861 research outputs found
Non-Equilibrium Production of Photons via \pi^0\to 2\gamma in DCC's
We study production of photons via the non-equilibrium relaxation of a
Disoriented Chiral Condensate with the chiral order parameter having a large
initial amplitude along the \pi^0 direction. Assuming the validity of the low
energy coupling of the neutral pion to photons via the U_A(1) anomalous vertex,
we find that for large initial amplitudes along the \pi^0 direction, photon
production is enhanced by parametric amplification. These processes are
non-perturbative with a large contribution during the non-equilibrium stages of
the evolution and result in a distinct distribution of the produced photons and
a polarization asymmetry. For initial amplitudes of the \pi^0 component of the
order parameter between 200-400 MeV, corresponding to energy densities between
1-12 GeV/fm^3 we find a peak in the photon distribution at energies between
\approx 300 -600 MeV. We also find polarization asymmetries typically between
5-10%. We discuss the potential experimental impact of these results as well as
the problems associated with its detection.Comment: 36 pages, 14 figures, uses revte
Generation and manipulation of squeezed states of light in optical networks for quantum communication and computation
We analyze a fiber-optic component which could find multiple uses in novel
information-processing systems utilizing squeezed states of light. Our approach
is based on the phenomenon of photon-number squeezing of soliton noise after
the soliton has propagated through a nonlinear optical fiber. Applications of
this component in optical networks for quantum computation and quantum
cryptography are discussed.Comment: 12 pages, 2 figures; submitted to Journal of Optics
Constraints and Hamiltonian in Light-Front Quantized Field Theory
Self-consistent Hamiltonian formulation of scalar theory on the null plane is
constructed following Dirac method. The theory contains also {\it constraint
equations}. They would give, if solved, to a nonlinear and nonlocal
Hamiltonian. The constraints lead us in the continuum to a different
description of spontaneous symmetry breaking since, the symmetry generators now
annihilate the vacuum. In two examples where the procedure lacks
self-consistency, the corresponding theories are known ill-defined from
equal-time quantization. This lends support to the method adopted where both
the background field and the fluctuation above it are treated as dynamical
variables on the null plane. We let the self-consistency of the Dirac procedure
determine their properties in the quantized theory. The results following from
the continuum and the discretized formulations in the infinite volume limit do
agree.Comment: 11 pages, Padova University preprint DFPF/92/TH/52 (December '92
Smart Grid Communication Architecture Modeling for Heterogeneous Network Based Advanced Metering Infrastructure
A smart grid is an emerging technology in the power delivery system which provides an intelligent, self-recovery and homeostatic grid in delivering power to the users. Smart grid communication network provides transmission capacity for information transformation within the connected nodes in the network, in favor of functional and operational needs. In the electric grids communication network delay is based on choosing the appropriate technology and the types of devices enforced. In distinction, the combination of IEEE 802.16 based WiMAX and IEEE 802.11 based WiFi technologies provides improved coverage and gives low delay performances to meet the smart grid needs. By incorporating this method in Wide Area Monitoring System (WAMS) and Advanced Metering Infrastructure (AMI) the performance of the smart grid will be considerably improved. This work deals with the implementation of WiMAX-WLAN integrated network architecture for WAMS and AMI in the smart grid
Line tension and structure of smectic liquid crystal multilayers at the air-water interface
At the air/water interface, 4,-8-alkyl[1,1,-biphenyl]-4-carbonitrile (8CB)
domains with different thicknesses coexist in the same Langmuir film, as
multiple bilayers on a monolayer. The edge dislocation at the domain boundary
leads to line tension, which determines the domain shape and dynamics. By
observing the domain relaxation process starting from small distortions, we
find that the line tension is linearly dependent on the thickness difference
between the coexisting phases in the film. Comparisons with theoretical
treatments in the literature suggest that the edge dislocation at the boundary
locates near the center of the film, which means that the 8CB multilayers are
almost symmetric with respect to the air/water interface.Comment: 21 pages, 6 figure
