Scientific Series

Displaying 3553 - 3564 of 5070

Black holes: To be or not be, that is the question

Luis Garay Complutense University of Madrid
December 13, 2012

PIRSA:12120032
General Relativity & Quantum Cosmology
Adventures with Monte Carlo Simulations of the Self-Avoiding Walk

Esaias Janse van Rensburg York University

December 12, 2012

PIRSA:12120025
Quantum Chaos, Information Gain and Quantum Tomography.

Vaibhav Madhok Wilfrid Laurier University
December 11, 2012

PIRSA:12120036
Quantum Physics
(0,2) Gauge Dynamics and Flux Compactifications

Callum Quigley Kirkland & Ellis
December 11, 2012

PIRSA:12120006
High Energy Physics
A robust constraint on cosmic textures from the cosmic microwave background

Stephen Feeney
December 11, 2012

PIRSA:12120034
Astrophysics
Nonlinear Extensions for the Inflationary Power Spectra

Shun-Pei Miao Utrecht University
December 11, 2012

PIRSA:12120014
Astrophysics
Light sleptons, Higgs phenomenology and the vacuum

Stefania Gori University of California, Santa Cruz
December 07, 2012

PIRSA:12120018
High Energy Physics
CMB as a Probe of New Physics: The Story of Cosmic Birefringence
December 06, 2012

PIRSA:12120019
Astrophysics
Renormalizing TGFTs: a 3d example on SU(2)

Sylvain Carrozza University of Burgundy
December 06, 2012

PIRSA:12120007
General Relativity & Quantum Cosmology
Approaches to modeling pulsar magnetospheres

Anatoly Spitkovsky Princeton University
December 06, 2012

PIRSA:12120001
General Relativity & Quantum Cosmology
Unitarity, black hole microstates and how Alices fuzzes but may not even know it

Andrea Puhm University of Amsterdam
December 06, 2012

PIRSA:12120029
High Energy Physics
The Spectrum of Strings on Warped AdS3

Wei Song Harvard University
December 05, 2012

PIRSA:12120027
High Energy Physics

Black holes: To be or not be, that is the question

Luis Garay Complutense University of Madrid
December 13, 2012

PIRSA:12120032
General Relativity & Quantum Cosmology
I will review some problems of the black hole paradigm and explore other
possibilities for the final state of stellar collapse other than an evaporating
black hole. In particular I will use the so-called transplanckian problem as a
guide in this search for a compelling scenario for the evaporation of
ultracompact objects.
Adventures with Monte Carlo Simulations of the Self-Avoiding Walk

Esaias Janse van Rensburg York University

December 12, 2012

PIRSA:12120025

The Rosenbluth Method is a classical kinetic growth Monte Carlo algorithm for growing a self-avoiding walk by appending steps to its endpoint. This algorithm can be generalised by the implementation of more general elementary moves (for example, BFACF elementary moves) to realise kinetic growth algorithms for lattice polygons. This generalises the counting principle that underlies the Rosenbluth method and the result is a widely applicable class of algorithms which may be used for microcanonical sampling in discrete models. In addition to self-avoiding walks, several applications of kinetic growth and canonical Monte Carlo algorithms will be presented, including the sampling of trivial words in abstract groups, as well as knotted lattice polygons and discrete lattice spin systems such as the Potts model. This is work was done in collaboration with Andrew Rechnitzer of the Mathematics Department at the University of British Columbia.
Quantum Chaos, Information Gain and Quantum Tomography.

Vaibhav Madhok Wilfrid Laurier University
December 11, 2012

PIRSA:12120036
Quantum Physics
Quantum chaos is the study of quantum systems whose classical description is chaotic. How does chaos manifest itself in the quantum world? In recent years, attempts have been made to address this question from the perspective of quantum information theory. It is in this spirit that we study the connection between quantum chaos and information gain in the time series of a measurement record used for quantum tomography. The record is obtained as a sequence of expectation values of a Hermitian operator evolving under repeated application of the Floquet operator of the quantum kicked top on a large ensemble of identical systems. We find an increase in information gain and hence higher fidelities in the process when the Floquet maps employed increase in chaoticity. We make predictions for the information gain using random matrix theory in the fully chaotic regime and show a remarkable agreement between the two.
(0,2) Gauge Dynamics and Flux Compactifications

Callum Quigley Kirkland & Ellis
December 11, 2012

PIRSA:12120006
High Energy Physics
Two-dimensional gauge theories with (0,2) supersymmetry admit a much broader, and more interesting, class of solutions than their better studied (2,2) counterparts. In this talk, we will explore some of the possibilities that are offered by this additional freedom. The moduli spaces we find can be interpreted as the target spaces for heterotic strings moving in backgrounds with non-trivial H-flux. A remarkable relationship between (0,2) gauge anomalies and H-flux will emerge.
A robust constraint on cosmic textures from the cosmic microwave background

