Màrius Fullana - Academia.edu (original) (raw)

Papers by Màrius Fullana

Research paper thumbnail of Diseño curricular de las asignaturas básicas, desde el punto de vista socio-profesional

La adaptacion de los planes de estudio al nuevo espacio europeo de educacion, esta exigiendo al p... more La adaptacion de los planes de estudio al nuevo espacio europeo de educacion, esta exigiendo al profesorado un importante esfuerzo de profundizacion en el diseno curricular de sus respectivas asignaturas, tanto para su propio desarrollo interno, como para enmarcarlas coordinadamente dentro de un proyecto formativo global, mas proximo a las necesidades socio – economico – profesionales del entorno europeo. Una de las principales recomendaciones de ANECA respecto de este tema es clara: Es necesario tener en cuenta de manera prioritaria las competencias profesionales, a la hora de realizar el diseno de los planes de estudio universitarios. En esta linea los autores venimos trabajando en la elaboracion de una metodologia cientifica para medir la incidencia de las asignaturas basicas: matematicas, fisica, quimica, descriptiva, dibujo, etc. en las diferentes ingenierias, como herramientas y fundamento de las mismas. Por otra parte, tambien estamos desarrollando una metodologia para la int...

Research paper thumbnail of On the estimation and detection of the Rees–Sciama effect

Monthly Notices of the Royal Astronomical Society, 2016

Maps of the Rees-Sciama (RS) effect are simulated using the parallel N-body code, HYDRA, and a ru... more Maps of the Rees-Sciama (RS) effect are simulated using the parallel N-body code, HYDRA, and a run-time ray-tracing procedure. A method designed for the analysis of small, square cosmic microwave background (CMB) maps is applied to our RS maps. Each of these techniques has been tested and successfully applied in previous papers. Within a range of angular scales, our estimate of the RS angular power spectrum due to variations in the peculiar gravitational potential on scales smaller than 42/h megaparsecs is shown to be robust. An exhaustive study of the redshifts and spatial scales relevant for the production of RS anisotropy is developed for the first time. Results from this study demonstrate that (i) to estimate the full integrated RS effect, the initial redshift for the calculations (integration) must be greater than 25, (ii) the effect produced by strongly non-linear structures is very small and peaks at angular scales close to 4.3 arcmin, and (iii) the RS anisotropy cannot be detected either directly-in temperature CMB maps-or by looking for cross-correlations between these maps and tracers of the dark matter distribution. To estimate the RS effect produced by scales larger than 42/h megaparsecs, where the density contrast is not strongly non-linear, high accuracy N-body simulations appear unnecessary. Simulations based on approximations such as the Zel'dovich approximation and adhesion prescriptions, for example, may be adequate. These results can be used to guide the design of future RS simulations.

Research paper thumbnail of CMB Anisotropies Generated by Nonlinear Cosmological Structures

Some Topics on General Relativity and Gravitational Radiation, 1997

Research paper thumbnail of Spots on the Microwave Background

Research paper thumbnail of Some Remarks on CMB Anisotropies in Open Universes

Astrophysical letters & communications

Research paper thumbnail of Frontiers of Fundamental Physics

Research paper thumbnail of Making Maps of the Rees-Sciama Effect

Frontiers of Fundamental Physics, 2006

In the begining, matter and radiation coupled Primeval plasma with protons and electrons not in a... more In the begining, matter and radiation coupled Primeval plasma with protons and electrons not in atoms Photons not travel freely, continuous interactions with plasma Universe was opaque Expansion: Universe cooled and became transparent Recombination: protons captured electrons and formed atoms Decoupling: between matter and radiation at redshift

Research paper thumbnail of On the microwave background anisotropies produced by nonlinear voids

The Astrophysical Journal, 1993

The Tolman-Bondi solution of the Einstein equations is used to study the microwave background ani... more The Tolman-Bondi solution of the Einstein equations is used to study the microwave background anisotropy produced by a pressureless spherical cosmological inhomogeneity. Our method improves on previous ones because it does not involve any approximating condition and it allows us to assume the following: (1) a general Friedmann-Robertson-Walker background, (2) an arbitrary relative location of the observer and the inhomogeneity,

Research paper thumbnail of On the microwave background anisotropy produced by Great Attractor-like structures

