Posts Tagged presence

Recent Postings from presence

How chameleons core dwarfs with cusps

The presence of a scalar field that couples nonminimally and universally to matter can enhance gravitational forces on cosmological scales while restoring general relativity in the Solar neighborhood. In the intermediate regime, kinematically inferred masses experience an additional radial dependence with respect to the underlying distribution of matter, which is caused by the increment of gravitational forces with increasing distance from the Milky Way center. The same effect can influence the internal kinematics of subhalos and cause cuspy matter distributions to appear core-like. Specializing to the chameleon model as a worked example, we demonstrate this effect by tracing the scalar field from the outskirts of the Milky Way halo to its interior, simultaneously fitting observed velocity dispersions of chemo-dynamically discriminated red giant populations in the Fornax and Sculptor dwarf spheroidals. Whereas in standard gravity these observations suggest that the matter distribution of the dwarfs is cored, we find that in the presence of a chameleon field the assumption of a cuspy Navarro-Frenk-White profile becomes perfectly compatible with the data. Importantly, chameleon models also predict the existence of slopes between two stellar subcomponents that in Newtonian gravity would be interpreted as a depletion of matter in the dwarf center. Hence, an observation of such an apparently pathological scenario may serve as a smoking gun for the presence of a chameleon field or a similar modification of gravity, independent of baryonic feedback effects. In general, measuring the dynamic mass profiles of the Milky Way dwarfs provides stronger constraints than those inferred from the screening scale of the Solar System since these are located at greater distances from the halo center.

Double-diffusive mixing in stellar interiors in the presence of horizontal gradients

We have identified an important source of mixing in stellar radiation zones, that would arise whenever two conditions are satisfied: (1) the presence of an inverse vertical compositional gradient, and (2) the presence of density-compensating horizontal gradients of temperature (alternatively, entropy) and composition. The former can be caused naturally by any off-center burning process, by atomic diffusion, or by surface accretion. The latter could be caused by rotation, tides, meridional flows, etc. The linear instability and its nonlinear development have been well-studied in the oceanographic context. It is known to drive the formation of stacks of fingering layers separated by diffusive interfaces, called intrusions. Using 3D numerical simulations of the process in the astrophysically-relevant region of parameter space, we find similar results, and demonstrate that the material transport in the intrusive regime can be highly enhanced compared with pure diffusion, even in systems which would otherwise be stable to fingering (thermohaline) convection.

A connection between accretion state and $\textit{Fe K absorption}$ in an accreting neutron star: black hole-like soft state winds?

High resolution X-ray spectra of accreting stellar mass Black Holes reveal the presence of accretion disc winds, traced by high ionisation Fe K lines. These winds appear to have an equatorial geometry and to be observed only during disc dominated states in which the radio jet is absent. Accreting neutron star systems also show equatorial high ionisation absorbers. However, the presence of any correlation with the accretion state has not been previously tested. We have studied EXO 0748-676, a transient neutron star system, for which we can reliably determine the accretion state, in order to investigate the Fe K absorption/accretion state/jet connection. Not one of twenty X-ray spectra obtained in the hard state revealed any significant Fe K absorption line. However, intense Fe ${\scriptsize{\rm XXV}}$ and Fe ${\scriptsize{\rm XXVI}}$ (as well as a rarely observed Fe ${\scriptsize{\rm XXIII}}$ line plus S ${\scriptsize{\rm XVI}}$; a blend of S ${\scriptsize{\rm XVI}}$ and Ar ${\scriptsize{\rm XVII}}$; Ca ${\scriptsize{\rm XX}}$ and Ca ${\scriptsize{\rm XIX}}$, possibly produced by the same high ionisation material) absorption lines ($EW_{\rm Fe~{XXIII-XXV}}=31\pm3$ eV, $EW_{\rm Fe~XXVI}=8\pm3$ eV) are clearly detected during the only soft state observation. This suggests that the connection between Fe K absorption and states (and anticorrelation between the presence of Fe K absorption and jets) is also valid for EXO 0748-676 and therefore it is not a unique property of black hole systems but a more general characteristic of accreting sources.

Adaptive Optics Images III: 87 Kepler Objects of Interest

The Kepler mission has revolutionized our understanding of exoplanets, but some of the planet candidates identified by Kepler may actually be astrophysical false positives or planets whose transit depths are diluted by the presence of another star. Adaptive optics images made with ARIES at the MMT of 87 Kepler Objects of Interest place limits on the presence of fainter stars in or near the Kepler aperture. We detected visual companions within 1" for five stars, between 1" and 2" for seven stars, and between 2" and 4" for 15 stars. For those systems, we estimate the brightness of companion stars in the Kepler bandpass and provide approximate corrections to the radii of associated planet candidates due to the extra light in the aperture. For all stars observed, we report detection limits on the presence of nearby stars. ARIES is typically sensitive to stars approximately 5.3 Ks magnitudes fainter than the target star within 1" and approximately 5.7 Ks magnitudes fainter within 2", but can detect stars as faint as delta Ks = 7.5 under ideal conditions.

Observational effects of the early episodically dominating dark energy

We investigate observational consequences of the early episodically dominating dark energy on the evolution of cosmological density perturbations. For this aim, we introduce the minimally coupled scalar field dark energy model with the Albrecht-Skordis potential which allows a sudden ephemeral domination of dark energy component during the radiation or early matter era. The conventional cosmological parameters in the presence of such an early dark energy are constrained with WMAP and Planck cosmic microwave background radiation data including other external data sets. It is shown that in the presence of such an early dark energy the estimated cosmological parameters can deviate substantially from the currently known \Lambda CDM-based parameters, with best-fit values differing by several percents for WMAP and by a percent level for Planck data. For the latter case, only a limited amount of dark energy with episodic nature is allowed since the Planck data strongly favors the \Lambda CDM model. Compared with the conventional dark energy model, the early dark energy dominating near radiation-matter equality or at the early matter era results in the shorter cosmic age or the presence of tensor-type perturbation, respectively. Our analysis demonstrates that the alternative cosmological parameter estimation is allowed based on the same observations even in Einstein’s gravity.

Absorption of scalars by extremal black holes in string theory

We show that the low frequency absorption cross section of minimally coupled massless scalar fields by extremal spherically symmetric black holes in d dimensions in the presence of string-theoretical alpha’ corrections is equal to the horizon area. Classically one has the relation sigma=4GS between the absorption cross section and the black hole entropy. We discuss the validity of such relation in the presence of alpha’ corrections for extremal black holes, both nonsupersymmetric and supersymmetric. The examples we consider seem to indicate that this relation is verified in the presence of alpha’ corrections for supersymmetric black holes, but not for nonsupersymmetric ones.

