Denisa Mihu - Academia.edu (original) (raw)
Papers by Denisa Mihu
arXiv (Cornell University), Apr 26, 2017
In the present paper, we are considering a spatially-flat Friedmann-Robertson-Walker cosmological... more In the present paper, we are considering a spatially-flat Friedmann-Robertson-Walker cosmological model, fueled with stiff matter and dust, treated as non-interacting ideal fluid sources. By solving the corresponding Friedmann equation with a non-zero cosmological constant, we are deriving the scale function and the fundamental cosmological parameters. Within a thermodynamic approach, the general form of the Equation of State is obtained, together with the explicit dependence of the energy density and pressure on temperature.
The purpose of the present work is to obtain new analytical solutions to the relativistically cor... more The purpose of the present work is to obtain new analytical solutions to the relativistically corrected Kompaneets equation describing the photon spectrum in magnetar's magnetosphere. In the assumption of stationarity, the solutions, expressed in terms of Heun Triconfluent functions, can be employed to compute the photons density as a function of the dimensionless frequency.
arXiv (Cornell University), Apr 26, 2017
In the present paper, we are considering a spatially-flat Friedmann-Robertson-Walker cosmological... more In the present paper, we are considering a spatially-flat Friedmann-Robertson-Walker cosmological model, fueled with stiff matter and dust, treated as non-interacting ideal fluid sources. By solving the corresponding Friedmann equation with a non-zero cosmological constant, we are deriving the scale function and the fundamental cosmological parameters. Within a thermodynamic approach, the general form of the Equation of State is obtained, together with the explicit dependence of the energy density and pressure on temperature.
Romanian Journal of Physics, 2018
In the framework of the celebrated perfect-fluid approach to the k = 0 – Friedmann-Robertson-Walk... more In the framework of the celebrated perfect-fluid approach to the k = 0 – Friedmann-Robertson-Walker models, with decoupled mixed sources, the case of radiation and cosmological dust has been investigated. We have obtained the algebraic equations which provide the scale factor and therefore computed the essential cosmological parameters. Finally, the quantum cosmological approach based on this minisuperspace and its heuristic correspondence with the classical regime have been received a particular consideration.
The purpose of the present work is to obtain new analytical solutions to the relativistically cor... more The purpose of the present work is to obtain new analytical solutions to the relativistically corrected Kompaneets equation describing the photon spectrum in magnetar's magnetosphere. In the assumption of stationarity, the solutions, expressed in terms of Heun Triconfluent functions, can be employed to compute the photons density as a function of the dimensionless frequency.
arXiv: General Relativity and Quantum Cosmology, 2016
Within the context of a cosmic space whose energy source is modeled with a perfect fluid, a unifo... more Within the context of a cosmic space whose energy source is modeled with a perfect fluid, a uniform model of Universe based on a standard FRW cosmology containing decoupled mixed matter sources namely stiff matter and cosmic dust together with a positive cosmological constant, has been studied. Within the scenario of a k=0−k=0-k=0− spatially-flat geometry, we analysed the geometrodynamics of the theoretical cosmology. For the model with an added cosmological constant, the main scope was to point out the effects of it on the universe' dynamics. In this last case, the thermodynamics of the model was also considered together with the relation between the cosmological energy density and fluid pressure in terms of the inverse function of the equation of state.
Generalized special solutions to modified Kompaneets equation
AIP Conference Proceedings, 2019
In the stationary regime, configurations of corrected Kompaneets equation have been analyzed with... more In the stationary regime, configurations of corrected Kompaneets equation have been analyzed within a theoretically approach and the spectrum evolution for the scattered photons has been derived. A particular attention has been granted to the impact of the nonlinearity on the spectrum distorsions, mainly to the closed form special solutions expressed in terms of Heun functions. In the nonrelativistic limit, stationary solutions of the Kompaneets equation bring into attention the Heun double confluent functions. On the other side, when various type of corrections come into play, the photon distribution functions are governed by the Heun triconfluent functions. In magnetar’s magnetosphere, where the resonant Compton scattering is more important than the Compton one, the photon number density can be written in terms of Hermite and confluent hypergeometric functions.In the stationary regime, configurations of corrected Kompaneets equation have been analyzed within a theoretically approach and the spectrum evolution for the scattered photons has been derived. A particular attention has been granted to the impact of the nonlinearity on the spectrum distorsions, mainly to the closed form special solutions expressed in terms of Heun functions. In the nonrelativistic limit, stationary solutions of the Kompaneets equation bring into attention the Heun double confluent functions. On the other side, when various type of corrections come into play, the photon distribution functions are governed by the Heun triconfluent functions. In magnetar’s magnetosphere, where the resonant Compton scattering is more important than the Compton one, the photon number density can be written in terms of Hermite and confluent hypergeometric functions.