The Astrophysical Journal Supplement Series, 1994

The Tolman-Bondi solution of the Einstein equations is used in order to model the time evolution ... more The Tolman-Bondi solution of the Einstein equations is used in order to model the time evolution of the void observed in Boötes. The present density contrast of the central region (∼ −0.75) and its radius (∼ 30h −1 Mpc) are fixed, while the density parameter of the Universe, the amplitude of the density contrast inside the void wall, the width of this wall and the distance from the void centre to the Local Group are appropriately varied. The microwave background anisotropy produced by Boötes-like voids is estimated for a significant set of locations. All the voids are placed far from the last scattering surface. It is shown that the anisotropy generated by these voids strongly depends on the density parameter, the wall structure and the void location. The Doppler dipole and quadrupole are subtracted and the residual anisotropy is calculated. In the case of some isolated Boötes-like voids placed at redshifts between 1 and 10 in an open universe with density parameter Ω 0 = 0.2, the residual anisotropy appears to be a few times 10 −6 on scales of a few degrees. This anisotropy is about one order of magnitude greater than previous estimates corresponding to other cases. The anisotropy produced by a distribution of voids is qualitatively studied in the light of this result. Comparisons with previous estimates are discussed.

Research paper thumbnail of Space time geometry in the atomic hydrogenoid system. Approach to a dust relativistic model from causal quantum mechanics

Revista Mexicana de Física, 2018

Weintend to use the description oftheelectron orbital trajectory in the de Broglie-Bohm (dBB) the... more Weintend to use the description oftheelectron orbital trajectory in the de Broglie-Bohm (dBB) theory to assimilate to a geodesiccorresponding to the General Relativity (GR) and get from itphysicalconclusions. ThedBBapproachindicatesustheexistenceof a non-local quantumfield (correspondingwiththequantumpotential), anelectromagneticfield and a comparativelyveryweakgravitatoryfield, togetherwith a translationkineticenergyofelectron. Ifweadmitthatthosefields and kineticenergy can deformthespace time, according to Einstein'sfield equations (and to avoidtheviolationoftheequivalenceprinciple as well), we can madethehypothesisthatthegeodesicsof this space-time deformation coincide withtheorbitsbelonging to thedBBapproach (hypothesisthat is coherentwiththestabilityofmatter). Fromit, we deduce a general equation that relates thecomponentsofthemetric tensor. Thenwe find anappropriatemetric for it, bymodificationofanexactsolutionofEinstein'sfield equations, whichcorresponds to dust in cy...

Research paper thumbnail of 1 a General Study of the Mathematical Impact in Technical Curricula

The most of the authors about the topic of University Curricula Design, point out the importance ... more The most of the authors about the topic of University Curricula Design, point out the importance of defining the profesional fields, where the future graduates are going to develop their jobs, in a coherent and up-to-date manner, with the aim of using this information in order to select the contents of the different subjects of the syllabus, which is being tried to be constructed. In the case of “instrumental ” disciplines such as Mathematics, Physics or Design, a special treatment is required in order to accomplish this problem, since their relation with the real-life socio-economic activities is less evident. Here is the topic we deal with in this paper. In order to solve it we propose a procedure which allows us to define the skills and knowledge to be acquired by engineering students, in relation with the “instrumental ” subjects, with the goal of selecting the most suitable contents of their syllabus, and of scheduleing them in an interdisciplinary way. The final purpose is to ...

Research paper thumbnail of A General Study Of The Mathematical Impact In Technical Curricula

The most of the authors about the topic of University Curricula Design, point out the importance ... more The most of the authors about the topic of University Curricula Design, point out the importance of defining the profesional fields, where the future graduates are going to develop their jobs, in a coherent and up-to-date manner, with the aim of using this information in order to select the contents of the different subjects of the syllabus, which is being tried to be constructed. In the case of "instrumental" disciplines such as Mathematics, Physics or Design, a special treatment is required in order to accomplish this problem, since their relation with the reallife socio-economic activities is less evident. Here is the topic we deal with in this paper. In order to solve it we propose a procedure which allows us to define the skills and knowledge to be acquired by engineering students, in relation with the "instrumental" subjects, with the goal of selecting the most suitable contents of their syllabus, and of scheduleing them in an interdisciplinary way. The fin...

