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# Cosmology 2018 in Dubrovnik

Europe/Zagreb
Dubrovnik, Croatia

#### Dubrovnik, Croatia

Hotel Kompas
Description

Cosmology offers today one of the most important frontiers of physics. The mystery of dark matter and puzzle of dark energy are still outstanding.  On the observational side there is an exponential growth of accurate and important data, and they will help in establishing the new needed theories.

In this conference we plan to bring together researchers from the observational, computer simulation and theoretical sides working in cosmology, astrophysics and astroparticle physics, to discuss the current situation as well as  prospects for the future improvements.

All the topics will be discussed from different angles starting from the booming flow of observational data. The topics to be discussed will include:

1. DM (Theory, Observations, Detection)
2. Structures in the Universe
3. New observational probes of the Universe
4. Multimessenger cosmology (Gravitational waves, Cosmic rays, Neutrinos)
5. Unknown physics in the Universe

A number of invited talks from leading scientists as well as many contributed ones from participants will be presented.

The conference will take place in a conductive atmosphere, appropriate for the dramatic paradigm shift that we may be witnessing in these days.

The conference is supported by the H2020 project n. 692194 RBI-T-WINNING.

A conference fee of 200Eur is required: it covers Coffee Breaks, Lunches, Gala dinner.

Additional support for accommodation of contributing speakers will be available in a limited number of cases.

### Scientific Organizing Committee (SOC)

• Pasquale Blasi
• Marina Cobal
• Christopher Conselice
• Angela di Virgilio
• Nicolao Fornengo
• Katherine Freese
• Carlos Frenk
• Paolo Gondolo
• Ruth Lazkoz
• Sabino Matarrese
• Joseph Silk
• Volker Springel
• Francesco Villante
• V. Gammaldi (scientific secretariat)
• Fabrizio Nesti, Paolo Salucci (chairs)

### Local Organizing Committee (LOC)

• O Antipin
• C. Di Paolo
• G. Sharma
• F. Nesti
• P. Salucci
• V. Gammaldi

Registration
Registration
Participants
• Alain Asokeng
• Alberto Zucchetta
• Alen Klimenta
• Alison Elliot
• Alma Gonzalez
• Angela Di Virgilio
• Anna De Graaff
• Annalisa Pillepich
• Barbara Patricelli
• Carlo Baccigalupi
• Carlos Frenk
• Carmelo Evoli
• Chiara Di Paolo
• Christian Arnold
• Daniel Nieto
• Daniele Bertacca
• Emmanuel Saridakis
• Enrico Garaldi
• Erik Aquino-Ortíz
• Fabrizio Nesti
• Florian Kuhnel
• Francesco Calura
• Gauri Sharma
• Gerry Gilmore
• Giovanni Tambalo
• Go Ogiya
• Goran Jelic-Cizmek
• Indranil Banik
• Jarah Evslin
• Joaquin Gonzalez-Nuevo
• John Heise
• Jose Cembranos
• Joseph Kuruvilla
• Kamil Danek
• Keiko Nagao
• Konstantinos Migkas
• Luca Visinelli
• Manel Ouafi
• Marina Cobal
• Marius Cautun
• Mark Vogelsberger
• Martin Moyano
• Martina Gerbino
• Massimiliano Lattanzi
• Michal Karamazov
• Miguel Sánchez-Conde
• Mikolaj Grzedzielski
• Mohamed Rameez
• Monika Biernacka
• Motonari Tonegawa
• Nicola Menci
• Nicola Turini
• Noemi Zabari
• Oleg Antipin
• Paolo Panci
• Paolo Salucci
• Phillip Helbig
• Piero Ullio
• Raffaele Pascale
• Robert Monjo
• Stefano Camera
• Takeshi Kobayashi
• Thomas Lacroix
• Thorsten Glüsenkamp
• Thorsten Naab
• Victoria Yankelevich
• Viviana Gammaldi
• Wim De Boer
• Wojciech Hellwing
Contact
• Monday, 22 October
• 08:30 09:30
Registrations from 8:30 1h
• 09:30 13:10
Opening and Morning session
• 09:30
Opening 20m
• 09:50
Galaxy Formation Simulations: Illustris, IllustrisTNG and Beyond 40m

Cosmological simulations of galaxy formation have evolved significantly over the last years. In my talk I will describe recent efforts to model the large-scale distribution of galaxies with cosmological hydrodynamics simulations. I will focus on the Illustris simulation, and our new simulation campaign, the IllustrisTNG project. After demonstrating the success of these simulations in terms of reproducing an enormous amount of observational data, I will also talk about their limitations and directions for further improvements over the next couple of years.

Speaker: Mark Vogelsberger
• 10:30
Is the FERMI GeV Excess a Dark Matter Signal? 30m

The Fermi GeV excess of diffuse gamma-rays is observed as a shift in the maximum in the spectrum (weighted by the energy squared) from below 1 GeV to about 2 GeV and can be explained either by a new source with a spectrum peaking at 2 GeV or a suppression of gamma-rays below 2 GeV. As new sources dark matter annihilation or millisecond pulsars have been proposed. In this paper we compare these hypotheses with the alternative of a suppression of gamma-rays below 2 GeV, as has been observed in molecular clouds. The different hypotheses can be distinguished by the gamma-ray spectrum and the morphology of the excess. We find that the suppression of gamma-rays below 2 GeV in molecular clouds is the clear winner. The origin of the apparent suppression of low energy gamma-rays in molecular clouds is not clear, but most likely a combination of energy losses, suppressed propagation of cosmic rays into molecular clouds and detector effects related to the limited angular resolution below a few GeV.

