GRAPPA10

2 Jul 2023, 10:00 → 5 Jul 2023, 23:30 Europe/Amsterdam

Turingzaal (CWI)

In 2012 the University of Amsterdam started Gravitation Astroparticle Physics Amsterdam (GRAPPA), its new excellence center for astroparticle physics, a multidisciplinary initiative of three institutes on the Science campus in Amsterdam. Over the last 10 years this new initiative resulted in the hiring of 10 new faculty members, working on topics like dark matter (indirect) detection, gamma-ray emission from cosmic-ray sources, neutrino research, gravitational wave and multimessenger observations of compact objects, and theory and the observations of the early Universe.

After ten years GRAPPA has become an household name in astroparticle physics, and a thriving place to do astroparticle physics research, involving around 50 researchers. In order to celebrate our ten-year anniversary GRAPPA is organising a three day symposium on all aspects of astroparticle physics, with an impressive list of invited speakers: David Berge, Pasquale Blasi, Jan de Boer, Manuela Campanelli, Kyle Cranmer,  Andreas Freise, Tanja Hinderer, Bradley Kavanagh, Kumiko Kotera, Teresa Marrodán Undagoitia, Alison Mitchell, Hiranya Peiris, Alessandra Silvestri, Christian Stegmann, Licia Verde, and Kathryn Zurek. 

We invite colleagues who are interested in astroparticle physics to join us in the celebration of GRAPPA’s ten-year anniversary. Apart from a host of excellent invited speakers we also have a number of open slots for interesting contributions in the field of astroparticle physics.

SOC: Samaya Nissanke (chair), Shin'ichiro Ando, Daniel Baumann, Gianfranco Bertone, Patrick Decowski, Ben Freivogel, Sera Markoff, Philipp Mösta, Jacco Vink, Christoph Weniger.

LOC: Jirina Salkova (chair), Samaya Nissanke, Shin'ichiro Ando, Gianfranco Bertone, Sheridan Lloyd, Philipp Mösta, Dion Noordhuis, Christoph Weniger.

We thank our current sponsors IoP (UvA), API (UvA), Nikhef, NOVA, and NWO. 

By attending GRAPPA10 you agree to the GRAPPA code of conduct.

Sunday, 2 July

18:00 Welcome reception at the EYE

Monday, 3 July

1 Welcome

2 Rector's Welcome

3 Dean's Welcome

4 The future of astroparticle physics - the next 10 years

Speaker: Christian Stegmann

10:15 Coffee

5 TeV gamma-ray highlights during the first decade of GRAPPA

Speaker: David Berge

6 Gamma-ray Astronomy: Current status and future outlook

Speaker: Alison Mitchell

12:15 Lunch

7 Cosmology and Multi-Messenger Astrophysics with Gamma-Ray Bursts

The huge luminosity, the redshift distribution extending at least up to z~10 and the association with the explosive death of very massive stars make long GRBs extremely powerful probes for investigating the early Universe (pop-III stars, cosmic re-ionization, SFR and metallicity evolution up to the “cosmic dawn”) and measuring cosmological parameters. At the same time, as demonstrated by the GW170817 event, short GRBs are the most prominent electromagnetic counterpart of gravitational-wave sources like NS-NS and NS-BH merging events, and both long and short GRBs are expected to be associated with neutrino emission. Moreover, the combination of extreme distances, huge number of photons emitted over wide photon energy range and the variability down to few ms makes these phenomena a promising tool for performing tests of fundamental physics like Lorentz Invariance Violation (LIV). My review will include the status, concepts and expected performances of space mission projects in which INAF and the Italian astronomical community are
heavily involved, aiming at fully exploiting these unique potentialities of the GRB phenomenon, thus providing an ideal synergy with the large e.m. facilities of the future like LSST, ELT, TMT, SKA, CTA, ATHENA in the e.m. domain, advanced second generation (2G++) and third generation (3G) GW detectors (ET, CE) and future large neutrino detectors (e.g., Km3NET).

