Geusa Marques - Academia.edu (original) (raw)
Papers by Geusa Marques
Abstract. Corrections to Newton’s gravitational law inspired by extra dimensional physics and by ... more Abstract. Corrections to Newton’s gravitational law inspired by extra dimensional physics and by the exchange of light and massless elementary particles between the atoms of two macrobodies are considered. These corrections can be described by the potentials of Yukawa-type and by the power-type potentials with different powers. The strongest up to date constraints on the corrections to Newton’s gravitational law are reviewed following from the Eötvos- and Cavendish-type experiments and from the measurements of the Casimir and van der Waals force. We show that the recent measurements of the Casimir force gave the possibility to strengthen the previously known constraints on the constants of hypothetical interactions up to several thousand times in a wide interaction range. Further strengthening is expected in near future that makes Casimir force measurements a prospective test for the predictions of fundamental physical theories. 1.
Efeito de superradiância em buracos negros acústicos na presença de desclinação Geusa de A. Marqu... more Efeito de superradiância em buracos negros acústicos na presença de desclinação Geusa de A. Marques UFCG Análogos acústicos de buracos negros tem sido objeto de investigações, tendo em vista a possibilidade dos mesmos poderem servir como um laboratório para testar os efeitos da geometria e da topologia sobre diferentes sistemas físicos, a exemplo de sistemas atômicos, de sistemas em matéria condensada, em teoria de campos e outras situações. Neste contexto, investigamos a possibilidade de um análogo acústico de um buraco negro, na presença de um defeito chamado desclinação, de alterar a taxa de emissão de superradiância produzida nesse cenário, examinando o efeito da competitividade entre os parâmetros associados à rotação do buraco negro e a deficiência angular da desclinação. Em particular, consideramos o papel da desclinação na amplificação ou atenuação dessa radiação, em função da deficiência de ângulo associada à geometria gerada por este defeito, bem como dos efeitos advindos da presença do buraco negro. A desclinação tem um papel extremamente importante neste cenário, que se realiza através da modificação da quantidade de energia que é retirada do buraco negro acústico, podendo levar a uma situação em que o efeito da deficiência angular sobre a superradiância é compensado por aquele associado à velocidade angular do buraco negro acústico, fornecendo como resultado um coeficiente de reflexão igual à unidade.
The Eleventh Marcel Grossmann Meeting, 2008
![Research paper thumbnail of Comment to: “Corrections to the fine structure constant in the spacetime of a cosmic string from the generalized uncertainty principle” [Phys. Lett. B 632 (2006) 151]](https://attachments.academia-assets.com/110356991/thumbnails/1.jpg)
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Proceedings of the Third Workshop (IWARA07), Apr 1, 2010
In this paper we invstigate the possibility of the acoustic analogue of a phenomenon like superra... more In this paper we invstigate the possibility of the acoustic analogue of a phenomenon like superradiance, that is, the amplification of a sound wave by reflection from the ergo-region of a rotating acoustic black hole in the fluid "draining bathtub" model in the presence of a desclination be amplified or reduced in agreement with the value of the deficit angle.
We study the behaviour of a non-relativistic quantum particle interacting with different potentia... more We study the behaviour of a non-relativistic quantum particle interacting with different potentials, in the background spacetime generated by a cosmic string. We find the energy spectra for the quantum systems under consideration and discuss how they differ from their flat Minkowski spacetime values. PACS numbers: 03.65.Ge, 03.65.Nk, 14.80.Hv I.
Physical Review D, 2010
We consider a scalar field interaction with a cosmic string configuration in a flat 3-brane. The ... more We consider a scalar field interaction with a cosmic string configuration in a flat 3-brane. The origin of this field is given by a compactification mechanism in the context of a 5-dimensional Brans-Dicke theory. We use the Cosmic Microwave Background Radiation constraint to analyse a possibility of optical activity effect in connection with the Brans-Dicke parameter ω and obtain relations between the compactification modes. We show that the dilatons produced by a cosmic string can decay into gauge bosons with masses given by the compactification modes. The Brans-Dicke parameter ω imposes stringent constraints on the mass of the dilaton which lives in the brane and help us to understand the energy scales. In this scenario we estimate the lifetime of the dilaton which decays into light gauge bosons and the dependence of this phenomenon with the Brans-Dicke parameter.
