Ghost of vector fields in compact stars

Silva, Hector O.; Coates, Andrew; Ramazanoğlu, Fethi M.; Sotiriou, Thomas P.

doi:10.1103/physrevd.105.024046

Cited by 34 publications

(30 citation statements)

References 93 publications

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“…Recent work on vectorization, i.e., the spontaneous growth of vector fields in vector-tensor modified gravity models has uncovered ghost type instabilities which occur when there is a change in the signature of the effective metric for the scalar mode of the Proca field [20][21][22]. In such theories, the instability is triggered by non-minimally coupled vector perturbations, and is closely related to the presence of a potential tachyonic mode.…”

Section: Introductionmentioning

confidence: 99%

The problem with Proca: ghost instabilities in self-interacting vector fields

Clough¹,

Helfer²,

Witek³

et al. 2022

Preprint

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Massive vector fields feature in several areas of particle physics, e.g., as carriers of weak interactions, dark matter candidates, or as an effective description of photons in a plasma. Here we investigate vector fields with self-interactions by replacing the mass term in the Proca equation with a general potential. We show that this seemingly benign modification inevitably introduces ghost instabilities of the same kind as those recently identified for vector-tensor theories of modified gravity (but in this simpler, minimally coupled theory). It has been suggested that nonperturbative dynamics may drive systems away from such instabilities. We demonstrate that this is not the case by evolving a self-interacting Proca field on a black hole background, where it grows due to the superradiant instability. The system initially evolves as in the massive case, but instabilities are triggered in a finite time once the self-interaction becomes significant. These instabilities have implications for the formation of condensates of massive, self-interacting vector bosons, the possibility of spin-one bosenovae, vector dark matter models, and effective models for interacting photons in a plasma.

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Section: Introductionmentioning

confidence: 99%

The problem with Proca: ghost instabilities in self-interacting vector fields

Clough¹,

Helfer²,

Witek³

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…Since the branch of vectorized solutions is disconnected from the GR branch, spontaneous vectorization would not proceed as a continuous evolution from a GR solution. Indeed, in GR solutions the scalar mode suffers from ghost instabilities, rather than tachyonic ones [28,30,31]. A similar problem has also been pointed out for the models of spontaneous spinorization [31].…”

Section: Introductionmentioning

confidence: 61%

“…Indeed, in GR solutions the scalar mode suffers from ghost instabilities, rather than tachyonic ones [28,30,31]. A similar problem has also been pointed out for the models of spontaneous spinorization [31]. One important lesson from such models is that for a successful higher-spin extension of spontaneous scalarization the gravitational theory should, on top of having GR solutions, not contain any extra scalar modes.…”

Section: Introductionmentioning

confidence: 80%

Static and spherically symmetric general relativity solutions in Minimal Theory of Bigravity

Minamitsuji,

De Felice,

Mukohyama

et al. 2022

Preprint

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We investigate static and spherically symmetric solutions in the Minimal Theory of Bigravity (MTBG). First, we show that a pair of Schwarzschild-de Sitter spacetimes with different cosmological constants and black hole masses written in the spatially-flat Gullstrand-Painlevé (GP) coordinates is a solution in the self-accelerating branch of MTBG, while it cannot be a solution in the normal branch. We then illustrate how Schwarzschild-de Sitter solutions can become compatible with the normal branch when using different coordinates. We also confirm that the self-accelerating branch of MTBG admits static and spherically symmetric general relativity solutions with matter written in the spatially-flat coordinates, including neutron stars with arbitrary matter equations of state. Finally, we show that in the self-accelerating branch nontrivial solutions are given by the Schwarzschild-de Sitter metrics written in nonstandard coordinates.

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“…Whether this indeed can occur for vector fields is an important issue because a tachyonic destabilization is a possible mechanism to generate compact astrophysical objects with vector hair starting from a hairless initial state-a phenomenon known as vectorization [79][80][81][82]. The no-go result of [38], together with the more general analyses in [83,84], cast doubt on vectorization as a viable mechanism, as they showed that localized perturbations must be either stable or else grow through wrong-sign kinetic or gradient operators. Our present results further supplement this claim by demonstrating that global bound-state solutions on a Schwarzschild BH background likewise do not exhibit tachyonic growth.…”

Section: Discussionmentioning

confidence: 99%

Schwarzschild quasi-normal modes of non-minimally coupled vector fields

Garcia-Saenz,

Held,

Zhang

2022

Preprint

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We study perturbations of massive and massless vector fields on a Schwarzschild black-hole background, including a non-minimal coupling between the vector field and the curvature. The coupling is given by the Horndeski vector-tensor operator, which we show to be unique, also when the field is massive, provided that the vector has a vanishing background value.We determine the quasi-normal mode spectrum of the vector field, focusing on the fundamental mode of monopolar and dipolar perturbations of both even and odd parity, as a function of the mass of the field and the coupling constant controlling the non-minimal interaction. In the massless case, we also provide results for the first two overtones, showing in particular that the isospectrality between even and odd modes is broken by the nonminimal gravitational coupling.We also consider solutions to the mode equations corresponding to quasi-bound states and static configurations. Our results for quasi-bound states provide strong evidence for the stability of the spectrum, indicating the impossibility of a vectorization mechanism within our set-up. For static solutions, we analytically and numerically derive results for the electromagnetic susceptibilities (the spin-1 analogs of the tidal Love numbers), which we show to be non-zero in the presence of the non-minimal coupling.

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Ghost of vector fields in compact stars

Cited by 34 publications

References 93 publications

The problem with Proca: ghost instabilities in self-interacting vector fields

The problem with Proca: ghost instabilities in self-interacting vector fields

Static and spherically symmetric general relativity solutions in Minimal Theory of Bigravity

Schwarzschild quasi-normal modes of non-minimally coupled vector fields

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