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Prof. Edward Hardy (University of Oxford)14/04/2025, 09:30
Axions are a well-motivated candidate for new physics. If the associated Peccei-Quinn symmetry was ever restored after inflation, cosmic strings form and inevitably produce a contribution to the stochastic gravitational wave background. I will discuss the resulting gravitational wave spectrum combining effective field theory with numerical simulations. Additionally, the axions produced by...
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José Ricardo Correia14/04/2025, 10:15
Multiple extensions of the Standard Model of particle physics predict the existence of first order phase transitions occurring in the early Universe, leading to an imprint in the stochastic background of gravitational waves. When the transition occurs at the electroweak scale, this imprint will be in the expected range of LISA.
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In this talk we explore the gravitational wave production of... -
Dr Andreas Mantziris (University of Porto)14/04/2025, 10:30
Our latest study (2407.18845) investigates the possibility of generating gravitational waves (GWs) from a curvature-induced phase transition of a non-minimally coupled scalar field acting as dark matter, with a portal interaction to the Higgs field. This analysis is conducted within a dynamical spacetime framework, specifically during the transition from inflation to kination, while also...
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Daniel Jiménez Aguilar (Tufts University)14/04/2025, 10:45
The collapse of domain wall networks in the early universe could have left observable signatures in the form of gravitational waves and primordial black holes. This motivates a detailed study of the dynamics of these topological defects. In this talk, I will discuss how their effective description can predict singularities in the worldvolume of the walls and how this catastrophic evolution is...
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Clara Winckler14/04/2025, 11:30
A series of symmetry-breaking phase transitions in the early universe is expected to have caused the formation of networks of sheet-like topological defects called domain walls, whose collapse could leave observable imprints in current-day massive non-linear structures. We use the parameter-free version of the velocity-dependent one-scale model to provide an estimate of their decay energy,...
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Ricarda Heilemann14/04/2025, 11:45
Domain walls are the simplest type of topological defects formed at cosmological phase transitions, and one of the most constrained. These analyses typically assume a quartic double well potential, but this model is not fully representative of the range of known or plausible particle physics models. Here we study the cosmological evolution of domain walls in two other classes of potentials....
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Pedro Belo Barbosa (University of Porto)14/04/2025, 12:00
The CVOS model is a thermodynamical framework designed to describe the evolution of a network of current‐carrying cosmic strings, where energy loss due to loop formation is incorporated phenomenologically. In this work, I investigate the stability of these configurations by analytically manipulating and examining the microscopic equations of the model. Subsequently, I analyze the evolution of...
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Francisco Pimenta14/04/2025, 12:15
Cosmic strings arise naturally in both unifying theories and superstring inspired inflation models, in which case the fundamental strings formed in the very early universe may have stretched to macroscopic scales.
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To better understand the underlying physical mechanisms and how the macroscopical properties of such networks evolve, analytical developments are needed. In this work, we have... -
Mr Sergei Mukovnikov (Institute of Astrophysics, Centre for Astrophysics of the University of Porto)14/04/2025, 12:30
Cosmic strings can be produced during phase transitions in the very
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early universe. They are particularly interesting objects since they
emit gravitational waves contributing to the stochastic gravitational
wave background (SGWB). This gives us possibility to connect
gravitational waves experiments to unknown physics scenarios of the very
distant past. In the early stages of cosmic string... -
Dr Artur Alho (CAMGSD-IST)14/04/2025, 14:30
We introduce new simple analytical approximations for quintessence solutions covering both tracking (asymptotically inverse power-law potentials) and thawing slow-roll models. From an observational perspective the remarkable accuracy of the approximations makes numerical calculations superfluous when assessing observational constraints. We will then discuss ongoing work on generalisations for...
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Paulo Alexandre Gomes Monteiro (Center for Astrophysics, University of Porto)14/04/2025, 14:45
The wide range of modified gravity theories proposed to address the limitations of General Relativity (GR) presents a challenge in distinguishing between them. In particular, the Geometric Trinity of Gravity - comprising General Relativity, based on curvature; Teleparallel Gravity, which relies on torsion and Symmetric Teleparallel Gravity, which is formulated in terms of nonmetricity- are...
