COVID-19 information for PI Residents and Visitors

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Conference Date:
Tuesday, June 14, 2016 (All day) to Friday, June 17, 2016 (All day)
Scientific Areas:
Cosmology

The purpose of this workshop is to discuss and exchange ideas on the most stimulating recent developments in cosmology and fundamental physics. This year, the workshop will focus on four themes: Next Generation Cosmological Probes, Gravitational Wave Astronomy, Fundamental Strong Gravity, and Theoretical Cosmology. We hope that this workshop encourages new ideas and new collaborations among theorists and observers working in cosmology and gravitation. This workshop is the ninth in a series organized jointly by the International Solvay Institutes, APC (Universite Paris VII, Paris) and the Perimeter Institute (Waterloo, Canada). The previous edition was held in Brussels in July, 2015.

Registration for this workshop is now closed.

Sponsorship for this workshop has been provided by:

• Yacine Ali-Haimoud, Johns Hopkins University
• Francois Bouchet, Institut d’Astrophysique de Paris
• Kipp Cannon, Research Center for the Early Universe
• William East, SLAC National Accelerator Laboratory
• Bryan Gaensler, University of Toronto
• Vera Gluscevic, Institute for Advanced Study
• Stephen Green, Perimeter Institute
• Gil Holder, McGill University
• Justin Khoury, University of Pennsylvania
• Jean-Luc Lehners, Max Planck Institute for Gravitational Physics
• Steve Liebling, Long Island University
• Eugene Lim, Kings College London
• Marilena LoVerde, Stony Brook University
• Frans PretoriusPrinceton University
• Leonardo Senatore, SLAC National Accelerator Laboratory
• Jon Sievers, University of KwaZulu-Natal
• Neil Turok, Perimeter Institute
• Nicolas Yunes, Montana State University
• Aaron ZimmermanCanadian Institute for Theoretical Astrophysics

• Yacine Ali-HaimoudJohns Hopkins University
• Cristian Armendariz-Pincon, St. Lawrence University
• Leon Avery, University of Waterloo
• James Bardeen, University of Washington
• Hossein Bazrafshan Moghaddam, McGill University
• Francois Bouchet, Institut d’Astrophysique de Paris
• Latham Boyle, Perimeter Institute
• Alex Buchel, Perimeter Institute
• Kipp Cannon, Research Center for the Early Universe
• Alan Coley, Dalhousie University
• Marina Cortes, Royal Observatory Edinburgh
• William EastSLAC National Accelerator Laboratory
• Solomon Endlich, Stanford University
• Bryan Gaensler, University of Toronto
• Vera Gluscevic, Institute for Advanced Study
• Stephen Green, Perimeter Institute
• Daniel Guariento, Perimeter Institute
• Kurt Hinterbichler, Perimeter Institute
• Renee Hlozek, University of Toronto
• Gil HolderMcGill University
• Mike Hudson, University of Waterloo
• Matthew Johnson, Perimeter Institute & York University
• Mansour Karami, Perimeter Institute
• Justin KhouryUniversity of Pennsylvania
• Darsh KodwaniCanadian Institute for Theoretical Astrophysics
• Peter Komorowski, University of Western Ontario
• Luis Lehner, Perimeter Institute
• Jean-Luc LehnersMax Planck Institute for Gravitational Physics
Andrew Liddle, Royal Observatory Edinburgh
• Steve Liebling, Long Island University
• Eugene LimKings College London
• Marilena LoVerdeStony Brook University
• Andrei Lupu, Vanier College
• Antonino Marciano, Fudan University
• Evan McDonough, McGill University
• Joel Meyers. University of Texas
• John Moffat, Perimeter Institute
• Moritz Muenchmeyer, Institute d'Astrophysique de Paris
• Ali Nayeri, Chapman University
• Elliot Nelson, Perimeter Institute
• Chiamaka Okoli, Perimeter Institute
• Ue-Li PenCanadian Institute for Theoretical Astrophysics
• Ashley Perko, Stanford University
• Frans PretoriusPrinceton University
• Leonardo SenatoreSLAC National Accelerator Laboratory
• Mohamad Shalaby, Perimeter Institute & University of Waterloo
• Yutaka Shikano, Institute for Molecular Science, National Institutes of Natural Sciences
• Jon Sievers, University of KwaZulu-Natal
• Kendrick Smith, Perimeter Institute
• Mark Stuckey, Elizabethtown College
• Alexandra Terrana, Perimeter Institute & York University
• Neil Turok, Perimeter Institute
• Robert Van den Hoogen, St. Francis Xavier University
• Alex van EngelenCanadian Institute for Theoretical Astrophysics
• Nicolas Yunes, Montana State University
• Aaron ZimmermanCanadian Institute for Theoretical Astrophysics
• Nosiphiwo Zwane, Perimeter Institute

