AN10173
Quantum honeycomb
A new structure resembling the packed hexagonal form of honeycomb has
been predicted and observed in computer models of groups of atoms that
are cooled down to a point where they lose their individual identities.
The honeycomb in this case is built not from wax but from a regular
arrangement of spinning vortices that form holes in the pancake-shaped
cloud of atoms. The wavelike behavior of such cold atom clouds has
previously been tested by splitting atomic clouds into two parts and
allowing the parts to collide, in experiments that are analogous to
Thomas Young's famous 200 year-old experiment with light. In this paper
we show that if the cloud is instead split into three parts, the pattern
of dark stripes observed by Young and cold atom researchers changes
dramatically into the lattice of swirling vortices. For cold atom clouds
to form requires them to be magnetically confined. We show that this
confinement leads the lattice to melt as the vortices interact
chaotically, clustering into structures that migrate and scatter
throughout the cloud. Computer generated movies of the lattice formation
and vortex interactions have been produced showing the whole process.
***
EP10337
JUST FOLLOW YOUR NOSE
Levy walks named after the French mathematician Paul Pierre Levy have
been observed in a bewildering range of organisms, including plankton,
honeybees, jackals and even sharks. In this paper I show how such
movement patterns will rise in predators that locate their prey by
simply following their noses. This is a significant finding because the
key to prediction and understanding lies in the elucidation of
mechanisms underlying observed patterns. The new result indicates that
Levy movements are common place but runs counter to the long-standing
notion that Levy movements arise from the execution of an optimal
searching strategy. The analysis and interpretation of animal movement
data is, however, not wholly straightforward and some of the analyses
claiming Levy walk behaviour have recently been called into question.
This issue is hotly contested, and arguments about the reliability of
methods used to test for the presence of Levy movement patterns may
continue for some time. Central to a resolution, though, is the
determination of underlying mechanisms that can give rise to such
patterns.
***
LR11055
A Non Accelerator Probe of New Physics
Motion reversal is known in physics parlance as time-reversal, as it
can be realized mathematically by changing time, t to -t. The origin
of time-reversal violation is one of the least understood of all the
profound issues in physics. The observation of an electric dipole
moment (EDM) of any fundamental particle or of a composite system like
atom or a molecule is a direct signature of the violation of
time-reversal symmetry in Nature. Open-shell atoms will have two
dominant sources of intrinsic electric dipole moments; one due to the
intrinsic EDM of its constituent electrons and the other due to a
time-reversal violating interaction between the electrons and the
nucleus mediated by spin zero particles. Despite the relentless
experimental search for EDMs in elementary particles and as well as in
composite systems for more than five decades no conclusive result has
been obtained. However, many ongoing high precision atomic EDM
experiments are aiming to achieve better detection limits, a few
orders of magnitude lower than the current experimental limits. In
order to obtain a limit for the electron EDM, one needs both the
enhancement factors (ratios of the atomic to the electron EDMs) and
the experimental atomic EDMs to a high precision. A rigorous
relativistic quantum mechanical calculation has been carried out to
predict the EDM enhancement factors for Rubidium (Rb) and Cesium (Cs)
with a sub 1% accuracy for the first time. One of the unique features
of this work is that it deals with the interplay of two very different
interactions—the long range Coulomb interaction and the short range
time-reversal violating interaction. The new results for the
enhancement factors when combined with those of the proposed non
accelerator EDM experiments on Rb and Cs when they achieve their
desired sensitivities could open up a novel direction for finding new
physics beyond the much celebrated model of particle physics, the
Standard Model, which indeed is quite significant, in the era of the
Large Hadron Collider. This could also serve as stringent tests of
many unification models, including Super-symmetry, and provide
insights into one of the most important but unresolved questions in
cosmology: the matter-antimatter asymmetry in the Universe to which we
owe our existence today.
***
LH11279B
Electronic orbital currents and polarization in Mott insulators
Systems with correlated electrons are now at the forefront of research in solid
state physics. The standard point of view is that at low energies Mott
insulators exhibit only magnetic properties, while charge degrees of freedom are
frozen because electrons are localized. But are they really localized? We
demonstrate this is not true in general: for certain spin textures on frustrated
lattices (v.g. triangular) there exist nontrivial charge effects in the ground
and lowest excited states. We show that in some cases \textit{spontaneous
circular electric currents} exist in the ground state \textit{of Mott
insulators} and are proportional to the \textit{scalar spin chirality}. Such
persistent currents can run on the surface of these insulators. We also show
that other spin structures generate \textit{spontaneous charge redistribution}.
In some cases, this charge ordering results in a net \textit{electric
polarization}. This is a novel, purely electronic mechanism for
\textit{multiferroic behavior}. We also discuss some dynamic consequences of the
effects discovered such as dipole-active "ESR" transitions, rotation of electric
polarization by spins and the possibility of having a negative refraction.
