1,420 research outputs found
Scale Invariant Cosmology
An attempt is made here to extend to the microscopic domain the scale
invariant character of gravitation - which amounts to consider expansion as
applying to any physical scale. Surprisingly, this hypothesis does not prevent
the redshift from being obtained. It leads to strong restrictions concerning
the choice between the presently available cosmological models and to new
considerations about the notion of time. Moreover, there is no horizon problem
and resorting to inflation is not necessary.Comment: TeX, 20 page
I - Matter, antimatter and geometry II - The twin universe model : a solution to the problem of negative energy particles III - The twin universe model plus electric charges and matter-antimatter symmetry
We introduce a new dynamical group whose coadjoint action on its momentum
space takes account of matter-antimatter symmetry on pure geometrical grounds.
According to this description the energy and the spin are unchanged under
matter-antimatter symmetry. We recall that the antichron components of the
Poincar\'{e} group, ruling relativistic motions of a mass-point particle,
generate negative energy particles. The model with two twin universes, inspired
by Sakharov's one, solves the stability issue. Positive and negative energy
particles motions hold in two distinct folds. The model is extended to charged
particles. As a result, the matter-antimatter duality holds in both universes.Comment: 19 Fevrier 200
On the quaternion -isogeny path problem
Let \cO be a maximal order in a definite quaternion algebra over
of prime discriminant , and a small prime. We describe a
probabilistic algorithm, which for a given left -ideal, computes a
representative in its left ideal class of -power norm. In practice the
algorithm is efficient, and subject to heuristics on expected distributions of
primes, runs in expected polynomial time. This breaks the underlying problem
for a quaternion analog of the Charles-Goren-Lauter hash function, and has
security implications for the original CGL construction in terms of
supersingular elliptic curves.Comment: To appear in the LMS Journal of Computation and Mathematics, as a
special issue for ANTS (Algorithmic Number Theory Symposium) conferenc
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Development of a simulation model for the expansion of perlite
New applications of expanded perlite in the building industry lead to a growing demand for process optimization for the expansion of periite. Periite expanders aim to adapt their furnaces and/or furnace operation conditions in order to attain more flexibility to produce different expanded periite qualities. Α way to examine the possibilities of an existing installation is the numerical simulation of the periite expansion process in that installation. The two-phase flow field and combustion in the furnace can be modelled by using currently available Computational Fluid Dynamics (CFD) codes. The only problem is the modelling of the expansion process, which changes the particle size and thus influences the two-phase flow calculations.
In this paper the authors propose a physical model for the simulation of the expansion of periite. This model is based on the results of fundamental studies concerning the expansion phenomenon. It relies on the calculation of particle temperature and viscosity and thus takes into account the most influential parameters for perlite expansion. It allows the calculation of the perlite particle size as a funedon of time or of the particle's trajectory inside a furnace. Particle size statistics of the expanded product can be determined in that way. The model has been validated by comparison with experimental results from laboratory and industrial measurements
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