Speaker: Wim De Boer (KIT - Karlsruhe Institute of Technology (DE))
• 11:00
Coffee Break 30m
• 11:30
Gaia - prospects for Dark Matter 40m
Speaker: Gerard Gilmore (Cambridge University)
• 12:10
The search for dark matter halo substructure with gamma rays 30m

A natural consequence of the hierarchical structure formation scenario in LCDM is that it predicts abundant substructure (or subhalos) inside larger halos, i.e. galaxies like ours. The most massive of these subhalos host the known dwarf satellite galaxies, while smaller subhalos may host no stars/gas at all and thus may not possess astrophysical counterparts. Yet, if dark matter (DM) particles are weakly interacting massive particles (WIMPs), we expect these “dark satellites” to emit gamma rays that can be detected with current or planned gamma-ray experiments like the Fermi LAT or the future Cherenkov telescope array (CTA). Indeed, hundreds of Fermi-LAT sources remain unidentified and there is the exciting possibility that some of these unidentified sources are subhalos simply awaiting a proper classification. A careful scrutiny of these sources can be made that takes into account both our best knowledge of the subhalo population and of the properties of the expected DM signal. In this talk, I will summarize the current status of such subhalo searches, paying particular attention to the most recent Fermi-LAT analyses. I will also show how this kind of search can yield very competitive limits on the nature of the DM particle, particularly in the absence of potential subhalo candidates in gamma-ray catalogs. These limits are comparable to the best constraints in the field so far.

Speaker: Dr Miguel Sánchez-Conde (IFT UAM/CSIC)
• 12:40
Scalar field (a.k.a Ultra light axion) DM in dSph's and some aspects of structure formation. 30m

I will discuss about the status of constraints for Scalar Field DM models arising from dwarf spheroidal kinematics. As well as about the differences, in the structure formation process, between the free scalar field and the self-interacting one, endowed with a trigonometric potential, that can help to avoid the constraints set by the Lyman-alpha forest and the dSph's kinematics.

Speaker: Dr Alma Gonzalez (Universidad de Guanajuato)
• 13:10 15:30
Lunch break 2h 20m
• 15:30 18:35
Afternoon session
• 15:30
Discrimination of Dark Matter Velocity Distribution by Directional Detection 30m

Existence of anisotropic component in dark matter velocity distribution has been pointed out by N-body simulation and observations. We study the possibility to discriminate isotropic and anisotropic distributions with directional direct detection of dark matter.

Speaker: Dr Keiko Nagao (National Institute of Technology, Niihama College)
• 16:00
Constraints on the Nature of Dark Matter from the Abundance of Galaxies 30m

We show how the abundance and the properties of dwarf galaxies can set tight constraints on Warm Dark Matter (WDM) models. We consider both thermal relics and sterile neutrino (with different production mechanisms) as possible candidates for the WDM, and show that the observed number density of faint (M_UV = -12) high-redshift (z= 6) lensed galaxies in the field provides an unprecedented probe for the mass m_X of thermal relic candidates independently of baryonic physics, as well as strong constraints on the parameter space of sterile neutrino dark matter models. We show that competitive baryon-independent constraints on such models can also be obtained from the abundance of satellite ultra-faint dwarf in nearby galaxy clusters, and that this method has the potentiality for appreciable improvements with next observations.

Speaker: Dr Nicola Menci (INAF-Oservatorio Astronomico di Roma)
• 16:30
Dynamical models of the dwarf spheroidal galaxies Fornax 30m

In the standard Λ cold dark matter (ΛCDM) cosmological model, dwarf galaxies are considered the building blocks of the most massive galaxies, so a knowledge of their properties is required to understand the processes that drive galaxy formation. Among dwarf galaxies, the local dwarf spheroidal galaxies (dSphs) are known to be hosted in massive and extended dark halos, usually dominating the stellar components even in the central parts. dSphs almost completely lack mission in bands other than the optical, so they are natural locations at which to look for high-energy signals from annihilating or decaying dark-matter particles. These facts make dSphs ideal laboratories in which to study dark matter and to test cosmology on the smallest scales, where there is potential tension between the observational data and the predictions of the ΛCDM model. I present new dynamical models of dwarf spheroidal galaxies (dSphs) in which both the stellar component and the dark halo are described by analytic distribution functions that depend on the action integrals. In their most general form these distribution functions can represent axisymmetric and possibly rotating stellar systems. I model the Fornax dSph, limiting for simplicity, to the non rotating, spherical case. The models are compared with state-of-the-art spectroscopic and photometric observations of Fornax, exploiting the knowledge of the line-of-sight velocity distribution of the models, using measures of individual stars, and accounting for the foreground contamination from the Milky Way. The model that best fits the structural and kinematic properties of Fornax has a cored dark halo, with a large core in the inner parts of the dark halo density distribution. The stellar velocity distribution is isotropic almost over the full radial range covered by the spectroscopic data and slightly radially anisotropic in the outskirts of the stellar distribution. The dark-matter annihilation J-factor and decay D-factor, useful tool to employ in the search for inderect dark matter signals, have also been computed. This cored halo model of Fornax is preferred, with high statistical significance, to both models with a Navarro, Frenk and White dark halo and simple mass-follows-light models.

Speaker: Dr Pascale Raffaele (DIFA, dipartimento di fisica e astronomia, Bologna )
• 17:00
Coffee Break 30m
• 17:30
Young stellar populations and other probes of dark matter 30m

We use a semi-analytic galaxy formation model and consider various observables which can be used as valuable probes for uncovering the nature of dark matter. Among them, we show how the properties of young stellar populations in the local Universe can be used as a particularly valuable cosmological test. We discuss how future facilities can help us supporting standard lambda cold dark matter or alternative dark matter models.

