Dark energy is an elusive concept, which has been introduced two decades ago in order to make the... more Dark energy is an elusive concept, which has been introduced two decades ago in order to make the acceleration of the universe a comprehensible phenomenon. However, the nature of this energy is far from being understood, both from a fundamental as well as an observational way. In this work we study cosmological consequences of the existence of particles (which we called "ewkons" in a previous work) which are quasi distinguishable, obey unorthodox statistics, and have an equation of state similar to many existent dark energy candidates (including negative relation between pressure and energy density). We find an effective scalar field description of this ewkon fluid, and obtain cosmological solutions for the dark energy dominated epoch. This can be considered as a one-parameter class of dark energy models.
All in-text references underlined in blue are linked to publications on ResearchGate, letting you... more All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.
We derive an equation for the current of particles in energy space; particles are subject to a me... more We derive an equation for the current of particles in energy space; particles are subject to a mean field effective potential that may represent quantum effects. From the assumption that noninteracting particles imply a free diffusion coefficient in energy space we derive Maxwell-Boltzmann, Fermi-Dirac and Bose-Einstein statistics. Other new statistics are associated to a free diffusion coefficient; their thermodynamic properties are analyzed using the grand partition function. A negative relation between pressure and energy density for low temperatures can be derived, suggesting a possible connection with cosmological dark energy models.
Boletin De La Asociacion Argentina De Astronomia La Plata Argentina, 2003
Se estudian las violaciones al Principio de Equivalencia en Teorías con Dilatón de Cuerdas. En es... more Se estudian las violaciones al Principio de Equivalencia en Teorías con Dilatón de Cuerdas. En estos modelos, algunas de las constantes fundamentales dependen del espacio y del tiempo. Se muestra que los experimentos de caída libre no tienen aún precisión como para poner límites a los parámetros de la teoría.
According to recent reports there is an excess correlation and an apparent regularity in the gala... more According to recent reports there is an excess correlation and an apparent regularity in the galaxy one-dimensional polar distribution with a characteristic scale of 128 h −1 Mpc. This aparent spatial periodicity can be naturally explained by a time oscillation of the gravitational constant G. On the other hand, periodic growth features of bivalve and coral fossiles appear to show a periodic component in the time dependence of the number of days per year. In this letter we show that a time oscillating gravitational constant with similar period and amplitude can explain such a feature.
Estudiamos el rango de validez del esquema de inflacion estocastica sin imponer a priori la aprox... more Estudiamos el rango de validez del esquema de inflacion estocastica sin imponer a priori la aproximacion de rodadura lenta. Encontramos las condiciones generales que se satisfacen para que sea aplicable este formalismo e ilustramos los resultados con dos ejemplos con solucion analitica.
The authors show that the measured parameters of the K0 - K-0 system impose strong constraints on... more The authors show that the measured parameters of the K0 - K-0 system impose strong constraints on the time variation of the s and d quark masses, and on the scale parameter of QCD Λ. These results provide information about the cosmological evolution of dilaton fields in superstring theories.
The perfect fluid in the context of a covariant variable speed of light (VSL) theory proposed by ... more The perfect fluid in the context of a covariant variable speed of light (VSL) theory proposed by J. Magueijo is studied. On the one hand the modified first law of thermodynamics together with a recipe to obtain equations of state are obtained. On the other hand the Newtonian limit is performed to obtain the non- relativistic hydrostatic equilibrium equation for the theory. The results obtained are used to determine the time variation of the radius of Mercury induced by the variability of the speed of light (c). Using a bound for the actual change of that radius and combining it with an upper limit for the variation of the fine structure constant, a bound on the time variation of c is set.
Aims. On the basis of the theoretical model proposed by Bekenstein for α's variation, we analyze ... more Aims. On the basis of the theoretical model proposed by Bekenstein for α's variation, we analyze the equations that describe the energy exchange between matter and both the electromagnetic and the scalar fields. Methods. We determine how the energy flow of the material is modified by the presence of a scalar field. We estimate the total magnetic energy of matter from the "sum rules techniques". We compare the results with data obtained from the thermal evolution of the Earth and other planets. Results. We obtain stringent upper limits to the variations in α that are comparable with those obtained from atomic clock frequency variations. Conclusions. Our constraints imply that the fundamental length scale of Bekenstein's theory " B " cannot be larger than Planck's length " P ".
