2,521 research outputs found
Comment on "Relativistic Effects of Light in Moving Media with Extremely Low Group Velocity"
In [cond-mat/9906332; Phys. Rev. Lett. 84, 822 (2000)] and [physics/9906038;
Phys. Rev. A 60, 4301 (1999)] Leonhardt and Piwnicki have presented an
interesting analysis of how to use a flowing dielectric fluid to generate a
so-called "optical black hole". Qualitatively similar phenomena using
acoustical processes have also been much investigated. Unfortunately there is a
subtle misinterpretation in the Leonhardt-Piwnicki analysis regarding these
"optical black holes": While it is clear that "optical black holes" can
certainly exist as theoretical constructs, and while the experimental prospects
for actually building them in the laboratory are excellent, the particular
model geometries that Leonhardt and Piwnicki write down as alleged examples of
"optical black holes" are in fact not black holes at all.Comment: one page comment, uses ReV_TeX 3; discussion clarified; basic
physical results unaltere
Lifting a Conformal Field Theory from D-Dimensional Flat Space to (D+1)-Dimensional Ads Space
A quantum field theory on Anti-de-Sitter space can be constructed from a
conformal field theory on its boundary Minkowski space by an inversion of the
holographic mapping. To do this the conformal field theory must satisfy certain
constraints. The structure of operator product expansions is carried over to
AdS space. We show that this method yields a higher spin field theory HS(4)
from the minimal conformal O(N) sigma model in three dimensions. For these
models AdS/CFT correspondence is hereby proved to second order in the coupling
constant.Comment: Latex file, 19 pages; one section added, 3 references added, typos
correcte
Partial Transmutation of Singularities in Optical Instruments
Some interesting optical instruments such as the Eaton lens and the Invisible
Sphere require singularities of the refractive index for their implementation.
We show how to transmute those singularities into harmless topological defects
in anisotropic media without the need for anomalous material properties
Non-Gaussian states from continuous-wave Gaussian light sources
We present a general analysis of the state obtained by subjecting the output
from a continuous-wave (cw) Gaussian field to non-Gaussian measurements. The
generic multimode state of cw Gaussian fields is characterized by an infinite
dimensional covariance matrix involving the noise correlations of the source.
Our theory extracts the information relevant for detection within specific
temporal output modes from these correlation functions . The formalism is
applied to schemes for production of non-classical light states from a squeezed
beam of light
Fluorescence microscopy for the characterization of structural integrity
The absorption characteristics of light and the optical technique of fluorescence microscopy for enhancing metallographic interpretation are presented. Characterization of thermally sprayed coatings by optical microscopy suffers because of the tendency for misidentification of the microstructure produced by metallographic preparation. Gray scale, in bright field microscopy, is frequently the only means of differentiating the actual structural details of porosity, cracking, and debonding of coatings. Fluorescence microscopy is a technique that helps to distinguish the artifacts of metallographic preparation (pullout, cracking, debonding) from the microstructure of the specimen by color contrasting structural differences. Alternative instrumentation and the use of other dye systems are also discussed. The combination of epoxy vacuum infiltration with fluorescence microscopy to verify microstructural defects is an effective means to characterize advanced materials and to assess structural integrity
Composite fields, generalized hypergeometric functions and the symmetry in the AdS/CFT correspondence
We discuss the concept of composite fields in flat CFT as well as in the
context of AdS/CFT. Furthermore we show how to represent Green functions using
generalized hypergeometric functions and apply these techniques to four-point
functions. Finally we prove an identity of symmetry for four-point
functions.Comment: 12 pages, 2 figure
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