Cláudio Gomes
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
Cláudio Gomes has a total of 21 co-authors. Here are the top co-authors by number of shared publications:
- Orfeu Bertolami
Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal
27 shared publications - Joao G. Rosa
Univ Coimbra, Faculdade de Ciências e Tecnologia da Universidade de Coimbra and CFisUC
4 shared publications - Margarida Lima
Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
4 shared publications - Francisco S. N. Lobo
Universidade de Lisboa
3 shared publications - Ariel Guerreiro
INESC TEC, Portugal; University of Porto, Portugal
2 shared publications - Nuno Azevedo Silva
Faculdade de Ciências da Universidade do Porto
2 shared publications
Latest Publications
- Open Access
- 26 October 2026
- Published by Springer Nature in The European Physical Journal C
- Vol. 86 (10) , 1226
Non-minimally coupled Weyl connection gravity in the Solar System and at the Galactic Center
We explore the phenomenological viability of non-minimally coupled Weyl connection gravity by confronting its static, spherically symmetric black hole solutions with classical weak-field Solar System tests and stellar-orbit observations near Sgr A*. In this geometric framework, non-metricity is encoded via a Weyl vector field, giving rise to two distinct families of Schwarzschild-like vacuum solutions characterized by a free parameter $$\omega $$ with dimensions of length. We compute the corrections to four classical observables – gravitational redshift, Mercury’s perihelion advance, light deflection, and radar echo delay – and derive stringent lower bounds on $$\omega $$ using current observational data. For Solution I (purely radial Weyl vector), the leading metric corrections scale as $$1/\omega $$ , yielding bounds as strong as $$\omega > rsim 10^{30}$$ m from perihelion precession. For Solution II (time-radial Weyl vector), the corrections scale as $$1/\omega ^2$$ , resulting in weaker constraints, with $$\omega > rsim 10^{20}$$ m from the same test. This marked difference arises from the distinct behavior of the linear corrections in each solution: while Solution I exhibits an unsuppressed linear term $$2r/\omega $$ that dominates in the Solar System regime, Solution II features a linear term suppressed by an additional factor of $$M/\omega $$ , making the quadratic term $$-r^2/4\omega ^2$$ dominant throughout. We then analyze stellar orbits near the Galactic Center, finding that current observations of the S2 star provide complementary constraints on both solutions. For Solution I, the S2 periastron precession yields $$\omega > rsim 10^{21}$$ m, while the S2 gravitational redshift provides the stronger constraint $$\omega > rsim 10^{24}$$ m. For Solution II, the corresponding bounds are $$\omega > rsim 10^{17}$$ m from periastron precession and $$\omega > rsim 10^{22}$$ m from gravitational redshift. While Solar System tests probe the weak-field regime, these stellar-orbit observations extend the analysis to a substantially stronger gravitational environment. The stellar-orbit analysis reveals a qualitative distinction: Solution I produces a retrograde correction to the periastron precession, while Solution II produces a prograde one, mirroring the behavior identified in the Solar System. Finally, despite both solutions sharing the same quadratic asymptotic structure, only Solution II can accommodate an effective cosmological constant of the same order as the observed value, $$\Lambda _{\textrm{obs}} \sim 10^{-52}$$ m $$^{-2}$$ , while Solution I is constrained to produce a negligibly small effective $$\Lambda $$ .- 26 October 2026
- Published by Springer Nature in The European Physical Journal C
- Vol. 86 (10) , 1226
Open AccessNon-minimally coupled Weyl connection gravity in the Solar System and at the Galactic Center
We explore the phenomenological viability of non-minimally coupled Weyl connection gravity by confronting its static, spherically symmetric black hole solutions with classical weak-field Solar System tests and stellar-orbit observations near Sgr A*. In this geometric framework, non-metricity is encoded via a Weyl vector field, giving rise to two distinct families of Schwarzschild-like vacuum solutions characterized by a free parameter $$\omega $$ with dimensions of length. We compute the corrections to four classical observables – gravitational redshift, Mercury’s perihelion advance, light deflection, and radar echo delay – and derive stringent lower bounds on $$\omega $$ using current observational data. For Solution I (purely radial Weyl vector), the leading metric corrections scale as $$1/\omega $$ , yielding bounds as strong as $$\omega > rsim 10^{30}$$ m from perihelion precession. For Solution II (time-radial Weyl vector), the corrections scale as $$1/\omega ^2$$ , resulting in weaker constraints, with $$\omega > rsim 10^{20}$$ m from the same test. This marked difference arises from the distinct behavior of the linear corrections in each solution: while Solution I exhibits an unsuppressed linear term $$2r/\omega $$ that dominates in the Solar System regime, Solution II features a linear term suppressed by an additional factor of $$M/\omega $$ , making the quadratic term $$-r^2/4\omega ^2$$ dominant throughout. We then analyze stellar orbits near the Galactic Center, finding that current observations of the S2 star provide complementary constraints on both solutions. For Solution I, the S2 periastron precession yields $$\omega > rsim 10^{21}$$ m, while the S2 gravitational redshift provides the stronger constraint $$\omega > rsim 10^{24}$$ m. For Solution II, the corresponding bounds are $$\omega > rsim 10^{17}$$ m from periastron precession and $$\omega > rsim 10^{22}$$ m from gravitational redshift. While Solar System tests probe the weak-field regime, these stellar-orbit observations extend the analysis to a substantially stronger gravitational environment. The stellar-orbit analysis reveals a qualitative distinction: Solution I produces a retrograde correction to the periastron precession, while Solution II produces a prograde one, mirroring the behavior identified in the Solar System. Finally, despite both solutions sharing the same quadratic asymptotic structure, only Solution II can accommodate an effective cosmological constant of the same order as the observed value, $$\Lambda _{\textrm{obs}} \sim 10^{-52}$$ m $$^{-2}$$ , while Solution I is constrained to produce a negligibly small effective $$\Lambda $$ . - Open Access
- 26 June 2026
- Published by Springer Nature in The European Physical Journal C
- Vol. 86 (6)
Black hole shadows in nonminimally coupled Weyl connection gravity
We study black hole shadows in nonminimally coupled Weyl connection gravity, a metric-affine extension of general relativity in which spacetime is described by a metric and a Weyl vector field encoding non-metricity. Despite going beyond the Riemannian framework, the presence of a non-dynamical Weyl vector ensures second-order field equations. The theory admits Schwarzschild- and Reissner–Nordström-like solutions modified by a Weyl integration constant that parametrizes deviations from General Relativity. By computing the corresponding shadow radii and confronting them with the Event Horizon Telescope constraints on Sgr A*, we place observational bounds on the Weyl parameter. Assuming an observer distance $$r_O = 4.1\times 10^{10}M$$ and requiring consistency at the $$2\sigma $$ level, we obtain $$\omega \gtrsim 10^{11.7}M$$ (model I), $$\omega \gtrsim 10^{10.5}M$$ (model II), and $$\omega \sim 10^{12}M$$ (model III). Our results show that present horizon-scale imaging already sets meaningful limits on spacetime non-metricity. This work highlights the power of black hole shadow observations as probes of extended gravitational dynamics and establishes a direct link between Weyl-based theories and current astrophysical data.- 26 June 2026
- Published by Springer Nature in The European Physical Journal C
- Vol. 86 (6)
Open AccessBlack hole shadows in nonminimally coupled Weyl connection gravity
We study black hole shadows in nonminimally coupled Weyl connection gravity, a metric-affine extension of general relativity in which spacetime is described by a metric and a Weyl vector field encoding non-metricity. Despite going beyond the Riemannian framework, the presence of a non-dynamical Weyl vector ensures second-order field equations. The theory admits Schwarzschild- and Reissner–Nordström-like solutions modified by a Weyl integration constant that parametrizes deviations from General Relativity. By computing the corresponding shadow radii and confronting them with the Event Horizon Telescope constraints on Sgr A*, we place observational bounds on the Weyl parameter. Assuming an observer distance $$r_O = 4.1\times 10^{10}M$$ and requiring consistency at the $$2\sigma $$ level, we obtain $$\omega \gtrsim 10^{11.7}M$$ (model I), $$\omega \gtrsim 10^{10.5}M$$ (model II), and $$\omega \sim 10^{12}M$$ (model III). Our results show that present horizon-scale imaging already sets meaningful limits on spacetime non-metricity. This work highlights the power of black hole shadow observations as probes of extended gravitational dynamics and establishes a direct link between Weyl-based theories and current astrophysical data. - 24 December 2025
- Published by World Scientific Pub Co Pte Ltd in Modern Physics Letters A
On scalar cosmological perturbations in non-minimally coupled Weyl connection gravity
We analyze a theory with non-minimal matter–curvature coupling, considering non-metricity properties with a Weyl connection. This model has the advantage of an extra force term which can mimic dark matter and dark energy, and simultaneously follow Weyl’s idea to unify gravity and electromagnetism. Indeed, Schwarzschild-like and Reissner–Nordström-like black hole solutions exist in this model, leading to new features, such as an additional horizon, due to the non-metricity vector. We derive the cosmological field equations, considering a minimal coupling, and discuss preliminary results on the scalar cosmological perturbations in this model.
