Professor THOMAS SOTIRIOU's Outputs (38)

Prospects for fundamental physics with LISA (2020)
Journal Article
Barausse, E., Berti, E., Hertog, T., Hughes, S. A., Jetzer, P., Pani, P., Sotiriou, T. P., Tamanini, N., Witek, H., Yagi, K., Yunes, N., Abdelsalhin, T., Achucarro, A., van Aelst, K., Afshordi, N., Akcay, S., Annulli, L., Arun, K. G., Ayuso, I., Baibhav, V., …Zumalacarregui, M. (2020). Prospects for fundamental physics with LISA. General Relativity and Gravitation, 52(8), Article 81. https://doi.org/10.1007/s10714-020-02691-1

In this paper, which is of programmatic rather than quantitative nature, we aim to further delineate and sharpen the future potential of the LISA mission in the area of fundamental physics. Given the very broad range of topics that might be relevant... Read More about Prospects for fundamental physics with LISA.

Onset of spontaneous scalarization in generalized scalar-tensor theories (2020)
Journal Article
Ventagli, G., Lehébel, A., & Sotiriou, T. P. (2020). Onset of spontaneous scalarization in generalized scalar-tensor theories. Physical Review D, 102(2), Article 024050. https://doi.org/10.1103/PhysRevD.102.024050

In gravity theories that exhibit spontaneous scalarization, astrophysical objects are identical to their general relativistic counterpart until they reach a certain threshold in compactness or curvature. Beyond this threshold, they acquire a nontrivi... Read More about Onset of spontaneous scalarization in generalized scalar-tensor theories.

Dynamical obstruction to perpetual motion from Lorentz-violating black holes (2018)
Journal Article
Benkel, R., Bhattacharyya, J., Louko, J., Mattingly, D., & Sotiriou, T. P. (2018). Dynamical obstruction to perpetual motion from Lorentz-violating black holes. Physical Review D, 98(2), Article 024034. https://doi.org/10.1103/PhysRevD.98.024034

Black holes in Lorentz-violating theories have been claimed to violate the second law of thermodynamics by perpetual motion energy extraction. We revisit this question for a Penrose splitting process in a spherically symmetric setting with two specie... Read More about Dynamical obstruction to perpetual motion from Lorentz-violating black holes.

Spontaneous scalarization of black holes and compact stars from a Gauss-Bonnet coupling (2018)
Journal Article
Silva, H. O., Sakstein, J., Gualtieri, L., Sotiriou, T. P., & Berti, E. (2018). Spontaneous scalarization of black holes and compact stars from a Gauss-Bonnet coupling. Physical Review Letters, 120(13), Article 131104. https://doi.org/10.1103/PhysRevLett.120.131104

We identify a class of scalar-tensor theories with coupling between the scalar and the Gauss-Bonnet invariant that exhibit spontaneous scalarization for both black holes and compact stars. In particular, these theories formally admit all of the stati... Read More about Spontaneous scalarization of black holes and compact stars from a Gauss-Bonnet coupling.

Revisiting the cuscuton as a Lorentz-violating gravity theory (2018)
Journal Article
Bhattacharyya, J., Coates, A., Colombo, M., Gümrükçüoğlu, A. E., & Sotiriou, T. P. (2018). Revisiting the cuscuton as a Lorentz-violating gravity theory. Physical Review D, 97(6), https://doi.org/10.1103/PhysRevD.97.064020

The cuscuton is a scalar field with infinite speed of propagation. It was introduced in the context of cosmology but it has also been claimed to resemble Horava gravity in a certain limit. Here we revisit the cuscuton theory as a Lorentz-violating gr... Read More about Revisiting the cuscuton as a Lorentz-violating gravity theory.

