13050023
Condensed Matter
TQFTs and Topological Phases of Matter

Zhenghan Wang Microsoft Corporation
May 06, 2013

PIRSA:13050022
Mathematical Physics
3d boson topological insulators and quantum spin liquids

Senthil Todadri Massachusetts Institute of Technology (MIT) - Department of Physics
May 06, 2013

PIRSA:13050021
Condensed Matter
From Pauli's Principle to Fermionic Entanglement

Matthias Christandl ETH Zurich
May 03, 2013

PIRSA:13050005
Quantum Physics

Quantum Physics
AMS02 results support the secondary origin of cosmic ray positrons

Kfir Blum
May 03, 2013

PIRSA:13050015
High Energy Physics
An Infalling Observer in AdS/CFT and the Information Paradox

Suvrat Raju
May 03, 2013

PIRSA:13050016
High Energy Physics
Dangerous Curves: How I Learned To Stop Worrying and Love the Calculus

Jennifer Ouellette Freelance Writer

May 01, 2013

PIRSA:13050004
Quantum measurements constrained by symmetry

Leon Loveridge University of York
April 30, 2013

PIRSA:13040124
Quantum Physics
Unconventional Magnetism and Superconductivity in 3 Dimensional Doped Mott Insulators

Baskaran Ganapathy Institute of Mathematical Sciences
April 30, 2013

PIRSA:13040140
Condensed Matter

Protected edge modes without symmetry

Michael Levin University of Chicago
May 06, 2013

PIRSA:13050026
High Energy Physics
Some 2D quantum many-body systems with a bulk energy gap support gapless edge modes which are extremely robust. These modes cannot be gapped out or localized by general classes of interactions or disorder at the edge: they are "protected" by the structure of the bulk phase. Examples of this phenomena include quantum Hall states and 2D topological insulators, among others. Recently, much progress has been made in understanding protected edge modes in non-interacting fermion systems. However, less is known about the interacting case. A basic problem is to predict, for general interacting systems, when such edge modes are present or absent, and to identify the different physical mechanisms that underlie their stability. In this talk, I will discuss this problem in the simplest case: interacting fermion systems without any symmetry.
Emergent Fermionic Strings in Bosonic He4 Crystal

Baskaran Ganapathy Institute of Mathematical Sciences
May 06, 2013

PIRSA:13050025
Condensed Matter
Large zero point motion of light atoms in solid Helium 4 leads to several anomalous properties, including a supersolid type behavior. We suggest an `anisotropic quantum melted' atom density wave model for solid He4 with hcp symmetry. Here, atoms preferentially quantum melt along the c-axis and maintain self organized crystallinity and confined dynamics along ab-plane. This leads to profound consequences: i) statistics transmutation of He4 atoms into fermions for c-axis dynamics, arising from restricted one dimensional motion and hard core repulsion, ii) resulting `fermionic strings' undergo Peierls instability (an atom density wave formation) in a staggered fashion and help regain the original hcp crystal symmetry, iii) `particle-hole' type excitations iv) emergence of `confined' `half atom' domain wall excitations, and so on. Known anomalies of solid He4 gets a natural qualitative explanation in the present scenario.
Topological Order with a Twist: Ising Anyons from an Abelian Model

Hector Bombin PsiQuantum Corp.
May 06, 2013

PIRSA:13050024
Quantum Physics
Anyon models can be symmetric under some permutations of their topological charges. One can then conceive topological defects that, under monodromy, transform anyons according to a symmetry. We study the realization of such defects in the toric code model, showing that a process where defects are braided and fused has the same outcome as if they were Ising anyons.
Quantum spin liquid phases in the absence of spin-rotation symmetry

Yong-Baek Kim University of Toronto
May 06, 2013

PIRSA:13050023
Condensed Matter
We investigate possible quantum spin liquid phases in the presence of a variety of spin-rotational-symmetry breaking perturbations. Projective symmetry group analysis on slave-particle representations is used to understand possible spin liquid phases on the Kagome lattice. The results of this analysis are used to make connections to the exiting and future experiments on Herbertsmithites. Applications to other systems are also discussed.
TQFTs and Topological Phases of Matter

