Spontaneous scalarization of charged stars

Masato Minamitsuji, Shinji Tsujikawa*


研究成果: Article査読

1 被引用数 (Scopus)


We study static and spherically symmetric charged stars with a nontrivial profile of the scalar field ϕ in Einstein-Maxwell-scalar theories. The scalar field is coupled to a U(1) gauge field Aμ with the form −α(ϕ)FμνFμν/4, where Fμν=∂μAν−∂νAμ is the field strength tensor. Analogous to the case of charged black holes, we show that this type of interaction can induce spontaneous scalarization of charged stars under the conditions (dα/dϕ)(0)=0 and (d2α/dϕ2)(0)>0. For the coupling α(ϕ)=exp⁡(−βϕ2/Mpl2), where β(<0) is a coupling constant and Mpl is a reduced Planck mass, there is a branch of charged star solutions with a nontrivial profile of ϕ approaching 0 toward spatial infinity, besides a branch of general relativistic solutions with a vanishing scalar field, i.e., solutions in the Einstein-Maxwell model. As the ratio ρcm between charge density ρc and matter density ρm increases toward its maximum value, the mass M of charged stars in general relativity tends to be enhanced due to the increase of repulsive Coulomb force against gravity. In this regime, the appearance of nontrivial branches induced by negative β of order −1 effectively reduces the Coulomb force for a wide range of central matter densities, leading to charged stars with smaller masses and radii in comparison to those in the general relativistic branch. Our analysis indicates that spontaneous scalarization of stars can be induced not only by the coupling to curvature invariants but also by the scalar-gauge coupling in Einstein gravity.

ジャーナルPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
出版ステータスPublished - 2021 9月 10

ASJC Scopus subject areas

  • 核物理学および高エネルギー物理学


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