Antonio Dobado
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Research Interests
Antonio Dobado has a total of 92 co-authors. Here are the top co-authors by number of shared publications:
- Antonio L. Maroto
Departamento de Física Teórica and Instituto de Física de Partículas y del Cosmos (IPARCOS-UCM), Universidad Complutense de Madrid, 28040 Madrid, Spain
44 shared publications - Felipe J. Llanes-Estrada
Universidad Complutense de Madrid
34 shared publications - Maria Jose Herrero
Universidad Autónoma de Madrid
29 shared publications - Rafael Delgado López
Dept. Matemática Aplicadas a las TIC Universidad Politécnica de Madrid Nikola Tesla s/n 28031- Madrid Spain
23 shared publications - Álvaro de la Cruz-Dombriz
University of Cape Town
23 shared publications - José Alberto Ruiz Cembranos
Departamento de Física Teórica, Universidad Complutense de Madrid, 28040 Madrid, Spain
21 shared publications
Latest Publications
- Open Access
- 23 March 2026
- Published by American Physical Society (APS) in Physical Review D
- Vol. 113 (8)
Unitarization of R + α R 2 gravity
We make use of the improved K-matrix algorithm to obtain unitarized amplitudes in R + α R 2 gravity (the so-called Starobinsky model, of cosmological relevance). The procedure is of some complexity because infrared divergences are present and need to be properly regulated. We focus on the behavior of a bona fide scalar resonance, known to exist in this model, and compare it to an apparent resonance detected in previous studies, thus confirming that the latter seems to be an artifact due to the introduction of the infrared regulator. We analyze the existence of other dynamical resonances and dwell on the amplitudes made unitary by this procedure.
- 23 March 2026
- Published by American Physical Society (APS) in Physical Review D
- Vol. 113 (8)
Open AccessUnitarization of R + α R 2 gravity
We make use of the improved K-matrix algorithm to obtain unitarized amplitudes in R + α R 2 gravity (the so-called Starobinsky model, of cosmological relevance). The procedure is of some complexity because infrared divergences are present and need to be properly regulated. We focus on the behavior of a bona fide scalar resonance, known to exist in this model, and compare it to an apparent resonance detected in previous studies, thus confirming that the latter seems to be an artifact due to the introduction of the infrared regulator. We analyze the existence of other dynamical resonances and dwell on the amplitudes made unitary by this procedure.
- 11 February 2025
- Published by American Physical Society (APS) in Physical Review D
- Vol. 111 (4)
Propagating degrees of freedom on maximally symmetric backgrounds in theories of gravity- 11 February 2025
- Published by American Physical Society (APS) in Physical Review D
- Vol. 111 (4)
Propagating degrees of freedom on maximally symmetric backgrounds in theories of gravity- Open AccessPropagating degrees of freedom on maximally-symmetric backgrounds in $f(R)$ theories of gravityIn the context of $f(R)$ gravity, as well as other extended theories of gravity, the correct counting of globally well-defined dynamical modes has recently drawn a vivid interest. In this communication we present a consistent approach shedding light on such issues for both so-called degenerate and non-degenerate $f(R)$ models embedded in maximally-symmetric backgrounds. We find that the linearised spectrum of degenerate models on these backgrounds is empty, lacking both the graviton and scalaron modes which appear in generic non-degenerate models. Our work generalises previous results in the literature applicable only to the specific (degenerate) model $f(R)=αR^2$; in fact, we find that the same pathologies discovered therein emerge for all choices of $f(R)$ belonging to the wide class of degenerate models.Open AccessPropagating degrees of freedom on maximally-symmetric backgrounds in $f(R)$ theories of gravityIn the context of $f(R)$ gravity, as well as other extended theories of gravity, the correct counting of globally well-defined dynamical modes has recently drawn a vivid interest. In this communication we present a consistent approach shedding light on such issues for both so-called degenerate and non-degenerate $f(R)$ models embedded in maximally-symmetric backgrounds. We find that the linearised spectrum of degenerate models on these backgrounds is empty, lacking both the graviton and scalaron modes which appear in generic non-degenerate models. Our work generalises previous results in the literature applicable only to the specific (degenerate) model $f(R)=αR^2$; in fact, we find that the same pathologies discovered therein emerge for all choices of $f(R)$ belonging to the wide class of degenerate models.
