Scientific Series

Displaying 3409 - 3420 of 5007

Three-point functions: SFT, integrability, and perturbative calculations.
April 02, 2013

PIRSA:13040110
High Energy Physics
To Split or Not to Split

Asimina Arvanitaki Perimeter Institute
April 02, 2013

PIRSA:13040115
High Energy Physics
Shake, Rattle and Explode: Short GRBs and the Electromagnetic Counterparts of Gravitational Wave Sources

Edo Berger Harvard University
April 02, 2013

PIRSA:13040081
Astrophysics

General Relativity & Quantum Cosmology
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
General Relativity & Quantum Cosmology
Quoins versus Coins

Terry Rudolph Imperial College London
March 27, 2013

PIRSA:13030000
Quantum Physics
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 Physics
Comments on short strings and Wilson loops in AdS/CFT
March 26, 2013

PIRSA:13030111
High Energy Physics
Effective field theory of the unstable top (quark)

Alexander Penin University of Alberta
March 26, 2013

PIRSA:13030090
High Energy Physics
Supersymmetric gauge theory and the Yangian - continued

Kevin Costello Perimeter Institute for Theoretical Physics

March 26, 2013

PIRSA:13030115
Wick's theorem for Matrix Product states

Robert Huebener Freie Universität Berlin
March 25, 2013

PIRSA:13030117
Quantum Physics

Three-point functions: SFT, integrability, and perturbative calculations.
April 02, 2013

PIRSA:13040110
High Energy Physics
I discuss several recent efforts in relating string field theory calculations of BMN BMN BMN and BMN BMN BPS correlation functions to direct perturbative calculations and integrability-assisted methods. I review the next-to-leading order agreement between strings and perturbation theory in the SO(6) sector, a conjectured extension of the integrability techniques by Escobedo, Gromov, Sever, Vieira from the SU(2) to the full SO(6) sector and agreement with SFT and PT in it at the leading order; finally, I discuss the issue of equating exactly extremal and non-extremal correlators at NLO in the integrability-assisted calculation.
To Split or Not to Split

Asimina Arvanitaki Perimeter Institute
April 02, 2013

PIRSA:13040115
High Energy Physics
Physics is at a crossroad that leads either to Naturalness or the Multiverse. While the confirmation of gauge coupling unification in the early 90s gave a tremendous boost to naturalness and to low energy SUSY, the lack of evidence for new physics beyond the standard model at the LHC points to a paucity of new particles near the weak scale. This suggests that the weak scale is tuned and that supersymmetry, if present at all, is realized at higher energies. This points to Split SUSY, a framework motivated by the String Landscape. Fine-tuning electroweak symmetry breaking and the renormalization group evolution of the scalar masses constrains Split model building and I review the expectations at the LHC for the different possible Split SUSY particle spectra.
Shake, Rattle and Explode: Short GRBs and the Electromagnetic Counterparts of Gravitational Wave Sources

Edo Berger Harvard University
April 02, 2013

PIRSA:13040081
Astrophysics

General Relativity & Quantum Cosmology
The bimodality of gamma-ray burst (GRB) durations points to distinct progenitor classes for the long- and short-duration GRBs. While the progenitors of long-duration GRBs are now known to be massive stars, the progenitors of short-duration GRBs remain unidentified. In this talk I will discuss the discovery of short GRB afterglow and their host galaxies, detailed studies of their environments from parsec to galactic scales, and studies of their energetics and beaming. Taken together, these observations point to the coalescence of NS-NS/NS-BH binaries as the most likely progenitors. With the upcoming Advanced LIGO/VIRGO gravitational wave detectors it is therefore possible that short GRBs will be the first detected sources, and I will discuss various approaches to making this connection between gravitational wave and electromagnetic sources.
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
General Relativity & Quantum Cosmology
Quoins versus Coins

Terry Rudolph Imperial College London
March 27, 2013

PIRSA:13030000
Quantum Physics
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.
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 Physics
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
High Energy Physics
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
High Energy 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.
Supersymmetric gauge theory and the Yangian - continued

