261 research outputs found
Instanton Approach to Josephson Tunneling between Trapped Condensates
An instanton method is proposed to investigate the quantum tunneling between
two weakly-linked Bose-Einstein condensates confined in double-well potential
traps. We point out some intrinsic pathologies in the earlier treatments of
other authors and make an effort to go beyond these very simple zero order
models. The tunneling amplitude may be calculated in the Thomas-Fermi
approximation and beyond it; we find it depends on the number of the trapped
atoms, through the chemical potential. Some suggestions are given for the
observation of the Josephson oscillation and the MQST.Comment: 20 pages, Revtex4, 6 figures. Abbreviated version accepted by Eur.
Phys. J
Once again: Instanton method vs. WKB
A recent analytic test of the instanton method performed by comparing the
exact spectrum of the Lam potential (derived from representations
of a finite dimensional matrix expressed in terms of generators) with
the results of the tight--binding and instanton approximations as well as the
standard WKB approximation is commented upon. It is pointed out that in the
case of the Lam potential as well as others the WKB--related method
of matched asymptotic expansions yields the exact instanton result as a result
of boundary conditions imposed on wave functions which are matched in domains
of overlap.Comment: 10 pages, no figures. References list revised according to JHE
A (2+1)-dimensional model with instanton and sphaleron solutions
We present a model with instantons in R^3, and in its static limit a sphaleron in R^2
A (2+1)-dimensional model with instanton and sphaleron solutions
We present a (2+1)-dimensional Skyrme-like model with a symmetry-breaking potential, which in R_3 has charge -n instanton solutions, and in the static limit in R_2 a sphaleron solution
Gross-Ooguri Phase Transition at Zero and Finite Temperature: Two Circular Wilson Loop Case
In the context of correspondence the two Wilson loop correlator is
examined at both zero and finite temperatures. On the basis of an entirely
analytical approach we have found for Nambu-Goto strings the functional
relation between Euclidean action and loop
separation with integration constant , which corresponds to the
analogous formula for point-particles. The physical implications of this
relation are explored in particular for the Gross-Ooguri phase transition at
finite temperature.Comment: 13pages, 6 postscript figures, published version in JHE
N=2 String-String Duality and Holomorphic couplings
We review aspects of N=2 duality between the heterotic and the type IIA
string. After a description of string duality intended for the non-specialist
the computation of the heterotic prepotential and the function for the
ST, STU and STUV model (V a Wilson line) and the matching with the Calabi-Yau
instanton expansions are given in detail. Relations with BPS spectral sums in
various connections are pointed out.Comment: 86 pages, late
A Note on Tachyons in the System
The periodic bounce of Born-Infeld theory of -branes is derived, and the
BPS limit of infinite period is discussed as an example of tachyon
condensation. The explicit bounce solution to the Born--Infeld action is
interpreted as an unstable fundamental string stretched between the brane and
its antibrane.Comment: 10 pages, 2 figures. v2: minor changes, acknowledgement added; v3:
explanations and references added. Final version to appear in Mod. Phys.
Lett.
- …