Scientific Series

Displaying 3361 - 3372 of 5090

A causal set action

Lisa Glaser University of Vienna
October 31, 2013

PIRSA:13100063
General Relativity & Quantum Cosmology
New lessons about hydrodynamics from gravity

Michal Heller Ghent University
October 31, 2013

PIRSA:13100064
General Relativity & Quantum Cosmology
Aspects of Modified Gravity

Jeremy Sakstein University of Pennsylvania
October 31, 2013

PIRSA:13100132
Astrophysics
Asymptotically Optimal Topological Quantum Compiling

Vadym Kliuchnikov University of Waterloo
October 30, 2013

PIRSA:13100129
Quantum Physics
Gravity and the Search for New Physics with Cosmology

Kris Sigurdson University of British Columbia
October 30, 2013

PIRSA:13100098
High Energy Physics
Silicene - a Wonder Electron Carpet

Baskaran Ganapathy Institute of Mathematical Sciences
October 29, 2013

PIRSA:13100128
Condensed Matter
The Geometry of Supersymmetric Partition Functions

Guido Festuccia Institute for Advanced Study (IAS) - School of Mathematics
October 29, 2013

PIRSA:13100130
High Energy Physics
Minimal Distances and the RG Flow
October 29, 2013

PIRSA:13100069
High Energy Physics
Mapping Mass Across The Sky: CMB Lensing Measurements Past and Future

Blake Sherwin Princeton University
October 29, 2013

PIRSA:13100075
Astrophysics
Asymptotically safe matrix models

Tim Koslowski Technical University of Applied Sciences Würzburg-Schweinfurt
October 24, 2013

PIRSA:13100067
General Relativity & Quantum Cosmology
The Stokes groupoids

Marco Gualtieri University of Toronto

October 23, 2013

PIRSA:13100110
Wilsonian and large N approaches to non-Fermi liquids

Shamit Kachru Stanford University
October 22, 2013

PIRSA:13100109
Condensed Matter

A causal set action

Lisa Glaser University of Vienna
October 31, 2013

PIRSA:13100063
General Relativity & Quantum Cosmology
Causal set theory is discrete, fully covariant theory of quantum gravity. The discrete framework makes it necessary to reformulate continuum concepts. One of these concepts is that of a derivative operator. It is possible to define a derivative operator in causal sets that in the continuum limit agrees with the d'Alembertian for a scalar field. This operator can be used to define a causal set action, which enables Monte-Carlo simulations. In this seminar I will present this operator and action and then show some results of Monte-Carlo simulations in 2 dimensions.
New lessons about hydrodynamics from gravity

Michal Heller Ghent University
October 31, 2013

PIRSA:13100064
General Relativity & Quantum Cosmology
Hydrodynamics of relativistic plasmas received, within the last 10 years, a lot of attention. The reason for it, on one hand, is the quest for theoretical understanding of the quark-gluon plasma created in heavy ion collisions and, on the other, advances in holographic duality and black hole physics in anti-de Sitter spacetimes. I will describe recent progress in answering foundational issues in hydrodynamics of strongly coupled systems, i.e. questions about its applicability and the character of hydrodynamic gradient expansion, that was achieved with the use of numerical techniques in anti-de Sitter spacetimes in the strong gravity regime.
Aspects of Modified Gravity

Jeremy Sakstein University of Pennsylvania
October 31, 2013

PIRSA:13100132
Astrophysics
In this talk I will give an introduction to some of my research into modified gravity over the last three years. I will begin by describing my implementation of chameleon models into supersymmetry and discuss some of the new features and cosmology that arise in this formalism. I will then change direction and talk about my work using astrophysical effects as novel probes of modified gravity theories and present some new results on modified gravity stellar oscillation theory. I will end by discussing work in progress and the possible future constraints that could be placed.
Asymptotically Optimal Topological Quantum Compiling

