Talks

10573 - 10584 of 18366 Results

A unifying approach to dark energy models

David Langlois Université Paris Cité

July 09, 2013

PIRSA:13070023
Resolution of Cosmic Singularities and Bounces

Neil Turok University of Edinburgh

July 09, 2013

PIRSA:13070008
Cosmological Magnetic Fields

Tanmay Vachaspati University of Arizona

July 09, 2013

PIRSA:13070007
Soft and Coulomb resummation: squark and gluino production at the LHC

July 09, 2013

PIRSA:13070034

High Energy Physics
Remarks on Gravitational Duality

Marc Henneaux International Solvay Institutes

July 09, 2013

PIRSA:13070020
Bimetric theory, Conformal Gravity and Partial Masslessness

Fawad Hassan Stockholm University

July 09, 2013

PIRSA:13070021
Solid Inflation

Alberto Nicolis Columbia University

July 09, 2013

PIRSA:13070005
Cosmological Limits on Neutrino-Neutrino Scattering and Particle Physics in the Early Universe

Kris Sigurdson University of British Columbia

July 09, 2013

PIRSA:13070025
Searching for Other Universes

Matthew Johnson York University

July 08, 2013

PIRSA:13070029
Primordial non-Gaussianity in the CMB and large-scale structure

Kendrick Smith Perimeter Institute for Theoretical Physics

July 08, 2013

PIRSA:13070001
Tumbling through a landscape

Erick Weinberg Columbia University

July 08, 2013

PIRSA:13070024
Massive gravity and cosmology

Shinji Mukohyama Yukawa Institute for Theoretical Physics

July 08, 2013

PIRSA:13070002

A unifying approach to dark energy models

David Langlois Université Paris Cité

July 09, 2013

PIRSA:13070023

This talk will present an effective description of single field dark energy/modified gravity models, which encompasses most existing proposals. The starting point is a generic Lagrangian expressed in terms of the lapse and of the extrinsic and intrinsic curvature tensors of the uniform scalar field hypersurfaces. By expanding this Lagrangian up to quadratic order, one can describe the homogeneous background and the dynamics of linear perturbations. In particular, one can identify seven Lagrangian operators that lead to equations of motion containing at most second order derivatives, the time-dependent coefficients of three of these operators characterizing the background evolution. I will illustrate this approach with Horndeski's---or generalized Galileon---theories. Finally, I will discuss the link between this effective approach and observations.
Resolution of Cosmic Singularities and Bounces

Neil Turok University of Edinburgh

July 09, 2013

PIRSA:13070008

The AdS/CFT correspondence provides new insights and tools to answer previously inaccessible questions in quantum gravity. Among the most interesting is whether it is possible to describe a cosmological "bounce" in a mathematically complete and consistent way. In the talk, I'll discuss joint work with M. Smolkin, developing the dual description of the simplest possible 4d M-theory cosmology in the stringy regime, employing the full quantum dynamics of its dual CFT. I'll also present evidence that the description extends to the Einstein-gravity regime.
Cosmological Magnetic Fields

Tanmay Vachaspati University of Arizona

July 09, 2013

PIRSA:13070007
Soft and Coulomb resummation: squark and gluino production at the LHC

July 09, 2013

PIRSA:13070034

High Energy Physics

We consider the production of strongly interacting, heavy SUSY pairs at the LHC. When the centre of mass energy is close to the production threshold of the pair, the corresponding cross sections receive large higher-loop QCD corrections. These corrections are classified as the so-called soft logarithms and Coulomb singularities and they lead to a break down of the usual perturbation expansion. In this talk I review the origin of these large corrections and explain how they can be resummed by using Effective Field theories. Finally, I will present some resummed results for the pair production cross sections of heavy squarks and gluinos. Based on: arXiv:1202.2260 and 1211.3408.
Remarks on Gravitational Duality

Marc Henneaux International Solvay Institutes

July 09, 2013

PIRSA:13070020
Bimetric theory, Conformal Gravity and Partial Masslessness

Fawad Hassan Stockholm University

July 09, 2013

PIRSA:13070021

Ghost-free bimetric theories can be used to describe gravitational interactions in the presence of an extra neutral massive
spin-2 field that can modify gravity in non-trivial ways. They also
provide a natural framework for a possible non-linear extension of
partially masslessness known to arise in linear Fierz-Pauli theory.
This talk will describe bimetric theories and a procedure that
identifies a unique bimetric action as a candidate for a nonlinear
partially massless theory. We then show that in the low curvature
limit, the candidate partial massless theory is related to Conformal
Gravity.
Solid Inflation

Alberto Nicolis Columbia University

July 09, 2013

PIRSA:13070005

I will describe a cosmological model where primordial inflation is driven by a 'solid', defined as a system of three derivatively coupled scalar fields obeying certain symmetries and spontaneously breaking a certain subgroup of these. The symmetry breaking pattern differs drastically from that of standard inflationary models: time translations are unbroken. This prevents our model from fitting into the standard effective field theory description of adiabatic perturbations, with crucial consequences for the dynamics of cosmological perturbations. Most notably, non-gaussianities in the curvature perturbations are unusually large, with f_NL ~ 1/(\epsilon.c_s^2), and have a novel shape: peaked in the squeezed limit, with anisotropic dependence on how the limit is approached. Other unusual features include the absence of adiabatic fluctuation modes during inflation---which does not impair their presence and near scale-invariance after inflation---and a slightly blue tilt for the tensor modes.
Cosmological Limits on Neutrino-Neutrino Scattering and Particle Physics in the Early Universe