Abundance analysis, spectral variability, and search for the presence of a magnetic field in the typical PGa star HD19400

The aim of this study is to carry out an abundance determination, to search for spectral variability and for the presence of a weak magnetic field in the typical PGa star HD19400. High-resolution, high signal-to-noise HARPS spectropolarimetric observations of HD19400 were obtained at three different epochs in 2011 and 2013. For the first time, we present abundances of various elements determined using an ATLAS12 model, including the abundances of a number of elements not analysed by previous studies, such as Ne I, Ga II, and Xe II. Several lines of As II are also present in the spectra of HD19400. To study the variability, we compared the behaviour of the line profiles of various elements. We report on the first detection of anomalous shapes of line profiles belonging to Mn and Hg, and the variability of the line profiles belonging to the elements Hg, P, Mn, Fe, and Ga. We suggest that the variability of the line profiles of these elements is caused by their non-uniform surface distribution, similar to the presence of chemical spots detected in HgMn stars. The search for the presence of a magnetic field was carried out using the moment technique and the SVD method. Our measurements of the magnetic field with the moment technique using 22 Mn II lines indicate the potential existence of a weak variable longitudinal magnetic field on the first epoch. The SVD method applied to the Mn II lines indicates <B_z>=-76+-25G on the first epoch, and at the same epoch the SVD analysis of the observations using the Fe II lines shows <B_z>=-91+-35G. The calculated false alarm probability values, 0.008 and 0.003, respectively, are above the value 10^{-3}, indicating no detection.

Planet formation in Binaries [Replacement]

Spurred by the discovery of numerous exoplanets in multiple systems, binaries have become in recent years one of the main topics in planet formation research. Numerous studies have investigated to what extent the presence of a stellar companion can affect the planet formation process. Such studies have implications that can reach beyond the sole context of binaries, as they allow to test certain aspects of the planet formation scenario by submitting them to extreme environments. We review here the current understanding on this complex problem. We show in particular how each of the different stages of the planet-formation process is affected differently by binary perturbations. We focus especially on the intermediate stage of kilometre-sized planetesimal accretion, which has proven to be the most sensitive to binarity and for which the presence of some exoplanets observed in tight binaries is difficult to explain by in-situ formation following the "standard" planet-formation scenario. Some tentative solutions to this apparent paradox are presented. The last part of our review presents a thorough description of the problem of planet habitability, for which the binary environment creates a complex situation because of the presence of two irradation sources of varying distance.

Planet formation in Binaries

Spurred by the discovery of numerous exoplanets in multiple systems, binaries have become in recent years one of the main topics in planet formation research. Numerous studies have investigated to what extent the presence of a stellar companion can affect the planet formation process. Such studies have implications that can reach beyond the sole context of binaries, as they allow to test certain aspects of the planet formation scenario by submitting them to extreme environments. We review here the current understanding on this complex problem. We show in particular how each of the different stages of the planet-formation process is affected differently by binary perturbations. We focus especially on the intermediate stage of kilometre-sized planetesimal accretion, which has proven to be the most sensitive to binarity and for which the presence of some exoplanets observed in tight binaries is difficult to explain by in-situ formation following the "standard" planet-formation scenario. Some tentative solutions to this apparent paradox are presented. The last part of our review presents a thorough description of the problem of planet habitability, for which the binary environment creates a complex situation because of the presence of two irradation sources of varying distance.

Planet formation in Binaries [Replacement]

Spurred by the discovery of numerous exoplanets in multiple systems, binaries have become in recent years one of the main topics in planet formation research. Numerous studies have investigated to what extent the presence of a stellar companion can affect the planet formation process. Such studies have implications that can reach beyond the sole context of binaries, as they allow to test certain aspects of the planet formation scenario by submitting them to extreme environments. We review here the current understanding on this complex problem. We show in particular how each of the different stages of the planet-formation process is affected differently by binary perturbations. We focus especially on the intermediate stage of kilometre-sized planetesimal accretion, which has proven to be the most sensitive to binarity and for which the presence of some exoplanets observed in tight binaries is difficult to explain by in-situ formation following the "standard" planet-formation scenario. Some tentative solutions to this apparent paradox are presented. The last part of our review presents a thorough description of the problem of planet habitability, for which the binary environment creates a complex situation because of the presence of two irradation sources of varying distance.

Black holes in the presence of dark energy [Cross-Listing]

The new, rapidly developing field of theoretical research — studies of dark energy interacting with black holes (and, in particular, accreting onto black holes) — is reviewed. The term `dark energy’ is meant to cover a wide range of field theory models, as well as perfect fluids with various equations of state, including cosmological dark energy. Various accretion models are analyzed in terms of the simplest test field approximation or by allowing back reaction on the black-hole metric. The behavior of various types of dark energy in the vicinity of Schwarzschild and electrically charged black holes is examined. Nontrivial effects due to the presence of dark energy in the black hole vicinity are discussed. In particular, a physical explanation is given of why the black hole mass decreases when phantom energy is being accreted, a process in which the basic energy conditions of the famous theorem of nondecreasing horizon area in classical black holes are violated. The theoretical possibility of a signal escaping from beneath the black hole event horizon is discussed for a number of dark energy models. Finally, the violation of the laws of thermodynamics by black holes in the presence of noncanonical fields is considered.

Running non-Gaussianity in the presence of inflationary vector fields

We consider cosmological inflationary models in which vector fields play some role in the generation of the primordial curvature perturbation $\zeta$. Such models are interesting because the involved vector fields naturally seed statistical anisotropy in the primordial fluctuations which eventually could leave a measurable imprint on the CMB fluctuations. In this article, we estimate the size of scale dependent effects on the non-Gaussianity (NG) parameters due to the scale dependent statistical anisotropy in the distribution of the fluctuations. For concreteness, we use a power spectrum (PS) of the fluctuations of the cuadrupolar form: $P_\zeta(\vec{k})\equiv P_\zeta(k)\left[1+g_\zeta(k)(\hat{n} \cdot \hat{k})^2 \right]$, where $g_{\zeta}(k)$ is the only quantity which parametrizes the level of statistical anisotropy and $\hat{n}$ is a unitary vector which points towards the preferred direction. Then, we evaluate the contribution of the running of $g_{\zeta}(k)$ on the NG parameters by means of the $\delta N$ formalism. We focus specifically in the details for the $f_{\rm NL}$ NG parameter, associated to the bispectrum $B_\zeta$, but the structure of higher order NG parameters is straightforward to generalize. Although the level of statistical anisotropy in the PS is severely constrained by recent observations, the importance of statistical anisotropy signals in higher order correlators remains to be determined, this being the main task that we address here. The precise measurement of the running of statistical parameters such as the statistical anisotropy level and the NG parameters could provide relevant elements for model building and for the determination of the presence (or non presence) of inflationary vector fields and their role in the inflationary mechanism.

