Third EuCAPT Annual Symposium

31 May 2023, 09:00 → 2 Jun 2023, 17:00 Europe/Zurich

500/1-001 - Main Auditorium (CERN)

Gongjun Choi (CERN), Valerie Domcke (CERN)

The European Consortium for Astroparticle Theory (EuCAPT, https://www.eucapt.org) is a new initiative, with central hub at CERN, that aims to bring together the European community of theoretical astroparticle physicists and cosmologists. Our goals are to increase the exchange of ideas and knowledge; to coordinate scientific and training activities; to help scientists attract adequate resources for their projects; and to promote a stimulating, fair and open environment in which young scientists can thrive.     

After two online meetings in 2021 and 2022, we are delighted to announce the third edition of the EuCAPT annual symposium, the flagship event of our consortium, that aims to provide an interdisciplinary Europe-wide forum to discuss opportunities and challenges in Theoretical Astroparticle Physics and Cosmology. The symposium will take place at CERN, with online participation possible. We invite all scientists (PhD students, postdocs, and staff) active in these fields of research to join us remotely from May 31 to June 2, 2023. The symposium will feature invited presentations, and young scientists will have the opportunity to present their work with lightning talks.

For EuCAPT council members, please note that there will be a council meeting on May 30 (afternoon) at CERN. 

Invited speakers:  
Alexandra Amon (Kavli Institute for Cosmology, Cambridge)  
Angelo Esposito (University of Rome La Sapienza)  
Jose Maria Ezquiga (Niels Bohr Institute)   
Gabriele Franciolini (University of Rome La Sapienza)   
Julia Harz (Johannes Gutenberg University Mainz)
Matthew Lewandowski (ETH, Zurich)   
Mathew Madhavacheril (University of Pennsylvania)   
Silvia Manconi (LAPTh, CNRS)   
Mehrdad Mirbabayi (ICTP, Trieste)   
Andrea Mitridate (DESY Hamburg)   
Foteini Oikonomou (Norwegian University of Science and Technology)   
Ville Vaskonen (NICPB Tallinn & Padua University)   
Eduardo Vitagliano (Hebrew University)
Jorinde van der Vis (Utrecht University)
Sam Witte (Grappa Institute)   

Wednesday 31 May

09:15 → 09:30 Welcome

Convener: Gian Giudice

09:15 Welcome

Speaker: Gian Giudice (CERN)

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09:30 → 10:30 Dark Matter

Convener: Laura Baudis

09:30 Neutron stars as axion laboratories

Speaker: Sam Witte

Eucapt_2023_pdf.pdf

Eucapt_2023_ppt.pdf

Eucapt_2023_ppt.pptx

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10:00 Constraining primordial black holes as a dark matter candidate

Speaker: Gabriele Franciolini

Franciolini.pdf

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10:30 → 11:15 Coffee Break

11:15 → 12:30 Dark Matter

Convener: Laura Baudis

11:15 Light dark matter detection in the lab: new ideas and new tools

Speaker: Angelo Esposito

EuCAPT 2023.pdf

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11:45 Gamma-ray flux limits from nearby brown dwarfs: Implications for dark matter annihilating into long-lived mediators.

Brown dwarfs (BDs) are celestial objects representing the link between the least massive main-sequence stars and giant gas planets. I will present a recent analysis (Bhattacharjee et al.,2023) where consider a sample of nine nearby ($<$ 11 pc distance), cold and old BDs and look for gamma-ray signal from the direction of these objects using 13 years of \textit{Fermi}-LAT data. In the absence of any gamma-ray excess, we set 95\% confidence level upper limits on the gamma-ray flux with a binned-likelihood approach.

I will then show how this null result can be used to constrain particle dark matter (DM). If the DM of the universe is constituted of particles with non-negligible couplings to the standard model, BDs may efficiently accumulate them through scatterings. DM particles eventually thermalize and can annihilate into light, long-lived, mediators which later decay into photons outside the BD.

Within this framework, we set a stacked upper limit on the DM-nucleon elastic scattering cross section at the level $\sim 10^{-38}$ cm$^{2}$ for DM masses below 10 GeV. Our limits are comparable to similar bounds from the capture of DM particles in celestial objects but have the advantage of covering a larger portion of the parameter space in mediator decay length and DM mass and being less affected by DM modeling uncertainties.

Reference:
Bhattacharjee et al.,2023 - ``Gamma-ray flux limits from brown dwarfs: Implications for dark matter annihilating into long-lived mediators'' -Pooja Bhattacharjee, Francesca Calore, and Pasquale Dario Serpico - Phys. Rev. D 107, 043012 – Published 10 February 2023

Speaker: Pooja BHATTACHARJEE

Eucapt_talk_Pooja_Bhattacharjee.pdf

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11:52 Neural simulation-based inference of dark matter substructure in JVAS B1938+666 strong gravitational lensing system

Precision analysis of galaxy-galaxy strong gravitational lensing images provides a unique way of characterizing dark matter (DM) substructures and could allow us to uncover the fundamental properties of DM's constituents. In reality, this analysis is extremely challenging due to the high dimensionality of lensing observations and the richly-structured parameter space of lensing systems. Existing methods for marginalizing over this large parameter space to infer substructure properties are typically extremely time-consuming, necessitating the exploration of a very high-dimensional parameter space, which is often intractable, or require compressing observations into hand-crafted summary statistics.