The Tenth Marcel Grossmann Meeting, On Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories - Proceedings of the MG10 Meeting, 2006
We study the behaviour of nonrelativistic quantum particles interacting with different background... more We study the behaviour of nonrelativistic quantum particles interacting with different backgrounds, namely, the generalized Kratzer potential in the spacetime of a cosmic string and the Morse potential in the spacetime of a global monopole. In both cases we find the energy spectra and show how they differ from their free-spacetime values.
International Journal of Modern Physics: Conference Series, 2012
We obtain approximate solutions of the Dirac equation in the gravitational fields of vacuumless d... more We obtain approximate solutions of the Dirac equation in the gravitational fields of vacuumless defects. In all obtained solutions we show the role played by the presence of these defects.
International Journal of Modern Physics: Conference Series, 2012
In this paper we use the Generalized Uncertainty Principle in order to obtain the corrections to ... more In this paper we use the Generalized Uncertainty Principle in order to obtain the corrections to the fine structure constant in (D + 1)-dimensional global monopole spacetime. We also discuss the case D = 3 corresponding to the (3+1)-dimensional global monopole spacetime.
We study the behaviour of a non-relativistic quantum particle interacting with different potentia... more We study the behaviour of a non-relativistic quantum particle interacting with different potentials, in the background spacetime generated by a cosmic string. We find the energy spectra for the quantum systems under consideration and discuss how they differ from their flat Minkowski spacetime values.
Physics Letters A, 2003
A massless spinor particle is considered in the background gravitational field due to a rotating ... more A massless spinor particle is considered in the background gravitational field due to a rotating massive body. In the weak field approximation it is shown that the solution of the massless Dirac equation depend on the angular momentum of the rotating body, which does not affect the curvature in this approximation. This result may be looked upon as a gravitational analogue of the Aharonov-Bohm effect.
Physical Review D, 2002
We consider a hydrogen atom in the background spacetimes generated by an infinitely thin cosmic s... more We consider a hydrogen atom in the background spacetimes generated by an infinitely thin cosmic string and by a point-like global monopole. In both cases, we find the solutions of the corresponding Dirac equations and we determine the energy levels of the atom. We investigate how the geometric and topological features of these spacetimes leads to shifts in the energy levels as compared with the flat Minkowski spacetime.
Modern Physics Letters A, 2004
A massless spinor particle is considered in the background spacetimes generated by a moving mass ... more A massless spinor particle is considered in the background spacetimes generated by a moving mass current and by a spinning cosmic string. In the weak field approximation it is shown that the solution of the Weyl equations depends on the velocity of the source, which does not affect the curvature in this approximation in the case of a moving mass current. In the case of a spinning cosmic string, the solution of the Weyl equations depends on the deficit angle and on the angular momentum of the string. These effects may be viewed as examples of the gravitational analogues of the Aharonov–Bohm effect in electrodynamics.
Modern Physics Letters A, 2001
We study the behaviour of a nonrelativistic quantum particle interacting with the Kratzer molecul... more We study the behaviour of a nonrelativistic quantum particle interacting with the Kratzer molecular potential in the space–time of a global monopole. We find the energy spectrum and derive the scattering amplitude of massive particles propagating in these fields and show how they differ from their free-space values.
