Closing a spontaneous-scalarization window with binary pulsars

Zhao, Junjie

Benefitting from the unequaled precision of the pulsar timing technique, binary pulsars are important testbeds of gravity theories, providing some of the tightest bounds on alternative theories of gravity. One class of well-motivated alternative gravity theories, the scalar–tensor gravity, predict large deviations from general relativity for neutron stars through a nonperturbative phenomenon known as spontaneous scalarization. This effect, which cannot be tested in the Solar System, can now be tightly constrained using the latest results from the timing of a set of seven binary pulsars (PSRs J0348+0432, J1012+5307, J1738+0333, J1909−3744, J2222−0137, J0737−3039A, and J1913+1102). Using new timing results, we constrain the neutron star’s effective scalar coupling, which describes how strongly neutron stars couple to the scalar field, to a level of |αA|