Cosmology

Cosmologists at Perimeter Institute seek to help pin down the constituents and history of our universe, and the rules governing its origin and evolution. Many of the most interesting clues about physics beyond the standard model (e.g., dark matter, dark energy, the matter/anti-matter asymmetry, and the spectrum of primordial density perturbations], come from cosmological observations, and cosmological observations are often the best way to test or constrain a proposed modification of the laws of nature, since such observations can probe length scales, time scales, and energy scales that are beyond the reach of terrestrial laboratories.

Displaying 1117 - 1128 of 2128

Large Scale Bayesian Inference in Cosmology

Jens Jasche Institut d'Astrophysique de Paris
April 11, 2013

PIRSA:13040119
Cosmology
12/13 PSI - Explorations in Cosmology Lecture 4

Matthew Johnson York University
April 11, 2013

PIRSA:13040065
Cosmology
12/13 PSI - Explorations in Cosmology Lecture 3

Matthew Johnson York University
April 10, 2013

PIRSA:13040064
Cosmology
The Death Throes of Massive Stars: Supernovae, Black Holes, and Neutrinos

Evan O'Connor California Institute of Technology
April 09, 2013

PIRSA:13040120
Cosmology
12/13 PSI - Explorations in Cosmology Lecture 2

Matthew Johnson York University
April 09, 2013

PIRSA:13040063
Cosmology
12/13 PSI - Explorations in Cosmology Lecture 1

Matthew Johnson York University
April 08, 2013

PIRSA:13040062
Cosmology
Time Reborn

Lee Smolin Perimeter Institute for Theoretical Physics
April 03, 2013

PIRSA:13040103
Cosmology
Black holes as probes of fundamental physics

Vitor Cardoso Instituto Superior Tecnico - Departamento de Física
April 03, 2013

PIRSA:13040109
Particle Physics

Cosmology
Shake, Rattle and Explode: Short GRBs and the Electromagnetic Counterparts of Gravitational Wave Sources

Edo Berger Harvard University
April 02, 2013

PIRSA:13040081
Cosmology

Strong Gravity
The Effective Field Theory of Large Scale Structures

Enrico Pajer Utrecht University
March 19, 2013

PIRSA:13030110
Cosmology
Effective field theory approach to quasi-single field inflation

Masahide Yamaguchi Tokyo Institute of Technology
March 12, 2013

PIRSA:13030096
Cosmology
12/13 PSI - Cosmology Review Lecture 14

Latham Boyle University of Edinburgh
March 08, 2013

PIRSA:13030045
Cosmology

Large Scale Bayesian Inference in Cosmology

Jens Jasche Institut d'Astrophysique de Paris
April 11, 2013

PIRSA:13040119
Cosmology
Already the last decade has witnessed unprecedented progress in the collection of cosmological data. Presently proposed and designed future cosmological probes and surveys permit us to anticipate the upcoming avalanche of cosmological information during the next decades.
The increase of valuable observations needs to be accompanied with the development of efficient and accurate information processing technology in order to analyse and interpret this data. In particular, cosmography projects, aiming at studying the origin and inhomogeneous evolution of
the Universe, involve high dimensional inference methods. For example, 3d cosmological density and velocity field inference requires to explore on the order of 10^7 or more parameters. Consequently, such projects critically rely on state-of-the-art information processing techniques
and, nevertheless, are often on the verge of numerical feasibility with present day computational resources. For this reason, in this talk I will address the problem of high dimensional Bayesian inference from cosmological data sets, subject to a variety of statistical and systematic uncertainties. In particular, I will focus on the discussion of selected Markov Chain Monte Carlo techniques, permitting to efficiently solve inference problems with on the order of 10^7 parameters. Furthermore, these methods will be exemplified in various cosmological applications, raging from 3d non-linear density and photometric redshift inference to 4d physical state inference. These techniques permit us to exploit cosmologically relevant information from
observations to unprecedented detail and hence will significantly contribute to the era of precision cosmology.
12/13 PSI - Explorations in Cosmology Lecture 4

