Scientific Series

Displaying 3361 - 3372 of 4903

Multifield Reheating and the Fate of the Primordial Observables

Ewan Tarrant University of Nottingham
February 05, 2013

PIRSA:13020123
Astrophysics
A classification of symmetry enriched topological phases with exactly solvable models

Ying Ran Boston College
February 01, 2013

PIRSA:13020122
Condensed Matter
Searching for topological phases in transition metal oxide heterostructures

Ying Ran Boston College
January 31, 2013

PIRSA:13010113
Condensed Matter
Hidden Structure in Linguistics: The Organization of Sound Systems

Elan Dresher

January 30, 2013

PIRSA:13010017
How to Fall into a Black Hole

Herman Verlinde Princeton University
January 29, 2013

PIRSA:13010020
High Energy Physics
Cosmic Tides

Ue-Li Pen Canadian Institute for Theoretical Astrophysics (CITA)
January 29, 2013

PIRSA:13010114
Astrophysics
What is motion? What is time?

Flavio Mercati University of Naples Federico II
January 23, 2013

PIRSA:13010003
General Relativity & Quantum Cosmology
Superfluid to normal phase transition in strongly interacting bosons in two and three dimensions.

Juan Carrasquilla ETH Zurich
January 22, 2013

PIRSA:13010107
Condensed Matter
A monodromy defect in the 3d Ising model.

Roberto Pellegrini National Institute for Nuclear Physics
January 22, 2013

PIRSA:13010106
High Energy Physics
Holographic description of cosmological singularity

Misha Smolkin Hebrew University of Jerusalem
January 22, 2013

PIRSA:13010111
Astrophysics
Pinning of Fermionic Occupation Numbers

Christian Schilling ETH Zurich - Institut für Theoretische Physik
January 21, 2013

PIRSA:13010105
Quantum Physics
Indirect Searches for Dark Matter with the Fermi Large Area Telescope

Andrea Marie Albert Ohio State University
January 18, 2013

PIRSA:13010102
High Energy Physics

Multifield Reheating and the Fate of the Primordial Observables

Ewan Tarrant University of Nottingham
February 05, 2013

PIRSA:13020123
Astrophysics
The presence of additional light fields during inflation can source isocurvature fluctuations, which can cause the curvature perturbation $\zeta$, and its statistics to evolve on superhorizon scales. I will demonstrate that if these fluctuations have not completely decayed before the onset of perturbative reheating, then primordial observables such as the level of non--Gaussianity can develop substantial reheating dependant corrections. I will argue that for inflationary models where an adiabatic condition is not reached before the relevant fields begin to decay, we must be careful in our interpretation of any observational constraints that place bounds on the statistics of $\zeta$.
A classification of symmetry enriched topological phases with exactly solvable models

Ying Ran Boston College
February 01, 2013

PIRSA:13020122
Condensed Matter
Two types of topological phases have attracted a lot of attention in condensed matter physics: symmetry protected topological(SPT) phases and topologically ordered phases. On the one hand, SPT phases are protected by given global symmetries while there is no topological order in the bulk. On the other hand, topologically ordered phases do not require symmetry and feature topological ground state degeneracy. In this talk, I present a classification of phases with both topological orders and global symmetries, equipped with local bosonic exactly solvable models. This classification, in some sense, organizes previous pieces of understandings on SPT phases, topological orders, symmetry fractionalizations, into a single framework. Solution of the exactly solvable models and measurable consequences will be discussed.
Searching for topological phases in transition metal oxide heterostructures

Ying Ran Boston College
January 31, 2013

PIRSA:13010113
Condensed Matter
In this talk I will present our recent investigations on possible topological phases in (111) heterostructures of transition metal oxide. These (111) heterstructures are promising systems to realize many 2D topological phases at high temperatures, even with strong correlations, which is hard to be achieved in conventional materials. Several examples will be discussed, including high-temperature quantum spin hall effect in LaAlO3/LaAuO3/LaAlO3 bilayer, correlation induced topological phases in LaAlO3/LaNiO3/LaAlO3 multilayer, nearly flat topological band with C=2 (C: Chern number) in SrIrO3 trilayer, and abelian/nonabelian fractional quantum hall effects in the absence of Landau levels (fractional Chern insulators). If time is allowed, I will also briefly introduce our work on classifying wavefunctions of fractional Chern/topological insulators.
Hidden Structure in Linguistics: The Organization of Sound Systems