Speaker: Lorenzo Amati (INAF - OAS Bologna (Italy))

8 Gamma-ray emission from the Sagittarius Dwarf Spheroidal galaxy due to millisecond pulsars

The Fermi Bubbles are giant, gamma-ray emitting lobes emanating from the nucleus of the Milky Way discovered in ~1-100 GeV data collected by the Fermi Gamma-Ray Space Telescope. Previous work has revealed substructure within the Fermi Bubbles that has been interpreted as a signature of collimated outflows from the Galaxy's super-massive black hole. In this talk, I will show that much of the gamma-ray emission associated to the brightest region of substructure -- the so-called cocoon -- is likely due to the Sagittarius dwarf spheroidal (Sgr dSph) galaxy. This large Milky Way satellite is viewed through the Fermi Bubbles from the position of the Solar System. As a tidally and ram-pressure stripped remnant, the Sgr dSph has no on-going star formation, but I will demonstrate that the dwarf's millisecond pulsar (MSP) population can plausibly supply the observed gamma-ray signal. This finding plausibly suggests that MSPs produce significant gamma-ray emission amongst old stellar populations, potentially confounding indirect dark matter searches in regions such as the Galactic Centre, the Andromeda galaxy, and other massive Milky Way dwarf spheroidals.

Speaker: Oscar Macias (University of Amsterdam)

9 Discovering the Millisecond Pulsar population responsible for the Gamma-Ray excess in the Sagittarius Dwarf Spheroidal galaxy with Radio Telescopes.

Observations of the Sagittarius dwarf spheroidal galaxy with the Fermi Gamma-Ray Space Telescope have revealed an excess of extended emission likely originated by an emerging population of millisecond pulsars in the core of this dwarf. In this talk, I will discuss the sensitivity of current and upcoming radio telescopes to this putative population of millisecond pulsars. I will show that the Square Kilometer Array (SKA) will be the most sensitive instrument for detecting these objects. With about 20 minutes of exposure per pointing, the SKA will be capable of identifying approximately ~20 millisecond pulsars in the Sgr dSph. This would confirm the hypothesis that the Sgr dSph galaxy excess is due to an unresolved population of millisecond pulsars and would decisively exclude a dark matter explanation for the excess.

Speaker: Lucia Gebauer Werner

10 The colliding wind binary Eta Carinae as a cosmic ray factory

The binary stellar system Eta Carinae is one of very few established astrophysical hadron accelerators and one of only two colliding wind binary systems detected in the gamma-ray regime. At the shocks in the wind collision region, particles are accelerated beyond TeV energies. It seems likely that at least some fraction of the accelerated particles escape from the system. Copious target material for hadronic interactions and associated gamma-ray emission exists on a wide range of spatial scales outside the binary system. This material creates a unique opportunity to trace the propagation of particles into the interstellar medium. Here we analyse gamma-ray data from Fermi-LAT of Eta Carinae and surrounding molecular clouds and investigate the many different scales on which escaping particles may interact and produce gamma rays. We find that interactions of escaping cosmic rays from Eta Carinae in the wind region and the Homunculus Nebula could produce a significant contribution to the gamma-ray emission associated with the system. Furthermore, we detect excess emission from the surrounding molecular clouds. The derived radial cosmic-ray excess profile is consistent with a steady injection of cosmic rays by a central source. However, this would require a higher flux of escaping cosmic rays from Eta Carinae than provided by our model. Therefore it is likely that additional cosmic ray sources contribute to the emission from the clouds.

Speaker: Dr Mischa Breuhaus (Max Planck Institute for nuclear physics)

11 Sequential simulation-based inference for strong gravitational lensing images

Galaxy-galaxy strong gravitational lenses are a unique laboratory for probing the smallest self-bound dark matter structures in our Universe and testing the $\Lambda$CDM paradigm. However, performing precise statistical analysis of such observations is extremely challenging, since it requires disentangling the source galaxy’s light from the lens’ mass distribution and marginalizing over different substructure configurations. Research in this field can be broadly separated into works that aim to directly detect individual perturbers and works that aim to statistically constrain the matter distribution by looking at collective perturbations caused by an unresolved population of perturbers.
In this talk, I will present recent advances in both of these approaches using a new multi-stage neural simulation-based inference method. I will also show the first application of machine learning to a real strongly lensed observation by reanalyzing JVASB1938+666 system, one of the few examples so far of substructure detection using traditional gravitational imaging techniques. These first results demonstrate that this method is imminently applicable to existing lensing data and to the large sample of very high-quality observational data that will be delivered by near-future telescopes.

Speaker: Noemi Anau Montel (GRAPPA)

Sequential SBI for Lensing.pdf

12 High Energy Cosmic Rays

Speaker: Pasquale Blasi

15:15 Coffee

13 From the Higgs Discovery to Simulation-based Inference

Speaker: Kyle Cranmer

14 Studying neutrinos with DUNE

The Deep Underground Neutrino Experiment (DUNE) is a near-future neutrino oscillation experiment in the U.S.A. consisting of a high-intensity neutrino beam produced and characterized at Fermilab, Illinois before it travels 1300 km to reach the DUNE Far Detector site in SURF, South Dakota. The DUNE experiment features a wide range of neutrino beam energies, long baseline length, and excellent energy resolution with the novel Liquid Argon Time Projection Chamber (LArTPC) technology for the Far Detector.

