Person:
Blázquez Salcedo, José Luis

First Name

José Luis

Last Name

Blázquez Salcedo

URI

https://hdl.handle.net/20.500.14352/75158

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Físicas

Department

Física Teórica

Area

Física Teórica

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Now showing 1 - 10 of 28

Angular momentum – area – proportionality of extremal charged black holes in odd dimensions
(Physics Letters B, 2013) Blázquez Salcedo, José Luis; Kunz, Jutta; Navarro Lerida, Francisco
Extremal rotating cohomogeneity-1 black holes in Einstein-Maxwell theory feature two branches. On the branch emerging from the Myers-Perry solutions their angular momentum is proportional to their horizon area, while on the branch emerging from the Tangherlini solutions their angular momentum is proportional to their horizon angular momentum. The transition between these branches occurs at a critical value of the charge, which depends on the value of the angular momentum. However, when a dilaton is included, the angular momentum is always proportional to the horizon area.
Remarks on the Taub-NUT solution in Chern–Simons modified gravity
(Physics letters B, 2017) Blázquez Salcedo, José Luis; Kunz, Jutta; Navarro Lerida, Francisco; Radu, Eugen
We construct a generalization of the AdS charged rotating black holes with two equal magnitude angular momenta in five-dimensional minimal gauged supergravity. In addition to the mass, electric charge and angular momentum, the new solutions possess an extra-parameter associated with a non-zero magnitude of the magnetic potential at infinity. In contrast with the known cases, these new black holes possess a non-trivial zero-horizon size limit which describes a one parameter family of spinning charged solitons. All configurations reported in this work approach asymptotically an AdS(5) spacetime in global coordinates and are free of pathologies.
Probing the Ellis-Bronnikov wormhole geometry with a scalar field: clouds, waves and Q-balls
(Physics letters B, 2022) Blázquez Salcedo, José Luis; Dariescu, Marina Aura; Dariescu, Ciprian; Radu, Eugen; Stelea, Cristian
The Ellis-Bronnikov solution provides a simple toy model for the study of various aspects of wormhole physics. In this work we solve the Klein-Gordon equation in this background and find an exact solution in terms of Heun's function. This may describe 'scalar clouds' (i.e. localized, particle-like configuration) or scalar waves. However, in the former case, the radial derivative of the scalar field is discontinuous at the wormhole's throat (except for the spherical case). This pathology is absent for a suitable scalar field self-interaction, and we provide evidence for the existence of spherically symmetric and spinning Q-balls in a Ellis-Bronnikov wormhole background.
Perturbed black holes in Einstein-dilaton-Gauss-Bonnet gravity: stability, ringdown, and gravitational-wave emission
(Physical Review D, 2016) Blázquez Salcedo, José Luis; Macedo, Caio F.B.; Cardoso, Vitor; Ferrari, Valeria; Gualtieri, Leonardo; Khoo, Fech Scen; Kunz, Jutta; Pani, Paolo
Gravitational waves emitted by distorted black holes-such as those arising from the coalescence of two neutron stars or black holes-carry not only information about the corresponding spacetime but also about the underlying theory of gravity. Although general relativity remains the simplest, most elegant, and viable theory of gravitation, there are generic and robust arguments indicating that it is not the ultimate description of the gravitational universe. Here, we focus on a particularly appealing extension of general relativity, which corrects Einstein's theory through the addition of terms which are second order in curvature: the topological Gauss-Bonnet invariant coupled to a dilaton. We study gravitational-wave emission from black holes in this theory and (i) find strong evidence that black holes are linearly (mode) stable against both axial and polar perturbations, (ii) discuss how the quasinormal modes of black holes can be excited during collisions involving black holes, and finally (iii) show that future ringdown detections with a large signal-to-noise ratio would improve current constraints on the coupling parameter of the theory.
New model of relativistic slowly rotating neutron star with surface layer crust: application to giant glitches of Vela Pulsar
(Journal of physics: Conference series, 2011) González Recio, José Luis; Blázquez Salcedo, José Luis
