104 research outputs found
Near-Horizon Geometry and Warped Conformal Symmetry
We provide boundary conditions for three-dimensional gravity including
boosted Rindler spacetimes, representing the near-horizon geometry of
non-extremal black holes or flat space cosmologies. These boundary conditions
force us to make some unusual choices, like integrating the canonical boundary
currents over retarded time and periodically identifying the latter. The
asymptotic symmetry algebra turns out to be a Witt algebra plus a twisted u(1)
current algebra with vanishing level, corresponding to a twisted warped CFT
that is qualitatively different from the ones studied so far in the literature.
We show that this symmetry algebra is related to BMS by a twisted Sugawara
construction and exhibit relevant features of our theory, including matching
micro- and macroscopic calculations of the entropy of zero-mode solutions. We
confirm this match in a generalization to boosted Rindler-AdS. Finally, we show
how Rindler entropy emerges in a suitable limit.Comment: 26 pages + appendices, v2: added refs. & comments and corrected
T-independent part of free energy for Rindler-Ad
Non-destructive interferometric characterization of an optical dipole trap
A method for non-destructive characterization of a dipole trapped atomic
sample is presented. It relies on a measurement of the phase-shift imposed by
cold atoms on an optical pulse that propagates through a free space
Mach-Zehnder interferometer. Using this technique we are able to determine,
with very good accuracy, relevant trap parameters such as the atomic sample
temperature, trap oscillation frequencies and loss rates. Another important
feature is that our method is faster than conventional absorption or
fluorescence techniques, allowing the combination of high-dynamical range
measurements and a reduced number of spontaneous emission events per atom.Comment: 9 pages, 6 figures, submitted to PR
- …