Marcony Cunha | Universidade Estadual do Ceara (original) (raw)

Papers by Marcony Cunha

The European Physical Journal C

We examine the interaction between massless scalar fields and the gravitational field generated b... more We examine the interaction between massless scalar fields and the gravitational field generated by a black hole solution that was recently obtained in the consistent well-defined 4-dimensional Einstein–Gauss–Bonnet gravity with a cosmological constant. In order to do this, we calculate quasibound state frequencies of scalar fields for the spherically symmetric black hole in the consistent 4-dimensional Einstein–Gauss–Bonnet–de Sitter and Anti-de Sitter theories. The expression for the quasibound states is obtained by using the polynomial condition associated to the Heun functions, and their values are overdamped. We also demonstrate the stability of the systems.

Annals of Physics

In this paper, we obtain a static black string solution to a bilocal gravitational source in 3+1 ... more In this paper, we obtain a static black string solution to a bilocal gravitational source in 3+1 dimensions. The solution is regular at the origin and tends asymptotically to the ordinary static uncharged black string solution of General Relativity. It can present an event horizon and allows an internal horizon depending on the value of the mass density. A mass remnant associated with a vanishing Hawking temperature is also found. In order to stabilize the solution, a perfect cosmological fluid with state parameter ω > −1 should be present throughout space. However, energy conditions do not exclude an exotic substance nearby the black string. Finally, we present the stationary counterpart of the solution and analyze the behavior of the horizons according to the mass and angular momentum of the spinning object.

In this paper we obtain black hole solutions from an action in 2+1 dimensions with bilocal Ricci ... more In this paper we obtain black hole solutions from an action in 2+1 dimensions with bilocal Ricci scalar and negative cosmological constant. The solutions found are regular (i. e., free of singularities) and present one or two horizons depending on the value of the fundamental length. We analyze the energy conditions of the matter source and compute thermodynamic quantities such as Hawking temperature, entropy, heat capacity, and free energy. We show that for small values of the horizon radius the Hawking temperature is negatively divergent, but a finite size remnant can be defined where THT_HTH crosses zero. This phase transition is not present in the static and uncharged BTZ black hole. Finally, we consider massless and massive particles in motion around these regular black hole solutions and show that there exist closed paths with stable circular orbits.

We use the exact analytical solution of the radial part of the Klein-Gordon equation describing a... more We use the exact analytical solution of the radial part of the Klein-Gordon equation describing a charged massive scalar field in the electrically charged Garfinkle-Horowitz-Strominger dilaton black hole spacetime, given in terms of the confluent Heun functions, to study the physical phenomena related to resonant frequencies associated to this field, and also to examine some aspects related to its Hawking radiation. The special case of a Schwarzschild spacetime is also considered.

In the present paper, we investigate how the phantom class of dark energy, presumably responsible... more In the present paper, we investigate how the phantom class of dark energy, presumably responsible for a super-accelerated cosmic expansion and here described by the state parameter ω=-5/3, determines the wave function of the Universe. This is done by analytically solving the Wheeler-DeWitt (WdW) equation in the cosmology of Friedmann-Robertson-Walker with an ambiguity term arising from the ordering of the conjugate operators associated with the scale factor a. Its solutions depend on an additional parameter q related to that ordering and show that the Universe presents maximal probability to come into existence with a well-defined size for q = 0. The amplitude of the wavefunction is higher the higher is the phantom energy content so an initial singularity of the type a = 0 is very unlikely. In this semi-classical approach, we also study how the scale factor evolves with time via the Hamilton-Jacobi equation assuming a flat Universe. We show that the ultimate big rip singularity emer...

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.