Speaker: Dr Francesco Calura (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna )
• 18:00
Testing modified gravity with cosmic voids 30m

Modifications to General Relativity on cosmological scales offer an intriguing explanation for the accelerated expansion of the Universe. The modifications to gravity are sourced by an extra scalar field, which gives rise to a fifth force that enhances structure formation. The additional force is negligible in high density regions, however it can attain maximum values in underdense regions and thus voids are a very promising venue to test modified gravity models. I will present the physics of voids in these theories and will discuss which voids observables are the most promising for testing the models. The fifth forces enhances the outflow of mass from voids and thus voids in modified gravity models are more underdense than their General Relativity analogues. This is manifested in the weak lensing signal by voids, which is larger in models with a fifth force. Such deviations will be measured by upcoming lensing surveys such as Euclid and LSST, and provide a new avenue for testing modified gravity theories.

Speaker: Marius Cautun (Institute for Computational Cosmology, Durham University )
• 19:00 20:00
Reception 1h
• Tuesday, 23 October
• 09:20 13:10
Morning session
• 09:20
Recent Results from the IceCube collaboration 40m
Speaker: Thorsten Glüsenkamp (Universität Erlangen-Nürnberg)
• 10:00
IllustrisTNG: the new frontier to understand the co-evolution of (cold) dark matter and galaxies with cosmological simulations of structure formation 30m

I will describe the numerical efforts to simulate galaxies with the moving-mesh code AREPO across an unprecedented range of halo masses, environments, evolutionary stages and cosmic times. In particular, I will focus on the IllustrisTNG project (www.tng-project.org), a series of three gravity+magnetohydrodynamics cosmological volumes (50, 100, 300 Mpc a side, respectively) in a LCDM cosmology that are capable of both resolving the inner structures of galaxies as small as the classical dwarfs of the Milky Way, as well as of sampling the large scale structure of the Universe with thousands among groups and clusters of galaxies. I will briefly explain what is explicitly and empirically solved in gravity+magnetohydrodynamics simulations for galaxy formation in a cosmological context and what is required and what it means to “successfully” reproduce populations of galaxies which resemble the real ones. I will therefore show novel insights allowed by the new simulations, ranging from the assembly of the most massive structures in the Universe to the coevolution of galaxies and their black holes. I will hence focus on a series of results to highlight how baryonic physics and feedback mechanisms can affect our “standard" theoretical expectations for the distribution of dark matter on large scales and within galaxies.

Speaker: Dr Annalisa Pillepich (MPIA Heidelberg)
• 10:30
Bounds on Dark Matter Annihilations from 21-cm data 30m

In March 2018 the EDGES experiment has reported the discovery of an absorption feature in the 21-cm spectrum at redshift around 17. This measurement, if confirmed, is fundamental because can give us information about the epoch of reionization soon after the formation of first stars and galaxies. This talk is organised in three parts. In the first part I’ll present the EDGES experiment and the procedure the collaboration has used to extract the broad absorption profile from the strong galactic synchrotron emission. Then I’ll review the physics of the 21-cm line and the history of the InterGalactic Medium (IGM) properties assuming a LambdaCDM Universe. Finally, I’ll conclude with a simple application of this measurement to set bounds on the Dark Matter (DM) properties. In particular, annihilating DM particles produce significant heating of the IGM erasing the absorption feature measured by EDGES. These limits, derived for the first time in our paper, are comparable to the strongest ones from all other observables.

Speaker: Dr Paolo Panci (CERN)
• 11:00
Coffee Break 30m
• 11:30
Dark matter heats up in dwarf galaxies 40m

Pure dark matter structure formation simulations in LCDM predict that dwarf galaxies should inhabit dark matter halos that have steeply rising central density “cusps”. However, observations of nearby dwarf irregulars favour instead constant density dark matter “cores”. Many solutions to this cusp-core problem have been proposed, from modifications to the nature of dark matter to dark matter being kinematically “heated up” by bursty star formation. In this talk, I present the first observational evidence for dark matter being heated up at the centres of nearby dwarf galaxies due to baryonic processes. I show that the inner dark matter density of these dwarfs is anti-correlated with their star formation histories. Dwarfs that have undergone a Hubble time of star formation have a lower central density than those whose star formation shut down long ago. This result is challenging to understand in theories that attempt to solve the cusp-core problem by modifying dark matter or the cosmological model, because these theories predict that dark matter cores should be ubiquitous. Our results suggest that dark matter is, to a good approximation, a cold, collisionless fluid that can be heated up and moved around.

Speakers: Prof. Justin Read (University of Surrey ), Justin Read (University of Surrey)
• 12:10
Dark Matter limits from dwarf satellites (TBC) 30m
Speaker: Piero Ullio
• 12:40
The LIGER method: light-cone using GR 30m

We introduce a method to create mock galaxy catalogs in redshift space including all gen- eral relativistic effects to linear order in the cosmological perturbations. We dub our method LIGER, a short for ‘light cones with general relativity’. LIGER takes a (N-body or hydrody- namic) Newtonian simulation as an input and outputs the distribution of galaxies in comoving redshift space. This result is achieved making use of a coordinate transformation and simulta- neously accounting for lensing magnification. The calculation includes both local corrections and terms that have been integrated along the line of sight. Our fast implementation allows the production of many realizations that can be used to forecast the performance of forthcom- ing wide-angle surveys and to estimate the covariance matrix of the observables. To facilitate this use, we also present a variant of LIGER designed for large-volume simulations with low mass resolution. In this case, the galaxy distribution on large scales is obtained biasing the matter-density field. Finally, we present two sample applications of LIGER. First, we dis- cuss the impact of magnification bias onto the angular clustering of galaxies in a Euclid-like survey. Second, we show that Doppler redshift-space distortions beyond the standard Kaiser effect can be detected with high statistical significance using the completed Square Kilometre Array.