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Anna-Lena Gschrey, Carolina Coelho14/04/2025, 15:00
The canonical cosmological model to explain the recent acceleration of the universe relies on a cosmological constant, and most dynamical dark energy and modified gravity model alternatives are based on scalar fields. Still, further alternatives are possible. One of these involves vector fields: under certain conditions, they can lead to accelerating universes while preserving large-scale...
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ANDREA TROST (University of Trieste)14/04/2025, 15:15
The elusive cosmological redshift drift — predicted by General Relativity as a direct signature of the universe's accelerated expansion — remains one of the most ambitious goals in observational cosmology. In this study, we take the first steps toward detecting this effect using the Lyman-α forest of bright quasars as tracers of the expanding cosmos. Focusing on the brightest quasar,...
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Ana Mafalda Vieira (Faculdade de Ciências da Universidade de Lisboa)14/04/2025, 15:30
There has been recent interest in the cosmological consequences of energy-momentum-powered-gravity models, in which the matter side of Einstein’s equations includes a term proportional to some power, n, of the energy-momentum tensor, in addition to the canonical linear term. Previous works have suggested that these models can lead to a recent accelerating universe without a cosmological...
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Miguel Barroso Varela14/04/2025, 15:45
We analyse the late-time cosmological effects of a modified theory of gravity with a non-minimal coupling between curvature and matter. By evolving the cosmological parameters that match the cosmic microwave background data until their values from direct late-time measurements, we will show how to obtain an agreement between different experimental methods without disrupting their individual...
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Dr Robert Monjo (University of Alcalá)14/04/2025, 16:00
This work explores the viability of Hyperconical Modified Gravity (HMG) as a relativistic alternative to the Modified Newtonian Dynamics (MOND) in explaining the dynamics of galaxy clusters, radial accelerations and galaxy rotation curves. By using five datasets (including high-resolution X-ray data and weak-lensing observations), we test HMG's predictions for hydrostatic equilibrium in galaxy...
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Guglielmo Frittoli (Università Roma Tor Vergata)14/04/2025, 16:45
The accelerated expansion of the Universe is canonically attributed to the Dark Energy (DE), encapsulated in the Lambda factor in the Einstein field equations of gravity, but its nature is still not understood. While observations supply strong evidence in favor of the standard model of cosmology Lambda-CDM, a plethora of different modified gravity models (MG) can still arise and describe...
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Mr Jorge Enrique García-Farieta (Universidad de Córdoba)14/04/2025, 17:00
The next generation of galaxy surveys will provide unprecedented data, leading to accurate tests of gravity on cosmological scales. To fully exploit the nonlinear information encoded in the large-scale structure of the Universe, we propose to leverage cutting-edge deep learning algorithms, such as diffusion models, to efficiently generate 3D density fields conditioned on cosmological...
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Adam Kaczmarek (Jan Długosz University in Częstochowa, Poland)14/04/2025, 17:15
The $f(\mathcal{G},T)$ theory of gravity is recast in terms of the $\phi$ and $\psi$ fields within the scalar-tensor formulation, where $\mathcal{G}$ is the Gauss-Bonnet term and $T$ denotes the trace of the energy-momentum tensor. The general aspects of the introduced reformulation are discussed and the reconstruction of the cosmological scenarios is presented, focusing on the so-called...
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Prof. Ernesto Nungesser (UPM)14/04/2025, 17:30
I will present expansions of the metric and its derivative near a conformal gauge singularity (also known as isotropic singularities) for Bianchi I symmetric massless solutions of the Einstein-Vlasov and Einstein-Boltzmann system with a magnetic field. We will discuss how this can be related to our universe. This is work in collaboration with Ho Lee, John Stalker and Paul Tod.
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Minahil Adil Butt14/04/2025, 17:45
We perform a stacking analysis of galaxy cluster velocity phase space using the caustic technique. By stacking 128 clusters, we create four robust stacked clusters with excellent agreement between caustic masses and binned medians. We model the gravitational potential using the NFW profile, validating the $\Lambda$CDM mass-concentration relation. Implementing the Chameleon screening model, we...
