521 research outputs found
Mixed quark-nucleon phase in neutron stars and nuclear symmetry energy
The influence of the nuclear symmetry energy on the formation of a mixed
quark-nucleon phase in neutron star cores is studied. We use simple
parametrizations of the nuclear matter equation of state, and the bag model for
the quark phase. The behavior of nucleon matter isobars, which is responsible
for the existence of the mixed phase, is investigated. The role of the nuclear
symmetry energy changes with the value of the bag constant B. For lower values
of B the properties of the mixed phase do not depend strongly on the symmetry
energy. For larger B we find that a critical pressure for the first quark
droplets to form is strongly dependent on the nuclear symmetry energy, but the
pressure at which last nucleons disappear is independent of it.Comment: 12 pages, 16 figures, Phys. Rev. C in pres
Temperature and momentum dependence of single-particle properties in hot asymmetric nuclear matter
We have studied the effects of momentum dependent interactions on the
single-particle properties of hot asymmetric nuclear matter. In particular, the
single-particle potential of protons and neutrons as well as the symmetry
potential have been studied within a self-consistent model using a momentum
dependent effective interaction. In addition, the isospin splitting of the
effective mass has been derived from the above model. In each case temperature
effects have been included and analyzed. The role of the specific
parametrization of the effective interaction used in the present work has been
investigated. It has been concluded that the behavior of the symmetry potential
depends strongly on the parametrization of the interaction part of the energy
density and the momentum dependence of the regulator function. The effects of
the parametrization have been found to be less pronounced on the isospin mass
splitting.Comment: 22 pages, 14 figure
Low Energy Skyrmion-Skyrmion Scattering
We study the scattering of Skyrmions at low energy and large separation using
the method proposed by Manton of truncation to a finite number of degrees
freedom. We calculate the induced metric on the manifold of the union of
gradient flow curves, which for large separation, to first non-trivial order is
parametrized by the variables of the product ansatz. (presented at the Lake
Louise Winter Institute, 1994)Comment: 6 page
Instabilities of infinite matter with effective Skyrme-type interactions
The stability of the equation of state predicted by Skyrme-type interactions
is examined. We consider simultaneously symmetric nuclear matter and pure
neutron matter. The stability is defined by the inequalities that the Landau
parameters must satisfy simultaneously. A systematic study is carried out to
define interaction parameter domains where the inequalities are fulfilled. It
is found that there is always a critical density beyond which the
system becomes unstable. The results indicate in which parameter regions one
can find effective forces to describe correctly finite nuclei and give at the
same time a stable equation of state up to densities of 3-4 times the
saturation density of symmetric nuclear matter.Comment: 20 pages, 5 figures, submitted to Phys.Rev.
A new window on Strange Quark Matter as the ground state of strongly interacting matter
If strange quark matter is the true ground state of matter, it must have
lower energy than nuclear matter. Simultaneously, two-flavour quark matter must
have higher energy than nuclear matter, for otherwise the latter would convert
to the former. We show, using an effective chiral lagrangian, that the
existence of a new lower energy ground state for two-flavour quark matter, the
pion condensate, shrinks the window for strange quark matter to be the ground
state of matter and sets new limits on the current strange quark mass
A fully relativistic radial fall
Radial fall has historically played a momentous role. It is one of the most
classical problems, the solutions of which represent the level of understanding
of gravitation in a given epoch. A {\it gedankenexperiment} in a modern frame
is given by a small body, like a compact star or a solar mass black hole,
captured by a supermassive black hole. The mass of the small body itself and
the emission of gravitational radiation cause the departure from the geodesic
path due to the back-action, that is the self-force. For radial fall, as any
other non-adiabatic motion, the instantaneous identity of the radiated energy
and the loss of orbital energy cannot be imposed and provide the perturbed
trajectory. In the first part of this letter, we present the effects due to the
self-force computed on the geodesic trajectory in the background field.
