On Dispersive and Classical Shock Waves in Bose-Einstein Condensates and Gas Dynamics

A Bose-Einstein condensate (BEC) is a quantum fluid that gives rise to interesting shock wave nonlinear dynamics. Experiments depict a BEC that exhibits behavior similar to that of a shock wave in a compressible gas, eg. traveling fronts with steep gradients. However, the governing Gross-Pitaevskii (GP) equation that describes the mean field of a BEC admits no dissipation hence classical dissipative shock solutions do not explain the phenomena. Instead, wave dynamics with small dispersion is considered and it is shown that this provides a mechanism for the generation of a dispersive shock wave (DSW). Computations with the GP equation are compared to experiment with excellent agreement. A comparison between a canonical 1D dissipative and dispersive shock problem shows significant differences in shock structure and shock front speed. Numerical results associated with the three dimensional experiment show that three and two dimensional approximations are in excellent agreement and one dimensional approximations are in good qualitative agreement. Using one dimensional DSW theory it is argued that the experimentally observed blast waves may be viewed as dispersive shock waves.Comment: 24 pages, 28 figures, submitted to Phys Rev

Принципы организации объектно-ориентированных систем обработки неформализованной информации

Рассматривается класс логико-аналитических систем, использующих специальные лингвистические процессоры и базы знаний (БЗ) для обработки потоков неформализованных документов с целью решения пользовательских задач. На первом этапе формализации текста документа извлекаются информационные объекты и связи, которые образуют структуры знаний и запоминаются в БЗ. На уровне БЗ организуются различные виды анализа и объектных поисков: поиск похожих объектов и ситуаций, поиск по связям и другие. Рассматриваются основные компоненты подобных систем, называемых объектно-ориентированными, их особенности при использовании в различных приложениях: при обработке криминальной информации, при автоматической формализации резюме (заявок на работу), в системах обработки СМИ с выделением террористических групп и их деяний.A class of the logical-analytical systems using special linguistic processors and knowledge bases is considered. Such systems are called object-oriented. These systems are employed for processing of the unstructured documents flow for the user problems decision. At the first stage the document text is formalized: information objects and links are extracted and transferred into the knowledge structures which are stored in the knowledge base (KB). At the level of KB various kinds of analysis and object search are organized: the search for similar objects and situations, the search on the basis of links and other types of search. The basic components of these systems, their main features and the particular use in different applications are considered.The system operation in the subject areas of criminal information processing, automatic formalization of summary texts (applications for work), mass media analysis for extracting information about terrorist formations and their activities are presented

Signatures of heavy Majorana neutrinos and HERA's isolated lepton events

The graph of neutrinoless double beta decay is applied to HERA and generalized to final states with any two charged leptons. Considered is the case in which one of the two escapes typical identification criteria and the case when a produced tau decays hadronically. Both possibilities give one isolated lepton with high transverse momentum, hadronic activity and an imbalance in transverse momentum. We examine the kinematical properties of these events and compare them with the high p_T isolated leptons reported by the H1 collaboration. Their positive charged muon events can be explained by the ``double beta'' process and we discuss possibilities for the precise determination which original final state produced the single isolated lepton. To confirm our hypothesis one should search in the data for high pseudorapidity and/or low p_T leptons or for additional separated jets.Comment: 19 pages with 14 figures, minor change

The Dipion Mass Spectrum In e+e- Annihilation and tau Decay: A Dynamical (rho0, omega, phi) Mixing Approach

