Sergio Costa Ulhoa
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Research Subjects
Sergio Costa Ulhoa has a total of 68 co-authors. Here are the top co-authors by number of shared publications:
- Jose Wadih Maluf
Universidade de Brasília
39 shared publications - Fernando Lessa Carneiro
Departamento de Física, Universidade Federal do Norte do Tocantins, 77824-838 Araguaína, TO, Brazil
38 shared publications - Ronni Geraldo Gomes Amorim
University of Brasilia
31 shared publications - Alesandro F. Santos
Universidade Federal de Mato Grosso
30 shared publications - José Francisco Da Rocha-Neto
Instituto de Física Universidade de Brasília 70910-900 Brasília DF Brazil
24 shared publications - Faqir C. Khanna
Department of Physics and Astronomy, University of Victoria, Victoria, Canada
14 shared publications
Latest Publications
- 26 October 2026
- Published by World Scientific Pub Co Pte Ltd in Modern Physics Letters A
On the gravitational-wave energy density in the teleparallel equivalent of general relativity: Application to LIGO–Virgo–KAGRA events
In this paper, we compute the gravitational energy density of a linearized gravitational wave in the teleparallel equivalent of general relativity. For a plane wave in the transverse-traceless gauge we obtain the closed and exact expression [Formula: see text], and evaluate it on model polarizations [Formula: see text] and [Formula: see text] generated with source parameters consistent with 10 LIGO–Virgo–KAGRA events spanning binary black holes, binary neutron stars and neutron-star-black-hole systems. Being a total derivative in the retarded time, the density is not positive definite and the energy it assigns to a region reduces to a flux across its boundary. As a local diagnostic, however, its morphology correlates with the nature of the source, contrasting the slow, growing oscillation of neutron-star systems with the compact profile that marks a black-hole merger. We argue that this quantity, built directly from the strain, may offer a template-independent diagnostic of gravitational-wave events.
- 26 October 2026
- Published by World Scientific Pub Co Pte Ltd in Modern Physics Letters A
On the gravitational-wave energy density in the teleparallel equivalent of general relativity: Application to LIGO–Virgo–KAGRA events
In this paper, we compute the gravitational energy density of a linearized gravitational wave in the teleparallel equivalent of general relativity. For a plane wave in the transverse-traceless gauge we obtain the closed and exact expression [Formula: see text], and evaluate it on model polarizations [Formula: see text] and [Formula: see text] generated with source parameters consistent with 10 LIGO–Virgo–KAGRA events spanning binary black holes, binary neutron stars and neutron-star-black-hole systems. Being a total derivative in the retarded time, the density is not positive definite and the energy it assigns to a region reduces to a flux across its boundary. As a local diagnostic, however, its morphology correlates with the nature of the source, contrasting the slow, growing oscillation of neutron-star systems with the compact profile that marks a black-hole merger. We argue that this quantity, built directly from the strain, may offer a template-independent diagnostic of gravitational-wave events.
- Open Access
- 31 July 2026
- Published by MDPI AG in Preprints.org
On the Gravitational-Wave Energy Density in the Teleparallel Equivalent of General Relativity: Application to LIGO–Virgo–KAGRA Events
We compute the gravitational energy density of a linearized gravitational wave in the teleparallel equivalent of general relativity. For a plane wave in the transverse-traceless gauge we obtain the closed and exact expression \( \varepsilon(u)=\tfrac{1}{32\pi}\,\tfrac{d^{2}}{du^{2}}(h_{+}^{2}+h_{\times}^{2}) \), and evaluate it on model polarizations h₊(t) and h×(t) generated with source parameters consistent with ten LIGO-Virgo-KAGRA events spanning binary black holes, binary neutron stars and neutron-star-black-hole systems. Being a total derivative in the retarded time, the density is not positive definite and the energy it assigns to a region reduces to a flux across its boundary; as a local diagnostic, however, its morphology correlates with the nature of the source, contrasting the slow, growing oscillation of neutron-star systems with the compact profile that marks a black-hole merger. We argue that this quantity, built directly from the strain, may offer a template-independent diagnostic of gravitational-wave events.- 31 July 2026
- Published by MDPI AG in Preprints.org
Open AccessOn the Gravitational-Wave Energy Density in the Teleparallel Equivalent of General Relativity: Application to LIGO–Virgo–KAGRA Events