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Chaymae Karam (Mohammed V University of Rabat, Faculty of Sciences (High Energy Physics Team - Modeling and Simulation))14/04/2025, 18:00
In the quest to understand the accelerated expansion of the universe, f(Q) gravity offers a promising alternative to General Relativity (GR) by incorporating non-metricity into the gravitational framework. Unlike GR, which relies on spacetime curvature, f(Q) gravity modifies the Einstein-Hilbert action by replacing the Ricci scalar R with a function f(Q), where Q represents the non-metricity...
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Jessica Turner15/04/2025, 09:30
Primordial black holes, which could have formed after inflation, can have significant implications for the history of the early Universe. Such a population of black holes, which may have differing mass and spin, can undergo evaporation due to Hawking radiation at different points in time. In this talk, I will review the potential impact of this evaporation on various cosmological observables,...
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Chris Byrnes15/04/2025, 10:15
Black holes with masses between a million and a billion solar masses are seen in the centres of many galaxies, even at high redshift. Their origin remains unknown and hard to explain, raising the possibility that these black holes are primordial rather than astrophysical. I will discuss the motivation for this scenario and the difficulty in finding a working model of the early universe (e.g....
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Marco Calza (University of Trento)15/04/2025, 10:30
It has been argued that realistic models of (singularity-free) black holes (BHs) embedded within an expanding Universe are coupled to the large-scale cosmological dynamics, with striking consequences, including pure cosmological growth of BH masses. In this pilot study, we examine the consequences of this growth for the stochastic gravitational wave background (SGWB) produced by inspiraling...
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Eleanna Kolonia (Perimeter Institute, University of Waterloo)15/04/2025, 10:45
It is well known that alternative theories to the Standard Model allow and sometimes require fundamental constants, such as the fine-structure constant, α, to vary in spacetime. We demonstrate that one way to investigate these variations is through the Mass-Radius relation of compact astrophysical objects, which is inherently affected by α variations. We start by considering the model of a...
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Dr JAVIER RUBIO (Universidad Complutense de Madrid)15/04/2025, 11:30
We explore a minimal scenario where the Standard-Model Higgs is responsible for reheating the Universe after inflation and produces a significant background of gravitational waves. The characteristic features of such signal can be directly correlated to the classical stability of the electroweak vacuum, thus offering a novel connection between the inflationary scale and the top quark mass at...
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Nicola Barbieri (INFN Ferrara)15/04/2025, 11:45
If reheating occurs at sufficiently low temperatures (below $20$ MeV), neutrinos--assuming they are populated only through weak interactions--do not have enough time to reach thermal equilibrium before decoupling. We present an updated analysis of cosmological models with very low reheating scenarios, including a more precise computation of neutrino distribution functions, leveraging the...
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Prof. Orfeu Bertolami (University of Porto)15/04/2025, 12:00
The de Sitter Swampland Conjectures are used to test some inflationary models compatible with CMBdata. We find that warm inflationary models, with one or more scalar fields, and the Claplygin-inspired models for some class of potentials satisfy the de Sitter Swampland Conjectures. Inflationary models in the context of theories of gravity that couple non-minimally curvature and matter are shown...
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Paulo B. Ferraz (University of Coimbra)15/04/2025, 12:15
We study classical background electric fields and the Schwinger effect in de Sitter space. We show that having a constant electric field in de Sitter requires the photon to have a tachyonic mass proportional to the Hubble scale. This has physical implications for the induced Schwinger current which affect its IR behaviour. To study this we recompute the Schwinger current in de Sitter space for...
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Diogo Gorgulho (University of Coimbra)15/04/2025, 12:30
We develop and analyse a novel mechanism based on Warm Little Inflaton models that allows for production of scalar particles $\chi$ during the slow-roll regime due to a narrow parametric resonance. We show that an appreciable energy density of $\chi$ particles can be generated through this mechanism without it becoming the dominant contribution to the Friedmann equation, thus preserving the...
