200,715 research outputs found
New Asymptotic Expanstion Method for the Wheeler-DeWitt Equation
A new asymptotic expansion method is developed to separate the Wheeler-DeWitt
equation into the time-dependent Schr\"{o}dinger equation for a matter field
and the Einstein-Hamilton-Jacobi equation for the gravitational field including
the quantum back-reaction of the matter field. In particular, the nonadiabatic
basis of the generalized invariant for the matter field Hamiltonian separates
the Wheeler-DeWitt equation completely in the asymptotic limit of
approaching infinity. The higher order quantum corrections of the gravity to
the matter field are found. The new asymptotic expansion method is valid
throughout all regions of superspace compared with other expansion methods with
a certain limited region of validity. We apply the new asymptotic expansion
method to the minimal FRW universe.Comment: 24 pages of Latex file, revte
Feynman's Decoherence
Gell-Mann's quarks are coherent particles confined within a hadron at rest,
but Feynman's partons are incoherent particles which constitute a hadron moving
with a velocity close to that of light. It is widely believed that the quark
model and the parton model are two different manifestations of the same
covariant entity. If this is the case, the question arises whether the Lorentz
boost destroys coherence. It is pointed out that this is not the case, and it
is possible to resolve this puzzle without inventing new physics. It is shown
that this decoherence is due to the measurement processes which are less than
complete.Comment: RevTex 15 pages including 6 figs, presented at the 9th Int'l
Conference on Quantum Optics (Raubichi, Belarus, May 2002), to be published
in the proceeding
Coupled oscillators and Feynman's three papers
According to Richard Feynman, the adventure of our science of physics is a
perpetual attempt to recognize that the different aspects of nature are really
different aspects of the same thing. It is therefore interesting to combine
some, if not all, of Feynman's papers into one. The first of his three papers
is on the ``rest of the universe'' contained in his 1972 book on statistical
mechanics. The second idea is Feynman's parton picture which he presented in
1969 at the Stony Brook conference on high-energy physics. The third idea is
contained in the 1971 paper he published with his students, where they show
that the hadronic spectra on Regge trajectories are manifestations of
harmonic-oscillator degeneracies. In this report, we formulate these three
ideas using the mathematics of two coupled oscillators. It is shown that the
idea of entanglement is contained in his rest of the universe, and can be
extended to a space-time entanglement. It is shown also that his parton model
and the static quark model can be combined into one Lorentz-covariant entity.
Furthermore, Einstein's special relativity, based on the Lorentz group, can
also be formulated within the mathematical framework of two coupled
oscillators.Comment: 31 pages, 6 figures, based on the concluding talk at the 3rd Feynman
Festival (Collage Park, Maryland, U.S.A., August 2006), minor correction
GaAs (AlGaAs)/CuInSe2 tandem solar cells. Technology status and future directions
Mechanically stacked, high efficiency, lightweight, and radiation resistant photovoltaic cells based on a GaAs thin film top and CuInSe2 thin film bottom cells were developed, and are considered one of the most promising devices for planar solar array applications. The highest efficiency demonstrated so far using the 4 sq cm design is 23.1 pct. AM0, one sun efficiency when measured in four-terminal configuration. The current status of the GaAs(AlGaAs)/CuInSe2 tandem cell program is presented and future directions that will lead to cell efficiencies higher than 26 pct. Air Mass Zero (AM0). A new 8 sq cm cell design developed for a two terminal and voltage matched configuration to minimize wiring complexity is discussed. Optimization of the GaAs structure for a higher end-of-life performance and further improvement of tandem cells by utilizing AlGaAs as an top absorber are described. Results of environmental tests conducted with these thin film GaAs/CuInSe2 tandem cells are also summarized
Validation of a model of regulation in the tryptophan operon against multiple experiment data using global optimisation
This paper is concerned with validating a mathematical model of regulation in the tryptophan operon using global optimization. Although a number of models for this biochemical network are proposed, in many cases only qualitative agreement between the model output and experimental data was demonstrated, since very little information is currently available to guide the selection of parameter values for the models. This paper presents a model validating method using both multiple experimental data and global optimization
Ideal Bose gas in fractal dimensions and superfluid He in porous media
Physical properties of ideal Bose gas with the fractal dimensionality between
D=2 and D=3 are theoretically investigated. Calculation shows that the
characteristic features of the specific heat and the superfluid density of
ideal Bose gas in fractal dimensions are strikingly similar to those of
superfluid Helium-4 in porous media. This result indicates that the geometrical
factor is dominant over mutual interactions in determining physical properties
of Helium-4 in porous media.Comment: 13 pages, 6 figure
Standing waves in the Lorentz-covariant world
When Einstein formulated his special relativity, he developed his dynamics
for point particles. Of course, many valiant efforts have been made to extend
his relativity to rigid bodies, but this subject is forgotten in history. This
is largely because of the emergence of quantum mechanics with wave-particle
duality. Instead of Lorentz-boosting rigid bodies, we now boost waves and have
to deal with Lorentz transformations of waves. We now have some understanding
of plane waves or running waves in the covariant picture, but we do not yet
have a clear picture of standing waves. In this report, we show that there is
one set of standing waves which can be Lorentz-transformed while being
consistent with all physical principle of quantum mechanics and relativity. It
is possible to construct a representation of the Poincar\'e group using
harmonic oscillator wave functions satisfying space-time boundary conditions.
This set of wave functions is capable of explaining the quantum bound state for
both slow and fast hadrons. In particular it can explain the quark model for
hadrons at rest, and Feynman's parton model hadrons moving with a speed close
to that of light.Comment: LaTex 20 pages, presented at the 2004 meeting of the International
Association of Relativistic Dynamincs, to be published in the proceeding
- …