Zero curvature representation for a new fifth-order integrable system

In this brief note we present a zero-curvature representation for one of the new integrable system found by Mikhailov, Novikov and Wang in nlin.SI/0601046.Comment: 2 pages, LaTeX 2e, no figure

Representations of sl(2,?) in category O and master symmetries

We show that the indecomposable sl(2,?)-modules in the Bernstein-Gelfand-Gelfand category O naturally arise for homogeneous integrable nonlinear evolution systems. We then develop a new approach called the O scheme to construct master symmetries for such integrable systems. This method naturally allows computing the hierarchy of time-dependent symmetries. We finally illustrate the method using both classical and new examples. We compare our approach to the known existing methods used to construct master symmetries. For new integrable equations such as a Benjamin-Ono-type equation, a new integrable Davey-Stewartson-type equation, and two different versions of (2+1)-dimensional generalized Volterra chains, we generate their conserved densities using their master symmetries

Multiboson effects in multiparticle production

The influence of multiboson effects on pion multiplicities, single-pion spectra and two-pion correlation functions is discussed in terms of an analytically solvable model. The applicability of its basic factorization assumption is clarified. An approximate scaling of the basic observables with the phase space density is demonstrated in the low density (gas) limit. This scaling and also its violation at high densities due to the condensate formation is described by approximate analytical formulae which allow, in principle, for the identification of the multiboson effects among others. For moderate densities indicated by the experimental data, a fast saturation of multiboson effects with the number of contributing cumulants is obtained, allowing for the account of these effects in realistic transport code simulations. At high densities, the spectra are mainly determined by the universal condensate term and the initially narrow Poisson multiplicity distribution approaches a wide Bose-Einstein one. As a result, the intercepts of the inclusive and fixed-$n$ correlation functions (properly normalized to 1 at large relative momenta) approach 2 and 1, respectively and their widths logarithmically increase with the increasing phase space density. It is shown that the neglect of energy-momentum constraints in the model is justified except near a multipion threshold, where these constraints practically exclude the possibility of a very cold condensate production. It is argued that spectacular multiboson effects are likely to be observed only in the rare events containing sufficiently high density (speckle) fluctuations.Comment: 30 pages including 10 figures, LaTex, a revised version of SUBATECH 99-04 (aps1999_mar21_001) resubmitted to Phys. Rev. C; Chapter II made shorter, figure description made more clear, a comparison with most recent works added in Chapter V

Assessment of Climatic Conditions for Siberian Reindeer Herding on the Basis of Heat Balance Modelling

The purpose of the research is to assess suitable climatic conditions for traditional herding of reindeer by Indigenous people in different areas of Siberia. A сomputer simulation model allowed us to calculate reindeer’s heat balance according to a number of meteorological indices; it was used to assess climatic conditions in 70 localities. To show the impact of climatic conditions on reindeer’s well-being, we introduce the notion of the thermal comfort index (Kt). The best environmental conditions for reindeer are in the areas where Kt takes the highest values in winter and the lowest ones in summer. We showed the results of the reindeer heat balance computer simulation on two maps visualising the average Kt values in summer and in winter. Finally, using official statistics, we calculated the number of reindeer per 100 km2 in areas with different types of traditional reindeer herding. The territories with the largest domesticated reindeer populations per 100 km2 in the two major tundra reindeer breeding areas (Samoed and Chukchi-Koriak types of reindeer herding) are located in the regions with the relatively low value of Kt in summer and high in winter. In the taiga, Kt is relatively high in summer, and reindeer herding (Tungus and Saian types) is developed mostly in highlands, where the summer Kt is lower than in flatlands because of the vertical temperature gradient. The results obtained prove that thermal conditions are extremely important for traditional reindeer herding.L’objectif de cette recherche consiste à évaluer les conditions climatiques convenables à l’élevage traditionnel des rennes par les peuples indigènes de différentes régions de la Sibérie. Au moyen d’un modèle de simulation informatisé, nous avons calculé le bilan thermique des rennes en fonction de plusieurs indices météorologiques. Nous avons évalué les conditions climatiques de 70 localités. Pour illustrer les incidences des conditions climatiques sur le bien-être des rennes, nous avons introduit la notion de l’indice du confort thermique (Kt). Pour le renne, les meilleures conditions environnementales sont celles pour lesquelles Kt a les plus grandes valeurs en hiver, et les moins grandes valeurs en été. Nous avons illustré les résultats de la simulation informatisée du bilan thermique du renne sur deux cartes permettant de visualiser les valeurs Kt moyennes de l’été et de l’hiver. Pour terminer, à l’aide de statistiques officielles, nous avons calculé le nombre de rennes par 100 km2 dans des zones ayant différents types d’élevage traditionnel de rennes. Les territoires comptant les plus grandes populations de rennes domestiqués par tranche de 100 km2 dans les deux grands secteurs de reproduction de la toundra (les types d’élevage Samoed et Chukchi-Koriak) se situent dans les régions où la valeur Kt est relativement basse l’été et élevée en hiver. Dans la taïga, le Kt est relativement élevé pendant l’été, et l’élevage des rennes (de types Tungus et Saian) est surtout développé dans les hautes terres, où la valeur Kt d’été est moins élevée que dans les plaines en raison du gradient thermique vertical. Les résultats obtenus prouvent que les conditions thermiques jouent un très grand rôle dans l’élevage traditionnel des rennes.Цель исследования состоит в оценке климатических условий для традиционного оленеводства коренных народов в разных областях Сибири. Использование имитационной компьютерной модели позволило по ряду метеорологических показателей рассчитать значения теплового баланса северного оленя для 70 географических пунктов. Чтобы отразить влияние климатических условий на организм оленя, мы ввели понятие коэффициент теплового комфорта (Kt). Самые благоприятные для северного оленя условия там, где Kt принимает наиболее высокие значения зимой и самые низкие значения летом. Мы отразили результаты компьютерного моделирования теплового баланса оленя на двух картах, отражающих средние значения Kt в летний и зимний периоды. Для интерпретации результатов мы рассчитали количество оленей на 100 км2 в ареалах с различными типами традиционного оленеводства, использовав данные официальной статистики. Оказалось, что в двух крупнейших областях тундрового оленеводства (самоедский и чукотско-корякский типы оленеводства) территории, с наибольшим числом домашних оленей на 100 км2, расположены в районах с относительно низкими значениями Kt летом и высокими зимой. В тайге (в ареалах тунгусского и саянского типов оленеводства) значения Kt летом сравнительно велики. Оленеводство здесь развивается в основном в районах, где есть высокие горы и из-за вертикального градиента температуры значения Kt летом понижены. Полученные результаты подтверждают значимость температурных условий для традиционного оленеводства