Compared to the latter trajectory, in the Regge-Wheeler, harmonic and all
others smoothly related gauges, a far observer concludes that the self-force
pushes inward (not outward) the falling body, with a strength proportional to
the mass of the small body for a given large mass; further, the same observer
notes an higher value of the maximal coordinate velocity, this value being
reached earlier on during infall. In the second part of this letter, we
implement a self-consistent approach for which the trajectory is iteratively
corrected by the self-force, this time computed on osculating geodesics.
Finally, we compare the motion driven by the self-force without and with
self-consistent orbital evolution. Subtle differences are noticeable, even if
self-force effects have hardly the time to accumulate in such a short orbit.Comment: To appear in Int. J. Geom. Meth. Mod. Phy
Shifting the quantum Hall plateau level in a double layer electron system
We study the plateaux of the integer quantum Hall resistance in a bilayer
electron system in tilted magnetic fields. In a narrow range of tilt angles and
at certain magnetic fields, the plateau level deviates appreciably from the
quantized value with no dissipative transport emerging. A qualitative account
of the effect is given in terms of decoupling of the edge states corresponding
to different electron layers/Landau levels.Comment: 3 pages, 3 figures include
Competition of ferromagnetic and antiferromagnetic spin ordering in nuclear matter
In the framework of a Fermi liquid theory it is considered the possibility of
ferromagnetic and antiferromagnetic phase transitions in symmetric nuclear
matter with Skyrme effective interaction. The zero temperature dependence of
ferromagnetic and antiferromagnetic spin polarization parameters as functions
of density is found for SkM, SGII effective forces. It is shown that in the
density domain, where both type of solutions of self--consistent equations
exist, ferromagnetic spin state is more preferable than antiferromagnetic one.Comment: 9p., 3 figure
Satellite DNA evolution in Corvoidea inferred from short and long reads
Satellite DNA (satDNA) is a fast-evolving portion of eukaryotic genomes. The homogeneous and repetitive nature of such satDNA causes problems during the assembly of genomes, and therefore it is still difficult to study it in detail in nonmodel organisms as well as across broad evolutionary timescales. Here, we combined the use of short- and long-read data to explore the diversity and evolution of satDNA between individuals of the same species and between genera of birds spanning ~40 millions of years of bird evolution using birds-of-paradise (Paradisaeidae) and crow (Corvus) species. These avian species highlighted the presence of a GC-rich Corvoidea satellitome composed of 61 satellite families and provided a set of candidate satDNA monomers for being centromeric on the basis of length, abundance, homogeneity and transcription. Surprisingly, we found that the satDNA of crow species rapidly diverged between closely related species while the satDNA appeared more similar between birds-of-paradise species belonging to different genera
Genomic analyses of the Linum distyly supergene reveal convergent evolution at the molecular level
Supergenes govern multi-trait-balanced polymorphisms in a wide range of systems; however, our understanding of their origins and evolution remains incomplete. The reciprocal placement of stigmas and anthers in pin and thrum floral morphs of distylous species constitutes an iconic example of a balanced polymorphism governed by a supergene, the distyly S-locus. Recent studies have shown that the Primula and Turnera distyly supergenes are both hemizygous in thrums, but it remains unknown whether hemizygosity is pervasive among distyly S-loci. As hemizygosity has major consequences for supergene evolution and loss, clarifying whether this genetic architecture is shared among distylous species is critical. Here, we have characterized the genetic architecture and evolution of the distyly supergene in Linum by generating a chromosome-level genome assembly of Linum tenue, followed by the identification of the S-locus using population genomic data. We show that hemizygosity and thrum-specific expression of S-linked genes, including a pistil-expressed candidate gene for style length, are major features of the Linum S-locus. Structural variation is likely instrumental for recombination suppression, and although the non-recombining dominant haplotype has accumulated transposable elements, S-linked genes are not under relaxed purifying selection. Our findings reveal remarkable convergence in the genetic architecture and evolution of independently derived distyly supergenes, provide a counterexample to classic inversion-based supergenes, and shed new light on the origin and maintenance of an iconic floral polymorphism.European Research Council (ERC) 757451Swedish Research Council 2019-04452, 2018-0597
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