Scientific Series

Displaying 3349 - 3360 of 5113

Asymptotically safe matrix models

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

PIRSA:13100067
Quantum Gravity
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
Conformal symmetry and cosmology

Austin Joyce University of Chicago
October 22, 2013

PIRSA:13100070
Cosmology
Heavy particle effective field theory: formalism, dark matter and the proton size puzzle

Richard Hill University of Kentucky
October 18, 2013

PIRSA:13100107
Particle Physics
All AdS7 solutions of type II supergravity

Alessandro Tomasiello University of Milano-Bicocca
October 18, 2013

PIRSA:13100108
Quantum Fields and Strings
Vector Beta Function

Yu Nakayama University of California, Berkeley
October 17, 2013

PIRSA:13100082
Quantum Fields and Strings
Constructing theories from duality: my response to John Wheeler
October 17, 2013

PIRSA:13100072
Quantum Gravity
Quasinormal modes of rapidly rotating black holes/ Stability of tidally perturbed neutron stars

Aaron Zimmerman The University of Texas at Austin
October 17, 2013

PIRSA:13100096
Strong Gravity
Simulating Hamiltonian evolution with quantum computers

Richard Cleve Institute for Quantum Computing (IQC)
October 16, 2013

PIRSA:13100097
Quantum Information
Geometry of quantum phases and emergent Newtonian dynamics

Anatoli Polkovnikov Boston College
October 15, 2013

PIRSA:13100083
Condensed Matter
Can ‘sub-quantum’ theories based on a background field escape Bell’s no-go theorem ?

Louis Vervoort Université de Montréal
October 15, 2013

PIRSA:13100085
Quantum Foundations

Asymptotically safe matrix models

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

PIRSA:13100067
Quantum Gravity
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.
Conformal symmetry and cosmology

Austin Joyce University of Chicago
October 22, 2013

PIRSA:13100070
Cosmology
We will explore the role that conformal symmetries may play in cosmology. First, we will discuss the symmetries underlying the statistics of the primordial perturbations which seeded the temperature anisotropies of the Cosmic Microwave Background. I will show how symmetry considerations lead us to three broad classes of theories to explain these perturbations: single-field inflation, multi-field inflation, and the conformal mechanism. We will discuss the symmetries in each case and derive their model-independent consequences. Finally, we will examine the possibility of violating the null energy condition with a well-behaved quantum field theory.
Heavy particle effective field theory: formalism, dark matter and the proton size puzzle

Richard Hill University of Kentucky
October 18, 2013

PIRSA:13100107
Particle Physics
Heavy particle expansions, familiar from heavy quark physics, have found important applications in the analysis of dark matter candidates and their interactions with the Standard Model. From a different direction, precision spectroscopy of muonic hydrogen has challenged QED and required more precise knowledge of proton structure. These problems have forced a closer examination of the construction of general heavy particle lagrangians at high orders in the 1/M expansion, and in the absence of known ultraviolet completions. Key aspects of this formalism, including the emergence of Lorentz invariance from "nonrelativistic" lagrangians, are reviewed, and several applications are presented. A status report on the proton radius puzzle is given.
All AdS7 solutions of type II supergravity

Alessandro Tomasiello University of Milano-Bicocca
October 18, 2013

PIRSA:13100108
Quantum Fields and Strings
In M-theory, the only AdS7 supersymmetric solutions are AdS7 × S4 and its orbifolds. In this talk, I will describe a classification of AdS7 supersymmetric solutions in type II supergravity. While in IIB none exist, in IIA with Romans mass (which does not lift to M-theory) there are many new ones. The classification starts from a pure spinor approach reminiscent of generalized complex geometry. Without the need for any Ansatz, the method determines uniquely the form of the metric and fluxes, up to solving a system of ODEs. Namely, the metric on M3 is that of an S2 fibered over an interval; this is consistent with the Sp(1) R-symmetry of the holographically dual (1,0) theory. One can obtain numerically many solutions, with D8 and/or D6 brane sources; topologically, the internal manifold M3 = S^3.
Vector Beta Function

Yu Nakayama University of California, Berkeley
October 17, 2013

PIRSA:13100082
Quantum Fields and Strings
We propose various properties of renormalization group beta functions for vector operators in relativistic quantum field theories. We argue that they must satisfy compensated gauge invariance, orthogonality with respect to scalar beta functions, Higgs-like relation among anomalous dimensions and a gradient property. We further conjecture that non-renormalization holds if and only if the vector operator is conserved. The local renormalization group analysis guarantees the first three within power counting renormalization. We verify all the conjectures in conformal perturbation theories and holography in the weakly coupled gravity regime.
Constructing theories from duality: my response to John Wheeler
October 17, 2013

