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S=1 spin liquid with fermionic excitations

Maksym Serbyn Massachusetts Institute of Technology (MIT)
March 28, 2013

PIRSA:13030113
Condensed Matter
Canonical gravity using unconstrained null initial data

Michael Reisenberger Universidad de la Republica Uruguay
March 28, 2013

PIRSA:13030092
Strong Gravity
12/13 PSI - Explorations in Particle Theory Lecture 9

David Morrissey TRIUMF
March 28, 2013

PIRSA:13030075
Particle Physics
12/13 PSI - Explorations on Quantum Information Lecture 9

David Cory Institute for Quantum Computing (IQC)
March 28, 2013

PIRSA:13030064
Quantum Information
Quoins versus Coins

Terry Rudolph Imperial College London
March 27, 2013

PIRSA:13030000
Quantum Information
12/13 PSI - Explorations in Particle Theory Lecture 8

David Morrissey TRIUMF
March 27, 2013

PIRSA:13030074
Particle Physics
12/13 PSI - Explorations on Quantum Information Lecture 8

David Cory Institute for Quantum Computing (IQC)
March 27, 2013

PIRSA:13030063
Quantum Information
Advanced General Relativity - Lecture 19

Rafael Sorkin Perimeter Institute for Theoretical Physics

March 26, 2013

PIRSA:13030027
Classifying fractionalization: symmetry classification of gapped Z2 spin liquids in two dimensions

Michael Hermele University of Colorado Boulder
March 26, 2013

PIRSA:13030116
Condensed Matter
The Quantum Steering Ellipsoid

Sania Jevtic Imperial College London
March 26, 2013

PIRSA:13030112
Quantum Foundations
Comments on short strings and Wilson loops in AdS/CFT
March 26, 2013

PIRSA:13030111
Quantum Fields and Strings
Effective field theory of the unstable top (quark)

Alexander Penin University of Alberta
March 26, 2013

PIRSA:13030090
Particle Physics

S=1 spin liquid with fermionic excitations

Maksym Serbyn Massachusetts Institute of Technology (MIT)
March 28, 2013

PIRSA:13030113
Condensed Matter
In the first part of my talk I describe a search for possible quantum spin liquid ground states for spin S=1 Heisenberg models on the triangular lattice which was motivated by recent experiments on Ba3NiSb2O9. We use representation of spin-1 via three flavors of fermionic spinon operators. The ground state where one gapless flavor of spinons with a Fermi surface coexists with d+id topological pairing of the two other flavors can explain available experimental data. Despite the existence of a Fermi surface, this spin liquid state has fully gapped bulk spin excitations. This results in a linear in-temperature specific heat and constant in-plane spin susceptibility, with an unusually high Wilson ratio. Using variational Monte Carlo technique, we show that proposed spin liquid ground state is realized in an SU(3)-invariant model with sufficiently strong ring-exchange terms. In the second part, I consider the physics of the magnetic s=1/2 impurity embedded in a S=1 spin liquid, where all three flavors of spinons have a Fermi surface. The interplay between non-Fermi-liquid behavior induced by a U(1) gauge field coupled to fermions, and a non-Fermi-liquid fixed point in the overscreened Kondo problem is studied using double expansion. The gauge field changes the physical properties of the system at the overscreened Kondo fixed point. Thus, spin-half impurity in such spin liquid can be used to probe the presence of fermionic spinons coupled to the gauge field. References: arXiv:1108.3070, arXiv:1208.3231 and arXiv:1212.5179
Canonical gravity using unconstrained null initial data

Michael Reisenberger Universidad de la Republica Uruguay
March 28, 2013

PIRSA:13030092
Strong Gravity
12/13 PSI - Explorations in Particle Theory Lecture 9

David Morrissey TRIUMF
March 28, 2013

PIRSA:13030075
Particle Physics
12/13 PSI - Explorations on Quantum Information Lecture 9

David Cory Institute for Quantum Computing (IQC)
March 28, 2013

PIRSA:13030064
Quantum Information
Quoins versus Coins

Terry Rudolph Imperial College London
March 27, 2013

PIRSA:13030000
Quantum Information
Human monkeys are used to thinking about the problem of choosing from a set of objects according to some desired, biased, probability distribution. Just think about how you chose your partner(s). Even when it is easy for you to do such a sampling, it can be difficult to do a quantum sampling (Q-Sampling) of the same distribution. By Q-Sampling I mean the creation of a coherent superposition of states of such objects whose amplitudes are the (square roots of) of the specified distribution. In this talk I will discuss what we do know about this problem, why it is interesting, and will discuss how it can let us achieve tasks with quantum information that are provably impossible classically.
12/13 PSI - Explorations in Particle Theory Lecture 8