Photoproduction Enhancement from Non Equilibrium Disoriented Chiral Condensates
We study photoproduction during the non-equilibrium stages of the formation
of chiral condensates within the ``quench'' scenario of the chiral phase
transition. The dynamics is modeled with a gauged linear sigma model. A novel
quantum kinetic approach to the description of photoproduction far off
equilibrium is developed. We find that non-equilibrium spinodal instabilities
of long wavelength pion fluctuations are responsible for an enhanced
photoproduction rate for energies MeV at order . These
non-equilibrium effects lead to a larger contribution than the typical
processes in the medium, including that of the anomalous neutral pion decay
(which is of order ). We follow the
evolution of the dynamics throughout the phase transition, which in this
scenario occurs on a time scale of about fm/c and integrate the photon
yield through its evolution. The spectrum of photons produced throughout the
phase transition is a non- equilibrium one. For thermal initial conditions at
the time of the quench it interpolates between a thermal distribution about 6%
above the initial temperature (at the time of the quench) for low energy MeV photons, and a high energy tail in thermal equilibrium at the initial
temperature, with a smooth crossover at 100 MeV. The rate displays a peak at
MeV which receives a larger enhancement the closer the initial
temperature at the time of the quench is to the critical temperature. It is
found that the enhancement of photoproduction at low energies is not an
artifact caused by the initial distribution of the photons, but is due to the
pionic instabilities. We suggest that these strong out of equilibrium effects
may provide experimental signatures for the formation and relaxation of DCC's
in heavy ion collisions.Comment: 33 pages, 11 figures, uses revtex and epsfi
Error Analysis in Spin Measurement using Synchro-ballistic Method and its Improvement
Error analysis of spin measurement using synchro-ballistic method is presented in this paper. Error in the spin measurement varies as the projections of marker move away from axis of symmetry, and the reason for variation of error is explained. An improvement to synchro-ballistic method is proposed for spin measurement, which reduces the error in measured spin, and an algorithm for implementation of same is provided. Results of improved synchro-ballistic method are compared with the theoretical estimation of spin from muzzle velocity
FDTD Simulation of Thermal Noise in Open Cavities
A numerical model based on the finite-difference time-domain (FDTD) method is
developed to simulate thermal noise in open cavities owing to output coupling.
The absorbing boundary of the FDTD grid is treated as a blackbody, whose
thermal radiation penetrates the cavity in the grid. The calculated amount of
thermal noise in a one-dimensional dielectric cavity recovers the standard
result of the quantum Langevin equation in the Markovian regime. Our FDTD
simulation also demonstrates that in the non-Markovian regime the buildup of
the intracavity noise field depends on the ratio of the cavity photon lifetime
to the coherence time of thermal radiation. The advantage of our numerical
method is that the thermal noise is introduced in the time domain without prior
knowledge of cavity modes.Comment: 8 pages, 7 figure
Quantum Noise Randomized Ciphers
We review the notion of a classical random cipher and its advantages. We
sharpen the usual description of random ciphers to a particular mathematical
characterization suggested by the salient feature responsible for their
increased security. We describe a concrete system known as AlphaEta and show
that it is equivalent to a random cipher in which the required randomization is
effected by coherent-state quantum noise. We describe the currently known
security features of AlphaEta and similar systems, including lower bounds on
the unicity distances against ciphertext-only and known-plaintext attacks. We
show how AlphaEta used in conjunction with any standard stream cipher such as
AES (Advanced Encryption Standard) provides an additional, qualitatively
different layer of security from physical encryption against known-plaintext
attacks on the key. We refute some claims in the literature that AlphaEta is
equivalent to a non-random stream cipher.Comment: Accepted for publication in Phys. Rev. A; Discussion augmented and
re-organized; Section 5 contains a detailed response to 'T. Nishioka, T.
Hasegawa, H. Ishizuka, K. Imafuku, H. Imai: Phys. Lett. A 327 (2004) 28-32
/quant-ph/0310168' & 'T. Nishioka, T. Hasegawa, H. Ishizuka, K. Imafuku, H.
Imai: Phys. Lett. A 346 (2005) 7
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