144,284 research outputs found
Ground State Energy for Fermions in a 1D Harmonic Trap with Delta Function Interaction
Conjectures are made for the ground state energy of a large spin 1/2 Fermion
system trapped in a 1D harmonic trap with delta function interaction. States
with different spin J are separately studied. The Thomas-Fermi method is used
as an effective test for the conjecture.Comment: 4 pages, 3 figure
Xenon fluorides show potential as fluorinating agents
Xenon fluorides permit the controlled addition of fluorine across an olefinic double bond. They provide a series of fluorinating agents that permit ready separation from the product at a high purity. The reactions may be carried out in the vapor phase
A mathematical model of the effect of a predator on species diversity
Mathematical model determines reaction between new predator and microbe competitor when the competitor is the predator's sole nutrient resource. The model utilizes differential equations to describe the interactions with the specific growth rates, and analyzes these growth rates as they are affected by population density and nutrient concentration
GAPS IN THE HEISENBERG-ISING MODEL
We report on the closing of gaps in the ground state of the critical
Heisenberg-Ising chain at momentum . For half-filling, the gap closes at
special values of the anisotropy , integer. We explain
this behavior with the help of the Bethe Ansatz and show that the gap scales as
a power of the system size with variable exponent depending on . We use
a finite-size analysis to calculate this exponent in the critical region,
supplemented by perturbation theory at . For rational
fillings, the gap is shown to be closed for {\em all} values of and
the corresponding perturbation expansion in shows a remarkable
cancellation of various diagrams.Comment: 12 RevTeX pages + 4 figures upon reques
Quantum phase transition and engineering in two-component BEC in optical lattices
In this paper we review recent progress in studying quantum phase transitions
in one- and two-component Bose-Einstein condensates (BEC) in optical lattices.
These phase transitions involve the emergence and disappearance of quantum
coherence over whole optical lattice and of linear superposition of macroscopic
quantum states. The latter may provide new means to engineer and to manipulate
novel macroscopic quantum states and novel coherent atomic beams for quantum
information processing, quantum computing etc.Comment: Format: LaTex2e. 7 pages, no figure. Talk at the Yang Symposium (in
honor of C.N. Yang's 80th birthday), Beijing, China, June 2002. To appear in
the Proceeding
Solvable Lattice Gas Models with Three Phases
Phase boundaries in p-T and p-V diagrams are essential in material science
researches. Exact analytic knowledge about such phase boundaries are known so
far only in two-dimensional (2D) Ising-like models, and only for cases with two
phases. In the present paper we present several lattice gas models, some with
three phases. The phase boundaries are either analytically calculated or
exactly evaluated.Comment: 5 pages, 6 figure
Design and analysis of a wire-driven flexible manipulator for bronchoscopic interventions
Bronchoscopic interventions are widely performed for the diagnosis and treatment of lung diseases. However, for most endobronchial devices, the lack of a bendable tip restricts their access ability to get into distal bronchi with complex bifurcations. This paper presents the design of a new wire-driven continuum manipulator to help guide these devices. The proposed manipulator is built by assembling miniaturized blocks that are featured with interlocking circular joints. It has the capability of maintaining its integrity when the lengths of actuation wires change due to the shaft flex. It allows the existence of a relatively large central cavity to pass through other instruments and enables two rotational degrees of freedom. All these features make it suitable for procedures where tubular anatomies are involved and the flexible shafts have to be considerably bent in usage, just like bronchoscopic interventions. A kinematic model is built to estimate the relationship between the translations of actuation wires and the manipulator tip position. A scale-up model is produced for evaluation experiments and the results validate the performance of the proposed mechanism
Hidden symmetry and quantum phases in spin-3/2 cold atomic systems
Optical traps and lattices provide a new opportunity to study strongly
correlated high spin systems with cold atoms. In this article, we review the
recent progress on the hidden symmetry properties in the simplest high spin
fermionic systems with hyperfine spin , which may be realized with atoms
of Cs, Be, Ba, Ba, and Hg. A {\it generic}
SO(5) or isomorphically, ) symmetry is proved in such systems with the
s-wave scattering interactions in optical traps, or with the on-site Hubbard
interactions in optical lattices. Various important features from this high
symmetry are studied in the Fermi liquid theory, the mean field phase diagram,
and the sign problem in quantum Monte-Carlo simulations. In the s-wave quintet
Cooper pairing phase, the half-quantum vortex exhibits the global analogue of
the Alice string and non-Abelian Cheshire charge properties in gauge theories.
The existence of the quartetting phase, a four-fermion counterpart of the
Cooper pairing phase, and its competition with other orders are studied in one
dimensional spin-3/2 systems. We also show that counter-intuitively quantum
fluctuations in spin-3/2 magnetic systems are even stronger than those in
spin-1/2 systems
Fractional Energy Loss and Centrality Scaling
The phenomenon of centrality scaling in the high-\pt spectra of
produced in Au-Au collisions at GeV is examined in the framework
of relating fractional energy loss to fractional centrality increase. A new
scaling behavior is found where the scaling variable is given a power-law
dependence on . The exponent specifies the fractional
proportionality relationship between energy loss and centrality, and is a
phenomenologically determined number that characterizes the nuclear suppression
effect. The implication on the parton energy loss in the context of
recombination is discussed.Comment: 4 pages in RevTe
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