# Cosmological Frontiers in Fundamental Physics 2013

Conference Date:
Monday, July 8, 2013 (All day) to Thursday, July 11, 2013 (All day)
Scientific Areas:
Cosmology

Support for this conference is provided by The Templeton Frontiers Program.

The purpose of this informal workshop is to discuss and exchange ideas on recent developments at the interface of modern cosmology and fundamental physics. This workshop is the seventh in a series organized jointly by the International Solvay Institutes, APC (Université Paris VII, Paris) and the Perimeter Institute (Waterloo, Canada).  The previous edition was held in Brussels in May, 2012.

Sponsorship for this conference has been provided by:

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• James Bardeen, University of Washington
• Richard Bond, University of Toronto
• Martin BucherLaboratoire de Physique Theorique d'Orsay
• Ben Craps, VUB & Solvay Institutes
• Neal DalalUniversity of Illinois at Urbana-Champaign
• Ben FreivogelUniversiteit van Amsterdam
• Daniel Green, Stanford University
• Fawad Hassan, Stockholm University
• Marc Henneaux, Solvay Institute
• Kurt Hinterbichler, Perimeter Institute
• Renee Hlozek, Princeton University
• David Langlois, APC Paris
• Paul McFadden, Perimeter Institute
• Sean McWilliams, Princeton University
• Shinji Mukohyama, Kavli IPMU
• Alberto Nicolis, Columbia University
• Hiranya Peiris, University College London
• Ue-Li Pen, CITA
• Suvrat RajuInternational Centre for Theoretical Sciences
• Claudia de Rham, Case Western Reserve University
• Kris Sigurdson, University of British Columbia
• Kendrick Smith, Perimeter Institute & Princeton University
• Neil Turok, Perimeter Institute
• Tanmay Vachaspati, Arizona State University
• Erick Weinberg, Columbia University
• Niayesh Afshordi, Perimeter Institute
• Tibra Ali, Perimeter Institute
• Melinda Andrews, University of Pennsylvania
• Latham Boyle, Perimeter Institute
• Jonathan Braden, CITA
• Nora BretonCentro de Investigación y de Estudios Avanzados
• Cliff Burgess, Perimeter Institute & McMaster University
• Vladimir Buzek, John Templeton Foundation
• Freddy Cachazo, Perimeter Institute
• Liam Connor, CITA
• Guido D'Amico, New York University
• Ema Dimastrgiovanni, UMN
• Francis Duplessis, McGill University
• Adrienne Erickcek, CITA
• Matteo Fasiello, Case Western Reserve University
• Anthony Fradette, University of Victoria
• Ghazal Geshnizjani, Perimeter Institute
• Steffen Gielen, Perimeter Institute
• Garrett Goon, University of Pennsylvania
• Pierre Gratia, University of Chicago
• Amir Hajian, CITA
• Shajid HaqueUniversity of the Witwatersrand
• Alireza Hojjati, Institute for the Early Universe
• Bart Horn, Columbia University
• Luca Iliesiu, Princeton University
• Shenglin Jing, University of Toronto
• Matt Johnson, Perimeter Institute
• Ronald KashubaLos Alamos National Laboratory
• Nima Khosravi, African Institute for Mathematical Sciences
• Takeshi Kobayashi, Perimeter Institute
• Anna Kostouki, Perimeter Institute
• Gordon Krnjaic, Perimeter Institute
• David Kubizniak, Perimeter Institute
• Keith Lee, Perimeter Institute
• Tonjuan Lin, University of Chicago
• Robert Mann, Perimeter Institute & University of Waterloo
• David Marsh, Perimeter Institute
• Mercedes Martin-Benito, Perimeter Institute
• Flavio Mercati, Perimeter Institute
• Joel Meyers, CITA
• Audrey Mithani, Tufts University
• John Moffat, Perimeter Institute
• Rob Myers, Perimeter Institute
• Riccardo Penco, Columbia University
• Andrea Petri, Columbia University
• Sohrab Rahvar, Perimeter Institute
• Dan Reynolds, York University
• Mohamad Shalaby, Perimeter Institute
• Brian Shuve, Perimeter Institute
• Lee Smolin, Perimeter Institute
• James Stokes, University of Pennsylvania
• Alexandra Terrana, Perimeter Institute
• Andrew Tolley, Case Western Reserve University
• Dan Wohns, Perimeter Institute
• I-Sheng Yang, University of Amsterdam