We readdress the problem of finding a simultaneous description of the pion form factor data in e+e- annihilations and in tau decays. For this purpose, we work in the framework of the Hidden Local Symmetry (HLS) Lagrangian and modify the vector meson mass term by including the pion and kaon loop contributions. This leads us to define the physical rho, omega and phi fields as linear combinations of their ideal partners, with coefficients being meromorphic functions of s, the square of the 4--momentum flowing into the vector meson lines. This allows us to define a dynamical, i.e. s-dependent, vector meson mixing scheme. The model is overconstrained by extending the framework in order to include the description of all meson radiative (V P gamma and P gamma gamma couplings) and leptonic (Ve+e- couplings) decays and also the isospin breaking (omega/ phi --> pi+ pi-) decay modes. The model provides a simultaneous, consistent and good description of the e+e- and tau dipion spectra. The expression for pion form factor in the latter case is derived from those in the former case by switching off the isospin breaking effects specific to e+e- and switching on those for tau decays. Besides, the model also provides a good account of all decay modes of the form V P gamma, Pgamma gamma as well as the isospin breaking decay modes. It leads us to propose new reference values for the rho^0 --> e+ e- and omega --> pi+ pi- partial widths which are part of our description of the pion form factor. Other topics (phi --> K anti K, the rho meson mass and width parameters) are briefly discussed. Therefore, we confirm the 3.3 sigma discrepancy between the theoretical estimate of a_mu based on e+e- and its direct BNL measurement.Comment: 71 pages, 8 figures. Accepted by EPJ C. Version 3: correct minor typos, minor changes spread out into the text. Extension of Sections 12.2 and 12.3.5 and introduction of the new Appendix

Heavy Majorana neutrinos in e+e- colliders

We investigate possibilities for detecting heavy Majorana neutrinos ($N$'s) in $e^+e^-$ at LEP200 and future Linear Colliders. We concentrate on the processes where the pairs of intermediate heavy $N$'s produce a clear signal of total lepton number violation ($e^+e^- \to NN \to W^+l^-W^+l^{\prime -}$). Such a signal is not possible if the heavy neutrinos are of Dirac nature. Our approach is general in the sense that the intermediate $N$'s can be either on shell or off shell. Discussion of the relative numerical importance of the $s$ and the $t+u$ channels of the $NN$ production is also included.Comment: 11 pages, latex (revtex), 4 eps-figures, text slightly modified, appears in Physical Review Letters (June 7, 1999, issue

IFNβ Protects Neurons from Damage in a Murine Model of HIV-1 Associated Brain Injury.

Infection with human immunodeficiency virus-1 (HIV-1) causes brain injury. Type I interferons (IFNα/β) are critical mediators of any anti-viral immune response and IFNβ has been implicated in the temporary control of lentiviral infection in the brain. Here we show that transgenic mice expressing HIV-1 envelope glycoprotein 120 in their central nervous system (HIVgp120tg) mount a transient IFNβ response and provide evidence that IFNβ confers neuronal protection against HIVgp120 toxicity. In cerebrocortical cell cultures, neuroprotection by IFNβ against gp120 toxicity is dependent on IFNα receptor 1 (IFNAR1) and the β-chemokine CCL4, as IFNAR1 deficiency and neutralizing antibodies against CCL4, respectively, abolish the neuroprotective effects. We find in vivo that IFNβ mRNA is significantly increased in HIVgp120tg brains at 1.5, but not 3 or 6 months of age. However, a four-week intranasal IFNβ treatment of HIVgp120tg mice starting at 3.5 months of age increases expression of CCL4 and concomitantly protects neuronal dendrites and pre-synaptic terminals in cortex and hippocampus from gp120-induced damage. Moreover, in vivo and in vitro data suggests astrocytes are a major source of IFNβ-induced CCL4. Altogether, our results suggest exogenous IFNβ as a neuroprotective factor that has potential to ameliorate in vivo HIVgp120-induced brain injury

Signatures for Majorana neutrinos in e−γe^- \gamma collider

We study the possibilities to detect Majorana neutrinos in $e^- \gamma$ colliders for different center of mass energies. We study the $W^- W^- l_j^{+}(l_j^+\equiv e^+ ,\mu^+ ,\tau^+)$ final state which are, due to leptonic number violation, a clear signature for intermediate Majorana neutrino contribution. Such a signal (final lepton have the opposite charge of the initial lepton) is not possible if the heavy neutrinos are Dirac particles. In our calculation we use the helicity formalism to obtain analytic expressions for the amplitude and we have considered that the intermediate neutrinos can be either on shell or off shell. Finally we present our results for the total cross-section and for the angular distribution of the final lepton. We also include a discussion on the expected events number as a function of the input parameters.Comment: Latex file with 12 pages and 6 figures. Submited to Phys. Rev.