Scientific Series

Displaying 3553 - 3564 of 5007

Astrophysical shear-driven turbulence

Jeremy Goodman Princeton University

October 17, 2012

PIRSA:12100043
Constraining RG flow in three-dimensional field theory

Benjamin Safdi Massachusetts Institute of Technology (MIT)
October 16, 2012

PIRSA:12100054
High Energy Physics
Now what?: Higgs physics after discovery

Nathaniel Craig University of California, Santa Barbara
October 16, 2012

PIRSA:12100060
High Energy Physics
Maximum entropy, the universal dark matter density profile... and its destruction

Andrew Pontzen University of Oxford
October 16, 2012

PIRSA:12100003
Astrophysics
The effect of initial correlations on the evolution of quantum states

Mark Byrd Southern Illinois University
October 15, 2012

PIRSA:12100045
Quantum Physics
Warm Superconductors

Baskaran Ganapathy Institute of Mathematical Sciences

October 10, 2012

PIRSA:12100059
New Directions in Categorical Logic for Classical, Probabilistic and Quantum Physics

Tobias Fritz Universität Innsbruck
October 09, 2012

PIRSA:12100055
Mathematical Physics
AdS(3)/CFT(2) correspondence and integrability

Konstantin Zarembo Nordic Institute for Theoretical Physics
October 09, 2012

PIRSA:12100062
High Energy Physics

Mathematical Physics
Voids in the SDSS: from demography to cosmology

Paul Sutter Institut d'Astrophysique de Paris
October 09, 2012

PIRSA:12100041
Astrophysics
Scalars with Higher Derivatives in Supergravity and Cosmology

Jean-Luc Lehners Self Employed
October 09, 2012

PIRSA:12100042
Astrophysics
Testing Strong-Field General Relativity with Black Holes

Tim Johannsen

October 04, 2012

PIRSA:12100049
A Higgs but no sparticles yet: what it means for the (p)MSSM

Ahmed Ismail University of Pittsburgh
October 02, 2012

PIRSA:12100052
High Energy Physics

Astrophysical shear-driven turbulence

Jeremy Goodman Princeton University

October 17, 2012

PIRSA:12100043

Astronomical hydrodynamics is usually almost ideal in the sense that the Reynolds number (Re) is enormous and any effective viscosity must be due to shocks or turbulence. Astronomical magnetohydrodynamics (MHD) is often also nearly ideal, so that magnetic fields and plasma are well coupled. In particular, dissipation of orbital energy in accretion disks around black holes is readily explained by MHD turbulence. On the other hand, the planet-bearing disks around protostars are magnetically far from ideal because of very low fractional ionization. MHD turbulence is at best marginal in these disks, yet accretion is observed. The Reynolds numbers based on orbital-velocity gradients are enormous, so by analogy with high-Re terrestrial flows, one might expect hydrodynamic (i.e., unmagnetized) turbulence. Direct numerical simulations indicate that such turbulence is somehow suppressed by keplerian rotation, though the mechanism is
unclear and the simulations are limited in Re. Recently, a few groups have studied the question via Taylor-Couette experiments at somewhat higher Re, obtaining conflicting results. Complicating and enriching this debate is the recent discovery that turbulence tends to have a finite lifetime in shear flows that admit a formally linearly stable laminar solution: this includes flow in smooth pipes and probably also unmagnetized keplerian disks. Some suggestions will be offered as to how these open questions might be resolved.
Constraining RG flow in three-dimensional field theory

Benjamin Safdi Massachusetts Institute of Technology (MIT)
October 16, 2012

PIRSA:12100054
High Energy Physics
The entanglement entropy S(R) across a circle of radius R has been invoked recently in deriving general constraints on renormalization group flow in three-dimensional field theory. At conformal fixed points, the negative of the finite part of the entanglement entropy, which is called F, is equal to the free energy on the round three-sphere. The F-theorem states that F decreases under RG flow. Along the RG flow it has recently been shown that the renormalized entanglement entropy {\cal F}(R) = -S(R) + R S'(R), which is equal to F at the fixed points, is a monotonically decreasing function. I will review various three-dimensional field theories where we can calculate F on the three-sphere and compute its change under RG flow, including free field theories, perturbative fixed points, large N field theories with double trace deformations, gauge theories with large numbers of flavors, and supersymmetric theories with at least {\cal N} = 2 supersymmetry. I will also present calculations of the renormalized entanglement entropy along the RG flow in free massive field theory and in holographic examples.
Now what?: Higgs physics after discovery

