5,371 research outputs found
Electron screening in the liquid-gas mixed phases of nuclear matter
Screening effects of electrons on inhomogeneous nuclear matter, which
includes spherical, slablike, and rodlike nuclei as well as spherical and
rodlike nuclear bubbles, are investigated in view of possible application to
cold neutron star matter and supernova matter at subnuclear densities. Using a
compressible liquid-drop model incorporating uncertainties in the surface
tension, we find that the energy change due to the screening effects broadens
the density region in which bubbles and nonspherical nuclei appear in the phase
diagram delineating the energetically favorable shape of inhomogeneous nuclear
matter. This conclusion is considered to be general since it stems from a
model-independent feature that the electron screening acts to decrease the
density at which spherical nuclei become unstable against fission and to
increase the density at which uniform matter becomes unstable against proton
clustering.Comment: 12 pages, 8 figures, accepted for publication in Physical Review
Simulation of Transitions between "Pasta" Phases in Dense Matter
Calculations of equilibrium properties of dense matter predict that at
subnuclear densities nuclei can be rodlike or slablike. To investigate whether
transitions between phases with non-spherical nuclei can occur during the
collapse of a star, we perform quantum molecular dynamic simulations of the
compression of dense matter. We have succeeded in simulating the transitions
between rodlike and slablike nuclei and between slablike nuclei and cylindrical
bubbles. Our results strongly suggest that non-spherical nuclei can be formed
in the inner cores of collapsing stars.Comment: 4 pages, 4 figures, final version published in Phys. Rev. Lett.,
high-res figures can be seen at http://www.nordita.dk/~gentaro/research/fig
Meteor Shower Activity Derived from "Meteor Watching Public-Campaign" in Japan
We tried to analyze activities of meteor showers from accumulated data collected by public campaigns for meteor showers which were performed as outreach programs. The analyzed campaigns are Geminids (in 2007 and 2009), Perseids (in 2008 and 2009), Quadrantids (in 2009) and Orionids (in 2009). Thanks to the huge number of reports, the derived time variations of the activities of meteor showers is very similar to those obtained by skilled visual observers. The values of hourly rates are about one-fifth (Geminids 2007) or about one-fourth (Perseids 2008) compared with the data of skilled observers, mainly due to poor observational sites such as large cities and urban areas, together with the immature skill of participants in the campaign. It was shown to be highly possible to estimate time variation in the meteor shower activity from our campaign
Identification of Optical Component of North Toroidal Source of Sporadic Meteors and its Origin
We succeeded to identify the North Toroidal source by optical observations performed by the SonotaCo Network, which is a TV observation network coordinated by Japanese amateurs. This source has been known only for radar observations until now. The orbits of the optical meteors in the North Toroidal source are relatively large eccentricity and semi-major axis, compared with those of the radar meteors. In this paper, we report the characteristics of this North Toroidal source detected by optical observations, and discuss the possible origin and evolution of this source
Distinct Fe-induced magnetic states in the underdoped and overdoped regimes of La2-xSrxCu1-yFeyO4 revealed by muon spin relaxation
Zero-field and longitudinal-field muon-spin-relaxation measurements have been
performed in partially Fe-substituted La2-xSrxCu1-yFeyO4 in a wide range of
hole concentration, to investigate the magnetic state induced by the Fe
substitution recently suggested from the neutron-scattering measurements [Phys.
Rev. Lett. 107, 127002 (2011)]. It has been found that the magnetic transition
temperature is notably enhanced through the 1% Fe substitution in a wide range
of hole concentration where superconductivity appears in Fe-free La2-xSrxCuO4.
In the underdoped regime, the Fe-induced magnetic order can be understood in
terms of the concept of stripe pinning by Fe as in the case of the Zn-induced
one in La2-xSrxCu1-yZnyO4. In the overdoped regime, on the other hand, the
Fe-induced magnetic order is short-ranged, which is distinct from the stripes.
It is plausible that a spin-glass state of Fe spins derived from the
Ruderman-Kittel-Kasuya-Yosida interaction is realized in the overdoped regime,
suggesting a change of the ground state from the strongly correlated state to
the Fermi-liquid state with hole doping in La-214 high-Tc cuprates.Comment: 10 pages, 6 figures, accepted for publication in Phys. Rev.
- …