Messengers of the very early universe: Gravitational Waves and Primordial Black Holes

12 Dec 2022, 08:00 → 14 Dec 2022, 19:00 Europe/Rome

Sala Grande (Centro Universitario Padovano)

Alvise Raccanelli (CERN), Angelo Ricciardone (Istituto Nazionale di Fisica Nucleare), Guillem Domenech (INFN-Padova), Sabino Matarrese (PD)

The "Messengers of the Early Universe: Gravitational Waves and Primordial Black Holes" workshop is an event within the Fellini Project.

The workshop has received funding from the European Union’s Horizon2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 754496.

The workshop is organized by the INFN Padova Unit and the Department of Physics and Astronomy of the Padova University

The Workshop aims at gathering leading experts on primordial cosmology with gravitational waves to discuss prospects on probing the unexplored periods of the very early universe, such as inflation and reheating.

Keynote speakers include:

• Nicola Bartolo (Padova University)
• Christian Byrnes (Sussex University)
• Guillem Domenech (INFN Padova)
• Marc Kamionkowski (Johns Hopkins University)
• Ely Kovetz (Ben-Gurion University)
• Chiara Mingarelli (Connecticut University)*
• Paolo Pani (Rome University)
• Subodh Patil (Leiden University)
• Sebastien Renaux-Petel (Institut Astrophysique de Paris)
• Misao Sasaki (IPMU Tokyo)

* Online talk

Registration
No fee is required to participate to the workshop. However, for organizational purposes, registration is mandatory and has to be done through the registration form in this Indico site.

The workshop will be mainly in-person and will consist of invited talks.

 

 

 

 

Monday, 12 December

08:30 Registration

12th Morning Session

1 welcome and Introduction

Speaker: Antonio Masiero (Istituto Nazionale di Fisica Nucleare)

2 Welcome and Introduction

Speaker: Sabino Matarrese (Istituto Nazionale di Fisica Nucleare)

3 Primordial Black Holes from Inflation

In addition to the traditional method of using micro- lensing, the rapid progress in gravitational wave astrophysics/cosmology has made projections of detecting signatures of PBHs quite feasible. Parallel to it, various models of inflation that produce PBHs have been proposed. In this talk I'll review the PBH formation from inflation, focusing on some recently-found novel mechanisms that lead to it.

Speaker: Misao Sasaki (Kavli Institute for the Physics and Mathematics of the Universe (IPMU))

Misao_Sasaki.pdf

10:30 Coffee break

Second part 12th morning

4 Probing the dark era of inflation with oscillatory features of the stochastic gravitational wave background

Speaker: Sebastien Renaux-Petel

Sebastien-Renaux-Petel.pdf

5 Initial isocurvature and Gravitational waves

Speaker: Guillem Domenech (Istituto Nazionale di Fisica Nucleare)

Guillem_Domenech.pdf

12:30 Lunch break

12th afternoon session (part 1)

6 Effective potentials and quantum corrections in inflationary cosmology

Speaker: Subodh Patil (Leiden University)

Subodh_Patil.pdf

7 Gravitational waves from primordial black hole Poisson fluctuations

A gas of Poisson distributed primordial black holes (PBH) can induce at second order in cosmological perturbation theory a stochastic gravitational-wave (GW) background. This GW background can act as a novel method to extract constraints on cosmological models and gravitational theories. In this talk, we will discuss the above mentioned GW portal within the context of general relativity by accounting as well for the effect of realistic extended PBH mass functions and checking its potential detectability by GW experiments. Interestingly, by requiring not to have GW overproduction we set model-independent constraints the initial PBH abundance at PBH formation time as a function their mass. Finally, we study the aforementioned GW signal within the context of f(R) modified theories of gravity showing that it can serve as a novel probe constraining the underlying gravity theory.

Speaker: Theodoros Papanikolaou (National Observatory of Athens)

Theodoros_Papanikolaou.pdf

15:30 Coffee break

12th afternoon session (part 1)

8 GW and PBH from sharp turns in axion monodromy inflation

Large and sharp turns in multifield inflation are attractive from the phenomenological point of view, but are difficult to obtain in supergravity. It can be shown that large and sharp turns can be naturally realised due to transient violations of slow-roll in axion monodromy inflation in SUGRA. In this setup, the scalar power spectrum can have a peaked profile with resonant oscillations at small scales with large peak amplitude ~ 0.01. Such large power spectra can lead to abundant production of PBHs and characteristic oscillatory spectra of GW sourced by the scalar fluctuations. This model is one of the first concrete realisations of resonant features in the power spectra, which are imprinted in the induced GW spectrum as well. For suitable choices of the model parameters, inflation can sustain for ~55-65 e-folds, leading to abundant production of very light PBH and large induced GW spectrum for a wide range of frequencies. These GW spectra can be large and wide with characteristic resonant oscillations, which can be probed by upcoming surveys such as LISA.

Speaker: Sukannya Bhattacharya

Sukannya_Bhattacharya.pdf

9 NON-LOCAL PERTURBATIONS DURING INFLATION

During this talk I will show how non-local terms in the linearized Einstein's equations are necessary to correctly describe the behaviour of gauge invariant quantities at superhorizon scales during inflation. Once this is clarified, I will explore how some approaches that aim to describe the large quantum fluctuations responsible for the formation of Primordial Black Holes (PBH) get affected by the inclusion of non-local terms. Stochastic inflation and the \deltaN formalism are some of these approaches.