In this talk, I will present the first application of neural simulation-based inference (SBI) technique to a strong-lensing observation, by reanalizing JVAS B1938+666 system. This system is one of the few examples, so far, of substructure detection (Vegetti et al. 2012) using the gravitational imaging technique.
I will show how different analysis tasks of increasing complexity can be easily performed in the employed SBI technique, Truncated Marginal Neural Ratio Estimation (TMNRE) (Miller et al. 2022). With TMNRE we can recover existing results for subhalo parameter inference and source reconstruction. Moreover, since TMNRE makes it possible to increase the realism of the analysis without significantly altering the inference procedure, we are able to include lens light uncertainties, source light variations, and a population of substructure in the analysis (Anau Montel et al. 2022, Coogan et al. 2022).

These first results demonstrate our analysis method is able to extract the wealth of information regarding DM's nature contained in existing lensing data and in the large sample of lenses that will be delivered by near-future telescopes, such as the Rubin Observatory, Euclid, JWST and the Extremely Large Telescope.

Speaker: Noemi Anau Montel (University of Amsterdam)

NoemiAnauMontel_3Eucapt.pdf

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11:59 Dark Matter Pollution in the Diffuse Supernova Neutrino Background

Upcoming neutrino experiments are expected to detect the Diffuse Supernova Neutrino Background (DSNB). This requires pondering all possible sources of background. Sub-GeV dark matter (DM) which annihilates into neutrinos is a potential background that has not been considered so far. We simulate DSNB and DM signals, as well as backgrounds in the Hyper-Kamiokande detector. We find that DM-induced neutrinos could indeed alter the extraction of the correct values of the parameters of interest for DSNB physics. While this opens the possibility of simultaneously characterizing the DNSB and discovering DM via indirect detection, we argue that it would be hard to disentangle the two contributions due to the lack of angular information available at low energies.

Speaker: Sandra Robles (Fermilab)

DMpollution_DSNB_EuCAPT.pdf

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12:06 Cosmic Web Studies in Fuzzy Dark Matter Cosmologies

Fuzzy dark matter (FDM) modifies the internal properties of dark matter halos and large-scale cosmic environments. In this talk I will share selected insights from recent work based on cosmological $N$-body simulations. We find that the concentration of FDM-like halos peaks around two decades above the half-mode mass, breaking the approximate universality of halo density profiles observed in ΛCDM. Shape parameter profiles (intermediate-to-major and minor-to-major axis ratios) of FDM-like halos are more elongated around the virial radius and less elongated near the center, deviating from the monotonicity observed in ΛCDM. We reassess intrinsic alignment correlations in FDM-like cosmologies and comment on their importance in upcoming weak lensing surveys. Finally, the cosmic web itself sees its mass distribution gradually reshuffled as the axion mass is reduced, leading to changes in the cosmic tidal fields. We quantify the mass and volume filling fractions of cosmic environments and find that in FDM-like cosmologies, 2D cosmic sheets host a larger share of the matter content of the Universe compared to ΛCDM. We show that FDM-like cosmologies exhibit more peaked log overdensity probability distribution functions and systematically higher skewness estimates compared to ΛCDM, particularly at high redshift. These results suggest that the internal properties of dark matter halos and large-scale cosmic environments may offer powerful constraints on FDM and other alternative dark matter models.

Speaker: Tibor Dome (Institute of Astronomy, Cambridge)

EuCAPT_upload.odp

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12:13 A Bayesian Estimation of the Milky Way’s Circular Velocity Curve using Gaia DR3

The hidden hand of dark matter (DM) shaping the Milky Way remains elusive as the dark substructure of the Galaxy is probed by tracing the dance of celestial bodies in the cosmic shadows. In our work, we exploit the increase of volume and precision in data brought about by ongoing large-scale stellar surveys and use approximately 1.6 million Red Giant Branch stars from Gaia DR3. We present a novel Bayesian inference approach to estimate the circular velocity curve of the Milky Way along with uncertainties that account for various sources of systematic uncertainty as our methodology provides a self-consistent way to quantify uncertainties in the Sun’s Galactocentric distance and the spatial-kinematic morphology of the tracer stars. In addition to estimating the circular velocity curve within a range of 5 to 15 kpc, we also infer the DM mass within 15 kpc and predict the local spherically-averaged DM density.

