Scientific Series

Displaying 3109 - 3120 of 5085

Conformal field theories at non-zero temperature: operator product expansions, Monte Carlo, and holography
September 19, 2014

PIRSA:14090072
High Energy Physics

Condensed Matter

General Relativity & Quantum Cosmology
Observables and Change in Totally Constrained Systems

Karim Thebault Ludwig-Maximilians-Universität München (LMU)
September 18, 2014

PIRSA:14090004
General Relativity & Quantum Cosmology
Evolution of quantum field, particle content, and classicality in the three stage universe

Suprit Singh IUCAA - The Inter-University Centre for Astronomy and Astrophysics
September 18, 2014

PIRSA:14090082
Astrophysics
A magic bullet for numerous quantum-informational tasks

Mark Howard University of Waterloo

September 17, 2014

PIRSA:14090006
Boltzmann's Dog and Darwin's Finch: The statistical thermodynamics of self-replication and evolution

Jeremy England Massachusetts Institute of Technology (MIT)

September 17, 2014

PIRSA:14090003
Irreversibility, Entropy Production, and and Self-organization far from Equilibrium

Jeremy England Massachusetts Institute of Technology (MIT)
September 17, 2014

PIRSA:14090073
Condensed Matter
Self-assembling tensor networks and holography in disordered spin chains

Andrew Goldsborough RWTH Aachen University
September 16, 2014

PIRSA:14090029
Condensed Matter
Infinite Chiral Symmetry in Four Dimensions

Wolfger Peelaers University of Oxford

September 16, 2014

PIRSA:14090079
Scalar Simplified Models and Dark Matter at Colliders

Matthew Buckley Rutgers University
September 16, 2014

PIRSA:14090080
High Energy Physics
Cosmic flows: testing gravity and the matter power spectrum on very large scales

Mike Hudson University of Waterloo
September 16, 2014

PIRSA:14090077
Astrophysics
Maximal supergravity, holography and the Romans mass

Oscar Varela Harvard University
September 12, 2014

PIRSA:14090071
High Energy Physics
Stripes and pairing in t-J and Hubbard models

Steven White University of California, Irvine
September 11, 2014

PIRSA:14090074
Condensed Matter

Conformal field theories at non-zero temperature: operator product expansions, Monte Carlo, and holography
September 19, 2014

PIRSA:14090072
High Energy Physics

Condensed Matter

General Relativity & Quantum Cosmology
We discuss properties of 2-point functions in CFTs in 2+1D at finite temperature. For concreteness, we focus on those involving conserved flavour currents, in particular on the associated conductivity. At frequencies much greater than the temperature, ω >> T, the ω dependence of the conductivity can be computed from the operator product expansion (OPE) between the currents and operators which acquire a non-zero expectation value at T > 0. Such results are found to be in excellent agreement with quantum Monte Carlo studies of the O(2) Wilson-Fisher CFT. Results for the conductivity and other observables are also obtained in vector 1/N expansions. We match these large ω results to the corresponding correlators of holographic representations of the CFT: the holographic approach then allows us to extrapolate to small ω/T. Other holographic studies implicitly only used the OPE between the currents and the energy-momentum tensor, and this yields the correct leading large ω behavior for a large class of CFTs. However, for the Wilson-Fisher CFT a relevant “thermal” operator must also be considered, and then consistency with the Monte Carlo results is obtained without a previously needed ad hoc rescaling of the T value [1]. We also use the OPE to prove sum rules obeyed by the conductivity. **In collaboration with A. Katz, S. Sachdev and E. Sørensen** [1] WWK, E. Sørensen, S. Sachdev, Nat. Phys. 10, 361 (2014)
Observables and Change in Totally Constrained Systems

Karim Thebault Ludwig-Maximilians-Universität München (LMU)
September 18, 2014

PIRSA:14090004
General Relativity & Quantum Cosmology
We isolate an important physical distinction between gauge symmetries which exist at the level of histories and states, and those which exist at the level of histories and not states. This distinction is characterised explicitly using a generalized Hamilton-Jacobi formalism within which a non-standard prescription for the observables of classical totally constrained systems is developed. These ideas motivate a `relational quantization' procedure which is different from the standard `Dirac quanization'. In particular, relational quantization of totally constrained systems leads to a formalism with superpositions of energy eigenstates and an enlarged set of quantum observables. These `Kucha\v{r} observables' can change independently of each other, and thus are associated with measurable quantities in excess of the `perennials' of the standard Dirac approach.
Evolution of quantum field, particle content, and classicality in the three stage universe

Suprit Singh IUCAA - The Inter-University Centre for Astronomy and Astrophysics
September 18, 2014