Matthew Johnson York University
April 11, 2013

PIRSA:13040065
Cosmology
12/13 PSI - Explorations in Cosmology Lecture 3

Matthew Johnson York University
April 10, 2013

PIRSA:13040064
Cosmology
The Death Throes of Massive Stars: Supernovae, Black Holes, and Neutrinos

Evan O'Connor California Institute of Technology
April 09, 2013

PIRSA:13040120
Cosmology
The endgame of massive star evolution is the gravitational-induced collapse of the central inert iron core. The collapse of the core continues until the matter reaches nuclear densities where the strong force between nucleons becomes dominant and provides sufficient pressure to stabilize the newly formed protoneutron star. What ensues is a complex multi-physics problem involving strong gravity, multidimensional hydrodynamic instabilities, magnetic fields, multispecies neutrino radiation, and supranuclear density physics to name a few.

We expect that most massive stars end this final stage of stellar evolution with a successful core-collapse supernova explosion. However, we also know that some of these core collapse events must fail and form stellar mass black holes.In his talk I will touch on two of the most important questions in core-collapse supernovae theory. I will briefly talk about what conditions are favourable for failed core-collapse supernovae (i.e. black hole formation). Conversely, I will discuss recent results from full three-dimensional, general-relativistic simulations of core-collapse and the implications for our understanding of the core-collapse supernova mechanism. If time permits, I'll discuss how neutrinos from the next galactic core-collapse supernova can help constrain properties of massive stars.
12/13 PSI - Explorations in Cosmology Lecture 2

Matthew Johnson York University
April 09, 2013

PIRSA:13040063
Cosmology
12/13 PSI - Explorations in Cosmology Lecture 1

Matthew Johnson York University
April 08, 2013

PIRSA:13040062
Cosmology
Time Reborn

Lee Smolin Perimeter Institute for Theoretical Physics
April 03, 2013

PIRSA:13040103
Cosmology
What is time? Is our perception of time passing an illusion which hides a deeper, timeless reality? Or is it real, indeed, the most real aspect of our experience of the world? Einstein said that "the distinction between past, present, and future is only a stubbornly persistent illusion," and many contemporary theorists agree that time emerges from a more fundamental timeless quantum universe. But, in recent cosmological speculation, this timeless picture of nature seems to have reached a dead end, populated by infinite numbers of imagined unobservable universes.

In his talk, Lee Smolin explains why he changed his mind about the nature of time. Like many fellow theorists, he used to believe time is an illusion, but he now embraces the view that time is real and everything else, including the laws of nature, evolves. Drawing from his new book, Time Reborn, Smolin explains how the great unsolved problems in physics and cosmology may be solved by adopting the view of a real time. then he will go beyond physics to explain how our view of time affects how we think of everything from our personal and family lives to how we face major problems such as climate change and economic crisis. In a world in which time is real, the future is open and there is an essential role for human agency and imagination in envisioning and shaping a good future.
Black holes as probes of fundamental physics

Vitor Cardoso Instituto Superior Tecnico - Departamento de Física
April 03, 2013

PIRSA:13040109
Particle Physics

Cosmology
Black holes are the elementary particles of gravity, the final state of sufficiently massive stars and of energetic collisions. With a forty-year long history, black hole physics is a fully-blossomed field which promises to embrace several branches of theoretical physics. Here I review the main developments in highly dynamical black holes with an emphasis on high energy black hole collisions and probes of particle physics via superradiance.
Shake, Rattle and Explode: Short GRBs and the Electromagnetic Counterparts of Gravitational Wave Sources

Edo Berger Harvard University
April 02, 2013

PIRSA:13040081
Cosmology

Strong Gravity
The bimodality of gamma-ray burst (GRB) durations points to distinct progenitor classes for the long- and short-duration GRBs. While the progenitors of long-duration GRBs are now known to be massive stars, the progenitors of short-duration GRBs remain unidentified. In this talk I will discuss the discovery of short GRB afterglow and their host galaxies, detailed studies of their environments from parsec to galactic scales, and studies of their energetics and beaming. Taken together, these observations point to the coalescence of NS-NS/NS-BH binaries as the most likely progenitors. With the upcoming Advanced LIGO/VIRGO gravitational wave detectors it is therefore possible that short GRBs will be the first detected sources, and I will discuss various approaches to making this connection between gravitational wave and electromagnetic sources.
The Effective Field Theory of Large Scale Structures

