Conference

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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
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
Precision Holographic Cosmology

Paul McFadden Durham University

July 08, 2013

PIRSA:13070006
Intermittent non-Gaussianity & Anomalies: rare patchy subdominants from Modulated Heating, Bubble Collisions & Oscillons

Richard Bond Canadian Institute for Theoretical Astrophysics (CITA)

July 08, 2013

PIRSA:13070000
Opening Remarks

Neil Turok University of Edinburgh

July 08, 2013

PIRSA:13070092
Characterizing quantum non-locality: a histories approach

Joe Henson BNP Paribas Asset Management London
May 31, 2013

PIRSA:13050073
Quantum Physics
Time, cosmology and quantum foundations

Lee Smolin Perimeter Institute for Theoretical Physics
May 31, 2013

PIRSA:13050072
Quantum Physics

Astrophysics
Towards a realist's interpretation of the path integral

Petros Wallden University of Athens

May 31, 2013

PIRSA:13050071

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.
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
Precision Holographic Cosmology

Paul McFadden Durham University

July 08, 2013

PIRSA:13070006

We discuss holography for cosmology, focusing on a class of slow-roll inflationary spacetimes that are holographically dual to a perturbative RG flow between two nearby CFTs. The cosmological power spectrum and non-Gaussianities may be calculated directly from the dual QFT using conformal perturbation theory, even when the dual QFT is strongly coupled. Holography thus offers new methods for computing cosmological observables. To illustrate, we show how to recover the power spectrum to second order in slow roll.
Intermittent non-Gaussianity & Anomalies: rare patchy subdominants from Modulated Heating, Bubble Collisions & Oscillons

Richard Bond Canadian Institute for Theoretical Astrophysics (CITA)

July 08, 2013

PIRSA:13070000
Opening Remarks

Neil Turok University of Edinburgh

July 08, 2013

PIRSA:13070092
Characterizing quantum non-locality: a histories approach

Joe Henson BNP Paribas Asset Management London
May 31, 2013

PIRSA:13050073
Quantum Physics
Characterising quantum non-locality using simple physical principles has become a hot topic in quantum foundations of late. In the simpler case of local hidden variable models, the space of allowed correlations can be characterised by requiring that there exists a joint probability distribution over all possible experimental outcomes, from which the experimental probabilities arise as marginals. This follows from Bell’s causality condition. But the existing characterisations of quantum correlations are far from being so straightforward.
Motivated by a histories outlook, we propose the following condition: there exists a positive semi-definite matrix in which the indices run over all possible experimental outcomes, from which the experimental probabilities arise as “marginals” in a similar way. This is a much simpler condition than the usual statement of the existence of a quantum model for the probabilities, and suggests an underlying connection with Bell’s derivation of his bound on local correlations. I will outline existing proofs that this condition places strong bounds on correlations consistent with QM, and ask whether it could completely characterise quantum non-locality
Time, cosmology and quantum foundations

Lee Smolin Perimeter Institute for Theoretical Physics
May 31, 2013

PIRSA:13050072
Quantum Physics

Astrophysics
I argue that quantum mechanics cannot usefully be extended to a theory of the whole universe, so the task of quantum foundations is to discover that cosmological theory which reduces to quantum mechanics when restricted to small subsystems of the universe. I argue that that cosmological theory will be based on a global notion of physical time which implies the distinction between past, present and future is real and objective. These motivate two examples of novel formulations of quantum theory: the real ensemble formulation and the principle of precedence. Each may imply departures from the expected quantum evolution for sufficiently large and complex quantum systems.
Towards a realist's interpretation of the path integral

Petros Wallden University of Athens

May 31, 2013

PIRSA:13050071

Having a fundamental spacetime view of physics, appears more justified in attempting to construct a quantum theory of gravity. In this talk, motivated by the latter, a path integral approach is adopted and an attempt to construct a self-consistent realistic histories formulation of quantum theory is presented. After revising the histories viewpoint of classical physics, the quantum case is considered. However, the nature of the probabilities arising from the path integral, leads us to alter the classical picture. The new ontology is that of a coevent (or a coarse grained history), and we analyse the consequences of this (relatively) novel proposal.

Title	Speaker(s)	Date	Talk Type	Info link
Bimetric theory, Conformal Gravity and Partial Masslessness	Fawad Hassan	2013-07-09	Conference	View details
Solid Inflation	Alberto Nicolis	2013-07-09	Conference	View details
Cosmological Limits on Neutrino-Neutrino Scattering and Particle Physics in the Early Universe	Kris Sigurdson	2013-07-09	Conference	View details
Primordial non-Gaussianity in the CMB and large-scale structure	Kendrick Smith	2013-07-08	Conference	View details
Tumbling through a landscape	Erick Weinberg	2013-07-08	Conference	View details
Massive gravity and cosmology	Shinji Mukohyama	2013-07-08	Conference	View details
Precision Holographic Cosmology	Paul McFadden	2013-07-08	Conference	View details
Intermittent non-Gaussianity & Anomalies: rare patchy subdominants from Modulated Heating, Bubble Collisions & Oscillons	Richard Bond	2013-07-08	Conference	View details
Opening Remarks	Neil Turok	2013-07-08	Conference	View details
Characterizing quantum non-locality: a histories approach	Joe Henson	2013-05-31	Conference	View details
Time, cosmology and quantum foundations	Lee Smolin	2013-05-31	Conference	View details
Towards a realist's interpretation of the path integral	Petros Wallden	2013-05-31	Conference	View details

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Format results

Bimetric theory, Conformal Gravity and Partial Masslessness

Solid Inflation

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

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

Tumbling through a landscape

Massive gravity and cosmology

Precision Holographic Cosmology

Intermittent non-Gaussianity & Anomalies: rare patchy subdominants from Modulated Heating, Bubble Collisions & Oscillons

Opening Remarks

Characterizing quantum non-locality: a histories approach

Time, cosmology and quantum foundations

Towards a realist's interpretation of the path integral

Bimetric theory, Conformal Gravity and Partial Masslessness

Solid Inflation

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

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

Tumbling through a landscape

Massive gravity and cosmology

Precision Holographic Cosmology

Intermittent non-Gaussianity & Anomalies: rare patchy subdominants from Modulated Heating, Bubble Collisions & Oscillons

Opening Remarks

Characterizing quantum non-locality: a histories approach

Time, cosmology and quantum foundations

Towards a realist's interpretation of the path integral