Scientific Series

Displaying 3457 - 3468 of 5007

Wall-Crossing and Quiver Invariants

Piljin Yi Korea Institute for Advanced Study
February 19, 2013

PIRSA:13020137
High Energy Physics
Qanti-kt: Nondeterministic jet clustering

David Krohn Harvard University
February 19, 2013

PIRSA:13020135
High Energy Physics
Fractional Quantum Hall States on an infinite cylinder: characterizing topological order and quasiparticle forces using infinite DMRG.

Michael Zaletel University of California, Berkeley
February 12, 2013

PIRSA:13020129
Condensed Matter
The structure of meaning in natural language: a big money quantum foundations spin-off.

Bob Coecke Quantinuum
February 12, 2013

PIRSA:13020131
Quantum Physics
Prospects for GW transients in early Advanced LIGO and Virgo science runs

Gabriela Gonzalez Louisiana State University
February 06, 2013

PIRSA:13020124
General Relativity & Quantum Cosmology
Looking for spinon deconfinement in two dimensions

Ying Tang Boston College
February 05, 2013

PIRSA:13020127
Condensed Matter
A positive and local formalism for quantum theory

Robert Oeckl Universidad Nacional Autónoma De Mexico (UNAM)
February 05, 2013

PIRSA:13020125
Quantum Physics
Time Crystals

Alfred Shapere University of Kentucky
February 05, 2013

PIRSA:13020121
High Energy Physics
Multifield Reheating and the Fate of the Primordial Observables

Ewan Tarrant University of Nottingham
February 05, 2013

PIRSA:13020123
Astrophysics
A classification of symmetry enriched topological phases with exactly solvable models

Ying Ran Boston College
February 01, 2013

PIRSA:13020122
Condensed Matter
Searching for topological phases in transition metal oxide heterostructures

Ying Ran Boston College
January 31, 2013

PIRSA:13010113
Condensed Matter
Hidden Structure in Linguistics: The Organization of Sound Systems

Elan Dresher

January 30, 2013

PIRSA:13010017

Wall-Crossing and Quiver Invariants

Piljin Yi Korea Institute for Advanced Study
February 19, 2013

PIRSA:13020137
High Energy Physics
We start with a one-slide review of the Kontsevich-Soibelman (KS) solution to the wall-crossing problem and then proceed to direct and comprehensive physics counting of BPS states that eventually connects to KS. We also asks what input data is needed for either approaches to produce complete BPS spectra, and this naturally leads to the BPS quiver representation of BPS states and the new notion of quiver invariants.
We propose a simple geometrical conjecture that can segregate BPS states in Higgs phases of the BPS quiver dynamics to those that experience wall-crossing and those that do not, and give
proofs for all cyclice Abelian quivers. We close with explanation of how physics distinguishes two such classes of BPS states.
Qanti-kt: Nondeterministic jet clustering

David Krohn Harvard University
February 19, 2013

PIRSA:13020135
High Energy Physics
The interpretation of events with jets is often ambiguous, especially for the sort of highly complex events one encounters at the LHC. One often finds that an event interpreted as signal-like using one choice of jet algorithm and radius parameter is no longer signal-like with another, even if the two are very similar. Here we present an extension of the Qjets procedure designed to account for this ambiguity and assign each plausible interpretation of an event a weight, so that events which are unambiguously signal-like carry more influence on one's results than events which are only marginally so. This procedure can be used with any existing analysis employing a sequential recombination algorithm like anti-kT and we will show that through its use the statistical power of an analysis often increases. In particular, we will see that a up to a 20\% improvement in statistical significance can be realized for a Higgs-like analysis searching for a resonance recoiling against an associated vector boson.
Fractional Quantum Hall States on an infinite cylinder: characterizing topological order and quasiparticle forces using infinite DMRG.

Michael Zaletel University of California, Berkeley
February 12, 2013

PIRSA:13020129
Condensed Matter
The density matrix renormalization group (DMRG), which has proved so successful in one dimension, has been making the push into higher dimensions, with the fractional quantum Hall (FQH) effect an important target. I'll briefly explain how the infinite DMRG algorithm can be adapted to find the degenerate ground states of a microscopic FQH Hamiltonian on an infinitely long cylinder, then focus on two applications. To characterize the topological order of the phase, I'll show that the bipartite entanglement spectrum of the ground state is sufficient to determine the quasiparticle charges, topological spins, quantum dimensions, chiral central charge, and Hall viscosity of the phase. Then I will show how to introduce localized quasiparticles of fixed topological charge. By pinning a pair of quasiparticles and dragging them into contact, we can directly measure the force curve of their interaction.
The structure of meaning in natural language: a big money quantum foundations spin-off.

