Scientific Series

Displaying 3601 - 3612 of 5164

Fifth forces and new particles from dark energy

Amol Upadhye University of Wisconsin–Madison
January 08, 2013

PIRSA:13010023
Cosmology
All one-loop amplitudes in N=6 Chern-Simons matter theories

Congkao Wen Queen Mary University of London
December 18, 2012

PIRSA:12120005
Quantum Fields and Strings
Inference of effective quantum models in the asymptotic regime
December 17, 2012

PIRSA:12120042
Quantum Information
Fermionic toric code model and a new class of topological phases in interacting fermion system

Zheng-Cheng Gu Chinese University of Hong Kong
December 14, 2012

PIRSA:12120037
Condensed Matter
Accidental Supersymmetry and the Renormalization of Co-dimension 2 Branes

Matthew Williams PROTO Manufacturing (Canada)
December 14, 2012

PIRSA:12120039
Particle Physics
Black holes: To be or not be, that is the question

Luis Garay Complutense University of Madrid
December 13, 2012

PIRSA:12120032
Quantum Gravity
Application of conditional independence to gapped quantum many-body systems

Isaac Kim University of California, Davis
December 12, 2012

PIRSA:12120035
Quantum Information
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 Foundations
(0,2) Gauge Dynamics and Flux Compactifications

Callum Quigley Kirkland & Ellis
December 11, 2012

PIRSA:12120006
Quantum Fields and Strings
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

Fifth forces and new particles from dark energy

Amol Upadhye University of Wisconsin–Madison
January 08, 2013

PIRSA:13010023
Cosmology
Dark energy coupled to Standard Model fermions and gauge bosons gives rise to fifth forces and new particles, which are readily accessible to experiments from laboratory to cosmological scales. I will discuss chameleon and symmetron models, whose fifth forces are screened locally through large effective masses and symmetry-restoring phase transitions, respectively. Fifth force experiments such as the Eot-Wash torsion balance will test chameleons with small quantum corrections and gravitation-strength fifth forces, as well as symmetrons with coupling energies just beyond the Standard Model scale. A dark energy coupling to electromagnetism would imply that photons passing through a magnetic field will oscillate into particles of dark energy, a phenomenon studied by afterglow experiments such as CHASE. After constraining dark energy using laboratory experiments, I proceed to astrophysical probes. Particles of a photon-coupled dark energy could be produced in the Sun and detected in magnetic helioscopes such as CAST, while fifth forces may alter the dynamics of variable stars and the growth of large-scale structure.
All one-loop amplitudes in N=6 Chern-Simons matter theories

Congkao Wen Queen Mary University of London
December 18, 2012

PIRSA:12120005
Quantum Fields and Strings
In this talk we will present results on all one-loop scattering amplitudes in N=6 Chern-Simons matter theories. Especially we will discuss connection between certain triple-cut diagrams and tree-level recursive diagrams, and a general formula capturing the multi-particle factorization of arbitrary one-loop amplitudes in the theories is obtained from this connection. Furthermore a recursion relation for the supercoefficients of one-loop amplitudes will be derived, which leads the solution for all one-loop amplitudes.
Inference of effective quantum models in the asymptotic regime
December 17, 2012

PIRSA:12120042
Quantum Information
In this talk I will sketch a project which aims at the design of systematic and efficient procedures to infer quantum models from measured data. Progress in experimental control have enabled an increasingly fine tuned probing of the quantum nature of matter, e.g., in superconducting qubits. Such experiments have shown that we not always have a good understanding of how to model the experimentally performed measurements via POVMs. It turns out that the ad hoc postulation of POVMs can lead to inconsistencies. For example, when doing asymptotic state tomography via linear inversion, one sometimes recovers density operators which are significantly not positive semidefinite. Assuming the asymptotic regime, we suggest an alternative procedure where we do not make a priori assumptions on the quantum model, i.e., on the Hilbert space dimension, the prepared states or the measured POVMs. In other words, we simultaneously estimate the dimension of the underlying Hilbert space, the quantum states and the POVMs. We are guided by Occam's razor, i.e., we search for the minimal quantum model consistent with the data.
Fermionic toric code model and a new class of topological phases in interacting fermion system

Zheng-Cheng Gu Chinese University of Hong Kong
December 14, 2012

PIRSA:12120037
Condensed Matter
Accidental Supersymmetry and the Renormalization of Co-dimension 2 Branes

Matthew Williams PROTO Manufacturing (Canada)
December 14, 2012

PIRSA:12120039
Particle Physics
In this talk, I'll give a brief summary of how one-loop bulk eﬀects renormalize both bulk and brane eﬀective interactions for geometries sourced by codimension-two branes. I'll then discuss what these results imply for a six-dimensional supergravity model which aims to capture the features that make extra-dimensional physics attractive for understanding naturalness issues in particle physics. I'll also emphasize the role that brane back-reaction plays in yielding unexpected results, and present a one-loop contribution to the 4D vacuum energy whose size is set by the KK scale.
Black holes: To be or not be, that is the question

Luis Garay Complutense University of Madrid
December 13, 2012

PIRSA:12120032
Quantum Gravity
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.
Application of conditional independence to gapped quantum many-body systems

Isaac Kim University of California, Davis
December 12, 2012

PIRSA:12120035
Quantum Information
It is widely known in the quantum information community that the states that satisfy strong subadditivity of entropy with equality have the form of quantum Markov chain. Based on a recent strengthening of strong subadditivity of entropy, I will describe how such structure can be exploited in the studies of gapped quantum many-body system. In particular, I will describe a diagrammatic trick to i) give a quantitative statement about the locality of entanglement spectrum ii) perturbatively bound changes of topological entanglement entropy under generic perturbation.
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 Foundations
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
Quantum Fields and Strings
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
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.

Title	Speaker(s)	Date	Talk Type	Info link
Fifth forces and new particles from dark energy	Amol Upadhye	2013-01-08	Scientific Series	View details
All one-loop amplitudes in N=6 Chern-Simons matter theories	Congkao Wen	2012-12-18	Scientific Series	View details
Inference of effective quantum models in the asymptotic regime		2012-12-17	Scientific Series	View details
Fermionic toric code model and a new class of topological phases in interacting fermion system	Zheng-Cheng Gu	2012-12-14	Scientific Series	View details
Accidental Supersymmetry and the Renormalization of Co-dimension 2 Branes	Matthew Williams	2012-12-14	Scientific Series	View details
Black holes: To be or not be, that is the question	Luis Garay	2012-12-13	Scientific Series	View details
Application of conditional independence to gapped quantum many-body systems	Isaac Kim	2012-12-12	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

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