PIRSA:14090082
Astrophysics
I will discuss the evolution of a quantum scalar field in a toy universe which has three stages of evolution, viz., (i) an early (inflationary) de Sitter phase (ii) radiation-dominated phase and (iii) late-time (cosmological constant dominated) de Sitter phase. Using the Schr\"odinger picture, the scalar field equations are solved separately for the three stages and matched at the transition points. The boundary conditions are chosen so that field modes in the early de Sitter phase evolve from the Bunch-Davies vacuum state. I shall look the (time-dependent) particle content of this quantum state for the entire evolution of the universe and describe the various features both numerically and analytically. I shall also describe the quantum to classical transition in terms of a classicality parameter which tracks the particle creation and its effect on phase space correlation of the quantum field.
A magic bullet for numerous quantum-informational tasks

Mark Howard University of Waterloo

September 17, 2014

PIRSA:14090006

A class of d-level quantum states called "magic states", whose initial purpose was to enable universal fault-tolerant computation within error-correcting codes, has a surprisingly broad range of applications. We begin by describing their structure with respect to the Clifford hierarchy, and in terms of convex geometry before proceeding to their applications. They appear to have some relevance to the search for SIC-POVMs in certain prime dimensions. A version of the CHSH non-local game, using a d-ary alphabet and Pauli measurements, has an optimal quantum strategy using magic states. Finally, magic states exhibit nice symmetries (balanced, minimum uncertainty) with respect to Pauli measurements and consequently could find applications in areas like cryptography.
Boltzmann's Dog and Darwin's Finch: The statistical thermodynamics of self-replication and evolution

Jeremy England Massachusetts Institute of Technology (MIT)

September 17, 2014

PIRSA:14090003

Living things operate according to well-known physical laws, yet it is challenging to discern specific, non-trivial consequences of these constraints for how an organism that is a product of evolution must behave. Part of the difficulty here is that life lives very far from thermal equilibrium, where many of our traditional theoretical tools fail us. However, recent developments in nonequilibrium statistical mechanics may help light a way forward. The goal of this talk will be to explain some of these developments, and show how they begin to offer a new perspective on the physics of self-replication, natural selection, and evolution.
Irreversibility, Entropy Production, and and Self-organization far from Equilibrium

Jeremy England Massachusetts Institute of Technology (MIT)
September 17, 2014

PIRSA:14090073
Condensed Matter
In the last few decades, substantial advances have been made in our ability to make general statements about the thermodynamics of systems driven far from thermal equilibrium. In this talk, I will give a brief overview of some the most basic results in this area and explain their connection to classic results in linear response theory. I will then describe how to formally construct the generalization of free energy for macrostates in a far-from-equilibrium system and discuss possible connections to self-organization phenomena in both biological and other contexts.
Self-assembling tensor networks and holography in disordered spin chains

Andrew Goldsborough RWTH Aachen University
September 16, 2014

PIRSA:14090029
Condensed Matter
We show that the numerical strong disorder renormalization group algorithm (SDRG) of Hikihara et.\ al.\ [{Phys. Rev. B} {\bf 60}, 12116 (1999)] for the one-dimensional disordered Heisenberg model naturally describes a tree tensor network (TTN) with an irregular structure defined by the strength of the couplings. Employing the holographic interpretation of the TTN in Hilbert space, we compute expectation values, correlation functions and the entanglement entropy using the geometrical properties of the TTN. We find that the disorder averaged spin-spin correlation scales with the average path length through the tensor network while the entanglement entropy scales with the minimal surface connecting two regions. Furthermore, the entanglement entropy increases with both disorder and system size, resulting in an area-law violation. Our results demonstrate the usefulness of a self-assembling TTN approach to disordered systems and quantitatively validate the connection between holography and quantum many-body systems.
Infinite Chiral Symmetry in Four Dimensions

Wolfger Peelaers University of Oxford

September 16, 2014

PIRSA:14090079

We describe a new correspondence between four-dimensional conformal field theories with extended supersymmetry and two-dimensional chiral algebras. We explore the resulting chiral algebras in the context of theories of class S. The class S duality web implies nontrivial associativity properties for the corresponding chiral algebras, the structure of which can be summarized by a generalized topological quantum field theory.
Scalar Simplified Models and Dark Matter at Colliders

Matthew Buckley Rutgers University
September 16, 2014

PIRSA:14090080
High Energy Physics
Dark matter is clear evidence of the existence of new physics beyond the Standard Model, and there are compelling reasons to expect that this physics can be probed at the LHC. As we prepare for Run II, we must consider a wide range of possible phenomenology, leaving no stone unturned. In this talk, I present a set of scalar and pseudoscalar models which provide a useful framework to interpret dark matter results, and can motivate new searches in novel channels at the LHC.
Cosmic flows: testing gravity and the matter power spectrum on very large scales

Mike Hudson University of Waterloo
September 16, 2014

PIRSA:14090077
Astrophysics
Peculiar velocities - deviations from Hubble expansion - are the only practical probe of the growth of matter density fluctuations on very large scales in the nearby Universe. I will discuss recent measurements of quantities of cosmological interest from our group and others. One is the "bulk" flow of nearby galaxies with respect to the frame defined by the Cosmic Microwave Background, and what this tells us about fluctuations on large very spatial scales. The second is the measurement of the growth rate of fluctuations, a critical test of Lambda CDM and modified gravity models.
Maximal supergravity, holography and the Romans mass