- 24 December 2025
- Published by World Scientific Pub Co Pte Ltd in Modern Physics Letters A
On scalar cosmological perturbations in non-minimally coupled Weyl connection gravity
We analyze a theory with non-minimal matter–curvature coupling, considering non-metricity properties with a Weyl connection. This model has the advantage of an extra force term which can mimic dark matter and dark energy, and simultaneously follow Weyl’s idea to unify gravity and electromagnetism. Indeed, Schwarzschild-like and Reissner–Nordström-like black hole solutions exist in this model, leading to new features, such as an additional horizon, due to the non-metricity vector. We derive the cosmological field equations, considering a minimal coupling, and discuss preliminary results on the scalar cosmological perturbations in this model.
- 12 December 2025
- Published by World Scientific Pub Co Pte Ltd in Modern Physics Letters A
Testing the dark Universe through the Layzer–Irvine equation
We review the cosmic generalization of the virial theorem known as the Layzer–Irvine equation, also independently derived by Dmitriev and Zeldovich. This equation has been studied in the literature for dark matter–dark energy interaction models, as well as in the context of alternative theories of gravity. We discuss results from the previous scenarios and point out future directions.
- 12 December 2025
- Published by World Scientific Pub Co Pte Ltd in Modern Physics Letters A
Testing the dark Universe through the Layzer–Irvine equation
We review the cosmic generalization of the virial theorem known as the Layzer–Irvine equation, also independently derived by Dmitriev and Zeldovich. This equation has been studied in the literature for dark matter–dark energy interaction models, as well as in the context of alternative theories of gravity. We discuss results from the previous scenarios and point out future directions.
- Open Access
- 26 November 2025
- Published by Springer Nature in The European Physical Journal C
- Vol. 85 (11) , 1359
Gravitational wave propagation in generalized hybrid metric-Palatini gravity
In this work we analyze the propagation properties of gravitational waves in the generalized hybrid metric-Palatini gravity theory. We introduce the scalar-tensor representation of the theory to make explicit the scalar degrees of freedom of the theory and obtain their equations of motion in a form decoupled from the metric tensor. Then, we introduce linear perturbations for the metric tensor and for the two scalar fields and obtain the propagation equations for these three quantities. We analyzed the theory both at non-linear and at linear level through the Newman–Penrose formalism so to find the polarization states. We show that the tensor modes propagate at the speed of light and feature the usual $$+$$ - and $$\times $$ -polarization modes also present in General Relativity (GR), plus two additional polarization modes: a longitudinal mode and a breathing mode, described by the same additional degree of freedom. On the other hand, the theory features two additional scalar modes not present in GR. These modes are massive and, thus, propagate with a speed smaller than the speed of light in general. The masses of the scalar modes depend solely on the interaction potential between the two scalar fields in the theory, which suggests that one can always fine-tune the potential to make the scalar modes massless and reduce their propagation speed to the speed of light. Given the possibility of fine-tuning the theory to match the observational predictions of GR and in the absence of any measured deviations, these features potentially render the generalized hybrid metric-Palatini theory unfalsifiable in the context of gravitational wave propagation.- 26 November 2025
- Published by Springer Nature in The European Physical Journal C
- Vol. 85 (11) , 1359
Open AccessGravitational wave propagation in generalized hybrid metric-Palatini gravity
