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Search results in Astrophysics from PIRSA

1153 - 1164 of 2140 Results

Newton’s Method in Cosmology Today

Bill Harp Western University
February 26, 2013

PIRSA:13020151
Astrophysics
12/13 PSI - Cosmology Review Lecture 5

Latham Boyle University of Edinburgh
February 25, 2013

PIRSA:13020105
Astrophysics
Beyond Massive Gravity

Rachel Rosen Carnegie Mellon University
February 25, 2013

PIRSA:13020134
Astrophysics
Gamma Rays at 130 GeV and How They Might Come from Dark Matter

Andrew Frey University of Winnipeg
February 21, 2013

PIRSA:13020139
Astrophysics

General Relativity & Quantum Cosmology
12/13 PSI - Cosmology Review Lecture 3

Latham Boyle University of Edinburgh
February 21, 2013

PIRSA:13020101
Astrophysics
12/13 PSI - Cosmology Review Lecture 2

Latham Boyle University of Edinburgh
February 20, 2013

PIRSA:13020100
Astrophysics
12/13 PSI - Cosmology Review Lecture 1

Latham Boyle University of Edinburgh
February 19, 2013

PIRSA:13020099
Astrophysics
Multifield Reheating and the Fate of the Primordial Observables

Ewan Tarrant University of Nottingham
February 05, 2013

PIRSA:13020123
Astrophysics
Cosmic Tides

Ue-Li Pen Canadian Institute for Theoretical Astrophysics (CITA)
January 29, 2013

PIRSA:13010114
Astrophysics
Holographic description of cosmological singularity

Misha Smolkin Hebrew University of Jerusalem
January 22, 2013

PIRSA:13010111
Astrophysics
Superhorizon fluctuations in de Sitter and cosmological spacetimes

Guilherme Pimentel Universiteit van Amsterdam
January 15, 2013

PIRSA:13010001
High Energy Physics

Astrophysics
Parameterizing dark sector perturbations

Jonathan Pearson Durham University
January 15, 2013

PIRSA:13010019
Astrophysics

Newton’s Method in Cosmology Today

Bill Harp Western University
February 26, 2013

PIRSA:13020151
Astrophysics
Newton’s inferences from phenomena realize an ideal of empirical success that’s richer than prediction. To realize Newton’s richer conception of empirical success a theory needs to do more than to accurately predict the phenomena it purports to explain: in addition it needs to have the phenomena accurately measure parameters of the theory. Newton’s method aims to turn theoretical questions into ones which can be empirically answered by measurements from phenomena. Propositions inferred from phenomena are provisionally accepted as guides to further research. Newton’s ideal of empirical success as agreeing measurements from diverse phenomena is appealed to in support of the radical inference to dark energy in cosmology today. Robert Kirshner (two of his PhDs share one half of 2011’s Nobel Prize in physics) gave an account of the role of cosmic microwave background measurements, to back up the supernova measurements and measurements from galaxy clustering in supporting the transition of dark energy from a wild hypothesis into an accepted background assumption that guides further research in cosmology today. This illustrates a feature of agreeing measurements from diverse phenomena that is especially important for turning data into evidence. To the extent that the sources of systematic error of the different measurements can be regarded as independent, their agreement contributes additional support for counting them as accurate rather than as mere artifacts of systematic error.
12/13 PSI - Cosmology Review Lecture 5

Latham Boyle University of Edinburgh
February 25, 2013

PIRSA:13020105
Astrophysics
Beyond Massive Gravity

Rachel Rosen Carnegie Mellon University
February 25, 2013

PIRSA:13020134
Astrophysics
In the last few years there has been a burst of progress in the field of massive gravity. The construction of consistent theories in which the graviton has a small mass has in turn led to the development a new family of compelling, consistent low-energy modifications of General Relativity. These theories improve our understanding of the interplay between gravity and particle physics and provide new approaches to solving the cosmological constant problem. In this talk I will review these recent developments. I will discuss the search among these new theories for a symmetry that has the potential to address the cosmological constant problem.
Gamma Rays at 130 GeV and How They Might Come from Dark Matter