Kevin Costello Perimeter Institute for Theoretical Physics

March 26, 2013

PIRSA:13030115

I'll explain a new connection between supersymmetric gauge theories and the Yangian. The main result is that a twisted, deformed version of the pure N=1 supersymmetric gauge theory is controlled by the Yangian, in the same way that Chern-Simons theory is controlled by the quantum group. This result is used to give an exact calculation, in perturbation theory, of the expectation value of a certain net of n+m Wilson operators in the deformed N=1 gauge theory. This expectation value coincides with the partition function of a spin-chain integrable lattice model on an n-by-m doubly-periodic lattice.
Wick's theorem for Matrix Product states

Robert Huebener Freie Universität Berlin
March 25, 2013

PIRSA:13030117
Quantum Physics
Matrix product states and their continuous analogues are variational classes of states that capture quantum many-body systems or quantum fields with low entanglement; they are at the basis of the density-matrix renormalization group method and continuous variants thereof. In this talk we show that, generically, N-point functions of arbitrary operators in discrete and continuous translation invariant matrix product states are completely characterized by the corresponding two- and three-point functions. Aside from having important consequences for the structure of correlations in quantum states with low entanglement, this result provides a new way of reconstructing unknown states from correlation measurements e.g. for one-dimensional continuous systems of cold atoms. We argue that such a relation of correlation functions may help in devising perturbative approaches to interacting theories.

Joint work with Andrea Mari and Jens Eisert.
arXiv:1207.6537

Title	Speaker(s)	Date	Talk Type	Info link
Three-point functions: SFT, integrability, and perturbative calculations.		2013-04-02	Scientific Series	View details
To Split or Not to Split	Asimina Arvanitaki	2013-04-02	Scientific Series	View details
Shake, Rattle and Explode: Short GRBs and the Electromagnetic Counterparts of Gravitational Wave Sources	Edo Berger	2013-04-02	Scientific Series	View details
S=1 spin liquid with fermionic excitations	Maksym Serbyn	2013-03-28	Scientific Series	View details
Canonical gravity using unconstrained null initial data	Michael Reisenberger	2013-03-28	Scientific Series	View details
Quoins versus Coins	Terry Rudolph	2013-03-27	Scientific Series	View details
Classifying fractionalization: symmetry classification of gapped Z2 spin liquids in two dimensions	Michael Hermele	2013-03-26	Scientific Series	View details
The Quantum Steering Ellipsoid	Sania Jevtic	2013-03-26	Scientific Series	View details
Comments on short strings and Wilson loops in AdS/CFT		2013-03-26	Scientific Series	View details
Effective field theory of the unstable top (quark)	Alexander Penin	2013-03-26	Scientific Series	View details
Supersymmetric gauge theory and the Yangian - continued	Kevin Costello	2013-03-26	Scientific Series	View details
Wick's theorem for Matrix Product states	Robert Huebener	2013-03-25	Scientific Series	View details

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Format results

Three-point functions: SFT, integrability, and perturbative calculations.

To Split or Not to Split

Shake, Rattle and Explode: Short GRBs and the Electromagnetic Counterparts of Gravitational Wave Sources

S=1 spin liquid with fermionic excitations

Canonical gravity using unconstrained null initial data

Quoins versus Coins

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

The Quantum Steering Ellipsoid

Comments on short strings and Wilson loops in AdS/CFT

Effective field theory of the unstable top (quark)

Supersymmetric gauge theory and the Yangian - continued

Wick's theorem for Matrix Product states

Three-point functions: SFT, integrability, and perturbative calculations.

To Split or Not to Split

Shake, Rattle and Explode: Short GRBs and the Electromagnetic Counterparts of Gravitational Wave Sources

S=1 spin liquid with fermionic excitations

Canonical gravity using unconstrained null initial data

Quoins versus Coins

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

The Quantum Steering Ellipsoid

Comments on short strings and Wilson loops in AdS/CFT

Effective field theory of the unstable top (quark)

Supersymmetric gauge theory and the Yangian - continued

Wick's theorem for Matrix Product states