We compute the gravitational energy density of a linearized gravitational wave in the teleparallel equivalent of general relativity. For a plane wave in the transverse-traceless gauge we obtain the closed and exact expression \( \varepsilon(u)=\tfrac{1}{32\pi}\,\tfrac{d^{2}}{du^{2}}(h_{+}^{2}+h_{\times}^{2}) \), and evaluate it on model polarizations h₊(t) and h×(t) generated with source parameters consistent with ten LIGO-Virgo-KAGRA events spanning binary black holes, binary neutron stars and neutron-star-black-hole systems. Being a total derivative in the retarded time, the density is not positive definite and the energy it assigns to a region reduces to a flux across its boundary; as a local diagnostic, however, its morphology correlates with the nature of the source, contrasting the slow, growing oscillation of neutron-star systems with the compact profile that marks a black-hole merger. We argue that this quantity, built directly from the strain, may offer a template-independent diagnostic of gravitational-wave events. - Open Access
- 29 July 2026
- Published by Springer Nature in The European Physical Journal Plus
- Vol. 141 (7) , 870
On a Gödel-like solution in non-relativistic gravity
The article deals with Gödel-like solutions in the context of Galilean gravity, a geometric formulation of non-relativistic gravitation defined on a five-dimensional Galilean manifold. Within this framework, non-relativistic matter fields admit a covariant description, while the physical Newtonian dynamics is recovered through an immersion into the usual $$3+1$$ spacetime. By adopting a Gödel-like metric ansatz and coupling the gravitational field to a Galilean fluid derived from a variational principle, we obtain a system of highly nonlinear and coupled field equations. This system is solved exactly: the matter sector is determined algebraically by the field equations, and the metric functions are obtained in closed form, $$D(x)=\cosh (mx)$$ and $$H(x)=\sinh (mx)$$ . The resulting configuration describes a rotating non-relativistic universe supported by the constant potential term of the fluid Lagrangian and satisfies the identity $$D^{2}(x)-H^{2}(x)=1$$ throughout the entire spatial domain. As a consequence, the associated Killing vector remains spacelike everywhere and no closed timelike curves arise.- 29 July 2026
- Published by Springer Nature in The European Physical Journal Plus
- Vol. 141 (7) , 870
Open AccessOn a Gödel-like solution in non-relativistic gravity
The article deals with Gödel-like solutions in the context of Galilean gravity, a geometric formulation of non-relativistic gravitation defined on a five-dimensional Galilean manifold. Within this framework, non-relativistic matter fields admit a covariant description, while the physical Newtonian dynamics is recovered through an immersion into the usual $$3+1$$ spacetime. By adopting a Gödel-like metric ansatz and coupling the gravitational field to a Galilean fluid derived from a variational principle, we obtain a system of highly nonlinear and coupled field equations. This system is solved exactly: the matter sector is determined algebraically by the field equations, and the metric functions are obtained in closed form, $$D(x)=\cosh (mx)$$ and $$H(x)=\sinh (mx)$$ . The resulting configuration describes a rotating non-relativistic universe supported by the constant potential term of the fluid Lagrangian and satisfies the identity $$D^{2}(x)-H^{2}(x)=1$$ throughout the entire spatial domain. As a consequence, the associated Killing vector remains spacelike everywhere and no closed timelike curves arise. - 9 July 2026
- Published by World Scientific Pub Co Pte Ltd in International Journal of Geometric Methods in Modern Physics
On the gravitational energy of axial perturbations in regular black holes
This paper deals with the gravitational energy associated with axial perturbations of regular black holes. We review the stability of the geometry under odd-parity perturbations and the corresponding quasinormal modes, previously obtained for this class of spacetimes. The perturbative functions describing the metric fluctuations are reconstructed from the master equation. To evaluate the energy content of these perturbations, we employ the Teleparallel Equivalent of General Relativity (TEGR), which provides a well-defined expression for gravitational energy. The gravitational energy is computed up to second order in the perturbation parameter and expressed in terms of the quasinormal mode functions. Our results establish a direct connection between the dynamical response of regular black holes and the energy carried by their gravitational perturbations.
- 9 July 2026
- Published by World Scientific Pub Co Pte Ltd in International Journal of Geometric Methods in Modern Physics
On the gravitational energy of axial perturbations in regular black holes
This paper deals with the gravitational energy associated with axial perturbations of regular black holes. We review the stability of the geometry under odd-parity perturbations and the corresponding quasinormal modes, previously obtained for this class of spacetimes. The perturbative functions describing the metric fluctuations are reconstructed from the master equation. To evaluate the energy content of these perturbations, we employ the Teleparallel Equivalent of General Relativity (TEGR), which provides a well-defined expression for gravitational energy. The gravitational energy is computed up to second order in the perturbation parameter and expressed in terms of the quasinormal mode functions. Our results establish a direct connection between the dynamical response of regular black holes and the energy carried by their gravitational perturbations.
