Scalarization of neutron stars with realistic equations of state

Abstract

We consider the effect of scalarization on static and slowly rotating neutron stars for a wide variety of realistic equations of state, including pure nuclear matter, nuclear matter with hyperons, hybrid nuclear and quark matter, and pure quark matter. We analyze the onset of scalarization, presenting a universal relation for the critical coupling parameter versus compactness. We find that the onset and the magnitude of the scalarization are strongly correlated with the value of the gravitational potential (the metric component gtt) at the center of the star. We also consider the moment-of-inertia-compactness relations and confirm universality for the nuclear matter, hyperon and hybrid equations of state.

Neutron star structure in the presence of nonminimally coupled scalar fields

“…Damour and Esposito-Farèse [46][47][48][49] discovered the effect of spontaneous scalarization beyond a critical compactness, which, more recently, was reconsidered by the authors of Refs. [50,51]. Spontaneous scalarization as a Higgslike mechanism in which a photon gains mass is studied in Ref.…”

Structure of Neutron Stars in Massive Scalar-Tensor Gravity

“…Numerous studies have demonstrated that spontaneous scalarization features as prominently in rotating NS models, either in the slow-rotation limit [32][33][34][35][36][37], for fast rotation [38,39], or with differential rotation [40]. Spontaneous scalarization has also been found a robust phenomenon under variations of the Equation of state (EOS) [21,36,[41][42][43]. While quantitative differences occur, the phenomenon as such appears to be ubiquitous and also preserve the approximate EOS universality of the relation between the moment of inertia I and the quadrupole moment Q known from GR [33,39] and the inertia vs. compactness universality [36].…”

“…Spontaneous scalarization has also been found a robust phenomenon under variations of the Equation of state (EOS) [21,36,[41][42][43]. While quantitative differences occur, the phenomenon as such appears to be ubiquitous and also preserve the approximate EOS universality of the relation between the moment of inertia I and the quadrupole moment Q known from GR [33,39] and the inertia vs. compactness universality [36].…”

Scalar charges and pulsar-timing observables in the presence of nonminimally coupled scalar fields

“…For the SNMC, (dF/dΦ)| Φ0 ∝ Φ 0 , and so the observed agreement [7] between solar system observations and GR's predictions implies that Φ 0 must be close to zero-but does not limit the viable range of ξ. Interestingly, however, even if Φ 0 = 0, STTs may still differ considerably from GR in their predictions for neutron stars (NS), due to a nonperturbative, strong-field effect known as spontaneous scalarization [8]. This effect, which has long been known to happen for sufficiently negative values of the nonminimal coupling ξ, is characterized by the formation of a scalar cloud that modifies the star's equilibrium * rfpmendes@id.uff.br † tulioottoni@id.uff.br and perturbative properties [9][10][11][12][13], and has dramatic implications, most notably for pulsar-timing observables [14][15][16]. Indeed, the inconsistency between pulsar-timing data and certain aspects of NS phenomenology in STTs, such as the existence of scalar dipole radiation, of scalarfield induced variations in the NS moment of inertia, and so on, can be used to rule out almost the entire range ξ −2.2 of field couplings allowing for spontaneous scalarization (in the case where V (Φ) = 0, which we will refer to as "massless" for simplicity).…”