Giant dispersion of critical currents in superconductor with fractal clusters of a normal phase

The influence of fractal clusters of a normal phase on the dynamics of a magnetic flux trapped in a percolative superconductor is considered. The critical current distribution and the current-voltage characteristics of fractal superconducting structures in the resistive state are obtained for an arbitrary fractal dimension of the cluster boundaries. The range of fractal dimensions, where the dispersion of critical currents becomes infinite, is found. It is revealed that the fractality of clusters depresses of the electric field caused by the magnetic flux motion thus increasing the critical current value. It is expected that the maximum current-carrying capability of a superconductor can be achieved in the region of giant dispersion of critical currents.Comment: 7 pages with 3 figure

Realistic calculations of nuclear disappearance lifetimes induced by neutron-antineutron oscillations

Realistic calculations of nuclear disappearance lifetimes induced by neutron-antineutron oscillations are reported for oxygen and iron, using antineutron nuclear potentials derived from a recent comprehensive analysis of antiproton atomic X-ray and radiochemical data. A lower limit of 3.3 x 10E8 s on the neutron-antineutron oscillation time is derived from the Super-Kamiokande I new lower limit of 1.77 x 10E32 yr on the neutron lifetime in oxygen. Antineutron scattering lengths in carbon and nickel, needed in trap experiments using ultracold neutrons, are calculated from updated antinucleon optical potentials at threshold, with results shown to be largely model independent.Comment: version matching PRD publication, typos and references correcte

Cosmic Coincidence and Asymmetric Dark Matter in a Stueckelberg Extension

We discuss the possibility of cogenesis generating the ratio of baryon asymmetry to dark matter in a Stueckelberg U(1) extension of the standard model and of the minimal supersymmetric standard model. For the U(1) we choose $L_{\mu}-L_{\tau}$ which is anomaly free and can be gauged. The dark matter candidate arising from this extension is a singlet of the standard model gauge group but is charged under $L_{\mu}-L_{\tau}$. Solutions to the Boltzmann equations for relics in the presence of asymmetric dark matter are discussed. It is shown that the ratio of the baryon asymmetry to dark matter consistent with the current WMAP data, i.e., the cosmic coincidence, can be successfully explained in this model with the depletion of the symmetric component of dark matter from resonant annihilation via the Stueckelberg gauge boson. For the extended MSSM model it is shown that one has a two component dark matter picture with asymmetric dark matter being the dominant component and the neutralino being the subdominant component (i.e., with relic density a small fraction of the WMAP cold dark matter value). Remarkably, the subdominant component can be detected in direct detection experiments such as SuperCDMS and XENON-100. Further, it is shown that the class of Stueckelberg models with a gauged $L_{\mu}-L_{\tau}$ will produce a dramatic signature at a muon collider with the $\sigma(\mu^+\mu^-\to \mu^+\mu^-,\tau^+\tau^-)$ showing a detectable $Z'$ resonance while $\sigma(\mu^+\mu^-\to e^+e^-)$ is devoid of this resonance. Asymmetric dark matter arising from a $U(1)_{B-L}$ Stueckelberg extension is also briefly discussed. Finally, in the models we propose the asymmetric dark matter does not oscillate and there is no danger of it being washed out from oscillations.Comment: 36 pages, 7 figure

Информационная поддержка анализа навыков и умений контингента студентов высшего учебного заведения