Speaker: Sven Põder (National Institute of Chemical Physics and Biophysics (EE))

MW_Curve_Poder.pdf

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12:20 Smoking-Gun Signatures for Indirect Detection from Bound State Formation of Electroweak Multiplets

Electroweak multiplets, i.e. $n$-plets which are colour singlets and are charged under the $SU(2)$ gauge group of the Standard Model, are the prototype of WIMP Dark Matter (DM). The phenomenology of these candidates is significantly affected by two non-perturbative effects: Sommerfeld enhancement and bound states formation (BSF). While the former has been the focus of many studies, the latter has received very little attention in the literature. However, BSF in an extremely promising effect for indirect detection DM searches: this effect implies the emission of photons with energies of $O(100 \ \text{GeV})$ which lead to a distinct line in the spectrum of the gamma-ray flux arising from the DM annihilation, in addition to a hard line in the multi-TeV range, at an energy $E \sim M_\text{DM}$. The lines due to BSF are particularly prominent in the photon fluxes of multiplets with $n>5$, and their correlation with the hard photon lines with $E \sim M_\text{DM}$ are clear smoking-gun signatures which can allow to test the theory with an unprecedented confidence level. In this talk, we show how this feature of the model is especially relevant in galaxy clusters, where the large relative velocity of the annihilating DM particles enhances the effect of the line, and how this can be used to potentially discover or rule out this class of candidates with the upcoming CTA telescope.

Speaker: Giovanni Armando (University of Pisa and INFN)

EuCAPT_Talk_Armando.pdf

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12:30 → 14:00 Lunch Break

14:00 → 15:30 Particle Astrophysics

Convener: Pasquale Serpico

14:00 Stellar Probes of Feebly Interacting Particles, Circa 2023

Stellar observables have often been shown to be powerful probes in searches for Feebly interacting particles (FIPs), such as axions, scalars, dark photons, and majorons. In this talk, I will summarize some of the most recent developments, with a focus on supernovae and astrophysical transients.

Speaker: Edoardo Vitagliano

Edoardo Vitagliano.pdf

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14:30 Particle emission from pulsars

Speaker: Silvia Manconi

Manconi_Eucapt_310523_v2.pdf

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15:00 Multimessenger astrophysics with high-energy neutrinos

Speaker: Prof. Foteini Oikonomou (NTNU)

EuCAPT_Oikonomou.pdf

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15:30 → 16:15 Coffee Break

16:15 → 17:00 Particle Astrophysics

Convener: Pasquale Serpico

16:15 Impact of Neutrino Decay on the Cosmic Neutrino Background

In this work, we explore the consequences of neutrino decay facilitated by a neutral scalar on possible cosmic neutrino background (CνB) detection in the future, especially in the PTOLEMY experiment. We analyze the distortion of the expected event spectrum as a function of the singlet mass and Yukawa couplings, and we consider both a three-neutrino scenario and a scenario with an extra sterile neutrino.

Speaker: Leonardo Jose Ferreira Leite (University of Campinas UNICAMP (BR))

Eucapt presentation-Leonardo.pdf

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16:22 A First Look at Sky Anosotripies of High-Energy Neutrino Flavours

Lorentz invariance is a pillar symmetry of the Standard Model. Yet, it may be violated in proposed extensions, inducing preference for particular directions in the propagation of particles. This type of Lorentz-invariance violation (LIV) is difficult to test. Fortunately, high-energy astrophysical neutrinos, with TeV–PeV energies and cosmological-scale baselines, provide us with a unique opportunity to do so; by looking for the differences in the distribution of arrival directions of neutrinos of different flavours. Using 7.5 years of IceCube High Energy Starting Events, we model a flavour-dependent spherical harmonic expansion of the neutrino flux and ground our predictions in realistic detector simulations. Further, we forecast the near-future reach of current and upcoming neutrino telescopes to constrain and detect these flavour anisotropies. Our work reaffirms the power of high-energy astrophysical neutrinos to probe fundamental physics, and stresses the need do so while accounting for theoretical and experimental nuance.

Speaker: Bernanda Telalovic (Niels Bohr Institute)

EuCAPT2023_presentation_BernandaTelalovic.pdf

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16:29 Dark Sectors and MiniBooNE Low Energy Excess

The aim of this presentation is to introduce a dark extension of the SM that communicates to it through three portals: neutrino, vector and scalar mixing, by which it could be possible to explain the Low Energy Excess (LEE) at MiniBooNE. In the model, Heavy Neutral leptons are produced by upscattering via a dark photon, with masses around 10 MeV – 2 GeV, and subsequently decay into an electron-positron pair and neutrinos. If sufficiently collimated or asymmetric in energy, these events can be detected as a single shower and explain the MiniBooNE LEE. We show how the model can well reconstruct the energy spectrum. We consider two cases: 3 ν + 1 HNL and 3 ν + 2 HNLs.

Speaker: Jaime Hoefken Zink

DS and MB LEE, EuCAPT.pdf

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16:36 Space Plasma Instabilities Resolve GeV-TeV Tension and Constrain Light Axions

TeV blazars dominate the extragalactic gamma-ray sky and highly energetic pair beams arising from such blazar jets underproduce gamma rays in the GeV band while inverse-Compton scattering off the cosmic microwave background. Recent Fermi-LAT isotropic gamma-ray background measurements suggest that space plasma instabilities can play a crucial role in alleviating this GeV-TeV tension by transferring energy from the active galactic nucleus into the intergalactic medium. A direct consequence of such instability losses is the modification of thermal history and suppression of power at late times, potentially holding a clue towards resolving the small-scale crisis in cosmology. We show that the observation of dwarf galaxies and Lyman-alpha measurements can narrow down the mass range for light axion-like particles in a blazar-heated universe.

