# Cosmological Frontiers in Fundamental Physics 2019

COVID-19 information for researchers and visitors

Conference Date:
Tuesday, September 3, 2019 (All day) to Friday, September 6, 2019 (All day)
Scientific Areas:
Cosmology
Particle Physics
Strong Gravity

The workshops focuses on novel frontiers in observational cosmology and astrophysics and how they shed light fundamental questions in understanding the universe.

Registration for this event is now closed.

Sponsorship for this event has provided by:

• Damiano Anselmi, University of Pisa
• James Bardeen, University of Washington
• Brando Bellazzini,  Institute de Physique Theorique of CEA
• Latham Boyle, Perimeter Institute
• Avery Broderick, Perimeter Institute
• George Efstathiou, University of Cambridge
• Bob Holdom, University of Toronto
• Mariangela Lisanti, Princeton University
• Moritz Munchmeyer, Perimeter Institute
• Samaya Nissanke, University of Amsterdam
• Francesco Nitti, Astroparticle and Cosmology Laboratory
• Masamune Oguri, Kavli Institute
• Ue-Li Pen, Canadian Institute for Theoretical Astrophysics
• Maxim Pospelov, Perimeter Institute & University of Victoria
• Adam Riess, Space Telescope Science institute
• Neelima Sehgal, Stony Brook University
• Kendrick Smith, Perimeter Institute
• Gerard 't Hooft, Utrecht University
• Chris Tully, Princeton University
• Michael Chapman, University of Waterloo
• Nick De Marchi, University of Waterloo
• William East, Perimeter Institute
• Mike Hudson, University of Waterloo
• Xinyu Li, Perimeter Institute & CITA
• Shuwei Liu, Perimeter Institute
• Elena Massara, University of Waterloo
• John Moffat, Perimeter Institute
• Faizan Mohammad, Perimeter Institute & University of Waterloo
• Emil Mottola, Los Alamos National Laboratory
• Makoto Narita, National Institute of Technology, Okinawa College
• Zhen Pan, Perimeter Institute
• Will Percival, Perimeter Institute & University of Waterloo
• Masoud Rafiei-Ravandi, Perimeter Institute
• Mary Reid, Reid Publishing
• Shan-Ming Ruan, Perimeter Institute
• Laura Sberna, Perimeter Institute
• Benafsheh Shiralilou, University of Amsterdam
• Barak Shoshany, Perimeter Institute
• Qingwen Wang, Perimeter Institute
• Alexander Woodfinden, University of Waterloo

Tuesday, September 3, 2019

 Time Event Location 9:00 – 9:25am Registration Reception 9:25 - 9:30am Latham Boyle, Perimeter InstituteWelcome and Opening Remarks Bob Room 9:30 – 10:15am Latham Boyle, Perimeter Institute  CPT-Symmetric Universe Bob Room 10:15 – 10:45am Coffee Break Bistro – 1st Floor 10:45 – 11:30am Francesco Nitti, Astroparticle and Cosmology LaboratoryBrane cosmology and the self-tuning of the cosmological constant Bob Room 11:30 – 12:15pm Maxim Pospelov, Perimeter Institute & University of VictoriaNew Physics in the Rayleigh-Jeans tale of the CMBand cosmic 21cm signal Bob Room 12:15 – 2:00pm Lunch Bistro – 2nd Floor 2:00 – 2:45pm Masamune Oguri, Kavli InstituteGravitational waves in the inhomogeneous Universe Bob Room 2:45 – 3:30pm Brando Bellazzini, Institute de Physique Theorique of CEAWeak Gravity Conjecture from Amplitudes’ Positivity Bob Room 3:30 – 4:00pm Coffee Break Bistro – 1st Floor 4:00 – 5:00pm Discussions (led by Elias Kiritsis):Where in the Cosmos should we look for novel physics? Bob Room

