Talks

9361 - 9372 of 18375 Results

Spinning Black Holes and the Membrane Paradigm

Robert Penna Massachusetts Institute of Technology (MIT)

October 16, 2014

PIRSA:14100007

General Relativity & Quantum Cosmology
Cosmological Constraints on theories of Modified Gravity

Alexandre Barreira Durham University

October 16, 2014

PIRSA:14100074

Astrophysics
Superconformal Indices, AdS/CFT, and Cyclic Homologies

Richard Eager University of Tokyo

October 16, 2014

PIRSA:14100067

High Energy Physics
14/15 PSI - Statistical Mechanics - Lecture 8

Anton Burkov University of Waterloo

October 16, 2014

PIRSA:14100094
14/15 PSI - Quantum Field Theory I (A) - Lecture 7

Tibra Ali Perimeter Institute for Theoretical Physics

Dan Wohns Perimeter Institute for Theoretical Physics

October 15, 2014

PIRSA:14100036
14/15 PSI - Conformal Field Theory - Lecture 7

Pedro Vieira Perimeter Institute for Theoretical Physics

October 15, 2014

PIRSA:14100017
Quantum Fields and Strings at Finite Coupling

Pedro Vieira Perimeter Institute for Theoretical Physics

October 15, 2014

PIRSA:14100050
14/15 PSI - Statistical Mechanics - Lecture 7

Anton Burkov University of Waterloo

October 15, 2014

PIRSA:14100093
Entanglement Entropy and the Area Law - Lecture 2

Rafael Sorkin Perimeter Institute for Theoretical Physics

October 14, 2014

PIRSA:14100070
Bulk Entanglement Spectrum: From Topological States to Quantum Criticality

Timothy Hsieh Perimeter Institute for Theoretical Physics

October 14, 2014

PIRSA:14100075

Condensed Matter
14/15 PSI - Conformal Field Theory- Lecture 6

Pedro Vieira Perimeter Institute for Theoretical Physics

October 14, 2014

PIRSA:14100016
The Minimal Modal Interpretation of Quantum Theory

David Kagan University of Massachusetts Dartmouth

Jacob Barandes Harvard University

October 14, 2014

PIRSA:14100001

Quantum Physics

Spinning Black Holes and the Membrane Paradigm

Robert Penna Massachusetts Institute of Technology (MIT)

October 16, 2014

PIRSA:14100007

General Relativity & Quantum Cosmology

There are about nine astrophysical black holes with measurements of the black hole's spin via the continuum fitting method. Several of these black holes drive powerful jets, which appear to extract the black hole's rotational energy. I will discuss the theory behind these observations, with a particular focus on the black hole membrane paradigm. The membrane paradigm is useful on a practical level for understanding black hole jets. However, it may also be related to fundamental physics through holography and AdS/CFT. This suggests new opportunities for interactions between fundamental physics and astrophysics.
Cosmological Constraints on theories of Modified Gravity

Alexandre Barreira Durham University

October 16, 2014

PIRSA:14100074

Astrophysics

Recently, research in cosmology has seen a growing interest in theories of gravity beyond General Relativity (GR). From an observational point of view, there are two main reasons for this. Firstly, the law of gravity has never been directly tested on scales larger than the Solar System. Hence, by understanding better the various signatures that different gravity models can leave on cosmological observables, one can improve the chances of identifying any departures from GR, or alternatively, extend the model's observational success into a whole new regime. Secondly, theories of modified gravity can arise also as an alternative to the cosmological constant (or any other form of dark energy) to explain the current accelerated expansion of the Universe. Using my results from suitably modified Boltzmann, N-body codes and semi-analytical models of structure formation, I will describe the way modified gravity models typically impact a series of cosmological observables. I will use two popular models as examples, which are known as Galileon and Nonlocal Gravity. In the Galileon model, the modifications to gravity on large scales are driven by nonlinear derivative interactions of a scalar field, which can nevertheless be suppressed in the Solar System by means of a mechanism known as Vainshtein screening. This model can provide a good fit to the latest CMB, BAO and SNIa data, although with different cosmological parameters than the standard LCDM model. Specifically, unlike LCDM, the Galileon model predicts nonzero neutrino masses (over 5sigma) and the constraints on the Hubble rate are compatible with its local determinations. The results from my N-body simulations and Halo Occupation Distribution analysis also show that the model can describe the measured clustering amplitude of Luminous Red Galaxies and that the screening mechanism can be very efficient in "hiding" the modifications to gravity on small scales. However, these results also show that the observational viability of the model may be under pressure due to the combined constraints derived from the sign of the ISW effect and from Solar System tests. In the Nonlocal model, the acceleration of the universe is driven by terms that involve the inverse of a derivative operator acting on curvature tensors. This model is also likely to pass large-scale structure constraints with the same flying colors as Galileon gravity, but the lack of a screening mechanism in this model makes it unclear on whether or not it is able to satisfy Solar System constraints. These steps I will describe for the cases of the Galileon and Nonlocal models can be viewed as guidelines for one to place constraints on other (or not yet invented) models of modified gravity. References: The results I will describe are based on the following papers: arXiv:1208.0600, arXiv:1302.6241, arXiv:1306.3219, arXiv:1308.3699, arXiv:1401.1497, arXiv:1404.1365, arXiv:1406.0485, arXiv:1408.1084
Superconformal Indices, AdS/CFT, and Cyclic Homologies

