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Quark matter in light neutron stars

Authors: Ferreira, M; Pereira, RC; Providencia, C

Ref.: Phys. Rev. D 102(8), 083030 (2020)

Abstract: Higher-order repulsive interactions are included in the three-flavor Nambu–Jona-Lasinio model in order to describe the quark phase of an hybrid star. The effect of 4-quark and 8-quark vector-isoscalar interactions in the stability of hybrid star configurations is analyzed. The presence of a 8-quark vector-isoscalar channel is seen to be crucial in generating large quark branches in the M(R) diagram. This is due to its stiffening effect on the quark matter equation of state which arises from the nonlinear density dependence of the speed of sound. This additional interaction channel allows for the appearance of a quark core at moderately low NS masses, ∼1  M⊙, and provides the required repulsion to preserve the star stability up to ∼2.1  M⊙. Furthermore, we show that both the heaviest NS mass generated, Mmax, and its radius, Rmax, are quite sensitive to the strength of 8-quark vector-isoscalar channel, leading to a considerable decrease of Rmax as the coupling increases. This behavior imprints a considerable deviation from the purely hadronic matter equation of state in the Λ(M) diagram, which might be a possible signature of the quark matter existence, even for moderately low NS masses, ∼1.4  M⊙. The resulting M(R) and Λ(R) relations are in accordance with the latest astrophysical constraints from NICER and LIGO/Virgo observations, respectively.

DOI: 10.1103/PhysRevD.102.083030

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