2,087 research outputs found
Deformations of coisotropic submanifolds for fibrewise entire Poisson structures
We show that deformations of a coisotropic submanifold inside a fibrewise
entire Poisson manifold are controlled by the -algebra introduced by
Oh-Park (for symplectic manifolds) and Cattaneo-Felder. In the symplectic case,
we recover results previously obtained by Oh-Park. Moreover we consider the
extended deformation problem and prove its obstructedness
Adding integrable defects to the Boussinesq equation
The purpose of this paper is to extend the store of models able to support
integrable defects by investigating the two-dimensional Boussinesq nonlinear
wave equation. As has been previously noted in many examples, insisting that a
defect contributes to energy and momentum to ensure their conservation, despite
the presence of discontinuities and the explicit breaking of translation
invariance, leads to sewing conditions relating the two fields and their
derivatives on either side of the defect. The manner in which several types of
soliton solutions to the Boussinesq equation are affected by the defect is
explored and reveals new effects that have not been observed in other
integrable systems, such as the possibility of a soliton reflecting from a
defect or of a defect decaying into one or two solitons.Comment: 28 pages, 9 figure
Integrable defects at junctions within a network
The purpose of this article is to explore the properties of integrable, purely transmitting, defects placed at the junctions of several one-dimensional domains within a network. The defect sewing conditions turn out to be quite restrictive—for example, requiring the number of domains meeting at a junction to be even—and there is a clear distinction between the behaviour of conformal and massive integrable models. The ideas are mainly developed within classical field theory and illustrated using a variety of field theory models defined on the branches of the network, including both linear and nonlinear examples
Type II defects revisited
Energy and momentum conservation in the context of a type II, purely transmitting, defect, within a single scalar relativistic two-dimensional field theory, places a severe constraint not only on the nature of the defect but also on the potentials for the scalar fields to either side of it. The constraint is of an unfamiliar type since it requires the Poisson Bracket of the defect contributions to energy and momentum with respect to the defect discontinuity and its conjugate to be balanced by the potential difference across the defect. It is shown that the only solutions to the constraint correspond to the known integrable field theories
A method for the location of noise-polluted area
This paper deals with the working out of a method suitable to locate the critical areas from an acoustic point of view inside the pertinence zones of the roads. We have applied our method to about one thousand kilometres of major roads managed by ANAS in Lombardia. The procedure is based on the coupling of a Geographic Information System (GIS) with an acoustics simulation model. In order to characterize the noise sources in the prediction software, it has been necessary to estimate in every significant section of the streets the day and night average fluxes of vehicles, the vehicle typology and their average velocity. This study started from a statistical analysis of the experimental data obtained by sound measurements and by counting the vehicle fluxes. As a result, we have obtained on a GIS the acoustics map of the whole Lombardia road network with information on where the noise limits classes are exceeded
Errors evaluation in the estimate of the noise from the road traffic
Specific algorithms together with noise data acquired during a measurement campaign, consisting of approximately 80 one-hour records, were utilized to model the noise levels of a road network. Experimental measurements were used to evaluate the reliability of the model by analyzing the differences between the measured values and the estimated ones. We think that these differences have to
be especially ascribed to an imperfect representation of the combined effects of the attenuation due to acoustic wave diffraction and the attenuation produced by the
ground effect
Risk and protective factors for meningococcal disease in adolescents: matched cohort study
Objective: To examine biological and social risk factors for
meningococcal disease in adolescents.
Design: Prospective, population based, matched cohort study
with controls matched for age and sex in 1:1 matching.
Controls were sought from the general practitioner.
Setting: Six contiguous regions of England, which represent
some 65% of the country’s population.
Participants: 15-19 year olds with meningococcal disease
recruited at hospital admission in six regions (representing 65%
of the population of England) from January 1999 to June 2000,
and their matched controls.
Methods: Blood samples and pernasal and throat swabs were
taken from case patients at admission to hospital and from
cases and matched controls at interview. Data on potential risk
factors were gathered by confidential interview. Data were
analysed by using univariate and multivariate conditional
logistic regression.
Results: 144 case control pairs were recruited (74 male (51%);
median age 17.6). 114 cases (79%) were confirmed
microbiologically. Significant independent risk factors for
meningococcal disease were history of preceding illness
(matched odds ratio 2.9, 95% confidence interval 1.4 to 5.9),
intimate kissing with multiple partners (3.7, 1.7 to 8.1), being a
university student (3.4, 1.2 to 10) and preterm birth (3.7, 1.0 to
13.5). Religious observance (0.09, 0.02 to 0.6) and
meningococcal vaccination (0.12, 0.04 to 0.4) were associated
with protection.
Conclusions: Activities and events increasing risk for
meningococcal disease in adolescence are different from in
childhood. Students are at higher risk. Altering personal
behaviours could moderate the risk. However, the development
of further effective meningococcal vaccines remains a key
public health priority
Nonadiabatic effects in the dynamics of atoms confined in a cylindric time-orbiting-potential magnetic trap
In a time-orbiting-potential magnetic trap the neutral atoms are confined by
means of an inhomogeneous magnetic field superimposed to an uniform rotating
one. We perform an analytic study of the atomic motion by taking into account
the nonadiabatic effects arising from the spin dynamics about the local
magnetic field. Geometric-like magnetic-fields determined by the Berry's phase
appear within the quantum description. The application of a variational
procedure on the original quantum equation leads to a set of dynamical
evolution equations for the quantum average value of the position operator and
of the spin variables. Within this approximation we derive the
quantum-mechanical ground state configuration matching the classical adiabatic
solution and perform some numerical simulations.Comment: 12 pages, 4 figure
The quantum non-linear Schrodinger model with point-like defect
We establish a family of point-like impurities which preserve the quantum
integrability of the non-linear Schrodinger model in 1+1 space-time dimensions.
We briefly describe the construction of the exact second quantized solution of
this model in terms of an appropriate reflection-transmission algebra. The
basic physical properties of the solution, including the space-time symmetry of
the bulk scattering matrix, are also discussed.Comment: Comments on the integrability and the impurity free limit adde
Spatial and temporal characterization of a Bessel beam produced using a conical mirror
We experimentally analyze a Bessel beam produced with a conical mirror,
paying particular attention to its superluminal and diffraction-free
properties. We spatially characterized the beam in the radial and on-axis
dimensions, and verified that the central peak does not spread over a
propagation distance of 73 cm. In addition, we measured the superluminal phase
and group velocities of the beam in free space. Both spatial and temporal
measurements show good agreement with the theoretical predictions.Comment: 5 pages, 6 figure
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