Research paper thumbnail of On the sources of the late integrated Sachs-Wolfe effect

In some scenarios, the peculiar gravitational potential of linear and mildly nonlinear structures... more In some scenarios, the peculiar gravitational potential of linear and mildly nonlinear structures depends on time and, as a result of this dependence, a late integrated Sachs-Wolfe effect appears. Here, an appropriate formalism is used which allows us to improve on the analysis of the spatial scales and locations of the main cosmological inhomogeneities producing this effect. The study is performed in the framework of the currently preferred flat model with cosmological constant, and it is also developed in an open model for comparisons. Results from this analysis are used to discuss the contribution of Great Attractor-like objects, voids, and other structures to the CMB anisotropy. Subject headings: cosmic microwave background—cosmology:theory — large-scale structure of the universe—methods:numericalPACS: 98.70.Vc, 98.65.-r, 98.65.Dx, 95.75.Pq 1 1

Research paper thumbnail of Índices De Un Sistema Generalizado De Control

Localización: Actas: XVI CEDYA Congreso de Ecuaciones Diferenciales y Aplicaciones, VI CMA Congre... more Localización: Actas: XVI CEDYA Congreso de Ecuaciones Diferenciales y Aplicaciones, VI CMA Congreso de Matemática Aplicada, Las Palmas de Gran Canaria, 21-24 septiembre 1999/coord. por Gabriel Winter Althaus, Rafael Alejandro Montenegro Armas, Gustavo ...

Research paper thumbnail of Yukawa effects on the mean motion of an orbiting body

Astrophysics and Space Science, 2016

In today's gravity research there exist few modified gravitational theories which among o... more In today's gravity research there exist few modified gravitational theories which among other things predict the existence of a Yukawa-type correction to the classical gravitational potential. In this paper we study the Yukawa effect on the mean motion if any in a two-body scenario, assuming the influence of the existence of a possible Yukawa correction in the gravitational force of a primary. For that, we derive an equation in order to approximate the mean motion for secondary time rate of change of the orbiting body and its total variation over one revolution, under the influence of the non-Newtonian radial acceleration. Numerical results for Mercury and the companion star of the pulsar PSR 1913 + 16 are calculated. For specific values of the parameters α and λ, as given in the bibliography we have found that there is no corresponding Yukawa effect affecting the mean motion of the planet Mercury. On the other hand it appears that there is a periodic Yukawa effect that affects the mean motion of PSR + 16 whose maximum numerical value occurs when the eccentric anomaly is equal to 180 • .

Research paper thumbnail of On the horizons in a viable vector-tensor theory of gravitation

Astrophysics and Space Science, 2015

A certain vector-tensor (VT) theory of gravitation was tested in previous papers. In the backgrou... more A certain vector-tensor (VT) theory of gravitation was tested in previous papers. In the background universe, the vector field of the theory has a certain energy density, which is appropriate to play the role of vacuum energy (cosmological constant). Moreover, this background and its perturbations may explain the temperature angular power spectrum of the cosmic microwave background (CMB) obtained with WMAP (Wilkinson Map Anisotropy Probe), and other observations, as e.g., the Ia supernova luminosities. The parametrized post-Newtonian limit of the VT theory has been proved to be identical to that of general relativity (GR), and there are no quantum ghosts and classical instabilities. Here, the stationary spherically symmetric solution, in the absence of any matter content, is derived and studied. The metric of this solution is formally identical to that of the Reissner-Nordströmde Sitter solution of GR, but the role of the electrical charge is played by a certain quantity Γ depending on both the vector field and the parameters of the VT theory. The black hole and cosmological horizons are discussed. The radius of the VT black hole horizon deviates with respect to that of the Kottler-Schwarzschildde Sitter radius. Realistic relative deviations depend on Γ and reach maximum values close to 30 per cent. For large enough Γ values, there is no any black hole horizon, but only a cosmological horizon. The radius of this

Research paper thumbnail of On the sources of the late integrated Sachs-Wolfe effect

