Erratum: Spontaneous scalarization in generalized scalar-tensor theory [Phys. Rev. D 
<b>99</b>
, 124022 (2019)]

Andreou, Nikolas; Franchini, Nicola; Ventagli, Giulia; Sotiriou, Thomas P.

doi:10.1103/physrevd.101.109903

Cited by 36 publications

(9 citation statements)

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“…The Lagrangian of the full model consists in the usual Einstein term for gravity and kinetic term for the scalar field, together with the interaction term (12) or (14).…”

Section: The Bh Solutionsmentioning

confidence: 99%

“…Further work includes the study of scalarized BHs in various extensions of the initial framework [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] and the investigation of solutions' stability [25][26][27][28]; furthermore, partial analytical results are reported in Refs. [29][30][31][32], while scalarized, rotating BHs are studied in [33][34][35][36][37][38][39].…”

Section: Introductionmentioning

confidence: 99%

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Embedding Gauss–Bonnet Scalarization Models in Higher Dimensional Topological Theories

2021

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In the presence of appropriate non-minimal couplings between a scalar field and the curvature squared Gauss–Bonnet (GB) term, compact objects such as neutron stars and black holes (BHs) can spontaneously scalarize, becoming a preferred vacuum. Such strong gravity phase transitions have attracted considerable attention recently. The non-minimal coupling functions that allow this mechanism are, however, always postulated ad hoc. Here, we point out that families of such functions naturally emerge in the context of Higgs–Chern–Simons gravity models, which are found as dimensionally descents of higher dimensional, purely topological, Chern–Pontryagin non-Abelian densities. As a proof of concept, we study spherically symmetric scalarized BH solutions in a particular Einstein-GB-scalar field model, whose coupling is obtained from this construction, pointing out novel features and caveats thereof. The possibility of vectorization is also discussed, since this construction also originates vector fields non-minimally coupled to the GB invariant.

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“…The Lagrangian of the full model consists in the usual Einstein term for gravity and kinetic term for the scalar field, together with the interaction term (12) or (14).…”

Section: The Bh Solutionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Embedding Gauss–Bonnet Scalarization Models in Higher Dimensional Topological Theories

2021

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“…In this scenario, the study of NSs is especially important, because since the first work on massless mono-scalar STTs (Damour & Esposito-Farèse 1993), a non-perturbative strong field effect has been predicted, allowing the scalar field to exponentially grow in magnitude inside compact material objects. Even generalisations of STTs to massive scalar fields and other gravitational theories have been shown to be subject to a similar phenomenon (Salgado et al 1998;Ramazanoglu & Pretorius 2016;Ramazanoglu 2017;Silva et al 2018;Andreou et al 2019). Scalarisation can happen in various contexts: binary systems of merging NSs can undergo a "dynamical scalarisation" process (Barausse et al 2013), in which the initially non-scalarised NSs become scalarised once they get closer to each other; again, in a binary NS system, one scalarised star can prompt an "induced scalarisation" on its non-scalarised companion (Barausse et al 2013); or even in an isolated NS system, where "spontaneous scalarisation" can develop (this was the first discovered non-perturbative strong field effect in STTs, Damour & Esposito-Farèse 1993).…”

Section: Introductionmentioning

confidence: 99%

Axisymmetric equilibrium models for magnetised neutron stars in scalar-tensor theories

Soldateschi

Bucciantini

Zanna

2020

A&A

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Among the possible extensions of general relativity that have been put forward to address some long-standing issues in our understanding of the Universe, scalar-tensor theories have received a lot of attention for their simplicity. Interestingly, some of these predict a potentially observable non-linear phenomenon, known as spontaneous scalarisation, in the presence of highly compact matter distributions, as in the case of neutron stars. Neutron stars are ideal laboratories for investigating the properties of matter under extreme conditions and, in particular, they are known to harbour the strongest magnetic fields in the Universe. Here, for the first time, we present a detailed study of magnetised neutron stars in scalar-tensor theories. First, we showed that the formalism developed for the study of magnetised neutron stars in general relativity, based on the “extended conformally flat condition”, can easily be extended in the presence of a non-minimally coupled scalar field, retaining many of its numerical advantages. We then carried out a study of the parameter space considering the two extreme geometries of purely toroidal and purely poloidal magnetic fields, varying both the strength of the magnetic field and the intensity of scalarisation. We compared our results with magnetised general-relativistic solutions and un-magnetised scalarised solutions, showing how the mutual interplay between magnetic and scalar fields affect the magnetic and the scalarisation properties of neutron stars. In particular, we focus our discussion on magnetic deformability, maximum mass, and range of scalarisation.

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“…Even if spontaneous scalarisation in the simplest versions of STTs (i.e. massless ones) have been almost completely ruled out by measurements in binary pulsar systems Shao et al 2017;Voisin et al 2020), this phenomenon remains worth investigating: first, because it cannot be ruled out for massive fields or fields with screening potentials (Ramazanoglu & Pretorius 2016;Yazadjiev et al 2016;Staykov et al 2018;Xu et al 2020;Rosca-Mead et al 2020); second, because it is the prototype of other kinds of scalarisation (Salgado et al 1998;Barausse et al 2013;Ramazanoglu & Pretorius 2016;Ramazanoǧlu 2017;Silva et al 2018;Andreou et al 2019); third, because multi-dimensional and/or time dependent numerical algorithms developed in GR can easily be extended to handle STTs (Novak 1998;Shibata et al 2014;Gerosa et al 2016;Soldateschi et al 2020), which cannot be said of virtually all other GR alternatives. Unfortunately, part of the phenomenology of STTs is degenerate with the EoS of NSs, for example regarding their mass-radius relation or deformabilities.…”

Section: Introductionmentioning

confidence: 99%

Quasi-universality of the magnetic deformation of neutron stars in general relativity and beyond

Soldateschi,

Bucciantini,

Del Zanna

2021

Preprint

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Neutron stars are known to host extremely powerful magnetic fields. Among other effects, one of the consequences of harbouring such fields is the deformation of the neutron star structure, leading, together with rotation, to the emission of continuous gravitational waves. On the one hand, the details of their internal magnetic fields are mostly unknown. Likewise, their internal structure, encoded by the equation of state, is highly uncertain. Here we present a study of axisymmetric models of isolated magnetised neutron stars, for various realistic equations of state considered viable by observations and nuclear physics constraints. We show that it is possible to find simple relations between the magnetic deformation of a neutron star, its Komar mass and its circumferential radius. Such relations are quasi-universal, meaning that they are mostly independent on the equation of state of the neutron star and only slightly dependent on the magnetic field configuration. Being formulated in terms of potentially observable quantities, as we discuss, our results could help to constrain the magnetic properties of the neutron star interior and to better assess the detectability of continuous gravitational waves by isolated neutron stars, without knowing their equation of state. Our results are derived both in general relativity and in scalar-tensor theories -one of the most promising extensions of general relativity -in this case by considering also the scalar charge. We show that even in this case general relations hold that account for deviations from general relativity, that could potentially be used to set constraints on the gravitational theory.

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Erratum: Spontaneous scalarization in generalized scalar-tensor theory [Phys. Rev. D 99 , 124022 (2019)]

Cited by 36 publications

References 0 publications

Embedding Gauss–Bonnet Scalarization Models in Higher Dimensional Topological Theories

Embedding Gauss–Bonnet Scalarization Models in Higher Dimensional Topological Theories

Axisymmetric equilibrium models for magnetised neutron stars in scalar-tensor theories

Quasi-universality of the magnetic deformation of neutron stars in general relativity and beyond

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