In this talk, I will first give an overview of the primary physics program of DUNE. The program includes precision measurement of neutrino oscillation to measure the PMNS matrix, resolve the neutrino mass ordering problem, and study CP violation in the leptonic sector. Furthermore, DUNE will also search for proton decay and detect neutrinos from supernova core collapse in our galaxy. I will also briefly summarize the current status and timeline of the experiment.

Lastly, I will give an overview of my work on ProtoDUNE, the far detector prototype program at CERN, aimed at developing and testing the necessary technology required for building the four 17 kt LArTPC modules planned for the DUNE Far Detector.

Speaker: Mr Vikas Gupta (NIKHEF)

dune_grappa.pdf

15 IceCube search for neutrinos from GRB 221009A

Gamma-ray bursts (GRBs) have long been a promising candidate for neutrino emission, with different theoretical models predicting neutrino fluxes across a large range of energies. While correlations between GRBs and neutrinos have yet to be found, GRB 221009A is an exceptionally interesting target for neutrino searches. As the brightest GRB ever observed and the first with >10 TeV photons, GRB 221009A gives us a unique opportunity to probe GRB neutrino emission. Using a variety of methods, applying different time windows and specializing for the different energy ranges, IceCube has been able to search for neutrinos ranging from MeV to PeV energies from GRB 221009A. These methods include looking for the photo-multiplier rates scalars usually reserved for MeV supernova neutrinos, to looking for an increase in GeV event rates inside DeepCore, to using traditional point source methods for searches from 10 GeV to 1 TeV with DeepCore and > 1 TeV with the full IceCube detector. With these different methods of neutrino observation it is possible to cover 9 orders of magnitude in neutrino energy, placing stringent limits on the neutrino emission of the brightest ever observed GRB.

Speaker: Karlijn Kruiswijk (UCLouvain)

16 CR antinuclei predictions and their detectability in the next years

The creation of anti-nuclei in the Galaxy has been has been discussed as a possible signal of exotic production mechanisms such as primordial black hole evaporation or dark matter decay/annihilation, in addition to the conventional production from cosmic-ray (CR) interactions. Tentative observations of CR antihelium by the AMS-02 collaboration have re-energized the quest to use antinuclei to search for physics beyond the standard model.
In this talk, we show state-of-art predictions of the antinuclei spectrum from both astrophysical and standard dark matter annihilation models obtained from combined fits to high-precision antiproton data as well as CR nuclei measurements (specially B, Be, Li). Astrophysical sources are capable of producing $\mathcal{O}(1)$ antideuteron event and $\mathcal{O}(0.1)$ antihelium events over 15~years of AMS-02 observations. Standard dark matter models could potentially produce $\mathcal{O}(1)$ antihelium event, while the production of a larger antihelium flux would require more novel dark matter model building. We also discuss that annihilation/decay of a QCD-like dark sector could potentially explain the AMS-02 preliminary observations of antihelium-3 and antihelium-4.

Speaker: Pedro De la Torre Luque (Oskar Klein Centre, Stockholm University)

GRAPPA_DelaTorreLuque.pptx

19:00 Public Event at the ARTIS

Tuesday, 4 July

17 Tanja Hinderer

18 Manuela Campanelli

19 Distinguishing environmental effects on gravitational waveforms

LISA, the space-based gravitational wave detector, is due to fly in the mid 2030s. An entire new frequency range will be opened up for discovering gravitational wave sources, including intermediate and extreme mass ratio black hole binaries which will remain in band for up to weeks, months or even years. This offers an exciting new avenue for fundamental physics discoveries because the environment of the binaries will have an effect on the gravitational waveform over this long period of time, and we will be able to measure the properties of the environments from the gravitational wave observations alone.

I will show that we can measure the parameters of not only baryonic environments such as accretion disks, but also the properties of dark matter spikes or clouds of scalar fields if they are present around the binaries. I will demonstrate that we can distinguish between different environments with a Bayesian model comparison approach and argue the importance of including environmental effects in waveform modelling. This is so that we don't miss the opportunity to learn about the nature of dark matter or the structure of accretion disks, but crucially also so that we don't infer biased parameters by assuming that the system is inspiralling through vacuum.