Tunneling of Relativistic Bosons Induced by Magnetic Fields in the Magnetar's Crust
Chinese Physics Letters, 2015
The present work is devoted to the study of bosons evolving in the frozen magnetar's crust en... more The present work is devoted to the study of bosons evolving in the frozen magnetar's crust endowed with an ultra-strong magnetic field orthogonal to an electric field, both described by periodic functions. We discuss the quantum tunneling process through the one-dimensional potential barrier along Oz. The solutions to the Klein–Gordon equation are expressed in terms of Mathieu's functions which, for computable particle's energy range, are turning from oscillatory to exponentially growing modes along Oz. Within the Jeffreys–Wentzel–Kramers–Brillouin framework, the transmission coefficient is computed for the particle momentum in the middle of the instability range.
AIP Conference Proceedings, 2017
Solutions of Klein-Gordon equation for particles moving in a standing wave configuration bring in... more Solutions of Klein-Gordon equation for particles moving in a standing wave configuration bring into attention an intricate and complicated category of special functions, namely the Mathieu functions. The stability of the solutions governed by the intercorrelation between Mathieu equation' parameters is discussed. For specific intervals of the wave number, the instability regime installs, pointing out the tendency of exponential growth for the oscillatory wave functions, as a consequence of parametric resonance phenomenon. The expression of the wave function allows the computation of the four-dimensional conserved current density components.
arXiv (Cornell University), Apr 26, 2017
In the present paper, we are considering a spatially-flat Friedmann-Robertson-Walker cosmological... more In the present paper, we are considering a spatially-flat Friedmann-Robertson-Walker cosmological model, fueled with stiff matter and dust, treated as non-interacting ideal fluid sources. By solving the corresponding Friedmann equation with a non-zero cosmological constant, we are deriving the scale function and the fundamental cosmological parameters. Within a thermodynamic approach, the general form of the Equation of State is obtained, together with the explicit dependence of the energy density and pressure on temperature.
The purpose of the present work is to obtain new analytical solutions to the relativistically cor... more The purpose of the present work is to obtain new analytical solutions to the relativistically corrected Kompaneets equation describing the photon spectrum in magnetar's magnetosphere. In the assumption of stationarity, the solutions, expressed in terms of Heun Triconfluent functions, can be employed to compute the photons density as a function of the dimensionless frequency.
arXiv (Cornell University), Apr 26, 2017
In the present paper, we are considering a spatially-flat Friedmann-Robertson-Walker cosmological... more In the present paper, we are considering a spatially-flat Friedmann-Robertson-Walker cosmological model, fueled with stiff matter and dust, treated as non-interacting ideal fluid sources. By solving the corresponding Friedmann equation with a non-zero cosmological constant, we are deriving the scale function and the fundamental cosmological parameters. Within a thermodynamic approach, the general form of the Equation of State is obtained, together with the explicit dependence of the energy density and pressure on temperature.
Romanian Journal of Physics, 2018
In the framework of the celebrated perfect-fluid approach to the k = 0 – Friedmann-Robertson-Walk... more In the framework of the celebrated perfect-fluid approach to the k = 0 – Friedmann-Robertson-Walker models, with decoupled mixed sources, the case of radiation and cosmological dust has been investigated. We have obtained the algebraic equations which provide the scale factor and therefore computed the essential cosmological parameters. Finally, the quantum cosmological approach based on this minisuperspace and its heuristic correspondence with the classical regime have been received a particular consideration.