Speaker: Oindrila Ghosh (Stockholm University & the Oskar Klein Centre)

Oindrila_Ghosh_EuCAPT2023.pdf

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16:43 The origin of ANITA-IV events from the sinergies with IceCube

Recently, the ANITA collaboration announced the detection of new, unsettling Ultra-High-Energy (UHE) events. Understanding their origin is pressing to ensure success of the incoming UHE neutrino program.
In this talk, I will discuss the ANITA-IV events in contrast with the lack of observations in the IceCube Neutrino Observatory. I will introduce a general framework to study the compatibility between these two observatories both in the SM and Beyond Standard Model (BSM) scenarios.
Finally, I will discuss the constraints on BSM and highlight the importance of simultaneous observations by high-energy optical neutrino telescopes and new, UHE detectors to uncover cosmogenic neutrinos or discover new physics.

Speaker: Antoni Bertólez-Martínez (Departament de Física Quàntica i Astrofísica, Universitat de Barcelona)

ANITA_origin_IceCube.pdf

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16:50 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 more conventional production from cosmic-ray (CR) interactions. Tentative observations of cosmic-ray 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 flux from both astrophysical and standard dark matter annihilation models from combined fits to high-precision antiproton data as well as cosmic-ray nuclei measurements (B, Be, Li). Astrophysical sources are capable of producing $\mathcal{O}(1)$ antideuteron events and $\mathcal{O}(0.1)$ anti-helium 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. Finally, we discuss that the 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

EUCAPT_DelaTorreLuque.pdf

EUCAPT_DelaTorreLuque.pptx

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17:00 → 17:15 EuCAPT: message from the director

Convener: Gianfranco Bertone

17:00 EuCAPT: message from the director

Speaker: Gianfranco Bertone

EuCAPT_Symposium 2023 2.pdf

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17:15 → 18:10 EuCAPT Highlights

Conveners: Alvise Raccanelli (Universita e INFN, Padova (IT)), Anne Green, Emanuela Dimastrogiovanni (The University of New South Wales), Francesca Calore (Unite Reseaux du CNRS (FR)), Gabriela Barenboim (IFIC & University of Valencia), Giuseppe Fanizza (University of Lisbon), Laura Bernard (CNRS), Dr Matteo Fasiello (Institute of Cosmology and Gravitation), Ms Nikolina Šarčević (Newcastle University), Silvia Pascoli (Universita e INFN, Bologna (IT)), Valerie Domcke (CERN)

EuCAPT task force presentations.pdf

17:15 Community Building Task Force

Speaker: Laura Bernard

EuCAPT task force presentations.pdf

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17:20 Funding Opportunities Task Force

Speaker: Gabriela Barenboim (IFIC & University of Valencia)

funding.pdf

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17:25 Governance/Elections Task Force

Speaker: Francesca Calore (CNRS, LAPTh)

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17:30 Training Task Force

Speaker: Ema Dimastrogiovanni (The University of Groningen)

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17:35 Symposium Task Force

Speaker: Valerie Domcke (CERN)

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17:40 Workshop Task Force

Speaker: Matteo Fasiello (IFT Madrid)

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17:45 Website Task Force

Speaker: Nikolina Šarčević (Newcastle University)

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17:50 Outreach Task Force

Speaker: Silvia Pascoli (Universita e INFN, Bologna (IT))

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17:55 Collaborative Projects Task Force

Speaker: Alvise Raccanelli (University of Padova)

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18:00 Newsletter Task Force

Speaker: Giuseppe Fanizza (IA - Lisbon)

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18:05 Colloquia Task Force

Speaker: Anne Green

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18:15 → 20:15 Reception & Posters

Thursday 1 June

09:30 → 10:30 Early Universe

Convener: Silvia Pascoli

09:30 Warm Inflation

Speaker: Mehrdad Mirbabayi

Mirbabayi_Eucapt_Jun2023.pdf

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10:00 Charting the baryogenesis landscape

Speaker: Julia Harz

EuCAPT2023_Harz.pdf

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10:30 → 11:15 Coffee Break

11:15 → 12:30 Early Universe

Convener: Silvia Pascoli

11:15 Primordial black hole formation

Speaker: Ville Vaskonen

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Vaskonen_EuCAPT23_PBHformation.pdf

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11:45 Robust constraints on the primordial spectrum from DM mini halos and the CMB anisotropies

Although the CMB and galaxy surveys provide precise measurements of the primordial power spectrum at large scales, the small-scale power spectrum remains largely unconstrained. An enhancement in the small-scale primordial spectrum can lead to the formation of Ultra-Compact-Mini-Halos (UCMH) much earlier than standard halo can form. As a result, the DM annihilation signal receives a boost than can strongly impact the CMB power spectra. In this talk, I briefly discuss how to model the effect of s- and p-wave annihilations in UCMHs onto the CMB. I quantify the impact of late-time halo mergers using excursion set theory, and argue that the associated uncertainty in the boost of energy injection is limited for the CMB, but can have serious consequences for late time probes (i.e. for the 21-cm signal). Finally, I demonstrate that the derived CMB constraints on the amplitude of the small-scale spectrum are competitive with those coming from gamma-ray observations, even for p-wave processes.