International Journal of Modern Physics D, 2020

In this work, the wave functions associated to the quantum relativistic universe, which is descri... more In this work, the wave functions associated to the quantum relativistic universe, which is described by the Wheeler–DeWitt equation, are obtained. Taking into account different kinds of energy density, namely, matter, radiation, vacuum, dark energy and quintessence, we discuss some aspects of the quantum dynamics. In all these cases, the wave functions of the quantum relativistic universe are given in terms of the triconfluent Heun functions. We investigate the expansion of the universe using these solutions and found that the asymptotic behavior for the scale factor is [Formula: see text] for whatever the form of energy density is. On the other hand, we analyze the behavior at early stages of the universe and found that [Formula: see text]. We also calculate and analyze the transmission coefficient through the effective potential barrier.

arXiv: General Relativity and Quantum Cosmology, 2019

In this work the wave functions associated to the quantum relativistic universe, which is describ... more In this work the wave functions associated to the quantum relativistic universe, which is described by the Wheeler-DeWitt equation, are obtained. Taking into account all forms of energy density, namely, matter, radiation, vacuum, dark energy, and quintessence, we discuss some aspects of the quantum dynamics. In all these cases, the wave functions of the quantum relativistic universe are given in terms of the triconfluent Heun functions. We investigate the expansion of the universe using these solutions and found that the asymptotic behavior for the scale factor is a(t)simmboxeta(t) \sim \mbox{e}^{t}a(t)simmboxet for whatever the form of energy density is. On the other hand, we analyze the behavior at early stages of the universe and found that a(t)simt1/2a(t) \sim t^{1/2}a(t)simt1/2. We also calculate and analyze the transmission coefficient through the effective potential barrier.

Bolas de bilhar que se chocam, neutrons atirados contra nucleos atomicos em um reator nuclear, o ... more Bolas de bilhar que se chocam, neutrons atirados contra nucleos atomicos em um reator nuclear, o impacto de um meteoro na superficie terrestre, todos esses eventos sao exemplos de colisoes, um assunto nem sempre bem compreendido pelos estudantes das escolas secundarias. Este trabalho apresenta uma atividade experimental para alunos do ensino secundario com o objetivo de consolidar o estudo de colisoes e nortear a acao pedagogica dos professores. Atualmente, a maioria dos estudantes possui um smartphone, cuja utilizacao na sala de aula para fins de comunicacao e redes sociais, tem sido compreensivelmente restringida nas escolas brasileiras. Entretanto podemos utilizar este instrumento como um recurso didatico com varias vantagens, principalmente em escolas que sofrem com a falta de laboratorios de ciencias. Esses aparelhos possuem diversos sensores e aplicativos que podem facilitar a aprendizagem e o ensino de Fisica, embora nao tenham sido fabricados com este proposito. A possibilid...

Nanomaterials Applications for Environmental Matrices, 2019

Abstract Numerous studies have shown that nanomaterials can effectively remove various pollutants... more Abstract Numerous studies have shown that nanomaterials can effectively remove various pollutants from water and have been successfully applied for water and wastewater treatment. This chapter provides a revision on water treatment devices based on metal oxide nanomaterials. The use of nanomaterials (nanorods, nanoparticles, nanotubes, nanoplates, nanowire, nanosheets, branched structures, and hybrid nanoarchitectures) for the treatment of water has increased due to the size of nanomaterials, which influences the properties of these materials. Size and morphology induce the reactivity of nanomaterials and change the quantum confinement and the optical and the electronic behaviors. For instance, nanostructures of metal oxide are used as electrochemical supercapacitors, sensors, magnetic controlling systems, adsorbents, and catalysts to remove organic compounds from water by adsorption. Another important application is related to the use of these materials in membrane separation processes in water treatment with nanoparticles of iron oxide, silica, alumina, silver, zeolites, carbon nanotubes, and titanate oxide enhanced membranes, as well as for improved functionalities of membranes integrated with nanoparticles for water treatment.

Physics Letters B, 2020

In this letter, we discuss the Wheeler-DeWitt equation with an ordering parameter in the Friedman... more In this letter, we discuss the Wheeler-DeWitt equation with an ordering parameter in the Friedmann-Robertson-Walker universe. The solutions when the universe was very small and at the end of the expansion are obtained in terms of Bessel and Heun functions, respectively. We also obtain a boundary condition which should be satisfied by the ordering parameter, namely, p ≤ 1. We investigate the minimum value of the scale factor with respect to the maximum value of the probability density.

