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Ioannis Gialamas (National Institute of Chemical Physics and Biophysics)
In this talk I will analyse a variety of Euclidean saddles in the gravitational path integral, with asymptotic AdS boundary conditions, in a class of Einstein-Scalar-Maxwell models.
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These include single boundary solutions, usual and wineglass wormholes, as well as more exotic (quasi)-oscillatory saddles. Some of these Euclidean backgrounds can be continued to Lorentzian FRW universes that... -
Georgios Karananas
Strong interactions preserve CP symmetry to extraordinary precision, despite
lacking an obvious reason to do so. The most elegant solution to this `strong
CP puzzle' introduces a new particle---the QCD axion---that dynamically
relaxes CP violation to experimentally acceptable levels. As an added virtue,
the axion can also account for the dark matter in the Universe.In standard...
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Hardi Veermäe (National Institute of Chemical Physics and Biophysics (EE))
Primordial black holes (PBHs) can be tested through various gravitational wave signatures. In this talk I will focus on PBHs formed from critical collapse of large curvature perturbations from single-field inflation and curvaton models, and review the role non-Gaussianity plays for PBHs and the scalar-induced gravitational waves (SIGWs) associated with their formation. Since non-Gaussian...
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Aris Katsis (Crete Center of Theoretical Physics)
A series of turns in field space in models with two inflaton fields can produce a peak in the scalar power spectrum and thus lead to significant abundances of primordial black holes and secondary gravitational waves. An intuitive way to realize this scenario will be presented, based on [JCAP 06 (2025) 010] and [2602.04055 [astro-ph.CO]]. The enhancing mechanism can be very efficient even in...
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Dr Ioannis Dalianis (University of Cyprus)
Gravitational wave astronomy has established a new probe of fundamental physics and of the dark sectror of the universe, with compact-object mergers and emerging evidence for a stochastic gravitational-wave background (SGWB). In parallel, high-energy neutrino observations are providing complementary access to extreme astrophysical environments and particle physics beyond the Standard Model.
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Ahmad Albadawi (Al-Hussein Bin Talal University)
We investigate a Schwarzschild-like black hole embedded in a combined environment consisting of a Dehnen-type dark matter halo and a cloud of strings. We first construct the corresponding composite spacetime metric and examine its geometric properties, including the horizon structure, curvature invariants, and the validity of the classical energy conditions. Subsequently, we explore the...
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Qianhang Ding
The dark matter surrounding black hole would form dense dark environment, studying the imprint of dark matter on the observational signals from black hole via accretions and dynamical friction could be a dark matter probe. In this talk I am going to talk about how to study the nature of dark matter from radio, optics and gravitational wave channels. With these studies, black hole would be a...
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Dr Davide Racco (Universita e INFN Roma Tre (IT))
I will discuss some of the directions in which a Gravitational Wave (GW) background can shed light on fundamental physics and cosmology.
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Model-independent information can be extracted from the low-frequency tail of the spectrum, which is dictated by causality for any primordial GW source active for a finite time (as a phase transition). The causality tail allows to probe the Hubble rate and... -
Peter Tinyakov (Universite Libre de Bruxelles)
Primordial black holes (PBHs) with “asteroid” masses around $10^{20}$ g can be captured by main-sequence stars, accrete the surrounding matter, and destroy the star within a short time. The capture process is efficient only in exceptional environments — namely, dwarf galaxies with the highest dark-matter densities and the lowest velocity dispersions. The capture probability also strongly...
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Masahide Yamaguchi (Institute for Basic Science)
We will discuss cosmological collider physics, with a particular focus on how to extract information about physics beyond the Standard Model (BSM) of particle physics in the current Universe.
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Michele MANCARELLA (Aix-Marseille)
Gravitational-wave standard sirens provide a novel and independent probe of cosmology. By directly measuring luminosity distances to compact binary mergers, they enable measurements of the Hubble constant and offer a way to test General Relativity on cosmological scales through possible modifications of gravitational-wave propagation.
In this talk, I will introduce the basic idea behind...
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Fiorella Burgio (INFN Sezione di Catania)
Cooling of isolated dark-matter-admixed neutron stars is studied in a theoretical framework which includes a realistic nuclear
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equation of state with consistent pairing gaps, together with fermionic dark matter of variable particle mass and dark-matter fraction. Stellar structure equations are solved for the two-fluid system, where the ordinary matter component and dark matter component... -
Marco Cirelli (CNRS LPTHE Jussieu)
I will discuss some recent works on the phenomenology and the detection of particle Dark Matter, both in the sub-GeV regime and in the ultra-heavy (~PeV) regime.
