9,492 research outputs found
Phase transitions and spin excitations of spin-1 bosons in optical lattice
We investigate ground state properties of spin-1 bosonic system trapped in
optical lattice with extended standard basis operator (SBO) method. For both
ferromagnetic () systems, we
analytically figure out the symmetry properties in Mott-insulator and
superfluid phases, which would provide a deeper insight into the MI-SF phase
transition process. Then by applying self-consistent approach to the method, we
include the effect of quantum and thermal fluctuations and derive the MI-SF
transition phase diagram, which is in quantitative agreement with recent
Monte-Carlo simulation at zero temperature, and at finite temperature, we find
the underestimation of finite-temperature-effect in the mean-field
approximation method. If we further consider the spin excitations in the
insulating states of spin-1 system in external field, distinct spin phases are
expected. Therefore, in the Mott lobes with and atoms per site, we
give analytical and numerical boundaries of the singlet, nematic, partially
magnetic and ferromagnetic phases in the magnetic phase diagrams.Comment: 14 pages, 6 figure
Risk Minimization, Regret Minimization and Progressive Hedging Algorithms
This paper begins with a study on the dual representations of risk and regret
measures and their impact on modeling multistage decision making under
uncertainty. A relationship between risk envelopes and regret envelopes is
established by using the Lagrangian duality theory. Such a relationship opens a
door to a decomposition scheme, called progressive hedging, for solving
multistage risk minimization and regret minimization problems. In particular,
the classical progressive hedging algorithm is modified in order to handle a
new class of linkage constraints that arises from reformulations and other
applications of risk and regret minimization problems. Numerical results are
provided to show the efficiency of the progressive hedging algorithms.Comment: 21 pages, 2 figure
Surface diffuseness correction in global mass formula
By taking into account the surface diffuseness correction for unstable
nuclei, the accuracy of the macroscopic-microscopic mass formula is further
improved. The rms deviation with respect to essentially all the available mass
data falls to 298 keV, crossing the 0.3 MeV accuracy threshold for the first
time within the mean-field framework. Considering the surface effect of the
symmetry potential which plays an important role in the evolution of the
"neutron skin" toward the "neutron halo" of nuclei approaching the neutron drip
line, we obtain an optimal value of the symmetry energy coefficient J=30.16
MeV. With an accuracy of 258 keV for all the available neutron separation
energies and of 237 keV for the alpha-decay Q-values of super-heavy nuclei, the
proposed mass formula is particularly important not only for the reliable
description of the r-process of nucleosynthesis but also for the study of the
synthesis of super-heavy nuclei.Comment: 2 figures, 2 tables, to appear in Phys. Lett.
4-Chloroanilinium tetrafluoroborate 18-crown-6 clathrate
In the title compound, C6H7ClN+·BF4
−·C12H24O6, the complete cation is generated by crystallographic mirror symmetry, with two C atoms and the N and Cl atoms lying on the mirror plane. The complete crown ether is also generated by mirror symmetry, as is the anion (in which the B and two F atoms lie on the mirror plane). The –NH3
+ group of the cation inserts into the crown-ether ring and forms bifurcated N—H⋯(O,O) hydrogen bonds. The H atoms of the –NH3
+ group were modelled as disordered across the mirror plane
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