Vadym Kliuchnikov University of Waterloo
October 30, 2013

PIRSA:13100129
Quantum Physics
In a topological quantum computer, universality is achieved by braiding and quantum information is natively protected from small local errors. We address the problem of compiling single-qubit quantum operations into braid representations for non-abelian quasiparticles described by the Fibonacci anyon model. We develop a probabilistically polynomial algorithm that outputs a braid pattern to approximate a given single-qubit unitary to a desired precision. We also classify the single-qubit unitaries that can be implemented exactly by a Fibonacci anyon braid pattern and present an efficient algorithm to produce their braid patterns. Our techniques produce braid patterns that meet the uniform asymptotic lower bound on the compiled circuit depth and thus are depth-optimal asymptotically. Our compiled circuits are significantly shorter than those output by prior state-of-the-art methods, resulting in improvements in depth by factors ranging from 20 to 1000 for precisions ranging between 10^{−10} and 10^{−30}.
Gravity and the Search for New Physics with Cosmology

Kris Sigurdson University of British Columbia
October 30, 2013

PIRSA:13100098
High Energy Physics
Despite its feeble in strength, gravity plays a pivotal role in shaping our Universe and the things in it. Ever since Newton formulated his universal law of gravitation the recognition that all things gravitate has been nearly sacrosanct. Repeatedly, apparent gravitational anomalies have either foretold the existence of new physics or a misunderstanding of gravity itself, from the existence of nuclear forces to Einstein's general relativity. Eighty years ago gravity betrayed the existence of dark matter, and fifteen years ago gravity demanded dark energy from reluctant cosmologists. I will discuss how gravity enables modern cosmology to explore the echoes of the invisible universe, even if it is impossible or difficult to directly see the invisible universe. In particular, I will show how gravity enables us to put surprisingly severe constraints on the coupling of dark matter to new light particles and search for secret interactions between Fermi's elusive neutrinos. The physics and cosmic history of the invisible universe are writ large across the cosmos itself, and gravity is our tried and trusted messenger.
Silicene - a Wonder Electron Carpet

Baskaran Ganapathy Institute of Mathematical Sciences
October 29, 2013

PIRSA:13100128
Condensed Matter
Graphene is a 2 dimensional net of strongly bonded carbon atoms. This magic carpet has taken us to new heights in the last decade. Silicene and Germanene are analogue nets, made of silicon and germanium atoms respectively, but with a relatively weaker chemical bond. I will argue that these carpets perform some new tricks by not being a carbon copy of graphene. We have suggested [1] that silicene and germanene are Mott insulators and potential abode for room temperature superconductivity, quantum spin liquids and more
The Geometry of Supersymmetric Partition Functions

Guido Festuccia Institute for Advanced Study (IAS) - School of Mathematics
October 29, 2013

PIRSA:13100130
High Energy Physics
Three-dimensional N=2 theories with a U(1)_R symmetry, can be placed on a compact three manifold M preserving some supersymmetry if and only if M admits a transversely holomorphic foliation (THF). I will show that the partition function of the resulting theory is independent of the metric and depends holomorphically on the moduli of the THF. When applied to supersymmetric field theories on manifolds diffeomorphic to S^3 and S^2 x S^1, this result explains many of the properties observed in explicit determinations of their partition functions.
Minimal Distances and the RG Flow
October 29, 2013

PIRSA:13100069
High Energy Physics
We will discuss the renormalization group flow between different classes of CFTs in four dimensions and study possible lower bounds on the "distances" between these theories.
Mapping Mass Across The Sky: CMB Lensing Measurements Past and Future

Blake Sherwin Princeton University
October 29, 2013

PIRSA:13100075
Astrophysics
Measurements of gravitational lensing in the Cosmic Microwave Background (CMB) directly probe the projected distribution of dark matter out to high redshifts. The CMB lensing maps thus encode a wealth of information about both fundamental physics (e.g., dark energy and neutrino properties) and high-redshift astrophysics. I will illustrate this by first reviewing measurements of CMB lensing with the Atacama Cosmology Telescope, discussing both CMB lensing auto-correlations and cross-correlations with quasars, galaxies and optical lensing. I will then discuss ongoing and upcoming measurements of CMB polarization lensing with the POLARBEAR and ACTPol experiments and explain the great scientific potential of such polarization lensing studies in the very near future.
Asymptotically safe matrix models

Tim Koslowski Technical University of Applied Sciences Würzburg-Schweinfurt
October 24, 2013