Physics of the Dark Universe, 2020

We investigate the quantum evolution of the universe in the presence of two types of dark energie... more We investigate the quantum evolution of the universe in the presence of two types of dark energies. First, we consider the phantom class (ω < −1) which would be responsible for a superaccelerated cosmic expansion, and then we apply the procedure to an ordinary Λ > 0 vacuum (ω = −1). This is done by analytically solving the Wheeler-DeWitt equation with ordering term (WdW) in the cosmology of Friedmann-Robertson-Walker. In this paper, we find exact solutions in the scale factor a and the ordering parameter q. For q = 1 it is shown that the universe has a high probability of evolving from a big bang singularity. On the other hand, for q = 0 the solution indicates that an initial singularity is unlikely. Instead, the universe has maximal probability of starting with a finite well-defined size which we compute explicitly at primordial times. We also study the time evolution of the scale factor by means of the Hamilton-Jacobi equation and show that an ultimate big rip singularity emerges explicitly from our solutions. The phantom scenario thus predicts a dramatic end in which the universe would reach an infinite scale factor in a finite cosmological time as pointed by Caldwell et al. in a classical setup [1]. Finally, we solve the WdW equation with ordinary constant dark energy and show that in this case the universe does not rip apart in a finite era.

The European Physical Journal Plus, 2020

In this manuscript we compute corrections to the global Casimir effect at zero and finite tempera... more In this manuscript we compute corrections to the global Casimir effect at zero and finite temperature due to Rainbow's Gravity (parametrized by ξ). For this we use the solutions for the scalar field with mass m in the deformed Schwarzschild background and the corresponding quantized energies of the system, which represent the stationary states of the field and yield the stable part of the quantum vacuum energy. The analysis is made here by considering the limit for which the source mass, M , approaches zero, in order to verify the effects on the global Casimir effect in mini black holes near to the Planck scale, ω P. We find a singular behavior for the regularized vacuum energy at zero temperature and for all the corresponding thermodynamic quantities when m 2 = ω 2 P /ξ, what can be seen as the limit of validity of the model. Furthermore, we show that the remnant Casimir tension over the event horizon in the limit M → 0 is finite for any temperature and all the space of parameters. In fact we show that the remnant tension receives no corrections from Rainbow's Gravity. This points to the fact that such a behavior may be an universal property of this kind of system.

Journal of Mathematical Physics, 2019

We obtain the wave functions associated with the quantum Newtonian universe with a cosmological c... more We obtain the wave functions associated with the quantum Newtonian universe with a cosmological constant which is described by the Schrödinger equation and discuss some aspects of its dynamics for all forms of energy density, namely, matter, radiation, vacuum, dark energy, and quintessence. These wave functions of the quantum Newtonian universe are obtained in terms of Heun's functions and the respective energy levels are shown. We use these solutions to investigate the expansion of the universe and found that the asymptotic behavior for the scale factor is R ∼ e t for whatever the form of energy density is. We also analyze the behavior of the universe at early stages.

Journal of Physics and Chemistry of Solids, 2015

Abstract In this work, we study the effects related to the creation of electron/hole pairs via ap... more Abstract In this work, we study the effects related to the creation of electron/hole pairs via application of an external electric field that acts on a pristine trans-polyacetylene molecular chain at zero-temperature. This phenomenon is termed Schwinger–Landau–Zener (SLZ) effect and arises when a physical system, which can even be the vacuum, is under the action of a strong, static and spatially homogeneous electric field. Initially, we investigate how the electrical conductivity of the polyacetylene changes with the applied field, by considering the carriers production as well as the variation of the interband gap according to certain ab initio models. Next, we analyse the competition between the SLZ effect and another one associated with the incidence of an uniform electric field on one-dimensional crystals – the Bloch oscillations. We evaluate the conditions in which these latter can be destroyed by the particles created through the same field that induces them, and verify the possibility of occurrence of the Bloch oscillations inside the trans-polyacetylene with frequencies equal to or higher than the terahertz scale.