Vector, Axial, Tensor and Pseudoscalar Vacuum Susceptibilities

Using a recently developed three-point formalism within the method of QCD Sum Rules we determine the vacuum susceptibilities needed in the two-point formalism for the coupling of axial, vector, tensor and pseudoscalar currents to hadrons. All susceptibilities are determined by the space-time scale of condensates, which is estimated from data for deep inelastic scattering on nucleons

Why nonlocal recursion operators produce local symmetries: new results and applications

It is well known that integrable hierarchies in (1+1) dimensions are local while the recursion operators that generate them usually contain nonlocal terms. We resolve this apparent discrepancy by providing simple and universal sufficient conditions for a (nonlocal) recursion operator in (1+1) dimensions to generate a hierarchy of local symmetries. These conditions are satisfied by virtually all known today recursion operators and are much easier to verify than those found in earlier work. We also give explicit formulas for the nonlocal parts of higher recursion operators, Poisson and symplectic structures of integrable systems in (1+1) dimensions. Using these two results we prove, under some natural assumptions, the Maltsev--Novikov conjecture stating that higher Hamiltonian, symplectic and recursion operators of integrable systems in (1+1) dimensions are weakly nonlocal, i.e., the coefficients of these operators are local and these operators contain at most one integration operator in each term.Comment: 10 pages, LaTeX 2e, final versio

Nonlinear electromagnetic response of graphene: Frequency multiplication and the self-consistent-field effects

Graphene is a recently discovered carbon based material with unique physical properties. This is a monolayer of graphite, and the two-dimensional electrons and holes in it are described by the effective Dirac equation with a vanishing effective mass. As a consequence, electromagnetic response of graphene is predicted to be strongly non-linear. We develop a quasi-classical kinetic theory of the non-linear electromagnetic response of graphene, taking into account the self-consistent-field effects. Response of the system to both harmonic and pulse excitation is considered. The frequency multiplication effect, resulting from the non-linearity of the electromagnetic response, is studied under realistic experimental conditions. The frequency up-conversion efficiency is analysed as a function of the applied electric field and parameters of the samples. Possible applications of graphene in terahertz electronics are discussed.Comment: 14 pages, 7 figures, invited paper written for a special issue of JPCM "Terahertz emitters

Droplet motion driven by surface freezing or melting: A mesoscopic hydrodynamic approach

A fluid droplet may exhibit self-propelled motion by modifying the wetting properties of the substrate. We propose a novel model for droplet propagation upon a terraced landscape of ordered layers formed as a result of surface freezing driven by the contact angle dependence on the terrace thickness. Simultaneous melting or freezing of the terrace edge results in a joint droplet-terrace motion. The model is tested numerically and compared to experimental observations on long-chain alkane system in the vicinity of the surface melting point.Comment: 4 pages, 3 figure

Two-component generalizations of the Camassa-Holm equation

A classification of integrable two-component systems of non-evolutionary partial differential equations that are analogous to the Camassa-Holm equation is carried out via the perturbative symmetry approach. Independently, a classification of compatible pairs of Hamiltonian operators is carried out, which leads to bi-Hamiltonian structures for the same systems of equations. Some exact solutions and Lax pairs are also constructed for the systems considered

Formation of ions by high energy photons

We calculate the electron energy spectrum of ionization by a high energy photon, accompanied by creation of electron-positron pair. The total cross section of the process is also obtained. The asymptotics of the cross section does not depend on the photon energies. At the photon energies exceeding a certain value $\omega_0$ this appeares to to be the dominant mechanism of formation of the ions. The dependence of $\omega_0$ on the value of nuclear charge is obtained. Our results are consistent with experimental data.Comment: 16 pages, 6 figure