Tuesday, June 14, 2016

 Time Event Location 9:00 – 9:30am Registration Reception 9:30 – 9:40am Welcome and Opening Remarks Theater 9:40 – 10:30am Yacine Ali-Haimoud, Johns Hopkins UniversityDark matter phenomenology across cosmic times Theater 10:30 – 11:20am Coffee Break Bistro – 1st Floor 11:30 – 12:00pm Special Announcement Theater 12:00 – 12:50pm Justin Khoury, University of PennsylvaniaA Dark Matter Superfluid Theater 12:50 – 3:00pm Lunch Bistro – 2nd Floor 3:00 – 3:50pm Jean-Luc Lehners, Max Planck Institute for Gravitational PhysicsThe Classicality Puzzle Theater 3:50pm – 4:40pm Leonardo Senatore, SLAC National Accelerator LaboratoryInhomogeneous  Anisotropic Cosmology Theater 4:40 – 5:30pm Vera Gluscevic, Institute for Advanced StudyA new probe of primordial magnetic fields at high redshift Theater

Wednesday, June 15, 2016

 Time Event Location 9:30 – 10:20am Stephen Green, Perimeter InstituteTurbulent gravity in asymptotically AdS spacetimes Theater 10:20 – 10:50am Coffee Break Bistro – 1st Floor 10:50 – 11:40am Aaron Zimmerman, CITABlack hole ringdown and quasinormal modes Theater 11:40 – 12:30pm Frans Pretorius, Princeton UniversityThe Dynamical Strong-field Regime of General Relativity Theater 12:30 – 12:40pm Conference Photo TBA 12:40 – 3:00pm Lunch Bistro – 2nd Floor 3:00 – 3:50pm Nicolas Yunes, Montana State UniversityWhat does the Advanced LIGO detection say about gravity? Theater 3:50pm – 4:40pm Kipp Cannon, Research Center for the Early UniverseTBA Theater 5:30pm onwards Banquet Bistro – 2nd Floor

Thursday, June 16, 2016

 Time Event Location 9:30 – 10:20am William East, SLAC National Accelerator LaboratorySpacetime Dynamics of the Higgs Instability and the Fate of the Early Universe Theater 10:20 – 10:50am Coffee Break Bistro – 1st Floor 10:50 – 11:40am Eugene Lim, Kings College LondonCan inflation really begin with inhomogenous initial conditions? Theater 11:40 – 12:30pm Steve Liebling, Long Island UniversityCompact Objects in the Era of GW Astronomy Theater 12:30 – 3:00pm Lunch Bistro – 2nd Floor 3:00 – 3:50pm Francois Bouchet, Institut d’Astrophysique de ParisLatest cosmological news from the Planck satelitte Project Theater 3:50pm – 4:40pm Gil Holder, McGill UniversityMapping dark matter on the largest and smallest scales Theater

Friday, June 17, 2016

 Time Event Location 9:30 – 10:20am Peter Adshead, University of Illinois at Urbana-ChampaignAsymmetric reheating and chilly dark sectors Theater 10:20 – 10:50am Coffee Break Bistro – 1st Floor 10:50 – 11:40am Marilena LoVerde, Stony Brook UniversityStructure Formation in a nuCDM Universe Theater 11:40 – 12:30pm Jon Sievers, University of KwaZulu-NatalTBA Theater 12:30 – 3:00pm Lunch Bistro – 2nd Floor 1:00 – 2:00pm PI Orchestra Concert Atrium 3:00 – 3:50pm Neil Turok, Perimeter InstituteShocks in the Early Universe Theater 3:50pm – 4:40pm Bryan Gaensler, University of TorontoCosmology and Fundamental Physics with the Square Kilometre Array Theater

Asymmetric reheating and chilly dark sectors

In a broad class of theories, the relic abundance of dark matter is determined by interactions internal to a thermalized dark sector, with no direct involvement of the Standard Model. These theories raise an immediate cosmological question: how was the dark sector initially populated in the early universe? I will discuss one possibility, asymmetric reheating,  which can populate a thermal dark sector that never reaches thermal equilibrium with the SM.

Yacine Ali-Haimoud, Johns Hopkins University

Dark matter phenomenology across cosmic times

The nature of dark matter remains one of the most nagging problems in cosmology. In this talk I will discuss several existing or potential probes of dark matter. I will start with a well known hot dark matter, massive neutrinos, and discuss their effect on large-scale structure in the non-linear regime. I will then talk about the effect of dark matter interactions with standard model particles on the spectrum of the CMB and on 21cm fluctuations. I will conclude by discussing whether LIGO could have detected primordial-black-hole dark matter.

