3,050 research outputs found
Charged three-body system with arbitrary masses near conformal invariance
Within an adiabatic approximation to the three-body Coulomb system, we study
the strength of the leading order conformaly invariant attractive dipole
interaction produced when a slow charged particle (with mass ) is
captured by the first excited state of a dimer [with individual masses and
charges ) and ()]. The approach leads to a universal
mass-charge critical condition for the existence of three-body level
condensation, , as well as the ratio between the geometrically scaled energy levels.
The resulting expressions can be relevant in the analysis of recent
experimental setups with charged three-body systems, such as the interactions
of excitons, or other matter-antimatter dimers, with a slow charged particle.Comment: 5 pages, 1 figure, to appear in Physical Review
Path Dependence of the Quark Nonlocal Condensate within the Instanton Model
Within the instanton liquid model, we study the dependence of the gauge
invariant two--point quark correlator on the path used to perform the color
parallel transport between two points in the Euclidean space.Comment: 4 pages, 5 figure
Two definitions of the electric polarizability of a bound system in relativistic quantum theory
For the electric polarizability of a bound system in relativistic quantum
theory, there are two definitions that have appeared in the literature. They
differ depending on whether or not the vacuum background is included in the
system. A recent confusion in this connection is clarified
Liquid-Gas phase transition in Bose-Einstein Condensates with time evolution
We study the effects of a repulsive three-body interaction on a system of
trapped ultra-cold atoms in Bose-Einstein condensed state. The stationary
solutions of the corresponding wave non-linear Schr\"{o}dinger equation
suggest a scenario of first-order liquid-gas phase transition in the condensed
state up to a critical strength of the effective three-body force. The time
evolution of the condensate with feeding process and three-body recombination
losses has a new characteristic pattern. Also, the decay time of the dense
(liquid) phase is longer than expected due to strong oscillations of the
mean-square-radius.Comment: 4 eps-figure
Validity of Feynman's prescription of disregarding the Pauli principle in intermediate states
Regarding the Pauli principle in quantum field theory and in many-body
quantum mechanics, Feynman advocated that Pauli's exclusion principle can be
completely ignored in intermediate states of perturbation theory. He observed
that all virtual processes (of the same order) that violate the Pauli principle
cancel out. Feynman accordingly introduced a prescription, which is to
disregard the Pauli principle in all intermediate processes. This ingeneous
trick is of crucial importance in the Feynman diagram technique. We show,
however, an example in which Feynman's prescription fails. This casts doubts on
the general validity of Feynman's prescription
Secalonic acid A from Pseudoparmelia sphaerospora (Nyl.) Hale and P. hypomilta (Fée) Hale (Parmeliaceae)
Secalonic acid A, a yellow pigment from fungal metabolism, was isolated from the lichens Pseudoparmelia sphaerospora and P. hypomilta. From P. sphaerospora was also isolated the depsidone hypostictic acid. The structure of these compounds was determined by spectroscopic methods and comparison with literature data
Bright solitons in quasi-one dimensional dipolar condensates with spatially modulated interactions
We introduce a model for the condensate of dipolar atoms or molecules, in
which the dipole-dipole interaction (DDI) is periodically modulated in space,
due to a periodic change of the local orientation of the permanent dipoles,
imposed by the corresponding structure of an external field (the necessary
field can be created, in particular, by means of magnetic lattices, which are
available to the experiment). The system represents a realization of a nonlocal
nonlinear lattice, which has a potential to support various spatial modes. By
means of numerical methods and variational approximation (VA), we construct
bright one-dimensional solitons in this system, and study their stability. In
most cases, the VA provides good accuracy, and correctly predicts the stability
by means of the Vakhitov-Kolokolov (VK)\ criterion. It is found that the
periodic modulation may destroy some solitons, which exist in the usual setting
with unmodulated DDI, and can create stable solitons in other cases, not
verified in the absence of modulations. Unstable solitons typically transform
into persistent localized breathers. The solitons are often mobile, with
inelastic collisions between them leading to oscillating localized modes.Comment: To appear in Physical Review A (2013). 24 pages (preprint format), 13
figure
- …