New Astronomy, 2000

In some scenarios, the peculiar gravitational potential of linear and mildly nonlinear structures... more In some scenarios, the peculiar gravitational potential of linear and mildly nonlinear structures depends on time and, as a result of this dependence, a late integrated Sachs-Wolfe effect appears. Here, an appropriate formalism is used which allows us to improve on the analysis of the spatial scales and locations of the main cosmological inhomogeneities producing this effect. The study is performed in the framework of the currently preferred flat model with cosmological constant, and it is also developed in an open model for comparisons. Results from this analysis are used to discuss the contribution of Great Attractor-like objects, voids, and other structures to the CMB anisotropy. Subject headings: cosmic microwave background-cosmology:theory-large-scale structure of the universe-methods:numerical

Research paper thumbnail of Reachability and observability indices of a discrete-time periodic descriptor system

Applied Mathematics and Computation, 2004

This work introduces the indices of reachability and observability of a discrete-time periodic de... more This work introduces the indices of reachability and observability of a discrete-time periodic descriptor linear system. The reachability and observability indices at time s, s 2 Z, of a periodic collection of nonproper transfer matrices are characterized. Using a special kind of coprime decompositions, the relationship between the indices at consecutive times is analyzed and an algorithm is constructed.

Research paper thumbnail of Some invariants of discrete-time descriptor systems

Applied Mathematics and Computation, 2002

Many papers analyze the role of controllability and observability indices of normal linear system... more Many papers analyze the role of controllability and observability indices of normal linear systems in control theory and their use in the study of structural properties. This work introduces these indices for linear discrete-time descriptor systems. Such indices are studied in two different ways, by means of the state-space approach and using its transfer matrix. A canonical form of the state-space system and a special decomposition of the nonproper transfer matrix are considered in order to discuss the reachability and observability indices.

Research paper thumbnail of Reachability and observability indices of a discrete-time periodic descriptor system

Applied Mathematics and Computation, Jun 4, 2004

This work introduces the indices of reachability and observability of a discrete-time periodic de... more This work introduces the indices of reachability and observability of a discrete-time periodic descriptor linear system. The reachability and observability indices at time s, s 2 Z, of a periodic collection of nonproper transfer matrices are characterized. Using a special kind of coprime decompositions, the relationship between the indices at consecutive times is analyzed and an algorithm is constructed.

Research paper thumbnail of Diseño curricular de las asignaturas básicas, desde el punto de vista socio-profesional

La adaptacion de los planes de estudio al nuevo espacio europeo de educacion, esta exigiendo al p... more La adaptacion de los planes de estudio al nuevo espacio europeo de educacion, esta exigiendo al profesorado un importante esfuerzo de profundizacion en el diseno curricular de sus respectivas asignaturas, tanto para su propio desarrollo interno, como para enmarcarlas coordinadamente dentro de un proyecto formativo global, mas proximo a las necesidades socio – economico – profesionales del entorno europeo. Una de las principales recomendaciones de ANECA respecto de este tema es clara: Es necesario tener en cuenta de manera prioritaria las competencias profesionales, a la hora de realizar el diseno de los planes de estudio universitarios. En esta linea los autores venimos trabajando en la elaboracion de una metodologia cientifica para medir la incidencia de las asignaturas basicas: matematicas, fisica, quimica, descriptiva, dibujo, etc. en las diferentes ingenierias, como herramientas y fundamento de las mismas. Por otra parte, tambien estamos desarrollando una metodologia para la int...

Research paper thumbnail of On the estimation and detection of the Rees–Sciama effect

Monthly Notices of the Royal Astronomical Society, 2016

Maps of the Rees-Sciama (RS) effect are simulated using the parallel N-body code, HYDRA, and a ru... more Maps of the Rees-Sciama (RS) effect are simulated using the parallel N-body code, HYDRA, and a run-time ray-tracing procedure. A method designed for the analysis of small, square cosmic microwave background (CMB) maps is applied to our RS maps. Each of these techniques has been tested and successfully applied in previous papers. Within a range of angular scales, our estimate of the RS angular power spectrum due to variations in the peculiar gravitational potential on scales smaller than 42/h megaparsecs is shown to be robust. An exhaustive study of the redshifts and spatial scales relevant for the production of RS anisotropy is developed for the first time. Results from this study demonstrate that (i) to estimate the full integrated RS effect, the initial redshift for the calculations (integration) must be greater than 25, (ii) the effect produced by strongly non-linear structures is very small and peaks at angular scales close to 4.3 arcmin, and (iii) the RS anisotropy cannot be detected either directly-in temperature CMB maps-or by looking for cross-correlations between these maps and tracers of the dark matter distribution. To estimate the RS effect produced by scales larger than 42/h megaparsecs, where the density contrast is not strongly non-linear, high accuracy N-body simulations appear unnecessary. Simulations based on approximations such as the Zel'dovich approximation and adhesion prescriptions, for example, may be adequate. These results can be used to guide the design of future RS simulations.