PIRSA:13100072
Quantum Gravity
The late physicist John Wheeler, was renowned for his Socratic method of conducting physics discussions. "Why is general relativity the way it is? What makes it special?" were reportedly questions one should expect in his presence. There are different answers to these questions, each requiring a set of assumptions - which Wheeler would likely question again - and each bringing with it new insights into physics as a whole. This talk will put forward new principles for deriving general relativity. Perhaps more than is the case with other construction principles, the principles introduced are not limited to the derivation of general relativity, requiring only an specification of the theory's phase space in order to be applicable. To be less enigmatic, one defines observable equivalence between physical theories in the Dirac constraint setting, and then the principle merely searches theory space for two equivalent (or dual) fully constrained theories. We find it quite remarkable that such a complex theory as general relativity emerges, when no initial presupposition even on the existence of space-time is made. If there is time (and I will argue there is!) I will discuss another issue that also distinguishes the present set of assumptions: the possibility that they are in a concrete sense ``self-selected", which I like to think would be more satisfactory to Wheeler's line of questioning (or at least give him more to chew on).
Quasinormal modes of rapidly rotating black holes/ Stability of tidally perturbed neutron stars

Aaron Zimmerman The University of Texas at Austin
October 17, 2013

PIRSA:13100096
Strong Gravity
I will review recent work in two very different topics. First, I will discuss the quasinormal mode spectrum of nearly extremal Kerr black holes, where a bifurcation of the frequency spectrum is observed. In addition, collective oscillations of many modes is possible, resulting in a power-law rather than exponentially decaying ringdown. Next, I will discuss a recent proposal for how tidally induced, multimode coupling of normal modes in neutron stars can destabilize the stars. Such an instability could hamper gravitational wave detection of neutron star binaries by matched filtering. By accounting for higher-order multimode couplings, it can be shown that there is no such instability for neutron star binaries, although a milder instability may exist for binaries with less compact objects.
Simulating Hamiltonian evolution with quantum computers

Richard Cleve Institute for Quantum Computing (IQC)
October 16, 2013

PIRSA:13100097
Quantum Information
In 1982, Richard Feynman proposed the concept of a quantum computer as a means of simulating physical systems that evolve according to the Schrödinger equation. I will explain various quantum algorithms that have been proposed for this simulation problem, including my recent work (jointly with Dominic Berry and Rolando Somma) that significantly improves the running time as a function of the precision of the output data.
Geometry of quantum phases and emergent Newtonian dynamics

Anatoli Polkovnikov Boston College
October 15, 2013

PIRSA:13100083
Condensed Matter
In the first part of this talk I will discuss how one can characterize geometry of quantum phases and phase transitions based on the Fubini-Study metric, which characterizes the distance between ground state wave-functions in the external parameter space. This metric is closely related to the Berry curvature. I will show that there are new geometric invariants based on the Euler characteristic. I will also show how one can directly measure this metric tensor in simple dynamical experiments. In the second part of the talk I will discuss emergent nature of macroscopic equations of motion (like Newton's equations) showing that they appear in the leading order of non-adiabatic expansion. I will show that the Berry curvature gives the Coriolis force and the Fubini-Study metric tensor is closely related to the inertia mass. Thus I will argue that any motion (not necessarily motion in space) is geometrical in nature.
Can ‘sub-quantum’ theories based on a background field escape Bell’s no-go theorem ?

Louis Vervoort Université de Montréal
October 15, 2013

PIRSA:13100085
Quantum Foundations
In systems described by Ising-like Hamiltonians, such as spin-lattices, the Bell Inequality can be strongly violated. Surprisingly, these systems are both local and non-superdeterministic. They are local, because 1) they include only local, near-neighbor interaction, 2) they satisfy, accordingly, the Clauser-Horne factorability condition, and 3) they can violate the Bell Inequality also in dynamic Bell experiments. Starting from this result we construct an elementary hidden-variable model, based on a generalized Ising Hamiltonian, describing the interaction of the Bell-particles with a stochastic ‘background’ medium. We suggest that such a model is a simple version of a variety of recently developed ‘sub-quantum’ theories, by authors as Nelson, Adler, De la Pena, Cetto, Groessing, Khrennikov, all based on a background field. We investigate how the model might be turned into a realistic theory. Finally, it appears that background-based models can be tested and discriminated from quantum mechanics by a straightforward extension of existing experiments.

Title	Speaker(s)	Date	Talk Type	Info link
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
Conformal symmetry and cosmology	Austin Joyce	2013-10-22	Scientific Series	View details
Heavy particle effective field theory: formalism, dark matter and the proton size puzzle	Richard Hill	2013-10-18	Scientific Series	View details
All AdS7 solutions of type II supergravity	Alessandro Tomasiello	2013-10-18	Scientific Series	View details
Vector Beta Function	Yu Nakayama	2013-10-17	Scientific Series	View details
Constructing theories from duality: my response to John Wheeler		2013-10-17	Scientific Series	View details
Quasinormal modes of rapidly rotating black holes/ Stability of tidally perturbed neutron stars	Aaron Zimmerman	2013-10-17	Scientific Series	View details
Simulating Hamiltonian evolution with quantum computers	Richard Cleve	2013-10-16	Scientific Series	View details
Geometry of quantum phases and emergent Newtonian dynamics	Anatoli Polkovnikov	2013-10-15	Scientific Series	View details
Can ‘sub-quantum’ theories based on a background field escape Bell’s no-go theorem ?	Louis Vervoort	2013-10-15	Scientific Series	View details

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