Scientific Series

Displaying 3217 - 3228 of 5012

New Light Species and the CMB - Joint Cosmology/Particle Physics Seminar

Christopher Brust
November 19, 2013

PIRSA:13110051
Particle Physics
Topological States in Strongly-Correlated Materials

Kai Sun
University of Michigan–Ann Arbor
November 15, 2013

PIRSA:13110082
Condensed Matter
N-body lensed CMB maps: lensing extraction and characterization

Claudia Antolini
SISSA International School for Advanced Studies
November 15, 2013

PIRSA:13110088
Cosmology
Finite regions, spherical entanglement, and quantum gravity

Hal Haggard
Bard College
November 14, 2013

PIRSA:13110049
Quantum Gravity
Self-force and Green function in Schwarzschild spacetime via quasinormal modes and branch cut

Marc Casals
Universität Leipzig
November 14, 2013

PIRSA:13110067
Strong Gravity
Bulk-boundary correspondence in PEPS

Ignacio Cirac
Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)
November 13, 2013

PIRSA:13110058
Quantum Information
Spin and Long-Range Forces: The Unfinished Tale of the Last Massless Particle

Natalia Toro
Stanford University
November 13, 2013

PIRSA:13110047
Particle Physics
Quantum mechanics as an operationally time symmetric probabilistic theory

Ognyan Oreshkov
Université Libre de Bruxelles
November 12, 2013

PIRSA:13110057
Quantum Foundations
On Scale and Conformal Invariance in Four Dimensions

Anatoly Dymarsky
Skolkovo Institute of Science and Technology
November 12, 2013

PIRSA:13110068
Quantum Fields and Strings
Baryogenesis from WIMPs
November 12, 2013

PIRSA:13110046
Particle Physics
Is there evidence for additional neutrino species from cosmology?

Stephen Feeney
November 12, 2013

PIRSA:13110083
Cosmology
A universal Hamiltonian simulator: the full characterization

Gemma De Las Cuevas
Universität Innsbruck
November 11, 2013

PIRSA:13110065
Quantum Information

New Light Species and the CMB - Joint Cosmology/Particle Physics Seminar

Christopher Brust
November 19, 2013

PIRSA:13110051
Particle Physics
The effective number of neutrino species in our universe, Neff, is capable of probing the presence of new light or massless species in our universe. I will first review relevant facts about both CMB measurements of new light species and thermodynamics in the early universe. Then, I will present the effects of many models of BSM physics containing new light species on the CMB, including models containing eV-scale sterile neutrinos compatible with anomalies in neutrino experiments, and interpret the compatibility of the parameter space of these models in terms of the recent results from the Planck satellite. I will argue that the bounds on couplings obtained from the Planck measurement of the CMB are competitive with bounds coming from other areas of physics.
Topological States in Strongly-Correlated Materials

Kai Sun
University of Michigan–Ann Arbor
November 15, 2013

PIRSA:13110082
Condensed Matter
In the study of strongly-correlated insulators, a long-standing puzzle remained open for over 40 years. Some Kondo insulators (or mixed-valent insulators) display strange electrical transport that cannot be understood if one assumes that it is governed by the three-dimensional bulk. In this talk, I show that some 3D Kondo insulators have the right ingredients to be topological insulators, which we called “topological Kondo insulators”. For a topological Kondo insulator, the low-temperature transport is dominated by the 2D surface rather than the 3D bulk, because the bulk of this material is an insulator while its surface is a topologically-protected 2D metal. This theoretical picture offers a natural explanation for the long-standing puzzle mentioned above. In addition, we also find that Kondo insulators can support another type of nontrivial topological structure protected by lattice symmetries, which we called “topological crystalline Kondo insulators”. In particular, we predict that SmB$_6$ is both a topological Kondo insulator and a topological crystalline Kondo insulator and I will also discuss recent experiments, which reveal the surface states in SmB$_6$.
N-body lensed CMB maps: lensing extraction and characterization

Claudia Antolini
SISSA International School for Advanced Studies
November 15, 2013

PIRSA:13110088
Cosmology
After multiple high precision detections (ACT, SPT, Planck) gravitational lensing has become a new source of relevant cosmological information: combining it with other probes (e.g. the large scale structure) can give significant insight on the evolution of the Dark Energy component. Developing new algorithms of estimate of this signal will allow the community to exploit this observable as a new and independent probe in cosmology. In my talk I will present the reconstruction of the lensing shear pattern and its angular power spectrum from total intensity and polarised CMB maps obtained using Born approximated ray-tracing through N-body simulated structures.The recovered spectra are in agreement with predictions of the underlying ΛCDM with no visible bias, on a scale interval which extends from the arcminute to several degrees over the sky. This demonstrates the feasibility of CMB lensing studies based on large scale simulations of cosmological structure formation in the context of the upcoming large observational campaigns.
Finite regions, spherical entanglement, and quantum gravity