Revista do Professor de Física, 2017

Como os aviões conseguem voar? Este trabalho tem como objetivo geral fornecer aos estudantes, fun... more Como os aviões conseguem voar? Este trabalho tem como objetivo geral fornecer aos estudantes, fundamentação teórica e orientação prática, a fim de lhes dar as condições de aprendizagem para responder esta pergunta, através de simulações do aplicativo Wind Tunnel no estudo de dinâmica dos fluidos para analisar o voo de um avião. Para alcançar este objetivo são propostas quatro atividades usando os aplicativos e materiais de fácil aquisição. A primeira consiste em utilizar os perfis aerodinâmicos, já existentes no aplicativo, dando aos estudantes a oportunidade de explorar os conteúdos expostos pelo professor em sala de aula. Na segunda atividade, os estudantes, usando o aplicativo, simulariam um perfil aerodinâmico que resulte a melhor relação entre a sustentação e o arrasto. Seguindo a segunda atividade, eles construirão em 3D, o protótipo da asa de avião usando, preferencialmente, materiais de baixo custo, como papel, cola, arame, usando como modelo, o perfil escolhido e criado na ...

Revista do Professor de Física, 2017

O presente trabalho procurou contribuir para o estudo do lançamento de projéteis em sala de aula ... more O presente trabalho procurou contribuir para o estudo do lançamento de projéteis em sala de aula para alunos do primeiro ano do Ensino Médio, utilizando aplicativos de videoanálises. Para alcançar os objetivos é proposto, como exemplo do lançamento de um projétil, o lançamento de um foguete construído com materiais de baixo custo. Seu movimento foi filmado e a partir dos dados e gráficos gerados pelos aplicativos Vídeo Physics e o Graphical Analysis, ele foi analisado. Para orientar o trabalho dos alunos em sala de aula, propõe-se que o professor peça-lhes que investiguem sobre a tangente do ângulo de inclinação da base, o tempo de subida e descida do foguete, seu alcance, sua velocidade e posição em cada eixo, além de suas funções. Propõe-se também que os alunos trabalhem em regime de colaboração, em que uma equipe grava um vídeo e envia para outras equipes analisarem e redigirem relatórios apresentando os gráficos, as tabelas e as considerações feitas em equipe.

International Journal of Modern Physics D, 2019

We use the exact analytical solution of the radial part of the Klein–Gordon equation describing a... more We use the exact analytical solution of the radial part of the Klein–Gordon equation describing a charged massive scalar field in the electrically charged Garfinkle–Horowitz–Strominger dilaton black hole spacetime, given in terms of the confluent Heun functions, to study the physical phenomena related to resonant frequencies associated with this field, and also to examine some aspects related to its Hawking radiation. The special case of a Schwarzschild spacetime is also considered.

Journal of Cosmology and Astroparticle Physics, 2018

In this paper we compute corrections to the global Casimir effect of a massive scalar field aroun... more In this paper we compute corrections to the global Casimir effect of a massive scalar field around a static mini black hole at zero and finite temperature due to the Rainbow's Gravity. For this we use the analytical solutions for the scalar field with mass m in the deformed Schwarzschild background. The analysis is made by considering the limit for which the source mass, M , approaches zero, in order to verify the effects of quantum gravity on the global Casimir effect in the final moments of the evaporating black hole. Initially, we compute the corrected stable part of the Casimir energy at zero temperature. At finite temperature we compute the corrected vacuum thermodynamic quantities of the system: free energy, internal energy, entropy and heat capacity, including the high temperature limits. We find a singular behavior for the Casimir energy at zero temperature as well as for all the corresponding thermodynamic quantities when m 2 = ω 2 P /ξ and this can be seen as the limit of validity of the model. However the conclusions about the thermodynamic stability of the vacuum are basically the same as in the uncorrected case. We also find that the remnant Casimir tension over the event horizon is finite for any temperature and all parameter values. More importantly, we show that the tension receives no corrections from Rainbow's Gravity for zero or finite temperature. This points to the fact that such behavior may be an universal property of the black hole evaporation. As a byproduct we correct the result of a recently published article about the subject, analysed in the general relativity context, and find a positive remnant Casimir tension in the high temperature limit, showing that this latter cannot "erase" the zero temperature remnant Casimir tension, as concluded in that work. In fact the effect of high temperatures will be to double it.