Bob Coecke Quantinuum
February 12, 2013

PIRSA:13020131
Quantum Physics
Prospects for GW transients in early Advanced LIGO and Virgo science runs

Gabriela Gonzalez Louisiana State University
February 06, 2013

PIRSA:13020124
General Relativity & Quantum Cosmology
Advanced LIGO (aLIGO) and Advanced Virgo (AdV) are kilometer-scale gravitational wave (GW) detectors that are expected to yield the first direct observations of gravitational waves. I will describe the currently projected schedule, sensitivity, and sky localization accuracy for the GW detector network in the next decade.
Looking for spinon deconfinement in two dimensions

Ying Tang Boston College
February 05, 2013

PIRSA:13020127
Condensed Matter
We have used a recently proposed quantum Monte Carlo algorithm [1] to study spinons (emergent S = 1/2 excitations) in 2D Resonating-Valence-Bond (RVB) spin liquids and in a J-Q model hosting a Neel – Valence Bond Solid (VBS) phase transition at zero temperature [2]. We confirm that spinons are well defined quasi-particles with finite intrinsic size in the RVB spin liquid. The distance distribution between two spinons shows signatures of deconfinement.
However, at the Neel–VBS transition, we found that the size of a single spinon is significantly greater than the bound-state in VBS, which indicates that spinons are “soft” and shrink when bound state is formed. Both spinon size and confinement length diverge as the critical point is approached. We have also compared spinon statistics in J-Q model with bilayer Heisenberg model and 1D spin chain. We conclude that the spinon deconfinement is marginal in the lowest-energy state in the spin-1 sector, due to very weak attractive spinon interactions. Deconfinement in the vicinity of the critical point should occur at higher energies.
A positive and local formalism for quantum theory

Robert Oeckl Universidad Nacional Autónoma De Mexico (UNAM)
February 05, 2013

PIRSA:13020125
Quantum Physics
The general boundary formulation (GBF) is an atemporal, but spacetime local formulation of quantum theory. Usually it is presented in terms of the amplitude formalism, which, in the presence of a background time, recovers the pure state formalism of the standard formulation of quantum theory. After reviewing the essentials of the amplitude formalism I will introduce a new "positive formalism", which recovers instead a mixed state formalism. This allows to define general quantum operations within the GBF and opens it to quantum information theory. Moreover, the transition to the positive formalism eliminates operationally irrelevant structure, making the extraction of measurement probabilities more direct. As a consequence, the probability interpretation takes on a remarkably simple and compelling form. I shall describe implications of the positive formalism, both for our understanding of quantum theory and for the practical formulation of quantum theories. I also observe a certain convergence with Lucien Hardy's operator tensor formulation of quantum theory, on which I hope to comment
Time Crystals

Alfred Shapere University of Kentucky
February 05, 2013

PIRSA:13020121
High Energy Physics
I consider a class of simple classical systems which exhibit motion in their lowest-energy states and thus spontaneously break time-translation symmetry. Their Lagrangians have nonstandard kinetic terms and their Hamiltonians are multivalued functions of momentum, yet they are perfectly consistent and amenable to quantization. Field theoretical generalizations of these systems may have applications in condensed matter physics and cosmology.
Multifield Reheating and the Fate of the Primordial Observables

Ewan Tarrant University of Nottingham
February 05, 2013

PIRSA:13020123
Astrophysics
The presence of additional light fields during inflation can source isocurvature fluctuations, which can cause the curvature perturbation $\zeta$, and its statistics to evolve on superhorizon scales. I will demonstrate that if these fluctuations have not completely decayed before the onset of perturbative reheating, then primordial observables such as the level of non--Gaussianity can develop substantial reheating dependant corrections. I will argue that for inflationary models where an adiabatic condition is not reached before the relevant fields begin to decay, we must be careful in our interpretation of any observational constraints that place bounds on the statistics of $\zeta$.
A classification of symmetry enriched topological phases with exactly solvable models

Ying Ran Boston College
February 01, 2013

PIRSA:13020122
Condensed Matter
Two types of topological phases have attracted a lot of attention in condensed matter physics: symmetry protected topological(SPT) phases and topologically ordered phases. On the one hand, SPT phases are protected by given global symmetries while there is no topological order in the bulk. On the other hand, topologically ordered phases do not require symmetry and feature topological ground state degeneracy. In this talk, I present a classification of phases with both topological orders and global symmetries, equipped with local bosonic exactly solvable models. This classification, in some sense, organizes previous pieces of understandings on SPT phases, topological orders, symmetry fractionalizations, into a single framework. Solution of the exactly solvable models and measurable consequences will be discussed.
Searching for topological phases in transition metal oxide heterostructures

