Intrinsically symmetric cosmological model in the presence of dissipative fluids

Based upon the intrinsic symmetries approach to inhomogeneous cosmologies, we propose an exact solution to Einstein’s field equations where the spatial sections are flat and the source is a nonperfect fluid such that the dissipative terms can be written in terms of spatial gradients of the energy density under a suitable choice of the coordinate system. It is shown through the calculation of the luminosity distance as a function of the redshift that the presence of such inhomogeneities may lead to an effective deceleration parameter compatible with either the standard [Formula: see text]CDM model or LTB models depending on the choice of boundary conditions with no exotic matter. This fact is another evidence that different inhomogeneous models should be carefully investigated in order to verify which model may be compatible with observations and still be as close as possible to the standard model regarding the underlying assumptions, without resorting necessarily to exotic matter components.

Study of voltages in inhomogeneous models of supplied combined coatings by the polarization-optica method for monitoring their state

The polarization-optical method for studying stresses in heterogeneous models of combined deposited coatings is considered. The physical foundations of the method and its essence are described. Investigations of the tense state of coatings on heterogeneous models made of viscoelastic materials are presented. Creep curves were obtained, on the basis of which the dependence of specific deformation δ(t) was built, from which the values of the isochron module E2(t) and the price of the strip σ0.2 (t) as a function of time for viscoelastic material were determined.

Cosmological evolution of Tsallis holographic dark energy model in LTB inhomogeneous gravity

The aim of this work is to analyze the modified form of holographic dark energy (DE) density suggested by Tsallis and Cirto within inhomogeneous models of the universe. This DE model is applied to IR cutoff equals the Hubble horizon. Some basic cosmological functions, such as the Hubble function, the deceleration function and the equation of state parameter, are reconstructed by choosing specific values of certain numerical parameters in this model. The stability of the model is studied by considering the square of sound speed and the strong, the weak and the dominant energy conditions (DEC). In addition, the variation of the diagnostic Omega, [Formula: see text] and [Formula: see text] parameters with the redshift and space are studied. The obtained results show a close behavior to that of the cosmological constant DE universe so it can be compared well with the recent observations.

Thesaurus Theoriis Circa Gravitatis et Cetera

<p><em>Thesaurus Theoriis Circa Gravitatis et Cetera</em> is a compilation subdivided into two chapters, containing the complete research developed during author's post-doctoral period at the Brazilian Center of Physics Research - CBPF, Rio de Janeiro (2016 - 2017). From the heated discussions that took place in a climate of intense knowledge exchange, additions were made to the original text, making it more translucent to the readers.</p><p>In the first chapter, the lecture notes related to the Summer Formative Activities -- 2017 were meant to compile the main ideas on gauge field theory and modern cosmology, showing the recent contributions of the author in these areas, especially in classical thermodynamics, supergravity and quantum gravity. Although the author has conducted the work without wishing to exhaust the issues in question, this synthesis provides some essential formal aspects for further studies, with relevant and updated references, as well as indications of classical readings. Special attention was given to author's application of Lyra's geometry, because of its growing importance in quantum cosmology, and to the so-called &lt;&lt;paleogravity&gt;&gt;, a model of supergravity developed by the author with the purpose to offer a classical representation for supergravity that could be made compatible with the quantum theory of spacetime also developed by himself. Also in general cosmology, the emphasis was on inhomogeneous models because of the debate that they open on the validity of the standard model. In this sense, the author presented his perturbative formalism of weak gravitational lensing by defining an inhomogeneous cosmological refractive index within a Lemaître-Tolman universe. Lastly, some remarks on Stephani cosmology were organized in order to expose the most significant features of this approach. During the reading, it shall be possible to observe some title marks indicating items of interest, as well as small side texts with outgivings of renowned authors.</p><p>In the second chapter, the author expanded the discussion about the quantization of spacetime, previously opened, deepening his phenomenological analysis at the surroundings of supermassive bodies with the aid of the formalism of Green's functions. This approach also opens the way for a broader and dialectical debate on quantum gravity and supergravity, seeking to rescue a physical discourse and not merely the math exercise which has been predominant in some research groups.</p><p>The author is immensely grateful to the colleagues and external participants for the contributions and affection with which he was received and from which a community of collaborative studies was formed on the most important topics in modern physics. Special thanks goes to our esteemed Professor Helayël, to whom the author directs his highest respects and wishes for a long and brilliant future.</p>

Hybrid models in loop quantum cosmology

In the framework of Loop Quantum Cosmology (LQC), inhomogeneous models are usually quantized by means of a hybrid approach that combines loop quantization techniques with standard quantum field theory methods. This approach is based on a splitting of the phase space in a homogeneous sector, formed by global, zero-modes and an inhomogeneous sector, formed by the remaining, infinite number of modes, that describe the local degrees of freedom. Then, the hybrid quantization is attained by adopting a loop representation for the homogeneous gravitational sector, while a Fock representation is used for the inhomogeneities. The zero-mode of the Hamiltonian constraint operator couples the homogeneous and inhomogeneous sectors. The hybrid approach, therefore, is expected to provide a suitable quantum theory in regimes where the main quantum effects of the geometry are those affecting the zero-modes, while the inhomogeneities, still being quantum, can be treated in a more conventional way. This hybrid strategy was first proposed for the simplest cosmological midisuperspaces: the Gowdy models, and it has been later applied to the case of cosmological perturbations. This paper reviews the construction and main applications of hybrid LQC.

Influence of Torso Model Complexity on the Noninvasive Localization of Ectopic Ventricular Activity

Location of premature ectopic ventricular activity was assessed noninvasively in five patients using integral body surface potential maps and inverse solution in terms of a single dipole. Precision of the inverse solution was studied using three different torso models: homogeneous torso model, inhomogeneous torso model including lungs and heart ventricles and inhomogeneous torso model including lungs, heart ventricles and atria, aorta and pulmonary artery. More stable results were obtained using the homogeneous model. However, in some patients the location of the resulting dipole representing the focus of ectopic activity was shifted between solutions using the homogeneous and inhomogeneous models. Comparison of solutions with inhomogeneous torso models did not show significantly different dispersions, but localization of the focus was better when a torso model including atria and arteries was used. The obtained results suggest that presented noninvasive localization of the ectopic focus can be used to shorten the time needed for successful ablation and to increase its success rate.