Oscar Varela Harvard University
September 12, 2014

PIRSA:14090071
High Energy Physics
At large N, an important sector of the ABJM field theory defined on a stack of N M2-branes can be described holographically by the D=4 N=8 SO(8)-gauged supergravity of de Wit and Nicolai. Since its inception, the latter has been tacitly assumed to be unique. Recently, however, a one-parameter family of SO(8) gaugings of N=8 supergravity has been discovered, the de Wit-Nicolai theory being just a member in this class. I will explain how this overlooked family of SO(8)-gauged supergravities is deeply related to electric/magnetic duality breaking in four dimensions. I will then discuss some predictions that can be made about the family of dual large-N field theories that these supergravities define, focusing on the structure of superconformal phases and the RG flows between them. I will finally argue that when the gauging is chosen to be related, but different, to the SO(8) one, the D=4 N=8 family arises as consistent truncation of massive IIA on the six-sphere, with the Romans mass identified as the electric/magnetic duality-breaking parameter.
Stripes and pairing in t-J and Hubbard models

Steven White University of California, Irvine
September 11, 2014

PIRSA:14090074
Condensed Matter
This has been a leading question in condensed matter physics since the discovery of the cuprate superconductors. In this talk I will review some of the DMRG and tensor network results for the ground states of these models. A key question I'll address is the issue of stripes: are the ground states striped? Do stripes compete with or induce d-wave superconductivity? Another question I'll address is: how well does 2D DMRG do in comparison with iPEPS and quantum Monte Carlo. I will also show recent results for a standard 3-band Hubbard model for the cuprates. The asymmetry between hole and electron doped systems which is seen in the cuprates arises naturally from this model.

Title	Speaker(s)	Date	Talk Type	Info link
Conformal field theories at non-zero temperature: operator product expansions, Monte Carlo, and holography		2014-09-19	Scientific Series	View details
Observables and Change in Totally Constrained Systems	Karim Thebault	2014-09-18	Scientific Series	View details
Evolution of quantum field, particle content, and classicality in the three stage universe	Suprit Singh	2014-09-18	Scientific Series	View details
A magic bullet for numerous quantum-informational tasks	Mark Howard	2014-09-17	Scientific Series	View details
Boltzmann's Dog and Darwin's Finch: The statistical thermodynamics of self-replication and evolution	Jeremy England	2014-09-17	Scientific Series	View details
Irreversibility, Entropy Production, and and Self-organization far from Equilibrium	Jeremy England	2014-09-17	Scientific Series	View details
Self-assembling tensor networks and holography in disordered spin chains	Andrew Goldsborough	2014-09-16	Scientific Series	View details
Infinite Chiral Symmetry in Four Dimensions	Wolfger Peelaers	2014-09-16	Scientific Series	View details
Scalar Simplified Models and Dark Matter at Colliders	Matthew Buckley	2014-09-16	Scientific Series	View details
Cosmic flows: testing gravity and the matter power spectrum on very large scales	Mike Hudson	2014-09-16	Scientific Series	View details
Maximal supergravity, holography and the Romans mass	Oscar Varela	2014-09-12	Scientific Series	View details
Stripes and pairing in t-J and Hubbard models	Steven White	2014-09-11	Scientific Series	View details

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Conformal field theories at non-zero temperature: operator product expansions, Monte Carlo, and holography

Observables and Change in Totally Constrained Systems

Evolution of quantum field, particle content, and classicality in the three stage universe

A magic bullet for numerous quantum-informational tasks

Boltzmann's Dog and Darwin's Finch: The statistical thermodynamics of self-replication and evolution

Irreversibility, Entropy Production, and and Self-organization far from Equilibrium

Self-assembling tensor networks and holography in disordered spin chains

Infinite Chiral Symmetry in Four Dimensions

Scalar Simplified Models and Dark Matter at Colliders

Cosmic flows: testing gravity and the matter power spectrum on very large scales

Maximal supergravity, holography and the Romans mass

Stripes and pairing in t-J and Hubbard models

Conformal field theories at non-zero temperature: operator product expansions, Monte Carlo, and holography

Observables and Change in Totally Constrained Systems

Evolution of quantum field, particle content, and classicality in the three stage universe

A magic bullet for numerous quantum-informational tasks

Boltzmann's Dog and Darwin's Finch: The statistical thermodynamics of self-replication and evolution

Irreversibility, Entropy Production, and and Self-organization far from Equilibrium

Self-assembling tensor networks and holography in disordered spin chains

Infinite Chiral Symmetry in Four Dimensions

Scalar Simplified Models and Dark Matter at Colliders

Cosmic flows: testing gravity and the matter power spectrum on very large scales

Maximal supergravity, holography and the Romans mass

Stripes and pairing in t-J and Hubbard models