Speaker: Guillermo Franco Abellán

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Talk_EuCAPT_guillermo.pdf

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11:52 Gravity as a Portal to Reheating, Leptogenesis and Dark Matter

We show that a minimal scenario, utilizing only the graviton as an intermediate messenger between the inflaton, the dark sector and the Standard Model (SM), is able to generate simultaneously the observed relic density of dark matter (DM), the baryon asymmetry through leptogenesis, as well as a sufficiently hot thermal bath after inflation. The possibility of reheating via minimal gravitational interactions has been excluded by constraints on dark radiation for excessive gravitational waves produced from inflation. We thus extend the minimal model in several ways: i) we consider non-minimal gravitational couplings; ii) we propose an explanation for the PeV excess observed by IceCube when the DM has a direct but small Yukawa coupling to the SM; and iii) we also propose a novel scenario, where the gravitational production of DM is a two-step process, first through the production of two scalars, which then decay to fermionic DM final states. In this case, the absence of a helicity suppression enhances the production of DM and baryon asymmetry, and allows a great range for the parameters including a dark matter mass below an MeV where dark matter warmness can be observable by cosmic 21-cm lines, even when gravitational interactions are responsible for reheating. We also show that detectable primordial gravitational wave signals provide the opportunity to probe this scenario for $T_\text{rh}< 5\times 10^6$ GeV in future experiments, such as BBO, DECIGO, CE and ET.

Speaker: Basabendu Barman

eucapt23_Barman.pdf

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11:59 The Cosmological Flow : a Systematic Approach to Primordial Correlators

Correlation functions of primordial density fluctuations provide an exciting probe of the physics governing the earliest moments of our Universe. However, the standard approach to compute them is technically challenging. Theoretical predictions are therefore available only in restricted classes of theories, which can completely bias the interpretation of data.

In this talk, I will present the cosmological flow: a complete method to systematically compute tree-level primordial correlators in any theory, bypassing the intricacies of Feynman diagram computations. This framework enables one to capture all effects—including e.g. the imprints of additional particles and breaking scale-invariance—for the reason that it relies on following the time evolution of these correlators from the initial quantum vacuum state to the end of inflation. I will then demonstrate the power of this approach by exposing new results in various classes of inflationary models that are difficult to track analytically, such as the strongly mixed regime of the cosmological collider—a robust probe of the field content of inflation—that requires a non-perturbative treatment of quadratic mixings.

Speaker: Denis Werth

EuCAPT2023_Werth.pdf

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12:06 Real scalar phase transitions: bubble nucleation, nonperturbatively

In the Standard Model the electroweak phase transition is a crossover, but in many beyond the Standard Model theories the transition is of first order. Strong first order phase transitions could produce gravitational waves that might be detectable by the Laser Interferometer Space Antenna (LISA). Perturbation theory is commonly used to estimate the parameters that enter the calculation of gravitational wave spectra. However, perturbation theory is known to run into the infrared problem in the regime we are interested in and furthermore it is important to test the reliability of existing results. Here I will discuss our recent results where we studied a real singlet scalar model with a tree level potential barrier and performed nonperturbative simulations to determine the bubble nucleation rate. Our preliminary results show that higher orders in perturbation theory are necessary, and we expect our findings to allow calibration of the systematic uncertainty in perturbative results.

Speaker: Anna Kormu

EuCAPT-Kormu-final.pdf

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12:13 Dissipative effects during inflation

Introducing an energy transfer between the inflaton field and a thermal bath modifies the primordial power spectrum $\mathcal{P}_\mathcal{R}$ due to the thermal fluctuations acting as a stochastic source for the curvature perturbations. We propose a fast and accurate method to compute $\mathcal{P}_\mathcal{R}$ in this context based on the Fokker-Planck equation, and verify its consistency with a Montecarlo stochastic approach and a fully analytical approximation. We apply these techniques to two different scenarios: 1. Warm inflation, for which we compute the inflationary CMB observables of several models. We find that some models currently ruled out become compatible with experimental constraints when taking dissipation into account. 2. Inflation with a transient dissipative phase, for which we compute the enhancement in the abundance of asteroid-mass primordial black holes (which are dark matter candidates) and the corresponding peak in the primordial gravitational wave background.