Running non-Gaussianity in the presence of inflationary vector fields [Cross-Listing]

We consider cosmological inflationary models in which vector fields play some role in the generation of the primordial curvature perturbation $\zeta$. Such models are interesting because the involved vector fields naturally seed statistical anisotropy in the primordial fluctuations which eventually could leave a measurable imprint on the CMB fluctuations. In this article, we estimate the size of scale dependent effects on the non-Gaussianity (NG) parameters due to the scale dependent statistical anisotropy in the distribution of the fluctuations. For concreteness, we use a power spectrum (PS) of the fluctuations of the cuadrupolar form: $P_\zeta(\vec{k})\equiv P_\zeta(k)\left[1+g_\zeta(k)(\hat{n} \cdot \hat{k})^2 \right]$, where $g_{\zeta}(k)$ is the only quantity which parametrizes the level of statistical anisotropy and $\hat{n}$ is a unitary vector which points towards the preferred direction. Then, we evaluate the contribution of the running of $g_{\zeta}(k)$ on the NG parameters by means of the $\delta N$ formalism. We focus specifically in the details for the $f_{\rm NL}$ NG parameter, associated to the bispectrum $B_\zeta$, but the structure of higher order NG parameters is straightforward to generalize. Although the level of statistical anisotropy in the PS is severely constrained by recent observations, the importance of statistical anisotropy signals in higher order correlators remains to be determined, this being the main task that we address here. The precise measurement of the running of statistical parameters such as the statistical anisotropy level and the NG parameters could provide relevant elements for model building and for the determination of the presence (or non presence) of inflationary vector fields and their role in the inflationary mechanism.

Stability properties of Hawking radiation in the presence of ultraviolet violation of local Lorentz invariance [Cross-Listing]

In this thesis, we study several features of Hawking radiation in the presence of ultraviolet Lorentz violations. These violations are implemented by a modified dispersion relation that becomes nonlinear at short wavelengths. The motivations of this work arise on the one hand from the developing field of analog gravity, where we aim at measuring the Hawking effect in fluid flows that mimic black hole space-times, and on the other hand from the possibility that quantum gravity effects might be approximately modeled by a modified dispersion relation. We develop several studies on various aspects of the problem. First we obtain precise characterizations about the deviations from the Hawking result of black hole radiation, which are induced by dispersion. Second, we study the emergence, both in white hole flows or for massive fields, of a macroscopic standing wave, spontaneously produced from the Hawking effect, and known as `undulation’. Third, we describe in detail an instability named black hole laser, which arises in the presence of two horizons, where Hawking radiation is self-amplified and induces an exponentially growing in time emitted flux.

Stability properties of Hawking radiation in the presence of ultraviolet violation of local Lorentz invariance

In this thesis, we study several features of Hawking radiation in the presence of ultraviolet Lorentz violations. These violations are implemented by a modified dispersion relation that becomes nonlinear at short wavelengths. The motivations of this work arise on the one hand from the developing field of analog gravity, where we aim at measuring the Hawking effect in fluid flows that mimic black hole space-times, and on the other hand from the possibility that quantum gravity effects might be approximately modeled by a modified dispersion relation. We develop several studies on various aspects of the problem. First we obtain precise characterizations about the deviations from the Hawking result of black hole radiation, which are induced by dispersion. Second, we study the emergence, both in white hole flows or for massive fields, of a macroscopic standing wave, spontaneously produced from the Hawking effect, and known as `undulation’. Third, we describe in detail an instability named black hole laser, which arises in the presence of two horizons, where Hawking radiation is self-amplified and induces an exponentially growing in time emitted flux.

Optical and near-infrared spectroscopy of the black hole GX 339-4 II. The spectrocopic content in the low/hard and high/soft states

As a complement to our optical and near-infrared study of the continuum properties of GX 339-4 in the two hard and one soft state observations made by the ESO/VLT FORS2 and ISAAC in early 2010, we report here on the results of our spectral line analysis for the same observations. In the soft state, the presence of strong Balmer, Paschen and Brackett emission lines points to the optical and near-infrared spectra stemming from the irradiated chromosphere of the optically thick and geometrically thin accretion disc. Most of these HI features are still detected in emission in both hard states but are veiled by the compact jets continuum. We also confirm the presence of a broad Hbeta absorption feature, prominent in the soft state and shallower in the first hard state, which we argue forms in the deep layers of the optically thick accretion disc. However, this trough is absent in the second hard state, a likely consequence of the formation of a geometrically thick extended envelope that arises above the disc plane and eventually enshrouds the region where the Hbeta absorption feature forms. We detect this envelope through the presence of a broad Pabeta emission line, which is constant during the first hard state but correlates with the underlying continuum during the second hard state, pointing to changing physical properties. We consider that this behaviour may be consistent with the launch of a thermally-driven accretion disc wind during the second hard state.

Galaxy clusters in presence of dark energy: a kinetic approach

Context. The external regions of galaxy clusters may be under strong influence of the dark energy, discovered by observations of the SN Ia at redshift z < 1. Aims. The presence of the dark energy in the gravitational equilibrium equation, with the Einstein $\Lambda$ term, contrasts the gravity, making the equilibrium configuration more extended in radius. Methods. In this paper we derive and solve the kinetic equation for an equilibrium configuration in presence of the dark energy, by considering the Newtonian regime, being the observed velocities of the galaxies inside a cluster largely smaller than the light velocity. Results. The presence of the dark energy in the gravitational equilibrium equation leads to wide regions in the $W_0-\rho_{\Lambda}$ diagram where the equilibrium solutions are not permitted, due to the prevalence of the effects of the dark energy on the gravity.

Galaxy clusters in presence of dark energy: a kinetic approach [Cross-Listing]

Context. The external regions of galaxy clusters may be under strong influence of the dark energy, discovered by observations of the SN Ia at redshift z < 1. Aims. The presence of the dark energy in the gravitational equilibrium equation, with the Einstein $\Lambda$ term, contrasts the gravity, making the equilibrium configuration more extended in radius. Methods. In this paper we derive and solve the kinetic equation for an equilibrium configuration in presence of the dark energy, by considering the Newtonian regime, being the observed velocities of the galaxies inside a cluster largely smaller than the light velocity. Results. The presence of the dark energy in the gravitational equilibrium equation leads to wide regions in the $W_0-\rho_{\Lambda}$ diagram where the equilibrium solutions are not permitted, due to the prevalence of the effects of the dark energy on the gravity.

Dynamics of ten clusters of galaxies with substructures

We present a detailed Chandra study of a sample of ten clusters of galaxies selected based on the presence of substructures in their optical images. The X-ray surface brightness maps of most of these clusters show anisotropic morphologies, especially in the central regions. A total of 22 well resolved significantly bright X-ray peaks (corresponding with high-density regions) are seen in the central parts (within r$_{\rm c}/2$) of the clusters. Multiple peaks are seen in central parts of six clusters. Eleven peaks are found to have optical counterparts (10 coinciding with the BCGs of the 10 clusters and one coinciding with the second brightest galaxy in A539). For most of the clusters, the optical substructures detected in the previous studies are found to be outside the field of view of Chandra. In the spectroscopically produced 2-D temperature maps, significantly lower temperatures are seen at the location of three peaks (two in A539 and one in A376). The centres of five clusters in our sample also host regions of higher temperature compared to the ambient medium, indicating the presence of galaxy scale mergers. The X-ray luminosity, gas mass and central cooling time estimates for all the clusters are presented. The radial X-ray surface-brightness profiles of all but one of the clusters are found to be best-fitted with a double-$\beta$ model, pointing towards the presence of double-phased central gas due to cool-cores. The cooling time estimates of all the clusters, however, indicate that none of them hosts a strong cool-core, although the possibility of weak cool-cores cannot be ruled out.

