A5064383464- Cosmology and Gravitation Theories
- Pulsars and Gravitational Waves Research
- Black Holes and Theoretical Physics
- Dark Matter and Cosmic Phenomena
- Particle physics theoretical and experimental studies
- Galaxies: Formation, Evolution, Phenomena
- Radio Astronomy Observations and Technology
- Geophysics and Gravity Measurements
- Cold Atom Physics and Bose-Einstein Condensates
- Atomic and Subatomic Physics Research
- Computational Physics and Python Applications
- Advanced Frequency and Time Standards
- Gamma-ray bursts and supernovae
- Relativity and Gravitational Theory
- Astrophysics and Cosmic Phenomena
- High-Energy Particle Collisions Research
- Methane Hydrates and Related Phenomena
- Complex Systems and Time Series Analysis
- Astronomy and Astrophysical Research
- Solar and Space Plasma Dynamics
- Quantum, superfluid, helium dynamics
- Superconducting and THz Device Technology
- Meteorological Phenomena and Simulations
- Astrophysical Phenomena and Observations
- Quantum Mechanics and Applications
National Institute of Chemical Physics and Biophysics
2017-2024
University of Padua
2023-2024
Istituto Nazionale di Fisica Nucleare, Sezione di Padova
2023-2024
Tallinn University of Technology
2024
Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)
2024
Leibniz University Hannover
2024
Institute for High Energy Physics
2021-2023
Universitat Autònoma de Barcelona
2022
European Organization for Nuclear Research
2021
King's College London
2019-2020
We revisit the cosmological and astrophysical constraints on fraction of dark matter in primordial black holes (PBHs) with an extended mass function. consider a variety functions, all which are described by three parameters: characteristic width fraction. Various observations then impose as function first two parameters. show how these relate to those for monochromatic function, demonstrating that they usually become more stringent case than one. Considering only well-established bounds,...
We outline the experimental concept and key scientific capabilities of AION (Atom Interferometer Observatory Network), a proposed programme using cold strontium atoms to search for ultra-light dark matter, explore gravitational waves in mid-frequency range between peak sensitivities LISA LIGO/Virgo/ KAGRA/INDIGO/Einstein Telescope/Cosmic Explorer experiments, probe other frontiers fundamental physics. would complement planned searches as well mergers involving intermediate-mass black holes...
We study the production of primordial black hole (PBH) binaries and resulting merger rate, accounting for an extended PBH mass function possibility a clustered spatial distribution. Under hypothesis that gravitational wave events observed by LIGO were caused mergers, we show it is possible to satisfy all present constraints on abundance, find viable parameter range lognormal function. The non-observation background allows us derive fraction dark matter in PBHs, which are stronger than any...
The abundance of primordial black holes (PBHs) in the mass range $0.1 - 10^3 M_\odot$ can potentially be tested by gravitational wave observations due to large merger rate PBH binaries formed early universe. To put estimates latter on a firmer footing, we first derive analytical for general functions while imposing minimal initial comoving distance between binary and nearest it, order pick only configurations where would not get disrupted. We then study formation evolution before...
We show that the recent NANOGrav result can be interpreted as a stochastic gravitational wave signal associated to formation of primordial black holes from high-amplitude curvature perturbations. The indicated amplitude and power spectrum agrees well with seeds for supermassive holes.
We analyse the LIGO-Virgo data, including recently released GWTC-2 dataset, to test a hypothesis that data contains more than one population of black holes. perform maximum likelihood analysis astrophysical holes with truncated power-law mass function whose merger rate follows from star formation rate, and primordial for which we consider log-normal critical collapse functions. find alone are strongly disfavoured by while best fit is obtained template combining rates. Alternatively, may hint...
We consider a real scalar singlet field which provides strong first-order electroweak phase transition via its coupling to the Higgs boson, and gives $CP$ violating contribution on top quark mass dimension-6 operator. study correlation between baryon-to-entropy ratio produced by baryogenesis, gravitational wave signal from transition. show that future experiments can test, in particular, region of model parameter space where observed be obtained even if new physics scale, is explicit operator, high.
We derive a lower bound on the merger rate of primordial black hole (PBH) binaries by estimating maximal fraction that were perturbed between formation in early Universe and merger, computing conservative binaries. This implies robust constraints PBH abundance range $1--100{M}_{\ensuremath{\bigodot}}$. further show LIGO/Virgo design sensitivity has potential to reach mass $1{0}^{\ensuremath{-}2}--1{0}^{3}{M}_{\ensuremath{\bigodot}}$. The constraint from is stronger if PBHs are initially...
We study whether the signal seen by pulsar timing arrays (PTAs) may originate from gravitational waves (GWs) induced large primordial perturbations. Such perturbations be accompanied a sizable black hole (PBH) abundance. improve existing analyses and show that PBH overproduction disfavors Gaussian scenarios for scalar-induced GWs at 2σ single-field inflationary scenarios, accounting non-Gaussianity, 3σ as explanation of most constraining NANOGrav 15-year data. This tension can relaxed in...
The most conservative interpretation of the nHz stochastic gravitational wave background (SGWB) discovered by NANOGrav and other pulsar timing array (PTA) collaborations is astrophysical, namely that it originates from supermassive black hole (SMBH) binaries. However, alternative cosmological models have been proposed, including cosmic strings, phase transitions, domain walls, primordial fluctuations, ``audible'' axions. We perform a multimodel analysis (MMA) to compare how well these...
