Astrophysics

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Some Conceptual Problems in General Relativity and Cosmology

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

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

Brian Dolan National University of Ireland
May 20, 2014

PIRSA:14050093
Astrophysics
What can we learn from modifing gravity ?

Claudia de Rham Imperial College London
May 14, 2014

PIRSA:14050003
Astrophysics
Random models of inflation

Andrew Liddle University of Lisbon
May 13, 2014

PIRSA:14050007
Astrophysics
Noncommutative geometry and the symmetries of the standard model

Fedele Lizzi University of Naples Federico II
May 06, 2014

PIRSA:14050031
High Energy Physics

Astrophysics
The Case for an Alternative Cosmology

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

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

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

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

Arif Babul University of Victoria
April 15, 2014

PIRSA:14040133
Astrophysics
Is the Milky Way Ringing?

Lawrence Widrow Queen's University
April 08, 2014

PIRSA:14040137
Astrophysics
The not-so-homogeneous universe

Phil Bull Queen Mary University of London
April 01, 2014

PIRSA:14040129
Astrophysics
Effective field theory for hydrodynamical systems

Alberto Nicolis Columbia University
March 28, 2014

PIRSA:14030121
High Energy Physics

Astrophysics
Cosmic initial conditions and the CMB

Daniel Grin California Institute of Technology
March 25, 2014

PIRSA:14030112
Astrophysics

Some Conceptual Problems in General Relativity and Cosmology

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

PIRSA:14060004
Astrophysics
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 National University of Ireland
May 20, 2014

PIRSA:14050093
Astrophysics
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.
What can we learn from modifing gravity ?

Claudia de Rham Imperial College London
May 14, 2014

PIRSA:14050003
Astrophysics
I will review models of modified gravity in the infrared and show how extra degrees of freedom present in these theories get screened via the Vainshtein mechanism. That mechanism comes hand in hand with its own share of peculiarities: classical superluminalities, strong coupling and perturbative non-analyticity of the S-matrix to name a few. From a traditional effective field viewpoint such effects are disastrous but I will present the first hints in understanding these theories beyond the traditional perspective and their implications not only for gravity but also for our understanding of a certain class of field theories.
Random models of inflation

Andrew Liddle University of Lisbon
May 13, 2014

PIRSA:14050007
Astrophysics
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.
Noncommutative geometry and the symmetries of the standard model

Fedele Lizzi University of Naples Federico II
May 06, 2014

PIRSA:14050031
High Energy Physics

Astrophysics
I will describe Connes approach to the standard model based on spectral noncommutative geometry with particular emphasis on the symmetries. The model poses constraints which are satisfied by the standard model group, and does not leave much room for other possibilities. There is however a possibility for a larger symmetry (the ``grand algebra'') which may also be instrumental to obtain the correct mass of the Higgs.
The Case for an Alternative Cosmology

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

PIRSA:14050034
Astrophysics
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
Astrophysics
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
Astrophysics
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
Astrophysics
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
Astrophysics
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
Effective field theory for hydrodynamical systems

Alberto Nicolis Columbia University
March 28, 2014

PIRSA:14030121
High Energy Physics

Astrophysics
I will review a recently proposed formalism that describes fluids and superfluids in effective field theory terms. I will then focus on applying this formalism to peculiar string-like objects that exist in fluid systems: vortex lines and vortex rings. These do not obey Newton's second law, and, as a consequence, their behavior is highly counterintuitive. I will describe how effective field theory provides us with an optimal tool to understand how they move and how they interact with one another and with sound.
Cosmic initial conditions and the CMB

Daniel Grin California Institute of Technology
March 25, 2014

PIRSA:14030112
Astrophysics
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

Title	Speaker(s)	Date	Talk Type	Info link
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
What can we learn from modifing gravity ?	Claudia de Rham	2014-05-14	Scientific Series	View details
Random models of inflation	Andrew Liddle	2014-05-13	Scientific Series	View details
Noncommutative geometry and the symmetries of the standard model	Fedele Lizzi	2014-05-06	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
Effective field theory for hydrodynamical systems	Alberto Nicolis	2014-03-28	Scientific Series	View details
Cosmic initial conditions and the CMB	Daniel Grin	2014-03-25	Scientific Series	View details

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Some Conceptual Problems in General Relativity and Cosmology

Black holes and Boyle's Law --- the thermodynamics of Einstein's greatest mistake

What can we learn from modifing gravity ?

Random models of inflation

Noncommutative geometry and the symmetries of the standard model

The Case for an Alternative Cosmology

Galileon Maps: Inequivalent Coset Constructions for Spacetime Symmetries

Groups and Clusters of Galaxies: Where Cosmology and Astrophysics Collide

Is the Milky Way Ringing?

The not-so-homogeneous universe

Effective field theory for hydrodynamical systems

Cosmic initial conditions and the CMB

Some Conceptual Problems in General Relativity and Cosmology

Black holes and Boyle's Law --- the thermodynamics of Einstein's greatest mistake

What can we learn from modifing gravity ?

Random models of inflation

Noncommutative geometry and the symmetries of the standard model

The Case for an Alternative Cosmology

Galileon Maps: Inequivalent Coset Constructions for Spacetime Symmetries

Groups and Clusters of Galaxies: Where Cosmology and Astrophysics Collide

Is the Milky Way Ringing?

The not-so-homogeneous universe

Effective field theory for hydrodynamical systems

Cosmic initial conditions and the CMB