Speaker: Philippa Cole (University of Amsterdam)

20 Spinning primordial black holes in a matter dominated universe

Interest in primordial black holes (PBHs) has spiked since the first detection of gravitational waves, and a few mass windows remain in which PBHs may still make up an appreciable part of dark matter. In a matter dominated universe, e.g. in the case of a first-order QCD phase transition, PBH production is enhanced and PBHs may have large dimensionless spins. We investigate the re-entry and collapse of superhorizon perturbations with initial dimensionless spins of $\chi^\xi_0\sim 0.1$ in this setting using full 3+1D numerical relativity simulations. We find that PBHs are formed with dimensionless spins $\chi_\textrm{PBH}$ smaller than but the same order of magnitude as $\chi^\xi_0$ and argue this suggests no PBHs with $\chi_\textrm{PBH} > 0.5$ are produced. Furthermore, we find that the addition of angular momentum only has a minor effect on the PBH mass and accretion rate. Additionally, we discuss apparent black hole horizons and cosmological horizons in the context of numerical relativity simulations of expanding spacetimes.

Speaker: Eloy de Jong (King's College London)

11:00 Coffee

21 How to build the Einstein Telescope

Speaker: Andreas Freise

22 Primordial Black Holes After 50 Years: A Positivist Perspective

Speaker: Bernard Carr

13:00 Lunch

23 Quantum Gravity, Chaos, Complexity, and Statistical Physics

Speaker: Jan de Boer

24 Quantum fields in compact stars.

Very compact stars seem to be forbidden in General Relativity. While Buchdahl's theorem sets an upper bound on compactness, further no-go results rely on the existence of two light rings, the inner of which is associated to gravitational instabilities. However, little is known about the role of QFT in these strong gravity regimes. We show that the renormalized stress tensor for CFTs diverges faster than the classical source as the star's surface approaches the Buchdahl radius rather than the Schwarzschild radius. The backreaction of quantum fields in this regime therefore cannot be ignored.

Speaker: Ignacio Reyes (University of Amsterdam)

25 PTOLEMY: resolving relics from the early universe

Though their imprint upon the CMB and large-scale structure of the universe remains to this day, Big Bang relic neutrinos (the CνB) have never been directly observed. This remains an outstanding test of the Standard Model in ΛCDM cosmology and, carrying a signal from only one second after the Big Bang, relies upon messengers predating any previously observed. PTOLEMY aims to make the first direct observation of the CνB by resolving the β-decay endpoint of atomic tritium to O(10meV) precision. If achieved, this first observation would also reap at least the lowest neutrino mass. The project is in its prototyping phase and looks to begin physics runs in the 2030s.

Speaker: James Mead (UvA)

grappa10_final.pdf

grappa10_final.pptx

15:15 Coffee

26 Direct detection of dark matter

Speaker: Teresa Marrodan Undagoitia

27 Diffuse Emission Models for the TeV Sky

Speaker: Tim Linden (Stockholm University)

grappa2023_widescreen.key

grappa2023_widescreen.pdf

28 Novel constraints on inflation from quantum cosmology

TBD

Speaker: Thomas Hertog (KU Leuven)

18:00 Conference Dinner at Paviljoen Puur

The dinner venue is https://paviljoenpuur.nl/

Wednesday, 5 July

29 Towards EeV Neutrino Astronomy

Speaker: Kumiko Kotera

30 Probing Hidden Sector Dark Matter Using Early Matter Domination

The absence of dark matter signals in direct detection experiments and collider searches has prompted interest in models in which dark matter belongs to a hidden sector minimally coupled to the Standard Model. In these scenarios, a long-lived massive particle might come to dominate the energy density of the early universe temporarily, causing an early matter-dominated era (EMDE) prior to the onset of nucleosynthesis. During an EMDE, matter perturbations grow more rapidly than they would in a period of radiation domination, which leads to the formation of microhalos much earlier than they would in standard cosmological scenarios. These microhalos generate observable signatures, but the constraints on these signatures are highly sensitive to the small-scale cut-off in the matter power spectrum. We discuss the effects of an EMDE on the matter power spectrum, focusing on cases where the particle that dominates the Universe during the EMDE was initially relativistic, and the small-scale cut-off in the power spectrum is set by its pressure support. We relate the power spectrum cut-off to the hidden sector properties and the particle mass and discuss avenues for constraining such scenarios using dark matter annihilation signals, gravitational microlensing and pulsar timing arrays.

