6,714 research outputs found
A parasitic copepod, Perulernaea gamitanae gen. et sp. nov. (Cyclopoida: Lernaeidae), from the nasal fossae of a Peruvian Amazon food fish
The female of Perulernaea gamitanae gen. et sp. nov. (Copepoda: Cyclopoida: Lernaeidae) is described from the nasal fossae of an important food fish, Colossoma macropomum (CUVIER), collected in the Peruvian Amazon near lquitos. The new genus differs from others in the family by having blunt head anchors, a well defined slender "neck", a fusiform hindbody, uropods, four pairs of well separated legs, genital pores which are post-equatorial in the hindbody and multiseriate egg sacs. The host is one of the largest freshwater fish of the Amazon region and is of considerable economic importance
Flavoring the gravity dual of N=1 Yang-Mills with probes
We study two related problems in the context of a supergravity dual to N=1
SYM. One of the problems is finding kappa symmetric D5-brane probes in this
particular background. The other is the use of these probes to add flavors to
the gauge theory. We find a rich and mathematically appealing structure of the
supersymmetric embeddings of a D5-brane probe in this background. Besides, we
compute the mass spectrum of the low energy excitations of N=1 SQCD (mesons)
and match our results with some field theory aspects known from the study of
supersymmetric gauge theories with a small number of flavors.Comment: 55 pages, 7 figures, LaTeX; v2: typos corrected, references added;
v3: typos correcte
Is it possible to accommodate massive photons in the framework of a gauge-invariant electrodynamics?
The construction of an alternative electromagnetic theory that preserves
Lorentz and gauge symmetries, is considered. We start off by building up
Maxwell electrodynamics in (3+1)D from the assumption that the associated
Lagrangian is a gauge-invariant functional that depends on the electron and
photon fields and their first derivatives only. In this scenario, as
well-known, it is not possible to set up a Lorentz invariant gauge theory
containing a massive photon. We show nevertheless that there exist two
radically different electrodynamics, namely, the Chern-Simons and the Podolsky
formulations, in which this problem can be overcome. The former is only valid
in odd space-time dimensions, while the latter requires the presence of
higher-order derivatives of the gauge field in the Lagrangian. This theory,
usually known as Podolsky electrodynamics, is simultaneously gauge and Lorentz
invariant; in addition, it contains a massive photon. Therefore, a massive
photon, unlike the popular belief, can be adequately accommodated within the
context of a gauge-invariant electrodynamics.Comment: 10 page
Electromagnetic radiation initiated by hadronic jets from microquasars in the ISM
Microquasars are potential candidates to produce a non-negligible fraction of
the observed galactic cosmic rays. The protons accelerated at the jet
termination shock interact with the interstellar medium and may produce
detectable fluxes of extended emission at different energy bands: high-energy
and very high-energy gamma-rays produced by neutral pion-decay, synchrotron and
bremsstrahlung emission in a wide energy range generated by the secondary
electrons produced by charged pion-decay. We discuss the association between
this scenario and some of the unidentified EGRET sources in the galactic plane.Comment: (1)Universitat de Barcelona (2)Max Planck institute fur kernphysik,
11 pages, 14 figures, accepted for publication in Astronomy & Astrophysic
Leptonic emission from microquasar jets: from radio to very high-energy gamma-rays
Microquasars are sources of very high-energy gamma-rays and, very probably,
high-energy gamma-ray emitters. We propose a model for a jet that can allow to
give accurate observational predictions for jet emission at different energies
and provide with physical information of the object using multiwavelength data.Comment: 2 pages, 1 figure. Proceedings of the conference: "International
Astronomical Union Symposium No. 230: Populations of High Energy Sources in
Galaxies". Edited by Evert J.A. Meurs & Giuseppina Fabbian
Broad-band electromagnetic radiation from microquasars interacting with ISM
Microquasars (MQs) are galactic objects with relativistic jets that
constitute a source population which can be responsible for production of a
non-negligible fraction of the observed galactic cosmic rays. These
relativistic protons, associated with the termination of the jet, interact with
the interstellar medium and, at certain surrounding conditions, may lead to
production of detectable fluxes of high-energy and very high-energy gamma-rays.
This radiation is accompanied by the broad-band emission of secondary electrons
from decays of -mesons produced through synchrotron, bremstrahlung and
inverse Compton process. The features of broad-band emission initiated by
proton-proton (pp) interactions in such a scenario is discussed in the context
of the strategy of search for counterparts of high-energy and very high-energy
gamma-ray sources in the galactic plane.Comment: High Energy Gamma-Ray Astronomy: 2nd International Symposium,
Proceedings of the conference held 26-30 July 2004 in Heidelberg (Germany).
Edited by Felix A. Aharonian, Heinz J. Volk, and Dieter Horns. AIP Conference
Proceedings, Volume 745. New York: American Institute of Physics, 2005.,
p.317-32
Three-dimensional Ising model confined in low-porosity aerogels: a Monte Carlo study
The influence of correlated impurities on the critical behaviour of the 3D
Ising model is studied using Monte Carlo simulations. Spins are confined into
the pores of simulated aerogels (diffusion limited cluster-cluster aggregation)
in order to study the effect of quenched disorder on the critical behaviour of
this magnetic system. Finite size scaling is used to estimate critical
couplings and exponents. Long-range correlated disorder does not affect
critical behavior. Asymptotic exponents differ from those of the pure 3D Ising
model (3DIS), but it is impossible, with our precision, to distinguish them
from the randomly diluted Ising model (RDIS).Comment: 10 pages, 10 figures. Submitted to Physical Review
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