The purpose of the present work is to obtain new analytical solutions to the relativistically cor... more The purpose of the present work is to obtain new analytical solutions to the relativistically corrected Kompaneets equation describing the photon spectrum in magnetar's magnetosphere. In the assumption of stationarity, the solutions, expressed in terms of Heun Triconfluent functions, can be employed to compute the photons density as a function of the dimensionless frequency.
arXiv: General Relativity and Quantum Cosmology, 2016
Within the context of a cosmic space whose energy source is modeled with a perfect fluid, a unifo... more Within the context of a cosmic space whose energy source is modeled with a perfect fluid, a uniform model of Universe based on a standard FRW cosmology containing decoupled mixed matter sources namely stiff matter and cosmic dust together with a positive cosmological constant, has been studied. Within the scenario of a k=0−k=0-k=0− spatially-flat geometry, we analysed the geometrodynamics of the theoretical cosmology. For the model with an added cosmological constant, the main scope was to point out the effects of it on the universe' dynamics. In this last case, the thermodynamics of the model was also considered together with the relation between the cosmological energy density and fluid pressure in terms of the inverse function of the equation of state.
Generalized special solutions to modified Kompaneets equation
AIP Conference Proceedings, 2019
In the stationary regime, configurations of corrected Kompaneets equation have been analyzed with... more In the stationary regime, configurations of corrected Kompaneets equation have been analyzed within a theoretically approach and the spectrum evolution for the scattered photons has been derived. A particular attention has been granted to the impact of the nonlinearity on the spectrum distorsions, mainly to the closed form special solutions expressed in terms of Heun functions. In the nonrelativistic limit, stationary solutions of the Kompaneets equation bring into attention the Heun double confluent functions. On the other side, when various type of corrections come into play, the photon distribution functions are governed by the Heun triconfluent functions. In magnetar’s magnetosphere, where the resonant Compton scattering is more important than the Compton one, the photon number density can be written in terms of Hermite and confluent hypergeometric functions.In the stationary regime, configurations of corrected Kompaneets equation have been analyzed within a theoretically approach and the spectrum evolution for the scattered photons has been derived. A particular attention has been granted to the impact of the nonlinearity on the spectrum distorsions, mainly to the closed form special solutions expressed in terms of Heun functions. In the nonrelativistic limit, stationary solutions of the Kompaneets equation bring into attention the Heun double confluent functions. On the other side, when various type of corrections come into play, the photon distribution functions are governed by the Heun triconfluent functions. In magnetar’s magnetosphere, where the resonant Compton scattering is more important than the Compton one, the photon number density can be written in terms of Hermite and confluent hypergeometric functions.
Tunneling of Relativistic Bosons Induced by Magnetic Fields in the Magnetar's Crust
Chinese Physics Letters, 2015
The present work is devoted to the study of bosons evolving in the frozen magnetar's crust en... more The present work is devoted to the study of bosons evolving in the frozen magnetar's crust endowed with an ultra-strong magnetic field orthogonal to an electric field, both described by periodic functions. We discuss the quantum tunneling process through the one-dimensional potential barrier along Oz. The solutions to the Klein–Gordon equation are expressed in terms of Mathieu's functions which, for computable particle's energy range, are turning from oscillatory to exponentially growing modes along Oz. Within the Jeffreys–Wentzel–Kramers–Brillouin framework, the transmission coefficient is computed for the particle momentum in the middle of the instability range.
AIP Conference Proceedings, 2017
Solutions of Klein-Gordon equation for particles moving in a standing wave configuration bring in... more Solutions of Klein-Gordon equation for particles moving in a standing wave configuration bring into attention an intricate and complicated category of special functions, namely the Mathieu functions. The stability of the solutions governed by the intercorrelation between Mathieu equation' parameters is discussed. For specific intervals of the wave number, the instability regime installs, pointing out the tendency of exponential growth for the oscillatory wave functions, as a consequence of parametric resonance phenomenon. The expression of the wave function allows the computation of the four-dimensional conserved current density components.