1,180 research outputs found
High-Velocity Estimates and Inverse Scattering for Quantum N-Body Systems with Stark Effect
In an N-body quantum system with a constant electric field, by inverse
scattering, we uniquely reconstruct pair potentials, belonging to the optimal
class of short-range potentials and long-range potentials, from the
high-velocity limit of the Dollard scattering operator. We give a
reconstruction formula with an error term.Comment: In this published version we have added remarks and we have edited
the pape
Dispersive estimates for Schrodinger operators in dimensions one and three
We prove L^1 --> L^\infty estimates for linear Schroedinger equations in
dimensions one and three. The potentials are only required to satisfy some mild
decay assumptions. No regularity on the potentials is assumed.Comment: 20 pages. Corrected typos and improved explanatory remarks at the en
L^p boundedness of the wave operator for the one dimensional Schroedinger operator
Given a one dimensional perturbed Schroedinger operator H=-(d/dx)^2+V(x) we
consider the associated wave operators W_+, W_- defined as the strong L^2
limits as s-> \pm\infty of the operators e^{isH} e^{-isH_0} We prove that the
wave operators are bounded operators on L^p for all 1<p<\infty, provided
(1+|x|)^2 V(x) is integrable, or else (1+|x|)V(x) is integrable and 0 is not a
resonance. For p=\infty we obtain an estimate in terms of the Hilbert
transform. Some applications to dispersive estimates for equations with
variable rough coefficients are given.Comment: 26 page
A rigorous analysis of high order electromagnetic invisibility cloaks
There is currently a great deal of interest in the invisibility cloaks
recently proposed by Pendry et al. that are based in the transformation
approach. They obtained their results using first order transformations. In
recent papers Hendi et al. and Cai et al. considered invisibility cloaks with
high order transformations. In this paper we study high order electromagnetic
invisibility cloaks in transformation media obtained by high order
transformations from general anisotropic media. We consider the case where
there is a finite number of spherical cloaks located in different points in
space. We prove that for any incident plane wave, at any frequency, the
scattered wave is identically zero. We also consider the scattering of finite
energy wave packets. We prove that the scattering matrix is the identity, i.e.,
that for any incoming wave packet the outgoing wave packet is the same as the
incoming one. This proves that the invisibility cloaks can not be detected in
any scattering experiment with electromagnetic waves in high order
transformation media, and in particular in the first order transformation media
of Pendry et al. We also prove that the high order invisibility cloaks, as well
as the first order ones, cloak passive and active devices. The cloaked objects
completely decouple from the exterior. Actually, the cloaking outside is
independent of what is inside the cloaked objects. The electromagnetic waves
inside the cloaked objects can not leave the concealed regions and viceversa,
the electromagnetic waves outside the cloaked objects can not go inside the
concealed regions. As we prove our results for media that are obtained by
transformation from general anisotropic materials, we prove that it is possible
to cloak objects inside general crystals.Comment: The final version is now published in Journal of Physics A:
Mathematical and Theoretical, vol 41 (2008) 065207 (21 pp). Included in
IOP-Selec
On Inverse Scattering at a Fixed Energy for Potentials with a Regular Behaviour at Infinity
We study the inverse scattering problem for electric potentials and magnetic
fields in \ere^d, d\geq 3, that are asymptotic sums of homogeneous terms at
infinity. The main result is that all these terms can be uniquely reconstructed
from the singularities in the forward direction of the scattering amplitude at
some positive energy.Comment: This is a slightly edited version of the previous pape
Nonlocal ultrafast demagnetization dynamics of Co/Pt multilayers by optical field enhancement
The influence on ultrafast demagnetization dynamics of metallic nano-structured gratings deposited on thin films of magnetic Co/Pt multilayers is investigated by the time-resolved optical Kerr effect. Depending on the polarization of the pump pulse, a pronounced enhancement of the demagnetization amplitude is found. Calculation of the inhomogeneous optical field distribution due to plasmon interaction and time-dependent solutions of the coupled electron, lattice, and spin temperatures in two dimensions show good agreement with the experimental data, as well as giving evidence of non-local demagnetization dynamics due to electron diffusion.BMBF, 05K10KTB, Verbundprojekt: FSP 301 - FLASH: Nanoskopische Systeme. Teilprojekt 1.1: Universelle Experimentierkammer für Streuexperimente mit kohärenten Femtosekunden-Röntgenpulsen Multi Purpose Coherent Scattering Chamber for FLASH and XFEL 'MPscatt
Design and performance of personal cooling garments based on three-layer laminates
Personal cooling systems are mainly based on cold air or liquids circulating through a tubing system. They are weighty, bulky and depend on an external power source. In contrast, the laminate-based technology presented here offers new flexible and light weight cooling garments integrated into textiles. It is based on a three-layer composite assembled from two waterproof, but water vapor permeable membranes and a hydrophilic fabric in between. Water absorbed in the fabric will be evaporated by the body temperature resulting in cooling energy. The laminate's high adaptiveness makes it possible to produce cooling garments even for difficult anatomic topologies. The determined cooling energy of the laminate depends mainly on the environmental conditions (temperature, relative humidity, wind): heat flux at standard climatic conditions (20°C, 65% R.H., wind 5km/h) has measured 423.2±52.6W/m2, water vapor transmission resistance, R et, 10.83±0.38m2Pa/W and thermal resistance, R ct, 0.010±0.002m2K/W. Thermal conductivity, k, changed from 0.048±0.003 (dry) to 0.244±0.018W/mK (water added). The maximum fall in skin temperature, ∆T max, under the laminate was 5.7±1.2°C, taken from a 12 subject study with a thigh cooling garment during treadmill walking (23°C, 50% R.H., no wind) and a significant linear correlation (R=0.85, P=0.01) between body mass index and time to reach 67% of ∆T max could be determine
Inverse Scattering at a Fixed Quasi-Energy for Potentials Periodic in Time
We prove that the scattering matrix at a fixed quasi--energy determines
uniquely a time--periodic potential that decays exponentially at infinity. We
consider potentials that for each fixed time belong to in space. The
exponent 3/2 is critical for the singularities of the potential in space. For
this singular class of potentials the result is new even in the
time--independent case, where it was only known for bounded exponentially
decreasing potentials.Comment: In this revised version I give a more detailed motivation of the
class of potentials that I consider and I have corrected some typo
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