Aims. On the basis of the theoretical model proposed by Bekenstein for α’s variation, we analyze ... more Aims. On the basis of the theoretical model proposed by Bekenstein for α’s variation, we analyze the equations that describe the energy exchange between matter and both the electromagnetic and the scalar fields. Methods. We determine how the energy flow of the material is modified by the presence of a scalar field. We estimate the total magnetic energy of matter from the “sum rules techniques”. We compare the results with data obtained from the thermal evolution of the Earth and other planets. Results. We obtain stringent upper limits to the variations in α that are comparable with those obtained from atomic clock frequency variations. Conclusions. Our constraints imply that the fundamental length scale of Bekenstein’s theory “`B” cannot be larger than Planck’s length “`P”.
We study violations of the weak equivalence principle in the context of string dilaton theories. ... more We study violations of the weak equivalence principle in the context of string dilaton theories. In these models some fundamental constants become spaceas well as time-dependent. We show that although universality of free fall (UFF) experiments set bounds on parameters that govern the cosmological evolution of the scalar fields, these are strongly relaxed when considering the space dependent behavior of the scalar field. We also analyze the Oklo bound on the variation of the fine structure constant. Conversely, including the space-dependent solution of the dilaton field, does not affect the restrictions on the free parameters of the model. Finally, consequences on the relevance of experiments on UFF are reanalyzed. PACS NUMBERS: 4.50+h, 4.80 Cc, 98.80Cq
Aims. On the basis the theoretical model proposed by Bekenstein for α’s variation, we analyze the... more Aims. On the basis the theoretical model proposed by Bekenstein for α’s variation, we analyze the equations that describe the energy exchange between matter and both the electromagnetic and the scalar fields. Methods. We determine how the energy flow of the material is modified by the presence of a scalar field. We estimate the total magnetic energy of matter from the “sum rules techniques”. We compare the results with data obtained from the thermal evolution of the Earth and other planets. Results. We obtain stringent upper limits to the variations in α that are comparable with those obtained from atomic clock frequency variations. Conclusions. Our constraints imply that the fundamental length scale of Bekenstein’s theory “lB” cannot be larger than Planck’s length “lP”.
We test the prediction of the time variation of the fine structure constant in the string dilaton... more We test the prediction of the time variation of the fine structure constant in the string dilaton model proposed by Damour and Polyakov. First, we analize the dependence of all available observational and experimental data with the fine structure constant variation. Furthermore, we obtain the prediction of the time variation of the fine structure constant including the renormalization group correction. Finally, we use the data set to perform a statistical analyisis. This analysis enables us to determine that the the dilaton model is in agreement with most of the data. Finally, constraints on the free parameters of this model are obtained.
Within the framework of stochastic inflationary cosmology we derive steady-state distributions P_... more Within the framework of stochastic inflationary cosmology we derive steady-state distributions P_c(V) of domains in comoving coordinates, under the assumption of slow-rolling and for two specific choices of the coarse-grained inflaton potential $V(\Phi)$. We model the process as a Starobinsky-like equation in V-space plus a time-independent source term P_w(V) which carries (phenomenologically) quantum-mechanical information drawn from either of two known solutions of the Wheeler-De Witt equation: Hartle-Hawking's and Vilenkin's wave functions. The presence of the source term leads to the existence of nontrivial steady-state distributions P^w_c(V). The relative efficiencies of both mechanisms at different scales are compared for the proposed potentials.
ABSTRACT Within the framework of the stochastic treatment of the inflationary model of the Univer... more ABSTRACT Within the framework of the stochastic treatment of the inflationary model of the Universe with a slow rolling scalar field, the authors study stationary solutions of the Starobinsky diffusion equation for the transition probabilities.
Page 1. PHYSICAL REVIEW D VOLUME 44, NUMBER 10 15 NOVEMBER 1991 Time variation of fundamental con... more Page 1. PHYSICAL REVIEW D VOLUME 44, NUMBER 10 15 NOVEMBER 1991 Time variation of fundamental constants. II. Quark masses as time-dependent parameters P. Sisterna* and H. Vucetich* Departamento de Fssica ...
