8,046 research outputs found
Nonlinear optical effects in artificial materials
We consider some nonlinear phenomena in metamaterials with negative
refractive index properties. Our consideration includes a survey of previously
known results as well as identification of the phenomena that are important for
applications of this new field. We focus on optical behavior of thin films as
well as multi-wave interactions.Comment: 22 pages, no figures. Submitted in book "Nonlinear waves in complex
systems: energy flow and geometry
Coherent Amplification of Optical Pulses in Metamaterials
In this paper we theoretically study propagation of steady state ultrashort
pulse in dissipative medium. We considered two cases (i) medium consists of
lossy metallic nanostructures embedded into a gain material and (ii) the gain
material is embedded directly into the nanostructures. We found the shape and
velocity of an optical pulse coupled with the polarization wave.Comment: 9 pages, 5 figures, submitted to IEEE Tran
Convection-Dominated Accretion Flows
Non-radiating, advection-dominated, accretion flows are convectively
unstable. We calculate the two-dimensional (r-theta) structure of such flows
assuming that (1) convection transports angular momentum inwards, opposite to
normal viscosity and (2) viscous transport by other mechanisms (e.g., magnetic
fields) is weak (alpha << 1). Under such conditions convection dominates the
dynamics of the accretion flow and leads to a steady state structure that is
marginally stable to convection. We show that the marginally stable flow has a
constant temperature and rotational velocity on spherical shells, a net flux of
energy from small to large radii, zero net accretion rate, and a radial density
profile proportional to r^{-1/2}, flatter than the r^{-3/2} profile
characteristic of spherical accretion flows. This solution accurately describes
the full two-dimensional structure of recent axisymmetric numerical simulations
of advection-dominated accretion flows.Comment: final version accepted by ApJ; discussion expanded, references adde
Cliffordons
At higher energies the present complex quantum theory with its unitary group
might expand into a real quantum theory with an orthogonal group, broken by an
approximate operator at lower energies. Implementing this possibility
requires a real quantum double-valued statistics. A Clifford statistics,
representing a swap (12) by a difference of Clifford units,
is uniquely appropriate. Unlike the Maxwell-Boltzmann, Fermi-Dirac,
Bose-Einstein, and para- statistics, which are tensorial and single-valued, and
unlike anyons, which are confined to two dimensions, Clifford statistics are
multivalued and work for any dimensionality. Nayak and Wilczek proposed a
Clifford statistics for the fractional quantum Hall effect. We apply them to
toy quanta here. A complex-Clifford example has the energy spectrum of a system
of spin-1/2 particles in an external magnetic field. This supports the proposal
that the double-valued rotations --- spin --- seen at current energies might
arise from double-valued permutations --- swap --- to be seen at higher
energies. Another toy with real Clifford statistics illustrates how an
effective imaginary unit can arise naturally within a real quantum theory.Comment: 15 pages, no figures; original title ("Clifford statistics") changed;
to appear in J. Math. Phys., 42, 2001. Key words: Clifford statistics,
cliffordons, double-valued representations of permutation groups, spin, swap,
imaginary unit , applications to quantum space-time and the Standard
Model. Some of these results were presented at the American Physical Society
Centennial Meeting, Atlanta, March 25, 199
Global geometry of two-dimensional charged black holes
The semiclassical geometry of charged black holes is studied in the context
of a two-dimensional dilaton gravity model where effects due to pair-creation
of charged particles can be included in a systematic way. The classical
mass-inflation instability of the Cauchy horizon is amplified and we find that
gravitational collapse of charged matter results in a spacelike singularity
that precludes any extension of the spacetime geometry. At the classical level,
a static solution describing an eternal black hole has timelike singularities
and multiple asymptotic regions. The corresponding semiclassical solution, on
the other hand, has a spacelike singularity and a Penrose diagram like that of
an electrically neutral black hole. Extremal black holes are destabilized by
pair-creation of charged particles. There is a maximally charged solution for a
given black hole mass but the corresponding geometry is not extremal. Our
numerical data exhibits critical behavior at the threshold for black hole
formation.Comment: REVTeX, 13 pages, 12 figures; Reference adde
Marked influence of the nature of chemical bond on CP-violating signature in molecular ions and
Heavy polar molecules offer a great sensitivity to the electron Electric
Dipole Moment(EDM). To guide emerging searches for EDMs with molecular ions, we
estimate the EDM-induced energy corrections for hydrogen halide ions
and in their respective ground states. We find that the energy corrections due to EDM for the two
ions differ by an unexpectedly large factor of fifteen. We demonstrate that a
major part of this enhancement is due to a dissimilarity in the nature of the
chemical bond for the two ions: the bond that is nearly of ionic character in
exhibits predominantly covalent nature in .
We conclude that because of this enhancement the HI ion may be a
potentially competitive candidate for the EDM search.Comment: This manuscript has been accepted for publication in Physical Review
Letters. The paper is now being prepared for publicatio
Semi-classical geometry of charged black holes
At the classical level, two-dimensional dilaton gravity coupled to an abelian
gauge field has charged black hole solutions, which have much in common with
four-dimensional Reissner-Nordstrom black holes, including multiple asymptotic
regions, timelike curvature singularities, and Cauchy horizons. The black hole
spacetime is, however, significantly modified by quantum effects, which can be
systematically studied in this two-dimensional context. In particular, the
back-reaction on the geometry due to pair-creation of charged fermions
destabilizes the inner horizon and replaces it with a spacelike curvature
singularity. The semi-classical geometry has the same global topology as an
electrically neutral black hole.Comment: REVTeX, 4 pages, 2 figures; references adde
Optical Pulse Dynamics in Active Metamaterials with Positive and Negative Refractive Index
We study numerically the propagation of two-color light pulses through a
metamaterial doped with active atoms such that the carrier frequencies of the
pulses are in resonance with two atomic transitions in the
configuration and that one color propagates in the regime of positive
refraction and the other in the regime of negative refraction. In such a
metamaterial, one resonant color of light propagates with positive and the
other with negative group velocity. We investigate nonlinear interaction of
these forward- and backward-propagating waves, and find self-trapped waves,
counter-propagating radiation waves, and hot spots of medium excitation.Comment: 9 pages, 6 figure
Preparation information and optimal decompositions for mixed quantum states
Consider a joint quantum state of a system and its environment. A measurement
on the environment induces a decomposition of the system state. Using
algorithmic information theory, we define the preparation information of a pure
or mixed state in a given decomposition. We then define an optimal
decomposition as a decomposition for which the average preparation information
is minimal. The average preparation information for an optimal decomposition
characterizes the system-environment correlations. We discuss properties and
applications of the concepts introduced above and give several examples.Comment: 13 pages, latex, 2 postscript figure
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