Conference

Displaying 2977 - 2988 of 4979

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 Foundations
Time, cosmology and quantum foundations

Lee Smolin Perimeter Institute for Theoretical Physics
May 31, 2013

PIRSA:13050072
Quantum Foundations

Cosmology
Towards a realist's interpretation of the path integral

Petros Wallden University of Athens

May 31, 2013

PIRSA:13050071
Generalizations of Quantum Theory
- Lucien Hardy Perimeter Institute for Theoretical Physics
- Rafael Sorkin Perimeter Institute for Theoretical Physics
- Wayne Myrvold Western University
- Howard Barnum University of New Mexico
- Joe Henson BNP Paribas Asset Management London
- Markus Müller Institute for Quantum Optics and Quantum Information (IQOQI) - Vienna
May 30, 2013

PIRSA:13050081
Quantum Information

Quantum Fields and Strings
Conjugates, Correlation and the Jordan Structure of Finite-Dimensional Quantum Theory
May 30, 2013

PIRSA:13050070
Mathematical physics

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 Foundations
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 Foundations

Cosmology
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.
Generalizations of Quantum Theory
- Lucien Hardy Perimeter Institute for Theoretical Physics
- Rafael Sorkin Perimeter Institute for Theoretical Physics
- Wayne Myrvold Western University
- Howard Barnum University of New Mexico
- Joe Henson BNP Paribas Asset Management London
- Markus Müller Institute for Quantum Optics and Quantum Information (IQOQI) - Vienna
May 30, 2013

PIRSA:13050081
Quantum Information

Quantum Fields and Strings
Conjugates, Correlation and the Jordan Structure of Finite-Dimensional Quantum Theory
May 30, 2013

PIRSA:13050070
Mathematical physics
The last few years have seen a spate of operational or information-theoretic
derivations (or \reconstructions") of nite-dimensional quantum mechanics [1]. These rest of some strong assumptions. In particular, most assume the state of a composite system is entirely determined by the joint probabilities it assigns to the outcomes of measurements on the component systems. This condition, often called local tomography, is satis ed by neither real nor quaternionic quantum theory. If we are interested in the possibilities for theories more general than orthodox quantum mechanics, we might wish to relax this constraint.
In this talk I will discuss a weaker system of assumptions, involving correla-
tions between a probabilistic system and an isomorphic conjugate system, that leads to a representation of such systems in terms of euclidean Jordan algebras [2]. These have a well-known classi cation as direct sums of real, complex or quaternionic quantum systems, possibly the exceptional Jordan algebra, and spin factors. The last are a form of \bit", characterized by a family of two-valued observables, parametrized by antipodal vectors in a sphere of arbitrary dimension. Orthodox quantum mechanics can be singled out by imposing local tomography, plus the existence of a qubit as additional axioms [3]. However, there is a natural way to form non-signaling, but generally non-locally tomo-graphic, composites of systems based on special euclidean Jordan algebras (that is, excluding the exceptional one). This yields a probabilistic theory strictly, but not wildly, more general than orthodox nite-dimensional QM; one that elegantly uni es real, complex and quaternionic quantum theory, has a simple operational basis, and allows for a spectrum of bits more general than permitted in orthodox quantum theory. Parts of this talk reflect ongoing joint work with Howard Barnum, Matthew Graydon and Cozmin Ududec.
References:
[1] G. Chiribella, M. D'Ariano and P. Perinotti, Phys. Rev. A 84, (2011), 012311-
012350; B. Dakic and C. Brukner, in H. Halvorson (ed.), Deep Beauty, Cambridge,
2011; P. Goyal, Phys. Rev. A 78 (2008), 052120-052146; L. Hardy, arXiv:quant-
ph/0101012 (2001); L. Masanes and M. Mueller, New J. Phys. 13 (2011) ; J. Rau,
Annals of Physics 324 (2009) 2622{2637;
[2] A. Wilce, Conjugates, correlation and quantum mechanics, arXiv:1206.2897 (2012)
[3] H. Barnum and A. Wilce, Local tomography and the Jordan structure of quantum
theory, arXiv:1202.4513, (2012)

Title	Speaker(s)	Date	Talk Type	Info link
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
Generalizations of Quantum Theory	Lucien Hardy, Rafael Sorkin, Wayne Myrvold, Howard Barnum, Joe Henson, Markus Müller	2013-05-30	Conference	View details
Conjugates, Correlation and the Jordan Structure of Finite-Dimensional Quantum Theory		2013-05-30	Conference	View details

Format results