Monday, July 8, 2013

 Time Event Location 9:00-9:30am Registration Reception 9:30-9:35am Welcome and Opening Remarks Theater 9:35-10:20am Richard  Bond, University of Toronto Intermittent non-Gaussianity & Anomalies: rare patchy subdominants from Modulated Heating, Bubble Collisions & Oscillons Theater 10:20-10:50am Coffee Break Bistro 10:50-11:40am Paul McFadden, Perimeter Institute Precision Holographic Cosmology Theater 11:40-12:30pm Shinji Mukohyama, Kavli IPMU Massive gravity and cosmology Theater 12:30-3:00pm Lunch Bistro - 2nd Floor 3:00-3:50pm Claudia de Rham, Case Western Reserve University TBA Theater 3:50-4:40pm Erick Weinberg, Columbia University Tumbling through a landscape Theater 4:40-5:30pm Kendrick Smith, Perimeter Institute & Princeton University Primordial non-Gaussianity in the CMB and large-scale structure Theater

Tuesday, July 9, 2013

 Time Event Location 9:00-9:50am Kris Sigurdson, University of British Columbia    Cosmological Limits on Neutrino-Neutrino Scattering  and Particle Physics in the Early Universe Theater 9:50-10:40am Alberto Nicolis, Columbia University Solid Inflation Theater 10:40-11:10am Coffee Break Bistro 11:10-12:00pm Fawad Hassan, Stockholm University Bimetric theory, Conformal Gravity and Partial Masslessness Theater 12:00-12:50pm Marc Henneaux, Solvay Institute Remarks on Gravitational Duality Theater 12:50-3:00pm Lunch Bistro - 2nd Floor 3:00-3:50pm Tanmay Vachaspati, Arizona State University Cosmological Magnetic Fields Theater 3:50-4:40pm Neil Turok, Perimeter Institute Resolution of Cosmic Singularities and Bounces Theater 4:40-5:30pm David Langlois, APC Paris A unifying approach to dark energy models Theater 5:30pm BBQ Bistro

Wednesday, July 10, 2013

 Time Event Location 9:30-10:20am Ue-Li Pen, CITA 21cm cosmology Theater 10:20-10:30am Conference Photo TBA 10:30-10:50am Coffee Break Bistro 10:50-11:40am Martin Bucher, Laboratoire de Physique Theorique d'Orsay Planck and beyond Theater 11:40-12:30pm Hiranya Peiris, University College London Testing inflation with combined power - and bispectrum Theater 12:30-3:00pm Lunch Bistro - 2nd Floor 3:00-3:50pm James Bardeen, University of Washington Black hole evaporation and unitarity: a semi-classical resolution? Theater 3:50-4:40pm Suvrat Raju, International Centre for Theoretical Sciences The Information Paradox and an an Infalling Observer in AdS/CFT Theater 4:40-5:30pm Renee Hlozek, Princeton University  The Microwave Background on small scales: Cosmological parameters from three seasons of data of the Atacama Cosmology Telescope (ACT). Theater

Thursday, July 11, 2012

 Time Event Location 9:30-10:20am Ben Freivogel, Universiteit van Amsterdam TBA Theater 10:20-10:50am Coffee Break Bistro 10:50-11:40am Sean McWilliams, Princeton University Gravitational waves and stalled satellites from massive galaxy mergers at z < 1 Theater 11:40-12:30pm Neal Dalal, University of Illinois at Urbana-Champaign Probing small-scale structure with dusty galaxies in the CMB Theater 12:30-3:00pm Lunch Bistro - 2nd Floor 3:00-3:50pm Daniel Green, Stanford University How much information is there in large scale structure? Theater 3:50-4:40pm Ben Craps, VUB & Solvay InstitutesStrings in Compact Cosmological Spaces Theater 4:40-5:30pm Kurt Hinterbichler, Perimeter Institute Cosmological Consistency Relations as Ward Identities Theater

