48 research outputs found
Exotic Low Density Fermion States in the Two Measures Field Theory: Neutrino Dark Energy
We study a new field theory effect in the cosmological context in the Two
Measures Field Theory (TMT). TMT is an alternative gravity and matter field
theory where the gravitational interaction of fermionic matter is reduced to
that of General Relativity when the energy density of the fermion matter is
much larger than the dark energy density. In this case also the 5-th force
problem is solved automatically. In the opposite limit, where the magnitudes of
fermionic energy density and scalar field dark energy density become
comparable, nonrelativistic fermions can participate in the cosmological
expansion in a very unusual manner. Some of the features of such states in a
toy model of the late time universe filled with homogeneous scalar field and
uniformly distributed nonrelativistic neutrinos: neutrino mass increases as m ~
a^{3/2}; the neutrino gas equation-of-state approaches w=-1, i.e. neutrinos
behave as a sort of dark energy; the total (scalar field + neutrino)
equation-of-state also approaches w=-1; the total energy density of such
universe is less than it would be in the universe filled with the scalar field
alone. An analytic solution is presented. A domain structure of the dark energy
seems to be possible. We speculate that decays of the CLEP state neutrinos may
be both an origin of cosmic rays and responsible for a late super-acceleration
of the universe. In this sense the CLEP states exhibit simultaneously new
physics at very low densities and for very high particle masses.Comment: 47 pages, accepted for publication in Int.J.Mod.Phys.
Particle and Antiparticle sectors in DSR1 and kappa-Minkowski space-time
In this paper we explore the problem of antiparticles in DSR1 and
-Minkowski space-time following three different approaches inspired by
the Lorentz invariant case: a) the dispersion relation, b) the Dirac equation
in space-time and c) the Dirac equation in momentum space. We find that it is
possible to define a map which gives the antiparticle sector from the
negative frequency solutions of the wave equation. In -Poincar\'e, the
corresponding map is the antipodal mapping, which is different from
. The difference is related to the composition law, which is crucial
to define the multiparticle sector of the theory. This discussion permits to
show that the energy of the antiparticle in DSR is the positive root of the
dispersion relation, which is consistent with phenomenological approaches.Comment: 15 pages, no figures, some references added, typos correcte
Soft singularity and the fundamental length
It is shown that some regular solutions in 5D Kaluza-Klein gravity may have
interesting properties if one from the parameters is in the Planck region. In
this case the Kretschman metric invariant runs up to a maximal reachable value
in nature, i.e. practically the metric becomes singular. This observation
allows us to suppose that in this situation the problems with such soft
singularity will be much easier resolved in the future quantum gravity then by
the situation with the ordinary hard singularity (Reissner-Nordstr\"om
singularity, for example). It is supposed that the analogous consideration can
be applied for the avoiding the hard singularities connected with the gauge
charges.Comment: 5 page
Investigating pseudoscalar and scalar dark matter
In this paper another class of Dark Matter candidate particles: the
pseudoscalar and scalar light bosonic candidates, is discussed. Particular care
is devoted to the study of the processes for their detection (which only
involves electrons and photons/X-rays) in a suitable underground experimental
set-up. For this purpose the needed calculations are developed and various
related aspects and phenomenologies are discussed. In particular, it is shown
that - in addition to the WIMP cases already discussed elsewhere - there is
also possibility for a bosonic candidate to account for the 6.3 sigma C.L.
model independent evidence for the presence of a particle DM component in the
galactic halo observed by DAMA/NaI. Allowed regions in these scenarios are
presented also paying particular care on the cosmological interest of the
bosonic candidate.Comment: 23 pages, 6 figures, 1 table, Int. J. Mod. Phys. A (in press
Special relativity with two invariant scales: Motivation, Fermions, Bosons, Locality, and Critique
We present a Master equation for description of fermions and bosons for
special relativities with two invariant scales, SR2, (c and lambda_P). We
introduce canonically-conjugate variables (chi^0, chi) to (epsilon, pi) of
Judes-Visser. Together, they bring in a formal element of linearity and
locality in an otherwise non-linear and non-local theory. Special relativities
with two invariant scales provide all corrections, say, to the standard model
of the high energy physics, in terms of one fundamental constant, lambda_P. It
is emphasized that spacetime of special relativities with two invariant scales
carries an intrinsic quantum-gravitational character. In an addenda, we also
comment on the physical importance of a phase factor that the whole literature
on the subject has missed and present a brief critique of SR2. In addition, we
remark that the most natural and physically viable SR2 shall require
momentum-space and spacetime to be non-commutative with the non-commutativity
determined by the spin content and C, P, and T properties of the examined
representation space. Therefore, in a physically successful SR2, the notion of
spacetime is expected to be deeply intertwined with specific properties of the
test particle.Comment: Int. J. Mod. Phys. D (in press). Extended version of a set of two
informal lectures given in "La Sapienza" (Rome, May 2001
Spin half fermions with mass dimension one: theory, phenomenology, and dark matter
We provide the first details on the unexpected theoretical discovery of a
spin-one-half matter field with mass dimension one. It is based upon a complete
set of dual-helicity eigenspinors of the charge conjugation operator. Due to
its unusual properties with respect to charge conjugation and parity, it
belongs to a non-standard Wigner class. Consequently, the theory exhibits
non-locality with (CPT)^2 = - I. We briefly discuss its relevance to the
cosmological `horizon problem'. Because the introduced fermionic field is
endowed with mass dimension one, it can carry a quartic self-interaction. Its
dominant interaction with known forms of matter is via Higgs, and with gravity.
