13,820 research outputs found
Heat conduction of single-walled carbon nanotube isotope-superlattice structures: A molecular dynamics study
Heat conduction of single-walled carbon nanotubes (SWNTs)
isotope-superlattice is investigated by means of classical molecular dynamics
simulations. Superlattice structures were formed by alternately connecting
SWNTs with different masses. On varying the superlattice period, the critical
value with minimum effective thermal conductivity was identified, where
dominant physics switches from zone-folding effect to thermal boundary
resistance of lattice interface. The crossover mechanism is explained with the
energy density spectra where zone-folding effects can be clearly observed. The
results suggest that the critical superlattice period thickness depends on the
mean free path distribution of diffusive-ballistic phonons. The reduction of
the thermal conductivity with superlattice structures beats that of the
one-dimensional alloy structure, though the minimum thermal conductivity is
still slightly higher than the value obtained by two-dimensional random mixing
of isotopes.Comment: 7 Pages, 5 figures, accepted to Phys. Rev.
Impact of Rotation on Quark-Hadron Hybrid Stars
Many recent observations give restrictions to the equation of state (EOS) for
high-density matter. Theoretical studies are needed to try to elucidate these
EOSs at high density and/or temperature. With the many known rapidly rotating
neutron stars, e.g., pulsars, several theoretical studies have tried to take
into account the effects of rotation. In our study of these systems, we find
that one of our EOSs is consistent with recent observation, whereas the other
is inconsistent.Comment: Quarks and Compact Stars 201
Observing quantum non-locality in the entanglement between modes of massive particles
We consider the question of whether it is possible to use the entanglement
between spatially separated modes of massive particles to observe nonlocal
quantum correlations. Mode entanglement can be obtained using a single
particle, indicating that it requires careful consideration before concluding
whether experimental observation, e.g. violation of Bell inequalities, is
possible or not. In the simplest setups analogous to optics experiments, that
observation is prohibited by fundamental conservation laws. However, we show
that using auxiliary particles, mode entanglement can be converted into forms
that allow the observation of quantum non-locality. The probability of
successful conversion depends on the nature and number of auxiliary particles
used. In particular, we find that an auxiliary Bose-Einstein condensate allows
the conversion arbitrarily many times with a small error that depends only on
the initial state of the condensate.Comment: 8 pages (two-column), 2 figure
Multi-antikaonic nuclei in the relativistic mean-field theory
Properties of multi-antikaonic nuclei (MKN), where several numbers of
mesons are bound, are studied in the relativistic mean-field model, combined
with chiral dynamics for kaonic part of the thermodynamic potential. The
density profiles for nucleons and mesons, the single particle energy of
the mesons, and binding energy of the MKN are obtained. The effects of
the interactions on these quantities are discussed in
comparison with other meson (, , and )-exchange models.
It is shown that the interactions originate from two
contributions: One is the contact interaction between antikaons inherent in
chiral symmetry, and the other is the one generated through coupling between
the and meson mean fields. Both effects of the repulsive
interactions become large on the ground state properties of the MKN as the
number of the embedded mesons increases. A relation between the
multi-antikaonic nuclei and kaon condensation in infinite and uniform matter is
mentioned.Comment: 27 pages, 13 figure
Properties of hadron and quark matter studied with a molecular dynamics
We study the hadron-quark phase transition in a molecular dynamics (MD) of
quark degrees of freedom. The hadron state at low density and temperature, and
the deconfined quark state at high density and temperature are observed in our
model. We investigate the equations of state and draw the phase-diagram at wide
baryon density and temperature range. We also discuss the transport property,
e.g. viscosity, of matter. It is found that the ratio of the shear
viscosity to the entropy density is less than one for quark matter.Comment: Poster presentation at Quark Matter 200
Nonequilibrium Green's Function Approach to Phonon Transport in Defective Carbon Nanotubes
We have developed a new theoretical formalism for phonon transport in
nanostructures using the nonequilibrium phonon Green's function technique and
have applied it to thermal conduction in defective carbon nanotubes. The
universal quantization of low-temperature thermal conductance in carbon
nanotubes can be observed even in the presence of local structural defects such
as vacancies and Stone-Wales defects, since the long wavelength acoustic
phonons are not scattered by local defects. At room temperature, however,
thermal conductance is critically affected by defect scattering since incident
phonons are scattered by localized phonons around the defects. We find a
remarkable change from quantum to classical features for the thermal transport
through defective CNTs with increasing temperature.Comment: 5 pages, 3 figures, accepted for publication in Phys. Rev. Let
Online Self-Indexed Grammar Compression
Although several grammar-based self-indexes have been proposed thus far,
their applicability is limited to offline settings where whole input texts are
prepared, thus requiring to rebuild index structures for given additional
inputs, which is often the case in the big data era. In this paper, we present
the first online self-indexed grammar compression named OESP-index that can
gradually build the index structure by reading input characters one-by-one.
Such a property is another advantage which enables saving a working space for
construction, because we do not need to store input texts in memory. We
experimentally test OESP-index on the ability to build index structures and
search query texts, and we show OESP-index's efficiency, especially
space-efficiency for building index structures.Comment: To appear in the Proceedings of the 22nd edition of the International
Symposium on String Processing and Information Retrieval (SPIRE2015
Coupled Breathing Oscillations of Two-Component Fermion Condensates in Deformed Traps
We investigate collective excitations coupled with monopole and quadrupole
oscillations in two-component fermion condensates in deformed traps. The
frequencies of monopole and dipole modes are calculated using Thomas-Fermi
theory and the scaling approximation. When the trap is largely deformed, these
collective motions are decoupled to the transverse and longitudinal breathing
oscillation modes. As the trap approaches becoming spherical, however, they are
coupled and show complicated behaviors.Comment: 18 pages and 8 figure
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