In this work we analyze the propagation properties of gravitational waves in the generalized hybrid metric-Palatini gravity theory. We introduce the scalar-tensor representation of the theory to make explicit the scalar degrees of freedom of the theory and obtain their equations of motion in a form decoupled from the metric tensor. Then, we introduce linear perturbations for the metric tensor and for the two scalar fields and obtain the propagation equations for these three quantities. We analyzed the theory both at non-linear and at linear level through the Newman–Penrose formalism so to find the polarization states. We show that the tensor modes propagate at the speed of light and feature the usual $$+$$ - and $$\times $$ -polarization modes also present in General Relativity (GR), plus two additional polarization modes: a longitudinal mode and a breathing mode, described by the same additional degree of freedom. On the other hand, the theory features two additional scalar modes not present in GR. These modes are massive and, thus, propagate with a speed smaller than the speed of light in general. The masses of the scalar modes depend solely on the interaction potential between the two scalar fields in the theory, which suggests that one can always fine-tune the potential to make the scalar modes massless and reduce their propagation speed to the speed of light. Given the possibility of fine-tuning the theory to match the observational predictions of GR and in the absence of any measured deviations, these features potentially render the generalized hybrid metric-Palatini theory unfalsifiable in the context of gravitational wave propagation. - Open Access
Black Hole Solutions in Non-Minimally Coupled Weyl Connection Gravity
Schwarzschild and Reissner–Nordstrøm black hole solutions are found in the context of a non-minimal matter–curvature coupling with Weyl connection both in vacuum and in the presence of a cosmological constant-like matter content. This model has the advantage of an extra force term which can mimic dark matter and dark energy, and simultaneously following Weyl’s idea of unifying gravity and electromagnetism. In fact, vacuum Schwarzschild solutions differ from the ones in a constant curvature scenario in theories, with the appearance of a coefficient in the term that is linear in r and a corrected “cosmological constant”. Non-vacuum Schwarzschild solutions formally have the same solutions as in the previous case, with the exception being the physical interpretation of a cosmological constant as the source of the matter Lagrangian and not a simple reparameterization of the description. Reissner–Nordstrøm solutions cannot be found in a vacuum, only in the presence of matter fields, with the result that the solutions also differ from the constant curvature scenario in theories by the term being linear in r, the corrected/dressed charge, and the cosmological constant. These results have bearings on future numerical simulations for black holes and gravitational waves in next-generation wavelet templates.Open AccessBlack Hole Solutions in Non-Minimally Coupled Weyl Connection Gravity
Schwarzschild and Reissner–Nordstrøm black hole solutions are found in the context of a non-minimal matter–curvature coupling with Weyl connection both in vacuum and in the presence of a cosmological constant-like matter content. This model has the advantage of an extra force term which can mimic dark matter and dark energy, and simultaneously following Weyl’s idea of unifying gravity and electromagnetism. In fact, vacuum Schwarzschild solutions differ from the ones in a constant curvature scenario in theories, with the appearance of a coefficient in the term that is linear in r and a corrected “cosmological constant”. Non-vacuum Schwarzschild solutions formally have the same solutions as in the previous case, with the exception being the physical interpretation of a cosmological constant as the source of the matter Lagrangian and not a simple reparameterization of the description. Reissner–Nordstrøm solutions cannot be found in a vacuum, only in the presence of matter fields, with the result that the solutions also differ from the constant curvature scenario in theories by the term being linear in r, the corrected/dressed charge, and the cosmological constant. These results have bearings on future numerical simulations for black holes and gravitational waves in next-generation wavelet templates. - 4 April 2023
- Published by American Physical Society (APS) in Physical Review D
- Vol. 107 (8) , 084009
Theories of gravity with nonminimal matter-curvature coupling and the de Sitter swampland conjectures
We discuss, in the context of alternative theories of gravity with nonminimal coupling between matter and curvature, if inflationary solutions driven by a single scalar field can be reconciled with the swampland conjectures about the emergence of de Sitter solutions in string theory. We find that the slow-roll conditions are incompatible with the swampland conjectures for a fairly generic inflationary solution in such alternative theories of gravity.