Elan Dresher

January 30, 2013

PIRSA:13010017

I will discuss some basic notions in the theory of phonology (sound systems in language). The sounds of a language are generally assumed to be composed of smaller constituents, called features. The features that make up a sound cannot be directly obtained from its pronunciation, but rather must be inferred from the system of contrasts that are at play in a particular language. How to determine which features are contrastive presents a logical and empirical puzzle that may be interesting to students of physics, who are accustomed to explaining observable events in terms of hidden structures that cannot be directly observed.
How to Fall into a Black Hole

Herman Verlinde Princeton University
January 29, 2013

PIRSA:13010020
High Energy Physics
In this talk I investigate the "firewall argument", that claims that black hole horizons can not be smooth. Using a holographic model of the black hole horizon as a quantum mechanical membrane, I show how to recover the black hole interior as an emergent smooth region of space-time. The reconstruction makes use of the formalism of quantum error correcting codes. I explain why the horizon of very old black holes appears to be singular, and formulate a complementarity principle that resolves this firewall paradox.
Cosmic Tides

Ue-Li Pen Canadian Institute for Theoretical Astrophysics (CITA)
January 29, 2013

PIRSA:13010114
Astrophysics
We apply CMB lensing techniques to large scale structure and solve for the 3-D cosmic tidal field. We use small scale filamentary structures to solve for the large scale tidal shear and gravitational potential. By comparing this to the redshift space density field, one can measure the gravitational growth factor on large scales without cosmic variance. This potentially enables accurate measurements of neutrino masses and reconstruction of radial modes lost in 21 cm intensity mapping, which are essential for CMB and other cross correlations. We relate the tidal fields to the squeezed limit bispectrum, and present initial results from simulations and data from the SDSS.
What is motion? What is time?

Flavio Mercati University of Naples Federico II
January 23, 2013

PIRSA:13010003
General Relativity & Quantum Cosmology
I give an account of the Machian approach to dynamics, from Mach's critique of Newton to the work of Barbour, Bertotti, York and O'Murchadha, which culminated in the theory of Shape Dynamics, a new and original way of thinking about General Relativity. I conclude commenting on the present research lines in Shape Dynamics, and the opportunity it offers to solve the problem of time in quantum gravity.

Support for this colloquium is provided by The Templeton Frontiers Program.
Superfluid to normal phase transition in strongly interacting bosons in two and three dimensions.

Juan Carrasquilla ETH Zurich
January 22, 2013

PIRSA:13010107
Condensed Matter
Using quantum Monte Carlo simulations, we investigate the finite-temperature phase diagram of hard-core bosons (XY model) in two- and three-dimensional square lattices. To determine the phase boundaries, we perform a finite-size scaling analysis of the condensate fraction and/or the superfluid stiffness. We then discuss how this diagrams can be measured in experiments with trapped ultracold gases, where the systems are inhomogeneous. For that, we introduce a method based on the measurement of the zero-momentum occupation, which is adequate for experiments dealing with both homogeneous and trapped systems. Finally, we provide an analytical argument that demonstrates that the Bose-Hubbard model does not exhibit ﬁnite-temperature BEC in two dimensions, provided that density remains finite across the entire system in the thermodynamic limit.
A monodromy defect in the 3d Ising model.

Roberto Pellegrini National Institute for Nuclear Physics
January 22, 2013

PIRSA:13010106
High Energy Physics
A conformal defect is a d-dimensional geometrical object that breaks the SO(D+1,1) symmetry, of a D-dimensional conformal field theory, down to those transformations that leave the defect invariant i.e. SO(D-d) X SO(d+1,1).
We studied the 3D critical Ising model in presence of a special kind of these defects, a monodromy line defect.
In particular we computed, using Montecarlo simulations, the anomalous dimensions of the lowest dimensional operators living at the defect, as well as correlation functions of operators in the bulk with operators at the defect.
We found a good agreement between our results and the expectations of conformal field theory.
Holographic description of cosmological singularity

Misha Smolkin Hebrew University of Jerusalem
January 22, 2013

PIRSA:13010111
Astrophysics
In my talk I will discuss our recent paper hep-th/1211.1322 where we construct a 3D conformal field theory dual to asymptotically AdS cosmology in four dimensions. Due to the scale invariance this dual theory allows an infinite family of instantons each of which breaks the conformal group O(3,2) down to O(3,1). These instantons are dual to bulk instantons responsible for nucleating an O(3,1) invariant cosmological bubble. Presumably they indicate an infinite instability rate, however we are able to sum over all of them completely. The resulting theory is manifestly stable, unitary and finite.
Pinning of Fermionic Occupation Numbers