Speaker: Daniele Bertacca (Dipartimento di Fisica e Astronomia "Galileo Galilei" Universita' degli Studi di Padova via Marzolo 8, I-35131 Padova, Italy )
• 13:10 15:30
Lunch break 2h 20m
• 15:30 19:00
Afternoon session
• 15:30
Primordial Black Holes as Dark Matter 30m
Speaker: Dr Florian Kuhnel (KTH Stockholm)
• 16:00
Why and how should we test (theory of) gravity on cosmological scales? 30m

The GR is over 100 years old. The beautiful Einstein's relativity theory of space-time and gravity is one of the founding block of modern physics and cosmology in particular. In my talk, I shall discuss why one would like (and actually really need) to design and convey tests of the theory on cosmological scales. Then, I will also present a handful of theories (called Modified Gravity) that aim to rival the ruling of GR at the cosmological distances. Finally, I will present and discuss some reasonable ways for conveying cosmological test of gravity, discuss why most of them might fail and present some potentially promising avenues for new class of such tests. Concluding with why you might want to stay tuned for future in that field!

Speaker: Dr Wojciech Hellwing (Center for Theoretical Physics of Polish Academy od Sciences )
• 16:30
Evolution of tidally stripped dark matter subhalos 30m

The mass of cosmic structures, such as galaxies and galaxy clusters as well as their surrounding dark matter (DM) halos, is a key quantity to characterize themselves. In the scenario of the hierarchical structure formation in the Universe, mergers between them are one of the main drivers for their mass evolution. Various physical mechanisms non-linearly couple with each other and work all together in the merging process. Cosmological N-body simulations have been utilized as the primal tool to investigate the complicated processes of the formation and evolution of DM halos and had tremendous success in reproducing the observations of the cosmic large scale structures. However, van den Bosch (2017) suggested that DM subhalos are artificially disrupted in current state-of-the-art cosmological simulations. This has been actually discussed as the over-merging problem in the past. We call up the classical problem. First, we analytically study various physical mechanisms which may disrupt subhalos and find that they cannot explain the subhalo disruptions in cosmological simulations. Secondly, using a large set of controlled N-body simulations varying numerical parameters, we identify two mechanisms for the artificial disruptions, relating to the spatial and mass resolutions of the simulations, and find two criteria to assess the reliability of the mass evolution of subhalos in the simulations. Thirdly, we make the empirical models for the mass and structural evolution of tidally stripped subhalos using simulations, satisfying the criteria. We will also present galaxy merger simulations, reproducing the observation of the ultra diffuse galaxy of the significant DM mass deficit.

Speaker: Ogiya Go (Observatoire de la Côte d'Azur )
• 17:00
Coffee Break 30m
• 17:30
Dark Matter and Mediators investigated with jets at LHC 30m

The presence of a non-baryonic dark matter component in the Universe is inferred from the observation of its gravitational interaction. If dark matter interacts weakly with the Standard Model it would be produced at the LHC, escaping the detector and leaving a large missing transverse momentum as their signature. The experiments at the LHC have developed a broad and systematic search program for dark matter production in proton-proton collisions. The results of the searches for dark matter along with jets done with 13 TeV data will be presented.

Speaker: Alison Elliot (Queen Mary University of London (GB))
• 18:00
The effect of scalar meson interactions on symmetry energy in RMFT. 30m

An extension of the standard RMF theory by including interaction between sigma and delta mesons is proposed. The first-order and second-order interaction between those mesons is calculated separately. It is shown that in both cases that the symmetry energy Esym can be diminished to some extent in the specific range of baryon density. However, for the second-order interaction Esym can take even negative values for low enough coupling constant. Current work includes implementing those results into TOV equation. The neutron stars with a mass in the range 1.8- 2.3 M☉ were obtained.

Speaker: Mrs Noemi Zabari (Institute of Nuclear Physics, Polish Academy of Sciences )
• Wednesday, 24 October
• 09:20 13:10
Morning session
• 09:20
Search for invisible particles at LHC. 40m

I will review all the searches for invisible particle at the LHC. From the standard missing momentum and energy to the more sophisticated methods with forward spectrometers as PPS at CMS and AFP at Atlas.

Speaker: Nicola Turini (INFN Sezione di Pisa, Universita' e Scuola Normale Superiore, P)
• 10:00
The kinematic signatures of AGN and black holes on massive galaxies 30m

I will present recent results from high-resolution cosmological zoom simulations and detailed merger simulations on observational kinematic signatures originating from the effect of feedback from supermassive black holes and their merging. We show that most observed stellar kinematical signatures of massive galaxies originate from the impact of supermassive black holes in a cosmological context.

Speaker: Dr Naab Thorsten (Max-Planck-Institute for Astrophysics )
• 10:30
Associated production of Dark Matter and Heavy Quarks at LHC 30m

In certain models beyond the standard model, the production of Dark Matter in association to heavy flavored quarks represents a privileged channel for a discovery. The LHC experiments have now analyzed a significant amount of Run-II data, publishing significant advancements in final states involving Dark Matter and one or two top or bottom quarks, or bottom quarks from the Higgs boson decays (mono-Higgs).

Speaker: Alberto Zucchetta (Universitaet Zuerich (CH))
• 11:00
Coffee Break 30m
• 11:30
Cosmology and fundamental physics with Euclid and the SKA 40m
Speaker: Stefano Camera (University of Torino, INFN and INAF )
• 12:10
Cosmological constraints on non-standard neutrino interactions 30m

Cosmological observations are a powerful probe of neutrino physics. In particular, they can be used to investigate the possibility that neutrinos have interactions beyond the standard model of particle physics, like those that emerge in dynamical realizations of the see-saw mechanism for neutrino mass generation (i.e., Majoron models). In my talk I will present constraints on the strength of neutrino interactions from the most recent cosmological data. I will also discuss the possibility of having such "secret" interactions together with a light sterile neutrino, in relation to the anomalies observed in short-baseline flavour oscillation experiments.

