36,167 research outputs found
Berry phase in a composite system
The Berry phase in a composite system with only one subsystem being driven
has been studied in this Letter. We choose two spin- systems with
spin-spin couplings as the composite system, one of the subsystems is driven by
a time-dependent magnetic field. We show how the Berry phases depend on the
coupling between the two subsystems, and what is the relation between these
Berry phases of the whole system and those of the subsystems.Comment: 4 pages, 6 figure
Initial overview of disconnection events in Halley's Comet 1986
We present an initial overview of the disconnection events (DE's) in Comet Halley in 1986. Although disconnection events are arguably the most spectacular of all dynamic comet phenomena, the mechanisms by which they occur are not fully understood. It is generally believed that the solar wind plays a major role in determining when disconnection events occur, but the details of the solar wind/cometary interactions responsible for initiating the tail disconnection are still under debate. The three most widely accepted models are: (1) high speed streams in the solar wind cause the tail to disconnect due to pressure effects; (2) decreased production of cometary ions in a high speed stream allows magnetic field to slip away from the comet; and (3) the tail disconnects after frontside reconnection of the interplanetary magnetic field (IMF) as the comet crosses a magnetic field sector boundary. We find that the front-side magnetic reconnection model is the best explanation for the DE's we have considered
Stabilization of the p-wave superfluid state in an optical lattice
It is hard to stabilize the p-wave superfluid state of cold atomic gas in
free space due to inelastic collisional losses. We consider the p-wave Feshbach
resonance in an optical lattice, and show that it is possible to have a stable
p-wave superfluid state where the multi-atom collisional loss is suppressed
through the quantum Zeno effect. We derive the effective Hamiltonian for this
system, and calculate its phase diagram in a one-dimensional optical lattice.
The results show rich phase transitions between the p-wave superfluid state and
different types of insulator states induced either by interaction or by
dissipation.Comment: 5 pages, 5 figure
Quantum Monte Carlo simulations of a particle in a random potential
In this paper we carry out Quantum Monte Carlo simulations of a quantum
particle in a one-dimensional random potential (plus a fixed harmonic
potential) at a finite temperature. This is the simplest model of an interface
in a disordered medium and may also pertain to an electron in a dirty metal. We
compare with previous analytical results, and also derive an expression for the
sample to sample fluctuations of the mean square displacement from the origin
which is a measure of the glassiness of the system. This quantity as well as
the mean square displacement of the particle are measured in the simulation.
The similarity to the quantum spin glass in a transverse field is noted. The
effect of quantum fluctuations on the glassy behavior is discussed.Comment: 23 pages, 7 figures included as eps files, uses RevTeX. Accepted for
publication in J. of Physics A: Mathematical and Genera
Energy average formula of photon gas rederived by using the generalized Hermann-Feynman theorem
By virtue of the generalized Hermann-Feynmam theorem and the method of
characteristics we rederive energy average formula of photon gas, this is
another useful application of the theorem.Comment: 2 page
Aharonov-Anandan Effect Induced by Spin-Orbit Interaction and Charge-Density-Waves in Mesoscopic Rings
We study the spin-dependent geometric phase effect in mesoscopic rings of
charge-density-wave(CDW) materials. When electron spin is explicitly taken into
account, we show that the spin-dependent Aharonov-Casher phase can have a
pronounced frustration effects on such CDW materials with appropriate electron
filling. We show that this frustration has observable consequences for
transport experiment. We identify a phase transition from a Peierls insulator
to metal, which is induced by spin-dependent phase interference effects.
Mesoscopic CDW materials and spin-dependent geometric phase effects, and their
interplay, are becoming attractive opportunities for exploitation with the
rapid development of modern fabrication technology.Comment: 5 pages, 6 figures, to appear in Phys.Rev.B(Aug.15, 1998
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