Francois Bouchet, Institut d’Astrophysique de Paris

Latest cosmological news from the Planck satelitte Project

The Planck collaboration is working towards a "legacy release" by the end of 2016 which will mark the end of the formal collaboration we set up back in the previous century. To this end, we keep improving further  our control on the potential level of residual systematics in the data and in accounting for these uncertainties in the final cosmological results to further enhance the robustness and precision of the constraints posed by Planck. For instance, we announced in May an improved likelihood analysis using detailed end-to-end simulation as well as an improved constraint on the reionisation optical depth by using for the first time the E-mode polarisation data from the HFI instrument. This determination fully reconciles the CMB results with other astrophysical measurements of reionization from sources at high redshift. It also gives constraints on the level of reionization at redshifts beyond that of the most distant sources (z > 10). I will further give some perspectives on what is coming next.

William East, SLAC National Accelerator Laboratory

Spacetime Dynamics of the Higgs Instability and the Fate of the Early Universe

A remarkable feature of the Standard Model is that it predicts that, in the absence of new physics, the Higgs field should become unstable at large energies.  Though the electroweak vacuum should currently be metastable on timescales that are long compared to the age of the Universe, during an inflationary period, quantum fluctuations could have driven the development of regions of true vacuum at negative energy densities.  I will discuss the evolution and spacetime dynamics of unstable Higgs fluctuations, illustrating how they can halt inflation in the regions they develop, and give rise to crunching regions and black holes with unusual properties. By combining this picture from general relativity with a detailed treatment of the stochastic development of such unstable Higgs fluctuations, bounds can be placed on the inflationary energy scale based on the existence of our current Universe.

Bryan Gaensler, University of Toronto

Cosmology and Fundamental Physics with the Square Kilometre Array

The Square Kilometre Array (SKA) is a next-generation radio telescope scheduled to commence construction in 2018. The SKA will be one of a small set of billion-dollar facilities that collectively span the electromagnetic spectrum, and will be an order of magnitude more sensitive than any other radio facility. The SKA's extraordinary survey capacity will allow it to map the distribution of galaxies and large-scale structure over an unprecedented cosmic volume, providing superb probes of dark matter, dark energy, neutrino physics, magnetogenesis, non-gaussianity and inflation. In addition, pulsar timing with the SKA will provide precision tests of general relativity in the strong field regime, and should allow us to detect gravitational radiation produced by merging supermassive black holes. In this talk, I will provide an overview of the capabilities and science goals for the SKA, highlighting its unique potential for advancing our understanding of cosmology and fundamental physics.

Vera Gluscevic, Institute for Advanced Study

A new probe of primordial magnetic fields at high redshift

I will present a novel method for probing extremely weak large-scale magnetic fields in the intergalactic medium prior to the epoch of reionization. This method relies on the effect of spin alignment of hydrogen atoms in a cosmological setting, and on the effect of magnetic precession of the atoms on the statistics of the 21–cm brightness–temperature fluctuations. It is intrinsically sensitive to magnetic fields weaker than 10^{-19} Gauss in physical units, and thus has a potential to reach many orders of magnitude below the current constraints on primordial magnetic fields. I will discuss the physical mechanism, lay out the estimator formalism that enables searches with future 21-cm tomographic surveys, and present forecasts for detecting magnetic fields in the high-redshift universe using this method.

Stephen Green, Perimeter Institute

Turbulent gravity in asymptotically AdS spacetimes

Dynamics in asymptotically anti-de Sitter spacetimes with reflecting boundary conditions are characterized by reduced dissipation as compared to asymptotically flat spacetimes. Such spacetimes, thus, represent opportunities to study nonlinear gravitational interactions that would otherwise be quickly damped away. I will discuss two background spacetimes---large AdS black branes in d=4, and pure AdS---where small perturbations display turbulent behavior and energy cascades driven by nonlinear interactions. In each case, the presence of an unexpected conserved quantity---a gravitational "enstrophy" around the AdS black brane, and a "particle number" for pure AdS perturbations---significantly affects the energy flow direction throughout the cascade, and drives energy to longer distance scales. I will comment on implications for fundamental general relativity questions such as cosmic censorship, and potential for turbulence beyond AdS.

Gil Holder, McGill University

Mapping dark matter on the largest and smallest scales

Using lensing of the CMB we can make maps of the dark matter distribution on the largest cosmological scales, perhaps allowing new insights into gravity, particle physics, and cosmology. With high-resolution maps of distant star-forming galaxies we can map dark matter on small scales within individual galaxies, measuring the small-scale clumping properties of dark matter.