Introducing a surface layer of matter on the edge of a neutron star in slow rigid rotation, we analyze, from an intrinsic point of view, the junction conditions that must be satisfied between the interior and exterior solutions of the Einstein equations. In our model the corecrust transition pressure arise as an essential parameter in the description of a configuration. As an application of this formalism, we describe giant glitches of the Vela pulsar as a result of variations in the transition pressure, finding that these small changes are compatible with the expected temperature variations of the inner crust during glitch time
Compact Objects in Alternative Gravities
(Universe, 2022) Blázquez Salcedo, José Luis; Kleihaus, Burkhard; Kunz, Jutta
We address neutron stars and black holes in alternative gravities, after recalling their basic properties in General Relativity. Among the plethora of interesting alternative gravities we here focus on an interesting set of scalar-tensor theories. We discuss the phenomenon of spontaneous scalarization, that is, matter induced for neutron stars and curvature induced for black holes. Along with other relevant physical properties, we address the quasi-normal modes of these compact objects. In particular, we consider universal relations of neutron stars to largely reduce the dependence on the equation of state, and we briefly address the shadow of black holes.
Polar modes and isospectrality of Ellis-Bronnikov wormholes
(Physical review D, 2023) Azad, Bahareh; Blázquez Salcedo, José Luis; Chew, Xiao Yan; Kunz, Jutta; Yeom, Dong-han
We consider polar perturbations of static Ellis-Bronnikov wormholes and derive the coupled set of perturbation equations for the gravitational and the scalar field. For massless wormholes the perturbations decouple, and we obtain two identical master equations for the scalar and gravitational modes, which moreover agree with the master equation for the axial modes. Consequently there is isospectrality with threefold degenerate modes. For a finite mass of the background wormhole solutions, the equations are coupled. We then obtain two distinct branches of polar quasinormal modes for a given multipole number l, associated with the presence of the two types of fields. We calculate the quasinormal mode frequencies and decay rates for the branches with l = 2, 3 and 4. For a given l the real frequencies of the two branches get the closer, the higher the multipole number gets.
Traversable wormholes in Einstein-Dirac-Maxwell theory
(Physical Review Letters, 2021) Blázquez Salcedo, José Luis; Knoll, Christian; Radu, Eugen
We construct a specific example of a class of traversable wormholes in Einstein-Dirac-Maxwell theory in four spacetime dimensions, without needing any form of exotic matter. Restricting to a model with two massive fermions in a singlet spinor state, we show the existence of spherically symmetric asymptotically flat configurations which are free of singularities, representing localized states. These solutions satisfy a generalized Smarr relation, being connected with the extremal Reissner-Nordström black holes. They also possess a finite mass M and electric charge Q_e, with Q_e/M > 1. An exact wormhole solution with ungauged, massless fermions is also reported.
Are slowly rotating Ellis-Bronnikov wormholes stable?
(Physics Letters B, 2024) Azad, Bahareh; Blázquez Salcedo, José Luis; Khoo, Fech Scen; Kunz, Jutta
We investigate the radial perturbations of Ellis-Bronnikov wormholes (l = 0) in a slowly rotating background expanded up to second order in rotation. We find indications that simple wormhole solutions such as Ellis-Bronnikov in General Relativity can be stabilized by rotation, thus favoring a viable traversable wormhole. This opens up the intriguing question whether the many other wormhole solutions with or without the support of exotic matter can become linearly mode stable when the wormhole rotates.
Squashed, magnetized black holes in D=5 minimal gauged supergravity
(Journal of high energy physics, 2018) Blázquez Salcedo, José Luis; Kunz, Jutta; Navarro Lerida, Francisco; Radu, Eugen
We construct a new class of black hole solutions in five-dimensional Einstein-Maxwell-Chern-Simons theory with a negative cosmological constant. These configurations are cohomogeneity-1, with two equal-magnitude angular momenta. In the generic case, they possess a non-vanishing magnetic potential at infinity with a boundary metric which is the product of time and a squashed three-dimensional sphere. Both extremal and non-extremal black holes are studied. The non-extremal black holes satisfying a certain relation between electric charge, angular momenta and magnitude of the magnetic potential at infinity do not trivialize in the limit of vanishing event horizon size, becoming particle-like (non-topological) solitonic configurations. Among the extremal black holes, we show the existence of a new one-parameter family of supersymmetric solutions, which bifurcate from a critical Gutowski-Reall configuration.