Effects of fermionic dark matter on properties of neutron stars

Abstract

By assuming that only gravitation exists between dark matter (DM) and normal matter (NM), we study the effects of fermionic DM on the properties of neutron stars using the two-fluid Tolman-Oppenheimer-Volkoff formalism. It is found that the mass-radius relationship of the DM admixed neutron stars (DANSs) depends sensitively on the mass of DM candidates, the amount of DM, and interactions among DM candidates. The existence of DM in DANSs results in a spread of mass-radius relationships that cannot be interpreted with a unique equilibrium sequence. In some cases, the DM distribution can surpass the NM distribution to form DM halo. In particular, it is favorable to form an explicit DM halo, provided the repulsion of DM exists. It is interesting to find that the difference in particle number density distributions in DANSs and consequently in star radii caused by various density dependencies of nuclear symmetry energy tends to disappear as long as the repulsion of accumulated DM is sufficient. These phenomena indicate that the admixture of DM in neutron stars can significantly affect the astrophysical extraction of nuclear equation of state by virtue of neutron star measurements. In addition, the effect of the DM admixture on the star maximum mass is also investigated.Comment: to be published in Phys. Rev. C (2014

Compact bifluid hybrid stars: hadronic matter mixed with self-interacting fermionic asymmetric dark matter

“…Since dark matter interacts with normal baryonic matter through gravity, it is quite possible for white dwarfs and neutron stars to accrete dark matter and evolve to a dark matter admixed compact star [12,15,17,[21][22][23][24][25][26]. The large baryonic density in compact stars increases the probability of dark matter capture within the star and eventually results in gravitational trapping.…”

Quantum force estimation in arbitrary non-Markovian Gaussian baths

“…We are now able to derive an expression of the QFI thanks to results from [28] and expressions for fidelity between Gaussian states [32]. One can also use the derivations in [33][34][35] which are applications of the results in [28] to Gaussian states. As expected, all these expressions of the QFI for Gaussian states are functions of the first and second moment of the quadrature operators.…”

“…Efforts have been made to find alternatives [28][29][30][31], but they are still hard to apply for arbitrary dynamics and states. We restrict ourselves to Gaussian states which are more easily accessible experimentally and for which [33][34][35] have derived explicit expressions of the QFI. As we will see in the following, this important assumption also guarantees that the best measurement is a quadrature measurement and that the maximum likelihood estimator is efficient implying that the quantum Cramer-Rao bound Eq.…”

Fusion reactions of58,64Ni+124Sn

“…The results clearly show that large values ofhω (corresponding to thin barriers and then in favour to a fusion enhancement) are always associated with positive Q values for neutron transfer, in both medium (Ca+Ca, Si+Ni, Ni+Ni) and heavy systems (Ca+Zr, Ca+Sn, Ni+Sn). In particular, excitation functions have a shallower slope for systems where a neutron-poor projectile collides on a neutron-rich target [14].…”

“…Two recent publications, concerning the influence of transfer in the fusion process, came to different conclusions. In the first one [13], where the excitation function of 58 Ni+ 132 Sn could only be measured down to the 0.1-1 mb region due to the low intensity of the secondary 132 Sn beam, it was claimed that the influence of transfer for Ni+Sn is negligible compared to lighter systems; in the other one [14] it was concluded that the fusion enhancement due to transfer couplings should be present in heavier systems as well.…”