Wednesday, September 4, 2019

 Time Event Location 9:30 – 10:15am Samaya Nissanke, University of AmsterdamGravitational wave standard sirens Bob Room 10:15 – 10:45am Coffee Break Bistro – 1st Floor 10:45 – 11:30am Ue-Li Pen, CITACosmology and fundamental physics with FRBs Bob Room 11:30 – 12:15pm Kendrick Smith, Perimeter InstituteCHIME: The Canadian Hydrogen Intensity Mapping Experiment Bob Room 12:15 – 2:00pm Lunch Bistro – 2nd Floor 2:00 – 3:00pm ColloquiumAdam Riess, Space Telescope Science instituteThe Present Expansion rate of the Universe, Evidence of New Physics? Theater 3:00 – 3:30pm Coffee Break Bistro – 1st Floor 3:30 – 4:15pm George Efstathiou, University of CambridgeThe Planck Legacy: Inflation and the Origin of Structure in the Universe Bob Room 4:15 – 5:00pm Discussions (led by Lena Funcke):Do cosmic tensions point to novel physics? Bob Room

Thursday, September 5, 2019

 Time Event Location 9:30 – 10:15am Avery Broderick, Perimeter Institute & University of WaterlooFirst Science Results from the EHT Bob Room 10:15 – 10:45am Coffee Break Bistro – 1st Floor 10:45 – 11:30am Gerard 't Hooft, Utrecht UniversityThe antipodal identification as a new boundary condition on the horizon, and how it comes about Bob Room 11:30 – 12:15pm James Bardeen, University of WashingtonNonsingular transition from an evaporating black hole to a white hole Bob Room 12:15 – 2:00pm Lunch Bistro – 2nd Floor 2:00 – 2:45pm Damiano Anselmi, University of PisaQuantum gravity from fakeons Bob Room 2:45 – 3:30pm Bob Holdom, University of TorontoNot quite black holes at LIGO Bob Room 3:30 – 4:00pm Coffee Break Bistro – 1st Floor 4:00 – 5:00pm Discussions (led by Emil Mottola):Is there novel physics at the black hole horizon? Bob Room 6:00 – 8:00pm Banquet Bistro – 2nd Floor

Friday, September 6, 2019

 Time Event Location 9:30 – 10:15am Mariangela Lisanti, Princeton UniversityDiscovering the Goddess of the Night with Machine Learning Bob Room 10:15 – 10:45am Coffee Break Bistro – 1st Floor 10:45 – 11:30am Neelima Sehgal, Stony Brook UniversityCMB-HD: Probing Dark Matter Particle Properties with Ultra-High-Resolution CMB Lensing Bob Room 11:30 – 12:15pm Moritz Munchmeyer, Perimeter InstitutekSZ tomography and its applications to cosmology Bob Room 12:15 – 2:00pm Lunch Bistro – 2nd Floor 2:00 – 2:45pm Chris Tully, Princeton UniversityCNB Detection and Neutrino Mass Measurement with PTOLEMY Bob Room 2:45 – 3:30pm Wrap-up by Niayesh Afshordi Bob Room

Damiano Anselmi, Università di Pisa

Quantum gravity from fakeons

A new quantization prescription is able to endow quantum field theory with a new type of “particle”, the fakeon (fake particle), which mediates interactions, but cannot be observed. A massive fakeon of spin2 (together with a scalar field) allows us to build a theory of quantum gravity that is both renormalizable and unitary, and basically unique. After presenting the general properties of this theory, I discuss its classical limit, which carries important remnants of the fakeon quantization prescription. I also discuss the implications for cosmology and the possibility that the Higgs boson might be a fakeon.

James Bardeen, University of Washington

Nonsingular transition from an evaporating black hole to a white hole

A "quasi-classical" picture of the transition from an evaporating black hole to a white hole is described, which is based on a resolution of the   Schwarzschild singularity suggested by loop quantum gravity.  All quantum information trapped by the black hole is eventually released from the white hole, without any Cauchy horizons, consistent with unitarity.  The effective stress-energy tensor suggests that inflow of negative energy associated with Hawking "partners" in the interior of the black hole becomes, at least initially, an outflow of negative energy from the white hole.  Alternative scenarios for the further evolution of the white hole and their implications will be discussed.