Stable static structures in models with galileon-like dynamics

We investigate the presence of static solutions in generalized models described by a real scalar field in four-dimensional space-time. We study models in which the scalar field engenders galileon-like dynamics and spontaneous symmetry breaking, inducing the presence of domain walls. The galileon-like behavior keeps to equation of motion second-order differential equation, so we focus on the presence of first-order equation that solves the equation of motion and very much help us to investigate stability on general grounds. We then illustrate the investigation with some specific examples, showing that the domain wall may become compact and that the zero mode may split. Moreover, if the model is further generalized to include k-field behavior, it may contribute to split the static structure.

Stable static structures in models with galileon-like dynamics [Replacement]

We investigate the presence of static solutions in generalized models described by a real scalar field in four-dimensional space-time. We study models in which the scalar field engenders galileon-like dynamics and spontaneous symmetry breaking, inducing the presence of domain walls. The galileon-like behavior keeps to equation of motion second-order differential equation, so we focus on the presence of first-order equation that solves the equation of motion and very much help us to investigate stability on general grounds. We then illustrate the investigation with some specific examples, showing that the domain wall may become compact and that the zero mode may split. Moreover, if the model is further generalized to include k-field behavior, it may contribute to split the static structure.

Remarks on the spin-one Duffin-Kemmer-Petiau equation in the presence of nonminimal vector interactions in (3+1) dimensions

In a recent paper published in this journal, Hassanabadi and collaborators [Advances in High Energy Physics, vol. 2012, Article ID 489641, 10 pages, 2012] analyzed the Duffin-Kemmer-Petiau equation in the presence of nonminimal vectorial interactions (Coulomb and harmonic oscillator potentials) in (3+1) dimensions for spin-one particles. In that paper, the authors used improperly the nonminimal vector interaction endangering in their main conclusions. We present a few properties of the nonminimal vector interactions and also present the correct equations to this problem. We show that the solution can be easily found by solving a Schr\"{o}dinger-like equation. As an application of this procedure, we consider spin-one particles in presence of a nonminimal vector linear potential. Additionally, we present the correct set of first-order coupled differential radial equation for the DKP equation in the presence of minimal vector and scalar interactions.

Short time scale spectral variability in the A0 supergiant HD92207 and the importance of line profile variations for the interpretation of FORS2 spectropolarimetric observations

Our recent search for the presence of a magnetic field in the bright early A-type supergiant HD92207 using FORS2 in spectropolarimetric mode indicated the presence of a longitudinal magnetic field of the order of a few hundred Gauss. Assuming the ideal case of a non-variable star, this discovery has recently been questioned in one work trying to demonstrate the importance of non-photon noise in FORS2 observations. The assumption of non-variability of HD92207 can, however, not be held since substantial profile variations of diverse lines on a time scale of minutes or maybe even a fraction of a minute are detected in FORS2 spectra. The presence of short-term spectral variability in blue supergiants, which are considered as type II supernova progenitors, has not been a subject of systematic studies before and is critical for the current theoretical understanding of their physics. Given the detected short term variability, the question of the presence of a magnetic field cannot be answered without proper modeling of the impact of such a variability on the measurements of the magnetic field. Since the short-term periodicity does not fit into the currently known domain of non-radially pulsating supergiants, its confirmation is of great importance for models of stellar evolution.

Radiation from a moving planar dipole layer: patch potentials vs dynamical Casimir effect [Cross-Listing]

We study the classical electromagnetic radiation due to the presence of a dipole layer on a plane that performs a bounded motion along its normal direction, to the first non-trivial order in the amplitude of that motion. We show that the total emitted power may be written in terms of the dipole layer autocorrelation function. We then apply the general expression for the emitted power to cases where the dipole layer models the presence of patch potentials, comparing the magnitude of the emitted radiation with that coming from the quantum vacuum in the presence of a moving perfect conductor (dynamical Casimir effect).

Constraining neutron star matter with QCD

In recent years, there have been several successful attempts to constrain the equation of state of neutron star matter using input from low-energy nuclear physics and observational data. We demonstrate that significant further restrictions can be placed by additionally requiring the pressure to approach that of deconfined quark matter at high densities. Remarkably, the new constraints turn out to be highly insensitive to the amount — or even presence — of quark matter inside the stars.

Constraining neutron star matter with QCD [Cross-Listing]

In recent years, there have been several successful attempts to constrain the equation of state of neutron star matter using input from low-energy nuclear physics and observational data. We demonstrate that significant further restrictions can be placed by additionally requiring the pressure to approach that of deconfined quark matter at high densities. Remarkably, the new constraints turn out to be highly insensitive to the amount — or even presence — of quark matter inside the stars.

Dynamics of tilted Bianchi models of types III, IV, V in presence of diffusion

We investigate the three types of class B Bianchi cosmologies filled with a tilted perfect fluid undergoing velocity diffusion in a scalar field background. We consider the two most importantcases: dust and radiation. A complete numerical integration of the Einstein field equations coupled with the diffusion equations is done to demonstrate how the presence of diffusion can affect the dynamics of cosmological evolution, where the most attention is paid to changes to the late-time behaviour. We show that aside from quantitative effects, diffusion can result in significant qualitative differences. For example, the cosmologies may recollapse if diffusion is sufficiently strong, or evolve towards the de Sitter state otherwise. In constrast to the diffusionless case, radiation isotropizes in presence of diffusion, and the tilt decreases exponentially at later times: $V\sim e^{-0.25\tau}$; also, we determine the decay rates of energy density, which become slower when the diffusion term is non-zero.

Women in Italian astronomy

This document gives some quantitative facts about the role of women in Italian astronomy. More than 26% of Italian IAU members are women: this is the largest fraction among the world leading countries in astronomy. Most of this high fraction is due to their presence in INAF, where women make up 32% of the research staff (289 out of 908) and 40% of the technical/administrative staff (173 out of 433); the percentage is slightly lower among permanent research staff (180 out of 599, about 30%). The presence of women is lower in the Universities (27 out of 161, about 17%, among staff). In spite of these (mildly) positive facts, we notice that similarly to other countries (e.g. USA and Germany) career prospects for Italian astronomers are clearly worse for women than for men. Within INAF, the fraction of women is about 35-40% among non-permanent position, 36% for Investigators, 17% for Associato/Primo Ricercatore, and only 13% among Ordinario/Dirigente di Ricerca. The situation is even worse at University (only 6% of Professore Ordinario are women). We found that similar trends are also present if researchers are ordered according to citation rather than position: for instance, women make up only 15% among the 100 most cited astronomers working in Italy, a percentage which is however twice that over all Europe. A similar fraction is found among first authors of most influential papers, which cannot be explained as a residual of a lower female presence in the past. We conclude that implicit sex discrimination factors probably dominate over explicit ones and are still strongly at work. Finally, we discuss the possible connection between the typical career pattern and these factors.

