Cosmology and Gravitation

Displaying 361 - 372 of 694

Wild and tame scalar-tensor black holes

Valerio Faraoni Bishop's University
June 10, 2014

PIRSA:14060043
Cosmology
Some Conceptual Problems in General Relativity and Cosmology

Jayant Narlikar IUCAA - The Inter-University Centre for Astronomy and Astrophysics
June 03, 2014

PIRSA:14060004
Cosmology
Black holes and Boyle's Law --- the thermodynamics of Einstein's greatest mistake

Brian Dolan Maynooth University
May 20, 2014

PIRSA:14050093
Cosmology
Random models of inflation

Andrew Liddle University of Lisbon
May 13, 2014

PIRSA:14050007
Cosmology
The Case for an Alternative Cosmology

Jayant Narlikar IUCAA - The Inter-University Centre for Astronomy and Astrophysics
May 06, 2014

PIRSA:14050034
Cosmology
Galileon Maps: Inequivalent Coset Constructions for Spacetime Symmetries

Gabirele Trevisan SISSA International School for Advanced Studies
April 29, 2014

PIRSA:14040132
Cosmology
Groups and Clusters of Galaxies: Where Cosmology and Astrophysics Collide

Arif Babul University of Victoria
April 15, 2014

PIRSA:14040133
Cosmology
Is the Milky Way Ringing?

Lawrence Widrow Queen's University
April 08, 2014

PIRSA:14040137
Cosmology
The not-so-homogeneous universe

Phil Bull Queen Mary University of London
April 01, 2014

PIRSA:14040129
Cosmology
Cosmic initial conditions and the CMB

Daniel Grin California Institute of Technology
March 25, 2014

PIRSA:14030112
Cosmology
Inflation After Planck
March 18, 2014

PIRSA:14030116
Cosmology
SDSS-III BOSS and Beyond: fundamental physics with galaxy redshift surveys

Beth Reid Lawrence Berkeley National Laboratory
March 11, 2014

PIRSA:14030096
Cosmology

Wild and tame scalar-tensor black holes

Valerio Faraoni Bishop's University
June 10, 2014

PIRSA:14060043
Cosmology
In scalar-tensor gravity, black holes do not obey the Jebsen-Birkhoff theorem. Non-isolated black holes can be highly dynamical and the teleological concept of event horizon is replaced by the apparent or trapping horizon. Dynamical solutions describing inhomogeneities embedded in cosmological "backgrounds" and the phenomenology of their apparent horizons, which often appear/vanish in pairs, will be described. Isolated black holes, in contrast, have no hair and are the same as in general relativity.
Some Conceptual Problems in General Relativity and Cosmology

Jayant Narlikar IUCAA - The Inter-University Centre for Astronomy and Astrophysics
June 03, 2014

PIRSA:14060004
Cosmology
This talk will try to highlight some basic problems connected with conclusions uncritically drawn from well known works. These include: 1. The Schwarzschild solution 2. The formation of black holes by gravitational collapse 3. The no hair theorem 4. The principle of equivalence in the very early universe.
Black holes and Boyle's Law --- the thermodynamics of Einstein's greatest mistake

Brian Dolan Maynooth University
May 20, 2014

PIRSA:14050093
Cosmology
The thermodynamics of black holes will be reviewed and recent developments incorporating pressure into the first law described. The asymptotically AdS Kerr metric has a van der Waals type critical point with a line of first order phase transitions terminating at a critical point with mean field exponents. The phase structure and stability of black holes in higher dimensions will also be described.
Random models of inflation

Andrew Liddle University of Lisbon
May 13, 2014

PIRSA:14050007
Cosmology
Rather than writing down specific functional forms, one can generate inflation models via stochastic processes in order to explore generic properties of inflation models. I describe our explorations of the phenomenology of randomly-generated multi-field inflation models, both for canonical fields and for a braneworld-motivated scenario. Implications of some recent observational results, including BICEP2, will be discussed.
The Case for an Alternative Cosmology

Jayant Narlikar IUCAA - The Inter-University Centre for Astronomy and Astrophysics
May 06, 2014

PIRSA:14050034
Cosmology
This talk will describe the Quasi-Steady State Cosmology proposed in 1993 by Fred Hoyle, Geoffrey Burbidge and Jayant Narlikar. Starting with the motivation for this exercise, a formal field theoretic framework inspired by Mach’s principle is shown to lead to this model. The model is a generalization of the classical steady state model in the sense that it is driven by a scalar field which causes creation in explosive form. Such ‘minicreation events’ lead to a universe with a long term de Sitter expansion superposed with oscillations of shorter time scales. It is shown that this cosmology explains all the observed cosmological features and that there exist potential tests to distinguish between this cosmology and the standard big bang cosmology.
Galileon Maps: Inequivalent Coset Constructions for Spacetime Symmetries

Gabirele Trevisan SISSA International School for Advanced Studies
April 29, 2014

PIRSA:14040132
Cosmology
Non-linear realizations of spacetime symmetries can be obtained by a generalization of the coset construction valid for internal ones. The physical equivalence of different representations for spacetime symmetries is not obvious, since their relation involves not only a redefinition of the fields but also a field-dependent change of coordinates. A simple and relevant spacetime symmetry is obtained by the contraction of the 4D conformal group that leads to the Galileon group. In this talk I will analyze two non-linear realizations of this group, focusing in particular on the propagation of signals around non-trivial backgrounds.
Groups and Clusters of Galaxies: Where Cosmology and Astrophysics Collide

Arif Babul University of Victoria
April 15, 2014

PIRSA:14040133
Cosmology
Groups and clusters of galaxies are the most massive gravitationally bound objects in the Universe. They are also the most recent cosmic objects to form. In the currently accepted models of cosmic structure formation, the number density distribution of the most massive of these systems, and how this has been changing with time, depend sensitively to the parameters describing the large-scale geometry and the expansion history of the universe. However, to exploit galaxy clusters as cosmological probes, we must be able to relate their observable properties to their total mass. I will discuss our ongoing effort to calibrate the X-ray/SZ observations to the total mass for the 50 clusters comprising the Canadian Cluster Comparison Project (CCCP) sample. Resulting scaling relations, the associated scatter, and even how these change with time, invariably depend on "astrophysics" unfolding in these systems. The precision with which the cosmological parameters can be determined depends critically on how well we understand why groups and clusters manifest the observed properties that they do. This, however, has proven challenging. I will provide an update of the current state of affairs and highlight some of the key gaps in our understanding of the underlying physics.
Is the Milky Way Ringing?

