Abstract
AbstractMotivated by constant-G theory, we introduce a one-parameter family of scalar–tensor theories as an extension of constant-G theory in which the conformal symmetry is a cosmological attractor. Since the model has the coupling function of negative curvature, we expect spontaneous scalarization to occur and that the parameter can be constrained by pulsar timing measurements. Modeling neutron stars with realistic equations of state, we study the structure of neutron stars and calculate the effective scalar coupling with the neutron star in these theories. We find that within the parameter region where the observational constraints are satisfied, the effective scalar coupling almost coincides with that derived using the quadratic model with the same curvature. This indicates that the constraints obtained by the quadratic model will be used to limit the curvature of the coupling function universally in the future.
Highlights
The equivalence principle played the principal role in constructing general relativity (GR) by Einstein
We find that spontaneous scalarization occurs if p 2.2 and p is constrained as p < 2.3 irrespective of equation of state (EOS). 9 more detailed constraints on p depend on the EOS: p is constrained to be p < 2.2 for APR4 and H4, while p = 2.2 is allowed for MS1
Motivated by constant-G theory which respects the strong equivalence principle (SEP) and is cosmologically attracted toward the conformal symmetry, we introduce a one-parameter family of scalar-tensor theories which exhibit cosmological attraction toward the conformal symmetry
Summary
The equivalence principle played the principal role in constructing general relativity (GR) by Einstein. In general scalar-tensor theories of gravity [1,2,3], the equation of motion of a self-gravitating massive body (at the first post-Newtonian approximation) depends on the inertial mass mI and the (passive) gravitational mass mG of the body. The equation of motion of a massive body is given in [4, 8] It contains terms which depend on the gravitational self-energy, the coefficient of which is η = 4β − γ − 3.
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