Nathaniel Craig University of California, Santa Barbara
October 16, 2012

PIRSA:12100060
High Energy Physics
With the discovery of a new Higgs-like particle at the LHC, there is an unprecedented opportunity to use the Higgs as a probe for physics beyond the Standard Model. I will discuss a variety of recent ideas to look for new physics via the Higgs, including measurements of Higgs couplings and associated indirect observables; searches for Higgs production in association with new physics; and strategies for probing extended electroweak symmetry breaking sectors.
Maximum entropy, the universal dark matter density profile... and its destruction

Andrew Pontzen University of Oxford
October 16, 2012

PIRSA:12100003
Astrophysics
I review some recent developments in attempting to reconcile the observed galaxy population with numerical models of structure formation in the 'LCDM' concordance cosmology. Focussing on behaviour of dwarf galaxies, I describe the infamous 'cusp-core' dichotomy -- a long-standing challenge to the LCDM picture on small scales -- and use toy models to show how it is resolved in recent numerical simulations (Pontzen & Governato 2012). I then discuss the current observational status of this picture (Teyssier, Pontzen & Read 2012; Penarrubia et al 2012).

In the second half of the talk, I apply the analytic techniques developed for probing the effect of gas on dark matter dynamics to the question of how, in the absence of baryons, a universal "NFW" dark matter halo profile emerges (independent of scale or details of the initial conditions).

Thus the generation of NFW halos on the one hand and the destruction of their central cusps on the other can be ascribed to surprisingly similar physical arguments.
The effect of initial correlations on the evolution of quantum states

Mark Byrd Southern Illinois University
October 15, 2012

PIRSA:12100045
Quantum Physics
Until fairly recently, it was generally assumed that the initial state of a quantum system prepared for information processing was in a product state with its environment. If this is the case,
the evolution is described by a completely positive map. However, if the system and environment are initially correlated, or entangled, such that the so-called quantum discord is non-zero, then the
evolution is described by a map which is not completely positive. Maps that are not completely positive are not as well understood and the implications of having such a map are not completely known. I will discuss a few examples and a theorem (or two) which may help us understand the implications of having maps which are not completely positive.
Warm Superconductors

Baskaran Ganapathy Institute of Mathematical Sciences

October 10, 2012

PIRSA:12100059
New Directions in Categorical Logic for Classical, Probabilistic and Quantum Physics

Tobias Fritz Universität Innsbruck
October 09, 2012

PIRSA:12100055
Mathematical Physics
I will give an idea of what category theory is and how it can be successfully applied in mathematics and the mathematical sciences by means of example. The example is a notion from mathematical logic formalizing the intuitive concept of "property". The new category-theoretical definition of this notion can physically be interpreted as a measurement. Unraveling this definition in particular categories can be regarded as defining the concept of "property" in different context, e.g. in classical, probabilistic and quantum physics, and in each case this recovers familiar things.
Disclaimer: Up to some differences in the technical details, all of this is work of Bart Jacobs. (See arXiv:1205.3940)
AdS(3)/CFT(2) correspondence and integrability

Konstantin Zarembo Nordic Institute for Theoretical Physics
October 09, 2012

PIRSA:12100062
High Energy Physics

Mathematical Physics
Integrability has been successfully used to compute the non-perturbative spectrum, Wilson loops and scattering amplitudes in the AdS/CFT correspondence. Most of these results apply to N=4, D=4 SYM / strings on AdS(5)xS(5). Strings on AdS(3)xM, where M is either S(3)xT(4) or S(3)xS(3)xS(1), are also integrable and potentially solvable by the same methods (Bethe ansatz, Y-system, TBA etc). An interesting aspect of string theory on AdS(3) is a large number of parameters that preserve integrability. One parameters, in particular, interpolates between the integrable RR AdS(3) background and conformal NSNS background described by a non-compact WZW model. Another interesting aspect of string theory on AdS(3) is emergence of target-space Viraroso symmetry. I will review how integrability arises in the AdS(3)/CFT(2) correspondence, and will describe what is (not) know about the Bethe ansatz solution of the relevant sigma-models.
Voids in the SDSS: from demography to cosmology

Paul Sutter Institut d'Astrophysique de Paris
October 09, 2012

PIRSA:12100041
Astrophysics
Cosmic voids are potentially a rich source of information for both astrophysics and cosmology. To enable such science, we produce the most comprehensive void catalog to date using the Sloan Digital Sky Survey Data Release 7 main sample out to redshift z = 0.2 and the Luminous Red Galaxy sample out to z = 0.44. Using a modified version of the parameter-free void finder ZOBOV, we fully take into account the presence of survey boundary and masks. We discuss basic catalog statistics such as number counts and redshift distributions, as well as describe some example data products derived from our catalog, such as radial density profiles and projected density maps. Using this catalog, we report on the first application of the Alcock-Paczynski test to stacked voids in spectroscopic redshift surveys by applying the shape-fitting procedure presented in Lavaux & Wandelt (2011) to ten void stacks out to redshift z = 0.36. Our results are consistent with WMAP 7-year cosmological constraints. We compare our results to alternate methods of constructing void stacks and comment on future observational prospects.
Scalars with Higher Derivatives in Supergravity and Cosmology