Speaker: Himanish Ganjoo (Perimeter Institute)

31 Cosmological implications of the Higgs vacuum metastability during inflation

According to the current experimental data, the Higgs vacuum appears to be metastable due to the development of a second lower ground state in its potential. Consequently, vacuum decay would induce the nucleation of true vacuum bubbles with catastrophic consequences for our Universe and therefore we are motivated to study possible stabilising mechanisms in the early universe. In our latest investigation (2207.00696), we studied the electroweak metastability in the context of the observationally favoured model of Starobinsky inflation. Following the motivation and techniques from our first study (2011.037633), we obtained constraints on the Higgs curvature coupling $\xi$, while embedding the SM on the modified gravity scenario $R+R^2$, which introduces Starobinsky inflation naturally. This had significant repercussions for the effective Higgs potential in the form of additional negative terms that destabilize the false vacuum. Another important aspect lay in the definition for the end of inflation, as bubble nucleation is most prominent during its very last moments. Our results dictated that these stronger lower $\xi$-bounds are very sensitive to the final moments of inflation, where spacetime deviates increasingly from de Sitter.

Speaker: Andreas Mantziris (University of Warsaw)

Mantziris_GRAPPA.pdf

32 Neutrinos in the Mediterranean Sea

Neutrino astronomy is a rapidly evolving discipline probed by large-volume neutrino detectors such as those being built by the KM3NeT collaboration in the Mediterranean Sea, instrumenting a cubic kilometre of seawater. KM3NeT focuses on the detection of cosmic high-energy neutrino sources as well as measurements of the atmospheric neutrino oscillations to expand our understanding of fundamental physics.
The transparency of the seawater allows accurate reconstructions of events achieving <0.1 degree angular resolution for neutrinos with energies >100TeV with great potential to locate cosmic high-energy neutrino sources. The location of KM3NeT offers an excellent view of the Southern Hemisphere with the interesting galactic center region.
The construction of KM3NeT is ongoing with ~10% of the detector already deployed in the sea. The talk presents the first results and prospects of KM3NeT.

Speaker: Rasa Muller

20230700_GRAPPA_Conference_v5.pdf

33 Galactic Cosmic Ray accelerators and Their multi-messenger Signals

The origin and acceleration mechanisms of Galactic cosmic rays (CRs) are still unknown. Gamma-ray observations have been crucial in identifying potential sites of CR acceleration. However, understanding these observations is challenging because both hadronic and leptonic processes can produce gamma rays, and different mechanisms may be responsible for accelerating various CR species. A multi-messenger approach that includes current and potential observations of radio, X-ray, gamma-ray, and neutrino signals is necessary to disentangle these complex acceleration mechanisms and emission processes. In this talk, I will present the latest findings from our research involving semi-analytical methods and accurate numerical simulations to study the multi-messenger emissions produced by nearby very-high-energy astrophysical accelerators.

Speaker: Youyou Li (GRAPPA)

11:30 Coffee

34 Gravitational Wave Signatures of Dark Matter around Black Holes

Speaker: Bradley Kavanagh

35 Model-agnostic analysis of large-scale structure surveys and implications for cosmology

Speaker: Licia Verde

13:30 Lunch

36 The era of precision Cosmology and its surprises

Speaker: Alessandra Silvestri

37 Superradiance and binary inspirals

Ultralight bosons may be spontaneously produced by a rotating black hole through a process known as superradiance. This creates a "cloud" around the black hole that can manifest its presence in a variety of ways. In the past few years, scientists in Amsterdam and at GRAPPA have lead the effort of understanding the imprint left by such a cloud in a black hole binary inspiral. In this talk, I will review the main results of this endeavor, as well as present new developments that will allow a more realistic and general description of these systems.

Speaker: Giovanni Maria Tomaselli

38 Cleaning a Dark Matter Detector

In dark matter detection experiments, Xenon tanks are being used to find traces of dark matter particles that are hypothesised to crisscross the universe. For such detection to succeed, the Xenon in the tanks has to be clean. But what is clean? In this context, it means that no background mimics the signs of dark matter particles, and when there are no electronegativities that might erase such signs. In practice, such cleanliness is difficult to achieve – as soaps may be radioactive, steel may spread electronegativity, and humans are altogether dangerously filthy. In this talk, I discuss the idiosyncratic cleaning practices of the XENONnT experiment that aims find WIMP dark matter. What does ensuring a detector’s cleanliness entail? And how does one know whether a detector is, in fact, adequately clean?

Speaker: Jaco de Swart (Massachusetts Institute of Technology)

39 Prospects for understanding the physics of the Universe

Speaker: Hiranya Peiris

40 Conclusion - GRAPPA - The Next 10 years

Speaker: Gianfranco Bertone