1,054 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
Batalin-Vilkovisky field-antifield quantisation of fluctuations around classical field configurations
The Lagrangian field-antifield formalism of Batalin and Vilkovisky (BV) is
used to investigate the application of the collective coordinate method to
soliton quantisation. It is shown how Noether identities and local symmetries
of the Lagrangian arise when collective coordinates are introduced in order to
avoid divergences related to zero modes. This transformation to collective and
fluctuation degrees of freedom is interpreted as a canonical transformation in
the symplectic field-antifield space which induces a time-local gauge symmetry.
Separating the corresponding Lagrangian path integral of the BV scheme in
lowest order into harmonic quantum fluctuations and a free motion of the
collective coordinate with the classical mass of the soliton, we show how the
BV approach clarifies the relation between zero modes, collective coordinates,
gauge invariance and the center-of-mass motion of classical solutions in
quantum fields. Finally, we apply the procedure to the reduced nonlinear O(3)
sigma-model.Comment: 29 pages, LaTex, no figure
Tunneling of Born-Infeld Strings to D2-Branes
A Born-Infeld theory describing a D2-brane coupled to a 4-form RR field
strength is considered, and the general solutions of the static and Euclidean
time equations are derived and discussed. The period of the bounce solutions is
shown to allow a consideration of tunneling and quantum-classical transitions
in the sphaleron region. The order of such transitions, depending on the
strength of the RR field strength, is determined. A criterion is then derived
to confirm these findings.Comment: 20 pages, 7 postscript figures, will appear in NP
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
Modern spatial sea-ice variability in the central Arctic Ocean and adjacent marginal seas: Reconstruction from biomarker data
Sea ice is a fundamental component of Earth’s climate system, contributing to heat reduction (albedo) and deep-water formation. In order to understand processes controlling the recent dramatic reduction in Arctic sea-ice cover, it is essential to determine spatial and temporal changes in sea-ice occurrence and its natural variability in the present and past. Here, we present biomarker data from surface sediments and related to the modern spatial (seasonal) sea-ice variability in the central Arctic Ocean and adjacent marginal seas (i.e., Bering, Chukchi, Laptev and Kara seas) as well as the Fram Strait/Yermak Plateau area. We determined concentrations of the sea-ice diatom-derived biomarker “IP25″ (highly-branched isoprenoid – HBI – with 25 carbon atom; Belt et al., 2007), phytoplankton-derived biomarkers (brassicasterol and dinosterol) and terrigenous biomarkers (campesterol and Î_-sitosterol) to estimate recent sea-ice conditions in the study area. A combined phytoplankton-IP25 biomarker approach (“PIP25 index”; Müller et al., 2009, 2011) is used to reconstruct the modern sea-ice distribution more quantitatively. In addition, the distribution pattern of HBI-diene/IP25 ratios has been determined to test a proposed relationship between the diene/IP25 ratio and sea-surface temperatures in Arctic marginal ice-zone environments (Fahl and Stein, 2012; Stein et al., 2012). Assessment of sea-ice conditions based on these biomarker data display that a quite stable marginal ice zone exists along the continental shelf/slope of Kara and Laptev seas during summer/early fall. Elevated IP25 as well as brassicasterol and dinosterol values occurring in the central Kara and Laptev seas are related to extended sea-ice-cover and higher primary production (close to ice-edge situation). Further to the north and the central Arctic Ocean, lower IP25 and phytoplankton biomarker concentrations point to a more close sea-ice cover situation
BRST invariant approach to quantum mechanical tunneling
A new approach with BRST invariance is suggested to cure the degeneracy
problem of ill defined path integrals in the path-integral calculationof
quantum mechanical tunneling effects in which the problem arises due to the
occurrence of zero modes. The Faddeev-Popov procedure is avoided and the
integral over the zero mode is transformed in a systematic way into a well
defined integral over instanton positions. No special procedure has to be
adopted as in the Faddeev-Popov method in calculating the Jacobian of the
transformation. The quantum mechanical tunneling for the Sine-Gordon potential
is used as a test of the method and the width of the lowest energy band is
obtained in exact agreement with that of WKB calculations.Comment: 9 pages, LaTe
Winding Number Transitions in the Mottola-Wipf Model on a Circle
Winding number transitions from quantum to classical behavior are studied in
the case of the {1+1} dimensional Mottola-Wipf model with the space coordinate
on a circle for exploring the possibility of obtaining transitions of second
order. The model is also studied as a prototype theory which demonstrates the
procedure of such investigations. In the model at hand we find that even on a
circle the transitions remain those of first order.Comment: 17pages + 5 ps figures, final version to appear in Nucl. Phys.
AdS/CFT Correspondence, Poincar\'{e} Vacuum State and Greybody Factors in BTZ Black Holes
The greybody factors in BTZ black holes are evaluated from 2D CFT in the
spirit of AdS/CFT correspondence. The initial state of black holes in the
usual calculation of greybody factors by effective CFT is described as
Poincar\'{e} vacuum state in 2D CFT. The normalization factor which cannot be
fixed in the effective CFT without appealing to string theory is shown to be
determined by the normalized bulk-to-boundary Green function. The relation
among the greybody factors in different dimensional black holes is exhibited.
Two kinds of operators which couple with the boundary
value of massless scalar field are discussed.Comment: 13 pages, Latex, no figures, minor corrections, to appear in Phys.
Lett.
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