Talks

10573 - 10584 of 16661 Results

A robust constraint on cosmic textures from the cosmic microwave background

Stephen Feeney

December 11, 2012

PIRSA:12120034

Cosmology
Nonlinear Extensions for the Inflationary Power Spectra

Shun-Pei Miao Utrecht University

December 11, 2012

PIRSA:12120014

Cosmology
Mathematica - Lecture 3b

Pedro Vieira Perimeter Institute for Theoretical Physics

December 10, 2012

PIRSA:12120021

Mathematical physics
Mathematica - Lecture 3a

Pedro Vieira Perimeter Institute for Theoretical Physics

December 10, 2012

PIRSA:12120020

Mathematical physics
Light sleptons, Higgs phenomenology and the vacuum

Stefania Gori University of California, Santa Cruz

December 07, 2012

PIRSA:12120018

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

December 06, 2012

PIRSA:12120019

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

Sylvain Carrozza University of Burgundy

December 06, 2012

PIRSA:12120007

Quantum Gravity
Quantum one-time programs

Gus Gutowski Institute for Quantum Computing (IQC)

December 06, 2012

PIRSA:12120028

Quantum Information
Approaches to modeling pulsar magnetospheres

Anatoly Spitkovsky Princeton University

December 06, 2012

PIRSA:12120001

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

Andrea Puhm University of Amsterdam

December 06, 2012

PIRSA:12120029

Quantum Fields and Strings
Curiosity: How Science Became Interested in Everything

Philip Ball The Lancet Group

December 05, 2012

PIRSA:12120004
Local topological order inhibits thermal stability in 2D

December 05, 2012

PIRSA:12120010

Quantum Information

A robust constraint on cosmic textures from the cosmic microwave background

Stephen Feeney

December 11, 2012

PIRSA:12120034

Cosmology

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

Cosmology

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.
Mathematica - Lecture 3b

Pedro Vieira Perimeter Institute for Theoretical Physics

December 10, 2012

PIRSA:12120021

Mathematical physics
Mathematica - Lecture 3a

Pedro Vieira Perimeter Institute for Theoretical Physics

December 10, 2012

PIRSA:12120020

Mathematical physics
Light sleptons, Higgs phenomenology and the vacuum

Stefania Gori University of California, Santa Cruz

December 07, 2012

PIRSA:12120018

Particle 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

Cosmology

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

Quantum Gravity

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.
Quantum one-time programs

Gus Gutowski Institute for Quantum Computing (IQC)

December 06, 2012

PIRSA:12120028

Quantum Information

A "one-time program" for a channel C is a hypothetical cryptographic primitive by which a user may evaluate C on only one input state of her choice. (Think Mission Impossible: "this tape will self-destruct in five seconds.") One-time programs cannot be achieved without extra assumptions such as secure hardware; it is known that one-time programs can be constructed for classical channels using a very basic hypothetical hardware device called a "one-time memory". Our main result is the construction of a one-time program for any quantum channel specified by a circuit, assuming the same basic one-time memory devices used for classical channels. The construction achieves universal composability -- the strongest possible security -- against any quantum adversary. It employs a technique for computation on authenticated quantum data and we present a new authentication scheme called the "trap" scheme for this purpose. Finally, we observe that there is a pathological class of channels that admit trivial one-time programs without any hardware assumptions whatsoever. We characterize these channels, assuming an interesting conjecture on the invertible (or decoherence-free) subspaces of an arbitrary channel. Joint work with Anne Broadbent and Douglas Stebila. http://arxiv.org/abs/1211.1080
Approaches to modeling pulsar magnetospheres

Anatoly Spitkovsky Princeton University

December 06, 2012

PIRSA:12120001

Strong Gravity

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

Quantum Fields and Strings

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.
Curiosity: How Science Became Interested in Everything

Philip Ball The Lancet Group

December 05, 2012

PIRSA:12120004
Local topological order inhibits thermal stability in 2D

December 05, 2012

PIRSA:12120010

Quantum Information

We study the robustness of quantum information stored in the degenerate ground space of a local, frustration-free Hamiltonian with commuting terms on a 2D spin lattice. On one hand, a macroscopic energy barrier separating the distinct ground states under local transformations would protect the information from thermal fluctuations. On the other hand, local topological order would shield the ground space from static perturbations. Here we demonstrate that local topological order implies a constant energy barrier, thus inhibiting thermal stability. Joint work with David Poulin. arXiv:1209.5750

Title	Date	Collection	Type	Info
A robust constraint on cosmic textures from the cosmic microwave background	2012‑12‑11	Cosmology and Gravitation	Scientific Series	View details
Nonlinear Extensions for the Inflationary Power Spectra	2012‑12‑11	Cosmology and Gravitation	Scientific Series	View details
Mathematica - Lecture 3b	2012‑12‑10	12/13 PSI - Front End	Course	View details
Mathematica - Lecture 3a	2012‑12‑10	12/13 PSI - Front End	Course	View details
Light sleptons, Higgs phenomenology and the vacuum	2012‑12‑07	Particle Physics	Scientific Series	View details
CMB as a Probe of New Physics: The Story of Cosmic Birefringence	2012‑12‑06	Cosmology and Gravitation	Scientific Series	View details
Renormalizing TGFTs: a 3d example on SU(2)	2012‑12‑06	Quantum Gravity	Scientific Series	View details
Quantum one-time programs	2012‑12‑06	Quantum Information	Scientific Series	View details
Approaches to modeling pulsar magnetospheres	2012‑12‑06	Strong Gravity	Scientific Series	View details
Unitarity, black hole microstates and how Alices fuzzes but may not even know it	2012‑12‑06	Quantum Fields and Strings	Scientific Series	View details
Curiosity: How Science Became Interested in Everything	2012‑12‑05	Public Lecture Series	Public Lectures	View details
Local topological order inhibits thermal stability in 2D	2012‑12‑05	Quantum Information	Scientific Series	View details

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