The European Physical Journal C

We examine the interaction between massless scalar fields and the gravitational field generated b... more We examine the interaction between massless scalar fields and the gravitational field generated by a black hole solution that was recently obtained in the consistent well-defined 4-dimensional Einstein–Gauss–Bonnet gravity with a cosmological constant. In order to do this, we calculate quasibound state frequencies of scalar fields for the spherically symmetric black hole in the consistent 4-dimensional Einstein–Gauss–Bonnet–de Sitter and Anti-de Sitter theories. The expression for the quasibound states is obtained by using the polynomial condition associated to the Heun functions, and their values are overdamped. We also demonstrate the stability of the systems.

Annals of Physics

In this paper, we obtain a static black string solution to a bilocal gravitational source in 3+1 ... more In this paper, we obtain a static black string solution to a bilocal gravitational source in 3+1 dimensions. The solution is regular at the origin and tends asymptotically to the ordinary static uncharged black string solution of General Relativity. It can present an event horizon and allows an internal horizon depending on the value of the mass density. A mass remnant associated with a vanishing Hawking temperature is also found. In order to stabilize the solution, a perfect cosmological fluid with state parameter ω > −1 should be present throughout space. However, energy conditions do not exclude an exotic substance nearby the black string. Finally, we present the stationary counterpart of the solution and analyze the behavior of the horizons according to the mass and angular momentum of the spinning object.

In this paper we obtain black hole solutions from an action in 2+1 dimensions with bilocal Ricci ... more In this paper we obtain black hole solutions from an action in 2+1 dimensions with bilocal Ricci scalar and negative cosmological constant. The solutions found are regular (i. e., free of singularities) and present one or two horizons depending on the value of the fundamental length. We analyze the energy conditions of the matter source and compute thermodynamic quantities such as Hawking temperature, entropy, heat capacity, and free energy. We show that for small values of the horizon radius the Hawking temperature is negatively divergent, but a finite size remnant can be defined where THT_HTH crosses zero. This phase transition is not present in the static and uncharged BTZ black hole. Finally, we consider massless and massive particles in motion around these regular black hole solutions and show that there exist closed paths with stable circular orbits.

We use the exact analytical solution of the radial part of the Klein-Gordon equation describing a... more We use the exact analytical solution of the radial part of the Klein-Gordon equation describing a charged massive scalar field in the electrically charged Garfinkle-Horowitz-Strominger dilaton black hole spacetime, given in terms of the confluent Heun functions, to study the physical phenomena related to resonant frequencies associated to this field, and also to examine some aspects related to its Hawking radiation. The special case of a Schwarzschild spacetime is also considered.

In the present paper, we investigate how the phantom class of dark energy, presumably responsible... more In the present paper, we investigate how the phantom class of dark energy, presumably responsible for a super-accelerated cosmic expansion and here described by the state parameter ω=-5/3, determines the wave function of the Universe. This is done by analytically solving the Wheeler-DeWitt (WdW) equation in the cosmology of Friedmann-Robertson-Walker with an ambiguity term arising from the ordering of the conjugate operators associated with the scale factor a. Its solutions depend on an additional parameter q related to that ordering and show that the Universe presents maximal probability to come into existence with a well-defined size for q = 0. The amplitude of the wavefunction is higher the higher is the phantom energy content so an initial singularity of the type a = 0 is very unlikely. In this semi-classical approach, we also study how the scale factor evolves with time via the Hamilton-Jacobi equation assuming a flat Universe. We show that the ultimate big rip singularity emer...

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.