How dusty is alpha Centauri? Excess or non-excess over the infrared photospheres of main-sequence stars

[Abridged] Debris discs around main-sequence stars indicate the presence of larger rocky bodies. The components of the nearby binary aCentauri have higher than solar metallicities, which is thought to promote giant planet formation. We aim to determine the level of emission from debris in the aCen system. Having already detected the temperature minimum, Tmin, of aCenA, we here attempt to do so also for the companion aCenB. Using the aCen stars as templates, we study possible effects Tmin may have on the detectability of unresolved dust discs around other stars. We use Herschel and APEX photometry to determine the stellar spectral energy distributions. In addition, we use APEX for spectral line mapping to study the complex background around aCen seen in the photometric images. Models of stellar atmospheres and discs are used to estimate the amount of debris around these stars. For solar-type stars, a fractional dust luminosity fd 2e-7 could account for SEDs that do not exhibit the Tmin-effect. Slight excesses at the 2.5 sigma level are observed at 24 mu for both stars, which, if interpreted to be due to dust, would correspond to fd (1-3)e-5. Dynamical disc modelling leads to rough mass estimates of the putative Zodi belts around the aCen stars, viz. <~4e-6 MMoon of 4 to 1000 mu size grains, distributed according to n a^-3.5. Similarly, for filled-in Tmin emission, corresponding EKBs could account for ~1e-3 MMoon of dust. Light scattered and/or thermally emitted by exo-Zodi discs will have profound implications for future spectroscopic missions designed to search for biomarkers in the atmospheres of Earth-like planets. The F-IR SED of aCenB is marginally consistent with the presence of a minimum temperature region in the upper atmosphere. We also show that an aCenA-like temperature minimum may result in an erroneous apprehension about the presence of dust around other stars.

How dusty is alpha Centauri? Excess or non-excess over the infrared photospheres of main-sequence stars [Replacement]

[Abridged] Debris discs around main-sequence stars indicate the presence of larger rocky bodies. The components of the nearby binary aCentauri have higher than solar metallicities, which is thought to promote giant planet formation. We aim to determine the level of emission from debris in the aCen system. Having already detected the temperature minimum, Tmin, of aCenA, we here attempt to do so also for the companion aCenB. Using the aCen stars as templates, we study possible effects Tmin may have on the detectability of unresolved dust discs around other stars. We use Herschel and APEX photometry to determine the stellar spectral energy distributions. In addition, we use APEX for spectral line mapping to study the complex background around aCen seen in the photometric images. Models of stellar atmospheres and discs are used to estimate the amount of debris around these stars. For solar-type stars, a fractional dust luminosity fd 2e-7 could account for SEDs that do not exhibit the Tmin-effect. Slight excesses at the 2.5 sigma level are observed at 24 mu for both stars, which, if interpreted to be due to dust, would correspond to fd (1-3)e-5. Dynamical disc modelling leads to rough mass estimates of the putative Zodi belts around the aCen stars, viz. <~4e-6 MMoon of 4 to 1000 mu size grains, distributed according to n a^-3.5. Similarly, for filled-in Tmin emission, corresponding EKBs could account for ~1e-3 MMoon of dust. Light scattered and/or thermally emitted by exo-Zodi discs will have profound implications for future spectroscopic missions designed to search for biomarkers in the atmospheres of Earth-like planets. The F-IR SED of aCenB is marginally consistent with the presence of a minimum temperature region in the upper atmosphere. We also show that an aCenA-like temperature minimum may result in an erroneous apprehension about the presence of dust around other stars.

Rotationally resolved spectroscopy of (20000) Varuna in the near-infrared

Models of the escape and retention of volatiles by minor icy objects exclude any presence of volatile ices on the surface of TNOs smaller than ~1000km in diameter at the typical temperature in this region of the solar system, whereas the same models show that water ice is stable on the surface of objects over a wide range of diameters. Collisions and cometary activity have been used to explain the process of surface refreshing of TNOs and Centaurs. These processes can produce surface heterogeneity that can be studied by collecting information at different rotational phases. The aims of this work are to study the surface composition of (20000)Varuna, a TNO with a diameter ~650km and to search for indications of rotational variability. We observed Varuna during two consecutive nights in January 2011 with NICS@TNG obtaining a set of spectra covering the whole rotation period of Varuna. After studying the spectra corresponding to different rotational phases, we did not find any indication of surface variability. In all the spectra, we detect an absorption at 2{\mu}m, suggesting the presence of water ice on the surface. We do not detect any other volatiles on the surface, although the S/N is not high enough to discard their presence. Based on scattering models, we present two possible compositions compatible with our set of data and discuss their implications in the frame of the collisional history of the Kuiper Belt. We find that the most probable composition for the surface of Varuna is a mixture of amorphous silicates, complex organics, and water ice. This composition is compatible with all the materials being primordial. However, our data can also be fitted by models containing up to a 10% of methane ice. For an object with the characteristics of Varuna, this volatile could not be primordial, so an event, such as an energetic impact, would be needed to explain its presence on the surface.

BBN And The CMB Constrain Light, Electromagnetically Coupled WIMPs

(Abridged) In the presence of a light WIMP (< 30 MeV), there are degeneracies among the nature of the WIMP, its couplings to standard model particles, its mass m_chi, and the number of equivalent neutrinos beyond the standard model, Delta N_nu. These degeneracies cannot be broken by the CMB constraint on the effective number of neutrinos, N_eff. However, big bang nucleosynthesis (BBN) is affected by a light WIMP and equivalent neutrinos, so the combination of BBN and CMB can break some of the degeneracies. Here, BBN predictions for abundances in the presence of a light WIMP and equivalent neutrinos are explored, and estimates of their observationally determined relic abundances are used to limit m_chi, Delta N_nu, and the present Universe baryon density (Omega_B h^2). These constraints are explored for Majorana and Dirac fermion WIMPs as well as for real and complex scalar WIMPs that couple to electrons, positrons, and photons. In a separate paper this analysis is repeated for WIMPs that couple only to the standard model neutrinos, and constraints for the two cases are contrasted. Without a light WIMP but allowing for equivalent neutrinos, the combined BBN and CMB constraints favor N_eff = 3.45 +/- 0.17, Omega_B h^2 = 0.0224 +/- 0.0003, and Delta N_nu = 0.40 +/- 0.17. In this case, standard BBN (Delta N_nu = 0) is disfavored at ~98% confidence, and the presence of one sterile neutrino (Delta N_nu = 1) is disfavored at > 99% confidence. Allowing a light WIMP and Delta N_nu equivalent neutrinos together, the combined BBN and CMB data provide lower limits to the WIMP masses (> 0.5 – 5 MeV) that depend on the nature of the WIMP, favor m_chi ~8 MeV slightly over no WIMP, and loosen constraints on equivalent neutrinos, Delta N_nu = 0.65+0.46-0.35. While Delta N_nu = 0 is still disfavored at ~95% confidence with a light WIMP, Delta N_nu = 1 is now allowed.