James Bardeen, University of Washington Black hole evaporation and unitarity: a semi-classical resolution? I explore the possibility that semi-classical back-reaction, due to the partners of the Hawking radiation quanta accumulating over the time for the black hole to lose about one half of its mass (the Page time), might cause the trapped surfaces to disappear, permitting unitary evolution without any cloning of quantum information. Richard Bond, University of Toronto Intermittent non-Gaussianity & Anomalies: rare patchy subdominants from Modulated Heating, Bubble Collisions & Oscillons Martin BucherLaboratoire de Physique Theorique d'Orsay  Planck and beyond After reviewing some of the highlights of the implications of the Planck results for cosmic  inflation (presentation to be coordinated with Hiranya Peiris), I will discuss some recent developments regarding future searches for B modes and other new science resulting from an ultra-precise characterization of the microwave and far-infrared sky in polarization. I will outline ideas for a recently proposed large-class European Space Agency mission called PRISM. Ben Craps, VUB & Solvay Institutes Strings in Compact Cosmological Spaces A formalism is proposed for perturbative string theory in spacetimes with totally compact space (and non-compact time). Neal Dalal, University of Illinois at Urbana-Champaign Probing small-scale structure with dusty galaxies in the CMB Daniel Green, Stanford University How much information is there in large scale structure? Large scale structure contains vastly more Fourier modes than the CMB, and is therefore a promising arena for studying the early universe.  One obstacle to using these modes is the non-linearity of structure formation. The amount of weakly coupled information available is therefore very sensitive to scale at which non-linear effects become important and simulations become necessary.  Using effective field theory techniques, I will present evidence that the perturbative description of dark matter is much better behaved than previously thought.  I will discuss the implications for improving constraints on non-gaussian initial conditions. Fawad Hassan, Stockholm University Bimetric theory, Conformal Gravity and Partial Masslessness Ghost-free bimetric theories can be used to describe  gravitational interactions in the presence of an extra neutral massive spin-2 field that can modify gravity in non-trivial ways. They also provide a natural framework for a possible non-linear extension of partially masslessness known to arise in linear Fierz-Pauli theory. This talk will describe bimetric theories and a procedure that identifies a unique bimetric action as a candidate for a nonlinear partially massless theory. We then show that in the low curvature limit, the candidate partial massless theory is related to Conformal Gravity. Marc Henneaux, Solvay Institute Remarks on Gravitational Duality Kurt Hinterbichler, Perimeter Institute Cosmological Consistency Relations as Ward Identities Renee Hlozek, Princeton Unviersity The Microwave Background on small scales: Cosmological parameters from three seasons of data of the Atacama Cosmology Telescope (ACT).

The Atacama Cosmology Telescope (ACT) has mapped the microwave sky to
arcminute scales. We present constraints on parameters from the observations at 148 and 217 GHz respectively by ACT from three years of observations.  Efficient map-making and spectrum-estimation techniques allow us to probe the acoustic peaks deep into the damping tail, and allow for confirmation of the concordance model, and tests for deviations from the standard cosmological picture. We fit a model of primary cosmological and secondary foreground parameters to the dataset, including contributions from both the thermal and kinetic Sunyaev-Zel'dovich effect, Poisson distributed and correlated infrared sources, radio sources and a term modeling the correlation between the thermal SZ effect and the Cosmic Infrared Background. We will describe the multi-frequency likelihood for the ACT data, and present constraints on a variety of cosmological parameters using this
complete dataset, and put these results in context with the recent results from the Planck satellite.

David Langlois, APC Paris

A unifying approach to dark energy models

This talk  will present  an effective  description of  single field dark energy/modified gravity models, which encompasses most  existing proposals.  The starting point is a generic Lagrangian expressed in terms of the lapse  and of the extrinsic and intrinsic curvature tensors of the uniform scalar field hypersurfaces. By expanding this Lagrangian up to quadratic order, one can describe the homogeneous background and the dynamics of  linear perturbations. In particular, one can identify seven Lagrangian operators that lead  to  equations of motion containing at most second order derivatives, the time-dependent coefficients  of three of these operators characterizing  the background evolution. I will illustrate this approach with  Horndeski's---or generalized Galileon---theories. Finally,  I will discuss  the link between this effective approach and  observations.

Paul McFadden, Perimeter Institute

Precision Holographic Cosmology

We discuss holography for cosmology, focusing on a class of slow-roll inflationary spacetimes that are holographically dual to a perturbative RG flow between two nearby CFTs.   The cosmological power spectrum and non-Gaussianities may be calculated directly from the dual QFT using conformal perturbation theory, even when the dual QFT is strongly coupled.  Holography thus offers new methods for computing cosmological observables.  To illustrate, we show how to recover the power spectrum to second order in slow roll.

Sean McWilliams, Princeton University

Gravitational waves and stalled satellites from massive galaxy mergers at z < 1

Pulsar timing arrays (PTAs), which are currently operating around the world and achieving remarkable sensitivities in the ~1--‐100 nHz band, will observe supermassive black holes (SMBHs) at redshifts z < ~1. Until now, all estimates of the anticipated signal strength of these sources have relied primarily on simulations to predict the relevant merger rates. I will present results from a completely new approach, which combines observational data and a fully self--‐consistent numerical evolution of the galaxy mass function. This method, which we will argue is superior to past estimates in several key ways, predicts a merger rate for massive galaxies that is ~10 times larger than that implied by previous calculations. I will explain why previous methods applied to this problem may systematically underestimate this merger rate, and one way in which our method may overestimate the rate, so that our approach has complementary systematic uncertainties in the worst case, and is an overall improvement in the best case. Finally, I will show that the new rate implies a range of possible signal strengths that is already in mild tension with PTA observations, with our model predicting a detection at the 95% confidence level as early as 2016. This could make PTAs the first instruments to directly detect gravitational waves, and will provide unprecedented information about the dynamics of merging galaxies, and merging bulges and supermassive black holes within those galaxies.