- 4 April 2023
- Published by American Physical Society (APS) in Physical Review D
- Vol. 107 (8) , 084009
Theories of gravity with nonminimal matter-curvature coupling and the de Sitter swampland conjectures
We discuss, in the context of alternative theories of gravity with nonminimal coupling between matter and curvature, if inflationary solutions driven by a single scalar field can be reconciled with the swampland conjectures about the emergence of de Sitter solutions in string theory. We find that the slow-roll conditions are incompatible with the swampland conjectures for a fairly generic inflationary solution in such alternative theories of gravity.
- Open Access
- 19 January 2023
- Published by Springer Nature in The European Physical Journal C
- Vol. 83 (1) , 1-12
Quantum kinetic theory of Jeans instability in non-minimal matter-curvature coupling gravity
We present a quantum treatment of the Jeans gravitational instability in the Newtonian limit of the non-minimal matter-curvature coupling gravity model. By relying on Wigner functions, allowing for the representation of quantum states in a classical phase space, we formulate a quantum kinetic treatment of this problem, generalizing the classical kinetic approach (Gomes in Eur Phys J C 80:633, 2020). This allows us to study the interplay between non-minimal matter-curvature coupling effects, quantum effects, and kinetic (finite-temperature) effects, on the Jeans criterion. We study in detail special cases of the model (general relativity, f(R) theories, pure non-minimal coupling, etc.) and confront the model with the observed stability of Bok globules.
- 19 January 2023
- Published by Springer Nature in The European Physical Journal C
- Vol. 83 (1) , 1-12
Open AccessQuantum kinetic theory of Jeans instability in non-minimal matter-curvature coupling gravity
We present a quantum treatment of the Jeans gravitational instability in the Newtonian limit of the non-minimal matter-curvature coupling gravity model. By relying on Wigner functions, allowing for the representation of quantum states in a classical phase space, we formulate a quantum kinetic treatment of this problem, generalizing the classical kinetic approach (Gomes in Eur Phys J C 80:633, 2020). This allows us to study the interplay between non-minimal matter-curvature coupling effects, quantum effects, and kinetic (finite-temperature) effects, on the Jeans criterion. We study in detail special cases of the model (general relativity, f(R) theories, pure non-minimal coupling, etc.) and confront the model with the observed stability of Bok globules.
- Open Access
Theories of gravity with nonminimal matter-curvature coupling and the de Sitter swampland conjectures
We discuss, in the context of alternative theories of gravity with nonminimal coupling between matter and curvature, if inflationary solutions driven by a single scalar field can be reconciled with the swampland conjectures about the emergence of de Sitter solutions in string theory. We find that the slow-roll conditions are incompatible with the swampland conjectures for a fairly generic inflationary solution in such alternative theories of gravity.
Open AccessTheories of gravity with nonminimal matter-curvature coupling and the de Sitter swampland conjectures
We discuss, in the context of alternative theories of gravity with nonminimal coupling between matter and curvature, if inflationary solutions driven by a single scalar field can be reconciled with the swampland conjectures about the emergence of de Sitter solutions in string theory. We find that the slow-roll conditions are incompatible with the swampland conjectures for a fairly generic inflationary solution in such alternative theories of gravity.
- 30 September 2022
- Published by ICETA in Revista de Ciência Elementar
- Vol. 10 (3)
Inflação cósmica
A inflação cósmica corresponde ao paradigma associado ao período de expansão exponencial, ou aproximadamente exponencial, do Universo primordial entre, sensivelmente, 10-36 e 10-32 segundos após o Big Bang. As evidências observacionais para este cenário encontram-se na radiação cósmica de fundo, resolvendo os problemas do modelo do Big Bang quente e explicando a origem das estruturas cosmológicas.
- 30 September 2022
- Published by ICETA in Revista de Ciência Elementar
- Vol. 10 (3)
Inflação cósmica
A inflação cósmica corresponde ao paradigma associado ao período de expansão exponencial, ou aproximadamente exponencial, do Universo primordial entre, sensivelmente, 10-36 e 10-32 segundos após o Big Bang. As evidências observacionais para este cenário encontram-se na radiação cósmica de fundo, resolvendo os problemas do modelo do Big Bang quente e explicando a origem das estruturas cosmológicas.