BBN And The CMB Constrain Light, Electromagnetically Coupled WIMPs [Replacement]

(Abridged) In the presence of a light WIMP (< 30 MeV), there are degeneracies among the nature of the WIMP, its couplings to standard model particles, its mass m_chi, and the number of equivalent neutrinos beyond the standard model, Delta N_nu. These degeneracies cannot be broken by the CMB constraint on the effective number of neutrinos, N_eff. However, big bang nucleosynthesis (BBN) is affected by a light WIMP and equivalent neutrinos, so the combination of BBN and CMB can break some of the degeneracies. Here, BBN predictions for abundances in the presence of a light WIMP and equivalent neutrinos are explored, and estimates of their observationally determined relic abundances are used to limit m_chi, Delta N_nu, and the present Universe baryon density (Omega_B h^2). These constraints are explored for Majorana and Dirac fermion WIMPs, as well as for real and complex scalar WIMPs that couple to electrons, positrons, and photons. In a separate paper this analysis is repeated for WIMPs that couple only to the standard model neutrinos, and constraints for the two cases are contrasted. Without a light WIMP but allowing for equivalent neutrinos, the combined BBN and CMB constraints favor N_eff = 3.46 +/- 0.17, Omega_B h^2 = 0.0224 +/- 0.0003, and Delta N_nu = 0.40 +/- 0.17. In this case, standard BBN (Delta N_nu = 0) is disfavored at ~98% confidence, and the presence of one sterile neutrino (Delta N_nu = 1) is disfavored at > 99% confidence. Allowing a light WIMP and Delta N_nu equivalent neutrinos together, the combined BBN and CMB data provide lower limits to the WIMP masses (> 0.5 – 5 MeV) that depend on the nature of the WIMP, favor m_chi ~8 MeV slightly over no WIMP, and loosen constraints on equivalent neutrinos, Delta N_nu = 0.65+0.46-0.35. While Delta N_nu = 0 is still disfavored at ~95% confidence with a light WIMP, Delta N_nu = 1 is now allowed.

BBN And The CMB Constrain Light, Electromagnetically Coupled WIMPs [Replacement]

(Abridged) In the presence of a light WIMP (< 30 MeV), there are degeneracies among the nature of the WIMP, its couplings to standard model particles, its mass m_chi, and the number of equivalent neutrinos beyond the standard model, Delta N_nu. These degeneracies cannot be broken by the CMB constraint on the effective number of neutrinos, N_eff. However, big bang nucleosynthesis (BBN) is affected by a light WIMP and equivalent neutrinos, so the combination of BBN and CMB can break some of the degeneracies. Here, BBN predictions for abundances in the presence of a light WIMP and equivalent neutrinos are explored, and estimates of their observationally determined relic abundances are used to limit m_chi, Delta N_nu, and the present Universe baryon density (Omega_B h^2). These constraints are explored for Majorana and Dirac fermion WIMPs as well as for real and complex scalar WIMPs that couple to electrons, positrons, and photons. In a separate paper this analysis is repeated for WIMPs that couple only to the standard model neutrinos, and constraints for the two cases are contrasted. Without a light WIMP but allowing for equivalent neutrinos, the combined BBN and CMB constraints favor N_eff = 3.46 +/- 0.17, Omega_B h^2 = 0.0224 +/- 0.0003, and Delta N_nu = 0.40 +/- 0.17. In this case, standard BBN (Delta N_nu = 0) is disfavored at ~98% confidence, and the presence of one sterile neutrino (Delta N_nu = 1) is disfavored at > 99% confidence. Allowing a light WIMP and Delta N_nu equivalent neutrinos together, the combined BBN and CMB data provide lower limits to the WIMP masses (> 0.5 – 5 MeV) that depend on the nature of the WIMP, favor m_chi ~8 MeV slightly over no WIMP, and loosen constraints on equivalent neutrinos, Delta N_nu = 0.65+0.46-0.35. While Delta N_nu = 0 is still disfavored at ~95% confidence with a light WIMP, Delta N_nu = 1 is now allowed.

BBN And The CMB Constrain Light, Electromagnetically Coupled WIMPs [Replacement]

(Abridged) In the presence of a light WIMP (< 30 MeV), there are degeneracies among the nature of the WIMP, its couplings to standard model particles, its mass m_chi, and the number of equivalent neutrinos beyond the standard model, Delta N_nu. These degeneracies cannot be broken by the CMB constraint on the effective number of neutrinos, N_eff. However, big bang nucleosynthesis (BBN) is affected by a light WIMP and equivalent neutrinos, so the combination of BBN and CMB can break some of the degeneracies. Here, BBN predictions for abundances in the presence of a light WIMP and equivalent neutrinos are explored, and estimates of their observationally determined relic abundances are used to limit m_chi, Delta N_nu, and the present Universe baryon density (Omega_B h^2). These constraints are explored for Majorana and Dirac fermion WIMPs, as well as for real and complex scalar WIMPs that couple to electrons, positrons, and photons. In a separate paper this analysis is repeated for WIMPs that couple only to the standard model neutrinos, and constraints for the two cases are contrasted. Without a light WIMP but allowing for equivalent neutrinos, the combined BBN and CMB constraints favor N_eff = 3.46 +/- 0.17, Omega_B h^2 = 0.0224 +/- 0.0003, and Delta N_nu = 0.40 +/- 0.17. In this case, standard BBN (Delta N_nu = 0) is disfavored at ~98% confidence, and the presence of one sterile neutrino (Delta N_nu = 1) is disfavored at > 99% confidence. Allowing a light WIMP and Delta N_nu equivalent neutrinos together, the combined BBN and CMB data provide lower limits to the WIMP masses (> 0.5 – 5 MeV) that depend on the nature of the WIMP, favor m_chi ~8 MeV slightly over no WIMP, and loosen constraints on equivalent neutrinos, Delta N_nu = 0.65+0.46-0.35. While Delta N_nu = 0 is still disfavored at ~95% confidence with a light WIMP, Delta N_nu = 1 is now allowed.

Asymptotically locally AdS and flat black holes in Horndeski theory [Replacement]

In this paper we construct asymptotically locally AdS and flat black holes in the presence of a scalar field whose kinetic term is constructed out from a linear combination of the metric and the Einstein tensor. The field equations as well as the energy-momentum tensor are second order in the metric and the field, therefore the theory belongs to the ones defined by Horndeski. We show that in the presence of a cosmological term in the action, it is possible to have a real scalar field in the region outside the event horizon. The solutions are characterized by a single integration constant, the scalar field vanishes at the horizon and it contributes to the effective cosmological constant at infinity. We extend these results to the topological case. The solution is disconnected from the maximally symmetric AdS background, however, within this family there exits a gravitational soliton which is everywhere regular. This soliton is therefore used as a background to define a finite Euclidean action and to obtain the thermodynamics of the black holes. For a certain region in the space of parameters, the thermodynamic analysis reveals a critical temperature at which a Hawking-Page phase transition between the black hole and the soliton occurs. We extend the solution to arbitrary dimensions grater than four and show that the presence of a cosmological term in the action allows to consider the case in which the standard kinetic term for the scalar it’s not present. In such scenario, the solution reduces to an asymptotically flat black hole.

