5,936 research outputs found
A new species of Aleurolobus Quaintance et Baker (Homoptera, Aleyrodidae) from Southern Europe.
Aleurolobus teucrii n. sp. is described from southern Italy and the Maltese Islands (Central Mediterranean). The species seems to be monophagous on Teucrium fruticans L. A key to the European species of this genus (A. niloticus Priesner et Hosny, A. olivinus (Silvestri), A. wunni (Ryberg) and A. teucrii n. sp.) is provided.peer-reviewe
A parallel compact-TVD method for compressible fluid dynamics employing shared and distributed-memory paradigms
A novel multi-block compact-TVD finite difference method for the simulation of compressible flows is presented. The method combines distributed and shared-memory paradigms to take advantage of the configuration of modern supercomputers that host many cores per shared-memory node. In our approach a domain decomposition technique is applied to a compact scheme using explicit flux formulas at block interfaces. This method offers great improvement in performance over earlier parallel compact methods that rely on the parallel solution of a linear system. A test case is presented to assess the accuracy and parallel performance of the new method
Conflicts, integration, hybridization of subcultures: An ecological approach to the case of queercore
This paper investigates the case study of queercore, providing a socio-historical analysis of its subcultural
production, in the terms of what Michel Foucault has called archaeology of knowledge (1969). In
particular, we will focus on: the self-definition of the movement; the conflicts between the two merged
worlds of punk and queer culture; the \u201cinternal-subcultural\u201d conflicts between both queercore and
punk, and between queercore and gay\lesbian music culture; the political aspects of differentiation.
In the conclusion, we will offer an innovative theoretical proposal about the interpretation of subcultures
in ecological and semiotic terms, combining the contribution of the American sociologist Andrew Abbot
and of the Russian semiologist Jurij Michajlovi\u10d Lotma
Polarization-based calculation of the dielectric tensor of polar crystals
We present a novel method for the calculation of the static and electronic
dielectric tensor of polar insulating crystals based on concepts from the
modern theory of dielectric polarization. As an application, we present the
first ab initio calculation of the dielectric constants in the wurtzite III-V
nitrides AlN, GaN, and InN.Comment: RevTeX 4 pages, no figures, numbering error correcte
Breaking the Vainshtein screening in clusters of galaxies
In this work we will test an alternative model of gravity belonging to the
large family of galileon models. It is characterized by an intrinsic breaking
of the Vainshtein mechanism inside large astrophysical objects, thus having
possibly detectable observational signatures. We will compare theoretical
predictions from this model with the observed total mass profile for a sample
of clusters of galaxies. The profiles are derived using two complementary
tools: X-ray hot intra-cluster gas dynamics, and strong and weak gravitational
lensing. We find that a dependence with the dynamical internal status of each
cluster is possible; for those clusters which are very close to be relaxed, and
thus less perturbed by possible astrophysical local processes, the galileon
model gives a quite good fit to both X-ray and lensing observations. Both
masses and concentrations for the dark matter halos are consistent with earlier
results found in numerical simulations and in the literature, and no compelling
statistical evidence for a deviation from general relativity is detectable from
the present observational state. Actually, the characteristic galileon
parameter is always consistent with zero, and only an upper limit
( at , at , and
at ) can be established. Some interesting distinctive deviations might
be operative, but the statistical validity of the results is far from strong,
and better data would be needed in order to either confirm or reject a
potential tension with general relativity.Comment: 26 pages, 3 tables, 4 figures. Accepted for publication on Phys. Rev.
Unifying static analysis of gravitational structures with a scale-dependent scalar field gravity as an alternative to dark matter
Aims. We investigated the gravitational effects of a scalar field within
scalar-tensor gravity as an alternative to dark matter. Motivated by chameleon,
symmetron and f(R)-gravity models, we studied a phenomenological scenario where
the scalar field has both a mass (i.e. interaction length) and a coupling
constant to the ordinary matter which scale with the local properties of the
considered astrophysical system. Methods. We analysed the feasibility of this
scenario using the modified gravitational potential obtained in its context and
applied it to the galactic and hot gas/stellar dynamics in galaxy clusters and
elliptical/spiral galaxies respectively. This is intended to be a first step in
assessing the viability of this new approach in the context of "alternative
gravity" models. Results. The main results are: 1. the velocity dispersion of
elliptical galaxies can be fitted remarkably well by the suggested scalar
field, with model significance similar to a classical Navarro-Frenk-White dark
halo profile; 2. the analysis of the stellar dynamics and the gas equilibrium
in elliptical galaxies has shown that the scalar field can couple with ordinary
matter with different strengths (different coupling constants) producing and/or
depending on the different clustering state of matter components; 3. elliptical
and spiral galaxies, combined with clusters of galaxies, show evident
correlations among theory parameters which suggest the general validity of our
results at all scales and a way toward a possible unification of the theory for
all types of gravitational systems we considered. All these results demonstrate
that the proposed scalar field scenario can work fairly well as an alternative
to dark matter.Comment: 23 pages, 15 figures, 5 tables, accepted for publication on Astronomy
& Astrophysic
Polynomial-exponential equations -- some new cases of solvability
Recently Brownawell and the second author proved a "non-degenerate" case of
the (unproved) "Zilber Nullstellensatz" in connexion with "Strong Exponential
Closure". Here we treat some significant new cases. In particular these settle
completely the problem of solving polynomial-exponential equations in two
complex variables. The methods of proof are also new, as is the consequence,
for example, that there are infinitely many complex with .Comment: 26 page
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