Talks

11557 - 11568 of 19959 Results

13/14 PSI - Explorations in Cosmology - Lecture 10

Matthew Johnson York University

April 21, 2014

PIRSA:14040055
13/14 PSI - Explorations in Particle Theory - Lecture 10

Brian Shuve Harvey Mudd College

April 21, 2014

PIRSA:14040016
Compact objects as dark-matter probes

Paolo Pani Instituto Superior Tecnico - Departamento de Física

April 17, 2014

PIRSA:14040078

General Relativity & Quantum Cosmology
Universal problems

David Mattingly University of New Hampshire

April 17, 2014

PIRSA:14040074

General Relativity & Quantum Cosmology
13/14 PSI - Explorations in Cosmology - Lecture 9

Matthew Johnson York University

April 17, 2014

PIRSA:14040051
13/14 PSI - Explorations in Particle Theory - Lecture 9

Brian Shuve Harvey Mudd College

April 17, 2014

PIRSA:14030058
Exact Classical Simulation of the Quantum-Mechanical GHZ Distribution

Gilles Brassard Université de Montréal

April 16, 2014

PIRSA:14040060

Quantum Physics
13/14 PSI - Explorations in Cosmology - Lecture 8

Matthew Johnson York University

April 16, 2014

PIRSA:14040050
13/14 PSI - Explorations in Particle Theory - Lecture 8

Brian Shuve Harvey Mudd College

April 16, 2014

PIRSA:14030055
Categories of Convex Sets and C*-Algebras

Robert Furber Radboud Universiteit Nijmegen

April 15, 2014

PIRSA:14040140

Quantum Physics
Boson Tagging with Wavelets

William Shepherd University of California, Santa Cruz

April 15, 2014

PIRSA:14040063

High Energy Physics
Groups and Clusters of Galaxies: Where Cosmology and Astrophysics Collide

Arif Babul University of Victoria

April 15, 2014

PIRSA:14040133

Astrophysics

13/14 PSI - Explorations in Cosmology - Lecture 10

Matthew Johnson York University

April 21, 2014

PIRSA:14040055
13/14 PSI - Explorations in Particle Theory - Lecture 10

Brian Shuve Harvey Mudd College

April 21, 2014

PIRSA:14040016
Compact objects as dark-matter probes

Paolo Pani Instituto Superior Tecnico - Departamento de Física

April 17, 2014

PIRSA:14040078

General Relativity & Quantum Cosmology

In the last few years the possibility of constraining dark matter with astrophysical observations of compact objects, such as white dwarfs, neutron stars and black holes, has been explored. The ultra-high density interior of neutron stars and the strong-curvature regions near massive black holes make these objects unique laboratories to test weakly-interacting particles. In the first part of this talk I will review some recent work on the potential of compact objects as dark-matter detectors, including the consequences of dark-matter accretion on compact stars and superradiant black-hole instabilities triggered by ultralight bosons. In the second part I will discus how observations of neutron stars can be used to constrain the dark-matter fraction in primordial black holes. In a close encounter with a neutron star, a primordial black hole can get gravitationally captured due to accretion, dynamical friction and tidal heating. Within a short time, the black hole is trapped inside the star and disrupts it by rapid accretion. The mere existence of old neutron stars limits the abundance of primordial black holes in the only mass range that was still unconstrained, thus suggesting that these objects cannot be the dominant dark matter constituent.
Universal problems

David Mattingly University of New Hampshire

April 17, 2014

PIRSA:14040074

General Relativity & Quantum Cosmology

Arguments that gravity cannot be a local renormalizable quantum field theory come from both field theory lore and black hole physics. Two current approaches to quantum gravity, asymptotic safety and Horava-Lifshitz gravity, both of which treat quantum gravity as a local renormalizable QFT, are explicitly constructed to counter field theory arguments about the non-renormalizability of gravity. However, any proposed renormalizable theory of quantum gravity must also answer black hole physics based counter-arguments. Formulating these arguments concretely requires understanding black hole solutions and thermodynamics in these theories. For Horava-Lifshitz gravity this entails understanding the thermodynamics of universal horizons. I describe the current status of universal horizon physics and which aspects are/are not still in tension with the fundamental premise of renormalizability.
13/14 PSI - Explorations in Cosmology - Lecture 9

Matthew Johnson York University

April 17, 2014

PIRSA:14040051
13/14 PSI - Explorations in Particle Theory - Lecture 9

Brian Shuve Harvey Mudd College

April 17, 2014

PIRSA:14030058
Exact Classical Simulation of the Quantum-Mechanical GHZ Distribution

Gilles Brassard Université de Montréal

April 16, 2014

PIRSA:14040060

Quantum Physics

John Bell has shown that the correlations entailed by quantum mechanics cannot be reproduced by a classical process involving non-communicating parties. But can they be simulated with the help of bounded communication? This problem has been studied for more than twenty years and it is now well understood in the case of bipartite entanglement. However, the issue was still widely open for multipartite entanglement, even for the simplest case, which is the tripartite Greenberger-Horne-Zeilinger (GHZ) state. We give an exact simulation of arbitrary independent von Neumann measurements on general n-partite GHZ states. Our protocol requires O(n^2) bits of expected communication between the parties, and O(n log n) expected time is sufficient to carry it out in parallel. Furthermore, we need only an expectation of O(n) independent unbiased random bits, with no need for the generation of continuous real random variables nor prior shared random variables. In the case of equatorial measurements, we improve earlier results with a protocol that needs only O(n log n) bits of communication and O(log^2 n) parallel time. At the cost of a slight increase in the number of bits communicated, these tasks can be accomplished with a constant expected number of rounds.
13/14 PSI - Explorations in Cosmology - Lecture 8

