217 research outputs found
Observation of a Cooperative Radiation Force in the Presence of Disorder
Cooperative scattering of light by an extended object such as an atomic
ensemble or a dielectric sphere is fundamentally different from scattering from
many point-like scatterers such as single atoms. Homogeneous distributions tend
to scatter cooperatively, whereas fluctuations of the density distribution
increase the disorder and suppress cooperativity. In an atomic cloud, the
amount of disorder can be tuned via the optical thickness, and its role can be
studied via the radiation force exerted by the light on the atomic cloud.
Monitoring cold atoms released from a magneto-optical trap, we
present the first experimental signatures of radiation force reduction due to
cooperative scattering. The results are in agreement with an analytical
expression interpolating between the disorder and the cooperativity-dominated
regimes
Observation of subdiffusion of a disordered interacting system
We study the transport dynamics of matter-waves in the presence of disorder
and nonlinearity. An atomic Bose-Einstein condensate that is localized in a
quasiperiodic lattice in the absence of atom-atom interaction shows instead a
slow expansion with a subdiffusive behavior when a controlled repulsive
interaction is added. The measured features of the subdiffusion are compared to
numerical simulations and a heuristic model. The observations confirm the
nature of subdiffusion as interaction-assisted hopping between localized states
and highlight a role of the spatial correlation of the disorder.Comment: 8 pages, to be published on Physical Review Letter
Cooperative Scattering by Cold Atoms
We have studied the interplay between disorder and cooperative scattering for
single scattering limit in the presence of a driving laser. Analytical results
have been derived and we have observed cooperative scattering effects in a
variety of experiments, ranging from thermal atoms in an optical dipole trap,
atoms released from a dark MOT and atoms in a BEC, consistent with our
theoretical predictions.Comment: submitted for special issue of PQE 201
A practical algorithmic approach to mature aggressive B cell lymphoma diagnosis in the double/triple hit era. Selecting cases, matching clinical benefit. A position paper from the Italian Group of Haematopathology (G.I.E.)
An accurate diagnosis of clinically distinct subgroups of aggressive mature B cell lymphomas is crucial for the choice of proper treatment. Presently, precise recognition of these disorders relies on the combination of morphological, immunophenotypical, and cytogenetic/molecular features. The diagnostic workup in such situations implies the application of costly and time-consuming analyses, which are not always required, since an intensified treatment option is reasonably reserved to fit patients. The Italian Group of Haematopathology proposes herein a practical algorithm for the diagnosis of aggressive mature B cell lymphomas based on a stepwise approach, aimed to select cases deserving molecular analysis, in order to optimize time and resources still assuring the optimal management for any patient
Quantum diffusion with disorder, noise and interaction
Disorder, noise and interaction play a crucial role in the transport
properties of real systems, but they are typically hard to control and study
both theoretically and experimentally, especially in the quantum case. Here we
explore a paradigmatic problem, the diffusion of a wavepacket, by employing
ultra-cold atoms in a disordered lattice with controlled noise and tunable
interaction. The presence of disorder leads to Anderson localization, while
both interaction and noise tend to suppress localization and restore transport,
although with completely different mechanisms. When only noise or interaction
are present we observe a diffusion dynamics that can be explained by existing
microscopic models. When noise and interaction are combined, we observe instead
a complex anomalous diffusion. By combining experimental measurements with
numerical simulations, we show that such anomalous behavior can be modeled with
a generalized diffusion equation, in which the noise- and interaction-induced
diffusions enter in an additive manner. Our study reveals also a more complex
interplay between the two diffusion mechanisms in regimes of strong interaction
or narrowband noise.Comment: 11 pages, 10 figure
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