28,296 research outputs found
Locally Inertial Reference Frames in Lorentzian and Riemann-Cartan Spacetimes
In this paper we scrutinize the concept of locally inertial reference frames
(LIRF) in Lorentzian and Riemann-Cartan spacetime structures. We present
rigorous mathematical definitions for those objects, something that needs
preliminary a clear mathematical distinction between the concepts of observers,
reference frames, naturally adapted coordinate functions to a given reference
frame and which properties may characterize an inertial reference frame (if
any) in the Lorentzian and Riemann-Cartan structures. We hope to have clarified
some eventual obscure issues associated to the concept of LIRF appearing in the
literature, in particular the relationship between LIRFs in Lorentzian and
Riemann-Cartan spacetimes and Einstein's most happy though, i.e., the
equivalence principle.Comment: In this version a new reference has been added, some misprints and
typos have been corrected and some few sentences in two remarks and in the
conclusions have been changed for better intelligibilit
Quark-hybrid matter in the cores of massive neutron stars
Using a nonlocal extension of the SU(3) Nambu-Jona Lasinio model, which
reproduces several of the key features of Quantum Chromodynamics, we show that
mixed phases of deconfined quarks and confined hadrons (quark-hybrid matter)
may exist in the cores of neutron stars as massive as around 2.1 M_Sun. The
radii of these objects are found to be in the canonical range of
km. According to our study, the transition to pure quark matter does not occur
in stable neutron stars, but is shifted to neutron stars which are unstable
against radial oscillations. The implications of our study for the recently
discovered, massive neutron star PSR J1614-2230, whose gravitational mass is
, are that this neutron star may contain an extended
region of quark-hybrid matter at it center, but no pure quark matter.Comment: 13 pages, 3 figure
Quark deconfinement in high-mass neutron stars
In this paper, we explore whether or not quark deconfinement may occur in
high-mass neutron stars such as J1614-2230 (1.97 \pm 0.04 M_Sun) and J0348+0432
(2.01 \pm 0.04 M_Sun). Our study is based on a non-local extension of the SU(3)
Nambu Jona-Lasinio (n3NJL) model with repulsive vector interactions among the
quarks. This model goes beyond the frequently used local version of the Nambu
Jona-Lasinio (NJL) model by accounting for several key features of QCD which
are not part of the local model. Confined hadronic matter is treated in the
framework of non-linear relativistic mean field theory. We find that both the
local as well as the non-local NJL model predict the existence of extended
regions of mixed quark-hadron (quark-hybrid) matter in high-mass neutron stars
with masses of 2.1 to 2.4 M_Sun. Pure quark matter in the cores of neutron
stars is obtained for certain parametrizations of the hadronic lagrangian and
choices of the vector repulsion among quarks. The radii of high-mass neutron
stars with quark-hybrid matter and/or pure quark matter cores in their centers
are found to lie in the canonical range of 12 to 13 km.Comment: 31 pages, 17 figures, PRC accepted versio
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