David Morrissey TRIUMF
March 27, 2013

PIRSA:13030074
Particle Physics
12/13 PSI - Explorations on Quantum Information Lecture 8

David Cory Institute for Quantum Computing (IQC)
March 27, 2013

PIRSA:13030063
Quantum Information
Advanced General Relativity - Lecture 19

Rafael Sorkin Perimeter Institute for Theoretical Physics

March 26, 2013

PIRSA:13030027
Classifying fractionalization: symmetry classification of gapped Z2 spin liquids in two dimensions

Michael Hermele University of Colorado Boulder
March 26, 2013

PIRSA:13030116
Condensed Matter
Quantum number fractionalization is a remarkable property of topologically ordered states of matter, such as fractional quantum Hall liquids, and quantum spin liquids. For a given type of topological order, there are generally many ways to fractionalize the quantum numbers of a given symmetry. What does it mean to have different types of fractionalization? Are different types of fractionalization a universal property that can be used to distinguish phases of matter? In this talk, I will answer these questions, focusing on a simple class of topologically ordered phases, namely two-dimensional gapped Z2 spin liquids, and I will present a symmetry classification of these phases. I will also discuss efforts in progress to find microscopic models realizing different symmetry classes.
The Quantum Steering Ellipsoid

Sania Jevtic Imperial College London
March 26, 2013

PIRSA:13030112
Quantum Foundations
A quantum steering ellipsoid may be used to faithfully represent a density matrix ? describing two qubits A and B. The ellipsoid is the geometric set of states that Bob can steer Alice's qubit to when he implements all possible measurements on his qubit. We show how the correlations between qubits A and B manifest themselves in this paradigm, giving simple conditions for when the state is entangled, or has discord. We will also present novel features of the two qubit state that are revealed by the steering ellipsoid formalism, and show that a state corresponding to an ellipsoid with non-zero volume contains a new type of correlation.
Comments on short strings and Wilson loops in AdS/CFT
March 26, 2013

PIRSA:13030111
Quantum Fields and Strings
In the study of the string/gauge theory duality (AdS/CFT), an important role is played by the relation between local operators and Wilson loops. Perhaps the most well known example is the relation between twist two operators and the light-like cusp Wilson loop. On the string side, the twist two operator is represented by a "long" string (GKP). In this talk I use T-duality to argue that such relation is also natural for "short" strings. I discuss some examples and present a map between the shape of a short string crossing the Poincare horizon and the shape of a corresponding Wilson loop.
Based on arXiv:1212.4886 with Arkady Tseytlin (Imperial College).
Effective field theory of the unstable top (quark)

Alexander Penin University of Alberta
March 26, 2013

PIRSA:13030090
Particle Physics
I introduce a new nonrelativistic effective field theory which systematically accounts for the finite lifetime effects in production of unstable particles.
The theory is applied to the threshold production of top quark-antiquark pairs.

Title	Date	Collection	Type	Info
S=1 spin liquid with fermionic excitations	2013‑03‑28	Quantum Matter	Scientific Series	View details
Canonical gravity using unconstrained null initial data	2013‑03‑28	Quantum Gravity	Scientific Series	View details
12/13 PSI - Explorations in Particle Theory Lecture 9	2013‑03‑28	12/13 PSI - Explorations in Particle Theory	Course	View details
12/13 PSI - Explorations on Quantum Information Lecture 9	2013‑03‑28	12/13 PSI - Explorations on Quantum Information	Course	View details
Quoins versus Coins	2013‑03‑27	Colloquium	Scientific Series	View details
12/13 PSI - Explorations in Particle Theory Lecture 8	2013‑03‑27	12/13 PSI - Explorations in Particle Theory	Course	View details
12/13 PSI - Explorations on Quantum Information Lecture 8	2013‑03‑27	12/13 PSI - Explorations on Quantum Information	Course	View details
Advanced General Relativity - Lecture 19	2013‑03‑26	Elements of General Relativity	Course	View details
Classifying fractionalization: symmetry classification of gapped Z2 spin liquids in two dimensions	2013‑03‑26	Quantum Matter	Scientific Series	View details
The Quantum Steering Ellipsoid	2013‑03‑26	Quantum Foundations	Scientific Series	View details
Comments on short strings and Wilson loops in AdS/CFT	2013‑03‑26	Quantum Fields and Strings	Scientific Series	View details
Effective field theory of the unstable top (quark)	2013‑03‑26	Particle Physics	Scientific Series	View details

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