Speaker: Massimiliano Lattanzi (INFN - National Institute for Nuclear Physics)
• 12:40
Sub-mm Galaxies Magnification Bias 30m

An unambiguous manifestation of the magnification bias is the cross-correlation between two source samples with non-overlapping redshift distributions. In this talk I will present a couple of examples of measured cross-correlation signals using a background sample of H-ATLAS galaxies (SMGs) with photometric redshifts 􏰁 >1.2. The SMGs characteristics help to boost the sensitivity improving the statistics and allowing us to split the lens sample in different redshift bins to perform a tomographic analysis. Altogether, these promising results suggest the SMGs Magnification Bias as a new interesting tool for studying the mass distribution inside/around the lenses.

Speaker: Joaquin Gonzalez-Nuevo (Universidad de Oviedo, Spain)
• 13:10 15:30
Lunch break 2h 20m
• 15:30 17:30
Afternoon session
• 15:30
Cosmological information in the redshift-space bispectrum 30m

We use the Fisher-matrix formalism to investigate whether the galaxy bispectrum in redshift space contains additional cosmological information with respect to the power spectrum alone. In this talk we present detailed forecasts for a Euclid-like survey and consider cosmological models dominated by dark energy and cold dark matter with Gaussian primordial perturbations. Our study shows that there is a clear advantage in combining the power spectrum and the bispectrum to infer the galaxy bias parameters and constraining the dark-energy equation of state. Also it investigates how the bispectrum depends on the orientation of wavevector triangles with respect to the line of sight. Finally we discuss how results depend on the binning strategy for the clustering statistics as well as on the maximum wavenumber.

Speaker: Victoria Yankelevich (Argelander-Institut für Astronomie, University of Bonn)
• 16:00
The Radial Acceleration Relation of satellite galaxies: a test for dark matter and MOND 30m

The Radial Acceleration Relation (RAR) has recently emerged as a challenge to the LambdaCDM cosmological model and possibly as an evidence of new physics, most notably of Modified Newtonian Dynamics (MOND). Satellite galaxies represent an intriguing laboratory for testing these theories, since in MOND they are affected by the external field effect, that has no analogous in LambdaCDM. I will present the first-ever predictions of the RAR for LambdaCDM satellite galaxies, its evolution with redshift, and its dependence on other satellite properties. I will then compare these results with available data and show that both LambdaCDM and MOND fail to reproduce the observed RAR in this regime. Finally, I will illustrate a new test that exploits the results aforementioned to discriminate between the LambdaCDM and MOND theories and discuss its feasibility in the light of upcoming data.

Speaker: Mr Enrico Garaldi (University of Bonn )
• 16:30
Testing Gravity with wide binary stars like α Centauri 30m

This talk describes a novel way to test the hypothesis that gravity does not follow the standard Newton/Einstein model at low accelerations. This MOND hypothesis (Milgrom 1983) correctly predicted that astronomers would find a very tight correlation between the internal acceleration within galaxies calculated according to standard physics (visible mass + Newtonian gravity) and that inferred kinematically e.g. from rotation curves. This has recently been confirmed across a huge range in galaxy properties, including morphological type (Lelli+ 2017). Thanks to GAIA, it will soon be possible to perform a novel and almost direct test of MOND. This will involve the orbital velocities of wide binary stars separated by ~3-20 kAU. In MOND, the orbital velocities in the Solar neighbourhood are typically ~20% higher than in Newtonian gravity despite the external field effect (EFE) from the rest of the Galaxy, which I carefully include in my calculations (Banik+ 2018). As a result, the velocity distribution of wide binaries would extend to values that are infeasible in Newtonian gravity. MOND has a greater effect without the EFE, but this is unlikely on theoretical grounds. I consider a number of systematic issues that could hamper this test. Recently ionised systems are not likely to be very problematic as sufficiently strong encounters with passing stars and molecular clouds should be rare. The presence of an additional low-mass companion to one of the stars is expected to be the most serious issue. If not directly detectable, its presence can still be inferred from the resulting astrometric and/or radial velocity acceleration of the affected star, which greatly exceeds (~1000x) that due to genuine wide binary orbital motion.

Speaker: Dr Indranil Banik (Bonn University )
• 17:00
Coffee Break 30m
• 17:30 19:30
Tour 2h
• 20:10 22:10
Social Dinner 2h
• Thursday, 25 October
• 09:20 13:10
Morning session
• 09:20
The small-scale structure of the Universe as a conclusive test of CDM 40m

I will discuss the status of the LCDM cosmological model and propose a new test that can unambiguously distinguish cold dark matter from other dark matter candidates such as warm dark matter. This test could potentially rule the standard model.

Speaker: Prof. Carlos Frenk (United Kingdom )
• 10:00
Searching for inflationary gravitational waves in the CMB polarization: from Planck to B-mode experiments 30m

We review the recent constraints on the primordial tensor to scalar ratio from the combination of Planck and operating CMB polarization experiments. We discuss the present and future B-mode observations and the expectations for early Universe, neutrino masses and dark energy.

Speaker: Carlo Baccigalupi (SISSA)
• 10:30
Recent Results in Galactic Cosmic Ray Physics and Their Interpretation 30m

The latest years have been dense with new developments in the search for the sources of Galactic cosmic rays (CRs): 1) The detection of features in the spectra of some primary chemicals opened new questions on the propagation of CRs in the Galaxy. 2) Precise measurements by AMS-02 of secondary nuclei are providing unique information about the transport processes over a larger energy domain 3) Gamma-rays data by FERMI-LAT revealed an unexpected radial dependence of the gamma-rays emissivity induced by interactions of CRs with the interstellar medium. For the first time, models about the galactic distribution of CR factories, as well as about the CR propagation throughout the Galaxy, can be severely tested against local and not-local observations. Additionally, understanding the feedback of low-energy CRs on interstellar chemistry in our Galaxy can provide unique insights on the physics of galaxy formation and evolution.