Research paper thumbnail of CMB Anisotropies Generated by Nonlinear Cosmological Structures

Some Topics on General Relativity and Gravitational Radiation, 1997

Research paper thumbnail of Spots on the Microwave Background

Research paper thumbnail of Some Remarks on CMB Anisotropies in Open Universes

Astrophysical letters & communications

Research paper thumbnail of Frontiers of Fundamental Physics

Research paper thumbnail of Making Maps of the Rees-Sciama Effect

Frontiers of Fundamental Physics, 2006

In the begining, matter and radiation coupled Primeval plasma with protons and electrons not in a... more In the begining, matter and radiation coupled Primeval plasma with protons and electrons not in atoms Photons not travel freely, continuous interactions with plasma Universe was opaque Expansion: Universe cooled and became transparent Recombination: protons captured electrons and formed atoms Decoupling: between matter and radiation at redshift

Research paper thumbnail of On the microwave background anisotropies produced by nonlinear voids

The Astrophysical Journal, 1993

The Tolman-Bondi solution of the Einstein equations is used to study the microwave background ani... more The Tolman-Bondi solution of the Einstein equations is used to study the microwave background anisotropy produced by a pressureless spherical cosmological inhomogeneity. Our method improves on previous ones because it does not involve any approximating condition and it allows us to assume the following: (1) a general Friedmann-Robertson-Walker background, (2) an arbitrary relative location of the observer and the inhomogeneity,

Research paper thumbnail of On the microwave background anisotropy produced by Great Attractor-like structures

The Astrophysical Journal Supplement Series, 1994

The Tolman-Bondi solution of the Einstein equations is used in order to model the time evolution ... more The Tolman-Bondi solution of the Einstein equations is used in order to model the time evolution of the void observed in Boötes. The present density contrast of the central region (∼ −0.75) and its radius (∼ 30h −1 Mpc) are fixed, while the density parameter of the Universe, the amplitude of the density contrast inside the void wall, the width of this wall and the distance from the void centre to the Local Group are appropriately varied. The microwave background anisotropy produced by Boötes-like voids is estimated for a significant set of locations. All the voids are placed far from the last scattering surface. It is shown that the anisotropy generated by these voids strongly depends on the density parameter, the wall structure and the void location. The Doppler dipole and quadrupole are subtracted and the residual anisotropy is calculated. In the case of some isolated Boötes-like voids placed at redshifts between 1 and 10 in an open universe with density parameter Ω 0 = 0.2, the residual anisotropy appears to be a few times 10 −6 on scales of a few degrees. This anisotropy is about one order of magnitude greater than previous estimates corresponding to other cases. The anisotropy produced by a distribution of voids is qualitatively studied in the light of this result. Comparisons with previous estimates are discussed.

Research paper thumbnail of Space time geometry in the atomic hydrogenoid system. Approach to a dust relativistic model from causal quantum mechanics

Revista Mexicana de Física, 2018

Weintend to use the description oftheelectron orbital trajectory in the de Broglie-Bohm (dBB) the... more Weintend to use the description oftheelectron orbital trajectory in the de Broglie-Bohm (dBB) theory to assimilate to a geodesiccorresponding to the General Relativity (GR) and get from itphysicalconclusions. ThedBBapproachindicatesustheexistenceof a non-local quantumfield (correspondingwiththequantumpotential), anelectromagneticfield and a comparativelyveryweakgravitatoryfield, togetherwith a translationkineticenergyofelectron. Ifweadmitthatthosefields and kineticenergy can deformthespace time, according to Einstein'sfield equations (and to avoidtheviolationoftheequivalenceprinciple as well), we can madethehypothesisthatthegeodesicsof this space-time deformation coincide withtheorbitsbelonging to thedBBapproach (hypothesisthat is coherentwiththestabilityofmatter). Fromit, we deduce a general equation that relates thecomponentsofthemetric tensor. Thenwe find anappropriatemetric for it, bymodificationofanexactsolutionofEinstein'sfield equations, whichcorresponds to dust in cy...