- 6 September 2023
- Published by American Physical Society (APS) in Physical Review D
- Vol. 108 (6) , 064006
Physical nonviability of a wide class of models and their constant-curvature solutionsConstant-curvature solutions lie at the very core of gravitational physics, with Schwarzschild and (anti-)de Sitter being two of the most paradigmatic examples. Although such a kind of solutions are very well-known in general relativity, that is not the case for theories of gravity beyond the Einsteinian paradigm. In this article, we provide a systematic overview on models allowing for constant-curvature solutions, as well as of the constant-curvature solutions themselves. We conclude that the vast majority of these models suffer, in general, from several shortcomings rendering their viability extremely limited, when not ruled out by physical evidence. Among these deficiencies are instabilities (including previously unforeseen strong-coupling problems) and issues limiting the predictive power of the models. Furthermore, we will also show that most -exclusive constant-curvature solutions also exhibit a variety of unphysical properties.- 6 September 2023
- Published by American Physical Society (APS) in Physical Review D
- Vol. 108 (6) , 064006
Physical nonviability of a wide class of models and their constant-curvature solutionsConstant-curvature solutions lie at the very core of gravitational physics, with Schwarzschild and (anti-)de Sitter being two of the most paradigmatic examples. Although such a kind of solutions are very well-known in general relativity, that is not the case for theories of gravity beyond the Einsteinian paradigm. In this article, we provide a systematic overview on models allowing for constant-curvature solutions, as well as of the constant-curvature solutions themselves. We conclude that the vast majority of these models suffer, in general, from several shortcomings rendering their viability extremely limited, when not ruled out by physical evidence. Among these deficiencies are instabilities (including previously unforeseen strong-coupling problems) and issues limiting the predictive power of the models. Furthermore, we will also show that most -exclusive constant-curvature solutions also exhibit a variety of unphysical properties.- Open Access
- 18 May 2023
- Published by American Physical Society (APS) in Physical Review D
- Vol. 107 (9) , 093006
Relevance of fermion loops for scattering at the LHCWe study the one-loop corrections to elastic scattering within the framework of effective theories. Rescattering via intermediate electroweak would-be-Goldstone bosons dominate at high energies, as the corresponding loop diagrams with these intermediate bosons scale like in the chiral effective counting. In the present article, we focus our attention on the usually neglected fermion-loop corrections which scale like in the Higgs effective field theory (HEFT). Although this dependency is formally suppressed for with respect to the ones from boson loops, the large top mass can lead to a numerical competition between fermion and boson loops at intermediate energies of the order of a few TeV. The central goal of the present study is to assess the importance of these fermion loops. For this, since the fermion contribution scales with the mass of the fermions, we have calculated the imaginary part induced by loops of the heaviest fermions, top and bottom quarks, in elastic scattering and compared them with the loop contributions from purely bosonic loops, as a large imaginary part would be a clear indicator of large fermion-loop effects. We have examined the dependence of both amplitudes on the effective couplings, allowing an deviation from the Standard Model. In some cases, boson loops dominate over top and bottom corrections, as expected. However, we find that there are regions in the space of effective parameters that yield a significant—and even dominant—imaginary contribution from fermion loops. In addition to our conclusions for the general HEFT, we also provide analyses particularized to some benchmark points in the minimal composite Higgs model.- 18 May 2023
- Published by American Physical Society (APS) in Physical Review D
- Vol. 107 (9) , 093006
Open AccessRelevance of fermion loops for scattering at the LHCWe study the one-loop corrections to elastic scattering within the framework of effective theories. Rescattering via intermediate electroweak would-be-Goldstone bosons dominate at high energies, as the corresponding loop diagrams with these intermediate bosons scale like in the chiral effective counting. In the present article, we focus our attention on the usually neglected fermion-loop corrections which scale like in the Higgs effective field theory (HEFT). Although this dependency is formally suppressed for with respect to the ones from boson loops, the large top mass can lead to a numerical competition between fermion and boson loops at intermediate energies of the order of a few TeV. The central goal of the present study is to assess the importance of these fermion loops. For this, since the fermion contribution scales with the mass of the fermions, we have calculated the imaginary part induced by loops of the heaviest fermions, top and bottom quarks, in elastic scattering and compared them with