64 research outputs found
Neutron star solutions in perturbative quadratic gravity
We study the structure of neutron stars in R+\beta\ R^{\mu \nu} R_{\mu \nu}
gravity model with perturbative method. We obtain mass--radius relations for
six representative equations of state (EoSs). We find that, for |\beta| ~ 10^11
cm^2, the results differ substantially from the results of general relativity.
Some of the soft EoSs that are excluded within the framework of general
relativity can be reconciled for certain values of \beta\ of this order with
the 2 solar mass neutron star recently observed. For values of \beta\ greater
than a few 10^11 cm^2 we find a new solution branch allowing highly massive
neutron stars. By referring some recent observational constraints on the
mass--radius relation we try to constrain the value of \beta\ for each EoS. The
associated length scale \sqrt{\beta} ~ 10^6 cm is of the order of the typical
radius of neutron stars implying that this is the smallest value we could find
by using neutron stars as a probe. We thus conclude that the true value of
\beta\ is most likely much smaller than 10^11 cm^2.Comment: 19 pages, 9 figures. v2: Analysis on validity of perturbative
approach is added. References added. v3: Aesthetic improvement
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