792 research outputs found
Whitham Deformations of Seiberg-Witten Curves for Classical Gauge Groups
Gorsky et al. presented an explicit construction of Whitham deformations of
the Seiberg-Witten curve for the \calN = 2 SUSY Yang-Mills theory.
We extend their result to all classical gauge groups and some other cases such
as the spectral curve of the affine Toda Toda system. Our
construction, too, uses fractional powers of the superpotential that
characterizes the curve. We also consider the -plane integral of
topologically twisted theories on four-dimensional manifolds with
in the language of these explicitly constructed Whitham
deformations and an integrable hierarchy of the KdV type hidden behind.Comment: latex, 39pp, no figure; some more comments and references on
integrable systems are added, and many typos are correcte
High efficiency somatic embryogenesis and plant germination in grapevine cultivars Chardonnay and Brachetto a grappolo lungo
A highly efficient, reproducible method for somatic embryogenesis induction, plant recovery and embryogenic culture preservation has been developed for cvs Chardonnay and Brachetto a grappolo lungo (Vitis vinifera), starting from immature anthers and ovaries. Embryogenic induction efficiency was 2 % and 17 % in anthers for Chardonnay and Brachetto g.l., respectively, and 14 % in ovaries for both cultivars. Embryogenic cultures of both genotypes are still propagating 3.5 years after the initial induction and are still morphogenic. Embryo conversion into plantlets occurred at suitable efficiencies during a 100 d culture for both Chardonnay (37 % and 15 %) and Brachetto g.l. (30 % and 29 %), in the two media tested. Organogenesis was also obtained from cotyledonary leaves of Chardonnay.
Ionisation-induced star formation III: Effects of external triggering on the IMF in clusters
We report on Smoothed Particle Hydrodynamics (SPH) simulations of the impact
on a turbulent M star--forming molecular cloud of
irradiation by an external source of ionizing photons. We find that the
ionizing radiation has a significant effect on the gas morphology, but a less
important role in triggering stars. The rate and morphology of star formation
are largely governed by the structure in the gas generated by the turbulent
velocity field, and feedback has no discernible effect on the stellar initial
mass function. Although many young stars are to be found in dense gas located
near an ionization front, most of these objects also form when feedback is
absent. Ionization has a stronger effect in diffuse regions of the cloud by
sweeping up low--density gas that would not otherwise form stars into
gravitationally--unstable clumps. However, even in these regions, dynamical
interactions between the stars rapidly erase the correlations between their
positions and velocities and that of the ionization front.Comment: 12 pages, 16 figures (some downgraded to fit on astro-ph), accepted
for publication in MNRA
Phase transition and hyperscaling violation for scalar Black Branes
We investigate the thermodynamical behavior and the scaling symmetries of the
scalar dressed black brane (BB) solutions of a recently proposed, exactly
integrable Einstein-scalar gravity model [1], which also arises as
compactification of (p-1)-branes with a smeared charge. The extremal, zero
temperature, solution is a scalar soliton interpolating between a conformal
invariant AdS vacuum in the near-horizon region and a scale covariant metric
(generating hyperscaling violation on the boundary field theory)
asymptotically. We show explicitly that for the boundary field theory this
implies the emergence of an UV length scale (related to the size of the brane),
which decouples in the IR, where conformal invariance is restored. We also show
that at high temperatures the system undergoes a phase transition. Whereas at
small temperature the Schwarzschild-AdS BB is stable, above a critical
temperature the scale covariant, scalar-dressed BB solution, becomes
energetically preferred. We calculate the critical exponent z and the
hyperscaling violation parameter of the scalar-dressed phase. In particular we
show that the hyperscaling violation parameter is always negative. We also show
that the above features are not a peculiarity of the exact integrable model of
Ref.[1], but are a quite generic feature of Einstein-scalar and
Einstein-Maxwell-scalar gravity models for which the squared-mass of the scalar
field is positive and the potential vanishes exponentially as the scalar field
goes to minus infinity.Comment: 20 pages, 4 figures. In the revised version it has been pointed out
that the Einstein-scalar gravity model considered in the paper also arises as
compactification of black p-branes with smeared charge
Matter-wave laser Interferometric Gravitation Antenna (MIGA): New perspectives for fundamental physics and geosciences
The MIGA project aims at demonstrating precision measurements of gravity with
cold atom sensors in a large scale instrument and at studying the associated
applications in geosciences and fundamental physics. The first stage of the
project (2013-2018) will consist in building a 300-meter long optical cavity to
interrogate atom interferometers and will be based at the low noise underground
laboratory LSBB in Rustrel, France. The second stage of the project (2018-2023)
