Factorization and infrared properties of non-perturbative contributions to DIS structure functions

In this paper we present a new derivation of the QCD factorization. We deduce the k_T- and collinear factorizations for the DIS structure functions by consecutive reductions of a more general theoretical construction. We begin by studying the amplitude of the forward Compton scattering off a hadron target, representing this amplitude as a set of convolutions of two blobs connected by the simplest, two-parton intermediate states. Each blob in the convolutions can contain both the perturbative and non-perturbative contributions. We formulate conditions for separating the perturbative and non-perturbative contributions and attributing them to the different blobs. After that the convolutions correspond to the QCD factorization. Then we reduce this totally unintegrated (basic) factorization first to the k_T- factorization and finally to the collinear factorization. In order to yield a finite expression for the Compton amplitude, the integration over the loop momentum in the basic factorization must be free of both ultraviolet and infrared singularities. This obvious mathematical requirement leads to theoretical restrictions on the non-perturbative contributions (parton distributions) to the Compton amplitude and the DIS structure functions related to the Compton amplitude through the Optical theorem. In particular, our analysis excludes the use of the singular factors x^{-a} (with a > 0) in the fits for the quark and gluon distributions because such factors contradict to the integrability of the basic convolutions for the Compton amplitude. This restriction is valid for all DIS structure functions in the framework of both the k_T- factorization and the collinear factorization if we attribute the perturbative contributions only to the upper blob.Comment: 19 pages, 6 figure

Asymptotic high energy behavior of the deeply virtual Compton scattering amplitude

We compute the deeply virtual Compton scattering (DVCS) amplitude for forward and backward scattering in the asymptotic limit. Since this calculation does not assume ordering of the transverse momenta, it includes important logarithmic contributions that are beyond those summed by the DGLAP evolution. These contributions lead to a power-like behavior for the forward DVCS amplitude.Comment: Latex, 22 pages, 5 Figures; references enhanced; typos correcte

Resummation of double logarithms in electroweak high energy processes

At future linear $e^+e^-$ collider experiments in the TeV range, Sudakov double logarithms originating from massive boson exchange can lead to significant corrections to the cross sections of the observable processes. These effects are important for the high precision objectives of the Next Linear Collider. We use the infrared evolution equation, based on a gauge invariant dispersive method, to obtain double logarithmic asymptotics of scattering amplitudes and discuss how it can be applied, in the case of broken gauge symmetry, to the Standard Model of electroweak processes. We discuss the double logarithmic effects to both non-radiative processes and to processes accompanied by soft gauge boson emission. In all cases the Sudakov double logarithms are found to exponentiate. We also discuss double logarithmic effects of a non-Sudakov type which appear in Regge-like processes.Comment: 26 pages, 3 figures, Latex2

Magnetron sputtering in rigid optical solar reflectors production

Magnetron sputtering was applied to meet the growing need for glass optical solar reflectors. This plasma method provided more uniform deposition of the silver based coating on glass substrates resulted in decrease of defective reflectors fraction down to 5%. For instance, such parameter of resistive evaporation was of 30%. Silver film adhesion to glass substrate was enhanced with indium tin oxide sublayer. Sunlight absorption coefficient of these rigid reflectors was 0.081-0.083

Soil cover structure and transformation of morphometric parameters of Haplic Chernozems under no-tillage

The results of the field experiment have been analyzed, it was set up on two experimental fields (with an area of 2.4 hectares each), where two different agricultural techniques – traditional and no-till – were applied. Diagnostics of morphometric parameters of typical chernozems such as: the thickness of the A1 horizon, A1 + AB horizons and the depth of carbonates reaction with 10% HCl, has shown that some changes in soils and soil cover had occurred in the fields over 8 years. The integral indicator of soil productivity is the thickness of the humus horizon, it demonstrated trends to decrease and increase in the soil cover structure of the experimental fields with different compositions of chernozem subtypes. The trends result from both climate change and periodic dry periods, which are not typical of the region, and from the change of traditional technology to no-till. The carbonates leaching from chernozem profiles in all variants of the experiment decreased, which correlates well with climatic indicators, changing with the seasons of the year. Chernozems with thin humus layaer and reacting with HCl close to the surface do not require liming. The revealed changes are not statistically significant, they reflect the resistance of chernozems to the variability of natural and anthropogenic factors of soil formation. Crop residues on the soil surface under no-tillage reduce physical evaporation, which contributes to moisture accumulation in the soil. The use of cover crops in winter also increases the moisture reserves, which are consumed by the plants during the summer growing season. Information on the transformation of morphometric parameters allows making temporal and spatial corrections in the applied agricultural practices (crop rotation, fertilization, the use of cover crops, herbicides and pesticides)

Variational description of Gibbs-non-Gibbs dynamical transitions for the Curie-Weiss model