Zhenghan Wang Microsoft Corporation
May 06, 2013

PIRSA:13050022
Mathematical Physics
In two spatial dimensions, there is a good correspondence between TQFTs and topological phases of matter for spin systems. I will discuss this correspondence in one and three spatial dimensions for spin systems. If time permits, I will also discuss the situation for fermion systems.
3d boson topological insulators and quantum spin liquids

Senthil Todadri Massachusetts Institute of Technology (MIT) - Department of Physics
May 06, 2013

PIRSA:13050021
Condensed Matter
I will discuss recent work on 3d Symmetry Protected Topological (SPT) phases of bosonic systems, and their implications for understanding the more exotic quantum spin liquid phases. First I will describe various characterizations of these 3d SPT phases, in particular their surface effective theories and (when applicable) bulk electromagnetic response. Next I will show how this understanding leads to several new insights into the theory of both 2d and 3d quantum spin liquids. Finally I will provide an explicit construction of several 3d SPT phases in a system of `coupled layers'. This includes a 3d SPT state that is beyond the existing cohomology classification of such states.
From Pauli's Principle to Fermionic Entanglement

Matthias Christandl ETH Zurich
May 03, 2013

PIRSA:13050005
Quantum Physics

Quantum Physics
The Pauli exclusion principle is a constraint on the natural occupation numbers of fermionic states. It has been suspected for decades, and only proved very recently, that there is a multitude of further constraints on these numbers, generalizing the Pauli principle. Surprisingly, these constraints are linear: they cut out a geometric object known as a polytope. This is a beautiful mathematical result, but are there systems whose physics is governed by these constraints? In order to address this question, we studied a system of a few fermions connected by springs. As we varied the spring constant, the occupation numbers moved within the polytope. The path they traced hugs very close to the boundary of the polytope, suggesting that the generalized constraints affect the system. I will mention the implications of these findings for the structure of few-fermion ground states and then discuss the relation between the geometry of the polytope and different types of fermionic entanglement.
AMS02 results support the secondary origin of cosmic ray positrons

Kfir Blum
May 03, 2013

PIRSA:13050015
High Energy Physics
We show that the recent AMS02 positron fraction measurement is perfectly consistent with a secondary origin for positrons, and does not require additional primary sources such as pulsars or dark matter. Within the secondary model the AMS02 data imply a cosmic ray propagation time in the
Galaxy of about one Myr and an average traversed interstellar matter density of about 1/cc at a rigidity of 300 GV. These results may hint that high energy cosmic rays are confined to a thin halo of scale height similar to the gaseous disk.
An Infalling Observer in AdS/CFT and the Information Paradox

Suvrat Raju
May 03, 2013

PIRSA:13050016
High Energy Physics
We reconstruct the experience of an infalling observer using the AdS/CFT correspondence. We write operators both outside and inside the black hole in terms of CFT operators. Our construction provides a natural realization of black hole complementarity, and a way of preserving information without the need for firewalls.
Dangerous Curves: How I Learned To Stop Worrying and Love the Calculus

Jennifer Ouellette Freelance Writer

May 01, 2013

PIRSA:13050004

Based on her book, The Calculus Diaries, join, Jennifer Ouellette as she shows how calculus can be applied to everything from gas mileage, diet, the rides at Disneyland, surfing in Hawaii, shooting craps in Vegas and warding off zombies. Even the mathematically challenged, can-and-should learn the fundamentals of the universal language.
Quantum measurements constrained by symmetry

Leon Loveridge University of York
April 30, 2013

PIRSA:13040124
Quantum Physics
The Wigner-Araki-Yanase (WAY) theorem delineates circumstances under which a class of quantum measurements is ruled out. Specifically, it states that any observable (given as a self adjoint operator) not commuting with an additive conserved quantity of a quantum system and measuring apparatus combined admits no repeatable measurements. I'll review the content of this theorem and present some new work which generalises and strengthens the existing results. The observation that the WAY constraint vanishes if the observable-to-be-measured is ``relativised'' (in a suitable sense) points to interesting links with quantum reference frames and superselection rules. I'll discuss some of these connections and raise some open questions.
Unconventional Magnetism and Superconductivity in 3 Dimensional Doped Mott Insulators

