21,109 research outputs found
On closing for flows on 2-manifolds
For some full measure subset B of the set of iet's (i.e. interval exchange
transformations) the following is satisfied: Let X be a , , vector field, with finitely many singularities, on a compact
orientable surface M. Given a nontrivial recurrent point of X, the
holonomy map around p is semi-conjugate to an iet If
then there exists a vector field Y, arbitrarily close to X, in
the topology, such that Y has a closed trajectory passing through p.Comment: 7 pages, 1 figur
Observation of the Quantum Zeno and Anti-Zeno effects in an unstable system
We report the first observation of the Quantum Zeno and Anti-Zeno effects in
an unstable system. Cold sodium atoms are trapped in a far-detuned standing
wave of light that is accelerated for a controlled duration. For a large
acceleration the atoms can escape the trapping potential via tunneling.
Initially the number of trapped atoms shows strong non-exponential decay
features, evolving into the characteristic exponential decay behavior. We
repeatedly measure the number of atoms remaining trapped during the initial
period of non-exponential decay. Depending on the frequency of measurements we
observe a decay that is suppressed or enhanced as compared to the unperturbed
system.Comment: 4 pages, 5 figures, submitted to PR
A statistical approach to identify superluminous supernovae and probe their diversity
We investigate the identification of hydrogen-poor superluminous supernovae
(SLSNe I) using a photometric analysis, without including an arbitrary
magnitude threshold. We assemble a homogeneous sample of previously classified
SLSNe I from the literature, and fit their light curves using Gaussian
processes. From the fits, we identify four photometric parameters that have a
high statistical significance when correlated, and combine them in a parameter
space that conveys information on their luminosity and color evolution. This
parameter space presents a new definition for SLSNe I, which can be used to
analyse existing and future transient datasets. We find that 90% of previously
classified SLSNe I meet our new definition. We also examine the evidence for
two subclasses of SLSNe I, combining their photometric evolution with
spectroscopic information, namely the photospheric velocity and its gradient. A
cluster analysis reveals the presence of two distinct groups. `Fast' SLSNe show
fast light curves and color evolution, large velocities, and a large velocity
gradient. `Slow' SLSNe show slow light curve and color evolution, small
expansion velocities, and an almost non-existent velocity gradient. Finally, we
discuss the impact of our analyses in the understanding of the powering engine
of SLSNe, and their implementation as cosmological probes in current and future
surveys.Comment: 16 pages, 9 figures, accepted by ApJ on 23/01/201
Correcting symmetry imperfections in linear multipole traps
Multipole radio-frequency traps are central to collisional experiments in
cryogenic environments. They also offer possibilities to generate new type of
ion crystals topologies and in particular the potential to create infinite
1D/2D structures: ion rings and ion tubes. However, multipole traps have also
been shown to be very sensitive to geometrical misalignment of the trap rods,
leading to additional local trapping minima. The present work proposes a method
to correct non-ideal potentials, by modifying the applied radio-frequency
amplitudes for each trap rod. This approach is discussed for the octupole trap,
leading to the restitution of the ideal Mexican-Hat-like pseudo-potential,
expected in multipole traps. The goodness of the compensation method is
quantified in terms of the choice of the diagnosis area, the residual trapping
potential variations, the required adaptation of the applied radio-frequency
voltage amplitudes, and the impact on the trapped ion structures. Experimental
implementation for macroscopic multipole traps is also discussed, in order to
propose a diagnostic method with respect to the resolution and stability of the
trap drive. Using the proposed compensation technique, we discuss the
feasibility of generating a homogeneous ion ring crystal, which is a measure of
quality for the obtained potential well
Fast accumulation of ions in a dual trap
Transporting charged particles between different traps has become an
important feature in high-precision spectroscopy experiments of different
types. In many experiments in atomic and molecular physics, the optical probing
of the ions is not carried out at the same location as the creation or state
preparation. In our double linear radio-frequency trap, we have implemented a
fast protocol allowing to shuttle large ion clouds very efficiently between
traps, in times shorter than a millisecond. Moreover, our shuttling protocol is
a one-way process, allowing to add ions to an existing cloud without loss of
the already trapped sample. This feature makes accumulation possible, resulting
in the creation of large ion clouds. Experimental results show, that ion clouds
of large size are reached with laser-cooling, however, the described mechanism
does not rely on any cooling process
A Closing Lemma for a Class of Symplectic Diffeomorphisms
We prove a closing lemma for a class of partially hyperbolic symplectic
diffeomorphisms. We show that for a generic symplectic diffeomorphism, , with two dimensional center and close to a product map, the set
of all periodic points is dense
Nongauge bright soliton of the nonlinear Schrodinger (NLS) equation and a family of generalized NLS equations
We present an approach to the bright soliton solution of the NLS equation
from the standpoint of introducing a constant potential term in the equation.
We discuss a `nongauge' bright soliton for which both the envelope and the
phase depend only on the traveling variable. We also construct a family of
generalized NLS equations with solitonic sech^p solutions in the traveling
variable and find an exact equivalence with other nonlinear equations, such as
the Korteveg-de Vries and Benjamin-Bona-Mahony equations when p=2Comment: ~4 pages, 3 figures, 16 references, published versio
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