Speaker: Alejandro Perez Rodriguez (Universidad Autonoma de Madrid)

dissipative_APR.pdf

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12:20 Reheating dynamics of dark sectors

As the nature of dark matter remains unresolved, existence of a whole dark sector is an intriguing possibility. It is also natural to assume that such dark sector couples to inflationary dynamics. As an example, we consider the case of warm axion inflation coupled to a non-Abelian dark sector, both in weakly and strongly coupled regime. We show that this simple setup provides rich phenomenology, possibly with interesting gravitational wave signatures.

Speaker: Helena Kolesova (Institute for Theoretical Physics, University of Bern)

EuCAPT_Kolesova_pdf.pdf

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12:30 → 14:00 Lunch Break

14:00 → 15:00 Late Universe

Convener: Camille Bonvin

14:00 Do we understand the growth of structure over cosmic time? A CMB Lensing Story

Speaker: Mathew Madhavacheril

CMB_Lensing_CERN_Madhavacheril-2.pdf

Do we understand the growth of structure over cosmic time? A CMB Lensing Story

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14:30 The Large-Scale Structure of the Universe

It is expected that measurements of the large-scale structure of the Universe will soon become our leading sources of fundamental cosmological information. In this talk, I will review some of the major progress, both theoretical and data-oriented, that has been made in understanding the physics of galaxy clustering, as well as what we might hope to learn about new physics from these measurements. As a main example, I will discuss our recent analysis of the BOSS galaxy-clustering power spectrum and bispectrum data using the one-loop predictions from the Effective Field Theory of Large-Scale Structure (EFTofLSS), where we find impressive constraints on cosmological parameters. Overall, we find that including higher-order predictions, which allows us to analyze the data to smaller length scales and access more physical modes, significantly reduces the error bars of cosmological parameters. Even with this existing BOSS data, some of our results are competitive with CMB constraints. This points to exciting, even stronger constraints from future surveys such as DESI, Euclid, and MegaMapper, and opens the door to exploring exciting new physics with precision large-scale structure measurements.

Speaker: Matthew Lewandowski

LEWANDOWSKI_cern_2023_v2.pdf

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15:00 → 15:45 Coffee Break

15:45 → 17:00 Late Universe

Convener: Camille Bonvin

15:45 Weak Lensing

Speaker: Alexandra Amon

Alexandra Amon.pdf

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16:15 Probing Axions through Tomography of Anisotropic Cosmic Birefringence

Cosmic birefringence is the in-vacuo rotation of the linear polarization plane experienced by photons of the Cosmic Microwave Background (CMB) radiation when theoretically well-motivated parity-violating extensions of Maxwell electromagnetism are considered. If the angle parametrizing such a rotation is dependent on the photon's direction, then this phenomenon is called Anisotropic Cosmic Birefringence (ACB). We have performed for the first time a tomographic treatment of the ACB, by considering photons emitted both at the recombination and reionization epoch. This allows one to extract additional and complementary information about the physical source of cosmic birefringence concerning the isotropic case. We have focused on the case of an axion-like field $\chi$, whose coupling with the electromagnetic sector induces such a phenomenon, by using an analytical and numerical approach (which involves a modification of the CLASS code). We have found that the anisotropic component of cosmic birefringence exhibits a peculiar behaviour: an increase of the axion mass implies an enhancement of the anisotropic amplitude, allowing to probe a wider range of masses with respect to the purely isotropic case. Moreover, we have shown that at large angular scales, the interplay between the reionization and recombination contributions to ACB is sensitive to the axion mass, so that at sufficiently low multipoles, for sufficiently light masses, the reionization contribution overtakes the recombination one, making the tomographic approach to cosmic birefringence a promising tool for investigating the properties of this axion-like field.

Speaker: Alessandro Greco

GRECO_BIREFRINGENCE.pdf

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16:22 Extracting Cluster Information from small-scale CMB

The weak gravitation lensing of the Cosmic Microwave Background
(CMB) [1] rows a wealth of information about the late-time universe in the
CMB data we observe through ground-based and space-based telescopes.
In this talk, I propose a method to probe Galaxy-cluster mass profiles
from the lensing signature of CMB in arcmin scales. In the first part, I
describe how a theoretical halo model [2] for a cluster gives rise to lensing
signatures in the observed CMB. In the second part, I discuss how we are
developing a method based on Maximum a posterior (MAP) estimator [3]
of lensing potential to recover the cluster mass. Such an estimator will be
influential in light of low noise level experiments like CMB S4.

References
[1] A. Lewis and A. Challinor, Weak gravitational lensing of the CMB, Phys.
Rept. 429 (2006) 1 [astro-ph/0601594].
[2] J.F. Navarro, C.S. Frenk and S.D.M. White, The Structure of cold dark
matter halos, Astrophys. J. 462 (1996) 563 [astro-ph/9508025].
[3] J. Carron and A. Lewis, Maximum a posteriori CMB lensing
reconstruction, Phys. Rev. D 96 (2017) 063510 [1704.08230].

