Diego Rubiera-García

Universidad Complutense de Madrid

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Gonzalo J. Olmo

Universidade Federal do Ceará

108

Francisco S. N. Lobo

University of Lisbon

Diego Sáez-Gómez

Universidad de Valladolid

J. Díaz-Alonso

Universidad de Oviedo

Merce Guerrero

Universidad Complutense de Madrid

Luís F. Dias da Silva

Institute of Astrophysics and Space Sciences

Emanuele Orazi

Universidade Federal do Rio Grande do Norte

Aneta Wojnar

University of Wrocław

Gerardo Mora-Pérez

Universitat de València

Antonio Sánchez-Puente

Universidad de Salamanca

Cooperative Institutions

Centre National de la Recherche Scientifique

127

University of Lisbon

Sorbonne Université

Université Paris Cité

Istituto Nazionale di Fisica Nucleare

Max Planck Institute for Gravitational Physics

University College London

Istituto Nazionale di Fisica Nucleare, Sezione di Napoli

University of Cambridge

Institute of Astrophysics and Space Sciences

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Coupling matter in modifiedQgravity

Physical review. D/Physical review. D. (2018)

Tiberiu Harko Tomi Koivisto Francisco S. N. Lobo Gonzalo J. Olmo Diego Rubiera-García

We present a novel theory of gravity by considering an extension of symmetric teleparallel gravity. This is done by introducing, in the framework of the metric-affine formalism, a new class of theories where the nonmetricity $Q$ is nonminimally coupled to the matter Lagrangian. More specifically, we consider a Lagrangian of the form $L\ensuremath{\sim}{f}_{1}(Q)+{f}_{2}(Q){L}_{M}$, where ${f}_{1}$ and ${f}_{2}$ are generic functions of $Q$, and ${L}_{M}$ is the matter Lagrangian. This nonminimal coupling entails the nonconservation of the energy-momentum tensor, and consequently the appearance of an extra force. The formulation of the gravity sector in terms of the $Q$ instead of the curvature may result in subtle improvements of the theory. In the context of nonminimal matter couplings, we are therefore motivated to explore whether the new geometrical formulation in terms of the $Q$, when implemented also in the matter sector, would allow more universally consistent and viable realizations of the nonminimal coupling. Furthermore, we consider several cosmological applications by presenting the evolution equations and imposing specific functional forms of the functions ${f}_{1}(Q)$ and ${f}_{2}(Q)$, such as power-law and exponential dependencies of the nonminimal couplings. Cosmological solutions are considered in two general classes of models, and found to feature accelerating expansion at late times.

Formalism (music)

10.1103/physrevd.98.084043

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Citations (257)

NONSINGULAR CHARGED BLACK HOLES À LA PALATINI

International Journal of Modern Physics D (2012)

Gonzalo J. Olmo Diego Rubiera-García

We argue that the quantum nature of matter and gravity should lead to a discretization of the allowed states of the matter confined in the interior of black holes. To support and illustrate this idea, we consider a quadratic extension of general relativity (GR) formulated à la Palatini and show that nonrotating, electrically charged black holes develop a compact core at the Planck density which is nonsingular if the mass spectrum satisfies a certain discreteness condition. We also find that the area of the core is proportional to the number of charges times the Planck area.

Black hole (networking)

Planck mass

Planck length

10.1142/s0218271812500678

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Citations (36)

Singularity-free and cosmologically viable Born-Infeld gravity with scalar matter

arXiv (Cornell University) (2021)

David Benisty Gonzalo J. Olmo Diego Rubiera-García

The early Cosmology driven by a single scalar field, both massless and massive, in the context of Eddington-inspired Born-Infeld gravity, is explored. We show the existence of nonsingular solutions of bouncing and loitering type (depending on the sign of the gravitational theory's parameter, $\epsilon$) replacing the Big Bang singularity, and discuss their properties. In addition, in the massive case we find some new features of the cosmological evolution depending on the value of the mass parameter, including asymmetries in the expansion/contraction phases, or a continuous transition between a contracting phase to an expanding one via an intermediate loitering phase. We also provide a combined analysis of cosmic chronometers, standard candles, BAO, and CMB data to constrain the model, finding that for roughly $\vert \epsilon \vert \lesssim 5\cdot 10^{-8} \text{ m}^2$ the model is compatible with the latest observations while successfully removing the Big Bang singularity. This bound is several orders of magnitude stronger than the most stringent constraints currently available in the literature

Initial singularity

Massless particle

10.48550/arxiv.2103.15437

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Geometric aspects of charged black holes in Palatini theories

Journal of Physics Conference Series (2015)

Gonzalo J. Olmo Diego Rubiera-García Antonio Sánchez-Puente

Charged black holes in gravity theories in the Palatini formalism present a number of unique properties. Their innermost structure is topologically nontrivial, representing a wormhole supported by a sourceless electric flux. For certain values of their effective mass and charge curvature divergences may be absent, and their event horizon may also disappear yielding a remnant. We give an overview of the mathematical derivation of these solutions and discuss their geodesic structure and other geometric properties.

