arXiv subjects

Manuel Malaver

Publications and source records attributed to Manuel Malaver.

16 recordsLinked to original sources

arXiv2023

Analysis of Local Anisotropy Fluctuations in Compact Objects

Mathematical modeling within the framework of the general theory of relativity has been used to explain the behavior and structure of massive objects as neutron stars, quasars, black holes, pulsars and white dwarfs and requires finding the exact solutions of the Einstein-Maxwell system. In this paper we study the effects induced by fluctuations of local anisotropy in a new family of anisotropic solutions depending on a parameter, with a specific value that provides a radial pressure having the same functional dependence on the radial coordinate as the Schwarzschild solution. It is shown the effect the functional dependence on the radial coordinate has in the occurrence of cracking within the sphere when anisotropy fluctuations are allowed.

gr-qc↗

arXiv2023

Some new relativistic charged models for compact objects with anisotropic pressure

In this paper, we found new classes of solutions to the Einstein-Maxwell field equations with matter anisotropic distribution incorporating a particular form of electric field intensity within the framework of general relativity. We use a metric potential or ansatz that depends on an adjustable parameter in order to get the new solutions. We generated new models of compact stars. Graphical analysis allows us to conclude that the new models satisfy all the physical characteristics for astrophysical objects and can be very useful in the study and description of compact structures. We obtained models consistent with two types of pulsars

gr-qc↗

arXiv2023

Some new models of anisotropic relativistic stars in linear and quadratic regime

Taking local anisotropy into consideration, in this paper, some new analytical models of relativistic anisotropic charged quark stars in linear and quadratic regime have been developed. The Einstein-Maxwell field equations have been solved with a particular form of metric potential and electric field intensity. The plots generated show that physical variables such as metric potentials, radial pressure, energy density, charge density, anisotropy, radial speed sound are consistent with realistic stellar models. We obtained some models consistent with stellar objects as 4U 1538-52, Cyg X-2, OGLE-TR-122b and red dwarf Proxima Centauri.

gr-qc↗

arXiv2023

Study of Compact Stars with Buchdahl Potential in 5-D Einstein-Gauss-Bonnet Gravity

In this paper, we have presented a compact object model in the framework of Einstein-Gauss-Bonnet gravity (EGB) with a linear equation of state considering a metric potential proposed for Buchdahl (1959). The new obtained models satisfy all physical requirements of a physically reasonable stellar object. We analyzed the effect of the Gauss-Bonnet coupling constant α on the main physical characteristics of the model. We checked that the radial pressure, energy density and anisotropy are well defined and are regular in the interior of the star and are dependent of the values of the coupling constant.

gr-qc↗

arXiv2022

Charged Dark Energy Stars in a Finch-Skea Spacetime

In this paper we obtained some spherically stellar configurations that represent new models of dark energy stars specifying particular forms for gravitational potential and the electric field intensity which allows solve the Einstein-Maxwell field equations. We have chosen the metric potential proposed by Finch and Skea (1989). We found that the radial pressure, the anisotropy factor, energy density, metric coefficients, mass function, charge density are regular and well behaved in the stellar interior but the causality conditions and of strong energy are not satisfied. These models have great application in physics and cosmology due to the fact that several independent observations indicate that the universe is in a phase of accelerated expansion which can be explained by the presence of dark energy that has not been detected

gr-qc↗

arXiv2022

Analytical Model of Compact Star with a new version of Modified Chaplygin Equation of State

In this paper we found a new model for compact star with anisotropic matter distribution considering the new version of Chaplygin fluid equation of state of Errehymy and Daoud (2021). We specify the particular form of the metric potential proposed for Thirukanesh and Ragel (2012) and generalized for Malaver (2014) in order to integrate the Einstein`s field equations. The obtained model satisfies all physical properties expected in a realistic star. The radial pressure, energy density, metric coefficients, anisotropy and mass are well defined and are regular in the stellar interior. The results of this research can be useful in the development and description of new models of compact structures.

gr-qc↗

arXiv2020

Mixed convective in an axisymmetric magneto flow owing to MoS2-GO hybrid nanoliquids in H2O based liquid through an upright cylinder with shape factor

In the presented paper, a comprehensive study will be done on shape factor analysis of MoS2-GO in H2O-C2H6O2 based hybrid nanoliquids associated with effect and influence of transverse magnetic field and thermal radiation. The effect of variation in different parameters and nanoliquids shapes under temperature and velocity distribution is explored and also non-linear thermal radiation will be analyzed. Algorithms are introduced in proportion to mathematical modeling based on their numerical results and comparative curves for further explanation. In addition, it will be done research for influence and effect of new significant parameters emerged to the model to do sensitivity analysis and also their output results are demonstrated, examined and compared together by presenting graphs and tables. Based on detailed discussions, authentication of attained results designates the high accuracy of applied methods deployed to solve presented model in the paper. Our results satisfy that our used approach is accurate, highly reliable and also effective. All mentioned steps will be described throughout the literature.

physics.gen-ph↗

arXiv2019

Carnot heat engine efficiency with a paramagnetic gas

Considering ideal paramagnetic medium, in this paper we deduced an expression for the thermal efficiency of Carnot heat engine with a paramagnetic gas as working substance. We found that the efficiency depends on the limits of maximum and minimal temperature imposed on the Carnot cycle, as in the ideal gas, photon gas and variable Chaplygin gas.

cond-mat.stat-mech↗

arXiv2019

Vapor Pressure in a Paramagnetic Solid?

