9,457 research outputs found
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
Ordered and disordered dynamics in monolayers of rolling particles
We consider the ordered and disordered dynamics for monolayers of rolling
self-interacting particles with an offset center of mass and a non-isotropic
inertia tensor. The rolling constraint is considered as a simplified model of a
very strong, but rapidly decaying bond with the surface, preventing application
of the standard tools of statistical mechanics. We show the existence and
nonlinear stability of ordered lattice states, as well as disturbance
propagation through and chaotic vibrations of these states. We also investigate
the dynamics of disordered gas states and show that there is a surprising and
robust linear connection between distributions of angular and linear velocity
for both lattice and gas states, allowing to define the concept of temperature
Analysis of proton-induced fragment production cross sections by the Quantum Molecular Dynamics plus Statistical Decay Model
The production cross sections of various fragments from proton-induced
reactions on Fe and Al have been analyzed by the Quantum
Molecular Dynamics (QMD) plus Statistical Decay Model (SDM). It was found that
the mass and charge distributions calculated with and without the statistical
decay have very different shapes. These results also depend strongly on the
impact parameter, showing an importance of the dynamical treatment as realized
by the QMD approach. The calculated results were compared with experimental
data in the energy region from 50 MeV to 5 GeV. The QMD+SDM calculation could
reproduce the production cross sections of the light clusters and
intermediate-mass to heavy fragments in a good accuracy. The production cross
section of Be was, however, underpredicted by approximately 2 orders of
magnitude, showing the necessity of another reaction mechanism not taken into
account in the present model.Comment: 12 pages, Latex is used, 6 Postscript figures are available by
request from [email protected]
Isoscalar Giant Quadrupole Resonance State in the Relativistic Approach with the Momentum-Dependent Self-Energies
We study the excited energy of the isoscalar giant quadrupole resonance with
the scaling method in the relativistic many-body framework. In this calculation
we introduce the momentum-dependent parts of the Dirac self-energies arising
from the one-pion exchange on the assumption of the pseudo-vector coupling with
nucleon field. It is shown that this momentum-dependence enhances the Landau
mass significantly and thus suppresses the quadrupole resonance energy even
giving the small Dirac effective mass which causes a problem in the
momentum-independent mean-field theory.Comment: 12pages, 2 Postscript figure
Non-local Control of the Kondo Effect in a Double Quantum Dot-Quantum Wire Coupled System
We have performed low-temperature transport measurements on a double quantum
dot-quantum wire coupled device and demonstrated non-local control of the Kondo
effect in one dot by manipulating the electronic spin states of the other. We
discuss the modulation of the local density of states in the wire region due to
the Fano-Kondo antiresonance, and the Ruderman-Kittel-Kasuya-Yoshida (RKKY)
exchange interaction as the mechanisms responsible for the observed features.Comment: 4 pages, 4 figure
The low-temperature energy calibration system for the CUORE bolometer array
The CUORE experiment will search for neutrinoless double beta decay (0nDBD)
of 130Te using an array of 988 TeO_2 bolometers operated at 10 mK in the
Laboratori Nazionali del Gran Sasso (Italy). The detector is housed in a large
cryogen-free cryostat cooled by pulse tubes and a high-power dilution
refrigerator. The TeO_2 bolometers measure the event energies, and a precise
and reliable energy calibration is critical for the successful identification
of candidate 0nDBD and background events. The detector calibration system under
development is based on the insertion of 12 gamma-sources that are able to move
under their own weight through a set of guide tubes that route them from
deployment boxes on the 300K flange down into position in the detector region
inside the cryostat. The CUORE experiment poses stringent requirements on the
maximum heat load on the cryostat, material radiopurity, contamination risk and
the ability to fully retract the sources during normal data taking. Together
with the integration into a unique cryostat, this requires careful design and
unconventional solutions. We present the design, challenges, and expected
performance of this low-temperature energy calibration system.Comment: To be published in the proceedings of the 13th International Workshop
on Low Temperature Detectors (LTD), Stanford, CA, July 20-24, 200
Hadron-quark mixed phase in hyperon stars
We analyze the different possibilities for the hadron-quark phase transition
occurring in beta-stable matter including hyperons in neutron stars. We use a
Brueckner-Hartree-Fock approach including hyperons for the hadronic equation of
state and a generalized MIT bag model for the quark part. We then point out in
detail the differences between Maxwell and Gibbs phase transition constructions
including the effects of surface tension and electromagnetic screening. We find
only a small influence on the maximum neutron star mass, whereas the radius of
the star and in particular its internal structure are more affected.Comment: 11 pages, 9 figure
Atomic Hydrogen Cleaning of Polarized GaAs Photocathodes
Atomic hydrogen cleaning followed by heat cleaning at 450C was used
to prepare negative-electron-affinity GaAs photocathodes. When hydrogen ions
were eliminated, quantum efficiencies of 15% were obtained for bulk GaAs
cathodes, higher than the results obtained using conventional 600C heat
cleaning. The low-temperature cleaning technique was successfully applied to
thin, strained GaAs cathodes used for producing highly polarized electrons. No
depolarization was observed even when the optimum cleaning time of about 30
seconds was extended by a factor of 100
Strain-Compensated AlInGaAs-GaAsP Superlattices for Highly-Polarized Electron Emission
Spin-polarized electron emission from the first superlattice photocathodes
developed with strain compensation is investigated. An opposite strain in the
quantum well and barrier layers is complished using an InAlGaAs/GaAsP
superlattice structure. The measured values of maximum polarization and quantum
yield for the structure with a 0.18 um-thick working layer are close to the
best results reported for any strained superlattice photocathode structure,
demonstrating the high potential of strain compensation for future photocathode
applications. An analysis of the photoemission spectra is used to estimate the
parameters responsible for the polarization losses.Comment: 10 pages, 2 figure
Thermodynamical Cost of Accessing Quantum Information
Thermodynamics is a macroscopic physical theory whose two very general laws
are independent of any underlying dynamical laws and structures. Nevertheless,
its generality enables us to understand a broad spectrum of phenomena in
physics, information science and biology. Recently, it has been realised that
information storage and processing based on quantum mechanics can be much more
efficient than their classical counterpart. What general bound on storage of
quantum information does thermodynamics imply? We show that thermodynamics
implies a weaker bound than the quantum mechanical one (the Holevo bound). In
other words, if any post-quantum physics should allow more information storage
it could still be under the umbrella of thermodynamics.Comment: 3 figure
- …