Stephen Feeney
December 11, 2012

PIRSA:12120034
Astrophysics
Fluctuations in the cosmic microwave background (CMB) contain information which has been pivotal in establishing the current cosmological model. These data can also be used to test well-motivated additions to this model, such as cosmic textures. Textures are a type of topological defect that can be produced during a cosmological phase transition in the early universe, and which leave characteristic hot and cold spots in the CMB. We apply Bayesian methods to carry out an optimal test of the texture hypothesis, using full-sky data from the Wilkinson Microwave Anisotropy Probe. We conclude that current data do not warrant augmenting the standard cosmological model with textures. We rule out at 95% confidence models that predict more than 6 detectable cosmic textures on the full sky.
Nonlinear Extensions for the Inflationary Power Spectra

Shun-Pei Miao Utrecht University
December 11, 2012

PIRSA:12120014
Astrophysics
We expound several principles in an attempt to clarify the debate over infrared loop corrections to the primordial scalar and tensor power spectra from inflation. Among other things we note that existing proposals for nonlinear extensions of the scalar fluctuation field $\zeta$ introduce new ultraviolet divergences which no one understands how to renormalize. Loop corrections and higher correlators of these putative observables would also be enhanced by inverse powers of the slow roll parameter $\epsilon$. We propose an extension which might be better behaved.
Light sleptons, Higgs phenomenology and the vacuum

Stefania Gori University of California, Santa Cruz
December 07, 2012

PIRSA:12120018
High Energy Physics
We analyze the implications for Susy theories of a Higgs to di-photon rate enhanced, if compared to the Standard Model prediction. We show how models predicting a sizable enhancement have generically an electroweak vacuum that is not absolutely stable. In particular we discuss the only viable scenario that can predict sizable new physics effects in the di-photon rate in the framework of the MSSM: a scenario with light and heavily mixed staus. We conclude with the phenomenology of this model and with the prospects of probing it at the LHC, through the direct production of light staus.
CMB as a Probe of New Physics: The Story of Cosmic Birefringence
December 06, 2012

PIRSA:12120019
Astrophysics
Cosmological birefringence is a postulated rotation of the linear polarization of photons that arises due to a Chern-Simons coupling of a new scalar field to electromagnetism. In particular, it appears as a generic feature of simple quintessence models for Dark Energy, and therefore, should it be detected, could provide insight into the microphysics of cosmic acceleration. Prior work has sought this rotation, assuming the rotation angle to be uniform across the sky, by looking for the parity-violating TB and EB correlations in the CMB temperature/polarization. However, if the scalar field that gives rise to cosmological birefringence has spatial fluctuations, then the rotation angle may vary across the sky. In this talk, I will present the results of the first CMB-based search for direction-dependent cosmological birefringence, using WMAP-7 data, and report the constraint on the rotation-angle power spectrum for all multipoles up to the resolution of the instrument. I will discuss the implications for a specific models for rotation, and show forecasts for Planck and future experiments. I will then conclude with a brief discussion of other exotic physical models, such as chiral gravity, and astrophysical scenarios, such as inhomogeneous reionization, that can be probed using the same analysis.
Renormalizing TGFTs: a 3d example on SU(2)

Sylvain Carrozza University of Burgundy
December 06, 2012

PIRSA:12120007
General Relativity & Quantum Cosmology
I will recall the main motivations for considering spin foam models in their Group Field Theory (GFT) versions, which are quantum field theories defined on group manifolds. As for any other quantum field theory, a fully consistent definition of the latter must involve renormalization. I will briefly review a specific class of GFTs, called tensorial, for which progress in this direction has recently been possible. A new just-renormalizable model, in three dimensions and on the SU(2) group, will be presented. Interestingly, it includes the geometric constraint of the Boulatov model, and might as such be related to Euclidean quantum gravity in three dimensions. Furthermore, this opens the way to a similar analysis of current 4d gravity spin foam models.
Approaches to modeling pulsar magnetospheres

Anatoly Spitkovsky Princeton University
December 06, 2012

PIRSA:12120001
General Relativity & Quantum Cosmology
Pulsars are rotating magnetized neutron stars that emit broadband pulses of radiation. Our ability to model magnetospheres of pulsars has been hampered by the difficulty of solving the self-consistent behavior of strongly magnetized relativistic plasmas. I will describe
recent progress in numerical modeling of magnetically-dominated plasmas and show applications to pulsar magnetospheres in increasing levels of realism, including ideal and resistive force-free,
relativistic MHD and kinetic models. The knowledge of the magnetospheric shape together with the new observations of gamma-ray emission from pulsars with Fermi telescope allow to directly constrain the location and physics of the acceleration regions in the magnetosphere and the origin of high energy emission. The pulsar magnetosphere is a prototype for other strongly magnetized
astrophysical objects, and I will discuss how the lessons from pulsar modeling can be useful in predicting EM counterparts to gravitational wave sources.
Unitarity, black hole microstates and how Alices fuzzes but may not even know it

