Scientific Series

Displaying 3529 - 3540 of 5085

Newton’s Method in Cosmology Today

Bill Harp Western University
February 26, 2013

PIRSA:13020151
Astrophysics
Bounding the purification rank of mixed states

Gemma De Las Cuevas Universität Innsbruck
February 25, 2013

PIRSA:13020149
Quantum Physics
Beyond Massive Gravity

Rachel Rosen Carnegie Mellon University
February 25, 2013

PIRSA:13020134
Astrophysics
Gamma Rays at 130 GeV and How They Might Come from Dark Matter

Andrew Frey University of Winnipeg
February 21, 2013

PIRSA:13020139
Astrophysics

General Relativity & Quantum Cosmology
The Evolution of Quasars with Cosmic Time

Michael Strauss Princeton University

February 20, 2013

PIRSA:13020120
A K matrix construction of symmetry enriched phases
February 20, 2013

PIRSA:13020140
Condensed Matter
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
The structure of meaning in natural language: a big money quantum foundations spin-off.

Bob Coecke Quantinuum
February 12, 2013

PIRSA:13020131
Quantum 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
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
A positive and local formalism for quantum theory

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

PIRSA:13020125
Quantum Physics

Newton’s Method in Cosmology Today

Bill Harp Western University
February 26, 2013

PIRSA:13020151
Astrophysics
Newton’s inferences from phenomena realize an ideal of empirical success that’s richer than prediction. To realize Newton’s richer conception of empirical success a theory needs to do more than to accurately predict the phenomena it purports to explain: in addition it needs to have the phenomena accurately measure parameters of the theory. Newton’s method aims to turn theoretical questions into ones which can be empirically answered by measurements from phenomena. Propositions inferred from phenomena are provisionally accepted as guides to further research. Newton’s ideal of empirical success as agreeing measurements from diverse phenomena is appealed to in support of the radical inference to dark energy in cosmology today. Robert Kirshner (two of his PhDs share one half of 2011’s Nobel Prize in physics) gave an account of the role of cosmic microwave background measurements, to back up the supernova measurements and measurements from galaxy clustering in supporting the transition of dark energy from a wild hypothesis into an accepted background assumption that guides further research in cosmology today. This illustrates a feature of agreeing measurements from diverse phenomena that is especially important for turning data into evidence. To the extent that the sources of systematic error of the different measurements can be regarded as independent, their agreement contributes additional support for counting them as accurate rather than as mere artifacts of systematic error.
Bounding the purification rank of mixed states

Gemma De Las Cuevas Universität Innsbruck
February 25, 2013

PIRSA:13020149
Quantum Physics
A mixed state can be expressed as a sum of D tensor product matrices, where D is its operator Schmidt rank, or as the result of a purification with a purifying state of Schmidt rank D', where D' is its purification rank. The question whether D' can be upper bounded by D is important theoretically (to establish a description of mixed states with tensor networks), as well as numerically (as the first decomposition is more efficient, but the second one guarantees positive-semidefiniteness after truncation). Here we show that no upper bounds of the purification rank that depend only on operator Schmidt rank exist, but provide upper bounds that also depend on the number of eigenvalues. In addition, we formulate the approximation problem as a Semidefinite Program.
Joint work with N. Schuch, D. Perez-Garcia, and J. I. Cirac.
Beyond Massive Gravity

Rachel Rosen Carnegie Mellon University
February 25, 2013

PIRSA:13020134
Astrophysics
In the last few years there has been a burst of progress in the field of massive gravity. The construction of consistent theories in which the graviton has a small mass has in turn led to the development a new family of compelling, consistent low-energy modifications of General Relativity. These theories improve our understanding of the interplay between gravity and particle physics and provide new approaches to solving the cosmological constant problem. In this talk I will review these recent developments. I will discuss the search among these new theories for a symmetry that has the potential to address the cosmological constant problem.
Gamma Rays at 130 GeV and How They Might Come from Dark Matter

