8,099 research outputs found
Quantum black holes in Type-IIA String Theory
We study black hole solutions of Type-IIA Calabi-Yau compactifications in the
presence of perturbative quantum corrections. We define a class of black holes
that only exist in the presence of quantum corrections and that, consequently,
can be considered as purely quantum black holes. The regularity conditions of
the solutions impose the topological constraint h^{1,1}>h^{2,1} on the
Calabi-Yau manifold, defining a class of admissible compactifications, which we
prove to be non-empty for h^{1,1}=3 by explicitly constructing the
corresponding Calabi-Yau manifolds, new in the literature.Comment: 17 pages. References added. Explanation of the truncation improve
Efficacy of insecticides on Tuta absoluta (Meyrick) and other pests in pole tomato.
Experimentos de campo em 2001 e 2005 foram conduzidos para determinar a eficácia de diversos inseticidas no controle da Tuta absoluta e o impacto desse controle na ocorrência das demais pragas do tomateiro. Os inseticidas testados assim como as respectivas doses por 100 litros de água foram: espinosade 4,8; 6,0; 7,2 g. i.a. com e sem Break Thru 0,03% v/v; clorfenapir 12,0 g. i.a.; emamectina 2,0 g i.a. com Joint Oil 0,25 % v/v e indoxacarbe 4,8 g i.a. com Joint Oil 0,25 % v/v. O delineamento experimental foi de blocos ao acaso com 4 repetições por tratamento sendo avaliado o complexo de pragas semanalmente. Todos os produtos testados, com exceção do espinosade sem Break Thru, foram eficientes no controle da T. absoluta. Considerando-se o complexo de pragas, espinosade + Break Thru mostrou-se ser o melhor tratamento no manejo da mosca-minadora Liriomyza spp. Field studies were conducted on 2001 and 2005 to determine the effectiveness of several insecticides in controlling Tuta absoluta and the impact of this control on the occurrence of other pests on tomato. The tested insecticides with their respective rates per 100 liters of water were: spinosad 4.8, 6.0, 7.2 g. a.i. with and without Break Thru 0.03% v/v; chlorfenapyr 12.0 g. a.i., emamectin 2.0 g. a.i. with Joint Oil 0.25 % v/v e indoxacarb 4.8 g. a.i. with Joint Oil 0.25 % v/v. The experiment was designed as randomized complete block with 4 replications per treatment. Trials were evaluated on a weekly basis. All tested treatments, except spinosad without Break Thru, were effective to control T. absoluta. Considering the pest complex, spinosad + Break Thru was the best treatment mainly because of the best overall performance on the serpentine leafminer Liriomyza spp
Topological Quintessence
A global monopole (or other topological defect) formed during a recent phase
transition with core size comparable to the present Hubble scale, could induce
the observed accelerating expansion of the universe. In such a model,
topological considerations trap the scalar field close to a local maximum of
its potential in a cosmologically large region of space. We perform detailed
numerical simulations of such an inhomogeneous dark energy system (topological
quintessence) minimally coupled to gravity, in a flat background of initially
homogeneous matter. We find that when the energy density of the field in the
monopole core starts dominating the background density, the spacetime in the
core starts to accelerate its expansion in accordance to a \Lambda CDM model
with an effective inhomogeneous spherical dark energy density parameter
\Omega_\Lambda(r). The matter density profile is found to respond to the global
monopole profile via an anti-correlation (matter underdensity in the monopole
core). Away from the monopole core, the spacetime is effectively
Einstein-deSitter (\Omega_\Lambda(r_{out}) -> 0) while at the center
\Omega_\Lambda(r ~ 0) is maximum. We fit the numerically obtained expansion
rate at the monopole core to the Union2 data and show that the quality of fit
is almost identical to that of \Lambda CDM. Finally, we discuss potential
observational signatures of this class of inhomogeneous dark energy models.Comment: Accepted in Phys. Rev. D (to appear). Added observational bounds on
parameters. 10 pages (two column revtex), 6 figures. The Mathematica files
used to produce the figures of this study may be downloaded from
http://leandros.physics.uoi.gr/topquin
Geometrical foundations of fractional supersymmetry
A deformed -calculus is developed on the basis of an algebraic structure
involving graded brackets. A number operator and left and right shift operators
are constructed for this algebra, and the whole structure is related to the
algebra of a -deformed boson. The limit of this algebra when is a -th
root of unity is also studied in detail. By means of a chain rule expansion,
the left and right derivatives are identified with the charge and covariant
derivative encountered in ordinary/fractional supersymmetry and this leads
to new results for these operators. A generalized Berezin integral and
fractional superspace measure arise as a natural part of our formalism. When
is a root of unity the algebra is found to have a non-trivial Hopf
structure, extending that associated with the anyonic line. One-dimensional
ordinary/fractional superspace is identified with the braided line when is
a root of unity, so that one-dimensional ordinary/fractional supersymmetry can
be viewed as invariance under translation along this line. In our construction
of fractional supersymmetry the -deformed bosons play a role exactly
analogous to that of the fermions in the familiar supersymmetric case.Comment: 42 pages, LaTeX. To appear in Int. J. Mod. Phys.
First test of a high voltage feedthrough for liquid Argon TPCs connected to a 300 kV power supply
Voltages above a hundred kilo-volt will be required to generate the drift
field of future very large liquid Argon Time Projection Chambers. The most
delicate component is the feedthrough whose role is to safely deliver the very
high voltage to the cathode through the thick insulating walls of the cryostat
without compromising the purity of the argon inside. This requires a
feedthrough that is typically meters long and carefully designed to be vacuum
tight and have small heat input. Furthermore, all materials should be carefully
chosen to allow operation in cryogenic conditions. In addition, electric fields
in liquid argon should be kept below a threshold to reduce risks of discharges.
The combination of all above requirements represents significant challenges
from the design and manufacturing perspective. In this paper, we report on the
successful operation of a feedthrough satisfying all the above requirements.
The details of the feedthrough design and its manufacturing steps are provided.
Very high voltages up to unprecedented voltages of -300 kV could be applied
during long periods repeatedly. A source of instability was observed, which was
specific to the setup configuration which was used for the test and not due to
the feedthrough itself.Comment: 13 pages, 9 figure
Non-extremal branes
We prove that for arbitrary black brane solutions of generic Supergravities
there is an adapted system of variables in which the equations of motion are
exactly invariant under electric-magnetic duality, i.e. the interchange of a
given extended object by its electromagnetic dual. We obtain thus a procedure
to automatically construct the electromagnetic dual of a given brane without
needing to solve any further equation. We apply this procedure to construct the
non-extremal (p, q)-string of Type-IIB String Theory (new in the literature),
explicitly showing how the dual (p, q)-five-brane automatically arises in this
construction. In addition, we prove that the system of variables used is
suitable for a generic characterization of every double-extremal Supergravity
brane solution, which we perform in full generality.Comment: 6 pages; v2 minor correction
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