Richard Eager University of Tokyo

October 16, 2014

PIRSA:14100067

High Energy Physics

We explain how to obtain the spectrum of operators with protected scaling dimensions in a four-dimensional superconformal field theory from cyclic homology. Additionally, we show that the superconformal index of a quiver gauge theory equals the Euler characteristic of the cyclic homology of the Ginzburg dg algebra associated to the quiver. For quiver gauge theories which are dual to type IIB string theory on the product of an arbitrary smooth Sasaki-Einstein manifold with five-dimensional AdS space, the index is calculated both from the gauge theory and gravity viewpoints. We find complete agreement. Finally we show how to match the spectrum of protected operators on a supergravity compactification involving generalized complex geometry.
14/15 PSI - Statistical Mechanics - Lecture 8

Anton Burkov University of Waterloo

October 16, 2014

PIRSA:14100094
14/15 PSI - Quantum Field Theory I (A) - Lecture 7

Tibra Ali Perimeter Institute for Theoretical Physics

Dan Wohns Perimeter Institute for Theoretical Physics

October 15, 2014

PIRSA:14100036
14/15 PSI - Conformal Field Theory - Lecture 7

Pedro Vieira Perimeter Institute for Theoretical Physics

October 15, 2014

PIRSA:14100017
Quantum Fields and Strings at Finite Coupling

Pedro Vieira Perimeter Institute for Theoretical Physics

October 15, 2014

PIRSA:14100050

Gauge theories lie at the heart of our understanding of three of the four known forces in nature: the electromagnetic, weak and strong forces. Moreover, our best understood non-perturbative definition of a theory of quantum gravity is also given by a gauge theory. Yet, despite their absolutely central role in physics, gauge theories are still far from being tamed with our current theoretical tools. In this colloquium we shall explore the realm of quantum fields and strings at finite coupling and survey some of the exciting recent developments which are improving this state of affairs. The main character in our incursions will be a most symmetric gauge theory known as N=4 super Yang-Mills theory, often referred to as the harmonic oscillator of the twenty first century or, as it was most recently coined, as the Darth Vader theory.
14/15 PSI - Statistical Mechanics - Lecture 7

Anton Burkov University of Waterloo

October 15, 2014

PIRSA:14100093
Entanglement Entropy and the Area Law - Lecture 2

Rafael Sorkin Perimeter Institute for Theoretical Physics

October 14, 2014

PIRSA:14100070
Bulk Entanglement Spectrum: From Topological States to Quantum Criticality

Timothy Hsieh Perimeter Institute for Theoretical Physics

October 14, 2014

PIRSA:14100075

Condensed Matter

A quantum phase transition is usually achieved by tuning physical parameters in a Hamiltonian at zero temperature. Here, we demonstrate that the ground state of a topological phase itself encodes critical properties of its transition to a trivial phase. To extract this information, we introduce a partition of the system into two subsystems both of which extend throughout the bulk in all directions. The resulting bulk entanglement spectrum (BES) has a low-lying part that resembles the excitation spectrum of a bulk Hamiltonian, which allows us to probe a topological phase transition from a single wavefunction by tuning either the geometry of the partition or the entanglement temperature. As an example, this remarkable correspondence between topological phase transition and entanglement criticality is rigorously established for integer quantum Hall states. We also implement BES using tensor networks, derive the universality classes of topological phase transitions from the spin-1 chain Haldane phase, and demonstrate that the AKLT wavefunction (and its generalizations) remarkably contains critical six-vertex (and in general eight-vertex) models within it.
14/15 PSI - Conformal Field Theory- Lecture 6