Jean-Luc Lehners Self Employed
October 09, 2012

PIRSA:12100042
Astrophysics
There are many situations in cosmology that motivate the study of scalar fields with higher-derivative actions. The best-known such situations are probably k-inflation (with DBI-inflation being a special case) and models based on galileon theories, but even eternal inflation and cyclic universes provide good reasons to study such theories. After an extended discussion of the motivations, I will show how scalar field theories with higher derivatives can be constructed in (minimal, 4-dimensional) supergravity, and will discuss their properties, especially in regard to their cosmological applications.
Testing Strong-Field General Relativity with Black Holes

Tim Johannsen

October 04, 2012

PIRSA:12100049
A Higgs but no sparticles yet: what it means for the (p)MSSM

Ahmed Ismail University of Pittsburgh
October 02, 2012

PIRSA:12100052
High Energy Physics
The phenomenological Minimal Supersymmetric Standard Model (pMSSM) provides a broad perspective on supersymmetric phenomenology. We have generated two large sets of pMSSM models with neutralino and gravitino LSPs, with sparticle masses extending up to 4 TeV. In this talk, I will discuss the implications of searches for supersymmetry and the Higgs, with particular attention to naturalness. In particular, we find that while sparticle spectra with moderately light stops are still allowed, such stops are difficult to find experimentally because of a wide array of possible cascade decays.

Title	Speaker(s)	Date	Talk Type	Info link
Astrophysical shear-driven turbulence	Jeremy Goodman	2012-10-17	Scientific Series	View details
Constraining RG flow in three-dimensional field theory	Benjamin Safdi	2012-10-16	Scientific Series	View details
Now what?: Higgs physics after discovery	Nathaniel Craig	2012-10-16	Scientific Series	View details
Maximum entropy, the universal dark matter density profile... and its destruction	Andrew Pontzen	2012-10-16	Scientific Series	View details
The effect of initial correlations on the evolution of quantum states	Mark Byrd	2012-10-15	Scientific Series	View details
Warm Superconductors	Baskaran Ganapathy	2012-10-10	Scientific Series	View details
New Directions in Categorical Logic for Classical, Probabilistic and Quantum Physics	Tobias Fritz	2012-10-09	Scientific Series	View details
AdS(3)/CFT(2) correspondence and integrability	Konstantin Zarembo	2012-10-09	Scientific Series	View details
Voids in the SDSS: from demography to cosmology	Paul Sutter	2012-10-09	Scientific Series	View details
Scalars with Higher Derivatives in Supergravity and Cosmology	Jean-Luc Lehners	2012-10-09	Scientific Series	View details
Testing Strong-Field General Relativity with Black Holes	Tim Johannsen	2012-10-04	Scientific Series	View details
A Higgs but no sparticles yet: what it means for the (p)MSSM	Ahmed Ismail	2012-10-02	Scientific Series	View details

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Format results

Astrophysical shear-driven turbulence

Constraining RG flow in three-dimensional field theory

Now what?: Higgs physics after discovery

Maximum entropy, the universal dark matter density profile... and its destruction

The effect of initial correlations on the evolution of quantum states

Warm Superconductors

New Directions in Categorical Logic for Classical, Probabilistic and Quantum Physics

AdS(3)/CFT(2) correspondence and integrability

Voids in the SDSS: from demography to cosmology

Scalars with Higher Derivatives in Supergravity and Cosmology

Testing Strong-Field General Relativity with Black Holes

A Higgs but no sparticles yet: what it means for the (p)MSSM

Astrophysical shear-driven turbulence

Constraining RG flow in three-dimensional field theory

Now what?: Higgs physics after discovery

Maximum entropy, the universal dark matter density profile... and its destruction

The effect of initial correlations on the evolution of quantum states

Warm Superconductors

New Directions in Categorical Logic for Classical, Probabilistic and Quantum Physics

AdS(3)/CFT(2) correspondence and integrability

Voids in the SDSS: from demography to cosmology

Scalars with Higher Derivatives in Supergravity and Cosmology

Testing Strong-Field General Relativity with Black Holes

A Higgs but no sparticles yet: what it means for the (p)MSSM