1,050 research outputs found
Condensation of Excitons in Cu2O at Ultracold Temperatures: Experiment and Theory
We present experiments on the luminescence of excitons confined in a
potential trap at milli-Kelvin bath temperatures under cw-excitation. They
reveal several distinct features like a kink in the dependence of the total
integrated luminescence intensity on excitation laser power and a bimodal
distribution of the spatially resolved luminescence. Furthermore, we discuss
the present state of the theoretical description of Bose-Einstein condensation
of excitons with respect to signatures of a condensate in the luminescence. The
comparison of the experimental data with theoretical results with respect to
the spatially resolved as well as the integrated luminescence intensity shows
the necessity of taking into account a Bose-Einstein condensed excitonic phase
in order to understand the behaviour of the trapped excitons.Comment: 41 pages, 23 figure
D-Branes on ALE Spaces and the ADE Classification of Conformal Field Theories
The spectrum of D2-branes wrapped on an ALE space of general ADE type is
determined, by representing them as boundary states of N=2 superconformal
minimal models. The stable quantum states have RR charges which precisely
represent the gauge fields of the corresponding Lie algebra. This provides a
simple and direct physical link between the ADE classification of N=2
superconformal field theories, and the corresponding root systems. An affine
extension of this structure is also considered, whose boundary states represent
the D2-branes plus additional D0-branes.Comment: 12p, harvmac, minor corrrections and ref adde
Holonomy from wrapped branes
Compactifications of M-theory on manifolds with reduced holonomy arise as the
local eleven-dimensional description of D6-branes wrapped on supersymmetric
cycles in manifolds of lower dimension with a different holonomy group.
Whenever the isometry group SU(2) is present, eight-dimensional gauged
supergravity is a natural arena for such investigations. In this paper we use
this approach and review the eleven dimensional description of D6-branes
wrapped on coassociative 4-cycles, on deformed 3-cycles inside Calabi-Yau
threefolds and on Kahler 4-cycles.Comment: 1+8 pages, Latex. Proceedings of the Leuven workshop, 2002. v2:
Corrected typos in equations (4)-(8
First Dark Matter Search Results from a Surface Run of the 10-L DMTPC Directional Dark Matter Detector
The Dark Matter Time Projection Chamber (DMTPC) is a low pressure (75 Torr
CF4) 10 liter detector capable of measuring the vector direction of nuclear
recoils with the goal of directional dark matter detection. In this paper we
present the first dark matter limit from DMTPC. In an analysis window of 80-200
keV recoil energy, based on a 35.7 g-day exposure, we set a 90% C.L. upper
limit on the spin-dependent WIMP-proton cross section of 2.0 x 10^{-33} cm^{2}
for 115 GeV/c^2 dark matter particle mass.Comment: accepted for publication in Physics Letters
Coset Construction of Gravitational Instantons
We study Ricci-flat metrics on non-compact manifolds with the exceptional
holonomy . We concentrate on the metrics which are defined on
. If the homogeneous coset spaces have weak ,
SU(3) holonomy, the manifold may have
holonomy metrics. Using the formulation with vector fields, we investigate the
metrics with holonomy on . We have found the explicit volume-preserving vector fields on
these manifold using the elementary coordinate parameterization. This
construction is essentially dual to solving the generalized self-duality
condition for spin connections. We present most general differential equations
for each coset. Then, we develop the similar formulation in order to calculate
metrics with holonomyComment: 29 pages, no figure; (v2) Errors are corrected ; (v3) Some
explanations are added. More general differential equations for SU(3)/U(1)
coset are give
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