Speaker: Sayan Saha (Indian Institute of Science Education and Research (IISER), Pune)

EuCAPT_sayan_updated.pdf

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16:29 Modelling of Astrophysical Systematics for Cosmology with LSST

LSST will provide an unprecedented wealth of astronomical data, with which we will be able to tightly constrain the values of the cosmological parameters, notably those which describe the poorly understood dark energy component. As weak lensing and galaxy clustering measurements provide a way to infer key cosmological quantities such as the dark matter distribution, the evolution of cosmic structure, and the expansion history of the Universe, detailed and rigorous analysis is necessary in order to glean as much information as possible from LSST measurements of these effects. This project developed a consistent and reliable framework (FISK) where three key systematic effects impacting weak lensing and galaxy clustering (intrinsic alignment of galaxies, galaxy bias and photometric redshift uncertainties) are modeled jointly. The results directly enable rigorous weak lensing and galaxy clustering constraints on cosmological parameters with LSST.

Speaker: Ms Nikolina Šarčević (Newcastle University)

Nikolina Šarčević.pdf

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16:36 Reliable and resource preserving emulation for Bayesian model inference

As a result of the observed discrepancies within the $\Lambda \mathrm{CDM}$ model, a lot of work is being done to reconcile the observations from the early and late universe with new cosmological models. The resulting model testing is often based on inference algorithms that depend on a large number of computationally intensive simulations that conclude in large computational efforts.

In our work we show that it is possible to substantially reduce the number of computations by emulating the simulation and interpolating between individual simulations. We demonstrate this by emulating the widely used linearized Boltzmann Einstein solver $\mathrm{CLASS}$ utilizing cosmology inspired neural networks. This intuition of the underlying physical effects allows us to keep the network sizes shallow and lightweight which results in fast evaluation and training. Additionally we use dynamic switching between the emulator and the full simulation to keep the used parameter range of the emulator as narrow as possible, still remaining accurate in the most relevant parameter region. This results in small training sets and ,thus, a faster adoption and training of this emulator for new models of interest. The code with example scripts on usage is publicly available under the name $\mathrm{CLASSNET}$.

Speaker: Sven Günther (RWTH Aachen University)

EuCAPT_talk_Guenther_final.pdf

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16:43 Antisymmetric galaxy cross-correlations

Galaxies are biased tracers of the underlying dark matter density field. If we work with a single tracer, its two-point function will be symmetric under exchange of the pair of galaxies under consideration. But if we look at two different tracers, then in principle their cross-correlation could be not symmetric (Dai et al. 2016). This locally antisymmetric signal arises naturally when the two tracers have different bias parameters, and it could provide additional information with respect to the standard power-spectrum, both on the clustering and on initial conditions. I will present the basic formalism, then build on it to add redshift space distortions and primordial non-Gaussianity. Finally, I present a way to build an estimator for this signal and to get an estimate of the signal-to-noise.

Speaker: Eleonora Vanzan (Università degli Studi di Padova)

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Slides_antisymmetric.pdf

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16:50 The Dipole of the Pantheon+SH0ES Data

We determine the dipole in the Pantheon+ data. We find that, while its amplitude roughly agrees with the dipole found in the cosmic microwave background which is attributed to the motion of the solar system with respect to the cosmic rest frame, the direction is different at very high significance. While the amplitude depends on the lower redshift cutoff, the direction is quite stable. For redshift cuts of order $z_{\rm cut} \simeq 0.05$ and higher, the dipole is no longer detected with high statistical significant. An important rôle seems to be played by the redshift corrections for peculiar velocities.

Speaker: Francesco Sorrenti (University of Geneva)

dipole_presentation_eucapt.pdf

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17:00 → 18:00 Visit of CERN Experiments

Friday 2 June

09:30 → 10:30 Gravitational Waves

Convener: Daniele Steer

09:30 Probing gravity with gravitational waves

Speaker: Jose Maria Ezquiaga Bravo

Jose Maria Ezquiaga Bravo.pdf

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10:00 Stochastic gravitational waves from cosmological phase transitions

Speaker: Jorinde van de Vis

GWsJvdVis.pdf

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10:30 → 11:15 Coffee Break

11:15 → 12:30 Gravitational Waves

Convener: Daniele Steer

11:15 Probing New Physics with Pulsar Timing Arrays

Speaker: Andrea Mitridate

mitridate_eucapt_23.pdf

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11:45 Testing Grand Unified Theories with gravitational waves and proton decay

We consider a minimal non-supersymmetric SO(10) Grand Unified Theory (GUT) model that can reproduce the observed fermionic masses and mixing parameters of the Standard Model. We calculate the scales of spontaneous symmetry breaking from the GUT to the Standard Model gauge group using two-loop renormalisation group equations. This procedure determines the proton decay rate and the scale of U(1)_B-L breaking, which generates cosmic strings and the right-handed neutrino mass scales. Consequently, the regions of parameter space where thermal leptogenesis is viable are identified and correlated with the fermion masses and mixing, the neutrinoless double beta decay rate, the proton decay rate, and the gravitational wave signal resulting from the network of cosmic strings. We demonstrate that this framework, which can explain the Standard Model fermion masses and mixing and the observed baryon asymmetry, will be highly constrained by the next generation of gravitational wave detectors and neutrino oscillation experiments which will also constrain the proton lifetime.

