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Article
Physics, Multidisciplinary
Miguel Bezares et al.
Summary: We have conducted fully relativistic simulations in a class of scalar-tensor theories with derivative selfinteractions and screening of local scales. Using advanced shock-capturing methods and a nonvanishing shift vector, we have successfully addressed the issues faced by previous attempts. Our findings confirm recent results in spherical symmetry, suggesting a partial breakdown of screening in black hole collapse. Additionally, we have observed that screening tends to suppress dipole scalar emission, but not the dominant quadrupole scalar mode. Our results indicate that quadrupole scalar signals can be as large as, or even larger than, those in Fierz-Jordan-Brans-Dicke theories with the same conformal coupling, within the strong-coupling scales that we can simulate.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Katy Clough et al.
Summary: In this study, we investigated vector fields with self-interactions and found that this modification introduces ghost instabilities similar to those found in vector-tensor theories of modified gravity. We also demonstrated that nonperturbative dynamics cannot prevent these instabilities from occurring.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Andrew Coates et al.
Summary: Even when not coupled to external fields, self-interacting vector field theories can exhibit unphysical behavior, posing a significant challenge to proposals in cosmology, gravity, high energy physics, and other fields. The problem arises when the vector fields reach a critical point where time evolution becomes mathematically ill defined. We have developed tools to easily identify and investigate this issue within a simple and unified framework.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Zong-Gang Mou et al.
Summary: Interacting massive spin-1 fields are widely used in cosmology and particle physics. This study reveals a new condition for the validity of the classical limit of these theories, related to nontrivial constraints on vector field components. Violation of this condition could lead to singularities in time derivatives, impacting the field's cosmic history and properties around black holes.
PHYSICAL REVIEW LETTERS
(2022)
Article
Astronomy & Astrophysics
Mary Gerhardinger et al.
Summary: The Galileon scalar field theory, which exhibits the Vainshtein screening mechanism, has implications for predictions of gravitational waves and tests of gravity. The derivative nature of their interactions poses a challenge in effective field theories but can be overcome through numerical simulations.
Article
Astronomy & Astrophysics
Katsuki Aoki et al.
Summary: This paper discusses the issues of singular effective metric and gradient or ghost instabilities in a self-interacting massive vector field. The research finds that the singularity formation is not necessarily a fundamental problem, but a breakdown of the effective field theory (EFT) description. It is also discovered that the EFT description breaks before the onset of the ghost instability.
Article
Astronomy & Astrophysics
Nicola Franchini et al.
Summary: The formulation of field equations in testing alternative theories of gravity with gravitational-wave data is a major obstacle. The fixing-the-equations approach is a possible solution to control the behavior of solutions and the flow towards ultraviolet modes. In this study, a representative example of scalar-Gauss-Bonnet gravity is used to demonstrate the effectiveness of the fixing-the-equations approach in resolving the dynamical evolutions and connecting with stationary black hole solutions.
Article
Astronomy & Astrophysics
Guillermo Lara et al.
Summary: Researchers explore the ultraviolet completion of k-essence and its dynamic evolution, finding that the completion does not result in any breakdown of the Cauchy problem. However, the nonlinear behavior of k-essence lies mostly outside the range of validity of the low-energy theory.
Article
Physics, Multidisciplinary
Lotte ter Haar et al.
Summary: This study examines gravitational theories that differ from general relativity to explain the accelerated expansion of the Universe without a cosmological constant. The research shows that while these theories are stable under large initial perturbations in isolated static and spherically symmetric stars, they may encounter issues when gravitational collapse is triggered. The characteristic speeds of the scalar evolution equation diverge when collapse occurs, raising doubts about predicting the dynamical evolution of screened stars in these effective field theories.
PHYSICAL REVIEW LETTERS
(2021)
Article
Astronomy & Astrophysics
Miguel Bezares et al.
Summary: The study focuses on the vacuum Cauchy problem for K-essence, a cosmologically relevant scalar-tensor theory. It reveals that there is a large class of theories where no breakdown of the Cauchy problem occurs, except for certain problematic initial data. Solutions for overcoming this issue are proposed.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Miguel Bezares et al.
Summary: The study explores the application of k-essence theory in stellar evolution and gravitational collapse, demonstrating its screening mechanism for scalar fifth forces while highlighting the need for fixing equations to address diverging characteristic speeds in collapsing stars.
Article
Astronomy & Astrophysics
Pau Figueras et al.
CLASSICAL AND QUANTUM GRAVITY
(2020)
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Ramiro Cayuso et al.
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Gwyneth Allwright et al.
CLASSICAL AND QUANTUM GRAVITY
(2019)
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Laura Bernard et al.
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Astronomy & Astrophysics
Justin L. Ripley et al.
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Astronomy & Astrophysics
Norihiro Tanahashi et al.
CLASSICAL AND QUANTUM GRAVITY
(2017)
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Astronomy & Astrophysics
Juan Cayuso et al.
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Astronomy & Astrophysics
Harvey S. Reall et al.
Article
Astronomy & Astrophysics
JM Stewart
CLASSICAL AND QUANTUM GRAVITY
(2001)