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Maria Pestana Da Luz Pereira Ramos15/04/2025, 14:30
The QCD axion is a well-motivated candidate for new physics and a primary focus of an ambitious global experimental program. It offers a compelling solution to both the strong CP and the dark matter problems within a narrow region of its parameter space, known as the QCD axion band. Nevertheless, rich theoretical frameworks lead us to expect that the axion is not the only exotic scalar...
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Riccardo Impavido (Università di Ferrara, INFN Ferrara)15/04/2025, 14:45
Axion-like particles (ALPS), radiated from a network of cosmic strings, may be a large part of Dark Matter (DM). In the era of precision cosmology, it is possible to characterize the effect of such particles - which almost scale invariant distribution function spans many orders of magnitudes in momentum - on the observables. In this work, we employ the CLASS code and Planck 2018 data to place...
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Guilherme Guedes (DESY)15/04/2025, 15:00
Small instantons can enhance the axion mass, due to an appropriate modification of QCD in the ultraviolet (UV), in a way where the axion still solves the strong CP problem. However, besides increasing the axion mass, small instantons can also enhance any CP violation present in the theory, which can shift the minimum of the axion potential, putting the the axion solution strong CP problem at...
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Siyao Li15/04/2025, 15:15
Oscillons are long-lived localized solitons of a real scalar field with potential flatter than quadratic. They are considered to be formed through parametric resonance during preheating after inflation and can play an important role in the early universe because of their long lifetime. However, their lifetime can be greatly affected by the parametric resonance if there is coupling of the...
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Ioana Alexandra Zelko (Canadian Institute for Theoretical Astrophysics)15/04/2025, 15:30
The nature of dark matter is one of the most important unsolved questions in science. Some dark matter candidates do not have sufficient nongravitational interactions to be probed in laboratory or accelerator experiments. It is thus important to develop astrophysical probes which can constrain or lead to a discovery of such candidates. I illustrate this using state-of-the-art measurements of...
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Samuel Pinto (FCUP / CAUP)15/04/2025, 15:45
According to the von Laue condition, the volume integral of the proper pressure inside isolated particles with a fixed structure and finite mass vanishes in the Minkowski limit of general relativity. We explore this condition considering a simple illustrative example: non-standard static global monopoles with finite energy, for which the von Laue condition is satisfied when the proper pressure...
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Ms MARÍA PÉREZ GARROTE (USAL)15/04/2025, 16:45Talk
I will discuss how the effective geometry seen by photons propagating on a non-trivial electromagnetic background within Born-Infeld theory corresponds to an asymmetric wormhole. I will explain some interesting properties of the generated geometry such as the behaviour of null geodesics. Interestingly, the wormhole effective geometry arises for the background fields created by a charged...
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Duarte Feiteira (Department of Physics, University of Helsinki)15/04/2025, 17:00Talk
The Penrose process consists of transferring energy from a black hole to infinity. This process can be studied in a combined description with the Bañados-Silk-West (BSW) mechanism, which uses collisions of ingoing particles at the event horizon of a black hole to locally produce large amounts of energy. In this talk, the blending of the Penrose process with BSW mechanism is described for a $d$...
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Mr Oscar Jaime Michelin Galindo-Uriarte15/04/2025, 17:15Talk
We present two nonlinear electromagnetic black hole solutions belonging to the Kerr-Newman-AdS-NUT family, referred to as cubic potential and quartic potential. These solutions are characterized by mass, angular momentum, electric and magnetic charge, the NUT parameter, the cosmological constant, and a nonlinear parameter. We provide the necessary electromagnetic potentials to generate these...
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José Arturo Báez Jiménez (Center of Research and Advanced Studies (CINVESTAV))15/04/2025, 17:30Talk
This work explores the extraction of energy from electrostatic black holes through the decay or splitting of electrically charged particles. We establish the energetic criteria for viable extraction, deriving a general expression for the efficiency that depends on black hole and particle parameters. Focusing on Reissner-Nordström (RN) and Reissner-Nordström-de Sitter (RNdS) black holes, we...