Pedro Vieira Perimeter Institute for Theoretical Physics

October 14, 2014

PIRSA:14100016
The Minimal Modal Interpretation of Quantum Theory

David Kagan University of Massachusetts Dartmouth

Jacob Barandes Harvard University

October 14, 2014

PIRSA:14100001

Quantum Physics

A persistent mystery of quantum theory is whether it admits an interpretation that is realist, self-consistent, model-independent, and unextravagant in the sense of featuring neither multiple worlds nor pilot waves. In this talk, I will present a new interpretation of quantum theory -- called the minimal modal interpretation (MMI) -- that aims to meet these conditions while also hewing closely to the basic structure of the theory in its widely accepted form. The MMI asserts that quantum systems -- whether closed or open -- have actual states that evolve along kinematical trajectories through their state spaces, and that those trajectories are governed by specific (if approximate) dynamical rules determined by a general new class of conditional probabilities, and in a manner that differs significantly from the de Broglie-Bohm formulation. The MMI is axiomatically parsimonious, leaves the usual dynamical content of quantum theory essentially intact, and includes only metaphysical entities that are either already a standard part of quantum theory or that have counterparts in classical physics. I will also address a number of important issues and implicit assumptions in the foundations community that I believe merit reconsideration and re-evaluation going forward.

Title	Date	Collection	Type	Info
Spinning Black Holes and the Membrane Paradigm	2014‑10‑16	Strong Gravity	Scientific Series	View details
Cosmological Constraints on theories of Modified Gravity	2014‑10‑16	Cosmology and Gravitation	Scientific Series	View details
Superconformal Indices, AdS/CFT, and Cyclic Homologies	2014‑10‑16	Quantum Fields and Strings	Scientific Series	View details
14/15 PSI - Statistical Mechanics - Lecture 8	2014‑10‑16	14/15 PSI - Statistical Mechanics	Course	View details
14/15 PSI - Quantum Field Theory I (A) - Lecture 7	2014‑10‑15	14/15 PSI - Quantum Field Theory	Course	View details
14/15 PSI - Conformal Field Theory - Lecture 7	2014‑10‑15	14/15 PSI - Conformal Field Theory	Course	View details
Quantum Fields and Strings at Finite Coupling	2014‑10‑15	Colloquium	Scientific Series	View details
14/15 PSI - Statistical Mechanics - Lecture 7	2014‑10‑15	14/15 PSI - Statistical Mechanics	Course	View details
Entanglement Entropy and the Area Law - Lecture 2	2014‑10‑14	Entanglement Entropy and the Area Law	Course	View details
Bulk Entanglement Spectrum: From Topological States to Quantum Criticality	2014‑10‑14	Quantum Matter	Scientific Series	View details
14/15 PSI - Conformal Field Theory- Lecture 6	2014‑10‑14	14/15 PSI - Conformal Field Theory	Course	View details
The Minimal Modal Interpretation of Quantum Theory	2014‑10‑14	Quantum Foundations	Scientific Series	View details

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Format results

Spinning Black Holes and the Membrane Paradigm

Cosmological Constraints on theories of Modified Gravity

Superconformal Indices, AdS/CFT, and Cyclic Homologies

14/15 PSI - Statistical Mechanics - Lecture 8

14/15 PSI - Quantum Field Theory I (A) - Lecture 7

14/15 PSI - Conformal Field Theory - Lecture 7

Quantum Fields and Strings at Finite Coupling

14/15 PSI - Statistical Mechanics - Lecture 7

Entanglement Entropy and the Area Law - Lecture 2

Bulk Entanglement Spectrum: From Topological States to Quantum Criticality

14/15 PSI - Conformal Field Theory- Lecture 6

The Minimal Modal Interpretation of Quantum Theory

Spinning Black Holes and the Membrane Paradigm

Cosmological Constraints on theories of Modified Gravity

Superconformal Indices, AdS/CFT, and Cyclic Homologies

14/15 PSI - Statistical Mechanics - Lecture 8

14/15 PSI - Quantum Field Theory I (A) - Lecture 7

14/15 PSI - Conformal Field Theory - Lecture 7

Quantum Fields and Strings at Finite Coupling

14/15 PSI - Statistical Mechanics - Lecture 7

Entanglement Entropy and the Area Law - Lecture 2

Bulk Entanglement Spectrum: From Topological States to Quantum Criticality

14/15 PSI - Conformal Field Theory- Lecture 6

The Minimal Modal Interpretation of Quantum Theory