248 research outputs found
Semilinear response for the heating rate of cold atoms in vibrating traps
The calculation of the heating rate of cold atoms in vibrating traps requires
a theory that goes beyond the Kubo linear response formulation. If a strong
"quantum chaos" assumption does not hold, the analysis of transitions shows
similarities with a percolation problem in energy space. We show how the
texture and the sparsity of the perturbation matrix, as determined by the
geometry of the system, dictate the result. An improved sparse random matrix
model is introduced: it captures the essential ingredients of the problem, and
leads to a generalized variable range hopping picture.Comment: 6 pages, 6 figures, improved version to be published in Europhysics
Letter
The Role of CP violation in D0 anti-D0 Mixing
In current searches for D0 anti-D0 mixing, the time evolution of
``wrong-sign'' decays is used to distinguish between a potential mixing signal
and the dominant background from doubly-Cabibbo-suppressed decays. A term
proportional to in the expression for the time evolution is often
neglected in theoretical discussions and experimental analyses of these
processes. We emphasize that, in general, this term does not vanish even in the
case of CP invariance. Furthermore, CP invariance is likely to be violated if
the rate of D0 anti-D0 mixing is close to the experimental bound. The
consequence of either of these two facts is that the strongest existing
measured bound is not applicable for constraining New Physics.Comment: 14 pages, uuencoded gzip-compressed postscript (84 kB
On the absence of the electrostriction force in dilute clouds of cold atoms
The momentum of light in a medium and the mechanisms of momentum transfer
between light and dielectrics have long been the topic of controversies and
confusion. We discuss here the problem of momentum transfers that follow the
refraction of light by dilute, inhomogeneous ensembles of ultra-cold atoms. We
show experimentally and theoretically that the refraction of light rays by a
dilute gas does not entail momentum transfers to first order in the light-atom
coupling coefficient, in contradiction with the work reported in Matzliah et
al. Phys. Rev. Lett. 119, 189902 (2017).Comment: 4 pages, 3 figure
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