- 18 May 2026
- Published by IOP Publishing in Physica Scripta
- Vol. 101 (20) , 205001
The role of gravitational energy flux in cosmic acceleration
The article deals with the role of gravitational radiation energy in the large-scale dynamics of the Universe. Motivated by the observed accelerated expansion, we investigate whether gravitational energy, treated as a well-defined physical quantity within the teleparallel equivalent of general relativity, contributes to cosmological acceleration through its associated energy flux. Using radiative space-times described by the Bondi–Sachs framework, we analyze the total gravitational energy and the corresponding energy flux evaluated in asymptotic regions. Particular emphasis is placed on the cumulative character of gravitational radiation over long time scales and on the fact that gravitational energy in this formulation is not positively definite. The present analysis provides a consistent theoretical basis for assessing the relevance of gravitational radiation energy and its flux in cosmological contexts.
- 18 May 2026
- Published by IOP Publishing in Physica Scripta
- Vol. 101 (20) , 205001
The role of gravitational energy flux in cosmic acceleration
The article deals with the role of gravitational radiation energy in the large-scale dynamics of the Universe. Motivated by the observed accelerated expansion, we investigate whether gravitational energy, treated as a well-defined physical quantity within the teleparallel equivalent of general relativity, contributes to cosmological acceleration through its associated energy flux. Using radiative space-times described by the Bondi–Sachs framework, we analyze the total gravitational energy and the corresponding energy flux evaluated in asymptotic regions. Particular emphasis is placed on the cumulative character of gravitational radiation over long time scales and on the fact that gravitational energy in this formulation is not positively definite. The present analysis provides a consistent theoretical basis for assessing the relevance of gravitational radiation energy and its flux in cosmological contexts.
- 25 April 2026
- Published by World Scientific Pub Co Pte Ltd in International Journal of Modern Physics D
- Vol. 35 (08)
On nonrelativistic isotropic and homogeneous universe
This paper deals with a nonrelativistic cosmological model based on Galilean covariance, formulated within a five-dimensional Galilean manifold. Within this framework, we construct an isotropic and homogeneous metric analogous to the Friedmann–Robertson–Walker metric but without a universal speed limit. Two distinct solutions of the Einstein-like field equations are obtained: (i) a vacuum configuration [ ] yielding an exponential–quadratic scale factor, and (ii) a dust-dominated universe [ ] described by a noninteracting nonrelativistic fluid. Upon dimensional reduction to 3[ ]1 spacetime through a specific embedding, the model naturally develops anisotropy in the scale factor and density, consistent with the near-zero spatial curvature inferred from Planck data. In the case of vanishing spatial curvature, the framework reproduces Milne’s Newtonian cosmology because this condition leads to a vanishing pressure. This provides an independent nonrelativistic setting for cosmological dynamics within Galilean covariance.
- 25 April 2026
- Published by World Scientific Pub Co Pte Ltd in International Journal of Modern Physics D
- Vol. 35 (08)
On nonrelativistic isotropic and homogeneous universe
This paper deals with a nonrelativistic cosmological model based on Galilean covariance, formulated within a five-dimensional Galilean manifold. Within this framework, we construct an isotropic and homogeneous metric analogous to the Friedmann–Robertson–Walker metric but without a universal speed limit. Two distinct solutions of the Einstein-like field equations are obtained: (i) a vacuum configuration [ ] yielding an exponential–quadratic scale factor, and (ii) a dust-dominated universe [ ] described by a noninteracting nonrelativistic fluid. Upon dimensional reduction to 3[ ]1 spacetime through a specific embedding, the model naturally develops anisotropy in the scale factor and density, consistent with the near-zero spatial curvature inferred from Planck data. In the case of vanishing spatial curvature, the framework reproduces Milne’s Newtonian cosmology because this condition leads to a vanishing pressure. This provides an independent nonrelativistic setting for cosmological dynamics within Galilean covariance.
- 23 April 2026
- Published by IOP Publishing in Europhysics Letters
- Vol. 154 (4) , 49002
On the gravitational angular momentum of axial perturbations of a regular black hole
This Letter deals with the gravitational angular momentum carried by axial (odd-parity) perturbations of the Bardeen regular black hole within the teleparallel equivalent of general relativity (TEGR). Using the Hamiltonian definition of conserved quantities in TEGR, we derive a closed expression for the perturbative angular momentum $\delta J$ in terms of the axial perturbation function $h_0(r,t)$. The result exhibits a sharp multipolar selection rule: $\delta J$ vanishes for odd values of the multipole index $\ell$, while even-$\ell$ modes yield a nonzero contribution. The radial and temporal behavior of $\delta J$ is illustrated using the known axial quasinormal modes of the Bardeen spacetime.- 23 April 2026
- Published by IOP Publishing in Europhysics Letters
- Vol. 154 (4) , 49002
On the gravitational angular momentum of axial perturbations of a regular black hole
This Letter deals with the gravitational angular momentum carried by axial (odd-parity) perturbations of the Bardeen regular black hole within the teleparallel equivalent of general relativity (TEGR). Using the Hamiltonian definition of conserved quantities in TEGR, we derive a closed expression for the perturbative angular momentum $\delta J$ in terms of the axial perturbation function $h_0(r,t)$. The result exhibits a sharp multipolar selection rule: $\delta J$ vanishes for odd values of the multipole index $\ell$, while even-$\ell$ modes yield a nonzero contribution. The radial and temporal behavior of $\delta J$ is illustrated using the known axial quasinormal modes of the Bardeen spacetime.- 8 April 2026
- Published by IOP Publishing in Classical and Quantum Gravity
- Vol. 43 (7) , 07LT01
Blueshift of light rays induced by gravitational wave memory effect
The article deals with photon propagation in pp-wave spacetimes in the strong gravitational-wave regime and its consequences for redshift measurements. We show that null geodesics crossing a localized pp-wave pulse exhibit an energy memory effect, producing a finite asymptotic shift in the photon frequency measured by static observers. This path-dependent contribution acts directly on the redshift observable and may help account for divergent interpretations of supernova redshift data in the presence of intervening gravitational radiation.
