A5070607224- Cosmology and Gravitation Theories
- Dark Matter and Cosmic Phenomena
- Black Holes and Theoretical Physics
- Galaxies: Formation, Evolution, Phenomena
- Particle physics theoretical and experimental studies
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- Relativity and Gravitational Theory
- Earth Systems and Cosmic Evolution
- Computational Physics and Python Applications
- Neutrino Physics Research
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Advanced Thermodynamics and Statistical Mechanics
- Scientific Research and Discoveries
- Gamma-ray bursts and supernovae
- Quantum Electrodynamics and Casimir Effect
University of Coimbra
2024
Institute for High Energy Physics
2021-2023
Centre de Recerca Matemàtica
2023
KTH Royal Institute of Technology
2019-2021
Stockholm University
2019-2021
University of Southern Denmark
2013-2018
Universitat de Barcelona
2017-2018
Centre for Cosmology and Particle Physics Phenomenology
2013-2017
Universidade do Porto
2012
Scattering and decay processes of thermal bath particles involving heavy leptons can dump hot axions in the primordial plasma around QCD phase transition. We compute their relic density, parameterized by an effective number ΔNeff additional neutrinos. For couplings allowed current bounds, production via scattering yields ≲ 0.6 0.2 for cases muon tau, respectively. Flavor violating tau decays to a lighter lepton plus axion give 0.3. Such values alleviate tension between direct local...
Abstract We present a model-independent search for gravitational wave background from cosmic domain walls (DWs) in the NANOGrav 12.5 years dataset and International PTA Data Release 2. DWs that annihilate at temperatures ∼ 20–50 MeV with tensions (40–100 TeV) 3 provide as good fit to both datasets astrophysical supermassive black hole mergers. may decay into Standard Model (SM) or dark sector. In latter case we predict an abundance Δ N eff of radiation well within reach upcoming CMB surveys....
The simplest gauge invariant models of inflationary magnetogenesis are known to suffer from the problems either large backreaction or strong coupling, which make it difficult self-consistently achieve cosmic magnetic fields inflation with a field strength larger than 10−32G today on Mpc scale. Such is insufficient act as seed for galactic dynamo effect, requires 10−20G. In this paper we analyze simple extensions minimal model, avoid both coupling and back reaction problems, in order generate...
We study the dynamics of a homogeneous and isotropic Friedmann-Robertson-Walker universe in context Eddington-inspired Born-Infeld theory gravity. generalize earlier results, obtained radiation dominated universe, to account for evolution permeated by perfect fluid with an arbitrary equation state parameter $w$. show that bounce may occur $\ensuremath{\kappa}>0$, if $w$ is time dependent, we demonstrate it free from tensor singularities. argue cosmologies be viable alternative inflationary...
Axions play a central role in many realizations of large field models inflation and recent alternative mechanisms for generating primordial tensor modes small models. If these axions couple to gauge fields, the coupling produces tachyonic instability that leads an exponential enhancement which turn can decay into observable scalar or curvature perturbations. Thus, fully self-consistent treatment during is important, this work we discuss perturbative constraints on coupled fields. We show how...
Abstract The evidence for a non-vanishing isotropic cosmic birefringence in recent analyses of the CMB data provides tantalizing hint new physics. Domain wall (DW) networks have recently been shown to generate an signal ballpark measured value when coupled photons. In this work, we explore axionic defects hypothesis more detail and extending previous results annihilating late-forming networks, by pointing out other smoking-gun signatures network spectrum such as anisotropic birefringent...
Abstract Unstable domain wall (DW) networks in the early universe are cosmologically viable and can emit a large amount of gravitational waves (GW) before annihilating. As such, they provide an interpretation for recent signal reported by Pulsar Timing Array (PTA) collaborations. A related important question is whether such scenario also leads to significant production Primordial Black Holes (PBH). We investigate both GW PBH using 3D numerical simulations expanding background, with box sizes...
We consider the presence of an axion like particle, σ, with a generic CP violating axial coupling form (ασ/f) $$ F\tilde{F} , where F μν is gauge field strength abelian U(1) group, not necessarily associated standard electromagnetism, and f decay constant axion. It has previously been demonstrated that if identified inflaton, such interaction can lead to measurable cosmological signatures (non-Gaussian modifications curvature perturbation spectrum) depending on parameter \xi = \alpha...
We obtain traversable wormhole and time machine solutions of the field equations an alternative gravity with non-minimally curvature-matter coupling. Our exhibit a non-trivial redshift function allow for matter that satisfy dominant energy condition.
We show that when the QCD axion is directly coupled to quarks with ${c}_{i}/f{\ensuremath{\partial}}_{\ensuremath{\mu}}a{\overline{q}}_{i}{\ensuremath{\gamma}}^{\ensuremath{\mu}}{\ensuremath{\gamma}}^{5}{q}_{i}$, such as in Dine-Fischler-Srednicki-Zhitnitsky models, dominant production mechanism early Universe at temperatures $1\text{ }\text{ }\mathrm{GeV}\ensuremath{\lesssim}T\ensuremath{\lesssim}100\text{ }\mathrm{GeV}$ obtained via ${q}_{i}{\overline{q}}_{i}\ensuremath{\leftrightarrow}ga$...
Abstract Light axions can potentially leave a cosmic background, just like neutrinos. We complete the study of thermal axion production across electroweak scale by providing smooth and continuous treatment through two phases. Focusing on both flavor conserving violating couplings to third generation quarks, we compute amount produced via scatterings decays bath particles. perform model independent analysis in terms effective couplings, also make predictions for specific microscopic QCD...
