76,996 research outputs found
T-Shape Molecular Heat Pump
We report on the first molecular device of heat pump modeled by a T-shape
Frenkel-Kontorova lattice. The system is a three-terminal device with the
important feature that the heat can be pumped from the low-temperature region
to the high-temperature region through the third terminal. The pumping action
is achieved by applying a stochastic external force that periodically modulates
the atomic temperature. The temperature, the frequency and the system size
dependence of heat pump are briefly discussed.Comment: 6 figure
Indirect exchange of magnetic impurities in zigzag graphene ribbon
We use quantum Monte Carlo method to study the indirect coupling between two
magnetic impurities on the zigzag edge of graphene ribbon, with respect to the
chemical potential . We find that the spin-spin correlation between two
adatoms located on the nearest sites in the zigzag edge are drastically
suppressed around the zero-energy. As we switch the system away from
half-filling, the antiferromagnetic correlation is first enhanced and then
decreased. If the two adatoms are adsorbed on the sites belonging to the same
sublattice, we find similar behavior of spin-spin correlation except for a
crossover from ferromagnetic to antiferromagentic correlation in the vicinity
of zero-energy. We also calculated the weight of different components of
d-electron wave function and local magnet moment for various values of
parameters, and all the results are consistent with those of spin-spin
correlation between two magnetic impurities.Comment: 3 pages, 4 figures, conference proceedin
Extended quark mean-field model for neutron stars
We extend the quark mean-field (QMF) model to strangeness freedom to study
the properties of hyperons () in infinite baryon matter and
neutron star properties. The baryon-scalar meson couplings in the QMF model are
determined self-consistently from the quark level, where the quark confinement
is taken into account in terms of a scalar-vector harmonic oscillator
potential. The strength of such confinement potential for quarks is
constrained by the properties of finite nuclei, while the one for quark is
limited by the properties of nuclei with a hyperon. These two
strengths are not same, which represents the SU(3) symmetry breaking
effectively in the QMF model. Also, we use an enhanced coupling with
the vector meson, and both and hyperon potentials can be
properly described in the model. The effects of the SU(3) symmetry breaking on
the neutron star structures are then studied. We find that the SU(3) breaking
shifts earlier the hyperon onset density and makes hyperons more abundant in
the star, in comparisons with the results of the SU(3) symmetry case. However,
it does not affect much the star's maximum mass. The maximum masses are found
to be with hyperons and without hyperons. The
present neutron star model is shown to have limitations on explaining the
recently measured heavy pulsar.Comment: 7 pages, 7 figures, Phys. Rev. C (2014) accepte
Asymmetric Properties of Heat Conduction in a One-Dimensional Frenkel-Kontorova Model
In this Letter, we show numerically that the rectifying effect of heat flux
in a one-dimensional two-segment Frenkel-Kontorova chain demonstrated in recent
literature is merely available under the limit of the weak coupling between the
two constituent segments. Surprisingly, the rectifying effect will be reversed
when the properties of the interface and the system size change. The two types
of asymmetric heat conduction are dominated by different mechanisms, which are
all induced by the nonlinearity. We further discuss the possibility of the
experimental realization of thermal diode or rectifier devices.Comment: 4 Pages, 4 figure
A test of the CPL parameterization for rapid dark energy equation of state transitions
We test the robustness and flexibility of the Chevallier-Polarski-Linder
(CPL) parameterization of the Dark Energy equation of state in recovering a four-parameter step-like fiducial model. We
constrain the parameter space region of the underlying fiducial model where the
CPL parameterization offers a reliable reconstruction. It turns out that non
negligible biases leak into the results for recent () rapid transitions,
but that CPL yields a good reconstruction in all other cases. The presented
analysis is performed with supernova Ia data as forecasted for a space mission
like SNAP/JDEM, combined with future expectations for the CMB shift parameter
and the BAO parameter .Comment: 8 pages, 6 ps figure
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