PIRSA:13100067
General Relativity & Quantum Cosmology
The functional renormalization group is a tool in the systematic search for Euclidean QFTs that works with very little input: All one needs to specify is a field content, symmetries and a notion of locality. The functional renormalization group then allows one to scan this theory space for bare actions for which the path integral can be performed nonperturbatively. These actions appear as fixed points (and relevant deformations) of the renormalization group flow (so-called asymptotic safety). Such a systematic search has so far not been performed for the tensor model approach to quantum gravity. We investigate matrix models for 2-dimensional gravity and the Grosse-Wulkenhaar model, which is a simple tensor model for a 4D noncommutative scalar field theory, as a first step. I will report on work, done in collaboration with Astrid Eichhorn and Alessandro Sfondrini, where we confirmed asymptotic safety purely through functional RG methods. Based on the lessons learned from these models I will summarize how the usual continuum RG approach has to be generalized for the investigation of tensor models and conclude with a recipe for the investigation of general tensor models.
The Stokes groupoids

Marco Gualtieri University of Toronto

October 23, 2013

PIRSA:13100110

Ordinary differential equations become much less ordinary when they are allowed to have singularities. Solving them naively in formal power series, one often obtains divergent series, just as in the perturbation series for physical observables in quantum field theory. The asymptotic interpretation of this divergent series exhibits the famous Stokes phenomenon, an essential ingredient in any full description of the solutions to the system. I will explain a new viewpoint on singular ODE which illuminates the geometric meaning of the phenomena described above, and which can be applied to the problem of resummation of formal power series. This viewpoint uses a very basic but underused tool in differential geometry: Lie groupoids. A Lie groupoid is as natural and essential an object as a Lie group; I shall explain how to build examples of them and how to use them to solve singular differential equations.
Wilsonian and large N approaches to non-Fermi liquids

Shamit Kachru Stanford University
October 22, 2013

PIRSA:13100109
Condensed Matter
We use Wilsonian RG and large N techniques to study the quantum field theory of a critical boson interacting with a Fermi surface, and compare/contrast the results with those coming from holography.

Title	Speaker(s)	Date	Talk Type	Info link
A causal set action	Lisa Glaser	2013-10-31	Scientific Series	View details
New lessons about hydrodynamics from gravity	Michal Heller	2013-10-31	Scientific Series	View details
Aspects of Modified Gravity	Jeremy Sakstein	2013-10-31	Scientific Series	View details
Asymptotically Optimal Topological Quantum Compiling	Vadym Kliuchnikov	2013-10-30	Scientific Series	View details
Gravity and the Search for New Physics with Cosmology	Kris Sigurdson	2013-10-30	Scientific Series	View details
Silicene - a Wonder Electron Carpet	Baskaran Ganapathy	2013-10-29	Scientific Series	View details
The Geometry of Supersymmetric Partition Functions	Guido Festuccia	2013-10-29	Scientific Series	View details
Minimal Distances and the RG Flow		2013-10-29	Scientific Series	View details
Mapping Mass Across The Sky: CMB Lensing Measurements Past and Future	Blake Sherwin	2013-10-29	Scientific Series	View details
Asymptotically safe matrix models	Tim Koslowski	2013-10-24	Scientific Series	View details
The Stokes groupoids	Marco Gualtieri	2013-10-23	Scientific Series	View details
Wilsonian and large N approaches to non-Fermi liquids	Shamit Kachru	2013-10-22	Scientific Series	View details

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Format results

A causal set action

New lessons about hydrodynamics from gravity

Aspects of Modified Gravity

Asymptotically Optimal Topological Quantum Compiling

Gravity and the Search for New Physics with Cosmology

Silicene - a Wonder Electron Carpet

The Geometry of Supersymmetric Partition Functions

Minimal Distances and the RG Flow

Mapping Mass Across The Sky: CMB Lensing Measurements Past and Future

Asymptotically safe matrix models

The Stokes groupoids

Wilsonian and large N approaches to non-Fermi liquids

A causal set action

New lessons about hydrodynamics from gravity

Aspects of Modified Gravity

Asymptotically Optimal Topological Quantum Compiling

Gravity and the Search for New Physics with Cosmology

Silicene - a Wonder Electron Carpet

The Geometry of Supersymmetric Partition Functions

Minimal Distances and the RG Flow

Mapping Mass Across The Sky: CMB Lensing Measurements Past and Future

Asymptotically safe matrix models

The Stokes groupoids

Wilsonian and large N approaches to non-Fermi liquids