1,447 research outputs found
Positive-P and Wigner representations for quantum-optical systems with nonorthogonal modes
We generalize the basic concepts of the positive-P and Wigner representations to unstable quantum-optical systems that are based on nonorthogonal quasimodes. This lays the foundation for a quantum description of such systems, such as, for example an unstable cavity laser. We compare both representations by calculating the tunneling times for an unstable resonator optical parametric oscillator
Friction of the surface plasmon by high-energy particle-hole pairs: Are memory effects important?
We show that the dynamics of the surface plasmon in metallic nanoparticles
damped by its interaction with particle-hole excitations can be modelled by a
single degree of freedom coupled to an environment. In this approach, the fast
decrease of the dipole matrix elements that couple the plasmon to particle-hole
pairs with the energy of the excitation allows a separation of the Hilbert
space into low- and high-energy subspaces at a characteristic energy that we
estimate. A picture of the spectrum consisting of a collective excitation built
from low-energy excitations which interacts with high-energy particle-hole
states can be formalised. The high-energy excitations yield an approximate
description of a dissipative environment (or "bath") within a finite confined
system. Estimates for the relevant timescales establish the Markovian character
of the bath dynamics with respect to the surface plasmon evolution for
nanoparticles with a radius larger than about 1 nm.Comment: 8 pages, 1 figure; see also cond-mat/070372
A mutational hot spot in keratin 10 (KRT 10) in patients with epidermolytic hyperkeratosis
Epidermolytic hyperkeratosis (EHK), (bullous congenital ichthyosiform erythroderma), is an autosomal dominant human skin disorder. Recently, we and others have described mutations in keratins 1 and 10 (K1 and K10) in patients with this disease. Structure-function models predict that these mutations would impair normal filament assembly and function. We have extended our earlier studies to include 8 more incidences of EHK. In half of these families, we were unable to locate a mutation within the rod domains of either K1 or K10. However, polymorphic restriction site and sequence analysis of the other families revealed a mutational hot spot within the 1A alpha-helical segment of K10. These involve Arginine to Histidine, Arginine to Cysteine and Arginine to Leucine substitutions at residue 10 of the rod domain. Interestingly, mutations in the corresponding Arginine residue in keratin K14 have been identified in patients with epidermolysis bullosa simplex. The large number of mutations found at this position in both keratins K10 and K14 suggests that other epithelia cell disorders will be discovered that are caused by the corresponding mutation in related type I keratin gene
Field quantization for open optical cavities
We study the quantum properties of the electromagnetic field in optical
cavities coupled to an arbitrary number of escape channels. We consider both
inhomogeneous dielectric resonators with a scalar dielectric constant
and cavities defined by mirrors of arbitrary shape. Using
the Feshbach projector technique we quantize the field in terms of a set of
resonator and bath modes. We rigorously show that the field Hamiltonian reduces
to the system--and--bath Hamiltonian of quantum optics. The field dynamics is
investigated using the input--output theory of Gardiner and Collet. In the case
of strong coupling to the external radiation field we find spectrally
overlapping resonator modes. The mode dynamics is coupled due to the damping
and noise inflicted by the external field. For wave chaotic resonators the mode
dynamics is determined by a non--Hermitean random matrix. Upon including an
amplifying medium, our dynamics of open-resonator modes may serve as a starting
point for a quantum theory of random lasing.Comment: 16 pages, added references, corrected typo
Tourism policy and destination marketing in developing countries: the chain of influence
Tourism marketers including destination marketing organisations (DMOs) and international tour operators play a pivotal role in destination marketing, especially in creating destination images. These images, apparent in tourist brochures, are designed to influence tourist decision-making and behaviour. This paper proposes the concept of a “chain of influence” in destination marketing and image-making, suggesting that the content of marketing materials is influenced by the priorities of those who design these materials, e.g. tour operators and DMOs. A content analysis of 2,000 pictures from DMO and tour operator brochures revealed synergies and divergence between these marketers. The brochure content was then compared to the South African tourism policy, concluding that the dominant factor in the chain of influence in the South African context is in fact its organic image
Quantum Statistics of Surface Plasmon Polaritons in Metallic Stripe Waveguides
Single surface plasmon polaritons are excited using photons generated via
spontaneous parametric down-conversion. The mean excitation rates, intensity
correlations and Fock state populations are studied. The observed dependence of
the second order coherence in our experiment is consistent with a linear
uncorrelated Markovian environment in the quantum regime. Our results provide
important information about the effect of loss for assessing the potential of
plasmonic waveguides for future nanophotonic circuitry in the quantum regime.Comment: 21 pages, 6 figures, published in Nano Letters, publication date
(web): March 27 (2012
Light scattering from disordered overlayers of metallic nanoparticles
We develop a theory for light scattering from a disordered layer of metal
nanoparticles resting on a sample. Averaging over different disorder
realizations is done by a coherent potential approximation. The calculational
scheme takes into account effects of retardation, multipole excitations, and
interactions with the sample. We apply the theory to a system similar to the
one studied experimentally by Stuart and Hall [Phys. Rev. Lett. {\bf 80}, 5663
(1998)] who used a layered Si/SiO/Si sample. The calculated results agree
rather well with the experimental ones. In particular we find conspicuous
maxima in the scattering intensity at long wavelengths (much longer than those
corresponding to plasmon resonances in the particles). We show that these
maxima have their origin in interference phenomena in the layered sample.Comment: 19 pages, 12 figure
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