- 8 April 2026
- Published by IOP Publishing in Classical and Quantum Gravity
- Vol. 43 (7) , 07LT01
Blueshift of light rays induced by gravitational wave memory effect
The article deals with photon propagation in pp-wave spacetimes in the strong gravitational-wave regime and its consequences for redshift measurements. We show that null geodesics crossing a localized pp-wave pulse exhibit an energy memory effect, producing a finite asymptotic shift in the photon frequency measured by static observers. This path-dependent contribution acts directly on the redshift observable and may help account for divergent interpretations of supernova redshift data in the presence of intervening gravitational radiation.
- Open Access
On a Gödel-like Solution in Non-Relativistic Gravity
The article deals with Gödel-like solutions in the context of Galilean gravity, a geometric formulation of non-relativistic gravitation defined on a five-dimensional Galilean manifold. Within this framework, non-relativistic matter fields admit a covariant description, while the physical Newtonian dynamics is recovered through an immersion into the usual $3+1$ spacetime. By adopting a Gödel-like metric ansatz and coupling the gravitational field to a Galilean fluid derived from a variational principle, we obtain a system of highly nonlinear and coupled field equations. Exact solutions are constructed by fixing the matter sector consistently with the field equations. The resulting configurations describe rotating non-relativistic universes and satisfy $D(x)>H(x)$ throughout the entire spatial domain. As a consequence, the associated Killing vector remains spacelike everywhere and no closed timelike curves arise.Open AccessOn a Gödel-like Solution in Non-Relativistic Gravity
The article deals with Gödel-like solutions in the context of Galilean gravity, a geometric formulation of non-relativistic gravitation defined on a five-dimensional Galilean manifold. Within this framework, non-relativistic matter fields admit a covariant description, while the physical Newtonian dynamics is recovered through an immersion into the usual $3+1$ spacetime. By adopting a Gödel-like metric ansatz and coupling the gravitational field to a Galilean fluid derived from a variational principle, we obtain a system of highly nonlinear and coupled field equations. Exact solutions are constructed by fixing the matter sector consistently with the field equations. The resulting configurations describe rotating non-relativistic universes and satisfy $D(x)>H(x)$ throughout the entire spatial domain. As a consequence, the associated Killing vector remains spacelike everywhere and no closed timelike curves arise. - Open Access
On the Gravitational Energy of Axial Perturbations in Regular Black Holes
The article deals with the gravitational energy associated with axial perturbations of regular black holes. We review the stability of the geometry under odd-parity perturbations and the corresponding quasinormal modes, previously obtained for this class of spacetimes. The perturbative functions describing the metric fluctuations are reconstructed from the master equation. To evaluate the energy content of these perturbations, we employ the Teleparallel Equivalent of General Relativity (TEGR), which provides a well-defined expression for gravitational energy. The gravitational energy is computed up to second order in the perturbation parameter and expressed in terms of the quasinormal mode functions. Our results establish a direct connection between the dynamical response of regular black holes and the energy carried by their gravitational perturbations.
Open AccessOn the Gravitational Energy of Axial Perturbations in Regular Black Holes
The article deals with the gravitational energy associated with axial perturbations of regular black holes. We review the stability of the geometry under odd-parity perturbations and the corresponding quasinormal modes, previously obtained for this class of spacetimes. The perturbative functions describing the metric fluctuations are reconstructed from the master equation. To evaluate the energy content of these perturbations, we employ the Teleparallel Equivalent of General Relativity (TEGR), which provides a well-defined expression for gravitational energy. The gravitational energy is computed up to second order in the perturbation parameter and expressed in terms of the quasinormal mode functions. Our results establish a direct connection between the dynamical response of regular black holes and the energy carried by their gravitational perturbations.