714 research outputs found
Variations of Infinite Derivative Modified Gravity
We consider nonlocal modified Einstein gravity without matter, where nonlocal
term has the form . For this model, in this paper we give
the derivation of the equations of motion in detail. This is not an easy task
and presented derivation should be useful to a researcher who wants to
investigate nonlocal gravity. Also, we present the second variation of the
related Einstein-Hilbert modified action and basics of gravity perturbations.Comment: 22 page
High-resolution FUSE and HST ultraviolet spectroscopy of the white dwarf central star of Sh 2-216
LS V +4621 is the DAO-type central star of the planetary nebula Sh 2-216. We
perform a comprehensive spectral analysis of high-resolution, high-S/N
ultraviolet observations obtained with FUSE and STIS aboard the HST as well as
the optical spectrum of LS V +4621 by means of state-of-the-art NLTE
model-atmosphere techniques in order to compare its photospheric properties to
theoretical predictions from stellar evolution theory as well as from diffusion
calculations.
From the N IV - NV, O IV - O VI, Si IV - Si V, and Fe V - Fe VII ionization
equilibria, we determined an effective temperature of 95 +/- 2 kK with high
precision. The surface gravity is log g = 6.9 +/- 0.2. An unexplained
discrepancy appears between the spectroscopic distance d = 224 +46/-58 pc and
the parallax distance d = 129 +6/-5 pc of LS V +4621. For the first time, we
have identified Mg IV and Ar VI absorption lines in the spectrum of a
hydrogen-rich central star and determined the Mg and Ar abundances as well as
the individual abundances of iron-group elements (Cr, Mn, Fe, Co, and Ni). With
the realistic treatment of metal opacities up to the iron group in the
model-atmosphere calculations, the so-called Balmer-line problem (found in
models that neglect metal-line blanketing) vanishes.
Spectral analysis by means of NLTE model atmospheres has presently arrived at
a high level of sophistication, which is now hampered largely by the lack of
reliable atomic data and accurate line-broadening tables. Strong efforts should
be made to improve upon this situation.Comment: 13 pages, 20 figure
On kappa-deformation and triangular quasibialgebra structure
We show that, up to terms of order 1/kappa^5, the kappa-deformed Poincare
algebra can be endowed with a triangular quasibialgebra structure. The
universal R matrix and coassociator are given explicitly to the first few
orders. In the context of kappa-deformed quantum field theory, we argue that
this structure, assuming it exists to all orders, ensures that states of any
number of identical particles, in any representation, can be defined in a
kappa-covariant fashion.Comment: 17 pages, Latex, typos corrected, references added, misleading
comments on twisting remove
New Evidences on Domestication of the Horse (Equus Ferus Caballus) and Origine of Domestic Mountain Pony
The results of draft genome research of permafrost horse bone dated approximately 560-780 (kyr BP) have been published recently. According to the data representing the oldest full genome sequence compared to the modern genomes of domesticated horse, Przewalskii and donkey it was suggested that the Equus lineage gave rise to contemporary horses, zebras and donkeys some 4.0 to 4.5 million years ago, twice increasing the assumed time to the common ancestor. Upon the phylogenetic and divergence analyses it was estimated that the Przewalskii and domestic horse populations diverged some 38-72 kyr BP and that there are no evidences that admixtures between Przewalskii and domestic horse populations occurred post-divergently thus Przewalskii’s involvement in the process of horse domestication has been excluded.
The new data on ancient equide genome question the conventional theory on the origin of Domestic mountain pony. Upon the protein variability of the Domestic mountain pony the influence of diluvial genome on the population was confirmed and this finding differed from the conventional theory stating E. f. Przewalskii and E. ferus caballus as ancestors of the autochthonous population. The role of different ancestral horses in evolution of our autochthonous population is therefore unclear.
The questions emerging from the most recent genetic and proteomic research in concern with the autochthonous populations are presented in the paper
Covariant particle statistics and intertwiners of the kappa-deformed Poincare algebra
To speak about identical particles - bosons or fermions - in quantum field
theories with kappa-deformed Poincare symmetry, one must have a kappa-covariant
notion of particle exchange. This means constructing intertwiners of the
relevant representations of kappa-Poincare. We show, in the simple case of
spinless particles, that intertwiners exist, and, supported by a perturbative
calculation to third order in 1/kappa, make a conjecture about the existence
and uniqueness of a certain preferred intertwiner defining particle exchange in
kappa-deformed theories.Comment: 16 pages, latex; v2, references adde
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
The Possibility of Organizing an Organic Sheep Breeding in the Municipality of Žagubica
Žagubica Municipality, in Eastern Serbia, is one of the most undeveloped municipalities in Serbia. It accounts for only 0.067% of the total GDP (Gross Domestic Product) of the Republic of Serbia. A large number of people migrated from this area to big cities or countries of the EU, mainly because of the economic underdevelopment and the lack of production and processing capacities. Nowadays agriculture has a major role in the economy of Žagubica, contributing to the total value created with 59.33%, which clearly speaks of its dominance, while far behind it is the manufacturing industry with 8.23% and commerce with 6.93%. Geographical position of the Žagubica Municipality, the Homolje territory, is an important natural resource of great potential, with specific characteristics of HNV (High Nature Value) region. Region of Homolje has a long tradition of sheep breeding and the quality of products has become well-known. However, depopulation of villages caused a decline in the production and closure of a number of processing facilities. The development of organic farming is one of the possible ways to revitalize the village and the development of this region rich in natural resources. This paper analyzes the strengths, weaknesses, opportunities, and threats (SWOT analysis) in the organization of organic sheep production in order to apply the necessary measures on the field for the organization of a new production system. The significant "advantages" of Žagubica Municipality are its herbal resources and the fact that the arable agricultural land makes 48.5% of the municipality area (42.9% of meadows and 26% of pastures) which is a good basis for the organization of the production. The issue of animal genetic resources is particularly analyzed and discussed. Under the "possibility" the attention is focused on various aspects of education in this field and its significance
Theoretical determination of lifetimes of metastable states in Sc III and Y III
Lifetimes of the first two metastable states in Sc^{2+} and Y^{2+} are
determined using the relativistic coupled-cluster theory. There is a
considerable interest in studying the electron correlation effects in these
ions as though their electronic configurations are similar to the neutral
alkali atoms, their structures are very different from the latter. We have made
a comparative study of the correlation trends between the above doubly ionized
systems with their corresponding neutral and singly ionized iso-electronic
systems. The lifetimes of the excited states of these ions are very important
in the field of astrophysics, especially for the study of post-main sequence
evolution of the cool giant stars.Comment: 13 pages, 1 figure and 5 table
Voros product and the Pauli principle at low energies
Using the Voros star product, we investigate the status of the two particle
correlation function to study the possible extent to which the previously
proposed violation of the Pauli principle may impact at low energies. The
results show interesting features which are not present in the computations
made using the Moyal star product.Comment: 5 pages LateX, minor correction
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