A5058696807- Cosmology and Gravitation Theories
- Black Holes and Theoretical Physics
- Solar and Space Plasma Dynamics
- Galaxies: Formation, Evolution, Phenomena
- Relativity and Gravitational Theory
- Noncommutative and Quantum Gravity Theories
- Geophysics and Gravity Measurements
- Advanced Differential Geometry Research
- Pulsars and Gravitational Waves Research
- Dark Matter and Cosmic Phenomena
- Computational Physics and Python Applications
- Geometric Analysis and Curvature Flows
- Particle physics theoretical and experimental studies
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Geomagnetism and Paleomagnetism Studies
- Quantum Electrodynamics and Casimir Effect
- Advanced Thermodynamics and Statistical Mechanics
- Astrophysical Phenomena and Observations
- Scientific Research and Discoveries
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Advanced Mathematical Theories and Applications
- Quantum Mechanics and Applications
Universidad de Salamanca
2012-2023
Leipzig University
2019
Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)
2019
European Organization for Nuclear Research
2008-2009
Instituto de Física Fundamental
2008
University of Freiburg
2002-2004
University of Geneva
2000-2002
University of the Basque Country
2001
University of Sussex
1997-1999
ETH Zurich
1999
Primordial magnetic fields that exist before the photon-baryon decoupling epoch are damped on length scales below photon diffusion and free-streaming scales. The energy injected into plasma by dissipation of magnetosonic Alfv'en waves heats photons, creating a y-type distortion black-body spectrum cosmic microwave background. This is converted μ-type when elastic Compton scattering efficient. Therefore, we can use observational limits y- distortions to constrain properties in early universe....
Large-scale magnetic fields affect the scalar modes of geometry whose ultimate effect is to determine anisotropies Cosmic Microwave Background (CMB in what follows). For first time, a consistent numerical approach magnetized CMB pursued with aim assessing angular power spectra temperature and polarization when stochastic background inhomogeneous are simultaneously present plasma. The effects related nature plasma taken into account both at level dynamical equations initial conditions...
The high- and low-frequency descriptions of the pre-decoupling plasma are deduced from Vlasov-Landau treatment generalized to curved space-times in presence relativistic fluctuations geometry. It is demonstrated that interplay between one-fluid two-fluid treatments mandatory for a complete reliable calculation polarization observables. Einstein-Boltzmann hierarchy handle dispersive propagation electromagnetic disturbances plasma. Given improved physical numerical framework, observables...
Following the pioneering observations with COBE in early 1990s, studies of cosmic microwave background (CMB) have focused on temperature and polarization anisotropies. CMB spectral distortions - tiny departures energy spectrum from that a perfect blackbody provide second, independent probe fundamental physics, reach deep into primordial Universe. The theoretical foundation has seen major advances recent years, which highlight immense potential this emerging field. Spectral property Universe...
Damping of magnetic fields via ambipolar diffusion and decay magnetohydrodynamical (MHD) turbulence in the post decoupling era heats intergalactic medium (IGM). Delayed recombination hydrogen atoms IGM yields an optical depth to scattering cosmic microwave background (CMB). The generated at z ≫ 10 does not affect ``reionization bump'' CMB polarization power spectrum low multipoles, but affects temperature spectra high multipoles. Writing present-day energy density smoothed over damping scale...
The creation of large scale magnetic fields is studied in an inflationary universe where electrodynamics assumed to be nonlinear. After inflation ends becomes linear and thus the description reheating subsequent radiation dominated stage are unaltered. nonlinear regime described by Lagrangians having a power-law dependence on one invariants electromagnetic field. It found that there range parameters for which primordial cosmologically interesting strengths can created.
The generation of primordial magnetic seed fields during inflation is studied in a theory derived from the one-loop vacuum polarization effective action photon curved background. This includes terms which couple curvature to Maxwell tensor. resulting field strength estimated model where inflationary phase directly matched standard radiation dominated era. allowed parameter region analyzed and compared with bounds necessary galactic field. It found that cosmologically interesting strengths...
Primordial magnetic fields present since before the epoch of matter-radiation equality have an effect on anisotropies cosmic microwave background. The CMB due to scalar perturbations are calculated in gauge invariant formalism for magnetized adiabatic initial conditions. Furthermore linear matter power spectrum is calculated. Numerical solutions complemented by a qualitative analysis.
We present exact inhomogeneous and anisotropic cosmological solutions of low-energy string theory containing dilaton axion fields. The spacetime metric possesses cylindrical symmetry. describe ever-expanding universes with an initial curvature singularity contain known homogeneous as subcases. asymptotic form the solution near has a spatially varying Kasner-like form. fields are found to evolve quasihomogeneously on scales larger than particle horizon. When inhomogeneities enter horizon they...
A complete numerical calculation of the temperature anisotropies and polarization cosmic microwave background in presence a stochastic helical magnetic field is presented which includes contributions due to scalar, vector tensor modes. The correlation functions are calculated numerically including Gaussian window function effectively cut off spectrum damping. Apart from parity-even correlations nature induces parity-odd between $E$ $B$ mode as well ($T$) mode.
