Spontaneous scalarization with an extremely massive field and heavy neutron stars

Understand

We investigate the internal structure and the mass-radius relation of neutron stars in a recently proposed scalar-tensor theory dubbed asymmetron in which a massive scalar field undergoes spontaneous scalarization inside neutron stars.

• We focus on the case where the Compton wavelength is shorter than 10 km, which has not been investigated in the literature.
• By solving the modified Einstein equations, either purely numerically or by partially using a semianalytic method, we find that not only the weakening of gravity by spontaneous scalarization but also the scalar force affect the internal structure significantly in the massive case.
• We also find that the maximum mass of neutron stars is larger for certain parameter sets than that in general relativity and reaches 2 solar mass even if the effect of strange hadrons is taken into account.