Speaker: Dr Carmelo Evoli (Gran Sasso Science Institute)
• 11:00
Coffee Break 30m
• 11:30
Ultralight Dark Matter 40m

Ultralight bosons constitute well motivated dark matter (DM) candidates. The most popular candidates being the axion-like particles (ALPs) with very small masses typically arising in string theory. In this scenario, the uncertainty principle prevents the formation of structures on small scales. Indeed, if DM is made of very light particles, the corresponding number density is so high that the interparticle separation becomes smaller than the Compton wavelength so that a field description of DM would be possible. As a matter of fact, at the background level, massive bosons can be described by coherently oscillating classical fields whose average energy density precisely scales as cold DM. Moreover, the effect on perturbations of the ultralight fields can also be understood easily since the de Broglie wavelength can be of astrophysical size. It implies that it is not possible to localize the DM particle on scales smaller than the de Broglie and structure formation is suppressed on those small scales. We will review these ideas and the main phenomenology of scalar, vector and tensor ultralight DM.

• 12:10
The Radial Acceleration Relation (RAR): is it really universal? 30m

McGaugh et al. (2016) have found, in a large sample of disc systems, a tight nonlinear relationship between the radial gravitational acceleration (g) and its baryonic component (gb). They claim the universality of such relation in any galaxy and at any radius. This is of difficult understanding in a standard “DM + Newtonian” scenario. Anyway, trough a recent investigation (Di Paolo & Salucci) on the Low Surface Brightness (LSB) and Dwarf Discs galaxies, I found that the McGaugh et al. relationship breaks down, i.e. it is not really universal. Furthermore, I found that a more complex relation exists among g, gb and also an additional variable: the normalised galactic radius r/R_opt. This is the direct consequence of the baryonic + DM distribution in galaxies. Moreover, I showed that the McGaugh et al. relation can be interpreted only as a limit of our complex relation when we consider galactic radii larger than the stellar disc scale length.

Speaker: Chiara Di Paolo (SISSA)
• 12:40
A search for missing baryons with the Sunyaev-Zel'dovich effect 30m

Observations of galaxies and galaxy clusters in the local universe cannot account for the total baryon content inferred from measurements of the cosmic microwave background and from big bang nucleosynthesis [1,2]. Locating the missing baryons has been one of the major challenges in cosmology. Cosmological simulations predict that they are spread throughout filamentary structures in the cosmic web, forming the warm-hot intergalactic medium (WHIM) [3]. Large observational searches have resulted in a few detections of the WHIM [4], but there was no clear picture of the large-scale extent of this gas. I will present the recent detection of the WHIM in stacked large-scale filaments through the thermal Sunyaev-Zel’dovich effect [5]. This result establishes the presence of diffuse ionised gas in large-scale filaments, and suggests that the missing baryons problem may be resolved via observations of the cosmic web.

Speaker: Anna De Graaff (Leiden Observatory )
• 13:10 15:30
Lunch break 2h 20m
• 15:30 18:30
Afternoon session
• 15:30
Gravitational Wave Decay into Dark Energy 30m

In this talk I will discuss the decay of gravitational waves into dark energy fluctuations, made possible by the spontaneous breaking of Lorentz invariance due to dark energy. For some operators of the EFT of Dark Energy (or Horndeski/beyond Horndeski theories) this decay process is large. Hence, recent observations rule out such couplings. This constraint, together with the requirement that gravitational waves travel at the speed of light, rules out all quartic and quintic GLPV theories.

Speaker: Mr Giovanni Tambalo (SISSA)
• 16:00
Geometric model of dark energy according to projected hyperconical universes 30m

Using hyperconical universes with linear expansion, radially inhomogeneous metrics can be obtained by local time-preserved transformations. This model tends to a locally flat Friedman-Robertson-Walker metric with linear expansion. The corresponding luminosity distance was obtained and compared with the observations of 580 SNe Ia, taken from the Supernova Cosmology Project (SCP). The best fit of the hyperconical model obtains $\chi_0^2 = 562$, the same value that the standard $\Lambda$CDM model. Choosing a radially distorted stereographic projection and taking regional (second order) equality between the Hubble parameter obtained from both models, it is predicted that the dark energy density is $\Omega_{\Lambda} = 0.6937181(2)$.

Speaker: Dr Robert Monjo (Department of Algebra, Geometry and Topology, Complutense University of Madrid )
• 16:30
The generation of vorticity in cosmological N-body simulations 30m

The evolution of cosmological perturbations, at large scales, is primarily determined by the gravitational clustering of cold dark matter, which has traditionally been modelled as a presureless perfect fluid. At small scales and at late times however, orbit crossing leads to a nonzero velocity dispersion and vorticity in the dark matter distribution, and while several studies of orbit crossing in the context of perturbation theory have been recently presented, a full description is still lacking. The alternative is to numerically investigate the generation of vorticity, and in this work, we've performed N-body simulations using the publicly available relativistic code "gevolution". I will present how the vorticity field is calculated and the convergence studies performed. Finally, I will describe the obtained features of the vorticity power spectra, notably its large and small scale behaviour as well as redshift dependence, and compare it with related work. I will also present some novel results for the power spectra of the velocity dispersion and vector perturbations of the metric.

