343 research outputs found
The analytic two-loop soft function for leading-jet pT
We present the calculation of the two-loop soft function for the transverse
momentum distribution of the leading jet produced in association with any
colour-singlet system (e.g.~a Higgs or a boson). This constitutes a central
ingredient for the resummation of the above distribution as well as the
jet-vetoed cross section at the next-to-next-to-next-to-leading logarithmic
order, both of which play an important role in the precision physics programme
at the Large Hadron Collider. The calculation is performed in soft-collinear
effective theory with an appropriate regularisation of the rapidity divergences
that occur in the phase-space integrals. We obtain analytic results by
employing an exponential regulator and by taking a Laurent expansion in the jet
radius . All expressions are presented as ancillary files with this article.Comment: 17 pages, 4 figures, and ancillary files with result
Tracing groundwater salinization processes in coastal aquifers: a hydrogeochemical and isotopic approach in Na-Cl brackish waters of north-western Sardinia, Italy
Abstract. Throughout the Mediterranean, salinization threatens water quality, especially in coastal areas. This salinization is the result of concomitant processes related to both seawater intrusion and waterârock interaction, which in some cases are virtually indistinguishable. In the Nurra region of northwestern Sardinia, recent salinization related to marine water intrusion has been caused by aquifer exploitation. However, the geology of this region records a long history from the Palaeozoic to the Quaternary, and is structurally complex and comprises a wide variety of lithologies, including Triassic evaporites. Determining the origin of the saline component of the Jurassic and Triassic aquifers in the Nurra region may provide a useful and more general model for salinization processes in the Mediterranean area, where the occurrence of evaporitic rocks in coastal aquifers is a common feature. In addition, due to intensive human activity and recent climatic change, the Nurra has become vulnerable to desertification and, in common with other Mediterranean islands, surface water resources periodically suffer from severe shortages. With this in mind, we report new data regarding brackish and surface waters (outcrop and lake samples) of the Na-Cl type from the Nurra region, including major ions and selected trace elements (B, Br, I, and Sr), in addition to isotopic data including ÎŽ18O, ÎŽD in water, and ÎŽ34S and ÎŽ18O in dissolved SO4. To identify the origin of the salinity more precisely, we also analysed the mineralogical and isotopic composition of Triassic evaporites. The brackish waters have Cl contents of up to 2025 mg Lâ1 , and the ratios between dissolved ions and Cl, with the exception of the Br / Cl ratio, are not those expected on the basis of simple mixing between rainwater and seawater. The ÎŽ18O and ÎŽD data indicate that most of the waters fall between the regional meteoric water line and the global meteoric water line, supporting the conclusion that they are meteoric in origin. A significant consequence of the meteoric origin of the Na-Cl-type water studied here is that the Br / Cl ratio, extensively used to assess the origin of salinity in fresh water, should be used with care in carbonate aquifers that are near the coast. Overall, ÎŽ34S and ÎŽ18O levels in dissolved SO4 suggest that waterârock interaction is responsible for the Na-Cl brackish composition of the water hosted by the Jurassic and Triassic aquifers of the Nurra, and this is consistent with the geology and lithological features of the study area. Evaporite dissolution may also explain the high Cl content, as halite was detected within the gypsum deposits. Finally, these Na-Cl brackish waters are undersaturated with respect to the more soluble salts, implying that in a climate evolving toward semi-arid conditions, the salinization process could intensify dramatically in the near future
Clean and Dirty Superconductivity in Pure, Al doped, and Neutron Irradiated MgB2: a Far-Infrared Study
The effects of Al substitution and neutron irradiation on the conduction
regime (clean or dirty) of the - and -band of MgB have been
investigated by means of far-infrared spectroscopy. The intensity reflected by
well characterized polycrystalline samples was measured up to 100 cm in
both normal and superconducting state. The analysis of the superconducting to
normal reflectivity ratios shows that only the effect of the opening of the
small gap in the dirty -band can be clearly observed in pure MgB,
consistently with previous results. In Al-doped samples the dirty character of
the -band is increased, while no definitive conclusion on the conduction
regime of the -band can be drawn. On the contrary, results obtained