Andrew Frey University of Winnipeg
February 21, 2013

PIRSA:13020139
Astrophysics

General Relativity & Quantum Cosmology
Gamma Rays at 130 GeV and How They Might Come from Dark Matter" I'll discuss the exciting (but somewhat controversial) new discovery of a sharp gamma ray feature at 130 GeV from near the galactic center and review some other evidence that might link it to annihilation of dark matter. I will then explain the challenges in understanding how dark matter might produce this signal and explain a model or two that overcome these difficulties.
12/13 PSI - Cosmology Review Lecture 3

Latham Boyle University of Edinburgh
February 21, 2013

PIRSA:13020101
Astrophysics
12/13 PSI - Cosmology Review Lecture 2

Latham Boyle University of Edinburgh
February 20, 2013

PIRSA:13020100
Astrophysics
12/13 PSI - Cosmology Review Lecture 1

Latham Boyle University of Edinburgh
February 19, 2013

PIRSA:13020099
Astrophysics
Multifield Reheating and the Fate of the Primordial Observables

Ewan Tarrant University of Nottingham
February 05, 2013

PIRSA:13020123
Astrophysics
The presence of additional light fields during inflation can source isocurvature fluctuations, which can cause the curvature perturbation $\zeta$, and its statistics to evolve on superhorizon scales. I will demonstrate that if these fluctuations have not completely decayed before the onset of perturbative reheating, then primordial observables such as the level of non--Gaussianity can develop substantial reheating dependant corrections. I will argue that for inflationary models where an adiabatic condition is not reached before the relevant fields begin to decay, we must be careful in our interpretation of any observational constraints that place bounds on the statistics of $\zeta$.
Cosmic Tides

Ue-Li Pen Canadian Institute for Theoretical Astrophysics (CITA)
January 29, 2013

PIRSA:13010114
Astrophysics
We apply CMB lensing techniques to large scale structure and solve for the 3-D cosmic tidal field. We use small scale filamentary structures to solve for the large scale tidal shear and gravitational potential. By comparing this to the redshift space density field, one can measure the gravitational growth factor on large scales without cosmic variance. This potentially enables accurate measurements of neutrino masses and reconstruction of radial modes lost in 21 cm intensity mapping, which are essential for CMB and other cross correlations. We relate the tidal fields to the squeezed limit bispectrum, and present initial results from simulations and data from the SDSS.
Holographic description of cosmological singularity

Misha Smolkin Hebrew University of Jerusalem
January 22, 2013

PIRSA:13010111
Astrophysics
In my talk I will discuss our recent paper hep-th/1211.1322 where we construct a 3D conformal field theory dual to asymptotically AdS cosmology in four dimensions. Due to the scale invariance this dual theory allows an infinite family of instantons each of which breaks the conformal group O(3,2) down to O(3,1). These instantons are dual to bulk instantons responsible for nucleating an O(3,1) invariant cosmological bubble. Presumably they indicate an infinite instability rate, however we are able to sum over all of them completely. The resulting theory is manifestly stable, unitary and finite.
Superhorizon fluctuations in de Sitter and cosmological spacetimes

Guilherme Pimentel Universiteit van Amsterdam
January 15, 2013

PIRSA:13010001
High Energy Physics

Astrophysics
I will discuss superhorizon fluctuations in de Sitter space. The first part of the talk will focus on computing entanglement entropies of field theories in a fixed de Sitter background. Those computations are done for free theories and also theories with gravity duals. If time permits, I will also discuss superhorizon fluctuations in cosmological backgrounds. In particular, I focus on showing that subhorizon fluctuations can not produce any significant backreaction on superhorizon modes. If those late time effects existed, one in principle could not trust the scale invariant spectrum of inflationary theories to be the source of the spectrum of thermal fluctuations of the CMB.
Parameterizing dark sector perturbations

