Scientific Series

Displaying 3385 - 3396 of 5164

A note on emergent classical behavior and approximations to decoherence functionals

Henrique Gomes University of Oxford
November 05, 2013

PIRSA:13110085
Quantum Foundations
Z2 spin liquid in kagome Heisenberg antiferromagnet

Yuan Wan Chinese Academy of Sciences
November 05, 2013

PIRSA:13110086
Condensed Matter
From the symmetric group to giant gravitons in super Yang-Mills theory
November 05, 2013

PIRSA:13110084
Quantum Fields and Strings
Induced Electroweak Symmetry Breaking and Supersymmetry

Jamison Galloway New York University (NYU)
November 05, 2013

PIRSA:13110050
Particle Physics
Feedback-regulated star formation on galactic and cosmological scales

Claude-André Faucher-Giguère University of California, Berkeley
November 05, 2013

PIRSA:13110056
Cosmology
Split Dirac Supersymmetry and a Higgsino LSP
November 01, 2013

PIRSA:13110052
Particle Physics
A causal set action

Lisa Glaser University of Vienna
October 31, 2013

PIRSA:13100063
Quantum Gravity
New lessons about hydrodynamics from gravity

Michal Heller Ghent University
October 31, 2013

PIRSA:13100064
Strong Gravity
Aspects of Modified Gravity

Jeremy Sakstein University of Pennsylvania
October 31, 2013

PIRSA:13100132
Cosmology
Asymptotically Optimal Topological Quantum Compiling

Vadym Kliuchnikov University of Waterloo
October 30, 2013

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

Kris Sigurdson University of British Columbia
October 30, 2013

PIRSA:13100098
Particle Physics
Silicene - a Wonder Electron Carpet

Baskaran Ganapathy Institute of Mathematical Sciences
October 29, 2013

PIRSA:13100128
Condensed Matter

A note on emergent classical behavior and approximations to decoherence functionals

Henrique Gomes University of Oxford
November 05, 2013

PIRSA:13110085
Quantum Foundations
Although it can only be argued to have become consequential in the study of quantum cosmology, the question ``Why do we observe a classical world? " has been one of the biggest preoccupations of quantum foundations. In the consistent histories formalism, the question is shifted to an analysis of the telltale sign of quantum mechanics: superposition of states. In the consistent histories formalism, histories of the system which ``decohere", i.e. fall out of superposition or have negligible interference can be subjected to a notion of classical probability. In this paper we use an extension of Kirchoff's diffraction formula for wave functions on configuration spaces to give a different analysis and an approximation of decoherence. The Kirchoff diffraction formula lies conveniently at the midway between path integrals, wave equations, and classical behavior. By using it, we formulate an approximate dampening of the amplitude of superposition of histories. The dampening acts on each middle element of the fine-grained history {c_\alpha}, and is a function of the angle formed between {c_{n-1},c_n} and {c_n,c_{n+1}}, as classical trajectories in configuration space. As an example we apply the formalism to a modified gravity theory in the ADM gravitational conformal superspace.
Z2 spin liquid in kagome Heisenberg antiferromagnet

Yuan Wan Chinese Academy of Sciences
November 05, 2013

PIRSA:13110086
Condensed Matter
A quantum spin liquid is a hypothesized ground state of a magnet without long-range magnetic order. Similar to a liquid, which is spatially uniform and strongly correlated, a quantum spin liquid preserves all the symmetries and exhibits strong correlations between spins. First proposed by P. W. Anderson in 1973, it has remained a conjecture until recently. In the past couple of years, numerical studies have provided strong evidences for quantum spin liquid in a simple model, the kagome Heisenberg antiferromagnet. In this talk, I will describe a low-energy effective theory for this magnet in terms of a lattice gauge theory with the simplest possible mathematical structure (a group of two elements, namely Z2). I will show that the theory reproduces many characteristic features observed numerically, thereby providing a bridge between the numeircs and the analytics. Furthermore, I will present theoretical predictions which could be tested in future numerical studies.
From the symmetric group to giant gravitons in super Yang-Mills theory
November 05, 2013

PIRSA:13110084
Quantum Fields and Strings
In this talk we will discuss how giant gravitons and their open string interactions emerge from super Yang-Mills Theory. This is accomplished by diagonalizing the one loop dilatation operator on a class of operators with bare dimension of order N. From the result of this diagonalization, the Gauss Law governing the allowed open string excitations of giant gravitons is clearly visible. In addition, we show that this sector of the theory is integrable.
Induced Electroweak Symmetry Breaking and Supersymmetry

Jamison Galloway New York University (NYU)
November 05, 2013

PIRSA:13110050
Particle Physics
I'll discuss a class of supersymmetric models in which the physical Higgs mass is freed from the quartic coupling, thereby allowing for a 125 GeV Higgs state whose self-interaction can be much smaller than in the SM via a mechanism of 'induced EWSB'. This class of models provides a unique alternative to other realizations of natural SUSY, and the simplest realizations necessitate additional characteristic scalars below the TeV scale, thus altering phenomenological predictions for additional Higgses at the LHC.
Feedback-regulated star formation on galactic and cosmological scales

Claude-André Faucher-Giguère University of California, Berkeley
November 05, 2013

PIRSA:13110056
Cosmology
A central problem in galaxy formation is to understand why star formation is so inefficient. Within individual galaxies, gas is converted into stars at a rate two orders of magnitude slower than unimpeded gravitational collapse predicts, a fact embodied in the low normalization of the observed Kennicutt-Schmidt (K-S) relationship between star formation rate surface density and gas surface density. Star formation in galaxies is also globally inefficient in the sense that the stellar mass in dark matter halos is a small fraction of the universal baryon fraction. I will show that these two facts can be explained by the self-regulation of star formation by feedback from massive stars. Within galaxies, stellar feedback drives turbulence that supports the interstellar medium against collapse and the K-S law is set by the low strength of gravity relative to stellar feedback. The energy input from the same stellar feedback processes drive powerful galactic outflows that remove most of the gas accreted from the intergalactic medium before it has time to turn into stars. Using cosmological hydrodynamical simulations from our FIRE project ("Feedback In Realistic Environments"), I will show that gas removal by star formation-driven galactic winds successfully explains the observed galaxy stellar mass function, at least for galaxies less massive than the Milky Way. Feedback from massive black holes may be required to explain the quenching of more massive galaxies. Motivated by recent observations, I will discuss the physics of galactic winds driven by active galactic nuclei.
Split Dirac Supersymmetry and a Higgsino LSP
November 01, 2013

PIRSA:13110052
Particle Physics
TBA
A causal set action

Lisa Glaser University of Vienna
October 31, 2013

PIRSA:13100063
Quantum Gravity
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
Strong Gravity
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
Cosmology
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 Information
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
Particle 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

Title	Speaker(s)	Date	Talk Type	Info link
A note on emergent classical behavior and approximations to decoherence functionals	Henrique Gomes	2013-11-05	Scientific Series	View details
Z2 spin liquid in kagome Heisenberg antiferromagnet	Yuan Wan	2013-11-05	Scientific Series	View details
From the symmetric group to giant gravitons in super Yang-Mills theory		2013-11-05	Scientific Series	View details
Induced Electroweak Symmetry Breaking and Supersymmetry	Jamison Galloway	2013-11-05	Scientific Series	View details
Feedback-regulated star formation on galactic and cosmological scales	Claude-André Faucher-Giguère	2013-11-05	Scientific Series	View details
Split Dirac Supersymmetry and a Higgsino LSP		2013-11-01	Scientific Series	View details
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

Scientific Series

Format results