15 research outputs found
Stochastic Self-Similar and Fractal Universe
The structures formation of the Universe appears as if it were a classically
self-similar random process at all astrophysical scales. An agreement is
demonstrated for the present hypotheses of segregation with a size of
astrophysical structures by using a comparison between quantum quantities and
astrophysical ones. We present the observed segregated Universe as the result
of a fundamental self-similar law, which generalizes the Compton wavelength
relation. It appears that the Universe has a memory of its quantum origin as
suggested by R.Penrose with respect to quasi-crystal. A more accurate analysis
shows that the present theory can be extended from the astrophysical to the
nuclear scale by using generalized (stochastically) self-similar random
process. This transition is connected to the relevant presence of the
electromagnetic and nuclear interactions inside the matter. In this sense, the
presented rule is correct from a subatomic scale to an astrophysical one. We
discuss the near full agreement at organic cell scale and human scale too.
Consequently the Universe, with its structures at all scales (atomic nucleus,
organic cell, human, planet, solar system, galaxy, clusters of galaxy, super
clusters of galaxy), could have a fundamental quantum reason. In conclusion, we
analyze the spatial dimensions of the objects in the Universe as well as
spacetime dimensions. The result is that it seems we live in an El Naschie's E
infinity Cantorian spacetime; so we must seriously start considering fractal
geometry as the geometry of nature, a type of arena where the laws of physics
appear at each scale in a self--similar way as advocated long ago by the
Swedish school of astrophysics.Comment: 17 pages, 3 figures, accepted by Chaos, Solitons & Fractla
Model- and calibration-independent test of cosmic acceleration
We present a calibration-independent test of the accelerated expansion of the
universe using supernova type Ia data. The test is also model-independent in
the sense that no assumptions about the content of the universe or about the
parameterization of the deceleration parameter are made and that it does not
assume any dynamical equations of motion. Yet, the test assumes the universe
and the distribution of supernovae to be statistically homogeneous and
isotropic. A significant reduction of systematic effects, as compared to our
previous, calibration-dependent test, is achieved. Accelerated expansion is
detected at significant level (4.3 sigma in the 2007 Gold sample, 7.2 sigma in
the 2008 Union sample) if the universe is spatially flat. This result depends,
however, crucially on supernovae with a redshift smaller than 0.1, for which
the assumption of statistical isotropy and homogeneity is less well
established.Comment: 13 pages, 2 figures, major change
Hubble flows and gravitational potentials in observable Universe
In this paper, we consider the Universe deep inside of the cell of
uniformity. At these scales, the Universe is filled with inhomogeneously
distributed discrete structures (galaxies, groups and clusters of galaxies),
which disturb the background Friedmann model. We propose mathematical models
with conformally flat, hyperbolic and spherical spaces. For these models, we
obtain the gravitational potential for an arbitrary number of randomly
distributed inhomogeneities. In the cases of flat and hyperbolic spaces, the
potential is finite at any point, including spatial infinity, and valid for an
arbitrary number of gravitating sources. For both of these models, we
investigate the motion of test masses (e.g., dwarf galaxies) in the vicinity of
one of the inhomogeneities. We show that there is a distance from the
inhomogeneity, at which the cosmological expansion prevails over the
gravitational attraction and where test masses form the Hubble flow. For our
group of galaxies, it happens at a few Mpc and the radius of the
zero-acceleration sphere is of the order of 1 Mpc, which is very close to
observations. Outside of this sphere, the dragging effect of the gravitational
attraction goes very fast to zero.Comment: 21 pages, 5 figure
Light propagation in statistically homogeneous and isotropic universes with general matter content
We derive the relationship of the redshift and the angular diameter distance
to the average expansion rate for universes which are statistically homogeneous
and isotropic and where the distribution evolves slowly, but which have
otherwise arbitrary geometry and matter content. The relevant average expansion
rate is selected by the observable redshift and the assumed symmetry properties
of the spacetime. We show why light deflection and shear remain small. We write
down the evolution equations for the average expansion rate and discuss the
validity of the dust approximation.Comment: 42 pages, no figures. v2: Corrected one detail about the angular
diameter distance and two typos. No change in result
MINDWALKER: Going one step further with assistive lower limbs exoskeleton for SCI condition subjects
This paper presents MINDWALKER, which is an ambitious EC funded research project coordinated by Space Applications Services aiming at the development of novel Brain Neural Computer Interfaces (BNCI) and robotics technologies, with the goal of obtaining a crutch-less assistive lower limbs exoskeleton, with non-invasive brain control approach as main strategy. Complementary BNCI control approaches such as arms electromyograms (EMG) are also researched. In the last phase of the project, the developed system should undergo a clinical evaluation with Spinal Cord Injured (SCI) subjects at the Fondazione Santa Lucia, Italy. © 2012 IEEE.SCOPUS: cp.pinfo:eu-repo/semantics/publishe