Research paper thumbnail of 1 a General Study of the Mathematical Impact in Technical Curricula

The most of the authors about the topic of University Curricula Design, point out the importance ... more The most of the authors about the topic of University Curricula Design, point out the importance of defining the profesional fields, where the future graduates are going to develop their jobs, in a coherent and up-to-date manner, with the aim of using this information in order to select the contents of the different subjects of the syllabus, which is being tried to be constructed. In the case of “instrumental ” disciplines such as Mathematics, Physics or Design, a special treatment is required in order to accomplish this problem, since their relation with the real-life socio-economic activities is less evident. Here is the topic we deal with in this paper. In order to solve it we propose a procedure which allows us to define the skills and knowledge to be acquired by engineering students, in relation with the “instrumental ” subjects, with the goal of selecting the most suitable contents of their syllabus, and of scheduleing them in an interdisciplinary way. The final purpose is to ...

Research paper thumbnail of A General Study Of The Mathematical Impact In Technical Curricula

The most of the authors about the topic of University Curricula Design, point out the importance ... more The most of the authors about the topic of University Curricula Design, point out the importance of defining the profesional fields, where the future graduates are going to develop their jobs, in a coherent and up-to-date manner, with the aim of using this information in order to select the contents of the different subjects of the syllabus, which is being tried to be constructed. In the case of "instrumental" disciplines such as Mathematics, Physics or Design, a special treatment is required in order to accomplish this problem, since their relation with the reallife socio-economic activities is less evident. Here is the topic we deal with in this paper. In order to solve it we propose a procedure which allows us to define the skills and knowledge to be acquired by engineering students, in relation with the "instrumental" subjects, with the goal of selecting the most suitable contents of their syllabus, and of scheduleing them in an interdisciplinary way. The fin...

Research paper thumbnail of On the sources of the late integrated Sachs-Wolfe effect

In some scenarios, the peculiar gravitational potential of linear and mildly nonlinear structures... more In some scenarios, the peculiar gravitational potential of linear and mildly nonlinear structures depends on time and, as a result of this dependence, a late integrated Sachs-Wolfe effect appears. Here, an appropriate formalism is used which allows us to improve on the analysis of the spatial scales and locations of the main cosmological inhomogeneities producing this effect. The study is performed in the framework of the currently preferred flat model with cosmological constant, and it is also developed in an open model for comparisons. Results from this analysis are used to discuss the contribution of Great Attractor-like objects, voids, and other structures to the CMB anisotropy. Subject headings: cosmic microwave background—cosmology:theory — large-scale structure of the universe—methods:numericalPACS: 98.70.Vc, 98.65.-r, 98.65.Dx, 95.75.Pq 1 1

Research paper thumbnail of Índices De Un Sistema Generalizado De Control

Localización: Actas: XVI CEDYA Congreso de Ecuaciones Diferenciales y Aplicaciones, VI CMA Congre... more Localización: Actas: XVI CEDYA Congreso de Ecuaciones Diferenciales y Aplicaciones, VI CMA Congreso de Matemática Aplicada, Las Palmas de Gran Canaria, 21-24 septiembre 1999/coord. por Gabriel Winter Althaus, Rafael Alejandro Montenegro Armas, Gustavo ...

Research paper thumbnail of Yukawa effects on the mean motion of an orbiting body

Astrophysics and Space Science, 2016

In today's gravity research there exist few modified gravitational theories which among o... more In today's gravity research there exist few modified gravitational theories which among other things predict the existence of a Yukawa-type correction to the classical gravitational potential. In this paper we study the Yukawa effect on the mean motion if any in a two-body scenario, assuming the influence of the existence of a possible Yukawa correction in the gravitational force of a primary. For that, we derive an equation in order to approximate the mean motion for secondary time rate of change of the orbiting body and its total variation over one revolution, under the influence of the non-Newtonian radial acceleration. Numerical results for Mercury and the companion star of the pulsar PSR 1913 + 16 are calculated. For specific values of the parameters α and λ, as given in the bibliography we have found that there is no corresponding Yukawa effect affecting the mean motion of the planet Mercury. On the other hand it appears that there is a periodic Yukawa effect that affects the mean motion of PSR + 16 whose maximum numerical value occurs when the eccentric anomaly is equal to 180 • .

