96 research outputs found
Instanton-induced contributions to structure functions of deep inelastic scattering
We identify and calculate the instanton-induced contributions to deep
inelastic scattering which correspond to nonperturbative exponential
corrections to the coefficient functions in front of parton distributions of
the leading twist.Comment: MPI-Ph/92-89 , LATEX, 15 pages, 3 figures incl. as uu-encoded fil
INSURANCE AS AN EFFECTIVE MECHANISM TO MINIMIZE RISKS AT THE ENTERPRISE
Purpose: The article analyzes the state of domestic insurance in agricultural enterprises, which is a complex type of property insurance, subspecies of which are insurance of crops, animals, commodity aquaculture, real estate and income of agricultural producers.
Methodology: Generally accepted methods and techniques of economic research were used in the study process: monographic (in the process of studying risk management theoretical foundations), statistical and economic (when studying trends of AIC enterprise development and functioning), design-constructive (when justifying and calculating indicators of enterprise functioning), abstract and logical (when generalizing conceptual and methodological approaches in identifying, analyzing and assessing risks), comparative analysis (synthesis of native and foreign risk management experience), various risk assessment methodologies.
Result: The economic risk passport is understood as a set of information about the risk area, risk criteria, as well as for instructions on the application of the necessary methods to manage or minimize the risk. The article presented a liquidity loss risk passport with one of the measures to minimize it - self-insurance.
Applications: This research can be used for universities, teachers, and students.
Novelty/Originality: In this research, the model of Insurance as an Effective Mechanism to Minimize Risks at the Enterprise is presented in a comprehensive and complete manner
Dispersive Shock Wave, Generalized Laguerre Polynomials and Asymptotic Solitons of the Focusing Nonlinear Schr\"odinger Equation
We consider dispersive shock wave to the focusing nonlinear Schr\"odinger
equation generated by a discontinuous initial condition which is periodic or
quasi-periodic on the left semi-axis and zero on the right semi-axis. As an
initial function we use a finite-gap potential of the Dirac operator given in
an explicit form through hyper-elliptic theta-functions. The paper aim is to
study the long-time asymptotics of the solution of this problem in a vicinity
of the leading edge, where a train of asymptotic solitons are generated. Such a
problem was studied in \cite{KK86} and \cite{K91} using Marchenko's inverse
scattering technics. We investigate this problem exceptionally using the
Riemann-Hilbert problems technics that allow us to obtain explicit formulas for
the asymptotic solitons themselves that in contrast with the cited papers where
asymptotic formulas are obtained only for the square of absolute value of
solution. Using transformations of the main RH problems we arrive to a model
problem corresponding to the parametrix at the end points of continuous
spectrum of the Zakharov-Shabat spectral problem. The parametrix problem is
effectively solved in terms of the generalized Laguerre polynomials which are
naturally appeared after appropriate scaling of the Riemann-Hilbert problem in
a small neighborhoods of the end points of continuous spectrum. Further
asymptotic analysis give an explicit formula for solitons at the edge of
dispersive wave. Thus, we give the complete description of the train of
asymptotic solitons: not only bearing envelope of each asymptotic soliton, but
its oscillating structure are found explicitly. Besides the second term of
asymptotics describing an interaction between these solitons and oscillating
background is also found. This gives the fine structure of the edge of
dispersive shock wave.Comment: 36 pages, 5 figure
Similarity transformations for Nonlinear Schrodinger Equations with time varying coefficients: Exact results
In this paper we use a similarity transformation connecting some families of
Nonlinear Schrodinger equations with time-varying coefficients with the
autonomous cubic nonlinear Schrodinger equation. This transformation allows one
to apply all known results for that equation to the non-autonomous case with
the additional dynamics introduced by the transformation itself. In particular,
using stationary solutions of the autonomous nonlinear Schrodinger equation we
can construct exact breathing solutions to multidimensional non-autonomous
nonlinear Schrodinger equations. An application is given in which we explicitly
construct time dependent coefficients leading to solutions displaying weak
collapse in three-dimensional scenarios. Our results can find physical
applicability in mean field models of Bose-Einstein condensates and in the
field of dispersion-managed optical systems
Даже простые процессы π-исчисления трудны для анализа