Constructing neutron stars with a gravitational Higgs mechanism (2018)
Journal Article
Franchini, N., Coates, A., & Sotiriou, T. P. (2018). Constructing neutron stars with a gravitational Higgs mechanism. Physical Review D, 97(6), https://doi.org/10.1103/PhysRevD.97.064013

In scalar-tensor theories, spontaneous scalarization is a phase transition that can occur in ultradense environments such as neutron stars. The scalar field develops a non-trivial configuration once the stars exceeds a compactness threshold. We recen... Read More about Constructing neutron stars with a gravitational Higgs mechanism.

Black hole horizons at the extremal limit in Lorentz-violating gravity (2017)
Journal Article
Franchini, N., Saravani, M., & Sotiriou, T. P. (2017). Black hole horizons at the extremal limit in Lorentz-violating gravity. Physical Review D, 96(10), Article 104044. https://doi.org/10.1103/PhysRevD.96.104044

Lorentz-violating gravity theories with a preferred foliation can have instantaneous propagation. Nonetheless, it has been shown that black holes can still exist in such theories and the relevant notion of an event horizon has been dubbed “universal... Read More about Black hole horizons at the extremal limit in Lorentz-violating gravity.

Gravitational Higgs mechanism in neutron star interiors (2017)
Journal Article
Coates, A., Horbatsch, M. W., & Sotiriou, T. P. (2017). Gravitational Higgs mechanism in neutron star interiors. Physical Review D, 95(8), Article 084003. https://doi.org/10.1103/PhysRevD.95.084003

We suggest that nonminimally coupled scalar fields can lead to modifications of the microphysics in the interiors of relativistic stars. As a concrete example, we consider the generation of a non-zero photon mass in such high-density environments. Th... Read More about Gravitational Higgs mechanism in neutron star interiors.

Black hole hair formation in shift-symmetric generalised scalar-tensor gravity (2017)
Journal Article
Benkel, R., Sotiriou, T. P., & Witek, H. (2017). Black hole hair formation in shift-symmetric generalised scalar-tensor gravity. Classical and Quantum Gravity, 34(6), Article 064001. https://doi.org/10.1088/1361-6382/aa5ce7

A linear coupling between a scalar field and the Gauss–Bonnet invariant is the only known interaction term between a scalar and the metric that: respects shift symmetry; does not lead to higher order equations; inevitably introduces black hole hair i... Read More about Black hole hair formation in shift-symmetric generalised scalar-tensor gravity.

Dynamical scalar hair formation around a Schwarzschild black hole (2016)
Journal Article
Benkel, R., Sotiriou, T. P., & Witek, H. (2016). Dynamical scalar hair formation around a Schwarzschild black hole. Physical Review D, 94(12), https://doi.org/10.1103/PhysRevD.94.121503

Scalar fields coupled to the Gauss-Bonnet invariant evade the known no-hair theorems and have nontrivial configurations around black holes. We focus on a scalar field that couples linearly to the Gauss-Bonnet invariant and hence exhibits shift symmet... Read More about Dynamical scalar hair formation around a Schwarzschild black hole.

Causality and black holes in spacetimes with a preferred foliation (2016)
Journal Article
Bhattacharyya, J., Colombo, M., & Sotiriou, T. P. (2016). Causality and black holes in spacetimes with a preferred foliation. Classical and Quantum Gravity, 33(23), Article 235003. https://doi.org/10.1088/0264-9381/33/23/235003

© 2016 IOP Publishing Ltd. We develop a framework that facilitates the study of the causal structure of spacetimes with a causally preferred foliation. Such spacetimes may arise as solutions of Lorentz-violating theories, e.g. Horava gravity. Our fra... Read More about Causality and black holes in spacetimes with a preferred foliation.

Uninvited guest in mixed derivative Hořava gravity (2016)
Journal Article
Coates, A., Colombo, M., Gümrükçüoğlu, A. E., & Sotiriou, T. P. (2016). Uninvited guest in mixed derivative Hořava gravity. Physical Review D, 94(8), Article 84014. https://doi.org/10.1103/PhysRevD.94.084014

We revisit the mixed-derivative extension of Hořava gravity which was designed to address the naturalness problems of the standard theory in the presence of matter couplings. We consider the minimal theory with mixed-derivative terms that contain two... Read More about Uninvited guest in mixed derivative Hořava gravity.