Brando Bellazzini, Institute de Physique Theorique of CEA

Weak Gravity Conjecture From Amplitudes’ Positivity

I will show how to derive new positivity bounds for scattering amplitudes in theories with a massless graviton in the spectrum in four spacetime dimensions. The bounds imply that extremal black holes are self-repulsive, M/|Q|<1 once higher dimensional operators are taken into account, and that they are unstable to decay to smaller extremal black holes, hence providing an S-matrix proof of the weak gravity conjecture.

Latham Boyle, Perimeter Institute

CPT-Symmetric Universe

I will introduce our recent proposal that the state of the universe does *not* spontaneously violate CPT.  Instead, the universe after the big bang is the CPT image of the universe before it, both classically and quantum mechanically.  The pre- and post-bang epochs comprise a universe/anti-universe pair, emerging from nothing directly into a hot, radiation-dominated era.  CPT symmetry selects the QFT vacuum state on such a spacetime, providing a new interpretation of the cosmological baryon asymmetry, as well as a particularly economical explanation for the cosmological dark matter. Requiring only the standard three-generation model of particle physics (with right-handed neutrinos), a Z_2 symmetry suffices to render one of the right-handed neutrinos stable. We calculate its abundance from first principles: matching the observed dark matter density requires its mass to be 4.8 x 10^{8} GeV.  Several other testable predictions immediately follow: e.g. (i) the lightest neutrino is massless; (ii) neutrinoless double beta decay occurs at a specific rate; and (iii) there are no primordial long-wavelength gravitational waves.  The proposal also has interesting things to say about the strong CP problem, the observed electrodynamic arrow of time, cosmological boundary conditions, and the wave-function of the universe. (Based on arXiv:1803.08928, arXiv:1803.08930, and forthcoming work.)

Bob Holdom, University of Toronto

Not quite black holes at LIGO

The Einstein action has made us very accustomed to black holes and their “no drama” event horizons. But the Einstein action will eventually be subsumed into a UV complete theory of gravity, and in such a theory there can be a new class of solutions that are not quite black holes. Within a Planck length of the would-be horizon, strong gravity and high curvatures quickly turn on. These solutions are analogous to the hadrons and/or the quark matter states of QCD. They are very close to being completely black, but not quite. An ideal probe to test for not quite black holes are the low frequency gravitational waves that are excited in and around them when they are newly formed, as in the merger events observed by LIGO. There are some key features of waves that escape the interior of not quite black holes, and from this we describe our own search and search results using LIGO data.

Mariangela Lisanti, Princeton University

Discovering the Goddess of the Night with Machine Learning

The Gaia mission is in the process of mapping nearly 1% of the Milky Way’s stars. This data set is unprecedented and provides a unique view into the formation history of our Galaxy and its associated dark matter halo.   My talk will focus primarily on recent work using deep learning methods to classify Gaia stars that were born inside the Milky Way, versus those that were accreted from satellite mergers.  Using these techniques, we discovered a vast stellar stream, called Nyx (after the Goddess of the Night), in the Solar vicinity that co-rotates with the Galactic disk.  If Nyx is the remnant of a disrupted dwarf galaxy, it may provide the first evidence for an accreted stellar disk and a dark matter disk.

Moritz Munchmeyer, Perimeter Institute for Theoretical Physics

kSZ tomography and its applications to cosmology

Upcoming CMB and large-scale structure experimental data can be cross correlated to reconstruct the large-scale matter velocity field in a process called kinetic Sunyaev–Zel'dovich (kSZ) tomography. Similar to CMB lensing reconstruction, kSZ tomography provides a large-scale probe from small scale observations. kSZ tomography is a powerful probe of cosmology, in particular of primordial non-Gaussianity, and I will discuss how the scientific returns from upcoming galaxy surveys can be enhanced with this method. I will also discuss a general bispectrum approach to kSZ estimation, which unifies several previously known methods.