Journal of Physics A: Mathematical and General, 2001
In this work we study the Landau levels in the presence of topological defects. We analyze the be... more In this work we study the Landau levels in the presence of topological defects. We analyze the behavior of electrons moving in a magnetic field in the presence of a continuous distribution of disclinations, a magnetic screw dislocation and a dispiration. We focus on the influence of these topological defects on the spectrum of the electron (or hole) in the magnetic field in the framework of the geometric theory of defects in solids of Katanaev-Volovich. The presence of the defect breaks the degeneracy of the Landau levels in different ways depending on the defect. Exact expressions for energies and eigenfunctions are found for all cases. Using Kaluza-Klein theory we solve the Landau level problem for a dispiration and compare the results with the ones obtained in the previous cases.
Journal of Mathematical Physics, 2006
Gravitational Aharonov-Bohm effect due to weak fields. [Journal of Mathematical Physics 47, 07250... more Gravitational Aharonov-Bohm effect due to weak fields. [Journal of Mathematical Physics 47, 072504 (2006)]. Geusa de A. Marques, Sandro G. Fernandes, VB Bezerra. Abstract. We study the behavior of relativistic quantum particles ...
Journal of Mathematical Physics, 2009
ABSTRACT In this paper we obtain a class of static cylindrically symmetric solutions of the Einst... more ABSTRACT In this paper we obtain a class of static cylindrically symmetric solutions of the Einstein–Maxwell field equations in the framework of scalar-tensor theories of gravity. In this context, in which both a Maxwell field and a dilaton field are sources of the stress energy, the solutions were obtained by using the Rainich conditions of general relativity, appropriately modified to take into account the presence of the scalar field.
International Journal of Modern Physics A, 2009
We consider the problem of a relativistic electron in the presence of a Coulomb potential and a m... more We consider the problem of a relativistic electron in the presence of a Coulomb potential and a magnetic field in the background spacetime corresponding to a cosmic string. We find the solution of the corresponding Dirac equation and determine the energy spectrum of the particle.
International Journal of Modern Physics A, 2005
We investigate the quantum scattering of an electron by a topological defect called dispiration, ... more We investigate the quantum scattering of an electron by a topological defect called dispiration, with an externally applied magnetic field along its axis. The Aharonov–Bohm effect for bound states is analyzed and it is demonstrated that the wave function and the energy spectra associated with the particle depend on the features of the dispiration as well as on the magnetic flux. We also calculate Berry's phase associated to the dynamics of electrons in this background.
Abstract. Corrections to Newton’s gravitational law inspired by extra dimensional physics and by ... more Abstract. Corrections to Newton’s gravitational law inspired by extra dimensional physics and by the exchange of light and massless elementary particles between the atoms of two macrobodies are considered. These corrections can be described by the potentials of Yukawa-type and by the power-type potentials with different powers. The strongest up to date constraints on the corrections to Newton’s gravitational law are reviewed following from the Eötvos- and Cavendish-type experiments and from the measurements of the Casimir and van der Waals force. We show that the recent measurements of the Casimir force gave the possibility to strengthen the previously known constraints on the constants of hypothetical interactions up to several thousand times in a wide interaction range. Further strengthening is expected in near future that makes Casimir force measurements a prospective test for the predictions of fundamental physical theories. 1.
Efeito de superradiância em buracos negros acústicos na presença de desclinação Geusa de A. Marqu... more Efeito de superradiância em buracos negros acústicos na presença de desclinação Geusa de A. Marques UFCG Análogos acústicos de buracos negros tem sido objeto de investigações, tendo em vista a possibilidade dos mesmos poderem servir como um laboratório para testar os efeitos da geometria e da topologia sobre diferentes sistemas físicos, a exemplo de sistemas atômicos, de sistemas em matéria condensada, em teoria de campos e outras situações. Neste contexto, investigamos a possibilidade de um análogo acústico de um buraco negro, na presença de um defeito chamado desclinação, de alterar a taxa de emissão de superradiância produzida nesse cenário, examinando o efeito da competitividade entre os parâmetros associados à rotação do buraco negro e a deficiência angular da desclinação. Em particular, consideramos o papel da desclinação na amplificação ou atenuação dessa radiação, em função da deficiência de ângulo associada à geometria gerada por este defeito, bem como dos efeitos advindos da presença do buraco negro. A desclinação tem um papel extremamente importante neste cenário, que se realiza através da modificação da quantidade de energia que é retirada do buraco negro acústico, podendo levar a uma situação em que o efeito da deficiência angular sobre a superradiância é compensado por aquele associado à velocidade angular do buraco negro acústico, fornecendo como resultado um coeficiente de reflexão igual à unidade.