Extrinsic curvature in two-dimensional causal dynamical triangulation (2016)
Journal Article
Glaser, L., Sotiriou, T. P., & Weinfurtner, S. (2016). Extrinsic curvature in two-dimensional causal dynamical triangulation. Physical Review D, 94(6), Article 64014. https://doi.org/10.1103/PhysRevD.94.064014

Causal dynamical triangulation (CDT) is a nonperturbative quantization of general relativity. Hořava-Lifshitz gravity, on the other hand, modifies general relativity to allow for perturbative quantization. Past work has given rise to the speculation... Read More about Extrinsic curvature in two-dimensional causal dynamical triangulation.

Low energy ghosts and the Jeans’ instability (2016)
Journal Article
Gümrükçüoğlu, A. E., Mukohyama, S., & Sotiriou, T. P. (2016). Low energy ghosts and the Jeans’ instability. Physical Review D, 94(6), Article 64001. https://doi.org/10.1103/PhysRevD.94.064001

We show that a massless canonical scalar field minimally coupled to general relativity can become a tachyonic ghost at low energies around a background in which the scalar’s gradient is spacelike. By performing a canonical transformation we demonstra... Read More about Low energy ghosts and the Jeans’ instability.

Evolution and spherical collapse in Einstein-Æther theory and Hořava gravity (2016)
Journal Article
Bhattacharyya, J., Coates, A., Colombo, M., & Sotiriou, T. P. (2016). Evolution and spherical collapse in Einstein-Æther theory and Hořava gravity. Physical Review D, 93(6), Article 64056. https://doi.org/10.1103/PhysRevD.93.064056

We compare the initial value formulation of the low-energy limit of (nonprojectable) Hořava gravity to that of Einstein-æther theory when the æther is assumed to be hypersurface orthogonal at the level of the field equations. This comparison clearly... Read More about Evolution and spherical collapse in Einstein-Æther theory and Hořava gravity.

Slowly rotating black holes in Einstein-æther theory (2016)
Journal Article
Barausse, E., Sotiriou, T. P., & Vega, I. (2016). Slowly rotating black holes in Einstein-æther theory. Physical Review D, 93(4), Article 44044. https://doi.org/10.1103/PhysRevD.93.044044

We study slowly rotating, asymptotically flat black holes in Einstein-æther theory and show that solutions that are free from naked finite area singularities form a two-parameter family. These parameters can be thought of as the mass and angular mome... Read More about Slowly rotating black holes in Einstein-æther theory.

Multipole moments in scalar-tensor theory of gravity (2015)
Journal Article
Pappas, G., & Sotiriou, T. P. (2015). Multipole moments in scalar-tensor theory of gravity. Physical Review D - Particles, Fields, Gravitation and Cosmology, 91, 1-12. https://doi.org/10.1103/PhysRevD.91.044011

Stationary, asymptotically flat spacetimes in general relativity can be characterized by their multipole moments. The moments have proved to be very useful tools for extracting information about the spacetime from various observables and, more recent... Read More about Multipole moments in scalar-tensor theory of gravity.

Black hole hair in generalized scalar-tensor gravity (2014)
Journal Article
Sotiriou, T., & Zhou, S.-Y. (2014). Black hole hair in generalized scalar-tensor gravity. Physical Review Letters, 112(25), Article 251102. https://doi.org/10.1103/PhysRevLett.112.251102

The most general action for a scalar field coupled to gravity that leads to second-order field equations for both the metric and the scalar—Horndeski’s theory—is considered, with the extra assumption that the scalar satisfies shift symmetry. We show... Read More about Black hole hair in generalized scalar-tensor gravity.