Speaker: LUCA MARSILI (IPPP, University of Durham)

Eucapt_2023(1).pptx

Eucapt_2023-2.pdf

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11:52 A new universal property of cosmological gravitational wave anisotropies

The anisotropies of the stochastic gravitational wave background, as produced in the early phases of cosmological evolution, can act as a key probe of the primordial universe particle content. We point out a universal property of gravitational wave anisotropies of cosmological origin: for adiabatic initial conditions, their angular power spectrum is insensitive to the equation of state of the cosmic fluid driving the expansion before BBN. Any deviation from this universal behaviour points to the presence of non-adiabatic sources of primordial fluctuations. In this work we prove this general result, and we illustrate its consequences for a representative realisation of initial conditions based on the curvaton scenario. In the case of the simplest curvaton setup, we also find a fourfould enhancement in the cross-correlation between gravitational wave anisotropies and the CMB temperature fluctuations, vis-à-vis the purely adiabatic scenario.

Speaker: Ameek Malhotra

Malhotra_Eucapt.pdf

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11:59 Searching for Primordial Black Holes with the Einstein Telescope

Primordial Black Holes (PBH) have attracted much attention in the last years as they may explain some of the LIGO/Virgo/KAGRA observations and significantly contribute to the dark matter in our universe.

The third generation of ground-based gravitational wave detectors will have the unique opportunity to set stringent bounds on this putative population of objects.

Focusing on the Einstein Telescope (ET), we will explore how well we could observe key quantities, that would allow us to discover and/or constrain a population of PBH mergers, from high redshifts to subsolar masses. We will also present the results of a population analysis, with a mass and redshift distribution compatible with the current observational bounds. The exquisite level of accuracy attainable on the considered observables will be shown, as well as the potential ET has to observe tens to thousands of PBH binary mergers per year.

Speaker: Mr Francesco Iacovelli (Universite de Geneve (CH))

Iacovelli_EuCAPT_2023.pdf

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12:06 The impact of gravitational wave memory in constraining binary black holes parameters

Besides the transient effect, the passage of a gravitational wave also causes a persistent displacement in the relative position of an interferometer's test masses through the "nonlinear memory effect".
This effect is generated by the gravitational backreaction of the waves themselves and encodes additional information about the source.
In this talk, we present the implications of using this information for the parameter estimation of massive binary black holes with LISA.
The main focus is the potential breaking of the degeneracy between the inclination and luminosity distance of the source and the latest forecast for the detectability of the memory for an astrophysical population of massive binary black holes.

Speaker: Silvia Gasparotto (IFAE)

GW_memory_talk.pdf

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12:13 EC(H)Os in the dark: Gravitational Wave backgrounds from colliding ECOs at atom interferometers

Long baseline atom interferometers (LBAI) offer an exciting opportunity to explore mid-frequency gravitational waves. In this talk I will advocate for targeting the total 'gravitational wave background', surveying the landscape of possible contributions within this frequency band. I will demonstrate that the cumulative signal from the inspirals of the LIGO-Virgo stellar-mass binaries is well within reach of typical terrestrial LBAI and may have much to reveal about the Universe. Finally, I will show that populations of dark sector exotic compact objects harbouring just a tiny fraction of the dark energy density, could generate signatures unique to mid- and low-frequency gravitational wave detectors, providing a novel means to probe complexity in the dark sector.

Speaker: Hannah Banks

EucaptEC(H)Os from ECOs.pdf

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12:20 Cosmological history of the HEFT

Effective Field Theories (EFTs) are crucial for new physics searches in the electroweak sector. They are a model-independent framework which can be used to classify the low-energy effects of heavy, new physics on experimental results which deviate from the standard model prediction. For this reason, the Standard Model Effective Field Theory (SMEFT), where the Higgs doublet transforms linearly under electroweak symmetry, has gained recent popularity. However, the SMEFT is not as general an EFT as the Higgs EFT (HEFT), where the Higgs doublet transforms non-linearly. The universe, as always, is reluctant to reveal it's secrets: is it SMEFT or HEFT/SMEFT? Particle colliders will certainly shed some light on this dichotomy, yet they can only probe near the vacuum. We turn instead to cosmology, specifically the gravitational waves that may have been produced in an early universe phase transition, and could provide us with a lens with which to resolve the SMEFT or HEFT/SMEFT dichotomy, and the nature of electroweak symmetry breaking.

Speaker: MIA,ROBIN,BYRON WEST

EUCAPT Talk Final.pdf

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12:30 → 14:00 Lunch Break

14:30 → 15:15 EuCAPT Discussion & Coffee

15:15 → 15:45 Prize Ceremony & Closing

15:15 Prize Ceremony and Closing

Speaker: Valerie Domcke (CERN)

EuCAPT_closing.pdf

EuCAPT Prizes.pdf

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