Lawrence Widrow Queen's University
April 08, 2014

PIRSA:14040137
Cosmology
Recent observations from three different astronomical surveys have revealed evidence for asymmetries about the Galactic midplane in the kinematics of solar neighborhood stars. These asymmetries appear, in part, as compression-rarefaction modes in the bulk motions of stars perpendicular to the midplane. I will discuss the hypothesis that these motions were caused by the recent passage of a satellite galaxy or dark matter subhalo through the Galactic disk. In short, we may be witnessing the early stages of a disk-heating event during which the Galaxy's disk relaxes to a new state after interacting with substructure from its own halo.
The not-so-homogeneous universe

Phil Bull Queen Mary University of London
April 01, 2014

PIRSA:14040129
Cosmology
The assumption of spatial homogeneity lies at the heart of the concordance cosmological model. But as I will discuss, truly solid empirical evidence for global (statistical) homogeneity is lacking, and tricky theoretical issues abound. I review a few recent advances in understanding the role inhomogeneity plays in cosmology, including some unexpected effects on light propagation, the death (and rebirth) of backreaction, and impending observational annoyances related to the lumpy local Universe. I'll also talk about some near-future observations that can give us a handle on these effects
Cosmic initial conditions and the CMB

Daniel Grin California Institute of Technology
March 25, 2014

PIRSA:14030112
Cosmology
One new frontier in cosmology is the frequency spectrum of the CMB. Future instruments may be precise enough to measure deviations from the nearly-perfect blackbody, measuring a chemical potential and thus probing energy injection at extremely high redshift. I will discuss ($\mu$ and $y$-type) CMB spectral distortions from the dissipation of entropy (isocurvature)-sourced acoustic modes. I will then discuss how a high-energy phase transition could also source such distortions. I will then switch gears and talk about the possibility of measuring a spatial fluctuation in the baryon/DM ratio using the CMB, including recent observational results. I may also muse on the surprising possible connection between these compensated isocurvature modes and the anomalously low large-scale scalar power hinted at by Planck observations of the CMB temperature power spectrum and the recent claimed BICEP2 detection of primordial tensor modes
Inflation After Planck
March 18, 2014

PIRSA:14030116
Cosmology
The Planck satellite measurement of the cosmic microwave background has provided spectacular confirmation of the predictions of inflationary cosmology, putting inflation on a firm footing as the leading theory of the very early universe. I will discuss the implications of Planck for the simplest canonical single-field inflation models, which are favored by the data. Then I will discuss the most general question: How strong is the case that inflation is the "right" theory of the early universe?
SDSS-III BOSS and Beyond: fundamental physics with galaxy redshift surveys

Beth Reid Lawrence Berkeley National Laboratory
March 11, 2014

PIRSA:14030096
Cosmology
The SDSS-III Baryon Oscillation Spectroscopic Survey, now nearly complete, is measuring the three-dimensional cosmic structure with 1.35 million new redshifts. Galaxy clustering measurements provide constraints on the cosmic expansion history through the baryon acoustic oscillation feature and the Alcock-Paczynski effect. In addition, the imprint of galaxy peculiar velocities on the observed galaxy clustering, "redshift-space distortions", provides a measurement of the growth rate of matter perturbations. Taken together, these measurements provide excellent constraints on dark energy and test the relation between expansion history and growth of perturbations expected in General Relativity. I will summarize results from BOSS's recent DR11 results and highlight what we may learn about fundamental physics (especially neutrinos) from the upcoming Dark Energy Spectroscopic Instrument (DESI).

Title	Speaker(s)	Date	Talk Type	Info
Wild and tame scalar-tensor black holes	Valerio Faraoni	2014-06-10	Scientific Series	View details
Some Conceptual Problems in General Relativity and Cosmology	Jayant Narlikar	2014-06-03	Scientific Series	View details
Black holes and Boyle's Law --- the thermodynamics of Einstein's greatest mistake	Brian Dolan	2014-05-20	Scientific Series	View details
Random models of inflation	Andrew Liddle	2014-05-13	Scientific Series	View details
The Case for an Alternative Cosmology	Jayant Narlikar	2014-05-06	Scientific Series	View details
Galileon Maps: Inequivalent Coset Constructions for Spacetime Symmetries	Gabirele Trevisan	2014-04-29	Scientific Series	View details
Groups and Clusters of Galaxies: Where Cosmology and Astrophysics Collide	Arif Babul	2014-04-15	Scientific Series	View details
Is the Milky Way Ringing?	Lawrence Widrow	2014-04-08	Scientific Series	View details
The not-so-homogeneous universe	Phil Bull	2014-04-01	Scientific Series	View details
Cosmic initial conditions and the CMB	Daniel Grin	2014-03-25	Scientific Series	View details
Inflation After Planck		2014-03-18	Scientific Series	View details
SDSS-III BOSS and Beyond: fundamental physics with galaxy redshift surveys	Beth Reid	2014-03-11	Scientific Series	View details

Cosmology and Gravitation

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