International Journal of Modern Physics D, 2020

In this work, the wave functions associated to the quantum relativistic universe, which is descri... more In this work, the wave functions associated to the quantum relativistic universe, which is described by the Wheeler–DeWitt equation, are obtained. Taking into account different kinds of energy density, namely, matter, radiation, vacuum, dark energy and quintessence, we discuss some aspects of the quantum dynamics. In all these cases, the wave functions of the quantum relativistic universe are given in terms of the triconfluent Heun functions. We investigate the expansion of the universe using these solutions and found that the asymptotic behavior for the scale factor is [Formula: see text] for whatever the form of energy density is. On the other hand, we analyze the behavior at early stages of the universe and found that [Formula: see text]. We also calculate and analyze the transmission coefficient through the effective potential barrier.

arXiv: General Relativity and Quantum Cosmology, 2019

In this work the wave functions associated to the quantum relativistic universe, which is describ... more In this work the wave functions associated to the quantum relativistic universe, which is described by the Wheeler-DeWitt equation, are obtained. Taking into account all forms of energy density, namely, matter, radiation, vacuum, dark energy, and quintessence, we discuss some aspects of the quantum dynamics. In all these cases, the wave functions of the quantum relativistic universe are given in terms of the triconfluent Heun functions. We investigate the expansion of the universe using these solutions and found that the asymptotic behavior for the scale factor is a(t)simmboxeta(t) \sim \mbox{e}^{t}a(t)simmboxet for whatever the form of energy density is. On the other hand, we analyze the behavior at early stages of the universe and found that a(t)simt1/2a(t) \sim t^{1/2}a(t)simt1/2. We also calculate and analyze the transmission coefficient through the effective potential barrier.

Bolas de bilhar que se chocam, neutrons atirados contra nucleos atomicos em um reator nuclear, o ... more Bolas de bilhar que se chocam, neutrons atirados contra nucleos atomicos em um reator nuclear, o impacto de um meteoro na superficie terrestre, todos esses eventos sao exemplos de colisoes, um assunto nem sempre bem compreendido pelos estudantes das escolas secundarias. Este trabalho apresenta uma atividade experimental para alunos do ensino secundario com o objetivo de consolidar o estudo de colisoes e nortear a acao pedagogica dos professores. Atualmente, a maioria dos estudantes possui um smartphone, cuja utilizacao na sala de aula para fins de comunicacao e redes sociais, tem sido compreensivelmente restringida nas escolas brasileiras. Entretanto podemos utilizar este instrumento como um recurso didatico com varias vantagens, principalmente em escolas que sofrem com a falta de laboratorios de ciencias. Esses aparelhos possuem diversos sensores e aplicativos que podem facilitar a aprendizagem e o ensino de Fisica, embora nao tenham sido fabricados com este proposito. A possibilid...

Nanomaterials Applications for Environmental Matrices, 2019

Abstract Numerous studies have shown that nanomaterials can effectively remove various pollutants... more Abstract Numerous studies have shown that nanomaterials can effectively remove various pollutants from water and have been successfully applied for water and wastewater treatment. This chapter provides a revision on water treatment devices based on metal oxide nanomaterials. The use of nanomaterials (nanorods, nanoparticles, nanotubes, nanoplates, nanowire, nanosheets, branched structures, and hybrid nanoarchitectures) for the treatment of water has increased due to the size of nanomaterials, which influences the properties of these materials. Size and morphology induce the reactivity of nanomaterials and change the quantum confinement and the optical and the electronic behaviors. For instance, nanostructures of metal oxide are used as electrochemical supercapacitors, sensors, magnetic controlling systems, adsorbents, and catalysts to remove organic compounds from water by adsorption. Another important application is related to the use of these materials in membrane separation processes in water treatment with nanoparticles of iron oxide, silica, alumina, silver, zeolites, carbon nanotubes, and titanate oxide enhanced membranes, as well as for improved functionalities of membranes integrated with nanoparticles for water treatment.

Physics Letters B, 2020

In this letter, we discuss the Wheeler-DeWitt equation with an ordering parameter in the Friedman... more In this letter, we discuss the Wheeler-DeWitt equation with an ordering parameter in the Friedmann-Robertson-Walker universe. The solutions when the universe was very small and at the end of the expansion are obtained in terms of Bessel and Heun functions, respectively. We also obtain a boundary condition which should be satisfied by the ordering parameter, namely, p ≤ 1. We investigate the minimum value of the scale factor with respect to the maximum value of the probability density.