the loop contributions from purely bosonic loops, as a large imaginary part would be a clear indicator of large fermion-loop effects. We have examined the dependence of both amplitudes on the effective couplings, allowing an deviation from the Standard Model. In some cases, boson loops dominate over top and bottom corrections, as expected. However, we find that there are regions in the space of effective parameters that yield a significant—and even dominant—imaginary contribution from fermion loops. In addition to our conclusions for the general HEFT, we also provide analyses particularized to some benchmark points in the minimal composite Higgs model. - Open AccessPhysical non-viability of a wide class of $f(R)$ models and their constant-curvature solutionsConstant-curvature solutions lie at the very core of gravitational physics, with Schwarzschild and (Anti)-de Sitter being two of the most paradigmatic examples. Although such kind of solutions are very well-known in General Relativity, that is not the case for theories of gravity beyond the Einsteinian paradigm. In this article, we provide a systematic overview on $f(R)$ models allowing for constant-curvature solutions, as well as of the constant-curvature solutions themselves. We conclude that the vast majority of these $f(R)$ models suffer, in general, from several shortcomings rendering their viability extremely limited, when not ruled out by physical evidence. Among these deficiencies are instabilities (including previously unforeseen strong-coupling problems) and issues limiting the predictive power of the models. Furthermore, we will also show that most $f(R)$-exclusive constant-curvature solutions also exhibit a variety of unphysical properties.Open AccessPhysical non-viability of a wide class of $f(R)$ models and their constant-curvature solutionsConstant-curvature solutions lie at the very core of gravitational physics, with Schwarzschild and (Anti)-de Sitter being two of the most paradigmatic examples. Although such kind of solutions are very well-known in General Relativity, that is not the case for theories of gravity beyond the Einsteinian paradigm. In this article, we provide a systematic overview on $f(R)$ models allowing for constant-curvature solutions, as well as of the constant-curvature solutions themselves. We conclude that the vast majority of these $f(R)$ models suffer, in general, from several shortcomings rendering their viability extremely limited, when not ruled out by physical evidence. Among these deficiencies are instabilities (including previously unforeseen strong-coupling problems) and issues limiting the predictive power of the models. Furthermore, we will also show that most $f(R)$-exclusive constant-curvature solutions also exhibit a variety of unphysical properties.
- Open Access
- 28 February 2023
- Published by American Physical Society (APS) in Physical Review D
- Vol. 107 (4) , 044073
Seeking for resonances in unitarized one-loop graviton-graviton scattering
Some effective field theories exhibit dynamical resonances that, when properly included, mitigate their bad behavior at high energies. Unitarization of the partial wave amplitudes is the preferred method to unveil such resonances. Interpreting the Einstein-Hilbert theory in the spirit of effective Lagrangians, we implement the inverse amplitude method and unitarize the one-loop level graviton-graviton scattering in pure gravity. Due to the presence of infrared divergences, the analysis requires a careful treatment of the infrared region and the introduction of infrared regulators, carefully selected in order to fulfill perturbative unitarity.
- 28 February 2023
- Published by American Physical Society (APS) in Physical Review D
- Vol. 107 (4) , 044073
Open AccessSeeking for resonances in unitarized one-loop graviton-graviton scattering
Some effective field theories exhibit dynamical resonances that, when properly included, mitigate their bad behavior at high energies. Unitarization of the partial wave amplitudes is the preferred method to unveil such resonances. Interpreting the Einstein-Hilbert theory in the spirit of effective Lagrangians, we implement the inverse amplitude method and unitarize the one-loop level graviton-graviton scattering in pure gravity. Due to the presence of infrared divergences, the analysis requires a careful treatment of the infrared region and the introduction of infrared regulators, carefully selected in order to fulfill perturbative unitarity.
- Open Access
Seeking for resonances in unitarized one-loop graviton-graviton scattering
Some effective field theories exhibit dynamical resonances that, when properly included, mitigate their bad behaviour at high energies. Unitarization of the partial wave amplitudes is the preferred method to unveil such resonances. Interpreting the Einstein-Hilbert theory in the spirit of effective Lagrangians, we implement the Inverse Amplitude Method and unitarize the one-loop level graviton-graviton scattering in pure gravity. Due to the presence of infrared divergences, the analysis requires a careful treatment of the infrared region and the introduction of infrared regulators, carefully selected in order to fulfil perturbative unitarity. No evidence of any graviball is found, in contradiction with a recent study.