Asymptotically locally AdS and flat black holes in Horndeski theory [Replacement]

In this paper we construct asymptotically locally AdS and flat black holes in the presence of a scalar field whose kinetic term is constructed out from a linear combination of the metric and the Einstein tensor. The field equations as well as the energy-momentum tensor are second order in the metric and the field, therefore the theory belongs to the ones defined by Horndeski. We show that in the presence of a cosmological term in the action, it is possible to have a real scalar field in the region outside the event horizon. The solutions are characterized by a single integration constant, the scalar field vanishes at the horizon and it contributes to the effective cosmological constant at infinity. We extend these results to the topological case. The solution is disconnected from the maximally symmetric AdS background, however, within this family there exits a gravitational soliton which is everywhere regular. This soliton is therefore used as a background to define a finite Euclidean action and to obtain the thermodynamics of the black holes. For a certain region in the space of parameters, the thermodynamic analysis reveals a critical temperature at which a Hawking-Page phase transition between the black hole and the soliton occurs. We extend the solution to arbitrary dimensions grater than four and show that the presence of a cosmological term in the action allows to consider the case in which the standard kinetic term for the scalar it’s not present. In such scenario, the solution reduces to an asymptotically flat black hole.

Asymptotically locally AdS and flat black holes in Horndeski theory

In this paper we construct asymptotically locally AdS and flat black holes in the presence of scalar field whose kinetic term is constructed out from a linear combination of the metric and the Einstein tensor. The field equations as well as the energy-momentum tensor are second order in the metric and the field, therefore the theory belongs to the ones defined by Horndeski. We show that in the presence of a cosmological term in the action, it is possible to have a real scalar field in the region outside of the event horizon. The solutions are characterized by a single integration constant, the scalar field vanishes at the horizon and it contributes to the effective cosmological constant at infinity. We extend these results to the topological case. The solution is disconnected from the maximally symmetric AdS background, however, within this family there exits a gravitational soliton which is everywhere regular. This soliton is therefore used as a background to define a finite Euclidean action and to obtain the thermodynamics of the black holes. We extend the solution to arbitrary dimensions grater than four and show that the presence of a cosmological term in the action allows to consider the case in which the standard kinetic term for the scalar its not present. In such scenario, the solution reduces to an asymptotically locally flat black hole

Rest-frame ultra-violet spectra of massive galaxies at z=3: evidence for high-velocity outflows

Galaxy formation models invoke the presence of strong feedback mechanisms that regulate the growth of massive galaxies at high redshifts. In this paper we aim to: (1) confirm spectroscopically the redshifts of a sample of massive galaxies selected with photometric redshifts larger than 2.5; (2) investigate the properties of their stellar and interstellar media; (3) detect the presence of outflows, and measure their velocities. To achieve this, we analysed deep, high-resolution (R=2000) FORS2 rest-frame UV spectra for 11 targets. We confirmed that 9 out of 11 have spectroscopic redshifts larger than 2.5. We also serendipitously found two mask fillers at redshift larger than 2.5, which originally were assigned photometric redshifts between 2.0 and 2.5. In the four highest-quality spectra we derived outflow velocities by fitting the absorption line profiles with models including multiple dynamical components. We found strongly asymmetric, high-ionisation lines, from which we derived outflow velocities ranging between 480 and 1528 km/s. We revised the spectral energy distribution fitting U-band through 8 micron photometry, including the analysis of a power-law component subtraction to identify the possible presence of active galactic nuclei (AGN). The revised stellar masses of all but one of our targets are larger than 1e10 solar masses, with four having stellar masses 5e10 solar masses. Three galaxies have a significant power-law component in their spectral energy distributions, which indicates that they host AGN. We conclude that massive galaxies are characterised by significantly higher velocity outflows than the typical Lyman break galaxies at redshifts around 3. The incidence of high-velocity outflows (approximately 40 per cent within our sample) is also much higher than among massive galaxies at redshifts below 1. (Abridged)

Rest-frame ultra-violet spectra of massive galaxies at z=3: evidence for high-velocity outflows [Replacement]

Galaxy formation models invoke the presence of strong feedback mechanisms that regulate the growth of massive galaxies at high redshifts. In this paper we aim to: (1) confirm spectroscopically the redshifts of a sample of massive galaxies selected with photometric redshifts z > 2.5; (2) investigate the properties of their stellar and interstellar media; (3) detect the presence of outflows, and measure their velocities. To achieve this, we analysed deep, high-resolution (R~2000) FORS2 rest-frame UV spectra for 11 targets. We confirmed that 9 out of 11 have spectroscopic redshifts z > 2.5. We also serendipitously found two mask fillers at redshift z > 2.5, which originally were assigned photometric redshifts 2.0 < z < 2.5. In the four highest-quality spectra we derived outflow velocities by fitting the absorption line profiles with models including multiple dynamical components. We found strongly asymmetric, high-ionisation lines, from which we derived outflow velocities ranging from 480 to 1518 km/s. The two galaxies with highest velocity show signs of AGN. We revised the spectral energy distribution fitting U-band through 8 micron photometry, including the analysis of a power-law component subtraction to identify the possible presence of active galactic nuclei (AGN). The revised stellar masses of all but one of our targets are >1e10 Msun, with four having stellar masses > 5e10 Msun. Three galaxies have a significant power-law component in their spectral energy distributions, which indicates that they host AGN. We conclude that massive galaxies are characterised by significantly higher velocity outflows than the typical Lyman break galaxies at z ~ 3. The incidence of high-velocity outflows (~40% within our sample) is also much higher than among massive galaxies at z < 1, which is consistent with the powerful star formation and nuclear activity that most massive galaxies display at z > 2.

Rest-frame ultra-violet spectra of massive galaxies at z=3: evidence for high-velocity outflows [Replacement]

Galaxy formation models invoke the presence of strong feedback mechanisms that regulate the growth of massive galaxies at high redshifts. In this paper we aim to: (1) confirm spectroscopically the redshifts of a sample of massive galaxies selected with photometric redshifts z > 2.5; (2) investigate the properties of their stellar and interstellar media; (3) detect the presence of outflows, and measure their velocities. To achieve this, we analysed deep, high-resolution (R~2000) FORS2 rest-frame UV spectra for 11 targets. We confirmed that 9 out of 11 have spectroscopic redshifts z > 2.5. We also serendipitously found two mask fillers at redshift z > 2.5, which originally were assigned photometric redshifts 2.0 < z < 2.5. In the four highest-quality spectra we derived outflow velocities by fitting the absorption line profiles with models including multiple dynamical components. We found strongly asymmetric, high-ionisation lines, from which we derived outflow velocities ranging between 480 and 1518 km/s. We revised the spectral energy distribution fitting U-band through 8 micron photometry, including the analysis of a power-law component subtraction to identify the possible presence of active galactic nuclei (AGN). The revised stellar masses of all but one of our targets are >1e10 Msun, with four having stellar masses > 5e10 Msun. Three galaxies have a significant power-law component in their spectral energy distributions, which indicates that they host AGN. We conclude that massive galaxies are characterised by significantly higher velocity outflows than the typical Lyman break galaxies at z ~ 3. The incidence of high-velocity outflows (~40% within our sample) is also much higher than among massive galaxies at z < 1, which is consistent with the powerful star formation and nuclear activity that most massive galaxies display at z > 2.

