24,338 research outputs found
Propagation of a Dark Soliton in a Disordered Bose-Einstein Condensate
We consider the propagation of a dark soliton in a quasi 1D Bose-Einstein
condensate in presence of a random potential. This configuration involves
nonlinear effects and disorder, and we argue that, contrarily to the study of
stationary transmission coefficients through a nonlinear disordered slab, it is
a well defined problem. It is found that a dark soliton decays algebraically,
over a characteristic length which is independent of its initial velocity, and
much larger than both the healing length and the 1D scattering length of the
system. We also determine the characteristic decay time.Comment: 4 pages, 2 figure
Microcircuit testing and fabrication, using scanning electron microscopes
Scanning electron microscopes are used to determine both user-induced damages and manufacturing defects subtle enough to be missed by conventional light microscopy. Method offers greater depth of field and increased working distances
Three-core weakly-guiding mode-selective fibre couplers
The coupling behaviour of two-core mode-selective couplers (MSC) depends on the spatial-orientation of the asymmetric higher-order modes. This restricts their use for mode de-multiplexing in few-mode fibre networks. The use of three-core MSC's is presented as a solution
Gamow-Teller properties of the double beta-decay partners 116Cd(Sn) and 150Nd(Sm)
The two Gamow-Teller (GT) branches connecting the double-beta decay partners
(116Cd, 116Sn) and (150Nd, 150Sm) with the intermediate nuclei 116In and 150Pm
are studied within a microscopic approach based on a deformed proton-neutron
quasiparticle random-phase approximation built on a Skyrme selfconsistent mean
field with pairing correlations and spin-isospin residual forces. The results
are compared with the experimental GT strength distributions extracted from
charge-exchange reactions. Combining the two branches, the nuclear matrix
elements for the two-neutrino double-beta decay are evaluated and compared to
experimental values derived from the measured half-lives.Comment: 10 pages, 16 figure
Asymmetric quantum cloning machines in any dimension
A family of asymmetric cloning machines for -dimensional quantum states is
introduced. These machines produce two imperfect copies of a single state that
emerge from two distinct Heisenberg channels. The tradeoff between the quality
of these copies is shown to result from a complementarity akin to Heisenberg
uncertainty principle. A no-cloning inequality is derived for isotropic
cloners: if and are the depolarizing fractions associated with
the two copies, the domain in -space located
inside a particular ellipse representing close-to-perfect cloning is forbidden.
More generally, a no-cloning uncertainty relation is discussed, quantifying the
impossibility of copying imposed by quantum mechanics. Finally, an asymmetric
Pauli cloning machine is defined that makes two approximate copies of a quantum
bit, while the input-to-output operation underlying each copy is a (distinct)
Pauli channel. The class of symmetric Pauli cloning machines is shown to
provide an upper bound on the quantum capacity of the Pauli channel of
probabilities , and .Comment: 18 pages RevTeX, 3 Postscript figures; new discussion on no-cloning
uncertainty relations, several corrections, added reference
Regulating Mobile Mental Health Apps
Mobile medical apps (MMAs) are a fast‐growing category of software typically installed on personal smartphones and wearable devices. A subset of MMAs are aimed at helping consumers identify mental states and/or mental illnesses. Although this is a fledgling domain, there are already enough extant mental health MMAs both to suggest a typology and to detail some of the regulatory issues they pose. As to the former, the current generation of apps includes those that facilitate self‐assessment or self‐help, connect patients with online support groups, connect patients with therapists, or predict mental health issues. Regulatory concerns with these apps include their quality, safety, and data protection. Unfortunately, the regulatory frameworks that apply have failed to provide coherent risk‐assessment models. As a result, prudent providers will need to progress with caution when it comes to recommending apps to patients or relying on app‐generated data to guide treatment
Non-abelian cubic vertices for higher-spin fields in anti-de Sitter space
We use the Fradkin-Vasiliev procedure to construct the full set of
non-abelian cubic vertices for totally symmetric higher spin gauge fields in
anti-de Sitter space. The number of such vertices is given by a certain
tensor-product multiplicity. We discuss the one-to-one relation between our
result and the list of non-abelian gauge deformations in flat space obtained
elsewhere via the cohomological approach. We comment about the uniqueness of
Vasiliev's simplest higher-spin algebra in relation with the (non)associativity
properties of the gauge algebras that we classified. The gravitational
interactions for (partially)-massless (mixed)-symmetry fields are also
discussed. We also argue that those mixed-symmetry and/or partially-massless
fields that are described by one-form connections within the frame-like
approach can have nonabelian interactions among themselves and again the number
of nonabelian vertices should be given by tensor product multiplicities.Comment: 30 pages, v2: minor corrections, reference adde
- …