Open AccessSeeking for resonances in unitarized one-loop graviton-graviton scattering
Some effective field theories exhibit dynamical resonances that, when properly included, mitigate their bad behaviour at high energies. Unitarization of the partial wave amplitudes is the preferred method to unveil such resonances. Interpreting the Einstein-Hilbert theory in the spirit of effective Lagrangians, we implement the Inverse Amplitude Method and unitarize the one-loop level graviton-graviton scattering in pure gravity. Due to the presence of infrared divergences, the analysis requires a careful treatment of the infrared region and the introduction of infrared regulators, carefully selected in order to fulfil perturbative unitarity. No evidence of any graviball is found, in contradiction with a recent study.
- Open Access
- 22 December 2022
- Published by EDP Sciences in EPJ Web of Conferences
- Vol. 274, 08010
Unitarized one-loop graviton-graviton scattering
In this work we interpret the Einstein-Hilbert (EH) Lagrangian of gravitation as the first term of a low-energy effective theory similar to those considered in the chiral Lagrangian approach to low-energy hadron physics or the electroweak chiral Lagragians describing the symmetry breaking sector of the Standard Model (SM). Starting from the one-loop computation of the elastic gravitongraviton scattering amplitude by Dunbar and Norridge, we unitarize the IR regularized partial waves by using the Inverse Amplitude Method (IAM). This method enlarges the regime of applicability of the perturbative results to higher energies of the order of the Plank scale MP and allows for the possibility of poles in the second Riemann which have the natural interpretation of dynamical resonances. In this work we look for these possible resonances for the ++++ and −−−− helicity channels and the J = 0, 2 and 4 partial waves.
- 22 December 2022
- Published by EDP Sciences in EPJ Web of Conferences
- Vol. 274, 08010
Open AccessUnitarized one-loop graviton-graviton scattering
In this work we interpret the Einstein-Hilbert (EH) Lagrangian of gravitation as the first term of a low-energy effective theory similar to those considered in the chiral Lagrangian approach to low-energy hadron physics or the electroweak chiral Lagragians describing the symmetry breaking sector of the Standard Model (SM). Starting from the one-loop computation of the elastic gravitongraviton scattering amplitude by Dunbar and Norridge, we unitarize the IR regularized partial waves by using the Inverse Amplitude Method (IAM). This method enlarges the regime of applicability of the perturbative results to higher energies of the order of the Plank scale MP and allows for the possibility of poles in the second Riemann which have the natural interpretation of dynamical resonances. In this work we look for these possible resonances for the ++++ and −−−− helicity channels and the J = 0, 2 and 4 partial waves.
- 28 April 2022
- Published by American Physical Society (APS) in Physical Review D
- Vol. 105 (8) , 084060
Is gravitational collapse possible in gravity?Gravitational collapse is still poorly understood in the context of theories of gravity, since the Oppenheimer-Snyder model is incompatible with their junction conditions. In this work, we will present a systematic approach to the problem. Starting with a thorough analysis of how the Oppenheimer-Snyder construction should be generalized to fit within metric gravity, we shall subsequently proceed to explore the existence of novel exterior solutions compatible with physically viable interiors. Our formalism has allowed us to show that some paradigmatic vacuum metrics cannot represent spacetime outside a collapsing dust star in metric gravity. Moreover, using the junction conditions, we have found a novel vacuole solution of a large class of models, whose exterior spacetime is documented here for the first time in the literature as well. Finally, we also report the previously unnoticed fact that the Oppenheimer-Snyder model of gravitational collapse is incompatible with the junction conditions of the Palatini formulation of gravity.- 28 April 2022
- Published by American Physical Society (APS) in Physical Review D
- Vol. 105 (8) , 084060
Is gravitational collapse possible in gravity?Gravitational collapse is still poorly understood in the context of theories of gravity, since the Oppenheimer-Snyder model is incompatible with their junction conditions. In this work, we will present a systematic approach to the problem. Starting with a thorough analysis of how the Oppenheimer-Snyder construction should be generalized to fit within metric gravity, we shall subsequently proceed to explore the existence of novel exterior solutions compatible with physically viable interiors. Our formalism has allowed us to show that some paradigmatic vacuum metrics cannot represent spacetime outside a collapsing dust star in metric gravity. Moreover, using the junction conditions, we have found a novel vacuole solution of a large class of models, whose exterior spacetime is documented here for the first time in the literature as well. Finally, we also report the previously unnoticed fact that the Oppenheimer-Snyder model of gravitational collapse is incompatible with the junction conditions of the Palatini formulation of gravity.