Hal Haggard
Bard College
November 14, 2013

PIRSA:13110049
Quantum Gravity
An exciting frontier in physics is to understand the quantum nature of gravitation in finite regions of spacetime. Study of these regions from ``below'', that is, by studying the quantum geometry of finite regions emerging from loop gravity and spin networks has recently resulted in a new road to the quantization of volume and to evidence that there is a robust gap in the volume spectrum. In this talk I will complement these results with recent work on conformal field theories in a particular finite region, a spherical ball of space. This new view afforded from ``above" gives insights into entanglement and the Reeh-Schlieder theorem, allows calculation of the entanglement spectrum, and suggests a new route to constructing the Minkowski vacuum out of independent finite regions in quantum gravity.
Self-force and Green function in Schwarzschild spacetime via quasinormal modes and branch cut

Marc Casals
Universität Leipzig
November 14, 2013

PIRSA:13110067
Strong Gravity
The modelling of gravitational wave sources is of timely interest given the exciting prospect of a first detection of gravitational waves by the new generation of detectors. The motion of a small compact object around a massive black hole deviates from a geodesic due to the action of its own field, giving rise to a self-force and the emission of gravitational waves. The self-force program has recently achieved important results using well-established methods. In this talk, we will present a different, novel method, where the self-force is calculated via the Green function of the wave equation that the field perturbation satisfies. We will present a calculation of the global Green function on Schwarzschild black hole spacetime. The calculation is carried out via a spectroscopy analysis of the Green function, which includes quasinormal modes and a branch cut in the complex-frequency plane. We will apply this analysis to calculate the self-force on a scalar charge and to reveal geometrical properties of wave propagation on a Schwarzschild background.
Bulk-boundary correspondence in PEPS

Ignacio Cirac
Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)
November 13, 2013

PIRSA:13110058
Quantum Information
TBA
Spin and Long-Range Forces: The Unfinished Tale of the Last Massless Particle

Natalia Toro
Stanford University
November 13, 2013

PIRSA:13110047
Particle Physics
The success of gauge theory descriptions of Nature follows simply, in hindsight, from Lorentz symmetry, quantum mechanics, and the existence of interacting massless particles with spin. Yet, remarkably, the most generic type of massless particle spin has never been seriously examined: Wigner's so-called "continuous spin" particles (CSPs), which have a tower of polarization states carrying all integer or half-integer helicities that mix under boosts. I will explain recent progress in understanding these particles on two fronts: simple scattering amplitudes and a free quantum field theory. The scattering amplitudes give two remarkable insights into CSP physics. First, Lorentz symmetry protects CSP interactions from the dysfunction one might expect in a theory with infinitely many polarization states: divergent cross-sections and problematic thermodynamics. Second, and most intriguingly, CSP interactions approach those of ordinary scalars or helicity-1 or 2 gauge bosons in a high-energy "correspondence" regime. While a full interacting theory of CSPs remains elusive, these results suggest that any such theory would extend Maxwell electrodynamics and/or general relativity in a viable and testable way.
Quantum mechanics as an operationally time symmetric probabilistic theory

Ognyan Oreshkov
Université Libre de Bruxelles
November 12, 2013

PIRSA:13110057
Quantum Foundations
The standard formulation of quantum mechanics is operationally asymmetric with respect to time reversal---in the language of compositions of tests, tests in the past can influence the outcomes of test in the future but not the other way around. The question of whether this represents a fundamental asymmetry or it is an artifact of the formulation is not a new one, but even though various arguments in favor of an inherent symmetry have been made, no complete time-symmetric formulation expressed in rigorous operational terms has been proposed. Here, we discuss such a possible formulation based on a generalization of the usual notion of test. We propose to regard as a test any set of events between an input and an output system which can be obtained by an autonomously defined laboratory procedure. This includes standard tests, as well as proper subsets of the complete set of outcomes of standard tests, whose realization may require post-selection in addition to pre-selection. In this approach, tests are not expected to be operations that are up to the choices of agents---the theory simply says what circuits of tests may occur and what the probabilities for their outcomes would be, given that they occur. By virtue of the definition of test, the probabilities for the outcomes of past tests can depend on tests that take place in the future. Such theories have been previously called non-causal, but here we revisit that notion of causality. Using the Choi-Jamiolkowski isomorphism, every test in that formulation, commonly regarded as inducing transformations from an input to an output system, becomes equivalent to a passive detection measurement applied jointly on two input systems---one from the past and one from the future. This is closely related to the two-state vector formalism, but it comes with a conceptual revision: every measurement is a joint measurement on two separate systems and not on one system described by states in the usual Hilbert space and its dual. We thus obtain a static picture of quantum mechanics in space-time or more general structures, in which every experiment is a local measurement on a global quantum state that generalizes the recently proposed quantum process matrix. The existence of two types of systems in the proposed formalism allows us to define causation in terms of correlations without invoking the idea of intervention, offering a possible answer to the problem of the meaning of causation. The framework is naturally compatible with closed time-like curves and other exotic causal structures.
On Scale and Conformal Invariance in Four Dimensions

