International Journal of Modern Physics D

Galactic winds constitute a primary feedback process in the ecology and evolution of galaxies. They are ubiquitously observed and exhibit a rich phenomenology, whose origin is actively investigated both theoretically and observationally. Cosmic rays have been widely recognized as a possible driving agent of galactic winds, especially in Milky–Way like galaxies. The formation of cosmic ray-driven winds is intimately connected with the microphysics of the cosmic ray transport in galaxies, making it an intrinsically non-linear and multiscale phenomenon. In this complex interplay, the cosmic ray distribution affects the wind launching and, in turns, is shaped by the presence of winds. In this review, we summarize the present knowledge of the physics of cosmic rays involved in the wind formation and of the wind hydrodynamics. We also discuss the theoretical difficulties connected with the study of cosmic ray-driven winds and possible future improvements and directions.

The search for the true ground state of the dense matter remains open since Bodmer, Terazawa and others raised the possibility of stable quark matter, boosted by Witten’s strange matter hypothesis in 1984. Within this proposal, the strange matter is assumed to be composed of $strange$ quarks in addition to the usual $up$s and $down$s, having an energy per baryon lower than the strangeless counterpart, and even lower than that of nuclear matter. In this sense, neutron stars should actually be strange stars. Later work showed that a paired, symmetric in flavor, color-flavor locked (CFL) state would be preferred to the one without any pairing for a wide range of the parameters (gap $\mathrm{\Delta }$, strange quark mass $m_s$ and bag constant B). We use an approximate, yet very accurate, CFL equation-of-state (EoS) that generalizes the MIT bag model to obtain two families of exact solutions for the static Einstein Field Equations (EFE) constructing families of anisotropic compact relativistic objects. In this fashion, we provide exact useful solutions directly connected with microphysics.

A spatially flat Friedmann–Robertson–Walker background with a general scale factor is considered. In this spacetime, the energy–momentum tensor of the scalar field with a general curvature coupling parameter is obtained. Using the Thermo Field Dynamics (TFD) formalism, the Stefan–Boltzmann law and the Casimir effect at finite temperature are calculated. The Casimir effect at zero temperature is also considered. The expansion of the universe changes these effects. A discussion of these modifications is presented.

We consider a multiscalar tensor cosmology model described by Friedmann–Robertson–Walker (FRW) spacetime with zero spatial curvature. Three specific scalar interaction potentials that characterize the model are analyzed under a set of coordinate transformations. By implication, we solve for the wave function of the universe, reduce the dimension of the underlying Hamiltonian system and consequently, establish analytical solutions of the multiscalar model’s field equations.

In the bibliography, a certain confusion arises in what regards to the classification of the gravitational theories into scalar–tensor theories (STT) and general relativity with a scalar field either minimally or nonminimally coupled to matter. Higher-derivatives Horndeski and beyond Horndeski theories that at first sight do not look like STT only add to the confusion. To further complicate things, the discussion on the physical equivalence of the different conformal frames in which a given scalar–tensor theory may be formulated, makes even harder to achieve a correct classification. In this paper, we propose a specific criterion for an unambiguous identification of STT and discuss its impact on the conformal transformations issue. The present discussion carries not only pedagogical but also scientific interest since an incorrect classification of a given theory as a scalar–tensor theory of gravity may lead to conceptual issues and to the consequent misunderstanding of its physical implications.

Based on the definition of the interior volume of spherically symmetry black holes, the interior volume of Schwarzschild–(Anti) de Sitter black holes is calculated. It is shown that with the cosmological constant ($\mathrm{\Lambda }$) increasing, the changing behaviors of both the position of the largest hypersurface and the interior volume for the Schwarzschild–Anti de Sitter black hole are the same as the Schwarzschild–de Sitter black hole. Considering a scalar field in the interior volume and Hawking radiation with only energy, the evolution relation between the scalar field entropy and Bekenstein–Hawking entropy is constructed. The results show that the scalar field entropy is approximately proportional to Bekenstein–Hawking entropy during Hawking radiation. Meanwhile, the proportionality coefficient is also regarded as a constant approximately with the increasing $\mathrm{\Lambda }$. Furthermore, considering $\mathrm{\Lambda }$ as a dynamical variable, the modified Stefan–Boltzmann law is proposed which can be used to describe the variation of both the mass and $\mathrm{\Lambda }$ under Hawking radiation. Using this modified law, the evolution relation between the two types of entropy is also constructed. The results show that the coefficient for Schwarzschild–de Sitter black holes is closer to a constant than the one for Schwarzschild–Anti de Sitter black holes during the evaporation process. Moreover, we find that for Hawking radiation carrying only energy, the evolution relation is a special case compared with the situation that the mass and $\mathrm{\Lambda }$ are both considered as dynamical variables.

Investigating the dark matter (DM) properties in the view of cosmic evolution is an important method in searching for DM. In this paper, we derive the modified Boltzmann equations and study how the elastic scattering between the DM particles and the free electrons in our universe influences the CMB and matter power spectra starting from a few basic assumptions. The results indicates that the scattering affects the small scales significantly, especially the CMB polarization power spectra. With this method, the coupling constant between DM and electrons can be constrained with CMB observational data and the results only depend on a few basic assumptions.

Geophysical application of large free-mass laser interferometers, which had been designed merely for the detection of gravitational radiation of an astrophysical nature, are considered. Despite the suspended mass-mirrors, these interferometers can be considered as two coordinate meters even at very low frequency ($f<10^{-3}$Hz) are rather accurate two-coordinate distance meters. In this case, the measurement of geodynamic deformations looks like a parallel product of long-term observations dictated by the task of the blind search for gravitational waves (GW) of extraterrestrial origin. Compared to conventional laser strain meters, gravitational interferometers have the advantage of an increased absolute value of the deformation signal due to the 3–4km baseline. The magnitude of the tidal variations of the baseline is 150–200microns, leading to conceive the observation of the fine structure of geodynamic disturbances. This paper presents the results of processing geophysical measurements made on a Virgo interferometer during test (technical) series of observations in 2007–2009.

The specific design of mass-mirrors suspensions in the Virgo gravitational interferometer also creates a unique possibility of separating gravitational and deformation perturbations through a recording mutual angular deviations of the suspensions of its central and end mirrors. It gives a measurement of the spatial derivative of the gravity acceleration along with the geoid of the Earth. In this mode, the physics of the interferometer is considered with estimates of the achievable sensitivity in the application to the classical problem of registration of oscillations of the inner Earth’s core.

The Israel junction conditions of a thin shell in the context of Einstein–Cartan gravity are revisited. It is shown that with a choice of the torsion discontinuity taken to be orthogonal to the hypersurface and consistent with the antisymmetric properties of torsion tensor and contorsion tensor, the generalized asymmetric surface energy–momentum tensor turns out to be tangent to the hypersurface while the resulting generalized Israel junction conditions are modified. The main differences to previous works are mentioned.