Wormhole

Formalism (music)

Black hole (networking)

10.1088/1742-6596/600/1/012042

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Citations (4)

Deformation method for generalized Abelian Higgs-Chern-Simons models

EPL (Europhysics Letters) (2013)

L. Losano J. M. C. Malbouisson Diego Rubiera-García C. dos Santos

We present an extension of the deformation method applied to self-dual solutions of generalized Abelian Higgs-Chern-Simons models. Starting from a model defined by a potential V (|ϕ|) and a non-canonical kinetic term ω(|ϕ|)|Dμϕ|2 whose analytical domain-wall solutions are known, we show that this method allows to obtain infinitely many new analytic solutions of new models defined by other functions and . We present some examples of deformation functions leading to new families of models and their associated analytic solutions.

Chern–Simons theory

Kinetic term

10.1209/0295-5075/101/31001

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Quantum gravity phenomenology at the dawn of the multi-messenger era -- A review.

arXiv (Cornell University) (2021)

Andrea Addazi J. Álvarez-Muñiz Rafael Alves Batista Giovanni Amelino-Camelia V. Antonelli

The exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give us information about their sources in the universe and the properties of the intergalactic medium. Moreover, multi-messenger astronomy opens up the possibility to search for phenomenological signatures of quantum gravity. On the one hand, the most energetic events allow us to test our physical theories at energy regimes which are not directly accessible in accelerators; on the other hand, tiny effects in the propagation of very high energy particles could be amplified by cosmological distances. After decades of merely theoretical investigations, the possibility of obtaining phenomenological indications of Planck-scale effects is a revolutionary step in the quest for a quantum theory of gravity, but it requires cooperation between different communities of physicists (both theoretical and experimental). This review is aimed at promoting this cooperation by giving a state-of-the art account of the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of cosmic messengers.

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Soliton solutions in relativistic field theories and gravitation

EAS Publications Series (2008)

J. Díaz-Alonso Diego Rubiera-García

We report on some recent results on a class of relativistic lagrangian field theories supporting non-topological soliton solutions and their applications in the contexts of Gravitation and Cosmology. We analyze one and many-components scalar fields and gauge fields.

10.1051/eas:0830024

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Citations (2)

Deforming solitons in generalized Abelian Higgs models

arXiv (Cornell University) (2011)

C. dos Santos Diego Rubiera-García

This work deals with several aspects of the extension to Abelian Higgs models of the deformation method originally developed for scalar field models. We present several examples allowing to transform self-dual solutions of different generalized Abelian Higgs models into scalar field models with or without a gauge field component. This is done through a parametrization of the soliton orbit in terms of the sine-Gordon static kink. We extend these ideas to a nonAbelian Higgs model.

10.48550/arxiv.1111.2173

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What is a singular black hole beyond general relativity?

Physical review. D/Physical review. D. (2017)

Cecilia Bejarano Gonzalo J. Olmo Diego Rubiera-García

Exploring the characterization of singular black hole spacetimes, we study the relation between energy density, curvature invariants, and geodesic completeness using a quadratic $f(R)$ gravity theory coupled to an anisotropic fluid. Working in a metric-affine approach, our models and solutions represent minimal extensions of general relativity (GR) in the sense that they rapidly recover the usual Reissner-Nordstr\"om solution from near the inner horizon outwards. The anisotropic fluid helps modify only the innermost geometry. Depending on the values and signs of two parameters on the gravitational and matter sectors, a breakdown of the correlations between the finiteness/divergence of the energy density, the behavior of curvature invariants, and the (in)completeness of geodesics is obtained. We find a variety of configurations with and without wormholes, a case with a de Sitter interior, solutions that mimic nonlinear models of electrodynamics coupled to GR, and configurations with up to four horizons. Our results raise questions regarding what infinities, if any, a quantum version of these theories should regularize.

Black hole (networking)

Completeness (order theory)

Wormhole

10.1103/physrevd.95.064043

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Citations (72)

Dynamical generation of wormholes with charged fluids in quadratic Palatini gravity

Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology (2014)

Francisco S. N. Lobo Jesús Martínez-Asencio Gonzalo J. Olmo Diego Rubiera-García

The dynamical generation of wormholes within an extension of General Relativity (GR) containing (Planck's scale-suppressed) Ricci-squared terms is considered. The theory is formulated assuming the metric and connection to be independent (Palatini formalism) and is probed using a charged null fluid as a matter source. This has the following effect: starting from Minkowski space, when the flux is active the metric becomes a charged Vaidya-type one, and once the flux is switched off the metric settles down into a static configuration such that far from the Planck scale the geometry is virtually indistinguishable from that of the standard Reissner-Nordstr\"om solution of GR. However, the innermost region undergoes significant changes, as the GR singularity is generically replaced by a wormhole structure. Such a structure becomes completely regular for a certain charge-to-mass ratio. Moreover, the nontrivial topology of the wormhole allows us to define a charge in terms of lines of force trapped in the topology such that the density of lines flowing across the wormhole throat becomes a universal constant. In light of our results, we comment on the physical significance of curvature divergences in this theory and the topology change issue, which support the view that space-time could have a foamlike microstructure pervaded by wormholes generated by quantum gravitational effects.

Wormhole

Planck length

10.1103/physrevd.90.024033

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Citations (28)