Jonathan Pearson Durham University
January 15, 2013

PIRSA:13010019
Astrophysics
When recent observational evidence and the GR+FRW+CDM model are combined we obtain the result that the Universe is accelerating, where the acceleration is due to some not-yet-understood "dark sector". There has been a considerable number of theoretical models constructed in an attempt to provide an "understanding" of the dark sector: dark energy and modified gravity theories. The proliferation of modified gravity and dark energy models has brought to light the need to construct a "generic" way to parameterize the dark sector. We will discuss our new way of approaching this problem, looking at linearised perturbations. Our approach is inspired by that taken in particle physics, where the most general modifications to the standard model are written down for a given field content that is compatible with some assumed symmetry (which we take to be isotropy of the background spatial sections). Our emphasis is on constructing a theoretically motivated toolkit which can be used to extract meaningful information about the dark sector (such as its field content). We find, for example, that the observational impact of very broad classes of theories can be encoded by a very small (less than 5) number of parameters. It is these parameters which we hope to measure with observational data.

Title	Date	Collection	Type	Info
Newton’s Method in Cosmology Today	2013‑02‑26	Cosmology and Gravitation	Scientific Series	View details
12/13 PSI - Cosmology Review Lecture 5	2013‑02‑25	12/13 PSI - Cosmology Review	Course	View details
Beyond Massive Gravity	2013‑02‑25	Colloquium	Scientific Series	View details
Gamma Rays at 130 GeV and How They Might Come from Dark Matter	2013‑02‑21	Strong Gravity	Scientific Series	View details
12/13 PSI - Cosmology Review Lecture 3	2013‑02‑21	12/13 PSI - Cosmology Review	Course	View details
12/13 PSI - Cosmology Review Lecture 2	2013‑02‑20	12/13 PSI - Cosmology Review	Course	View details
12/13 PSI - Cosmology Review Lecture 1	2013‑02‑19	12/13 PSI - Cosmology Review	Course	View details
Multifield Reheating and the Fate of the Primordial Observables	2013‑02‑05	Cosmology and Gravitation	Scientific Series	View details
Cosmic Tides	2013‑01‑29	Cosmology and Gravitation	Scientific Series	View details
Holographic description of cosmological singularity	2013‑01‑22	Cosmology and Gravitation	Scientific Series	View details
Superhorizon fluctuations in de Sitter and cosmological spacetimes	2013‑01‑15	Quantum Fields and Strings	Scientific Series	View details
Parameterizing dark sector perturbations	2013‑01‑15	Cosmology and Gravitation	Scientific Series	View details

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Format results

Newton’s Method in Cosmology Today

12/13 PSI - Cosmology Review Lecture 5

Beyond Massive Gravity

Gamma Rays at 130 GeV and How They Might Come from Dark Matter

12/13 PSI - Cosmology Review Lecture 3

12/13 PSI - Cosmology Review Lecture 2

12/13 PSI - Cosmology Review Lecture 1

Multifield Reheating and the Fate of the Primordial Observables

Cosmic Tides

Holographic description of cosmological singularity

Superhorizon fluctuations in de Sitter and cosmological spacetimes

Parameterizing dark sector perturbations

Newton’s Method in Cosmology Today

12/13 PSI - Cosmology Review Lecture 5

Beyond Massive Gravity

Gamma Rays at 130 GeV and How They Might Come from Dark Matter

12/13 PSI - Cosmology Review Lecture 3

12/13 PSI - Cosmology Review Lecture 2

12/13 PSI - Cosmology Review Lecture 1

Multifield Reheating and the Fate of the Primordial Observables

Cosmic Tides

Holographic description of cosmological singularity

Superhorizon fluctuations in de Sitter and cosmological spacetimes

Parameterizing dark sector perturbations