Impact of New Conformal Coupling on Spontaneous Scalarization of Neutron Stars

The scalar-tensor gravity as one of the alternative theories of general relativity has some interesting features. In the case of compact objects it predicts a unique phenomenon which is known as spontaneous scalarization, as shown by Damour and Espasito-Farese [1]. This phenomenon does not appear within the general relativity. In this note, we investigate a new conformal coupling function i.e., A(φ) = 1 − ln[1 − 0.5β(φ − φ ₀)²] and its consequences in neutron stars. In the case of a polytropic equation of state, we have found that the spontaneous scalarization starts to appear when β_c ≈ −4.35. We also found that for the realistic equation of states the β_c depends on the composition and the stiffness of the equation of state. (paper)