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Antonios Kyriazis
Spontaneous symmetry breaking of global symmetries in the early universe may leave behind topological defects known as cosmic strings. These strings continuously emit the symmetry’s pseudo Nambu-Goldstone boson, which contributes to the dark matter density after it becomes non-relativistic. In the talk, I will discuss the numerical and analytical methods we developed to evaluate the density...
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Samya Roychowdhury
Every neutron star is born in the process of core-collapse supernova explosion that, for a brief moment, reproduces conditions of the early Universe with temperatures $T\sim O(30\rm\,MeV)$. We calculate the production of Dark Matter $\chi$ from the SM particles in such events, SM\,$\to\chi\bar\chi$, for the freeze-in range of couplings, $\alpha_{\rm FI} \sim O(10^{-26}) $, finding that...
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Dr GOUDELIS Andreas (LPCA - Clermont Ferrand)
Freeze-in is a mechanism for cosmic dark matter production which has emerged as an interesting alternative to standard thermal freeze-out. Until recently, freeze-in computations were typically performed assuming that the onset of radiation domination in the Universe occurred at a very high initial ("reheating") temperature. However, if this temperature becomes comparable or smaller than some...
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Florian Niedermann
I will argue that growing tensions in cosmological data point towards new dark sector physics, built on the same fundamental principles that govern the visible sector. Specifically, I will present a scenario in which the dark sector undergoes a symmetry-breaking phase transition in the early Universe, leading to a rapid reheating of the dark sector after Big Bang nucleosynthesis. In this...
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Albert Escrivà (Nagoya University)
We study the dynamics of the collapse of a nonspherical overdense patch during an early matter-dominated era and the associated production of gravitational waves (GWs) using a semirelativistic N-body framework that we develop. The collapsing patch is initialized through a Zel'dovich deformation of a homogeneous sphere and evolved in an Einstein--de Sitter background, while the emitted signal...
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Dr Ville Vaskonen
Cosmological first-order phase transitions may have played a significant role in the generation of the baryon asymmetry, intergalactic magnetic fields, and dark matter, while potentially leaving behind an observable gravitational wave (GW) signal. In this talk, I will present our recent simulations of GW production during phase transitions, focusing on strongly supercooled and slow...
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Boris Betancourt Kamenetskaia (Institute for Basic Science)
A strongly self-interacting component of asymmetric dark matter (DM) particles can form compact dark stars (DSs). These objects have a broad spectrum of masses and radii, with distinct evolution histories from both neutron stars and black holes (BHs). We argue that these differences allow a population of DSs to contribute significantly to the astrophysical merger rate in unique and discernible...
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Dr Miguel Ruben Nebot Gómez (U. of Valencia - IFIC)
It was recently shown that in multi-Higgs models with a CP invariant potential and spontaneous CP violation, despite having free quadratic parameters that could induce a decoupling regime for the new scalars, that possibility cannot be fully realized. Contrary to expectations, there are states with masses that cannot be much larger than the electroweak scale once perturbativity constraints are...
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Riccardo Catena (Chalmers University of Technology, Göteborg, Sweden)
I combine the non-relativistic effective theory of dark matter (DM) - electron interactions with linear response theory to obtain a formalism that fully accounts for screening and collective excitations in DM-induced electronic transition rate calculations for general DM-electron interactions. In the same way that the response of a dielectric material to an external electric field in...
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Jacopo Nava (Vrije Universiteit Brussels)
The nanohertz gravitational-wave (GW) signal observed by pulsar timing arrays may originate from a cosmological first-order phase transition (FOPT) at temperatures of order 100 MeV. This coincidence raises a fundamental question: why this scale? We show that such a PT naturally arises in scenarios where the baryon asymmetry is generated from a dark asymmetry via resonant neutron-dark matter...
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Antonio Racioppi (National Institute of Chemical Physics and Biophysics (EE))
We revisit natural inflation within the framework of metric-affine gravity, considering the impact of a periodic non-minimal coupling between the inflaton and the Nieh-Yan term. Such a term, alone, leads to linear inflation predictions in the strong coupling limit and cannot help to rescue the natural inflation scenario. However, once an analogous non-minimal coupling with the Ricci scalar is...
