716 research outputs found
Nanofiber-based optical trapping of cold neutral atoms
We present experimental techniques and results related to the optimization
and characterization of our nanofiber-based atom trap [Vetsch et al., Phys.
Rev. Lett. 104, 203603 (2010)]. The atoms are confined in an optical lattice
which is created using a two-color evanescent field surrounding the optical
nanofiber. For this purpose, the polarization state of the trapping light
fields has to be properly adjusted. We demonstrate that this can be
accomplished by analyzing the light scattered by the nanofiber. Furthermore, we
show that loading the nanofiber trap from a magneto-optical trap leads to
sub-Doppler temperatures of the trapped atomic ensemble and yields a
sub-Poissonian distribution of the number of trapped atoms per trapping site
Deformed vortices in (4+1)-dimensional Einstein-Yang-Mills theory
We study vortex-type solutions in a (4+1)-dimensional
Einstein-Yang-Mills-SU(2) model. Assuming all fields to be independent on the
extra coordinate, these solutions correspond in a four dimensional picture to
axially symmetric multimonopoles, respectively monopole-antimonopole solutions.
By boosting the five dimensional purely magnetic solutions we find new
configurations which in four dimensions represents rotating regular nonabelian
solutions with an additional electric charge.Comment: 11 pages, including 5 eps files; reference added, discussion
extended; typos correcte
Self-dual instanton and nonself-dual instanton-antiinstanton solutions in Yang-Mills theory
Subjecting the SU(2) Yang--Mills system to azimuthal symmetries in both the
and the planes results in a residual subsystem described by a U(1)
Higgs like model with two complex scalar fields on the quarter plane. The
resulting instantons are labeled by integers with topological
charges . Solutions are constructed numerically for
and a range of . It is found that only the
instantons are self-dual, the configurations describing composite
instanton-antiinstanton lumps.Comment: 12 pages, 5 Figure
Self-interactions in a topological BF-type model in D=5
All consistent interactions in five spacetime dimensions that can be added to
a free BF-type model involving one scalar field, two types of one-forms, two
sorts of two-forms, and one three-form are investigated by means of deforming
the solution to the master equation with the help of specific cohomological
techniques. The couplings are obtained on the grounds of smoothness, locality,
(background) Lorentz invariance, Poincar\'{e} invariance, and the preservation
of the number of derivatives on each field.Comment: LaTeX, 57 pages, final version, matching the published pape
Nonabelian solutions in N=4, D=5 gauged supergravity
We consider static, nonabelian solutions in N=4, D=5 Romans' gauged
supergravity model. Numerical arguments are presented for the existence of
asymptotically anti-de Sitter configurations in the version of the
theory, with a dilaton potential presenting a stationary point. Considering the
version of the theory with a Liouville dilaton potential, we look for
configurations with unusual topology. A new exact solution is presented, and a
counterterm method is proposed to compute the mass and action.Comment: 15 pages, 4 figure
New nonuniform black string solutions
We present nonuniform vacuum black strings in five and six spacetime
dimensions. The conserved charges and the action of these solutions are
computed by employing a quasilocal formalism. We find qualitative agreement of
the physical properties of nonuniform black strings in five and six dimensions.
Our results offer further evidence that the black hole and the black string
branches merge at a topology changing transition. We generate black string
solutions of the Einstein-Maxwell-dilaton theory by using a Harrison
transformation. We argue that the basic features of these solutions can be
derived from those of the vacuum black string configurations.Comment: 30 pages, 12 figures; v2: more details on numerical method,
references added; v3: references added, minor revisions, version accepted by
journa
Rotating nonuniform black string solutions
We explore via linearized perturbation theory the Gregory-Laflamme
instability of rotating black strings with equal magnitude angular momenta. Our
results indicate that the Gregory-Laflamme instability persists up to
extremality for all even dimensions between six and fourteen. We construct
rotating nonuniform black strings with two equal magnitude angular momenta in
six dimensions. We see a first indication for the occurrence of a topology
changing transition, associated with such rotating nonuniform black strings.
Charged nonuniform black string configurations in heterotic string theory are
also constructed by employing a solution generation technique.Comment: 36 pages, 10 figures, final versio
On the generalized Freedman-Townsend model
Consistent interactions that can be added to a free, Abelian gauge theory
comprising a finite collection of BF models and a finite set of two-form gauge
fields (with the Lagrangian action written in first-order form as a sum of
Abelian Freedman-Townsend models) are constructed from the deformation of the
solution to the master equation based on specific cohomological techniques.
Under the hypotheses of smoothness in the coupling constant, locality, Lorentz
covariance, and Poincare invariance of the interactions, supplemented with the
requirement on the preservation of the number of derivatives on each field with
respect to the free theory, we obtain that the deformation procedure modifies
the Lagrangian action, the gauge transformations as well as the accompanying
algebra. The interacting Lagrangian action contains a generalized version of
non-Abelian Freedman-Townsend model. The consistency of interactions to all
orders in the coupling constant unfolds certain equations, which are shown to
have solutions.Comment: LaTeX, 62 page
Hamiltonian BRST deformation of a class of n-dimensional BF-type theories
Consistent Hamiltonian interactions that can be added to an abelian free
BF-type class of theories in any n greater or equal to 4 spacetime dimensions
are constructed in the framework of the Hamiltonian BRST deformation based on
cohomological techniques. The resulting model is an interacting field theory in
higher dimensions with an open algebra of on-shell reducible first-class
constraints. We argue that the Hamiltonian couplings are related to a natural
structure of Poisson manifold on the target space.Comment: 27 pages, uses JHEP3.cl
Quantum effects in a rotating spacetime
The behavior of a arbitrary coupled quantum scalar field is studied in the
background of the G\"odel spacetime. Closed forms are derived for the effective
action and the vacuum expectation value of quadratic field fluctuations by
using -function regularization. Based on these results, we argue that
causality violation presented in this spacetime can not be removed by quantum
effects.Comment: 17 pages, LaTe
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