Dark energy is an elusive concept, which has been introduced two decades ago in order to make the... more Dark energy is an elusive concept, which has been introduced two decades ago in order to make the acceleration of the universe a comprehensible phenomenon. However, the nature of this energy is far from being understood, both from a fundamental as well as an observational way. In this work we study cosmological consequences of the existence of particles (which we called "ewkons" in a previous work) which are quasi distinguishable, obey unorthodox statistics, and have an equation of state similar to many existent dark energy candidates (including negative relation between pressure and energy density). We find an effective scalar field description of this ewkon fluid, and obtain cosmological solutions for the dark energy dominated epoch. This can be considered as a one-parameter class of dark energy models.
All in-text references underlined in blue are linked to publications on ResearchGate, letting you... more All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.
We derive an equation for the current of particles in energy space; particles are subject to a me... more We derive an equation for the current of particles in energy space; particles are subject to a mean field effective potential that may represent quantum effects. From the assumption that noninteracting particles imply a free diffusion coefficient in energy space we derive Maxwell-Boltzmann, Fermi-Dirac and Bose-Einstein statistics. Other new statistics are associated to a free diffusion coefficient; their thermodynamic properties are analyzed using the grand partition function. A negative relation between pressure and energy density for low temperatures can be derived, suggesting a possible connection with cosmological dark energy models.
Boletin De La Asociacion Argentina De Astronomia La Plata Argentina, 2003
Se estudian las violaciones al Principio de Equivalencia en Teorías con Dilatón de Cuerdas. En es... more Se estudian las violaciones al Principio de Equivalencia en Teorías con Dilatón de Cuerdas. En estos modelos, algunas de las constantes fundamentales dependen del espacio y del tiempo. Se muestra que los experimentos de caída libre no tienen aún precisión como para poner límites a los parámetros de la teoría.
According to recent reports there is an excess correlation and an apparent regularity in the gala... more According to recent reports there is an excess correlation and an apparent regularity in the galaxy one-dimensional polar distribution with a characteristic scale of 128 h −1 Mpc. This aparent spatial periodicity can be naturally explained by a time oscillation of the gravitational constant G. On the other hand, periodic growth features of bivalve and coral fossiles appear to show a periodic component in the time dependence of the number of days per year. In this letter we show that a time oscillating gravitational constant with similar period and amplitude can explain such a feature.
Estudiamos el rango de validez del esquema de inflacion estocastica sin imponer a priori la aprox... more Estudiamos el rango de validez del esquema de inflacion estocastica sin imponer a priori la aproximacion de rodadura lenta. Encontramos las condiciones generales que se satisfacen para que sea aplicable este formalismo e ilustramos los resultados con dos ejemplos con solucion analitica.
The authors show that the measured parameters of the K0 - K-0 system impose strong constraints on... more The authors show that the measured parameters of the K0 - K-0 system impose strong constraints on the time variation of the s and d quark masses, and on the scale parameter of QCD Λ. These results provide information about the cosmological evolution of dilaton fields in superstring theories.
The perfect fluid in the context of a covariant variable speed of light (VSL) theory proposed by ... more The perfect fluid in the context of a covariant variable speed of light (VSL) theory proposed by J. Magueijo is studied. On the one hand the modified first law of thermodynamics together with a recipe to obtain equations of state are obtained. On the other hand the Newtonian limit is performed to obtain the non- relativistic hydrostatic equilibrium equation for the theory. The results obtained are used to determine the time variation of the radius of Mercury induced by the variability of the speed of light (c). Using a bound for the actual change of that radius and combining it with an upper limit for the variation of the fine structure constant, a bound on the time variation of c is set.
Aims. On the basis of the theoretical model proposed by Bekenstein for α's variation, we analyze ... more Aims. On the basis of the theoretical model proposed by Bekenstein for α's variation, we analyze the equations that describe the energy exchange between matter and both the electromagnetic and the scalar fields. Methods. We determine how the energy flow of the material is modified by the presence of a scalar field. We estimate the total magnetic energy of matter from the "sum rules techniques". We compare the results with data obtained from the thermal evolution of the Earth and other planets. Results. We obtain stringent upper limits to the variations in α that are comparable with those obtained from atomic clock frequency variations. Conclusions. Our constraints imply that the fundamental length scale of Bekenstein's theory " B " cannot be larger than Planck's length " P ".