Justin Khoury, University of Pennsylvania

A Dark Matter Superfluid

Jean-Luc Lehners, Max Planck Institute for Gravitational Physics

The Classicality Puzzle

Why was the early universe classical? Along with the big bang singularity problem and the flatness, horizon and inhomogeneity puzzles, this is one of the big unexplained features of the hot big bang scenario. In this talk I will discuss how inflation and ekpyrosis, which have mainly been considered as models that can address some of the other puzzles, can both drive the early universe towards classicality. The remarkable aspect is that classicality is achieved via the intrinsic dynamics of inflation and ekpyrosis, without invoking decoherence.

Steve Liebling, Long Island University

Compact Objects in the Era of GW Astronomy

I will discuss recent work modeling compact objects in an effort to extract scientific understanding from multi-messenger observations.

Eugene Lim, Kings College London

Can inflation really begin with inhomogenous initial conditions?

Marilena LoVerde, Stony Brook University

Structure Formation in a nuCDM Universe

Cosmic background neutrinos are nearly as abundant as cosmic microwave background photons, but their mass, which determines the strength of their gravitational clustering, is unknown. Neutrino oscillation data gives a strict lower limit on neutrino mass, while cosmological datasets provide the most stringent upper limit. Even if the neutrino masses are the minimum required by oscillation data, their gravitational effects on structure formation will nevertheless be detectable in — and in fact required to explain —  data within the next decade. I will discuss the physical effects of the cosmic neutrino background on structure formation and present a new signature that may be used to measure neutrino mass with large galaxy surveys.

Frans Pretorius, Princeton University

The Dynamical Strong-field Regime of General Relativity

In this talk I will discuss some of the consequences for our understanding of strong-field gravity that can be gleaned from the recent detection of gravitational waves by the LIGO/Virgo collaboration.

The event heard, GW150914, is consistent with the emission of gravitational waves from the late inspiral, merger and ringdown of two heavy stellar mass black holes. This has given us the first quantifiable pieces of evidence that the dynamics and properties of colliding black holes are governed by general relativity. At present certain exotic compact object alternatives to black holes within general relativity, such as boson stars or gravastars, cannot yet be ruled out due to lack of concrete predictions of the merger regime in such scenarios. However, I will argue that even if the progenitors of GW150914 where composed of such exotic matter, the gravitational wave data strongly suggests collision lead to the prompt formation of a Kerr black hole.

Leonardo Senatore, SLAC National Accelerator Laboratory

Inhomogeneous  Anisotropic Cosmology

In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate.  If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch.   A similar statement holds for homogeneous but anisotropic (Bianchi) universes.  Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with flat'' (including toroidal) and open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations  and/or the formation of black holes.   Because the set of 3-manifold topologies is countable, a single integer  determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are flat'' or open''.    Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with flat'' or open''  topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves.  Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.

Neil Turok, Perimeter Institute

Shocks in the Early Universe

Nicolas Yunes, Montana State University

The gravitational-wave observation GW150914 by Advanced LIGO provides the first opportunity to learn about theoretical physics mechanisms that may be present in the extreme gravity environment of coalescing binary black holes. The LIGO collaboration verified that this observation is consistent with Einstein's theory of General Relativity, constraining the presence of parametric anomalies in the signal. In this talk, I will discuss the plethora of additional inferences about gravity that can be drawn from the absence of such anomalies in the LIGO observation. I will focus and classify these inferences into those that inform us about the generation of gravitational waves (e.g. the activation of scalar fields, black hole graviton leakage into extra dimensions, the variability of Newton's constant, the breakage of Lorentz invariance and parity invariance), and the propagation of gravitational waves (e.g. the speed of gravity and the existence of large extra dimensions). I will conclude with a discussion of how these inferences may inform us about the models of modified gravity in cosmology.

Aaron Zimmerman, CITA

Black hole ringdown and quasinormal modes

The first detection of gravitational waves came with an unexpected windfall: a clear signal from the merger of two black holes into a final, spinning black hole. General Relativity predicts that following merger, the final black hole relaxes by emitting radiation in a characteristic spectrum of decaying modes. I will discuss these quasinormal modes'' and what can be learned from them, as well as the black hole ringdown observed in GW150914. I will also explore the exotic side of ringdown, including the modes of nearly extremal black holes, and a tool for understanding the ringdown of black holes which differ from the standard Kerr solution.

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Scientific Organziers:

• Matthew Johnson, Perimeter Institute & York University
• Kendrick Smith, Perimeter Institute