681 research outputs found
Quantum Bose Josephson Junction with binary mixtures of BECs
We study the quantum behaviour of a binary mixture of Bose-Einstein
condensates (BEC) in a double-well potential starting from a two-mode
Bose-Hubbard Hamiltonian. We focus on the small tunneling amplitude regime and
apply perturbation theory up to second order. Analytical expressions for the
energy eigenvalues and eigenstates are obtained. Then the quantum evolution of
the number difference of bosons between the two potential wells is fully
investigated for two different initial conditions: completely localized states
and coherent spin states. In the first case both the short and the long time
dynamics is studied and a rich behaviour is found, ranging from small amplitude
oscillations and collapses and revivals to coherent tunneling. In the second
case the short-time scale evolution of number difference is determined and a
more irregular dynamics is evidenced. Finally, the formation of Schroedinger
cat states is considered and shown to affect the momentum distribution.Comment: 14 pages, 4 figure
Parasitic pumping currents in an interacting quantum dot
We analyze the charge and spin pumping in an interacting dot within the
almost adiabatic limit. By using a non-equilibrium Green's function technique
within the time-dependent slave boson approximation, we analyze the pumped
current in terms of the dynamical constraints in the infinite-U regime. The
results show the presence of parasitic pumping currents due to the additional
phases of the constraints. The behavior of the pumped current through the
quantum dot is illustrated in the spin-insensitive and in the spin-sensitive
case relevant for spintronics applications
Critical behaviour of a spin-tube model in a magnetic field
We show that the low-energy physics of the spin-tube model in presence of a
critical magnetic field can be described by a broken SU(3) spin chain. Using
the Lieb-Schultz-Mattis Theorem we characterize the possible magnetization
plateaus and study the critical behavior in the region of transition between
the plateaus m=1/2 and m=3/2 by means of renormalization group calculations
performed on the bosonized effective continuum field theory. We show that in
certain regions of the parameter space of the effective theory the system
remains gapless, and we compute the spin-spin correlation functions in these
regions. We also discuss the possibility of a plateau at m=1, and show that
although there exists in the continuum theory a term that might cause the
appearance of a plateau there, such term is unlikely to be relevant. This
conjecture is proved by DMRG techniques. The modifications of the three-leg
ladder Hamiltonian that might show plateaus at m =1,5/6,7/6 are discussed, and
we give the expected form of correlation functions on the m=1 plateau.Comment: RevTeX, 43 pages, 5 EPS figure
Kecerdasan Emosional dan Kecerdasan Spiritual Meningkatkan Kompetensi Sosial Guru
Teacher as a professional educational is demanded to have a set of competence in carrying out the daily tasks. One of the competences is social competence. The social competence of teachers is that teachers have an objective, inclusive and non discriminative attitude, well-mannered eitherin speech or in act, capable in communicating verbally, writtenly and gesture. In addition, teachers have to coordinate with the students, other fellow teachers, educational staff, student's parents as well asthe society. They must also be able to adapt with the community. This study aims to determine the relationship between emotional intelligence and spiritual intelligence work with the social competence of teachers in Vocational Schools of Gorontalo City. The result of multiple correlation coefficient which showed between emotional intelligence and spiritual intelegence toward social competence. This means that the better the emotional and spiritual intelligence of teacher, the better the effect of the social competence of teachers will be. Keywords: emotional intelligence, spiritual intelligence, teachers, social competenc
Temperature and doping dependence of normal state spectral properties in a two-orbital model for ferropnictides
Using a second-order perturbative Green's functions approach we determined
the normal state single-particle spectral function
employing a minimal effective model for iron-based superconductors. The
microscopic model, used before to study magnetic fluctuations and
superconducting properties, includes the two effective tight-binding bands
proposed by S.Raghu et al. [Phys. Rev. B 77, 220503 (R) (2008)], and intra- and
inter-orbital local electronic correlations, related to the Fe-3d orbitals.
Here, we focus on the study of normal state electronic properties, in
particular the temperature and doping dependence of the total density of
states, , and of in different Brillouin zone
regions, and compare them to the existing angle resolved photoemission
spectroscopy (ARPES) and previous theoretical results in ferropnictides. We
obtain an asymmetric effect of electron and hole doping, quantitative agreement
with the experimental chemical potential shifts as a function of doping, as
well as spectral weight redistributions near the Fermi level as a function of
temperature consistent with the available experimental data. In addition, we
predict a non-trivial dependence of the total density of states with the
temperature, exhibiting clear renormalization effects by correlations.