Masamune Oguri, Kavli Institute for Theoretical Physics

Gravitational waves in the inhomogeneous Universe

The discovery of gravitational waves from a binary black hole merger in 2015 opened up a new window to study the Universe, including the origin of black holes, the nature of dark matter, and the expansion history of the Universe. However, gravitational waves emitted from binary mergers propagate through the inhomogeneous Universe, which can have a considerable impact on observations of gravitational waves, in good or bad ways. I will highlight some examples of the effects of the inhomogeneity on gravitational wave observations, including their possible applications and implications.

Ue-li Pen, Canadian Institute for Theoretical Astrophysics

Cosmology and fundamental physics with FRBs

FRBs are the only known sources of extragalactic coherent radiation, that show interference phenomena after traveling over cosmological distances.  The interferometric probe allows equivalent strain measurements of $h\sim 10^{-26}$, opening new windows for gravitational wave detection, dark matter properties, and emission physics.  I describe new directions, theoretical and observational tools, and current and future experiments.

The Present Expansion rate of the Universe, Evidence of New Physics?

The Hubble constant remains one of the most important parameters in the cosmological model, setting the size and age scales of the Universe. Present uncertainties in the cosmological model including the nature of dark energy, the properties of neutrinos and the scale of departures from flat geometry can be constrained by measurements of the Hubble constant made to higher precision than was possible with the first generations of Hubble Telescope instruments. A streamlined distance ladder constructed from infrared observations of Cepheids and type Ia supernovae with ruthless attention paid to systematics now provide <2% precision and offer the means to do much better. By steadily improving the precision and accuracy of the Hubble constant, we now see evidence for significant deviations from the standard model, referred to as LambdaCDM, and thus the exciting chance, if true, of discovering new fundamental physics such as exotic dark energy, a new relativistic particle, or a small curvature to name a few possibilities. I will review recent and expected progress.

Neelima Sehgal, Stanford University

Probing Dark Matter Particle Properties with Ultra-High-Resolution CMB Lensing

I will discuss a novel and powerful way to probe dark matter particle properties using deep, high-resolution cosmic microwave background (CMB) gravitational lensing measurements.  These measurements can distinguish between cold dark matter and alternative dark matter models that can explain observational puzzles of small-scale structure.  I will also discuss a new experiment being developed, called CMB-HD, that can achieve this science and also open new windows on the early Universe, gas and galaxy evolution, planetary studies, and the transient sky.

Kendrick Smith, Perimeter Institute for Theoretical Physics

CHIME: The Canadian Hydrogen Intensity Mapping Experiment

CHIME is a new interferometric telescope at radio frequencies 400-800 MHz. The mapping speed (or total statistical power) of CHIME is among the largest of any radio telescope in the world, and the technology powering CHIME could be used to build telescopes which are orders of magnitude more powerful. Recently during precommissioning, CHIME started finding new fast radio bursts (FRB's) at an unprecedented rate, including a new repeating FRB.Understanding the origin of fast radio bursts is a central unsolved problem in astrophysics, and we anticipate that CHIME's statistical power will play an important role in solving it.  In this talk, I'll give a status update on CHIME, with emphasis on FRB's.

Gerard 't Hooft, Utrecht University

The antipodal identification as a new boundary condition on the horizon, and how it comes about

Quantizing the black hole can be done without String Theory, fuzz balls, AdS/CFT and such. We just assume matter to keep the form of point particles until they come close to the horizon. The gravitational back reaction of these particles generates a novel relation between particles going in and particles going out, enabling us to transform in-going particles into out-going ones. This transformation removes "firewalls" along the future and past horizons, but it strongly affects space-time inside a black hole. It subsequently allows us, and indeed forces us, to identify antipodal points on the horizon. We argue that this is the only way to restore unitarity for the quantum evolution operator, and to identify the black hole microstates. Some mysteries, however, remain unresolved.

## Wrap Up

Friday Sep 06, 2019
Speaker(s):
Scientific Areas:

## CNB Detection and Neutrino Mass Measurement with PTOLEMY

Friday Sep 06, 2019
Speaker(s):
Scientific Areas:

## kSZ tomography and its applications to cosmology

Friday Sep 06, 2019
Speaker(s):

Upcoming CMB and large-scale structure experimental data can be cross correlated to reconstruct the large-scale matter velocity field in a process called kinetic Sunyaev–Zel'dovich (kSZ) tomography. Similar to CMB lensing reconstruction, kSZ tomography provides a large-scale probe from small scale observations. kSZ tomography is a powerful probe of cosmology, in particular of primordial non-Gaussianity, and I will discuss how the scientific returns from upcoming galaxy surveys can be enhanced with this method.

