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 $q_3$ (with mass $m_3$) is captured by the first excited state of a dimer [with individual masses and charges $(m_1,q_1$) and ($m_2,q_2=-q_1$)]. The approach leads to a universal mass-charge critical condition for the existence of three-body level condensation, ${(m_1^{-1}+m_2^{-1})}/ {[(m_1+m_2)^{-1}+m_3^{-1}]}>|{q_1}/(24 q_3)|$, 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 $s-$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