5,171 research outputs found
Exotic solutions in string theory
Solutions of classical string theory, correspondent to the world sheets,
mapped in Minkowsky space with a fold, are considered. Typical processes for
them are creation of strings from vacuum, their recombination and annihilation.
These solutions violate positiveness of square of mass and Regge condition. In
quantum string theory these solutions correspond to physical states |DDF>+|sp>
with non-zero spurious component.Comment: accepted in Il Nuovo Cimento A for publication in 199
Superintegrable systems with spin and second-order integrals of motion
We investigate a quantum nonrelativistic system describing the interaction of
two particles with spin 1/2 and spin 0, respectively. We assume that the
Hamiltonian is rotationally invariant and parity conserving and identify all
such systems which allow additional integrals of motion that are second order
matrix polynomials in the momenta. These integrals are assumed to be scalars,
pseudoscalars, vectors or axial vectors. Among the superintegrable systems
obtained, we mention a generalization of the Coulomb potential with scalar
potential and spin orbital one
.Comment: 32 page
Tunneling Time in the Landau-Zener Model
We give a general definition for the tunneling time in the Landau-Zener
model. This definition allows us to compute numerically the Landau-Zener
tunneling time at any sweeping rate without ambiguity. We have also obtained
analytical results in both the adiabatic limit and the sudden limit. Whenever
applicable, our results are compared to previous results and they are in good
agreement.Comment: 7pages, 9 figure
Simulation of oxygen dissociation on a six-dimensional O4 potential energy surface
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143058/1/6.2017-3487.pd
Superconductivity and magnetic order in the non-centrosymmetric Half Heusler compound ErPdBi
We report superconductivity at K and magnetic order at K in the semi-metallic noncentrosymmetric Half Heusler compound ErPdBi.
The upper critical field, , has an unusual quasi-linear temperature
variation and reaches a value of 1.6 T for . Magnetic order is
found below and is suppressed at T for . Since , the interaction of superconductivity and magnetism
is expected to give rise to a complex ground state. Moreover, electronic
structure calculations show ErPdBi has a topologically nontrivial band
inversion and thus may serve as a new platform to study the interplay of
topological states, superconductivity and magnetic order.Comment: 6 pages, 5 figures; accepted for publication in Europhysics Letter
Effective attraction between oscillating electrons in a plasmoid via acoustic waves exchange
We consider the effective interaction between electrons due to the exchange
of virtual acoustic waves in a low temperature plasma. Electrons are supposed
to participate in rapid radial oscillations forming a spherically symmetric
plasma structure. We show that under certain conditions this effective
interaction can result in the attraction between oscillating electrons and can
be important for the dynamics of a plasmoid. Some possible applications of the
obtained results to the theory of natural long-lived plasma structures are also
discussed.Comment: 14 pages in LaTeX2e, two columns, 3 eps figures; minimal changes,
some typos are corrected; version published on-line in Proc. R. Soc.
`St\"uckelberg interferometry' with ultracold molecules
We report on the realization of a time-domain `St\"uckelberg interferometer',
which is based on the internal state structure of ultracold Feshbach molecules.
Two subsequent passages through a weak avoided crossing between two different
orbital angular momentum states in combination with a variable hold time lead
to high-contrast population oscillations. This allows for a precise
determination of the energy difference between the two molecular states. We
demonstrate a high degree of control over the interferometer dynamics. The
interferometric scheme provides new possibilities for precision measurements
with ultracold molecules.Comment: 4 pages, 5 figure
On the new approach to variable separation in the time-dependent Schr\"odinger equation with two space dimensions
We suggest an effective approach to separation of variables in the
Schr\"odinger equation with two space variables. Using it we classify
inequivalent potentials such that the corresponding Schr\" odinger
equations admit separation of variables. Besides that, we carry out separation
of variables in the Schr\" odinger equation with the anisotropic harmonic
oscillator potential and obtain a complete list of
coordinate systems providing its separability. Most of these coordinate systems
depend essentially on the form of the potential and do not provide separation
of variables in the free Schr\" odinger equation ().Comment: 21 pages, latex, to appear in the "Journal of Mathematical Physics"
(1995
Landau-Zener Problem for Trilinear Hamiltonians
We consider a nonlinear version of the Landau-Zener problem, focusing on
photoassociation of a Bose-Einstein condensate as a specific example. Contrary
to the exponential rate dependence obtained for the linear problem, a series
expansion technique indicates that, when the resonance is crossed slowly, the
probability for failure of adiabaticity is directly proportional to the rate at
which the resonance is crossed.Comment: 4.5 pages, 1 figure, transferred to PRA; v2 adds discussion,
clarification, and explicit numbers for Na and 87R
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