Christian Schilling ETH Zurich - Institut für Theoretische Physik
January 21, 2013

PIRSA:13010105
Quantum Physics
The problem of determining and describing the family of 1-particle reduced density operators (1-RDO) arising from N-fermion pure states (viapartial trace) is known as the fermionic quantum marginal problem. We present its solution, a multitude of constraints on the eigenvalues of the 1-RDO, generalizing the Pauli exclusion principle. To explore the relevance of these constraints we study an analytically solvable model of N fermions in a harmonic potential and determine the spectral `trajectory' corresponding to the ground state as function of the fermion-fermion interaction strength.Intriguingly, we find that the occupation numbers are almost, but not exactly, pinned to the boundary of the allowed region (quasi-pinned). Our findings suggest a generalization of the Hartree-Fock approximation.

see also: http://arxiv.org/abs/1210.5531
Indirect Searches for Dark Matter with the Fermi Large Area Telescope

Andrea Marie Albert Ohio State University
January 18, 2013

PIRSA:13010102
High Energy Physics
There is overwhelming evidence that non-baryonic dark matter constitutes ~23% of the energy density of the universe. Weakly Interacting Massive Particles (WIMPs) are promising dark matter candidates that may produce gamma rays via annihilation or decay detectable by the Fermi Large Area Telescope (Fermi LAT). A detection of WIMPs would also indicate the existence of physics beyond the Standard Model. I will present recent results from indirect WIMP searches by the Fermi LAT Collaboration. I will focus on our recent search for gamma-ray spectral lines from WIMP annihilations with 4 years of data. There has been recent excitement with the report of a line-like feature localized in the galactic center around 130 GeV. I will be discussing what our search finds and the systematic checks we've performed on potential signals.

Title	Speaker(s)	Date	Talk Type	Info link
Multifield Reheating and the Fate of the Primordial Observables	Ewan Tarrant	2013-02-05	Scientific Series	View details
A classification of symmetry enriched topological phases with exactly solvable models	Ying Ran	2013-02-01	Scientific Series	View details
Searching for topological phases in transition metal oxide heterostructures	Ying Ran	2013-01-31	Scientific Series	View details
Hidden Structure in Linguistics: The Organization of Sound Systems	Elan Dresher	2013-01-30	Scientific Series	View details
How to Fall into a Black Hole	Herman Verlinde	2013-01-29	Scientific Series	View details
Cosmic Tides	Ue-Li Pen	2013-01-29	Scientific Series	View details
What is motion? What is time?	Flavio Mercati	2013-01-23	Scientific Series	View details
Superfluid to normal phase transition in strongly interacting bosons in two and three dimensions.	Juan Carrasquilla	2013-01-22	Scientific Series	View details
A monodromy defect in the 3d Ising model.	Roberto Pellegrini	2013-01-22	Scientific Series	View details
Holographic description of cosmological singularity	Misha Smolkin	2013-01-22	Scientific Series	View details
Pinning of Fermionic Occupation Numbers	Christian Schilling	2013-01-21	Scientific Series	View details
Indirect Searches for Dark Matter with the Fermi Large Area Telescope	Andrea Marie Albert	2013-01-18	Scientific Series	View details

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Format results

Multifield Reheating and the Fate of the Primordial Observables

A classification of symmetry enriched topological phases with exactly solvable models

Searching for topological phases in transition metal oxide heterostructures

Hidden Structure in Linguistics: The Organization of Sound Systems

How to Fall into a Black Hole

Cosmic Tides

What is motion? What is time?

Superfluid to normal phase transition in strongly interacting bosons in two and three dimensions.

A monodromy defect in the 3d Ising model.

Holographic description of cosmological singularity

Pinning of Fermionic Occupation Numbers

Indirect Searches for Dark Matter with the Fermi Large Area Telescope

Multifield Reheating and the Fate of the Primordial Observables

A classification of symmetry enriched topological phases with exactly solvable models

Searching for topological phases in transition metal oxide heterostructures

Hidden Structure in Linguistics: The Organization of Sound Systems

How to Fall into a Black Hole

Cosmic Tides

What is motion? What is time?

Superfluid to normal phase transition in strongly interacting bosons in two and three dimensions.

A monodromy defect in the 3d Ising model.

Holographic description of cosmological singularity

Pinning of Fermionic Occupation Numbers

Indirect Searches for Dark Matter with the Fermi Large Area Telescope