Kris Sigurdson University of British Columbia

July 09, 2013

PIRSA:13070025

In the standard model neutrinos are assumed to have streamed across the Universe since they last scattered at the weak decoupling epoch when the temperature of the standard-model plasma was ~MeV. The shear stress of free-streaming neutrinos imprints itself gravitationally on the Cosmic Microwave Background (CMB) and makes the CMB a sensitive probe of neutrino scattering. Yet, the presence of nonstandard physics in the neutrino sector may alter this standard chronology and delay neutrino free-streaming until a much later epoch. We will discuss how observations of the CMB can be used to constrain the strength of neutrino self-interactions G_eff and put limits on new physics in the neutrino sector from the early Universe. Key measurements of the CMB at large multipoles made by the Planck satellite and high-l experiments are critical for probing this physics. Within the context of conventional LambdaCDM parameters cosmological data are compatible with G_eff < 1/(56 MeV)^2 and neutrino free-streaming might be delayed until their temperature has cooled to as low as ~25 eV. Intriguingly, we also find an alternative cosmology compatible with cosmological data in which neutrinos scatter off each other until z~10^4 with a preferred interaction strength in a narrow region around G_eff = 1/(10 MeV)^2. This distinct self-interacting neutrino cosmology is characterized by somewhat lower values of both the scalar spectral index and the amplitude of primordial fluctuations. We phrase our discussion in terms of a specific scenario in which a late onset of neutrino free-streaming could occur, but in fact our constraints on the neutrino visibility function are very general.
Searching for Other Universes

Matthew Johnson York University

July 08, 2013

PIRSA:13070029
Primordial non-Gaussianity in the CMB and large-scale structure

Kendrick Smith Perimeter Institute for Theoretical Physics

July 08, 2013

PIRSA:13070001
Tumbling through a landscape

Erick Weinberg Columbia University

July 08, 2013

PIRSA:13070024
Massive gravity and cosmology

Shinji Mukohyama Yukawa Institute for Theoretical Physics

July 08, 2013

PIRSA:13070002

Title	Date	Collection	Type	Info
A unifying approach to dark energy models	2013‑07‑09	Cosmological Frontiers in Fundamental Physics 2013	Conference	View details
Resolution of Cosmic Singularities and Bounces	2013‑07‑09	Cosmological Frontiers in Fundamental Physics 2013	Conference	View details
Cosmological Magnetic Fields	2013‑07‑09	Cosmological Frontiers in Fundamental Physics 2013	Conference	View details
Soft and Coulomb resummation: squark and gluino production at the LHC	2013‑07‑09	Particle Physics	Scientific Series	View details
Remarks on Gravitational Duality	2013‑07‑09	Cosmological Frontiers in Fundamental Physics 2013	Conference	View details
Bimetric theory, Conformal Gravity and Partial Masslessness	2013‑07‑09	Cosmological Frontiers in Fundamental Physics 2013	Conference	View details
Solid Inflation	2013‑07‑09	Cosmological Frontiers in Fundamental Physics 2013	Conference	View details
Cosmological Limits on Neutrino-Neutrino Scattering and Particle Physics in the Early Universe	2013‑07‑09	Cosmological Frontiers in Fundamental Physics 2013	Conference	View details
Searching for Other Universes	2013‑07‑08	ISSYP 2011		View details
Primordial non-Gaussianity in the CMB and large-scale structure	2013‑07‑08	Cosmological Frontiers in Fundamental Physics 2013	Conference	View details
Tumbling through a landscape	2013‑07‑08	Cosmological Frontiers in Fundamental Physics 2013	Conference	View details
Massive gravity and cosmology	2013‑07‑08	Cosmological Frontiers in Fundamental Physics 2013	Conference	View details

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Format results

A unifying approach to dark energy models

Resolution of Cosmic Singularities and Bounces

Cosmological Magnetic Fields

Soft and Coulomb resummation: squark and gluino production at the LHC

Remarks on Gravitational Duality

Bimetric theory, Conformal Gravity and Partial Masslessness

Solid Inflation

Cosmological Limits on Neutrino-Neutrino Scattering and Particle Physics in the Early Universe

Searching for Other Universes

Primordial non-Gaussianity in the CMB and large-scale structure

Tumbling through a landscape

Massive gravity and cosmology

A unifying approach to dark energy models

Resolution of Cosmic Singularities and Bounces

Cosmological Magnetic Fields

Soft and Coulomb resummation: squark and gluino production at the LHC

Remarks on Gravitational Duality

Bimetric theory, Conformal Gravity and Partial Masslessness

Solid Inflation

Cosmological Limits on Neutrino-Neutrino Scattering and Particle Physics in the Early Universe

Searching for Other Universes

Primordial non-Gaussianity in the CMB and large-scale structure

Tumbling through a landscape

Massive gravity and cosmology