We perform for the first time a dedicated analysis of cosmological constraints on Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) QCD axion models. Such constructions are especially interesting in light recent xenon1texcess and hints from stellar cooling. In DFSZ models, ${m}_{a}\ensuremath{\gtrsim}0.1\text{ }\text{ }\mathrm{eV}$, scatterings pions muons can produce sizable cosmic background thermal axions, that behave similarly to massive neutrinos. However, pion coupling depends alignment...
Abstract We show that in theories of axionlike particles (ALPs) coupled to electrons at tree-level, the one-loop effective coupling photons is process dependent: relevant for decay processes, g aγ (D) , differs significantly from appearing phenomenologically important Primakoff process, (P) . this has implications physics massive ALPs hot and dense environments, such as supernovae. derive, a consequence, new limits on ALP-electron coupling, ĝ ae SN 1987A by accounting all production...
Abstract We analyze the dynamics and observational signatures of axion clouds formed via superradiant instability around primordial black holes, focusing on mass range 10 14 - 18 kg where latter may account for all dark matter. take into leading effects self-interactions, showing that, even though these limit number axions produced within each cloud, a large become free hole's gravitational potential accumulate in intergalactic medium or host galaxy, depending their escape velocity. This...
Dark matter energy injection in the early universe modifies both ionization history and temperature of intergalactic medium. In this work, we improve CMB bounds on sub-keV dark extend previous from Lyman-$\alpha$ observations to same mass range, resulting new competitive constraints axion-like particles (ALPs) decaying into two photons. The limits depend underlying reionization history, here accounted self-consistently by our modified version publicly available {\tt DarkHistory} CLASS}...
Recent observational claims of magnetic fields stronger than $10^{-16}$ G in the extragalactic medium motivate a new look for their origin inflationary magnetogenesis models. In this work we shall review constraints on simplest gauge invariant model $f^2(\phi)F_{\mu \nu}F^{\mu \nu}$ magnetogenesis, and show that optimal region parameter space anisotropic coming from induced bispectrum, due to generated electromagnetic fields, yield strongest constraints. model, only very fine tuned scenario...
Astroparticle physics is undergoing a profound transformation, due to series of extraordinary new results, such as the discovery high-energy cosmic neutrinos with IceCube, direct detection gravitational waves LIGO and Virgo, many others. This white paper result collaborative effort that involved hundreds theoretical astroparticle physicists cosmologists, under coordination European Consortium for Theory (EuCAPT). Addressed whole community, it explores upcoming opportunities challenges our...
The axion solution to the strong CP problem is delicately sensitive Peccei-Quinn breaking contributions that are misaligned with respect QCD instantons. Heavy models appealing because they avoid this so-called quality problem. We show generic realizations of framework can be probed by LIGO-Virgo-KAGRA interferometers, through stochastic gravitational wave (GW) signal sourced long-lived axionic string-domain wall network and upcoming measurements neutron proton electric dipole moments....
We analyze the dynamics of inflationary models with a coupling inflaton ϕ to gauge fields form F /f, as in case axions. It is known that this leads an instability, exponential amplification fields, controlled by parameter ξ= /(2fH), which can strongly affect generation cosmological perturbations and even background. show scattering rates involving become larger than expansion rate H, due very large occupation numbers, create thermal bath particles temperature T during inflation. In regime,...
The recent electron recoil excess observed by XENON1T has a possible interpretation in terms of solar axions coupled to electrons. If such are still relativistic at recombination they would also leave cosmic imprint the form an additional radiation component, parameterized effective neutrino number Δ Neff. We explore minimal scenarios with detectable signal future CMB surveys: democratically all fermions, axion-electron coupling generated radiatively, DFSZ framework for QCD axion. predicted...
We consider a quintessence field which transitions from matter-like to cosmological constant behavior between recombination and the present time. aim at easing tension in measurement of Hubble rate, we assess $\Lambda$CDM model properly enlarged include our against observations. The does not address scope proposed. This result allows us exclude class quintessential models as solution measurements.
Inflation can be supported in very steep potentials if it is generated by rapidly turning fields, which natural negatively curved field spaces. The curvature perturbation, ζ, of these models undergoes an exponential, transient amplification around the time horizon crossing, but still compatible with observations at level power spectrum. However, a recent analysis (based on proposed single-field effective theory imaginary speed sound) found that trispectrum and other higher-order,...
In this work, we study the luminosity that results from conversion of QCD axion particles into photons in magnetic field plasma accreting onto black holes (BHs). For luminosities to be large two conditions need met: (i) there are numbers axions primordial BH surroundings as a result so-called superradiant instability; (ii) exists point inside region where and masses similar is resonant axion-photon conversion. BHs interstellar medium our Galaxy, above require hole have subsolar therefore led...
Several laboratory experiments have published limits on axionlike particles (ALPs) with feeble couplings to electrons and masses in the keV-MeV range, under assumption that such ALPs comprise dark matter. We note decay radiatively into photons, show for a large subset of parameter space ostensibly probed by these experiments, lifetime is shorter than age universe. Such cannot consistently make up matter, which significantly affects interpretation from GERDA, Edelweiss-III, SuperCDMS...
Soft gravitons produced by the expansion of de Sitter can be viewed as Nambu-Goldstone bosons spontaneously broken asymptotic symmetries spacetime. We explicitly construct associated charges, and show that acting with charges on vacuum creates a new state equivalent to change in local coordinates induced soft graviton. While effect remains unobservable within domain single observer where symmetry is unbroken, this physical when comparing different observers, or between transformed...