for the irradiated sample show that the irradiation-induced disorder drives the
-band in the dirty regime, making the large gap in -band
observable for the first time in far-infrared measurements.Comment: 11 pages, 1 figur
Quark and gluon two-loop beam functions for leading-jet and slicing at NNLO
We compute the complete set of two-loop beam functions for the transverse
momentum distribution of the leading jet produced in association with an
arbitrary colour-singlet system. Our results constitute the last missing
ingredient for the calculation of the jet-vetoed cross section at small veto
scales at the next-to-next-to-leading order, as well as an important ingredient
for its resummation to next-to-next-to-next-to-leading logarithmic order. Our
calculation is performed in the soft-collinear effective theory framework with
a suitable regularisation of the rapidity divergences occurring in the
phase-space integrals. We discuss the occurrence of soft-collinear mixing terms
that might violate the factorisation theorem, and demonstrate that they vanish
at two loops in the exponential rapidity regularisation scheme when performing
a multipole expansion of the measurement function. As in our recent computation
of the two-loop soft function, we present the results as a Laurent expansion in
the jet radius . We provide analytic expressions for all flavour channels in
space with the exception of a set of -independent non-logarithmic terms
that are given as numerical grids. We also perform a fully numerical
calculation with exact dependence, and find that it agrees with our
analytic expansion at the permyriad level or better. Our calculation allows us
to define a next-to-next-to-leading order slicing method using the leading-jet
as a slicing variable. As a check of our results, we carry out a
calculation of the Higgs and boson total production cross sections at the
next-to-next-to-leading order in QCD.Comment: 26 pages, 3 figures and a set of ancillary file
Piecewise planar underwater mosaicing
A commonly ignored problem in planar mosaics, yet often present in practice, is the selection of a reference homography reprojection frame where to attach the successive image frames of the mosaic. A bad choice for the reference frame can lead to severe distortions in the mosaic and can degenerate in incorrect configurations after some sequential frame concatenations. This problem is accentuated in uncontrolled underwater acquisition setups as those provided by AUVs or ROVs due to both the noisy trajectory of the acquisition vehicle - with roll and pitch shakes - and to the non-flat nature of the seabed which tends to break the planarity assumption implicit in the mosaic construction. These scenarios can also introduce other undesired effects, such as light variations between successive frames, scattering and attenuation, vignetting, flickering and noise. This paper proposes a novel mosaicing pipeline, also including a strategy to select the best reference homography in planar mosaics from video sequences which minimizes the distortions induced on each image by the mosaic homography itself. Moreover, a new non-linear color correction scheme is incorporated to handle strong color and luminosity variations among the mosaic frames. Experimental evaluation of the proposed method on real, challenging underwater video sequences shows the validity of the approach, providing clear and visually appealing mosaic
Exactly solvable models in 2D semiclassical dilaton gravity and extremal black holes
Previously known exactly solvable models of 2D semiclassical dilaton gravity
admit, in the general case, only non-extreme black holes. It is shown that
there exist exceptional degenerate cases, that can be obtained by some limiting
transitions from the general exact solution, which include, in particular,
extremal and ultraextremal black holes. We also analyze properties of extreme
black holes without demanding exact solvability and show that for such
solutions quantum backreaction forbids the existence of ultraextreme black
holes. The conditions,under which divergencies of quantum stresses in a free
falling frame can disappear, are found. We derive the closed equation with
respect to the metric as a function of the dilaton field that enables one,
choosing the form of the metric, to restore corresponding Lagrangian. It is
demonstrated that exactly solvable models, found earlier, can be extended to
include an electric charge only in two cases: either the dilaton-gravitation
coupling is proportional to the potential term, or the latter vanishes. The
second case leads to the effective potential with a negative amplitude and we
analyze, how this fact affects the structure of spacetime. We also discuss the
role of quantum backreaction in the relationship between extremal horizons and
the branch of solutions with a constant dilaton.Comment: 31 pages. In v.2 typo in Ref. [2] corrected, 4 references added.
