https://doi.org/10.1140/epjc/s10052-021-09662-z
Regular Article - Theoretical Physics
Neutron stars in Palatini 
and 
theories
1
Dipartimento di Fisica ’G. Occhialini’, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126, Milan, Italy
2
Institute of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010, Graz, Austria
3
Silicon Austria Labs GmbH, Inffeldgasse 33, 8010, Graz, Austria
Received:
14
June
2021
Accepted:
16
September
2021
Published online:
9
October
2021
We study solutions of the stellar structure equations for spherically symmetric objects in modified theories of gravity, where the Einstein-Hilbert Lagrangian is replaced by 
and 
, with R being the Ricci scalar curvature, 
and 
the Ricci tensor. We work in the Palatini formalism, where the metric and the connection are assumed to be independent dynamical variables. We focus on stellar solutions in the mass-radius region associated to neutron stars. We illustrate the potential impact of the 
and Q terms by studying a range of viable values of 
and 
. Similarly, we use different equations of state (SLy, FPS, HS(DD2) and HS(TMA)) as a simple way to account for the equation of state uncertainty. Our results show that for certain combinations of the and parameters and equation of state, the effect of modifications of general relativity on the properties of stars is sizeable. Therefore, with increasing accuracy in the determination of the equation of state for neutron stars, astrophysical observations may serve as discriminators of modifications of General Relativity.
© The Author(s) 2021
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Funded by SCOAP3