A variety of beyond the standard model scenarios contain very light hidden sector U(1) gauge bosons undergoing kinetic mixing with photon. The resulting oscillation between ordinary and photons leads to spectral distortions cosmic microwave background. We update bounds on parameter $\chi_0$ mass photon $m_{\gamma'}$ for future experiments measuring CMB distortions, such as PIXIE PRISM/COrE. For $10^{-14}\;{\rm eV}\lesssim m_{\gamma'}\lesssim 10^{-13}\;{\rm eV}$, we find angle has be less...
We determine the most general form of antisymmetric $H$-field tensor derived from a purely time-dependent potential that is admitted by all possible spatially homogeneous cosmological models in 3+1-dimensional low-energy bosonic string theory. The maximum number components $H$ field are left arbitrary found for each cosmology defined Bianchi group classification. relative generality these cosmologies counting independent pieces Cauchy data needed to specify solution Einstein's equations....
Magnetic fields are observed on nearly all scales in the Universe, from stars and galaxies up to galaxy clusters even beyond. The origin of cosmic magnetic is still an open question, however a large class models puts its very early Universe. A dynamo amplifying initial seed field could explain present day strength galactic field. However, it problem how when this was created.
The most general initial conditions of cosmic microwave background anisotropies, compatible with the presence pre-equality magnetic fields, are derived. When plasma is composed photons, baryons, electrons, cold dark matter particles and neutrinos, data truncated Einstein-Boltzmann hierarchy contemplate one magnetized adiabatic mode four (magnetized) nonadiabatic modes. After obtaining analytical form various solutions, numerically integrated for corresponding sets data. TT, TE EE angular...
The standard $\ensuremath{\Lambda}\mathrm{CDM}$ paradigm is complemented with a magnetized contribution whose effects on the anisotropies of cosmic microwave background are assessed by means dedicated numerical approach. accuracy temperature and polarization correlations stems from inclusion large-scale magnetic fields both at level initial conditions Einstein-Boltzmann hierarchy which consistently embedded in generalized magnetohydrodynamical framework. Examples calculations angular power...
We show that vector theories on cosmological scales are excellent candidates for dark energy. consider two different examples, both with no dimensional parameters nor potential terms, natural initial conditions in the early universe and same number of free as ΛCDM. The first one exhibits scaling behaviour during radiation a strong phantom phase today, ending "big‐freeze" singularity. This model provides best fit to date SNIa Gold dataset. second theory we is standard electromagnetism....
The perturbative approach to stochastic inflation is used determine the spectrum of density fluctuations and gravitational waves due coarse grained field. amplitude curvature fluctuation spectrum, spectral index running are in general found be smaller than standard inflation. Furthermore, amount non-Gaussianity second-order perturbation estimated.
Dark energy and dark matter are the dominant sources in evolution of late universe. They currently only indirectly detected via their gravitational effects, there could be a coupling between them without violating observational constraints. We investigate background dynamics when is modeled as exponential quintessence, coupled to simple models exchange. introduce new form sector coupling, which leads more complicated dynamical phase space has better physical motivation than previous...
The existence of extremely dark and compact astronomical bodies is by now a well established observational fact. On the other hand, classical General Relativity predicts black holes which fit very with observations, but do lead to important conceptual problems. In this contribution we ask ourselves straightforward question: Are objects that have evidence for in sense Relativity? By revising semiclassical scenario stellar collapse find out as result some alternative could be formed might...
Dynamical extra dimensions break the conformal invariance of Maxwell's equations in four dimensions. A higher dimensional background with $n$ contracting and expanding is matched to an effectively standard radiation dominated universe. The resulting spectrum for magnetic field calculated taking into account also momenta along Imposing constraints from observations upper limit on strength seed fields found. Depending number dimensions, cosmologically interesting can be created.
We construct a broad family of exact solutions to the five-dimensional Einstein equations coupled scalar field with an exponential potential. Embedding three-brane in these bulk space-times particular way we obtain class self-tuned curved brane worlds which vacuum energy on is gravitationally idle, four-dimensional geometry being insensitive value tension. This self-tuning arises from cancellations, enforced by junction conditions, between potential, and matter brane. Finally, study some...
We present a generic inference method for inflation models from observational data by the usage of higher-order statistics curvature perturbation on uniform density hypersurfaces. This is based calculation posterior primordial non-Gaussianity parameters fNL and gNL, which in general depend specific reheating models, enables to discriminate among still viable models. To keep analyticity as far possible dispense with numerically expensive sampling techniques saddle-point approximation...
The Lorentz term raises the linear matter power on small scale which leads to interesting signatures in 21 cm signal. Numerical simulations of resuting nonlinear density field, distribution ionized hydrogen and signal at different values redshift are presented for magnetic fields with field strength B=5 nG, spectral indices $n_B=-2.9, -2.2$ -1.5 together adiabatic mode best fit data Planck13+WP. Comparing averaged global projected SKA1-LOW sensitivities Square Kilometre Array (SKA) it might...
The Penrose limits of inhomogeneous cosmologies admitting two Abelian Killing vectors and their T duals are found in general. wave profiles the resulting plane waves given for particular solutions. non-Abelian dualities used as solution generating techniques. Furthermore, it is that, unlike case duality, duality taking limit not commutative procedures.