Accepted in Class. Quant. Gra
TEMATIZANDO O ENSINO RELIGIOSO â IDENTIDADE E DES-IDENTIFICAĂĂES
In this study, the authors have investigated the determination of the most suitable legal form for the development of the cluster management activities. In each particular case the developers of the cluster have to assess the objectives of the cluster, the principal aspects of the mutual partnership, the risks that could be provoked, and in accordance with the derived decisions. The choice of the cluster legal activity form depends on the objectives and on the branch in which the cluster is operating, on the number of the cluster participants, on the type of the activities of the cluster, on the openness or closeness to new members, type of the contributions of the partners and the other factors. The most reliable solution regarding the choice of the model of the functioning and management of the cluster has to be derived as well legal regulation of the legal form of the activity discussed. The advantages and disadvantages of two models of the cluster formation discussed. During experimental evaluation, the significance of criteria was determined and the expert evaluation on legal form for the development of clusters activities was performed. Foundation and management of the clusters are determined firstly by the fact that in one case a new established legal person performs the functions of the cluster coordinator while in another case one of the cluster participants performs the functions and partners legal cooperation determined by Agreement on Partnership. Article analyses the multi-criteria decisions-making to establish the cluster with the certain type of juridical form of legal person or to develop cluster management activities by the Partnership Agreement. The recommendations presented by application of MCDM calculus methods with aspect of percentage
Fully Band Resolved Scattering Rate in MgB2 Revealed by Nonlinear Hall Effect and Magnetoresistance Measurements
We have measured the normal state temperature dependence of the Hall effect
and magnetoresistance in epitaxial MgB2 thin films with variable disorders
characterized by the residual resistance ratio RRR ranging from 4.0 to 33.3. A
strong nonlinearity of the Hall effect and magnetoresistance have been found in
clean samples, and they decrease gradually with the increase of disorders or
temperature. By fitting the data to the theoretical model based on the
Boltzmann equation and ab initio calculations for a four-band system, for the
first time, we derived the scattering rates of these four bands at different
temperatures and magnitude of disorders. Our method provides a unique way to
derive these important parameters in multiband systems.Comment: 4 pages, 4 figure
Phononic Self energy effects and superconductivity in CaC
We study the graphite intercalated compound CaC by means of Eliashberg
theory, focusing on the anisotropy properties. An analysis of the
electron-phonon coupling is performed, and we define a minimal 6-band
anisotropy structure. Comparing with Superconducting Density Functional Theory
(SCDFT) the condition under which Eliashberg theory is able to reproduce the
SCDFT gap structure is determined, and we discuss the role of Coulomb
interactions. The Engelsberg-Schrieffer polaron structure is computed by
solving the Eliashberg equation on the Matsubara axis and analytically
continuing it to the full complex plane. This reveals the polaronic
quasiparticle bands anisotropic features as well as the interplay with
superconductivity
Sperm quality assessment in Ficopomatus enigmaticus (Fauvel, 1923): Effects of selected organic and inorganic chemicals across salinity levels
Contamination by organic and inorganic compounds remains one of the most complex problems in both brackish and marine environments, causing potential implications for the reproductive success and survival of several broadcast spawners. Ficopomatus enigmaticus is a tubeworm polychaete that has previously been used as a model organism for ecotoxicological analysis, due to its sensitivity and ecological relevance. In the present study, the effects of five trace elements (zinc, copper, cadmium, arsenic and lead), one surfactant (sodium dodecyl sulfate, SDS) and one polycyclic aromatic hydrocarbon (benzo(a)pyrene, B(a)P) on the sperm quality of F. enigmaticus were investigated. Sperm suspensions were exposed in vitro to different concentrations of each selected contaminant under four salinity conditions (10, 20, 30, 35). Possible adverse effects on sperm function were assessed by measuring oxidative stress, membrane integrity, viability and DNA damage. Sperm quality impairments induced by organic contaminants were more evident than those induced by inorganic compounds. SDS exerted the largest effect on sperm. In addition, F. enigmaticus sperm showed high tolerance to salinity variation, supporting the wide use of this species as a promising model organism for ecotoxicological assays. Easy and rapid methods on polychaete spermatozoids were shown to be effective as integrated sperm quality parameters or as an alternative analysis for early assessment of marine and brackish water pollution
- âŠ