In this paper, we obtain an analytical expression for the vapor pressure of a paramagnetic solid for high temperatures. We have considered the behavior of magnetic materials in the presence of an external magnetic field using the thermodynamical analysis and the elements of statistical mechanics in microscopic systems. We found that the vapor pressure depends on the magnetic susceptibility of material and the external field applied.

physics.gen-ph↗

arXiv2015

Relativistic Modeling of Quark Stars with Tolman IV Type Potential

In this paper, we studied the behavior of relativistic objects with anisotropic matter distribution considering Tolman IV form for the gravitational potential Z. The equation of state presents a quadratic relation between the energy density and the radial pressure. New exact solutions of the Einstein-Maxwell system are generated. A physical analysis of electromagnetic field indicates that is regular in the origin and well behaved. We show as the presence of an electrical field modifies the energy density, the radial pressure and the mass of the stellar object and generates a singular charge density.

physics.gen-ph↗

arXiv2015

Modeling anisotropic charged neutron star in isotropic coordinates

We present a spherically symmetric solution of the general relativistic field equations in isotropic coordinates for charged fluid with pressure anisotropy, compatible with a super dense star modeling. Further, we have constructed an anisotropic model of super dense star with all degree of suitability. We also observed that by increasing anisotropy, the maximum mass of super dense stars also decreases.

physics.gen-ph↗

arXiv2014

Anisotropic fluid star model in isotropic coordinates

We present a spherically symmetric solution of the general relativistic field equations in isotropic coordinates for anisotropic neutral fluid, compatible with a super dense star modeling by considering a specific choice of anisotropy factor that includes a positive constant defined as anisotropy parameter, which varies the relation between the radial and tangential pressure. Further, we have constructed a super-dense star model with all degree of suitability. We have found that the maximum mass decreases with the increase of anisotropy parameter. The robustness of our result is that it matches with the recent discoveries.

gr-qc↗

arXiv2014

Models for Quark Stars with Charged Anisotropic Matter

In this paper, we found new exact solutions to the Einstein- Maxwell system of equations within the framework of MIT Bag Model considering a particular form for the measure of anisotropy and a gravitational potential which depends on an adjustable parameter α. Variables as the energy density, radial pressure, tangential pressure, electric field intensity and the metric functions are written in terms of elementary and polinominal functions. We show that the form chosen for the gravitational potential and the anisotropy allows obtain physically acceptable solutions with any value of the adjustable parameter.

physics.gen-ph↗

arXiv2014

Quark star model with charge distributions

In this paper, we studied the behavior of relativistic objects with anisotropic matter distribution inthe presence of an electric field considering a gravitational potential Z(x) of Thirukkanesh and Ragel (2013) which depends on an adjustable parameter n. The equation of state presents a quadratic relation between the energy densityand the radial pressure. New exact solutions of the Einstein-Maxwell system are generated. A physical analysis of electromagnetic field indicates that is regular in the origin and well behaved. We show as a variation of the adjustable parameter n causes a modification in the charge density, the radial pressure and the mass of the stellar object.

gr-qc↗

arXiv2014

Strange Quark Star Model with Quadratic Equation of State

In this paper, we studied the behaviour of compact relativistic objects with anisotropic matter distribution considering quadratic equation of state of Feroze and Siddiqui (2011). We specify the gravitational potential Z(x) in order to integrate the fields equations and there has been calculated the energy density, the radial pressure, the anisotropy and the mass function. The new solutions to the Einstein-Maxwell system of equations are found in term of elementary functions. For n=2, we have obtained the expressions for mass function, energy density, radius and metric functions of the model of Thirukkanesh and Ragel (2012) with polytropic equation of state.

gr-qc↗

arXiv2014

Some new models for strange quark stars with isotropic pressure

We found new class of solutions to the Einstein-Maxwell system of equations for charged quark matter within the framework of MIT Bag Model considering a gravitational potential Z(x) proposed by Thirukkanesh and Ragel (2013), which depends on an adjustable parameter n. Variables as the energy density, charge density, pressure and the metric functions are written in terms of elementary and polinominal functions. We show that the form chosen for the gravitational potential allows obtain physically acceptable solutions with any value of the adjustable parameter.

gr-qc↗