It is anticipated that the gravitational radiation detected in future gravitational wave (GW) detectors from binary neutron star (NS) mergers can probe the high density equation of state (EOS). We perform the first simulations of binary NS mergers which adopt various parameterizations of the quark-hadron crossover (QHC) EOS. These are constructed from combinations of a hadronic EOS (n b < 2 n 0 ) and a quark-matter EOS (n b > 5 n 0 ), where n b and n 0 are the baryon number density and the nuclear saturation density, respectively. At the crossover densities (2 n 0 < n b < 5 n 0 ) the QHC EOSs continuously soften, while remaining stiffer than hadronic and first-order phase transition EOSs, achieving the stiffness of the strongly correlated quark matter. This enhanced stiffness leads to significantly longer lifetimes of the postmerger NS than that for a pure hadronic EOS. We find a dual nature of these EOSs such that their maximum chirp GW frequencies f max fall into the category of a soft EOS while the dominant peak frequencies ( f peak ) of the postmerger stage falls in between that of a soft and stiff hadronic EOS. An observation of this kind of dual nature in the characteristic GW frequencies will provide crucial evidence for the existence of strongly interacting quark matter at the crossover densities for QCD.
It is anticipated that the gravitational radiation detected in future gravitational wave (GW) detectors from binary neutron star (NS) mergers can probe the high density equation of state (EOS). We simulate binary NS mergers which adopt various quark-hadron crossover (QHC) EOSs which are constructed from combinations of a hardronic EOS (n b < 2 n 0 ) and a quark-matter EOS (n b > 5 n 0 ), where n b and n 0 are the baryon number density and the nuclear saturation density, respectively. At the crossover densities (2 n 0 < n b < 5 n 0 ), the QHC EOSs have a gradually increasing stiffness reaching to the stiffness of the strongly correlated quark matter. This enhanced stiffness leads to much longer lifetimes of the hypermassive NS than that for a pure hadronic EOS. We find a dual nature of these EOSs such that their maximum chirp GW frequencies f max fall into the category of a soft EOS while the dominant peak frequencies ( f peak ) of the postmerger stage falls in between that of a soft and stiff hadronic EOSs. An observation of this kind of dual nature in the characteristic GW frequencies will provide crucial evidence for the existence of strongly interacting quark matter at the crossover densities for QCD.
No abstract
The abundance of primordial lithium is derived from the observed spectroscopy of metal-poor stars in the galactic halo. However, the observationally inferred abundance remains at about a factor of three below the abundance predicted by standard big bang nucleosynthesis (BBN). The resolution of this dilemma can be either astrophysical (stars destroy lithium after BBN), nuclear (reactions destroy lithium during BBN), or cosmological, i.e. new physics beyond the standard BBN is responsible for destroying lithium. Here, we overview a variety of possible cosmological solutions, and their shortcomings. On the one hand, we examine the possibility of physical processes that modify the velocity distribution of particles from the usually assumed Maxwell-Boltzmann statistics. A physical justification for this is an inhomogeneous spatial distribution of domains of primordial magnetic field strength as a means to reduce the primordial lithium abundance. Another possibility is that scattering with the mildly relativistic electrons in the background plasma alters the baryon distribution to one resembling a Fermi-Dirac distribution. We show that neither of these possibilities can adequately resolve the lithium problem. A number of alternate hybrid models are discussed including a mix of neutrino degeneracy, unified dark matter, axion cooling, and the presence of decaying and/or charged supersymmetric particles.
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