will be dedicated to science runs and data analyses in order to probe the
spatio-temporal structure of the local gravity field of the LSBB region, a site
of high hydrological interest. MIGA will also assess future potential
applications of atom interferometry to gravitational wave detection in the
frequency band Hz hardly covered by future long baseline optical
interferometers. This paper presents the main objectives of the project, the
status of the construction of the instrument and the motivation for the
applications of MIGA in geosciences. Important results on new atom
interferometry techniques developed at SYRTE in the context of MIGA and paving
the way to precision gravity measurements are also reported.Comment: Proceedings of the 50th Rencontres de Moriond "100 years after GR",
La Thuile (Italy), 21-28 March 2015 - 10 pages, 5 figures, 23 references
version2: added references, corrected typo
The faint counterparts of MAMBO mm sources near the NTT Deep Field
We discuss identifications for 18 sources from our MAMBO 1.2mm survey of the
region surrounding the NTT Deep Field. We have obtained accurate positions from
Very Large Array 1.4GHz interferometry and in a few cases IRAM mm
interferometry, and have also made deep BVRIzJK imaging at ESO. We find
thirteen 1.2mm sources associated with optical/near-infrared objects in the
magnitude range K=19.0 to 22.5, while five are blank fields at K>22. The median
redshift of the radio-identified mm sources is ~2.6 from the radio/mm
estimator, and the median optical/near-infrared photometric redshifts for the
objects with counterparts ~2.1. This suggests that those radio-identified mm
sources without optical/near-infrared counterparts tend to lie at higher
redshifts than those with optical/near-infrared counterparts. Compared to
published identifications of objects from 850micron surveys of similar depth,
the median K and I magnitudes of our counterparts are roughly two magnitudes
fainter and the dispersion of I-K colors is less. Real differences in the
median redshifts, residual mis-identifications with bright objects, cosmic
variance, and small number statistics are likely to contribute to this
significant difference, which also affects redshift measurement strategies. We
discuss basic properties of the near-infrared/(sub)mm/radio spectral energy
distributions of our galaxies and of interferometrically identified submm
sources from the literature. From a comparison with submm objects with
CO-confirmed spectroscopic redshifts we argue that roughly two thirds of the
(sub)mm galaxies are at z>~2.5. This fraction is probably larger when including
sources without radio counterparts. (abridged)Comment: 45 pages, 9 figures. Accepted by ApJ. The resolution of figures 2 and
3 has been degraded. A higher quality pdf version of this paper is available
at http://www.mpe.mpg.de/~dannerb
Generalized Holographic Quantum Criticality at Finite Density
We show that the near-extremal solutions of Einstein-Maxwell-Dilaton
theories, studied in ArXiv:1005.4690, provide IR quantum critical geometries,
by embedding classes of them in higher-dimensional AdS and Lifshitz solutions.
This explains the scaling of their thermodynamic functions and their IR
transport coefficients, the nature of their spectra, the Gubser bound, and
regulates their singularities. We propose that these are the most general
quantum critical IR asymptotics at finite density of EMD theories.Comment: v4: Corrected the scaling equation for the conductivity in section
9.
Peroxisomal PEX7 Receptor Affects Cadmium-Induced ROS and Auxin Homeostasis in Arabidopsis Root System
Peroxisomes are important in plant physiological functions and stress responses. Through the production of reactive oxygen and nitrogen species (ROS and RNS), and antioxidant defense enzymes, peroxisomes control cellular redox homeostasis. Peroxin (PEX) proteins, such as PEX7 and PEX5, recognize peroxisome targeting signals (PTS1/PTS2) important for transporting proteins from cytosol to peroxisomal matrix. pex7-1 mutant displays reduced PTS2 protein import and altered peroxisomal metabolism. In this research we analyzed the role of PEX7 in the Arabidopsis thaliana root system exposed to 30 or 60 ÎŒM CdSO4. Cd uptake and translocation, indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) levels, and reactive oxygen species (ROS) and reactive nitrogen species (RNS) levels and catalase activity were analyzed in pex7-1 mutant primary and lateral roots in comparison with the wild type (wt). The peroxisomal defect due to PEX7 mutation did not reduce Cd-uptake but reduced its translocation to the shoot and the root cell peroxisomal signal detected by 8-(4-Nitrophenyl) Bodipy (N-BODIPY) probe. The trend of nitric oxide (NO) and peroxynitrite in pex7-1 roots, exposed/not exposed to Cd, was as in wt, with the higher Cd-concentration inducing higher levels of these RNS. By contrast, PEX7 mutation caused changes in Cd-induced hydrogen peroxide (H2O2) and superoxide anion (O2ââ) levels in the roots, delaying ROS-scavenging. Results show that PEX7 is involved in counteracting Cd toxicity in Arabidopsis root system by controlling ROS metabolism and affecting auxin levels. These results add further information to the important role of peroxisomes in plant responses to Cd
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