Speaker: Goran Jelic-Cizmek (Universite de Geneve (CH))
• 17:00
Coffee Break 30m
• 17:30
Testing the isotropy of the Universe with galaxy clusters in X-rays 30m

We introduce a new test to study the cosmological principle with galaxy clusters. Galaxy clusters exhibit a tight correlation between the luminosity and temperature of the X-ray-emitting intracluster medium. While the luminosity measurement depends on cosmological parameters through the luminosity distance, the temperature determination is cosmology-independent. We exploit this property to test the isotropy of the luminosity distance over the full extragalactic sky, through the normalization a of the Lx–T scaling relation and the cosmological parameters Ωm and H0. We use two almost independent galaxy cluster samples: the ASCA Cluster Catalog (ACC) and the XMM Cluster Survey (XCS-DR1). These two samples appear to have the same pattern for H0 with respect to the Galactic longitude. More specifically, we identify one sky region within l ~ (−15°, 90°) that shares very different best-fit values for H0 for both independent samples (~2.7 sigma for both). Several reasons were tested, but none of them was able to significantly alleviate the tension. Finally, the eeHIFLUGCS galaxy cluster sample is introduced and its potential for further testing this apparent anisotropy, is presented.

Speaker: Mr Konstantinos Migkas (University of Bonn )
• 18:00
On the streaming model for redshift-space distortions 30m

Peculiar velocities affects the redshifts of distant galaxies and introduces distortions in all statistical measures of the reconstructed large-scale structure. These distortions can be used to constrain the gravitational theory through clustering statistics. In this talk, we introduce the generalised hyperbolic distribution (GHD) to model the line-of-sight pairwise velocity distribution. We showcase the fidelity of the GHD streaming model by comparing against N-body simulations. With the phenomenological model we have introduced, it paves a way in which the redshift-space correlation function could be utilised to precisely test theories of gravity and interacting dark-energy models for future galaxy surveys like EUCLID.

Speaker: Joseph Kuruvilla
• Friday, 26 October
• 09:20 13:10
Morning session
• 09:20
Ring-laser and fundamental physics 40m

GINGER (Gyroscopes IN General Relativity) is a proposal aiming at measuring the Lense-Thirring effect with an experiment based on Earth. It utilises an array of ring lasers, which are the most sensitive inertial sensors to measure the angular rotation rate of the Earth. This experiment is Earth based, it is well known that Lense Thirring tests are currently done with space experiment, but the earth based one provides the measurement at a certain latitude and the map of the gravity field is unnecessary. The interdisciplinary nature of this experiment will be outlined, with particular attention to the dark matter search.

Speaker: Angela Di Virgilio
• 10:00
Neutrino properties from Cosmology` 30m

The presence of a cosmic background of relic neutrinos is a robust prediction of the standard cosmological model. A direct detection is extremely difficult and still lacking. Nevertheless cosmological observations are a powerful probe of neutrino properties, and cosmological bounds on neutrino masses and number are in agreement with both theoretical predictions and laboratory searches. In this talk, I will briefly review the basics of neutrino cosmology. I will then focus on current cosmological limits on neutrino properties, and show the prospects from next-generation surveys.

Speaker: Martina Gerbino
• 10:30
To B or not to B: Primordial magnetic fields from Weyl anomaly 30m

For more than twenty years, it has been argued that the Weyl anomaly of quantum electrodynamics sources cosmological magnetic fields in the early universe. If true, this would be a natural way to produce the seed magnetic fields of our universe within the Standard Model. In this talk, I will examine this long-standing claim and show that there is actually no production of coherent magnetic fields from the Weyl anomaly, irrespective of the number of massless charged particles in the early universe.

Speaker: Dr Takeshi Kobayashi (ICTP)
• 11:00
Coffee Break 30m
• 11:30
Gravitational waves and Multi-messenger astronomy: the new exploration of the Universe 40m

The era of Gravitational Wave (GW) Astronomy started in 2015, with the first observation of GWs from the merger of a binary black hole system. Two years later, the detection of GWs from a binary neutron star merger and of its electromagnetic counterpart marked the birth of multi-messenger astronomy, opening a new chapter in the study of the universe. This talk will give an overview of the first scientific results of Advanced LIGO and Virgo and discuss what we learned from the first multi-messenger observations.

Speaker: Barbara Patricelli
• 12:10
Dark matter searches in the very-high-energy gamma-ray band: can deep learning help? 30m

Ground-based gamma-ray telescopes based on the imaging atmospheric Cherenkov technique (IACTs) are one of our best tools to access the very-high-energy (few tens of GeV and above) gamma-ray sky. Consequently, these instruments have the capability to offer observations in this particular energy band that may hint at the answers of some of the most pressing questions in Cosmology, like that of the nature of the dark matter. For instance, if one assumes that dark matter particles with masses larger than a few tens of GeV produce gamma-ray signatures in their annihilation or decay, IACTs become excellent detectors of indirect signatures of such a hypothetical particles. The performance of these telescopes turned into dark matter detectors is strongly affected by our ability to reconstruct the properties of the primary particle that originates the extended atmospheric showers that are imaged by the telescopes: this particle reconstruction enables us to classify gamma-ray events from the much more frequent background of cosmic-ray events. In this contribution we will briefly review the state-of-the-art of dark matter searches with IACTs and discuss prospects for what the incoming Cherenkov Telescope Array, the next-generation gamma-ray observatory, may offer us in the near future. We will finalize arguing how deep learning can help us with the reconstruction of CTA events, thus potentially improving its sensitivity to dark matter signatures.

• 12:40
Simple self-consistent prediction methods for the phase space of dark matter: from galactic dynamics to phenomenology 30m

In the context of dark matter (DM) searches, it is crucial to quantify and reduce theoretical uncertainties affecting predictions of observables that depend on the DM velocity distribution, including event rates in direct searches, velocity-dependent annihilation rates, and microlensing event rates for DM compact objects. The well-known Eddington inversion formalism for the self- consistent reconstruction of the isotropic DM phase-space distribution from a galactic mass model allows one to go beyond the simplistic Maxwell-Boltzmann approximation or direct extrapolations from cosmological simulations, with limited technicalities. However, this method and its anisotropic extensions can be ill-defined depending on the DM and baryonic content of the galaxy of interest. In this presentation, I will first discuss the validity range of the Eddington inversion methods from a theoretical perspective, as well as issues relevant to DM searches. Then, even in their theoretical validity range, these methods must be tested against hydrodynamical cosmological simulations to assess their relevance for complex gravitational systems such as Milky-Way-like galaxies. I will therefore discuss the predictivity of these methods based on zoom simulations. As an application, I will also present novel constraints on p-wave suppressed DM annihilation from positron data, and their associated theoretical uncertainties.