Enrico Pajer Utrecht University
March 19, 2013

PIRSA:13030110
Cosmology
An analytical understanding of large-scale matter inhomogeneities is an important cornerstone of our cosmological model and helps us interpreting current and future data. The standard approach, namely Eulerian perturbation theory, is unsatisfactory for at least three reasons: there is no clear expansion parameter since the density contrast is not small everywhere; it does not consistently account for deviations at large scales from a perfect pressureless fluid induced by short-scale non-linearities; for generic initial conditions, loop corrections are UV divergent, making predictions cutoff dependent and hence unphysical. I will present the systematic construction of an Effective Field Theory of Large Scale Structures and show that it successfully addresses all of the above issues. The idea is to smooth the density and velocity fields on a scale larger than the non-linear scale. The resulting smoothed fields are then small everywhere and provide a well-defined small parameter for perturbation theory. Smoothing amounts to integrating out the short scales, whose non-linear dynamics is hard to describe analytically. Their effects on the large scales are then determined by the symmetries of the problems. They introduce additional terms in the fluid equations such as an effective pressure, dissipation and stochastic noise. These terms have exactly the right scale dependence to cancel all divergences at one loop, and this should hold at all loops.
I will present a clean example of the renormalization of the theory in an Einstein de Sitter universe with self-similar initial conditions and discuss the relative importance of loop and effective corrections.
Effective field theory approach to quasi-single field inflation

Masahide Yamaguchi Tokyo Institute of Technology
March 12, 2013

PIRSA:13030096
Cosmology
We apply the effective field theory approach to quasi-single field inflation, which contains an additional scalar field with Hubble scale mass other than inflaton. Based on the time-dependent spatial diffeomorphism, which is not broken by the time-dependent background evolution, the most generic action of quasi-single field inflation is constructed up to third order fluctuations. Using the obtained action, the effects of the additional massive scalar field on the primordial curvature perturbations are discussed. In particular, we calculate the power spectrum and discuss the momentum-dependence of three point functions in the squeezed limit for general settings of quasi-single field inflation. Our framework can be also applied to inflation models with heavy particles. We make a qualitative discussion on the effects of heavy particles during inflation and that of sharp turning trajectory in our framework.
12/13 PSI - Cosmology Review Lecture 14

Latham Boyle University of Edinburgh
March 08, 2013

PIRSA:13030045
Cosmology

Title	Speaker(s)	Date	Talk Type	Info link
Large Scale Bayesian Inference in Cosmology	Jens Jasche	2013-04-11	Scientific Series	View details
12/13 PSI - Explorations in Cosmology Lecture 4	Matthew Johnson	2013-04-11	Course	View details
12/13 PSI - Explorations in Cosmology Lecture 3	Matthew Johnson	2013-04-10	Course	View details
The Death Throes of Massive Stars: Supernovae, Black Holes, and Neutrinos	Evan O'Connor	2013-04-09	Scientific Series	View details
12/13 PSI - Explorations in Cosmology Lecture 2	Matthew Johnson	2013-04-09	Course	View details
12/13 PSI - Explorations in Cosmology Lecture 1	Matthew Johnson	2013-04-08	Course	View details
Time Reborn	Lee Smolin	2013-04-03	Public Lectures	View details
Black holes as probes of fundamental physics	Vitor Cardoso	2013-04-03	Scientific Series	View details
Shake, Rattle and Explode: Short GRBs and the Electromagnetic Counterparts of Gravitational Wave Sources	Edo Berger	2013-04-02	Scientific Series	View details
The Effective Field Theory of Large Scale Structures	Enrico Pajer	2013-03-19	Scientific Series	View details
Effective field theory approach to quasi-single field inflation	Masahide Yamaguchi	2013-03-12	Scientific Series	View details
12/13 PSI - Cosmology Review Lecture 14	Latham Boyle	2013-03-08	Course	View details

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