Physics of the Dark Universe, 2020

We investigate the quantum evolution of the universe in the presence of two types of dark energie... more We investigate the quantum evolution of the universe in the presence of two types of dark energies. First, we consider the phantom class (ω < −1) which would be responsible for a superaccelerated cosmic expansion, and then we apply the procedure to an ordinary Λ > 0 vacuum (ω = −1). This is done by analytically solving the Wheeler-DeWitt equation with ordering term (WdW) in the cosmology of Friedmann-Robertson-Walker. In this paper, we find exact solutions in the scale factor a and the ordering parameter q. For q = 1 it is shown that the universe has a high probability of evolving from a big bang singularity. On the other hand, for q = 0 the solution indicates that an initial singularity is unlikely. Instead, the universe has maximal probability of starting with a finite well-defined size which we compute explicitly at primordial times. We also study the time evolution of the scale factor by means of the Hamilton-Jacobi equation and show that an ultimate big rip singularity emerges explicitly from our solutions. The phantom scenario thus predicts a dramatic end in which the universe would reach an infinite scale factor in a finite cosmological time as pointed by Caldwell et al. in a classical setup [1]. Finally, we solve the WdW equation with ordinary constant dark energy and show that in this case the universe does not rip apart in a finite era.

The European Physical Journal Plus, 2020

In this manuscript we compute corrections to the global Casimir effect at zero and finite tempera... more In this manuscript we compute corrections to the global Casimir effect at zero and finite temperature due to Rainbow's Gravity (parametrized by ξ). For this we use the solutions for the scalar field with mass m in the deformed Schwarzschild background and the corresponding quantized energies of the system, which represent the stationary states of the field and yield the stable part of the quantum vacuum energy. The analysis is made here by considering the limit for which the source mass, M , approaches zero, in order to verify the effects on the global Casimir effect in mini black holes near to the Planck scale, ω P. We find a singular behavior for the regularized vacuum energy at zero temperature and for all the corresponding thermodynamic quantities when m 2 = ω 2 P /ξ, what can be seen as the limit of validity of the model. Furthermore, we show that the remnant Casimir tension over the event horizon in the limit M → 0 is finite for any temperature and all the space of parameters. In fact we show that the remnant tension receives no corrections from Rainbow's Gravity. This points to the fact that such a behavior may be an universal property of this kind of system.

Journal of Mathematical Physics, 2019

We obtain the wave functions associated with the quantum Newtonian universe with a cosmological c... more We obtain the wave functions associated with the quantum Newtonian universe with a cosmological constant which is described by the Schrödinger equation and discuss some aspects of its dynamics for all forms of energy density, namely, matter, radiation, vacuum, dark energy, and quintessence. These wave functions of the quantum Newtonian universe are obtained in terms of Heun's functions and the respective energy levels are shown. We use these solutions to investigate the expansion of the universe and found that the asymptotic behavior for the scale factor is R ∼ e t for whatever the form of energy density is. We also analyze the behavior of the universe at early stages.

Journal of Physics and Chemistry of Solids, 2015

Abstract In this work, we study the effects related to the creation of electron/hole pairs via ap... more Abstract In this work, we study the effects related to the creation of electron/hole pairs via application of an external electric field that acts on a pristine trans-polyacetylene molecular chain at zero-temperature. This phenomenon is termed Schwinger–Landau–Zener (SLZ) effect and arises when a physical system, which can even be the vacuum, is under the action of a strong, static and spatially homogeneous electric field. Initially, we investigate how the electrical conductivity of the polyacetylene changes with the applied field, by considering the carriers production as well as the variation of the interband gap according to certain ab initio models. Next, we analyse the competition between the SLZ effect and another one associated with the incidence of an uniform electric field on one-dimensional crystals – the Bloch oscillations. We evaluate the conditions in which these latter can be destroyed by the particles created through the same field that induces them, and verify the possibility of occurrence of the Bloch oscillations inside the trans-polyacetylene with frequencies equal to or higher than the terahertz scale.