Mathematical models of distributed computations, based on the calculus of mobile processes (π-calculus) are widely used for checking the information security properties of cryptographic protocols. Since π-calculus is Turing-complete, this problem is undecidable in general case. Therefore, the study is carried out only for some special classes of π-calculus processes with restricted computational capabilities, for example, for non-recursive processes, in which all runs have a bounded length, for processes with a bounded number of parallel components, etc. However, even in these cases, the proposed checking procedures are time consuming. We assume that this is due to the very nature of the π -calculus processes. The goal of this paper is to show that even for the weakest model of passive adversary and for relatively simple protocols that use only the basic π-calculus operations, the task of checking the information security properties of these protocols is co-NP-complete.Математические модели распределенных вычислений, построенные на основе исчисления мобильных процессов (-исчисления), широко используются для проверки свойств информационной безопасности криптографических протоколов. Поскольку -исчисление является полной по Тьюрингу моделью вычислений, эта задача в общем случае алгоритмически неразрешима. Поэтому ее исследование проводится лишь для некоторых специальных классов процессов -исчисления с ограниченными вычислительными возможностями, например, для нерекурсивных процессов, в которых все вычисления имеют ограниченную длину, для процессов с ограниченным числом параллельных компонентов и др. Однако и в этих случаях предложенные разрешающие алгоритмы оказываются весьма трудоемкими. Мы полагаем, что это обусловлено самой природой процессов -исчисления. Цель данной работы — показать, что даже для наиболее слабой модели пассивного противника и для сравнительно простых протоколов, в которых используются лишь базовые операции -исчисления, задача проверки свойств информационной безопасности этих протоколов является co-NP-полной
Arctic climate change: observed and modelled temperature and sea-ice variability
Changes apparent in the arctic climate system in recent years require evaluation in a century-scale perspective in order to assess the Arctic's response to increasing anthropogenic greenhouse-gas forcing. Here, a new set of century- and multidecadal-scale observational data of surface air temperature (SAT) and sea ice is used in combination with ECHAM4 and HadCM3 coupled atmosphere-ice-ocean global model simulations in order to better determine and understand arctic climate variability. We show that two pronounced twentieth-century warming events, both amplified in the Arctic, were linked to sea-ice variability. SAT observations and model simulations indicate that the nature of the arctic warming in the last two decades is distinct from the early twentieth-century warm period. It is suggested strongly that the earlier warming was natural internal climate-system variability, whereas the recent SAT changes are a response to anthropogenic forcing. The area of arctic sea ice is furthermore observed to have decreased similar to8 x 10(5) km(2) (7.4%) in the past quarter century, with record-low summer ice coverage in September 2002. A set of model predictions is used to quantify changes in the ice cover through the twenty-first century, with greater reductions expected in summer than winter. In summer, a predominantly sea-ice-free Arctic is predicted for the end of this century
Collapse in boson-fermion mixtures with all-repulsive interactions
We describe the collapse of the bosonic component in a boson-fermion mixture
due to the pressure exerted on them by a large fermionic component, leading to
collapse in a system with all-repulsive interactions. We describe the phenomena
early collapse and of super-slow collapse of the mixture.Comment: 5 page
Boundary RG Flow Associated with the AKNS Soliton Hierarchy
We introduce and study an integrable boundary flow possessing an infinite
number of conserving charges which can be thought of as quantum counterparts of
the Ablowitz, Kaup, Newell and Segur Hamiltonians. We propose an exact
expression for overlap amplitudes of the boundary state with all primary states
in terms of solutions of certain ordinary linear differential equation. The
boundary flow is terminated at a nontrivial infrared fixed point. We identify a
form of whole boundary state corresponding to this fixed point.Comment: 54 page
GIADA microbalance measurements on board Rosetta: submicrometer- to micrometer-sized dust particle flux in the coma of comet 67P/Churyumov-Gerasimenko
Context. From August 2014 to September 2016, Rosetta escorted comet 67P/Churyumov-Gerasimenko (67P) during its journey around the Sun. One of the aims of Rosetta was to characterize cometary activity and the consequent formation of dust flux structures in cometary comae. Aims: We characterize and quantify the submicrometer- to micrometer-sized dust flux that may be shaped in privileged directions within the coma of 67P inbound to and outbound from perihelion. Methods: The in situ dust-measuring instrument GIADA, part of the Rosetta/ESA payload, consisted of three subsystems, one of which was the Micro Balance Subsystem (MBS), composed of five quartz crystal microbalances. From May 2014 to September 2016, MBS measured the submicrometer- to micrometer-sized deposited dust mass every 5 min. Results: We characterized the submicrometer- to micrometer-sized dust mass flux in the coma of 67P. The anti-sunward and the radial direction are preferred, and the flux is higher in the anti-sunward direction. The measured cumulative dust mass in the anti-sunward direction is 2.38 ± 0.04 × 10-7 kg, and in the radial direction, it is 1.18 ± 0.02 × 10-7 kg. We explain the anti-sunward dust flux as the effect of nonuniform gas emission between the night- and dayside of the nucleus, which acts in combination with the solar radiation pressure. We compared the cumulated dust mass of particles ≤5 μm with particles ≥100 μm. The retrieved ratio of ≈2% implies a differential size distribution index of ≈-3.0, which confirms that particles of size ≥0.1 mm dominate the dust coma cross-section of 67P during the entire orbit. Conclusions: Submicrometer- to micrometer-sized dust mass flux measurements were made for the first time from the arising of cometary activity until its extinction. They indicate that these particles do not provide a substantial optical scattering in the coma of 67P with respect to the scattering caused by millimeter-sized particles. In addition, MBS data reveal that the measured dust flux is highly anisotropic: anti-sunward plus radial
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