Matthew Johnson York University

April 16, 2014

PIRSA:14040050
13/14 PSI - Explorations in Particle Theory - Lecture 8

Brian Shuve Harvey Mudd College

April 16, 2014

PIRSA:14030055
Categories of Convex Sets and C*-Algebras

Robert Furber Radboud Universiteit Nijmegen

April 15, 2014

PIRSA:14040140

Quantum Physics

The start of the talk will be an outline how the ordinary notions of quantum theory translate into the category of C*-algebras, where there are several possible choices of morphisms. The second half will relate this to a category of convex sets used as state spaces. Alfsen and Shultz have characterized the convex sets arising from state spaces C*-algebras and this result can be applied to get a categorical equivalence between C*-algebras and state spaces of C*-algebras which is a generalization of the equivalence between the Schroedinger and Heisenberg pictures.
Boson Tagging with Wavelets

William Shepherd University of California, Santa Cruz

April 15, 2014

PIRSA:14040063

High Energy Physics

I'll present a proof-of-concept new technique for tagging boosted objects which decay into two colored particles based on the wavelet transform. It is able to moderately improve the sensitivity of searches for such particles by 6-7%. I will also discuss future directions of applicability.
Groups and Clusters of Galaxies: Where Cosmology and Astrophysics Collide

Arif Babul University of Victoria

April 15, 2014

PIRSA:14040133

Astrophysics

Groups and clusters of galaxies are the most massive gravitationally bound objects in the Universe. They are also the most recent cosmic objects to form. In the currently accepted models of cosmic structure formation, the number density distribution of the most massive of these systems, and how this has been changing with time, depend sensitively to the parameters describing the large-scale geometry and the expansion history of the universe. However, to exploit galaxy clusters as cosmological probes, we must be able to relate their observable properties to their total mass. I will discuss our ongoing effort to calibrate the X-ray/SZ observations to the total mass for the 50 clusters comprising the Canadian Cluster Comparison Project (CCCP) sample. Resulting scaling relations, the associated scatter, and even how these change with time, invariably depend on "astrophysics" unfolding in these systems. The precision with which the cosmological parameters can be determined depends critically on how well we understand why groups and clusters manifest the observed properties that they do. This, however, has proven challenging. I will provide an update of the current state of affairs and highlight some of the key gaps in our understanding of the underlying physics.

Title	Date	Collection	Type	Info
13/14 PSI - Explorations in Cosmology - Lecture 10	2014‑04‑21	13/14 PSI - Explorations in Cosmology	Course	View details
13/14 PSI - Explorations in Particle Theory - Lecture 10	2014‑04‑21	13/14 PSI - Explorations in Particle Theory	Course	View details
Compact objects as dark-matter probes	2014‑04‑17	Strong Gravity	Scientific Series	View details
Universal problems	2014‑04‑17	Quantum Gravity	Scientific Series	View details
13/14 PSI - Explorations in Cosmology - Lecture 9	2014‑04‑17	13/14 PSI - Explorations in Cosmology	Course	View details
13/14 PSI - Explorations in Particle Theory - Lecture 9	2014‑04‑17	13/14 PSI - Explorations in Particle Theory	Course	View details
Exact Classical Simulation of the Quantum-Mechanical GHZ Distribution	2014‑04‑16	Colloquium	Scientific Series	View details
13/14 PSI - Explorations in Cosmology - Lecture 8	2014‑04‑16	13/14 PSI - Explorations in Cosmology	Course	View details
13/14 PSI - Explorations in Particle Theory - Lecture 8	2014‑04‑16	13/14 PSI - Explorations in Particle Theory	Course	View details
Categories of Convex Sets and C*-Algebras	2014‑04‑15	Quantum Foundations	Scientific Series	View details
Boson Tagging with Wavelets	2014‑04‑15	Particle Physics	Scientific Series	View details
Groups and Clusters of Galaxies: Where Cosmology and Astrophysics Collide	2014‑04‑15	Cosmology and Gravitation	Scientific Series	View details

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Format results

13/14 PSI - Explorations in Cosmology - Lecture 10

13/14 PSI - Explorations in Particle Theory - Lecture 10

Compact objects as dark-matter probes

Universal problems

13/14 PSI - Explorations in Cosmology - Lecture 9

13/14 PSI - Explorations in Particle Theory - Lecture 9

Exact Classical Simulation of the Quantum-Mechanical GHZ Distribution

13/14 PSI - Explorations in Cosmology - Lecture 8

13/14 PSI - Explorations in Particle Theory - Lecture 8

Categories of Convex Sets and C*-Algebras

Boson Tagging with Wavelets

Groups and Clusters of Galaxies: Where Cosmology and Astrophysics Collide

13/14 PSI - Explorations in Cosmology - Lecture 10

13/14 PSI - Explorations in Particle Theory - Lecture 10

Compact objects as dark-matter probes

Universal problems

13/14 PSI - Explorations in Cosmology - Lecture 9

13/14 PSI - Explorations in Particle Theory - Lecture 9

Exact Classical Simulation of the Quantum-Mechanical GHZ Distribution

13/14 PSI - Explorations in Cosmology - Lecture 8

13/14 PSI - Explorations in Particle Theory - Lecture 8

Categories of Convex Sets and C*-Algebras

Boson Tagging with Wavelets

Groups and Clusters of Galaxies: Where Cosmology and Astrophysics Collide