Baskaran Ganapathy Institute of Mathematical Sciences
April 30, 2013

PIRSA:13040140
Condensed Matter
Utilizing a variety and also constraints offered by quantum and solid state chemistry, we discuss possibilities of unconventional quantum magnetism and superconductivity in doped 3 dimensional Mott insulators. Some of the possibilities are quantum spin liquid states having pseudo fermi surface coexisting with long range magnetic order, 3 dimensional emergent gauge fields and unconventional superconducting order parameter symmetry. We present a few realistic models to illustrate this and use our theory to understand anomalous behavior of certain double perovskite compounds.

Title	Date	Collection	Type	Info
Protected edge modes without symmetry	2013‑05‑06	Emergence & Entanglement II 2013	Conference	View details
Emergent Fermionic Strings in Bosonic He4 Crystal	2013‑05‑06	Emergence & Entanglement II 2013	Conference	View details
Topological Order with a Twist: Ising Anyons from an Abelian Model	2013‑05‑06	Emergence & Entanglement II 2013	Conference	View details
Quantum spin liquid phases in the absence of spin-rotation symmetry	2013‑05‑06	Emergence & Entanglement II 2013	Conference	View details
TQFTs and Topological Phases of Matter	2013‑05‑06	Emergence & Entanglement II 2013	Conference	View details
3d boson topological insulators and quantum spin liquids	2013‑05‑06	Emergence & Entanglement II 2013	Conference	View details
From Pauli's Principle to Fermionic Entanglement	2013‑05‑03	Colloquium	Scientific Series	View details
AMS02 results support the secondary origin of cosmic ray positrons	2013‑05‑03		Scientific Series	View details
An Infalling Observer in AdS/CFT and the Information Paradox	2013‑05‑03	Quantum Fields and Strings	Scientific Series	View details
Dangerous Curves: How I Learned To Stop Worrying and Love the Calculus	2013‑05‑01	Public Lecture Series	Public Lectures	View details
Quantum measurements constrained by symmetry	2013‑04‑30	Quantum Foundations	Scientific Series	View details
Unconventional Magnetism and Superconductivity in 3 Dimensional Doped Mott Insulators	2013‑04‑30	Quantum Matter	Scientific Series	View details

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Format results

Protected edge modes without symmetry

Emergent Fermionic Strings in Bosonic He4 Crystal

Topological Order with a Twist: Ising Anyons from an Abelian Model

Quantum spin liquid phases in the absence of spin-rotation symmetry

TQFTs and Topological Phases of Matter

3d boson topological insulators and quantum spin liquids

From Pauli's Principle to Fermionic Entanglement

AMS02 results support the secondary origin of cosmic ray positrons

An Infalling Observer in AdS/CFT and the Information Paradox

Dangerous Curves: How I Learned To Stop Worrying and Love the Calculus

Quantum measurements constrained by symmetry

Unconventional Magnetism and Superconductivity in 3 Dimensional Doped Mott Insulators

Protected edge modes without symmetry

Emergent Fermionic Strings in Bosonic He4 Crystal

Topological Order with a Twist: Ising Anyons from an Abelian Model

Quantum spin liquid phases in the absence of spin-rotation symmetry

TQFTs and Topological Phases of Matter

3d boson topological insulators and quantum spin liquids

From Pauli's Principle to Fermionic Entanglement

AMS02 results support the secondary origin of cosmic ray positrons

An Infalling Observer in AdS/CFT and the Information Paradox

Dangerous Curves: How I Learned To Stop Worrying and Love the Calculus

Quantum measurements constrained by symmetry

Unconventional Magnetism and Superconductivity in 3 Dimensional Doped Mott Insulators