Ying Ran Boston College
January 31, 2013

PIRSA:13010113
Condensed Matter
In this talk I will present our recent investigations on possible topological phases in (111) heterostructures of transition metal oxide. These (111) heterstructures are promising systems to realize many 2D topological phases at high temperatures, even with strong correlations, which is hard to be achieved in conventional materials. Several examples will be discussed, including high-temperature quantum spin hall effect in LaAlO3/LaAuO3/LaAlO3 bilayer, correlation induced topological phases in LaAlO3/LaNiO3/LaAlO3 multilayer, nearly flat topological band with C=2 (C: Chern number) in SrIrO3 trilayer, and abelian/nonabelian fractional quantum hall effects in the absence of Landau levels (fractional Chern insulators). If time is allowed, I will also briefly introduce our work on classifying wavefunctions of fractional Chern/topological insulators.
Hidden Structure in Linguistics: The Organization of Sound Systems

Elan Dresher

January 30, 2013

PIRSA:13010017

I will discuss some basic notions in the theory of phonology (sound systems in language). The sounds of a language are generally assumed to be composed of smaller constituents, called features. The features that make up a sound cannot be directly obtained from its pronunciation, but rather must be inferred from the system of contrasts that are at play in a particular language. How to determine which features are contrastive presents a logical and empirical puzzle that may be interesting to students of physics, who are accustomed to explaining observable events in terms of hidden structures that cannot be directly observed.

Title	Speaker(s)	Date	Talk Type	Info link
Wall-Crossing and Quiver Invariants	Piljin Yi	2013-02-19	Scientific Series	View details
Qanti-kt: Nondeterministic jet clustering	David Krohn	2013-02-19	Scientific Series	View details
Fractional Quantum Hall States on an infinite cylinder: characterizing topological order and quasiparticle forces using infinite DMRG.	Michael Zaletel	2013-02-12	Scientific Series	View details
The structure of meaning in natural language: a big money quantum foundations spin-off.	Bob Coecke	2013-02-12	Scientific Series	View details
Prospects for GW transients in early Advanced LIGO and Virgo science runs	Gabriela Gonzalez	2013-02-06	Scientific Series	View details
Looking for spinon deconfinement in two dimensions	Ying Tang	2013-02-05	Scientific Series	View details
A positive and local formalism for quantum theory	Robert Oeckl	2013-02-05	Scientific Series	View details
Time Crystals	Alfred Shapere	2013-02-05	Scientific Series	View details
Multifield Reheating and the Fate of the Primordial Observables	Ewan Tarrant	2013-02-05	Scientific Series	View details
A classification of symmetry enriched topological phases with exactly solvable models	Ying Ran	2013-02-01	Scientific Series	View details
Searching for topological phases in transition metal oxide heterostructures	Ying Ran	2013-01-31	Scientific Series	View details
Hidden Structure in Linguistics: The Organization of Sound Systems	Elan Dresher	2013-01-30	Scientific Series	View details

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Format results

Wall-Crossing and Quiver Invariants

Qanti-kt: Nondeterministic jet clustering

Fractional Quantum Hall States on an infinite cylinder: characterizing topological order and quasiparticle forces using infinite DMRG.

The structure of meaning in natural language: a big money quantum foundations spin-off.

Prospects for GW transients in early Advanced LIGO and Virgo science runs

Looking for spinon deconfinement in two dimensions

A positive and local formalism for quantum theory

Time Crystals

Multifield Reheating and the Fate of the Primordial Observables

A classification of symmetry enriched topological phases with exactly solvable models

Searching for topological phases in transition metal oxide heterostructures

Hidden Structure in Linguistics: The Organization of Sound Systems

Wall-Crossing and Quiver Invariants

Qanti-kt: Nondeterministic jet clustering

Fractional Quantum Hall States on an infinite cylinder: characterizing topological order and quasiparticle forces using infinite DMRG.

The structure of meaning in natural language: a big money quantum foundations spin-off.

Prospects for GW transients in early Advanced LIGO and Virgo science runs

Looking for spinon deconfinement in two dimensions

A positive and local formalism for quantum theory

Time Crystals

Multifield Reheating and the Fate of the Primordial Observables

A classification of symmetry enriched topological phases with exactly solvable models

Searching for topological phases in transition metal oxide heterostructures

Hidden Structure in Linguistics: The Organization of Sound Systems