417 research outputs found
The Dirac Equation in Classical Statistical Mechanics
The Dirac equation, usually obtained by `quantizing' a classical stochastic
model is here obtained directly within classical statistical mechanics. The
special underlying space-time geometry of the random walk replaces the missing
analytic continuation, making the model `self-quantizing'. This provides a new
context for the Dirac equation, distinct from its usual context in relativistic
quantum mechanics.Comment: Condensed version of a talk given at the MRST conference, 05/02,
Waterloo, Ont. 7 page
Entwined Paths, Difference Equations and the Dirac Equation
Entwined space-time paths are bound pairs of trajectories which are traversed
in opposite directions with respect to macroscopic time. In this paper we show
that ensembles of entwined paths on a discrete space-time lattice are simply
described by coupled difference equations which are discrete versions of the
Dirac equation. There is no analytic continuation, explicit or forced, involved
in this description. The entwined paths are `self-quantizing'. We also show
that simple classical stochastic processes that generate the difference
equations as ensemble averages are stable numerically and converge at a rate
governed by the details of the stochastic process. This result establishes the
Dirac equation in one dimension as a phenomenological equation describing an
underlying classical stochastic process in the same sense that the Diffusion
and Telegraph equations are phenomenological descriptions of stochastic
processes.Comment: 15 pages, 5 figures Replacement 11/02 contains minor editorial
change
The Feynman chessboard model in 3 + 1 dimensions
The chessboard model was Feynman’s adaptation of his path integral method to a two-dimensional relativistic domain. It is shown that chessboard paths encode information about the contiguous pairs of paths in a spacetime plane, as required by discrete worldlines in Minkowski space. The application of coding by pairs in a four-dimensional spacetime is then restricted by the requirements of the Lorentz transformation, and the implementation of these restrictions provides an extension of the model to 4D, illuminating the relationship between relativity and quantum propagation
Scale relativity and fractal space-time: theory and applications
In the first part of this contribution, we review the development of the
theory of scale relativity and its geometric framework constructed in terms of
a fractal and nondifferentiable continuous space-time. This theory leads (i) to
a generalization of possible physically relevant fractal laws, written as
partial differential equation acting in the space of scales, and (ii) to a new
geometric foundation of quantum mechanics and gauge field theories and their
possible generalisations. In the second part, we discuss some examples of
application of the theory to various sciences, in particular in cases when the
theoretical predictions have been validated by new or updated observational and
experimental data. This includes predictions in physics and cosmology (value of
the QCD coupling and of the cosmological constant), to astrophysics and
gravitational structure formation (distances of extrasolar planets to their
stars, of Kuiper belt objects, value of solar and solar-like star cycles), to
sciences of life (log-periodic law for species punctuated evolution, human
development and society evolution), to Earth sciences (log-periodic
deceleration of the rate of California earthquakes and of Sichuan earthquake
replicas, critical law for the arctic sea ice extent) and tentative
applications to system biology.Comment: 63 pages, 14 figures. In : First International Conference on the
Evolution and Development of the Universe,8th - 9th October 2008, Paris,
Franc
Modelling annual and orbital variations in the scintillation of the relativistic binary PSR J11416545
We have observed the relativistic binary pulsar PSR J11416545 over a
period of 6 years using the Parkes 64 m radio telescope, with a focus on
modelling the diffractive intensity scintillations to improve the accuracy of
the astrometric timing model. The long-term scintillation, which shows orbital
and annual variations, allows us to measure parameters that are difficult to
measure with pulsar timing alone. These include: the orbital inclination ;
the longitude of the ascending node ; and the pulsar system transverse
velocity. We use the annual variations to resolve the previous ambiguity in the
sense of the inclination angle. Using the correct sense, and a prior
probability distribution given by a constraint from pulsar timing
(), we find and we estimate the
pulsar distance to be kpc. This then gives us an estimate of
this pulsar's proper motion of mas
yr in right ascension and mas yr in
declination. Finally, we obtain measurements of the spatial structure of the
interstellar electron density fluctuations, including: the spatial scale and
anisotropy of the diffraction pattern; the distribution of scattering material
along the line of sight; and spatial variation in the strength of turbulence
from epoch to epoch. We find that the scattering is dominated by a thin screen
at a distance of , with an anisotropy axial ratio .Comment: 17 pages, 8 figures, 2 tables. Accepted for publication in MNRA
- …