Speaker: Diego Cruces (ICCUB)

Diego_Cruces.pdf

discussion

Tuesday, 13 December

13th morning session

10 Primordial non-Gaussianity (PNG), Primordial Black Holes (PBH) and Gravitational waves (GWs)

I will discuss the effects of PNG on PBH abundance and scalar induced GWs. I will also touch on a viable model of axion inflation (coupled with gauge fields) and probes of small scales via mu distortions and GWs at PTA.

Speaker: Caner Unal

Caner_Unal.pdf

11 Lattice simulations of axion-U(1) inflation

I present the first nonlinear lattice simulation of an axion field coupled to a U(1) gauge field during inflation. The simulation allows to fully characterize the statistics of the primordial curvature perturbation. We find high-order statistics to be essential in describing non-Gaussianity in the linear regime of the theory. On the contrary, non-Gaussianity is suppressed when the dynamics becomes nonlinear. This relaxes bounds from overproduction of primordial black holes, allowing for an observable gravitational waves signal at interferometer scales. Our work establishes lattice simulations as a crucial tool to study the inflationary epoch and its predictions.

Speaker: Angelo Caravano (LMU Munich)

Angelo_Caravano.pdf

10:30 coffe-break

13th morning session part 2

12 Searching for primordial BHs in GW data: Recipes for single-event and population studies

Speaker: Paolo Pani (Istituto Nazionale di Fisica Nucleare)

Paolo_pani.pdf

13 Microlensing of gravitational waves by dark matter

Gravitational lensing of gravitational waves provides a potential new probe of dark matter structures. In this talk, I will focus on the microlensing effect on gravitational wave signals from compact object binaries. I will describe how this effect changes the gravitational wave signal and discuss whether it can be detected. I will show that primordial black holes and other compact dark matter objects can be probed through the microlensing of gravitational waves.

Speaker: Ville Vaskonen

Ville_Vaskonen.pdf

12:30 Lunch break

13th afternoon session part 1

14 Tracking the origin of black holes with the stochastic gravitational wave background popcorn signal

Speaker: Sachiko Kuroyanagi

Sachiko_Kuroyanagi.pdf

15 Scale-invariant enhancement of gravitational waves during inflation

Speaker: Atsuhisa Ota

Atsuhisa_ota.pdf

16 Implications for the formation of primordial black holes from the third LIGO-Virgo observing run

Formation of primordial black holes from inflationary fluctuations is accompanied by a scalar induced gravitational wave background. We perform a Bayesian search of such a background in the data from Advanced LIGO and Virgo's first, second and third observing runs, parametrizing the peak in the curvature power spectrum by a log-normal distribution. The search shows no evidence for such a background. We place 95\% confidence level upper limits on the integrated power of the curvature power spectrum peak which, for a narrow width, reaches down to 0.02 at 1017Mpc−1. The resulting constraints are stronger than those arising from BBN or CMB observations. In addition, we find that LIGO, at its design sensitivity, and the Einstein Telescope can compete with the constraints related to the abundance of the formed primordial black holes.

Speaker: Alba Romero

Alba_Romero.pdf

15:30 Coffee break

13th afternoon part 2

17 Pulsar Timing Arrays: The Next Window to Open on the Gravitational-Wave Universe

Galaxy mergers are a standard aspect of galaxy formation and evolution, and most (likely all) large galaxies contain supermassive black holes. As part of the merging process, the supermassive black holes should in-spiral together and eventually merge, generating a background of gravitational radiation in the nanohertz to microhertz regime. An array of precisely timed pulsars spread across the sky can form a galactic-scale gravitational wave detector in the nanohertz band. I describe the current efforts to develop and extend the pulsar timing array concept, together with recent limits which have emerged from international efforts to constrain astrophysical phenomena at the heart of supermassive black hole mergers.

online talk

Speaker: Chiara Mingarelli

Chiara_Mingarelli.pdf

discussion

Wednesday, 14 December

14th morning session part 1

18 Prospects to detect a PBH merging channel”

Speaker: Ely Kovetz

Ely_Kovetz.pdf

10:30 coffee-break

14th morning session part 2

19 PBHs: Fine-tuning and fine opportunities

Speaker: Chris Byrnes

Chris_Byrnes.pdf

20 Dark matter and dark radiation from evaporating primordial black holes

Speaker: Isabella Masina (FE)

Isabella_Masina.pdf

12:30 lunch break

14 afternnon session part 1

21 ​New avenues to the Cosmological Gravitational Wave Background

Speaker: Nicola Bartolo (Istituto Nazionale di Fisica Nucleare)

22 Signatures of Primordial Gravitational Waves on the Large-Scale Structure of the Universe

Primordial scalar perturbations are always considered as a source in the study of large-scale structures. Being the dominant ones at first order in perturbation theory, they have also encouraged the study of generation of second order gravitational waves from them. We seek to investigate the opposite effect, i.e. if gravitational waves can have an observable contribution on the matter power spectrum in the second order. For this, we consider gravitational waves with broken scale-invariance, which happens in some models of inflation. Our results are positive about having a significant effect, and we notice a crucial characteristic of this new effect, unlike the standard matter perturbation, it does not exist outside the horizon scales, although on smaller scales it can be said that it mimics the linear one.

Speaker: Pritha Bari

Pritha_Bari.pdf

15:30 coffee-break

14 afternnon session part 2

23 Stochastic GW Backgrounds

Speaker: Marc Kamionkowski (JHU)

Marc_Kamionkowski.pdf

Discussion