Rest-frame ultra-violet spectra of massive galaxies at z=3: evidence of high-velocity outflows [Replacement]

Galaxy formation models invoke the presence of strong feedback mechanisms that regulate the growth of massive galaxies at high redshifts. In this paper we aim to: (1) confirm spectroscopically the redshifts of a sample of massive galaxies selected with photometric redshifts z > 2.5; (2) investigate the properties of their stellar and interstellar media; (3) detect the presence of outflows, and measure their velocities. To achieve this, we analysed deep, high-resolution (R~2000) FORS2 rest-frame UV spectra for 11 targets. We confirmed that 9 out of 11 have spectroscopic redshifts z > 2.5. We also serendipitously found two mask fillers at redshift z > 2.5, which originally were assigned photometric redshifts 2.0 < z < 2.5. In the four highest-quality spectra we derived outflow velocities by fitting the absorption line profiles with models including multiple dynamical components. We found strongly asymmetric, high-ionisation lines, from which we derived outflow velocities ranging from 480 to 1518 km/s. The two galaxies with highest velocity show signs of AGN. We revised the spectral energy distribution fitting U-band through 8 micron photometry, including the analysis of a power-law component subtraction to identify the possible presence of active galactic nuclei (AGN). The revised stellar masses of all but one of our targets are >1e10 Msun, with four having stellar masses > 5e10 Msun. Three galaxies have a significant power-law component in their spectral energy distributions, which indicates that they host AGN. We conclude that massive galaxies are characterised by significantly higher velocity outflows than the typical Lyman break galaxies at z ~ 3. The incidence of high-velocity outflows (~40% within our sample) is also much higher than among massive galaxies at z < 1, which is consistent with the powerful star formation and nuclear activity that most massive galaxies display at z > 2.

Cosmological solutions in F(T) gravity with the presence of spinor fields

The presence of spinor fields is considered in the framework of some extensions of teleparallel gravity, where the Weitzenb\"ock connection is assumed. Some well known models as the Chaplygin gas and its generalizations are reconstructed in terms of a spinor field in the framework of teleparallel gravity. In addition, the {\Lambda}CDM model is also realized with the presence of a spinor field where a simple self-intercating term is considered and the corresponding action is reconstructed. Other cosmological solutions and the reconstruction of the gravitational action in terms of the scalar torsion is studied.

Cosmological solutions in F(T) gravity with the presence of spinor fields [Cross-Listing]

The presence of spinor fields is considered in the framework of some extensions of teleparallel gravity, where the Weitzenb\"ock connection is assumed. Some well known models as the Chaplygin gas and its generalizations are reconstructed in terms of a spinor field in the framework of teleparallel gravity. In addition, the {\Lambda}CDM model is also realized with the presence of a spinor field where a simple self-intercating term is considered and the corresponding action is reconstructed. Other cosmological solutions and the reconstruction of the gravitational action in terms of the scalar torsion is studied.

Inhomogeneities, loop quantum gravity corrections, constraint algebra and general covariance

Loop quantum gravity corrections, in the presence of inhomogeneities, can lead to a deformed constraint algebra. Such a deformation implies that the effective theory is no longer generally covariant. As a consequence, the geometrical concepts used in the classical theory lose their meaning. In the present paper we propose a method, based on canonical transformation on the phase space of the effective theory, to systematically recover the classical constraint algebra in the presence of the inverse triad corrections as well as in the presence of holonomy corrections. We show, by way of explicit example, that this also leads to the recovery of general covariance of the theory in the presence of inverse triad connections, implying that one can once again use the geometrical concepts to analyze the solutions in the presence of these quantum gravity corrections.

Inhomogeneities, loop quantum gravity corrections, constraint algebra and general covariance [Replacement]

Loop quantum gravity corrections, in the presence of inhomogeneities, can lead to a deformed constraint algebra. Such a deformation implies that the effective theory is no longer generally covariant. As a consequence, the geometrical concepts used in the classical theory lose their meaning. In the present paper we propose a method, based on canonical transformation on the phase space of the effective theory, to systematically recover the classical constraint algebra in the presence of the inverse triad corrections as well as in the presence of the holonomy corrections. We show, by way of explicit example, that this also leads to the recovery of general covariance of the theory in the presence of inverse triad corrections, implying that one can once again use the geometrical concepts to analyze the solutions in the presence of these quantum gravity corrections.

Inhomogeneities, loop quantum gravity corrections, constraint algebra and general covariance [Replacement]

Loop quantum gravity corrections, in the presence of inhomogeneities, can lead to a deformed constraint algebra. Such a deformation implies that the effective theory is no longer generally covariant. As a consequence, the geometrical concepts used in the classical theory lose their meaning. In the present paper we propose a method, based on canonical transformation on the phase space of the spherically symmetric effective theory, to systematically recover the classical constraint algebra in the presence of the inverse triad corrections as well as in the presence of the holonomy corrections. We show, by way of explicit example, that this also leads to the recovery of general covariance of the theory in the presence of inverse triad corrections, implying that one can once again use the geometrical concepts to analyze the solutions in the presence of these quantum gravity corrections.

Inhomogeneities, loop quantum gravity corrections, constraint algebra and general covariance [Replacement]

Loop quantum gravity corrections, in the presence of inhomogeneities, can lead to a deformed constraint algebra. Such a deformation implies that the effective theory is no longer generally covariant. As a consequence, the geometrical concepts used in the classical theory lose their meaning. In the present paper we propose a method, based on canonical transformation on the phase space of the spherically symmetric effective theory, to systematically recover the classical constraint algebra in the presence of the inverse triad corrections as well as in the presence of the holonomy corrections. We show, by way of explicit example, that this also leads to the recovery of general covariance of the theory in the presence of inverse triad corrections, implying that one can once again use the geometrical concepts to analyze the solutions in the presence of these quantum gravity corrections.

Ultrarelativistic electron states in a general background electromagnetic field [Replacement]

The feasibility of obtaining exact analytical results in the realm of QED in the presence of a background electromagnetic field is almost exclusively limited to a few tractable cases, where the Dirac equation in the corresponding background field can be solved analytically. This circumstance has restricted, in particular, the theoretical analysis of QED processes in intense laser fields to within the plane-wave approximation even at those high intensities, achievable experimentally only by tightly focusing the laser energy in space. Here, within the Wentzel-Kramers-Brillouin (WKB) or eikonal approximation, we construct analytically single-particle electron states in the presence of a background electromagnetic field of general space-time structure in the realistic assumption that the initial energy of the electron is the largest dynamical energy scale in the problem. The relatively compact expression of these states opens, in particular, the possibility of investigating analytically strong-field QED processes in the presence of spatially focused laser beams, which is of particular relevance in view of the upcoming experimental campaigns in this field.

Generation and evolution of stable stellar magnetic fields in young A-type stars

While the presence of magnetic fields on low-mass stars is attributed to a dynamo process essentially driven by convective motions, the existence of magnetic fields on intermediate-mass stars has very likely other reasons. Presuming that the fields we see are nearly constant in time, the paper focuses on the generation of stable magnetic configurations at the early stages of stellar evolution. The convective processing of an initial magnetic field during the pre-main-sequence phase is studied in a very simple model star. Azimuthal magnetic fields are found to be typical remnants in the upcoming radiative envelope after the convection has receded.

 

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