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Maksym Ovchynnikov (CERN)
In this talk, I discuss how current and upcoming CMB/BBN data can probe new physics in the MeV-era Universe through observables such as $N_{\rm eff}$, primordial helium, and deuterium. I focus on benchmark scenarios including electromagnetic relic decays and late reheating, neutrinophilic decays, and decays into metastable particles such as $\mu,\pi^{\pm},K$, with examples motivated by ALPs,...
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Giacomo Ferrante (Université Libre de Bruxelles (ULB))
The magnetic monopole of a dark sector has been advocated as an appealing dark matter candidate, since its stability naturally follows from topological arguments. I will revisit the computation of the monopole abundance generated by a thermal phase transition, exploring the three regimes where the phase transition is second order, weakly first order, or supercooled. This will allow us to...
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Philipp Schicho (University of Geneva)
The possibility that future gravitational-wave detectors could observe the relic background from a cosmological phase transition has triggered intense progress in the theoretical description of these events. A detection of such a signal would probe energy scales far beyond those accessible to particle colliders, providing insight into fundamental questions about the early Universe, including...
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Antonio Racioppi (National Institute of Chemical Physics and Biophysics (EE))
We propose a new mechanism for inflationary model building in the framework of metric-affine gravity. Such a mechanism involves an inflaton non-minimally coupled with the Holst invariant. If the non-minimal coupling function has a zero point and it is very steep at that same point, the corresponding inflaton kinetic function will feature a quasi-pole behaviour, implying a canonically...
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Dr Takahiro Terada (KMI, Nagoya University)
Recent cosmological observations, including those from the Dark Energy Spectroscopic Instrument (DESI), hint at a dynamical nature of dark energy. Motivated by phenomenological parametrizations of the equation-of-state parameter $w(a)$ with sharp transitional features, we study their realization in quintessence models. In our scenario, the quintessence field begins to oscillate abruptly in...
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Pietro Di Gangi
The XENONnT experiment is a dual-phase xenon time projection chamber (TPC) designed for the direct detection of dark matter, operating at the INFN Laboratori Nazionali del Gran Sasso. With a total liquid xenon mass of 8.6 tonnes and a record-low background, the detector has achieved world-leading sensitivity to rare interactions. The experiment has pushed the exploration of particle dark...
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Dr Theodoros Nakas (Institute for Basic Science)
Recent developments have uncovered a broad class of black hole solutions with scalar hair in shift-symmetric quadratic DHOST theories. In this talk, I will present results from 2310.11919 and 2312.17198, where both singular and regular black hole solutions, with primary and secondary scalar hair, are constructed and analyzed. These configurations exhibit nontrivial scalar profiles that modify...
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Paul Frampton
We discuss an Electromagnetically Accelerating Universe as an al-
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ternative to dark energy. It requires the existence of PEMNS=
Primordial Extremely Massive Naked Singularities which for sim-
plicity we rename as astrons. We discuss how astrons retain their
electric charge in the intergalactic plasma because Debye screening
is ineffective in such a rarified density. We also discuss how... -
Dr P. Frampton
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P. Frampton
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Stefano Anselmi (INFN, Sezione di Padova)
One of the landmarks guiding our understanding of physical cosmology is the large-scale structure, defined as the large scale distributions of galaxies, as observed by galaxy surveys. In this context, the so-called Baryon Acoustic Oscillations, are considered one of the most powerful cosmological probes. They are generally deemed to provide distance measures independent of a specific...
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Francesca Passalacqua (INFN Padova)
The large-scale distribution of galaxies encodes information about acoustic waves that propagated in the primordial baryon–photon plasma, leaving a characteristic feature in the two-point correlation function at scales of order 150 Mpc. By exploiting this feature, a new observable, known as the Linear Point, has been identified and shown to be a powerful cosmological standard ruler.
In...
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Tao LIU
Pulsars are remarkable astronomical tools — both as precise clocks for timing and as sources of polarized light. As clocks, millisecond pulsars have been used since the 1980s to form Pulsar Timing Arrays (PTAs) for detecting nanohertz gravitational waves. As polarized sources, the speaker and his collaborators have proposed constructing a Pulsar Polarization Array (PPA) to explore new...
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Mathias Becker (University of Padova)
We present a new framework (ultra)light dark matter based on a scalar field experiencing boundaries in field space. These boundaries give rise to wallions, excitations whose masses are exponentially suppressed yet radiatively stable. After introducing the basic setup, we will discuss how wallions behave in the early universe, how field-space boundaries can form dynamically, and which probes...
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