The Eleventh Marcel Grossmann Meeting, 2008
Proceedings of the Third Workshop (IWARA07), Apr 1, 2010
In this paper we invstigate the possibility of the acoustic analogue of a phenomenon like superra... more In this paper we invstigate the possibility of the acoustic analogue of a phenomenon like superradiance, that is, the amplification of a sound wave by reflection from the ergo-region of a rotating acoustic black hole in the fluid "draining bathtub" model in the presence of a desclination be amplified or reduced in agreement with the value of the deficit angle.
We study the behaviour of a non-relativistic quantum particle interacting with different potentia... more We study the behaviour of a non-relativistic quantum particle interacting with different potentials, in the background spacetime generated by a cosmic string. We find the energy spectra for the quantum systems under consideration and discuss how they differ from their flat Minkowski spacetime values. PACS numbers: 03.65.Ge, 03.65.Nk, 14.80.Hv I.
Physical Review D, 2010
We consider a scalar field interaction with a cosmic string configuration in a flat 3-brane. The ... more We consider a scalar field interaction with a cosmic string configuration in a flat 3-brane. The origin of this field is given by a compactification mechanism in the context of a 5-dimensional Brans-Dicke theory. We use the Cosmic Microwave Background Radiation constraint to analyse a possibility of optical activity effect in connection with the Brans-Dicke parameter ω and obtain relations between the compactification modes. We show that the dilatons produced by a cosmic string can decay into gauge bosons with masses given by the compactification modes. The Brans-Dicke parameter ω imposes stringent constraints on the mass of the dilaton which lives in the brane and help us to understand the energy scales. In this scenario we estimate the lifetime of the dilaton which decays into light gauge bosons and the dependence of this phenomenon with the Brans-Dicke parameter.
The Tenth Marcel Grossmann Meeting, On Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories - Proceedings of the MG10 Meeting, 2006
We study the behaviour of nonrelativistic quantum particles interacting with different background... more We study the behaviour of nonrelativistic quantum particles interacting with different backgrounds, namely, the generalized Kratzer potential in the spacetime of a cosmic string and the Morse potential in the spacetime of a global monopole. In both cases we find the energy spectra and show how they differ from their free-spacetime values.
International Journal of Modern Physics: Conference Series, 2012
We obtain approximate solutions of the Dirac equation in the gravitational fields of vacuumless d... more We obtain approximate solutions of the Dirac equation in the gravitational fields of vacuumless defects. In all obtained solutions we show the role played by the presence of these defects.
International Journal of Modern Physics: Conference Series, 2012
In this paper we use the Generalized Uncertainty Principle in order to obtain the corrections to ... more In this paper we use the Generalized Uncertainty Principle in order to obtain the corrections to the fine structure constant in (D + 1)-dimensional global monopole spacetime. We also discuss the case D = 3 corresponding to the (3+1)-dimensional global monopole spacetime.
We study the behaviour of a non-relativistic quantum particle interacting with different potentia... more We study the behaviour of a non-relativistic quantum particle interacting with different potentials, in the background spacetime generated by a cosmic string. We find the energy spectra for the quantum systems under consideration and discuss how they differ from their flat Minkowski spacetime values.
Physics Letters A, 2003
A massless spinor particle is considered in the background gravitational field due to a rotating ... more A massless spinor particle is considered in the background gravitational field due to a rotating massive body. In the weak field approximation it is shown that the solution of the massless Dirac equation depend on the angular momentum of the rotating body, which does not affect the curvature in this approximation. This result may be looked upon as a gravitational analogue of the Aharonov-Bohm effect.