We construct an analytically solvable simplified model that captures the essential features for primordial black hole (PBH) production in most models of single-field inflation. The construction makes use Wands duality between constant-roll (or slow-roll) and preceding ultra-slow-roll phases can be realized by a simple inflaton potential two joined parabolas. Within this framework, it is possible to formulate explicit inflationary scenarios consistent with CMB observations copious PBHs...
We analyze cosmic superstring models in light of NANOGrav 15-year pulsar timing data. A good fit is found for a string tension $G\ensuremath{\mu}\ensuremath{\sim}{10}^{\ensuremath{-}12}--{10}^{\ensuremath{-}11}$ and intercommutation probability $p\ensuremath{\sim}{10}^{\ensuremath{-}3}--{10}^{\ensuremath{-}1}$. Extrapolation to higher frequencies assuming standard big bang cosmology compatible at the 68% CL with current LIGO/Virgo/KAGRA upper limit on stochastic gravitational wave background...
We estimate the gravitational wave spectra generated in strongly supercooled phase transitions by bubble collisions and fluid motion. derive analytically thin-wall approximation efficiency factor that determines share of energy released transition between scalar field fluid. perform numerical simulations including as a function radius separately for all points on surfaces to take into account their different collision times. find does not significantly change show result can be approximated...
A bstract We study the formation of primordial black holes (PBHs) in strongly super-cooled first-order phase transitions. The mechanism is based on presence remnants dominated by false vacuum that scale slower with expansion Universe than their surroundings where this energy was already converted into radiation. compute PBH from these including contribution and bubble walls, estimating collapse using hoop conjecture considering both regions collapsing immediately when entering horizon...
The NANOGrav and other pulsar timing arrays (PTAs) have recently announced evidence for nHz gravitational waves (GWs) that may originate from supermassive black hole (SMBH) binaries. spectral index of the GW signal differs predicted binary evolution by emission alone, we show environmental effects such as dynamical friction with gas, stars, dark matter improve consistency SMBH model PTA data. We comment on possible implications observations fluctuations in frequency spectrum measurements GWs...
The James Webb Space Telescope has detected surprisingly luminous early galaxies that indicate a tension with the $\mathrm{\ensuremath{\Lambda}}$ cold dark matter. Motivated by scenarios including axion miniclusters or primordial black holes, we consider power-law modifications of matter power spectrum. We show could be resolved if consists $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}\text{ }\text{ }\mathrm{eV}$ axions fraction ${f}_{\mathrm{PBH}}>0.005$ is composed compact...
The recently claimed anomaly in the measurement of 21 cm hydrogen absorption signal by EDGES at $z\sim 17$, if cosmological, requires existence new physics. possible attempts to resolve rely on either (i) cooling gas via dark matter-hydrogen interactions or (ii) modifying soft photon background beyond standard CMB one, as possibly suggested also ARCADE~2 excess. We argue that solutions belonging first class are generally tension with cosmological matter probes once simple sector models...
We study possible effects of a dark matter (DM) core on the maximum mass neutron star (NS), mass-radius relation and NS tidal deformability parameter $\mathrm{\ensuremath{\Lambda}}$. show that all these quantities would in general be reduced presence DM core. In particular, our calculations indicate with fraction $\ensuremath{\sim}5%$ could affect significantly interpretation data as constraints nuclear equation state (EOS), potentially excluding some EOS models basis measured PSR...
We update predictions for the gravitational wave (GW) signal from a strongly supercooled phase transition in an illustrative classically conformal U(1)B−L model. implement ∝ γ2 scaling of friction on bubble wall and estimates efficiency factors GW production collisions plasma-related sources. take into account fact that small decay rate symmetry-breaking field may lead to brief matter-dominated era after transition, as oscillates around its minimum before decaying. find strong collision...
We derive efficiency factors for the production of gravitational waves through bubble collisions and plasma-related sources in strong phase transitions, find conditions under which can contribute significantly to signal. use lattice simulations clarify dependence colliding bubbles on their initial state. illustrate our findings two examples, Standard Model with an extra |H|6 interaction a classically scale-invariant U(1)B−L extension Model. The contribution GW spectrum from is found be...
We study production of primordial black holes (PBHs) during an early matter-dominated phase. As a source perturbations, we consider either inflaton field with running spectral index or spectator that has blue spectrum and thus provides significant contribution to PBH at small scales. First, identify the region parameter space where fraction observed dark matter can be produced, taking into account all current constraints. Then, present constraints on amplitude as function reheating...
The EDGES experiment has recently measured an anomalous global 21-cm spectrum due to hydrogen absorptions at redshifts of about $z\sim 17$. Model independently, the unusually low temperature baryons probed by this observable sets strong constraints on any physical process that transfers energy into baryonic environment such redshifts. Here we make use derive bounds injection a possible population ${\cal O}(1-100) M_\odot$ primordial black holes, which induce wide radiation during accretion...
Motivated by the recent detection of gravitational wave signal emitted a binary neutron star merger, we analyse possible impact dark matter on such signals. We show that cores in merging stars may yield an observable supplementary peak power spectral density following which could be distinguished from features produced components.
Making use of a dimensionally-reduced effective theory at high temperature, we perform nonperturbative study the electroweak phase transition in Two Higgs Doublet model. We focus on two phenomenologically allowed points parameter space, carrying out dynamical lattice simulations to determine equilibrium properties transition. discuss shortcomings conventional perturbative approaches based resummed potential - regarding insufficient handling infrared resummation but also need account for...