Interestingly, investigating the origin of this predicted behaviour by
analyzing the evolution with temperature of the k-dependent self-energy
obtained in our approach, we could identify a number of specific Brillouin zone
points, none of them probed by ARPES experiments yet, where the largest
non-trivial effects of temperature on the renormalization are present.Comment: Manuscript accepted in Physics Letters A on Feb. 25, 201
Normal state electronic properties of LaOFBiS superconductors
A good description of the electronic structure of BiS-based
superconductors is essential to understand their phase diagram, normal state
and superconducting properties. To describe the first reports of normal state
electronic structure features from angle resolved photoemission spectroscopy
(ARPES) in LaOFBiS, we used a minimal microscopic model to
study their low energy properties. It includes the two effective tight-binding
bands proposed by Usui et al [Phys.Rev.B 86, 220501(R)(2012)], and we added
moderate intra- and inter-orbital electron correlations related to Bi-(,
) and S-(, ) orbitals. We calculated the electron Green's
functions using their equations of motion, which we decoupled in second-order
of perturbations on the correlations. We determined the normal state spectral
density function and total density of states for LaOFBiS,
focusing on the description of the k-dependence, effect of doping, and the
prediction of the temperature dependence of spectral properties. Including
moderate electron correlations, improves the description of the few
experimental ARPES and soft X-ray photoemission data available for
LaOFBiS. Our analytical approximation enabled us to
calculate the spectral density around the conduction band minimum at
, and to predict the temperature dependence of
the spectral properties at different BZ points, which might be verified by
temperature dependent ARPES.Comment: 9 figures. Manuscript accepted in Physica B: Condensed Matter on Jan.
25, 201
Noise-assisted Thouless pump in elastically deformable molecular junctions
We study a Thouless pump realized with an elastically \textit{deformable
quantum dot} whose center of mass follows a non-linear stochastic dynamics. The
interplay of noise, non-linear effects, dissipation and interaction with an
external time-dependent driving on the pumped charge is fully analyzed. The
results show that the quantum pumping mechanism not only is not destroyed by
the force fluctuations, but it becomes stronger when the forcing signal
frequency is tuned close to the resonance of the vibrational mode. The
robustness of the quantum pump with temperature is also investigated and an
exponential decay of the pumped charge is found when the coupling to the
vibrational mode is present. Implications of our results for
nano-electromechanical systems are also discussed.Comment: 2 Appendices and figures adde
An efficient consistency management algorithm for real-time mobile collaboration
Real time mobile collaboration involves two or more co-workers operating concurrently on a shared document using independent mobile devices. The replicated architecture is attractive for such applications since it does not rely on a central server and a user can continue to work on his or her own local document replica even during disconnection period. Several consistency management algorithms have been proposed, however the resource usage of such algorithms, which is critical in a mobile environment, has not been formally studied. Mobile devices are constrained in terms of memory and processing power, and operate in networking environments with limited bandwidth and transient connectivity. Therefore, algorithms that use resources more effectively improve the quality of the user experience in a mobile environment. ISO 9126-1 considers software to be efficient if it provides a balance between performance, and resource utilisation while performing its function. Therefore, this paper evaluates the efficiency of existing techniques, and proposes a more efficient consistency management algorithm. The new algorithm leverages existing techniques which are shown to be efficient and incorporates a novel history management strategy called partial history copy. Different combinations of these techniques are tested and compared to determine which one is most efficient and thus suitable for mobile usage
Off-diagonal correlations in a one-dimensional gas of dipolar bosons
We present a quantum Monte Carlo study of the one-body density matrix (OBDM)
and the momentum distribution of one-dimensional dipolar bosons, with dipole
moments polarized perpendicular to the direction of confinement. We observe
that the long-range nature of the dipole interaction has dramatic effects on
the off-diagonal correlations: although the dipoles never crystallize, the
system goes from a quasi-condensate regime at low interactions to a regime in
which quasi-condensation is discarded, in favor of quasi-solidity. For all
strengths of the dipolar interaction, the OBDM shows an oscillatory behavior
coexisting with an overall algebraic decay; and the momentum distribution shows
sharp kinks at the wavevectors of the oscillations, (where
is the atom density), beyond which it is strongly suppressed. This
\emph{momentum filtering} effect introduces a characteristic scale in the
momentum distribution, which can be arbitrarily squeezed by lowering the atom
density. This shows that one-dimensional dipolar Bose gases, realized e.g. by
trapped dipolar molecules, show strong signatures of the dipolar interaction in
time-of-flight measurements.Comment: 10 pages, 6 figures. v2: fixed a mistake in the comparison with Ref.
9, as well as several typos. Published versio
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