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Sung-Won Kim (Ewha Womans University)15/04/2025, 17:45Talk
We considered the generation of gravitational waves by the binary system associated with a wormhole. In the Newtonian limit, the gravitational potential of a wormhole requires the effective mass of the wormhole taking into account radial tension effects. This definition allows us to derive gravitational wave production in homogeneous and heterogeneous binary systems. Therefore, we studied...
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José Luis Bernal16/04/2025, 09:30
Line-Intensity mapping (LIM) uses the integrated flux along the line of sight with relatively low-aperture telescopes, recovering radial information targeting known spectral lines discarding the continuum emission. Mapping the intensity fluctuations of an array of lines from HI 21cm to optical-UV lines offers a unique opportunity to probe redshifts well beyond the reach of other cosmological...
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Javier de Cruz Pérez (Universidad de Córdoba)16/04/2025, 10:15
The symmetry group of general relativity is the group of diffeomorphisms (Diff), which means that the form of the physical equations remains invariant under general coordinate transformations. We discuss the cosmological implications of breaking the Diff invariance down to transverse diffeomorphisms (TDiff) invariance in the matter sector. We show that even simple cases, like a minimally...
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Dr Ruchika Ruchika (University of Salamanca)16/04/2025, 10:30
Observations from the James Webb Space Telescope (JWST) have unveiled an unexpectedly high abundance of massive galaxies at early times, further challenging ΛCDM predictions. I will discuss our pioneering solutions for these tensions and their implications for the future of cosmology.
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Adrià Gómez-Valent16/04/2025, 10:45
The parameter $\sigma_8$, which represents the root-mean-square (rms) mass fluctuations on a scale of $R_8=8h^{-1}$ Mpc (where $h$ is the reduced Hubble parameter), is commonly used to quantify the amplitude of matter fluctuations at linear cosmological scales. Derived quantities, such as $S_8=\sigma_8(\Omega_m^{0}/0.3)^{0.5}$, are also frequently employed. However, the dependence of $R_8$ on...
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Arianna Favale (University of Rome Tor Vergata)16/04/2025, 11:30
Several studies in the literature have found a discrepancy between Baryon Acoustic Oscillation (BAO) measurements derived from two distinct methodologies, i.e. the two-dimensional (2D, angular) and the three-dimensional (3D, anisotropic) BAO. Since these probes play a key role in building the inverse distance ladder, this inconsistency affects discussions on the Hubble tension and its...
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Marcos Muniz Cueli16/04/2025, 11:45
Weak gravitational lensing has flourished into one of the most competitive fields in cosmology, based on two main pillars, namely cosmic shear and galaxy-galaxy lensing. However, there is a third pillar that is usually overlooked as an observable in itself: cosmic magnification, the statistical correlation in the sky between the position of foreground galaxies and the number counts of...
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Carlos Alonso Álvarez16/04/2025, 12:00
This work uses Lick indices to derive an independent, cosmology-free measurement of the Hubble parameter H(z), focusing on massive, passive galaxies at low redshift (z<0.4) from SDSS Legacy data. Unlike prior studies based on Full Spectral Fitting (FSF) or the D4000 spectral feature, we adopt a novel combined Lick index approach. Two Stellar Population Synthesis models are employed: Thomas,...
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JUAN ALBERTO CANO DIEZ16/04/2025, 12:15
Submillimeter galaxies (SMGs) are a population of high-redshift, dust-obscured galaxies with high star-formation rates and a steep number of counts, making them crucial for understanding galaxy formation and evolution. This study investigates the physical properties of 68 candidate gravitationally lensed SMGs at $z>1.2$ from the Herschel-ATLAS catalog, along with their associated lenses at...
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Carlos Martins16/04/2025, 12:30
Cosmography is a model-independent phenomenological approach to observational cosmology, relying on Taylor series expansions of physical quantities as a function of the cosmological redshift or analogous variables. A recent work [Martins et al. Phys. Lett. B827 (2022) 137002] developed the formalism for a cosmographic analysis of astrophysical and local measurements of the fine-structure...
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