Revista do Professor de Física, 2017

Como os aviões conseguem voar? Este trabalho tem como objetivo geral fornecer aos estudantes, fun... more Como os aviões conseguem voar? Este trabalho tem como objetivo geral fornecer aos estudantes, fundamentação teórica e orientação prática, a fim de lhes dar as condições de aprendizagem para responder esta pergunta, através de simulações do aplicativo Wind Tunnel no estudo de dinâmica dos fluidos para analisar o voo de um avião. Para alcançar este objetivo são propostas quatro atividades usando os aplicativos e materiais de fácil aquisição. A primeira consiste em utilizar os perfis aerodinâmicos, já existentes no aplicativo, dando aos estudantes a oportunidade de explorar os conteúdos expostos pelo professor em sala de aula. Na segunda atividade, os estudantes, usando o aplicativo, simulariam um perfil aerodinâmico que resulte a melhor relação entre a sustentação e o arrasto. Seguindo a segunda atividade, eles construirão em 3D, o protótipo da asa de avião usando, preferencialmente, materiais de baixo custo, como papel, cola, arame, usando como modelo, o perfil escolhido e criado na ...

Revista do Professor de Física, 2017

O presente trabalho procurou contribuir para o estudo do lançamento de projéteis em sala de aula ... more O presente trabalho procurou contribuir para o estudo do lançamento de projéteis em sala de aula para alunos do primeiro ano do Ensino Médio, utilizando aplicativos de videoanálises. Para alcançar os objetivos é proposto, como exemplo do lançamento de um projétil, o lançamento de um foguete construído com materiais de baixo custo. Seu movimento foi filmado e a partir dos dados e gráficos gerados pelos aplicativos Vídeo Physics e o Graphical Analysis, ele foi analisado. Para orientar o trabalho dos alunos em sala de aula, propõe-se que o professor peça-lhes que investiguem sobre a tangente do ângulo de inclinação da base, o tempo de subida e descida do foguete, seu alcance, sua velocidade e posição em cada eixo, além de suas funções. Propõe-se também que os alunos trabalhem em regime de colaboração, em que uma equipe grava um vídeo e envia para outras equipes analisarem e redigirem relatórios apresentando os gráficos, as tabelas e as considerações feitas em equipe.

International Journal of Modern Physics D, 2019

We use the exact analytical solution of the radial part of the Klein–Gordon equation describing a... more We use the exact analytical solution of the radial part of the Klein–Gordon equation describing a charged massive scalar field in the electrically charged Garfinkle–Horowitz–Strominger dilaton black hole spacetime, given in terms of the confluent Heun functions, to study the physical phenomena related to resonant frequencies associated with this field, and also to examine some aspects related to its Hawking radiation. The special case of a Schwarzschild spacetime is also considered.

Journal of Cosmology and Astroparticle Physics, 2018

In this paper we compute corrections to the global Casimir effect of a massive scalar field aroun... more In this paper we compute corrections to the global Casimir effect of a massive scalar field around a static mini black hole at zero and finite temperature due to the Rainbow's Gravity. For this we use the analytical solutions for the scalar field with mass m in the deformed Schwarzschild background. The analysis is made by considering the limit for which the source mass, M , approaches zero, in order to verify the effects of quantum gravity on the global Casimir effect in the final moments of the evaporating black hole. Initially, we compute the corrected stable part of the Casimir energy at zero temperature. At finite temperature we compute the corrected vacuum thermodynamic quantities of the system: free energy, internal energy, entropy and heat capacity, including the high temperature limits. We find a singular behavior for the Casimir energy at zero temperature as well as for all the corresponding thermodynamic quantities when m 2 = ω 2 P /ξ and this can be seen as the limit of validity of the model. However the conclusions about the thermodynamic stability of the vacuum are basically the same as in the uncorrected case. We also find that the remnant Casimir tension over the event horizon is finite for any temperature and all parameter values. More importantly, we show that the tension receives no corrections from Rainbow's Gravity for zero or finite temperature. This points to the fact that such behavior may be an universal property of the black hole evaporation. As a byproduct we correct the result of a recently published article about the subject, analysed in the general relativity context, and find a positive remnant Casimir tension in the high temperature limit, showing that this latter cannot "erase" the zero temperature remnant Casimir tension, as concluded in that work. In fact the effect of high temperatures will be to double it.