In the below article, the application of the fuzzy logical conclusion method is considered as decision-maker in the process of analyzing the students skills and abilities based on the requirements of potential employers, in order to reduce the time of the first interview for potential candidates on a vacant position. When analyzing the results of the assessment of the competence of university students, a certain degree of fuzziness arises. In modern practice, fuzzy logic is used in many different assessment methods, including questioning, interviewing, testing, descriptive method, classification method, pairwise comparison, rating method, business games competence models, and the like. Each of the methods has its advantages and disadvantages, but they are effective only as part of a unified personnel management system. As a method for implementing a systematic approach to the assessment of the contingent of students, it is proposed to use fuzzy logic, a mathematical apparatus that allows you to build a model of an object based on fuzzy judgments. The use of fuzzy logic, the mathematical apparatus of which allows you to build a model of the object, based on fuzzy reasoning and rules. The most important condition for creating such a model is to translate the fuzzy, qualitative assessments used by man into the language of mathematics, which will be understood by the computer. The most used are fuzzy inferences using the Mamdani and Sugeno methods. In a fuzzy inference of the Mamdani type, the value of the output variable is given by fuzzy terms, in the conclusion of the Sugeno type, as a linear combination of the input variables. Research in the field of application of fuzzy logic in socio-economic systems suggests that it can be used to assess the competencies of university students.В данной работе рассмотрено использование метода нечеткого логического вывода для поддержки принятия решения в задачах анализа навыков и умений контингента студентов исходя из требований потенциальных работодателей, с целью уменьшения времени на первичную обработку информации касательно потенциальных кандидатов на вакантную должность. При анализе результатов оценки компетентности студентов вузов возникает определенная степень нечеткости. В современной практике нечеткая логика применяется во многих различных методах оценки, в том числе анкетирование, интервью, тестирование, описательный метод, метод классификации, парное сравнение, рейтинговый метод, деловые игры модели компетентности и тому подобное. Каждый из методов имеет свои преимущества и недостатки, но эффективны они только в составе единой системы управления персоналом. Как метод для реализации системного подхода к оценке контингента студентов предложено использовать нечеткую логику, математический аппарат, который позволяет построить модель объекта, основанную на нечетких суждениях. Использование нечеткой логики, математический аппарат которой позволяет построить модель объекта, основываясь на нечетких рассуждениях и правилах. Важнейшее условие создания такой модели заключается в том, чтобы перевести нечеткие, качественные оценки, применяемые человеком, на язык математики, которая будет понятна вычислительной машине. Наиболее используемыми являются нечеткие выводы с помощью способов Мамдани и Сугено. В нечетком выводе типа Мамдани значение выходной переменной задаются нечеткими термами, в заключении типа Сугено – как линейная комбинация входных переменных. Исследования в области применения нечеткой логики в социоэкономических системах позволяют говорить о возможности ее использования для оценки компетенций студентов вузов

Longitudinal Hadronic Shower Development in a Combined Calorimeter

This work is devoted to the experimental study of the longitudinal hadronic shower development in the ATLAS barrel combined prototype calorimeter consisting of the lead-liquid argon electromagnetic part and the iron-scintillator hadronic part. The results have been obtained on the basis of the 1996 combined test beam data which have been taken on the H8 beam of the CERN SPS, with the pion beams of 10, 20, 40, 50, 80, 100, 150 and 300 GeV/c. The degree of description of generally accepted Bock parameterization of the longitudinal shower development has been investigated. It is shown that this parameterization does not give satisfactory description for this combined calorimeter. Some modification of this parameterization, in which the e/h ratios of the compartments of the combined calorimeter are used, is suggested and compared with the experimental data. The agreement between such parameterization and the experimental data is demonstrated.Comment: Latex, 21 pages, 10 figure

Non-compensation of an Electromagnetic Compartment of a Combined Calorimeter

The method of extraction of the $e/h$ ratio, the degree of non-compensation, of the electromagnetic compartment of the combined calorimeter is suggested. The $e/h$ ratio of $1.74\pm0.04$ has been determined on the basis of the 1996 combined calorimeter test beam data. This value agrees with the prediction that $e/h > 1.7$ for this electromagnetic calorimeter.Comment: LATEX, 17 pages, 7 figure

Non-perturbative proton stability

Proton decay is a generic prediction of GUT models and is therefore an important channel to detect the existence of unification or to set limits on GUT models. Current bounds on the proton lifetime are around 10^33 years, which sets stringent limits on the GUT scale. These limits are obtained under `reasonable' assumptions about the size of the hadronic matrix elements. In this paper we present a non-perturbative calculation of the hadronic matrix elements within the chiral bag model of the proton. We argue that there is an exponential suppression of the matrix elements, due to non-perturbative QCD, that stifles proton decay by orders of magnitude -- potentially O(10^-10). This suppression is present for small quark masses and is due to the chiral symmetry breaking of QCD. Such a suppression has clear implications for GUT models and could resuscitate several scenarios