F-theory and experiment

There is currently a wide gulf between string theory and experiment. This is compounded by the existence of a ‘landscape’ of solutions to the string theory equations of motion, many of which are in gross violation of experimental constraints. To make contact with experiment, it is then necessary to impose some additional criteria to find potentially realistic solutions. In this article we show that requiring that the forces of the Standard Model unify, while remaining decoupled from gravity, imposes sharp restrictions. A promising class of string based models which meet both these criteria are known as F-theory GUTs. We review the main ingredients of these constructions, and how they make contact with experiment.     

Laser produced plasma: A pumping source for cadmium photo-ionization laser

We report laser oscillations in Cd II on 4d ⁹5s ^{2 2} D _5/2 − 4d ¹⁰5p ² P _3/2 transition at 441.6 nm using laser produced tungsten plasma as a pumping source. Mach Zehnder interferometer is used to measure electron density. Design and working of the crossed heat pipe used in the studies is discussed.     

Development of the Monte Carlo model CASCADE-2004 of high-energy nuclear interactions

The Monte Carlo code CASCADE for the calculation of inelastic hadron- and nucleus-nucleus interactions at energies from several tens of MeV up to several tens of GeV and for modelling of nuclear-physical processes accompanying the transport of particles and nuclei in matter is improved by considering a more detailed model of decay of highly excited residual (after-intranuclear-cascade) nuclei. Results of calculations are in good agreement with experiment. However, there are some deviations for light-isotope production, which prompt the necessity of developing more correct models of evaporation and strong asymmetric high-energy fission.     

水平管油水两相流摩擦阻力特性实验研究

本文对水平管内油水液液两相流的摩擦阻力压降特性进行了实验研究。水平管实验段由有机玻璃管制成,内径为40mm。根据油水两相流流型的不同,通过建立物理模型或对实验数据的整理得到了各种典型流型下的摩擦阻力压降计算式。揭示了摩擦阻力压降随混合物速度和体积含水率等的变化规律。     

煤气管道沉积物的分析

以苯－乙醇为溶剂，在对煤气管道沉积物提取，分离后，采用２５ｍ＊０．２４ｍｍＩ．Ｄ．的石英毛细管ＯＶ－１０１柱进行了ＧＣ，ＧＣ－ＭＳ分析，鉴定出１９种有机成分，并用归一法作了定量分析，并用采用ＩＲ、点滴试验等方法对其无机物作了定性鉴定。     

Integrability of Generalized (Matrix) Ernst Equations in String Theory

We elucidate the integrability structures of the matrix generalizations of the Ernst equation for Hermitian or complex symmetric (d×d)-matrix Ernst potentials. These equations arise in string theory as the equations of motion for the truncated bosonic parts of the low-energy effective action for the respective dilaton and d×d matrix of moduli fields or for a string gravity model with a scalar (dilaton) field, a U(1) gauge vector field, and an antisymmetric 3-form field, all depending on only two space-time coordinates. We construct the corresponding spectral problems based on the overdetermined 2d×2d linear systems with a spectral parameter and the universal (i.e., solution-independent) structures of the canonical Jordan forms of their matrix coefficients. The additionally imposed existence conditions for each of these systems of two matrix integrals with appropriate symmetries provide specific (coset) structures of the related matrix variables. We prove that these spectral problems are equivalent to the original field equations, and we envisage an approach for constructing multiparametric families of their solutions. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 144, No. 2, pp. 214–225, August, 2005.     

广义二阶流体管内轴向流动

在流体的本构关系中引入分数阶导数运算，对于介于粘性与弹性之间的流体的描述更具有合理性。本文将这种关系引入二阶流体，研究其管内轴向流动。我们先求出了１／２阶导数的解析解，用以验证Ｌａｐｌａｃｅ数值反演的ＣＲＵＭＰ方法的有效性。然后用ＣＲＵＭＰ法分析二阶流体管内轴向流动的特征。分析表明粘弹性特征越明显的流体，其速度与应力对分数导数的阶数越具有敏感性。     

Krein's strings with singular left boundary

M. G. Krein established a one-to-one correspondence between strings with regular left boundary and their spectral measures. In this note we treat strings with a certain class of singular left boundary and obtain a condition that the spectral measure grows polynomially.     

An integer linear programming approach for approximate string comparison

We introduce a problem called maximum common characters in blocks (MCCB), which arises in applications of approximate string comparison, particularly in the unification of possibly erroneous textual data coming from different sources. We show that this problem is NP-complete, but can nevertheless be solved satisfactorily using integer linear programming for instances of practical interest. Two integer linear formulations are proposed and compared in terms of their linear relaxations. We also compare the results of the approximate matching with other known measures such as the Levenshtein (edit) distance.     

Radiation beyond four space-time dimensions

We present a set of formulas describing classical radiation of a rank-s tensor field from an accelerated pointlike source in a flat space-time of an arbitrary even dimension d. These formulas allow straightforwardly and algorithmically evaluating the total intensity and radiated momentum for any s and d by hand or using a computer. The practical application of the obtained results is limited for s > 1 because the energy-momentum tensor for the pointlike source is not conserved. This usually means that contributions to the radiation from tensions of the forces causing the acceleration of the radiation source cannot be neglected. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 156, No. 2, pp. 282–291, August, 2008.