This aspect leads us to contemplate the new fermion as a prime dark matter
candidate. Taking this suggestion seriously we study a supernova-like explosion
of a galactic-mass dark matter cloud to set limits on the mass of the new
particle and present a calculation on relic abundance to constrain the relevant
cross-section. The analysis favours light mass (roughly 20 MeV) and relevant
cross-section of about 2 pb. Similarities and differences with the WIMP and
mirror matter proposals for dark matter are enumerated. In a critique of the
theory we bare a hint on non-commutative aspects of spacetime, and
energy-momentum space.Comment: 78 pages [Changes: referee-suggested improvements, additional
important references, and better readability
Surface topography of the InSb-MnSb thin films
In that report we observe a semiconductor eutectic composite InSb-MnSb thin films, prepared by the "flash evaporation" method. The atomic force microscopy and the scanning electron microscopy were employed for investigation microstructure and surface relief of the InSb-MnSb thin films. В этом отчете мы наблюдаем за тонкими пленками полупроводникового электического композита InSb-MnSb, полученными методом «мгновенного испарения». С помощью атомно-силовой микроскопии и сканирующей электронной микроскопии исследованы микроструктура и рельеф поверхности тонких пленок InSb-MnSb
Surface topography of the InSb-MnSb thin films
In that report we observe a semiconductor eutectic composite InSb-MnSb thin films, prepared by the "flash evaporation" method. The atomic force microscopy and the scanning electron microscopy were employed for investigation microstructure and surface relief of the InSb-MnSb thin films. В этом отчете мы наблюдаем за тонкими пленками полупроводникового электического композита InSb-MnSb, полученными методом «мгновенного испарения». С помощью атомно-силовой микроскопии и сканирующей электронной микроскопии исследованы микроструктура и рельеф поверхности тонких пленок InSb-MnSb
Doubly Special Relativity and de Sitter space
In this paper we recall the construction of Doubly Special Relativity (DSR)
as a theory with energy-momentum space being the four dimensional de Sitter
space. Then the bases of the DSR theory can be understood as different
coordinate systems on this space. We investigate the emerging geometrical
picture of Doubly Special Relativity by presenting the basis independent
features of DSR that include the non-commutative structure of space-time and
the phase space algebra. Next we investigate the relation between our geometric
formulation and the one based on quantum -deformations of the
Poincar\'e algebra. Finally we re-derive the five-dimensional differential
calculus using the geometric method, and use it to write down the deformed
Klein-Gordon equation and to analyze its plane wave solutions.Comment: 26 pages, one formula (67) corrected; some remarks adde
Contractions, deformations and curvature
The role of curvature in relation with Lie algebra contractions of the
pseudo-ortogonal algebras so(p,q) is fully described by considering some
associated symmetrical homogeneous spaces of constant curvature within a
Cayley-Klein framework. We show that a given Lie algebra contraction can be
interpreted geometrically as the zero-curvature limit of some underlying
homogeneous space with constant curvature. In particular, we study in detail
the contraction process for the three classical Riemannian spaces (spherical,
Euclidean, hyperbolic), three non-relativistic (Newtonian) spacetimes and three
relativistic ((anti-)de Sitter and Minkowskian) spacetimes. Next, from a
different perspective, we make use of quantum deformations of Lie algebras in
order to construct a family of spaces of non-constant curvature that can be
interpreted as deformations of the above nine spaces. In this framework, the
quantum deformation parameter is identified as the parameter that controls the
curvature of such "quantum" spaces.Comment: 17 pages. Based on the talk given in the Oberwolfach workshop:
Deformations and Contractions in Mathematics and Physics (Germany, january
2006) organized by M. de Montigny, A. Fialowski, S. Novikov and M.
Schlichenmaie