Shinji Mukohyama, Kavli IPMU

Massive gravity and cosmology

Alberto Nicolis, Columbia University

Solid Inflation

I will describe a cosmological model where primordial inflation is driven by a 'solid', defined as a system of three derivatively coupled scalar fields obeying certain symmetries and spontaneously breaking a certain subgroup of these. The symmetry breaking pattern differs drastically from that of standard inflationary models: time translations are unbroken. This prevents our model from fitting into the standard effective field theory description of adiabatic perturbations, with crucial consequences for the dynamics of cosmological perturbations. Most notably, non-gaussianities in the curvature perturbations are unusually large, with f_NL ~ 1/(\epsilon.c_s^2), and have a novel shape: peaked in the squeezed limit, with anisotropic dependence on how the limit is approached. Other unusual features include the absence of adiabatic fluctuation modes during inflation---which does not impair their presence and near scale-invariance after inflation---and a slightly blue tilt for the tensor modes.

Hiranya Peiris, London's Global University

Testing inflation with  combined power- and bispectrum

Ue-Li Pen, CITA

21cm cosmology

I will overview the progress of 21cm cosmology, with emphasis on intensity mapping.  Current and future experiments have the potential for precision measurements of dark energy, neutrino mass, and gravitational waves.

Suvrat RajuInternational Centre for Theoretical Sciences

The Information Paradox and an an Infalling Observer in AdS/CFT        Kris Sigurdson, University of British Columbia Cosmological Limits on Neutrino-Neutrino Scattering and Particle Physics in the Early Universe In the standard model neutrinos are assumed to have streamed across the Universe since they last scattered at the weak decoupling epoch when the temperature of the standard-model plasma was ~MeV. The shear stress of free-streaming neutrinos imprints itself gravitationally on the Cosmic Microwave Background (CMB) and makes the CMB a sensitive probe of neutrino scattering. Yet, the presence of nonstandard physics in the neutrino sector may alter this standard chronology and delay neutrino free-streaming until a much later epoch. We will discuss how observations of the CMB can be used to constrain the strength of neutrino self-interactions G_eff and put limits on new physics in the neutrino sector from the early Universe. Key measurements of the CMB at large multipoles made by the Planck satellite and high-l experiments are critical for probing this physics. Within the context of conventional LambdaCDM parameters cosmological data are compatible with G_eff < 1/(56 MeV)^2 and neutrino free-streaming might be delayed until their temperature has cooled to as low as ~25 eV. Intriguingly, we also find an alternative cosmology compatible with cosmological data in which neutrinos scatter off each other until z~10^4 with a preferred interaction strength in a narrow region around G_eff = 1/(10 MeV)^2. This distinct self-interacting neutrino cosmology is characterized by somewhat lower values of both the scalar spectral index and the amplitude of primordial fluctuations. We phrase our discussion in terms of a specific scenario in which a late onset of neutrino free-streaming could occur, but in fact our constraints on the neutrino visibility function are very general.  Kendrick Smith, Perimeter Institute & Princeton University
Primordial non-Gaussianity in the CMB and large-scale structure

Neil Turok, Perimeter Institute

Resolution of Cosmic Singularities and Bounces

The AdS/CFT correspondence provides new insights and tools to answer previously inaccessible questions in quantum gravity. Among the most interesting is whether it is possible to describe a cosmological "bounce" in a mathematically complete and consistent way. In the talk, I'll discuss joint work with M. Smolkin, developing the dual description of the simplest possible 4d M-theory cosmology in the stringy regime, employing the full quantum dynamics of its dual CFT. I'll also present evidence that the description extends to the Einstein-gravity regime.

Tanmay Vachaspati, Arizona State University

Cosmological Magnetic Fields

Erick Weinberg, Columbia University

Tumbling through a landscape

## Massive gravity and cosmology

Monday Jul 08, 2013
Speaker(s):

## Precision Holographic Cosmology

Monday Jul 08, 2013
Speaker(s):

We discuss holography for cosmology, focusing on a class of slow-roll inflationary spacetimes that are holographically dual to a perturbative RG flow between two nearby CFTs.   The cosmological power spectrum and non-Gaussianities may be calculated directly from the dual QFT using conformal perturbation theory, even when the dual QFT is strongly coupled.  Holography thus offers new methods for computing cosmological observables.  To illustrate, we show how to recover the power spectrum to second order in slow roll.

## Intermittent non-Gaussianity & Anomalies: rare patchy subdominants from Modulated Heating, Bubble Collisions & Oscillons

Monday Jul 08, 2013
Speaker(s):

## Opening Remarks

Monday Jul 08, 2013
Speaker(s):

## Organizers

• Latham Boyle, Perimeter Institute
• Ben Craps, VUB & Solvay Institutes
• Thomas Hertog, KU Leuven
• Matthew Johnson, Perimeter Institute
• Kendrick Smith, Perimeter Institute & Princeton University