Physical Review D, 2002
We consider a hydrogen atom in the background spacetimes generated by an infinitely thin cosmic s... more We consider a hydrogen atom in the background spacetimes generated by an infinitely thin cosmic string and by a point-like global monopole. In both cases, we find the solutions of the corresponding Dirac equations and we determine the energy levels of the atom. We investigate how the geometric and topological features of these spacetimes leads to shifts in the energy levels as compared with the flat Minkowski spacetime.
Modern Physics Letters A, 2004
A massless spinor particle is considered in the background spacetimes generated by a moving mass ... more A massless spinor particle is considered in the background spacetimes generated by a moving mass current and by a spinning cosmic string. In the weak field approximation it is shown that the solution of the Weyl equations depends on the velocity of the source, which does not affect the curvature in this approximation in the case of a moving mass current. In the case of a spinning cosmic string, the solution of the Weyl equations depends on the deficit angle and on the angular momentum of the string. These effects may be viewed as examples of the gravitational analogues of the Aharonov–Bohm effect in electrodynamics.
Modern Physics Letters A, 2001
We study the behaviour of a nonrelativistic quantum particle interacting with the Kratzer molecul... more We study the behaviour of a nonrelativistic quantum particle interacting with the Kratzer molecular potential in the space–time of a global monopole. We find the energy spectrum and derive the scattering amplitude of massive particles propagating in these fields and show how they differ from their free-space values.
Journal of Physics A: Mathematical and General, 2001
In this work we study the Landau levels in the presence of topological defects. We analyze the be... more In this work we study the Landau levels in the presence of topological defects. We analyze the behavior of electrons moving in a magnetic field in the presence of a continuous distribution of disclinations, a magnetic screw dislocation and a dispiration. We focus on the influence of these topological defects on the spectrum of the electron (or hole) in the magnetic field in the framework of the geometric theory of defects in solids of Katanaev-Volovich. The presence of the defect breaks the degeneracy of the Landau levels in different ways depending on the defect. Exact expressions for energies and eigenfunctions are found for all cases. Using Kaluza-Klein theory we solve the Landau level problem for a dispiration and compare the results with the ones obtained in the previous cases.
Journal of Mathematical Physics, 2006
Gravitational Aharonov-Bohm effect due to weak fields. [Journal of Mathematical Physics 47, 07250... more Gravitational Aharonov-Bohm effect due to weak fields. [Journal of Mathematical Physics 47, 072504 (2006)]. Geusa de A. Marques, Sandro G. Fernandes, VB Bezerra. Abstract. We study the behavior of relativistic quantum particles ...
Journal of Mathematical Physics, 2009
ABSTRACT In this paper we obtain a class of static cylindrically symmetric solutions of the Einst... more ABSTRACT In this paper we obtain a class of static cylindrically symmetric solutions of the Einstein–Maxwell field equations in the framework of scalar-tensor theories of gravity. In this context, in which both a Maxwell field and a dilaton field are sources of the stress energy, the solutions were obtained by using the Rainich conditions of general relativity, appropriately modified to take into account the presence of the scalar field.
International Journal of Modern Physics A, 2009
We consider the problem of a relativistic electron in the presence of a Coulomb potential and a m... more We consider the problem of a relativistic electron in the presence of a Coulomb potential and a magnetic field in the background spacetime corresponding to a cosmic string. We find the solution of the corresponding Dirac equation and determine the energy spectrum of the particle.
International Journal of Modern Physics A, 2005
We investigate the quantum scattering of an electron by a topological defect called dispiration, ... more We investigate the quantum scattering of an electron by a topological defect called dispiration, with an externally applied magnetic field along its axis. The Aharonov–Bohm effect for bound states is analyzed and it is demonstrated that the wave function and the energy spectra associated with the particle depend on the features of the dispiration as well as on the magnetic flux. We also calculate Berry's phase associated to the dynamics of electrons in this background.