We perform a detailed study of Gibbs-non-Gibbs transitions for the Curie-Weiss model subject to independent spin-flip dynamics ("infinite-temperature" dynamics). We show that, in this setup, the program outlined in van Enter, Fern\'andez, den Hollander and Redig can be fully completed, namely that Gibbs-non-Gibbs transitions are equivalent to bifurcations in the set of global minima of the large-deviation rate function for the trajectories of the magnetization conditioned on their endpoint. As a consequence, we show that the time-evolved model is non-Gibbs if and only if this set is not a singleton for some value of the final magnetization. A detailed description of the possible scenarios of bifurcation is given, leading to a full characterization of passages from Gibbs to non-Gibbs -and vice versa- with sharp transition times (under the dynamics Gibbsianness can be lost and can be recovered). Our analysis expands the work of Ermolaev and Kulske who considered zero magnetic field and finite-temperature spin-flip dynamics. We consider both zero and non-zero magnetic field but restricted to infinite-temperature spin-flip dynamics. Our results reveal an interesting dependence on the interaction parameters, including the presence of forbidden regions for the optimal trajectories and the possible occurrence of overshoots and undershoots in the optimal trajectories. The numerical plots provided are obtained with the help of MATHEMATICA.Comment: Key words and phrases: Curie-Weiss model, spin-flip dynamics, Gibbs vs. non-Gibbs, dynamical transition, large deviations, action integral, bifurcation of rate functio

Low-temperature dynamics of the Curie-Weiss Model: Periodic orbits, multiple histories, and loss of Gibbsianness

We consider the Curie-Weiss model at a given initial temperature in vanishing external field evolving under a Glauber spin-flip dynamics corresponding to a possibly different temperature. We study the limiting conditional probabilities and their continuity properties and discuss their set of points of discontinuity (bad points). We provide a complete analysis of the transition between Gibbsian and non-Gibbsian behavior as a function of time, extending earlier work for the case of independent spin-flip dynamics. For initial temperature bigger than one we prove that the time-evolved measure stays Gibbs forever, for any (possibly low) temperature of the dynamics. In the regime of heating to low-temperatures from even lower temperatures, when the initial temperature is smaller than the temperature of the dynamics, and smaller than 1, we prove that the time-evolved measure is Gibbs initially and becomes non-Gibbs after a sharp transition time. We find this regime is further divided into a region where only symmetric bad configurations exist, and a region where this symmetry is broken. In the regime of further cooling from low-temperatures there is always symmetry-breaking in the set of bad configurations. These bad configurations are created by a new mechanism which is related to the occurrence of periodic orbits for the vector field which describes the dynamics of Euler-Lagrange equations for the path large deviation functional for the order parameter. To our knowledge this is the first example of the rigorous study of non-Gibbsian phenomena related to cooling, albeit in a mean-field setup.Comment: 31 pages, 24 figure

Quantitative assessment of crop residues in no-till technology according to remote sensing data and field soil cover survey

The key feature of the no-till technology is the preservation of crop residues on the soil surface. Crop residues quantitative assessment is an important task when introducing technology into production. On the basis of field and remote sensing data, different approaches to this assessment are considered. The research was carried out in the Budennovsky district of the Stavropol Territory in the fields of farms using both traditional technology (TT) and no-till (ПП). Images of the Sentinel-2 system were used as remote sensing data, on the basis of which the spectral indices NDTI and NDVI were calculated. Three methods were used to estimate the projective cover by plant residues: 1) weight accounting of plant residues per unit area; 2) field determination of the projective cover by the method of line transects; 3) desk analysis of photographs of the soil surface. Based on the obtained results, models of the linear dependence of NDTI values on the projective cover of the soil surface with plant residues were constructed. The possibility of quantitative accounting of plant residues only on the basis of remote sensing data was also analyzed. The highest coefficient of determination (R2 = 0.97) with the smallest square root of the standard error (RMSE = 7.93) was obtained by modeling based on the analysis of photographs of the soil surface covered with plant residues. Based on the model of the dependence of NDTI values on the projective cover of plant residues obtained as a result of the analysis of photographs based on Sentinel -2 satellite data for the growing season 2020–2021, data were obtained on the dynamics of soil coverage with plant residues (CRC) on the scale of a single field an d different tillage technologies. As an approbation of the approach and an assessment of its use for solving production problems, the dynamics of the projective cover with plant residues was analyzed under different crops and different relief conditions. An analysis of the dynamics of CRC values made it possible to distinguish between different stages of crop cultivation under traditional technology (TT) and no-till (ПП), and also on the scale of an individual field revealed the heterogeneity of the projective soil cover with plant residues associated with the features of the mesorelief

Small x behavior of parton distributions. A study of higher twist effects

Higher twist corrections to the structure function F_2 at small x are studied for the case of a flat initial condition for the twist-two QCD evolution in the next-to-leading order approximation. We present an analytical parameterization of the contributions from the twist-two and higher twist operators of the Wilson operator product expansion. Higher twist terms are evaluated using two different approaches, one motivated by BFKL and the other motivated by the renormalon formalism. The results of the latter approach are in very good agreement with deep inelastic scattering data from HERA.Comment: 46 pages, 9 figures, typeset using REVTeX. Misprints corrected, new results, discussions, references and acknowledgements added, 2 pictures replaced. The conclusions remain unchange