Aims. On the basis of the theoretical model proposed by Bekenstein for α’s variation, we analyze ... more Aims. On the basis of the theoretical model proposed by Bekenstein for α’s variation, we analyze the equations that describe the energy exchange between matter and both the electromagnetic and the scalar fields. Methods. We determine how the energy flow of the material is modified by the presence of a scalar field. We estimate the total magnetic energy of matter from the “sum rules techniques”. We compare the results with data obtained from the thermal evolution of the Earth and other planets. Results. We obtain stringent upper limits to the variations in α that are comparable with those obtained from atomic clock frequency variations. Conclusions. Our constraints imply that the fundamental length scale of Bekenstein’s theory “`B” cannot be larger than Planck’s length “`P”.
We study violations of the weak equivalence principle in the context of string dilaton theories. ... more We study violations of the weak equivalence principle in the context of string dilaton theories. In these models some fundamental constants become spaceas well as time-dependent. We show that although universality of free fall (UFF) experiments set bounds on parameters that govern the cosmological evolution of the scalar fields, these are strongly relaxed when considering the space dependent behavior of the scalar field. We also analyze the Oklo bound on the variation of the fine structure constant. Conversely, including the space-dependent solution of the dilaton field, does not affect the restrictions on the free parameters of the model. Finally, consequences on the relevance of experiments on UFF are reanalyzed. PACS NUMBERS: 4.50+h, 4.80 Cc, 98.80Cq
Aims. On the basis the theoretical model proposed by Bekenstein for α’s variation, we analyze the... more Aims. On the basis the theoretical model proposed by Bekenstein for α’s variation, we analyze the equations that describe the energy exchange between matter and both the electromagnetic and the scalar fields. Methods. We determine how the energy flow of the material is modified by the presence of a scalar field. We estimate the total magnetic energy of matter from the “sum rules techniques”. We compare the results with data obtained from the thermal evolution of the Earth and other planets. Results. We obtain stringent upper limits to the variations in α that are comparable with those obtained from atomic clock frequency variations. Conclusions. Our constraints imply that the fundamental length scale of Bekenstein’s theory “lB” cannot be larger than Planck’s length “lP”.
We test the prediction of the time variation of the fine structure constant in the string dilaton... more We test the prediction of the time variation of the fine structure constant in the string dilaton model proposed by Damour and Polyakov. First, we analize the dependence of all available observational and experimental data with the fine structure constant variation. Furthermore, we obtain the prediction of the time variation of the fine structure constant including the renormalization group correction. Finally, we use the data set to perform a statistical analyisis. This analysis enables us to determine that the the dilaton model is in agreement with most of the data. Finally, constraints on the free parameters of this model are obtained.
Within the framework of stochastic inflationary cosmology we derive steady-state distributions P_... more Within the framework of stochastic inflationary cosmology we derive steady-state distributions P_c(V) of domains in comoving coordinates, under the assumption of slow-rolling and for two specific choices of the coarse-grained inflaton potential $V(\Phi)$. We model the process as a Starobinsky-like equation in V-space plus a time-independent source term P_w(V) which carries (phenomenologically) quantum-mechanical information drawn from either of two known solutions of the Wheeler-De Witt equation: Hartle-Hawking's and Vilenkin's wave functions. The presence of the source term leads to the existence of nontrivial steady-state distributions P^w_c(V). The relative efficiencies of both mechanisms at different scales are compared for the proposed potentials.
ABSTRACT Within the framework of the stochastic treatment of the inflationary model of the Univer... more ABSTRACT Within the framework of the stochastic treatment of the inflationary model of the Universe with a slow rolling scalar field, the authors study stationary solutions of the Starobinsky diffusion equation for the transition probabilities.
Page 1. PHYSICAL REVIEW D VOLUME 44, NUMBER 10 15 NOVEMBER 1991 Time variation of fundamental con... more Page 1. PHYSICAL REVIEW D VOLUME 44, NUMBER 10 15 NOVEMBER 1991 Time variation of fundamental constants. II. Quark masses as time-dependent parameters P. Sisterna* and H. Vucetich* Departamento de Fssica ...
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