Research paper thumbnail of On the horizons in a viable vector-tensor theory of gravitation

Astrophysics and Space Science, 2015

A certain vector-tensor (VT) theory of gravitation was tested in previous papers. In the backgrou... more A certain vector-tensor (VT) theory of gravitation was tested in previous papers. In the background universe, the vector field of the theory has a certain energy density, which is appropriate to play the role of vacuum energy (cosmological constant). Moreover, this background and its perturbations may explain the temperature angular power spectrum of the cosmic microwave background (CMB) obtained with WMAP (Wilkinson Map Anisotropy Probe), and other observations, as e.g., the Ia supernova luminosities. The parametrized post-Newtonian limit of the VT theory has been proved to be identical to that of general relativity (GR), and there are no quantum ghosts and classical instabilities. Here, the stationary spherically symmetric solution, in the absence of any matter content, is derived and studied. The metric of this solution is formally identical to that of the Reissner-Nordströmde Sitter solution of GR, but the role of the electrical charge is played by a certain quantity Γ depending on both the vector field and the parameters of the VT theory. The black hole and cosmological horizons are discussed. The radius of the VT black hole horizon deviates with respect to that of the Kottler-Schwarzschildde Sitter radius. Realistic relative deviations depend on Γ and reach maximum values close to 30 per cent. For large enough Γ values, there is no any black hole horizon, but only a cosmological horizon. The radius of this

Research paper thumbnail of On the sources of the late integrated Sachs-Wolfe effect

New Astronomy, 2000

In some scenarios, the peculiar gravitational potential of linear and mildly nonlinear structures... more In some scenarios, the peculiar gravitational potential of linear and mildly nonlinear structures depends on time and, as a result of this dependence, a late integrated Sachs-Wolfe effect appears. Here, an appropriate formalism is used which allows us to improve on the analysis of the spatial scales and locations of the main cosmological inhomogeneities producing this effect. The study is performed in the framework of the currently preferred flat model with cosmological constant, and it is also developed in an open model for comparisons. Results from this analysis are used to discuss the contribution of Great Attractor-like objects, voids, and other structures to the CMB anisotropy. Subject headings: cosmic microwave background-cosmology:theory-large-scale structure of the universe-methods:numerical

Research paper thumbnail of Reachability and observability indices of a discrete-time periodic descriptor system

Applied Mathematics and Computation, 2004

This work introduces the indices of reachability and observability of a discrete-time periodic de... more This work introduces the indices of reachability and observability of a discrete-time periodic descriptor linear system. The reachability and observability indices at time s, s 2 Z, of a periodic collection of nonproper transfer matrices are characterized. Using a special kind of coprime decompositions, the relationship between the indices at consecutive times is analyzed and an algorithm is constructed.

Research paper thumbnail of Some invariants of discrete-time descriptor systems

Applied Mathematics and Computation, 2002

Many papers analyze the role of controllability and observability indices of normal linear system... more Many papers analyze the role of controllability and observability indices of normal linear systems in control theory and their use in the study of structural properties. This work introduces these indices for linear discrete-time descriptor systems. Such indices are studied in two different ways, by means of the state-space approach and using its transfer matrix. A canonical form of the state-space system and a special decomposition of the nonproper transfer matrix are considered in order to discuss the reachability and observability indices.

Research paper thumbnail of Reachability and observability indices of a discrete-time periodic descriptor system

Applied Mathematics and Computation, Jun 4, 2004

This work introduces the indices of reachability and observability of a discrete-time periodic de... more This work introduces the indices of reachability and observability of a discrete-time periodic descriptor linear system. The reachability and observability indices at time s, s 2 Z, of a periodic collection of nonproper transfer matrices are characterized. Using a special kind of coprime decompositions, the relationship between the indices at consecutive times is analyzed and an algorithm is constructed.