Speaker: Thomas Lacroix (Institut d'Astrophysique de Paris (IAP))
• 13:10 15:30
Lunch break 2h 20m
• 15:30 18:30
Afternoon session
• 15:30
Simulating galaxy formation with the Illustris-TNG model in f(R) modified gravity 30m

The question on the nature of gravity and dark energy is one of the fundamental problems in modern cosmology. f(R) gravity is a viable alternative to general relativity (GR) with a cosmological constant and can therefore be used to test GR over a large range of scales. Simulations of cosmic structure formation in this model thus deliver crucial information on how possible deviations from GR might be observable in upcoming surveys such as Euclid, DESI or LSST. The simulations I will present in this talk are dedicated to study the interplay between baryonic feedback and modified gravity, two processes which both have a significant effect on the matter clustering and the matter power spectrum. They for the first time include both a full physics hydrodynamical model and modified gravity in one simulation at a time. The simulations were carried out with the AREPO cosmological simulation code and its new modified gravity solver which allows to solve the f(R) gravity equations in full non-linearity and to fully capture the effects of the chameleon screening mechanism. The baryonic physics are simulated employing the Illustris-TNG hydrodynamical model in the code which incorporates magnetohydrodynamics, star- and black hole formation, supernova- and AGN feedback, metal advection and galactic winds. In this talk I will present detailed study of the degeneracy between AGN-feedback and f(R) gravity in the matter power spectrum, results on the impact of f(R) gravity on the stellar and gaseous components of galaxies and on the effects of modified gravity on star formation.

Speaker: Christian Arnold (Durham University )
• 16:00
Kinematic scaling relations of CALIFA and MaNGA galaxies: A dynamical mass proxy for galaxies across the Hubble sequence. 30m

We used gas and stellar kinematics for spatially resolved galaxies from CALIFA and MaNGA surveys with the aim of studying dynamical scaling relations as the Tully&Fisher, Faber&Jackson and also a combination of them through the SK parameter defined as SK^2=KVrot^2+disp^2. TF and FJ generalized relations (early+late types) present larger dispersions and deviations from the classical ones. When we use the SK parameter all galaxies, regardless of the morphology, lie in the same scaling relation with the scatter smaller or equal to the TF and FJ ones. We interpret this relation as a consequence of the relation between dynamical mass and stellar mass in central regions of galaxies, what implies that the SK parameter is a better proxy of this dynamical mass. We compared our estimations of the dynamical mass based on the SK parameter with results based on more complex dynamical models, finding a good agreement within 0.14dex between both quantities.

Speaker: Dr Erik Aquino-Ortíz (Instituto de Astronomía, UNAM)
• 16:30
Coffee Break 30m
• 17:00
Giant Monopole Dark Matter 30m

Halo sized magnetic monopoles are automatically cored, have universal profiles and have a minimum mass given by Dirac quantization which can resolve the missing satellites problem. In addition they can possess spikes which can seed supermassive black hole growth. The Kibble mechanism lets them form just in time for structure formation. The main challenge is the screening of the intermonopole repulsion.

Speaker: Jarah Evslin (I)
• 17:30
Testing the Cosmological Principle 30m

The dipolar anisotropy of the CMB is believed to be due to our motion with respect to the CMB rest frame at 369 km/s. This should cause a dipolar modulation in the number counts of distant sources, through special relativistic aberration and Doppler boosting effects. We construct an all-sky catalogue of ~60000 radio galaxies, by combining the NRAO VLA Sky Survey (NVSS) and Sydney University Molonglo Sky Survey (SUMSS) catalogues and find a significantly larger dipole than expected, in the same direction but with a velocity of 1355 +/- 174 km/s, in tension with the kinematic interpretation of the CMB dipole at 2.81σ. As the significance is limited by shot noise due to a catalogue of finite size, we examine a catalogue of ~2.4 million galaxies, observed by the Widefield Infrared Survey Explorer (WISE) satellite. After suppressing star contamination and sources at low redshift through innovative use of apparent motion fits and photometry, the dipole in the remaining ~1.2 million sources converges in direction to the CMB dipole, while still favoring a velocity higher than ~1000 km/s. This dipole can be reconciled with the CMB dipole only for a non-Copernican observer situated within a bulk flow greater than 240 km/s on scales exceeding 100 Mpc, which is unexpected in a LambdaCDM universe at a level less than 3%. The deceleration parameter q0 derived from local observations is then expected to show a scale-dependent dipolar modulation. From a maximum likelihood analysis of the Joint Lightcurve Analysis (JLA) catalogue of Type Ia supernovae we do find such a dipole in q0 extending out to z∼0.2, with a magnitude comparable to its monopole. Although not statistically significant in current data, such a dipole must be allowed for, especially in analysing surveys with incomplete sky coverage such as JLA and its successor Pantheon; out of 740 (1048) SNe IA in the JLA (Pantheon) catalogue, 632 (890) are in the hemisphere opposite to the direction of bulk flow for which their redshifts have been corrected. However when we do so, the monopole component of q0, which has been widely ascribed to a cosmological constant (dark energy), drops in statistical significance and becomes consistent with zero at 2σ (95\% c.l.). This suggests that the apparent acceleration of the expansion rate deduced from supernovae may be an artifact of our bulk flow.

Speaker: Mohamed Rameez
• Saturday, 27 October
• 09:20 11:30
Discussion and closing