Anatoly Dymarsky
Skolkovo Institute of Science and Technology
November 12, 2013

PIRSA:13110068
Quantum Fields and Strings
I will be discussing relation between scale and conformal symmetry in unitary Lorentz invariant QFTs in four dimensions.
Baryogenesis from WIMPs
November 12, 2013

PIRSA:13110046
Particle Physics
We propose a robust, unified framework, in which the similar baryon and dark matter cosmic abundances both arise from the physics of weakly interacting massive particles (WIMPs), with the rough quantitative success of the so-called “WIMP miracle”. In particular the baryon asymmetry arises from the decay of a meta-stable WIMP after its thermal freezeout at or below the weak scale. A minimal model and its embedding in R-parity violating (RPV) natural SUSY are studied as examples. The new mechanism saves RPV SUSY from the potential crisis of washing out primordial baryon asymmetry. We also consider the embedding of this idea in RPV split SUSY, where the mechanism works within the minimal model, and independently motivates the mini-split scale. Phenomenological implications for the LHC and precision tests are discussed.
Is there evidence for additional neutrino species from cosmology?

Stephen Feeney
November 12, 2013

PIRSA:13110083
Cosmology
It has been suggested that recent cosmological and flavor-oscillation data favor the existence of additional neutrino species beyond the three standard flavors. We apply Bayesian model selection to determine whether there is any evidence from current cosmological datasets for the standard cosmological model to be extended to include additional neutrino flavors. The datasets employed include cosmic microwave background temperature, polarization and lensing data, and measurements of the baryon acoustic oscillation scale and the Hubble constant. We also consider other additional neutrino physics, such as massive neutrinos, and possible degeneracies with other cosmological parameters.
A universal Hamiltonian simulator: the full characterization

Gemma De Las Cuevas
Universität Innsbruck
November 11, 2013

PIRSA:13110065
Quantum Information
We show that if the ground state energy problem of a classical spin model is NP-hard, then there exists a choice parameters of the model such that its low energy spectrum coincides with the spectrum of \emph{any} other model, and, furthermore, the corresponding eigenstates match on a subset of its spins. This implies that all spin physics, for example all possible universality classes, arise in a single model. The latter property was recently introduced and called ``Hamiltonian completeness'', and it was shown that several different models had this property. We thus show that Hamiltonian completeness is essentially equivalent to the more familiar complexity-theoretic notion of NP-completeness. Additionally, we also show that Hamiltonian completeness implies that the partition functions are the same. These results allow us to prove that the 2D Ising model with fields is Hamiltonian complete, which is substantially simpler than the previous examples of complete Hamiltonians. Joint work with Toby Cubitt.

Title	Speaker(s)	Date	Talk Type	Info link
New Light Species and the CMB - Joint Cosmology/Particle Physics Seminar	Christopher Brust	2013-11-19	Scientific Series	View details
Topological States in Strongly-Correlated Materials	Kai Sun	2013-11-15	Scientific Series	View details
N-body lensed CMB maps: lensing extraction and characterization	Claudia Antolini	2013-11-15	Scientific Series	View details
Finite regions, spherical entanglement, and quantum gravity	Hal Haggard	2013-11-14	Scientific Series	View details
Self-force and Green function in Schwarzschild spacetime via quasinormal modes and branch cut	Marc Casals	2013-11-14	Scientific Series	View details
Bulk-boundary correspondence in PEPS	Ignacio Cirac	2013-11-13	Scientific Series	View details
Spin and Long-Range Forces: The Unfinished Tale of the Last Massless Particle	Natalia Toro	2013-11-13	Scientific Series	View details
Quantum mechanics as an operationally time symmetric probabilistic theory	Ognyan Oreshkov	2013-11-12	Scientific Series	View details
On Scale and Conformal Invariance in Four Dimensions	Anatoly Dymarsky	2013-11-12	Scientific Series	View details
Baryogenesis from WIMPs		2013-11-12	Scientific Series	View details
Is there evidence for additional neutrino species from cosmology?	Stephen Feeney	2013-11-12	Scientific Series	View details
A universal Hamiltonian simulator: the full characterization	Gemma De Las Cuevas	2013-11-11	Scientific Series	View details

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