Andrew Frey University of Winnipeg
February 21, 2013

PIRSA:13020139
Astrophysics

General Relativity & Quantum Cosmology
Gamma Rays at 130 GeV and How They Might Come from Dark Matter" I'll discuss the exciting (but somewhat controversial) new discovery of a sharp gamma ray feature at 130 GeV from near the galactic center and review some other evidence that might link it to annihilation of dark matter. I will then explain the challenges in understanding how dark matter might produce this signal and explain a model or two that overcome these difficulties.
The Evolution of Quasars with Cosmic Time

Michael Strauss Princeton University

February 20, 2013

PIRSA:13020120

While the luminosity and mass distributions of quasars has evolved dramatically with cosmic time, the physical properties of quasars of a given luminosity are remarkably independent of redshift. I will describe recent results on the spectra of luminous quasars, the dark matter halos in which they sit, and the intergalactic medium of their host galaxies, that are essentially indistinguishable from moderate redshifts to z>6. The one property apparently unique to the highest-redshift quasars is that some small fraction show evidence for having very little infrared excess from hot dust. Dust obscuration is another theme in quasar studies; an appreciable fraction of the growth of black holes may be hidden at optical wavelengths by dust. I will describe searches for obscured quasars at high redshift and low, and studies of their demographics and physical properties.
A K matrix construction of symmetry enriched phases
February 20, 2013

PIRSA:13020140
Condensed Matter
We construct in the K matrix formalism concrete examples of symmetry enriched topological phases, namely intrinsically topological phases with global symmetries. We focus on the Abelian and non-chiral topological phases and demonstrate by our examples how the interplay between the global symmetry and the fusion algebra of the anyons of a topologically ordered system determines the existence of gapless edge modes protected by the symmetry and that a (quasi)-group structure can be defined among these phases. Our examples include phases that display charge fractionalization and more exotic non-local anyon exchange under global symmetry that correspond to general group extensions of the global symmetry group.
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.
The structure of meaning in natural language: a big money quantum foundations spin-off.

Bob Coecke Quantinuum
February 12, 2013

PIRSA:13020131
Quantum 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 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.
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.
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

Title	Speaker(s)	Date	Talk Type	Info link
Newton’s Method in Cosmology Today	Bill Harp	2013-02-26	Scientific Series	View details
Bounding the purification rank of mixed states	Gemma De Las Cuevas	2013-02-25	Scientific Series	View details
Beyond Massive Gravity	Rachel Rosen	2013-02-25	Scientific Series	View details
Gamma Rays at 130 GeV and How They Might Come from Dark Matter	Andrew Frey	2013-02-21	Scientific Series	View details
The Evolution of Quasars with Cosmic Time	Michael Strauss	2013-02-20	Scientific Series	View details
A K matrix construction of symmetry enriched phases		2013-02-20	Scientific Series	View details
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
The structure of meaning in natural language: a big money quantum foundations spin-off.	Bob Coecke	2013-02-12	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
Prospects for GW transients in early Advanced LIGO and Virgo science runs	Gabriela Gonzalez	2013-02-06	Scientific Series	View details
A positive and local formalism for quantum theory	Robert Oeckl	2013-02-05	Scientific Series	View details

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Format results

Newton’s Method in Cosmology Today

Bounding the purification rank of mixed states

Beyond Massive Gravity

Gamma Rays at 130 GeV and How They Might Come from Dark Matter

The Evolution of Quasars with Cosmic Time

A K matrix construction of symmetry enriched phases

Wall-Crossing and Quiver Invariants

Qanti-kt: Nondeterministic jet clustering

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

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

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

A positive and local formalism for quantum theory

Newton’s Method in Cosmology Today

Bounding the purification rank of mixed states

Beyond Massive Gravity

Gamma Rays at 130 GeV and How They Might Come from Dark Matter

The Evolution of Quasars with Cosmic Time

A K matrix construction of symmetry enriched phases

Wall-Crossing and Quiver Invariants

Qanti-kt: Nondeterministic jet clustering

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

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

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

A positive and local formalism for quantum theory