Scientific Areas:

## Probing Dark Matter Particle Properties with Ultra-High-Resolution CMB Lensing

Friday Sep 06, 2019
Speaker(s):

I will discuss a novel and powerful way to probe dark matter particle properties using deep, high-resolution cosmic microwave background (CMB) gravitational lensing measurements. These measurements can distinguish between cold dark matter and alternative dark matter models that can explain observational puzzles of small-scale structure. I will also discuss a new experiment being developed, called CMB-HD, that can achieve this science and also open new windows on the early Universe, gas and galaxy evolution, planetary studies, and the transient sky.

Scientific Areas:

## Discovering the Goddess of the Night with Machine Learning

Friday Sep 06, 2019
Speaker(s):

The Gaia mission is in the process of mapping nearly 1% of the Milky Way’s stars. This data set is unprecedented and provides a unique view into the formation history of our Galaxy and its associated dark matter halo. My talk will focus primarily on recent work using deep learning methods to classify Gaia stars that were born inside the Milky Way, versus those that were accreted from satellite mergers. Using these techniques, we discovered a vast stellar stream, called Nyx (after the Goddess of the Night), in the Solar vicinity that co-rotates with the Galactic disk.

Scientific Areas:

## Discussion: Is there novel physics at the black hole horizon?

Thursday Sep 05, 2019
Speaker(s):
Scientific Areas:

## Not quite black holes at LIGO

Thursday Sep 05, 2019
Speaker(s):

The Einstein action has made us very accustomed to black holes and their “no drama” event horizons. But the Einstein action will eventually be subsumed into a UV complete theory of gravity, and in such a theory there can be a new class of solutions that are not quite black holes. Within a Planck length of the would-be horizon, strong gravity and high curvatures quickly turn on. These solutions are analogous to the hadrons and/or the quark matter states of QCD. They are very close to being completely black, but not quite.

Scientific Areas:

## Quantum gravity from fakeons

Thursday Sep 05, 2019
Speaker(s):

A new quantization prescription is able to endow quantum field theory with a new type of “particle”, the fakeon (fake particle), which mediates interactions, but cannot be observed. A massive fakeon of spin
2 (together with a scalar field) allows us to build a theory of quantum gravity that is both renormalizable and unitary, and basically unique.

Scientific Areas:

## Nonsingular transition from an evaporating black hole to a white hole

Thursday Sep 05, 2019
Speaker(s):

A "quasi-classical" picture of the transition from an evaporating black hole to a white hole is described, which is based on a resolution of the Schwarzschild singularity suggested by loop quantum gravity. All quantum information trapped by the black hole is eventually released from the white hole, without any Cauchy horizons, consistent with unitarity. The effective stress-energy tensor suggests that inflow of negative energy associated with Hawking "partners" in the interior of the black hole becomes, at least initially, an outflow of negative energy from the white hole.

Scientific Areas:

## The antipodal identification as a new boundary condition on the horizon, and how it comes about

Thursday Sep 05, 2019
Speaker(s):

Quantizing the black hole can be done without String Theory, fuzz balls, AdS/CFT and such. We just assume matter to keep the form of point particles until they come close to the horizon. The gravitational back reaction of these particles generates a novel relation between particles going in and particles going out, enabling us to transform in-going particles into out-going ones. This transformation removes "firewalls" along the future and past horizons, but it strongly affects space-time inside a black hole.

Scientific Areas:

## Pages

Scientific Organizers:

• Niayesh Afshordi, Perimeter Institute & University of Waterloo
• Latham Boyle, Perimeter Institute
• Lena Funcke, Perimeter Institute
• Elias KiritsisAstroparticle and Cosmology Laboratory
• Laura Lopez HonorezInternational Solvay Institutes