Andrea Puhm University of Amsterdam
December 06, 2012

PIRSA:12120029
High Energy Physics
The information paradox and the infall problem have been long-standing puzzles in the understanding of black holes. The idea of free infall is in considerable tension with unitarity of the evaporation process and recent developements have made this tension sharp. In the first part of my talk I will address the information question and argue that unitarty requires every quantum of radiation leaving the black hole to carry information about the initial state. Unitary evaporation is thus inconsistent with an information-free horizon at every step of the evaporation process and this extends the recent firewall result. This immediately raises the question of What is the required horizon-scale structure? I will show an explicit construction of near-extremal black hole microstates which put flesh and branes on the fuzzball proposal and may realize firewalls in string theory. In the second part I will address the question of What happens to an observer falling into a fuzzball? I will argue that the answer is dependent on the energy scale of the infalling observer.
The Spectrum of Strings on Warped AdS3

Wei Song Harvard University
December 05, 2012

PIRSA:12120027
High Energy Physics
Warped AdS3 has isometry SL(2,R) x U(1). It is closed related to Kerr/CFT, non local dipole theories and AdS/CMT. In this talk I will derive the spectrum of string theory on Warped AdS3. This is possible because the worldsheet theory can be mapped to the worldsheet on AdS3 by a nonlocal field redefinition.

Title	Speaker(s)	Date	Talk Type	Info link
Black holes: To be or not be, that is the question	Luis Garay	2012-12-13	Scientific Series	View details
Adventures with Monte Carlo Simulations of the Self-Avoiding Walk	Esaias Janse van Rensburg	2012-12-12	Scientific Series	View details
Quantum Chaos, Information Gain and Quantum Tomography.	Vaibhav Madhok	2012-12-11	Scientific Series	View details
(0,2) Gauge Dynamics and Flux Compactifications	Callum Quigley	2012-12-11	Scientific Series	View details
A robust constraint on cosmic textures from the cosmic microwave background	Stephen Feeney	2012-12-11	Scientific Series	View details
Nonlinear Extensions for the Inflationary Power Spectra	Shun-Pei Miao	2012-12-11	Scientific Series	View details
Light sleptons, Higgs phenomenology and the vacuum	Stefania Gori	2012-12-07	Scientific Series	View details
CMB as a Probe of New Physics: The Story of Cosmic Birefringence		2012-12-06	Scientific Series	View details
Renormalizing TGFTs: a 3d example on SU(2)	Sylvain Carrozza	2012-12-06	Scientific Series	View details
Approaches to modeling pulsar magnetospheres	Anatoly Spitkovsky	2012-12-06	Scientific Series	View details
Unitarity, black hole microstates and how Alices fuzzes but may not even know it	Andrea Puhm	2012-12-06	Scientific Series	View details
The Spectrum of Strings on Warped AdS3	Wei Song	2012-12-05	Scientific Series	View details

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Format results

Black holes: To be or not be, that is the question

Adventures with Monte Carlo Simulations of the Self-Avoiding Walk

Quantum Chaos, Information Gain and Quantum Tomography.

(0,2) Gauge Dynamics and Flux Compactifications

A robust constraint on cosmic textures from the cosmic microwave background

Nonlinear Extensions for the Inflationary Power Spectra

Light sleptons, Higgs phenomenology and the vacuum

CMB as a Probe of New Physics: The Story of Cosmic Birefringence

Renormalizing TGFTs: a 3d example on SU(2)

Approaches to modeling pulsar magnetospheres

Unitarity, black hole microstates and how Alices fuzzes but may not even know it

The Spectrum of Strings on Warped AdS3

Black holes: To be or not be, that is the question

Adventures with Monte Carlo Simulations of the Self-Avoiding Walk

Quantum Chaos, Information Gain and Quantum Tomography.

(0,2) Gauge Dynamics and Flux Compactifications

A robust constraint on cosmic textures from the cosmic microwave background

Nonlinear Extensions for the Inflationary Power Spectra

Light sleptons, Higgs phenomenology and the vacuum

CMB as a Probe of New Physics: The Story of Cosmic Birefringence

Renormalizing TGFTs: a 3d example on SU(2)

Approaches to modeling pulsar magnetospheres

Unitarity, black hole microstates and how Alices fuzzes but may not even know it

The Spectrum of Strings on Warped AdS3