26 research outputs found
Dark energy, antimatter gravity and geometry of the Universe
This article is based on two hypotheses. The first one is the existence of
the gravitational repulsion between particles and antiparticles. Consequently,
virtual particle-antiparticle pairs in the quantum vacuum may be considered as
gravitational dipoles. The second hypothesis is that the Universe has geometry
of a four-dimensional hyper-spherical shell with thickness equal to the Compton
wavelength of a pion, which is a simple generalization of the usual geometry of
a 3-hypersphere. It is striking that these two hypotheses lead to a simple
relation for the gravitational mass density of the vacuum, which is in very
good agreement with the observed dark energy density
On the relation between mass of pion, fundamental physical constants and cosmological parameters
In this article we reconsider the old mysterious relation, advocated by Dirac
and Weinberg, between the mass of the pion, the fundamental physical constants,
and the Hubble parameter. By introducing the cosmological density parameters,
we show how the corresponding equation may be written in a form that is
invariant with respect to the expansion of the Universe and without invoking a
varying gravitational "constant", as was originaly proposed by Dirac. It is
suggest that, through this relation, Nature gives a hint that virtual pions
dominante the "content" of the quantum vacuum
On the vacuum fluctuations, Pioneer Anomaly and Modified Newtonian Dynamics
We argue that the so-called "Pioneer Anomaly" is related to the quantum
vacuum fluctuations. Our approach is based on the hypothesis of the
gravitational repulsion between matter and antimatter, what allows considering,
the virtual particle-antiparticle pairs in the physical vacuum, as
gravitational dipoles. Our simplified calculations indicate that the anomalous
deceleration of the Pioneer spacecrafts could be a consequence of the vacuum
polarization in the gravitational field of the Sun. At the large distances, the
vacuum polarization by baryonic matter could mimic dark matter what opens
possibility that dark matter do not exist, as advocated by the Modified
Newtonian Dynamics (MOND)
The time and frequency comparisons via Loran-C and National TV Network in Yugoslavia
Time comparisons were made between cesium clocks in Yugoslavia and other cesium clocks in the country by the Laboratory of Federal Bureau of Measures and Precious Metals. Regional standard frequency and time signals dissemination is over National TV network by so called active TV system. International comparisons are performed via Loran-C system and by clock transportation. The method of calculation and approximation of the time signal propagation delays is given. Settled comparison results of the cesium clocks via TV network, Loran-C, and by clock transportation are also discussed in this paper
"Dark energy" in the Local Void
The unexpected discovery of the accelerated cosmic expansion in 1998 has
filled the Universe with the embarrassing presence of an unidentified "dark
energy", or cosmological constant, devoid of any physical meaning. While this
standard cosmology seems to work well at the global level, improved knowledge
of the kinematics and other properties of our extragalactic neighborhood
indicates the need for a better theory. We investigate whether the recently
suggested repulsive-gravity scenario can account for some of the features that
are unexplained by the standard model. Through simple dynamical considerations,
we find that the Local Void could host an amount of antimatter
() roughly equivalent to the mass of a typical
supercluster, thus restoring the matter-antimatter symmetry. The antigravity
field produced by this "dark repulsor" can explain the anomalous motion of the
Local Sheet away from the Local Void, as well as several other properties of
nearby galaxies that seem to require void evacuation and structure formation
much faster than expected from the standard model. At the global cosmological
level, gravitational repulsion from antimatter hidden in voids can provide more
than enough potential energy to drive both the cosmic expansion and its
acceleration, with no need for an initial "explosion" and dark energy.
Moreover, the discrete distribution of these dark repulsors, in contrast to the
uniformly permeating dark energy, can also explain dark flows and other
recently observed excessive inhomogeneities and anisotropies of the Universe.Comment: 6 pages, accepted as a Letter to the Editor by Astrophysics and Space
Scienc
A few provoking relations between dark energy, dark matter and pions
I present three relations, striking in their simplicity and fundamental
appearance. The first one connects the Compton wavelength of a pion and the
dark energy density of the Universe; the second one connects Compton wavelength
of a pion and the mass distribution of non-baryonic dark matter in a Galaxy;
the third one relates mass of a pion to fundamental physical constants and
cosmological parameters. All these relations are in excellent numerical
agreement with observations
CPT symmetry and antimatter gravity in general relativity
The gravitational behavior of antimatter is still unknown. While we may be
confident that antimatter is self-attractive, the interaction between matter
and antimatter might be either attractive or repulsive. We investigate this
issue on theoretical grounds. Starting from the CPT invariance of physical
laws, we transform matter into antimatter in the equations of both
electrodynamics and gravitation. In the former case, the result is the
well-known change of sign of the electric charge. In the latter, we find that
the gravitational interaction between matter and antimatter is a mutual
repulsion, i.e. antigravity appears as a prediction of general relativity when
CPT is applied. This result supports cosmological models attempting to explain
the Universe accelerated expansion in terms of a matter-antimatter repulsive
interaction.Comment: 6 pages, to be published in EPL (http://epljournal.edpsciences.org/
The Pioneer anomaly and the holographic scenario
In this paper we discuss the recently obtained relation between the
Verlinde's holographic model and the first phenomenological Modified Newtonian
dynamics. This gives also a promising possible explanation to the Pioneer
anomaly.Comment: 5 pages, Accepted for publication in Astrophysics & Space Scienc
Towards a quantum universe
In this short review we study the state of the art of the great problems in
cosmology and their interrelationships. The reconciliation of these problems
passes undoubtedly through the idea of a quantum universe.Comment: 7 pages, Accepted for publication in Astrophysics & Space Scienc
Status Report and Beam Time Request for Experiment AD-4
Summary of current status and plans for October 200