Generalization of the BLM procedure and its scales in any order of pQCD

The Brodsky--Lepage--Mackenzie procedure is sequentially and unambiguously extended to any fixed order of perturbative QCD beyond the so called ``large--\beta_0 approximation''. As a result of this procedure, the obtained perturbation series looks like a continued-fraction representation. A subsequent generalization of this procedure is developed, in order to optimize the convergence of the final series, along the lines of the Fastest Convergence Prescription. This generalized BLM procedure is applied to the Adler D function and also to R_{e^+e^-} in QCD at N$^3$LO. A further extension of the sequential BLM is presented which makes use of additional parameters to optimize the convergence of the power-series at any fixed order of expansion.Comment: 24 pages, JHEP3, 4 figures are enclosed as eps-file, final version to be published in JHE

Characteristics of Conservation Laws for Difference Equations

Each conservation law of a given partial differential equation is determined (up to equivalence) by a function known as the characteristic. This function is used to find conservation laws, to prove equivalence between conservation laws, and to prove the converse of Noether's Theorem. Transferring these results to difference equations is nontrivial, largely because difference operators are not derivations and do not obey the chain rule for derivatives. We show how these problems may be resolved and illustrate various uses of the characteristic. In particular, we establish the converse of Noether's Theorem for difference equations, we show (without taking a continuum limit) that the conservation laws in the infinite family generated by Rasin and Schiff are distinct, and we obtain all five-point conservation laws for the potential Lotka-Volterra equation

Generalized Drinfeld-Sokolov Reductions and KdV Type Hierarchies

Generalized Drinfeld-Sokolov (DS) hierarchies are constructed through local reductions of Hamiltonian flows generated by monodromy invariants on the dual of a loop algebra. Following earlier work of De Groot et al, reductions based upon graded regular elements of arbitrary Heisenberg subalgebras are considered. We show that, in the case of the nontwisted loop algebra $\ell(gl_n)$, graded regular elements exist only in those Heisenberg subalgebras which correspond either to the partitions of $n$ into the sum of equal numbers $n=pr$ or to equal numbers plus one $n=pr+1$. We prove that the reduction belonging to the grade $1$ regular elements in the case $n=pr$ yields the $p\times p$ matrix version of the Gelfand-Dickey $r$-KdV hierarchy, generalizing the scalar case $p=1$ considered by DS. The methods of DS are utilized throughout the analysis, but formulating the reduction entirely within the Hamiltonian framework provided by the classical r-matrix approach leads to some simplifications even for $p=1$.Comment: 43 page

The B-Meson Distribution Amplitude in QCD

The B-meson distribution amplitude is calculated using QCD sum rules. In particular we obtain an estimate for the integral relevant to exclusive B-decays \lambda_B = 460 \pm 110 MeV at the scale 1 GeV. A simple QCD-motivated parametrization of the distribution amplitude is suggested.Comment: 17 pages, 8 figures, Latex styl

Observation of KS0K_S^0 semileptonic decays with CMD-2 detector

The decay $K_S^0 \to \pi e \nu$ has been observed by the CMD-2 detector at the e^+e^- collider VEPP-2M at Novosibirsk. Of 6 million produced $K_L^0K_S^0$ pairs, $75 \pm 13$ events of the $K_S^0 \to \pi e \nu$ decay were selected. The corresponding branching ratio is $B(K_S^0 \to \pi e \nu)=(7.2 \pm 1.4)\times10^{-4}$. This result is consistent with the evaluation of $B(K_S^0 \to \pi e \nu)$ from the $K_L^0$ semileptonic rate and $K_S^0$ lifetime assuming $\Delta S=\Delta Q$ .Comment: 7 pages, 6 figures, LaTex2e. Submitted to Phys.Lett.

Alloying and modification of stainless steels by powerful plasma streams

The stainless steel surfaces coated of tungsten have been alloyed and modified with powerful QSPA Kh-50 plasma streams. The plasma streams exposures result in modification of steel-based materials and formation of resolidified layers. The changes of substrate texture were also registered. Phase characterized by body-centered cubic lattice appeared due to recrystallization of affected material. Thus, the favorable conditions were created for penetration of tungsten into the stainless steel bulk. Growth of lattice parameter was observed as result of plasma irradiation of coated samples. It's indication of tungsten penetration into the depth of substrates.Поверхности из нержавеющей стали с покрытием из вольфрама были легированы и модифицированы мощными плазменными потоками в КСПУ Х-50. Облучение потоком плазмы приводит к модификации материалов на основе сталей и формирование повторно затвердевшего слоя. Изменения текстуры подложки были также зарегистрированы. Фаза, которая характеризуется объёмно центрированной кубической решёткой, появилась вследствие рекристаллизации облучённого материала. Таким образом, были созданы необходимые условия для проникновения вольфрама в нержавеющую сталь. Рост параметра решётки наблюдался в результате плазменного облучения образцов с покрытием. Это указывает на проникновение вольфрама в глубину субстратов.Поверхні з нержавіючої сталі з покриттям з вольфраму були леговані і модифіковані потужними плазмовими потоками в КСПП Х-50. Опромінення потоком плазми призводить до модифікації матеріалів на основі сталей і формування повторно затверділого шару. Зміни текстури підкладки були також зареєстровані. Фаза, яка характеризується об'ємно центрованою кубічною решіткою, з'явилася внаслідок рекристалізації опроміненого матеріалу. Таким чином, були створені необхідні умови для проникнення вольфраму в нержавіючу сталь. Зростання параметра решітки спостерігався в результаті плазмового опромінення зразків з покриттям. Це вказує на проникнення вольфраму в глибину субстратів

A Giant Water Maser Flare in the Galactic Source IRAS 18316-0602

The results of long-term monitoring of the Galactic maser source IRAS 18316-0602 (G25.65+1.05) in the water-vapor line at frequency f = 22.235 GHz (6_16-5_23 transitioin) carried out on the 22-m Simeiz, 26-m HartRAO, and 26-m Torun radio telescopes are reported. The source has been episodically observed on the Simeiz telescope since 2000, with more regular observations beginning in 2017. A double flare was observed beginning in September 2017 and continuing to February 2018, which was the most powerful flare registered over the entire history of observations of this object. Most of the monitoring of the flare was carried out in a daily regime. Detailed analysis of the variations of the flux density, which reached a maximum value P ≈ 1.3 × 10^5 Jy, have led to important scientific conclusions about possible mechanisms for the emission in this water line. The exponential growth in the flux density in this double flare testifies that it was associated with a maser that was unsaturated right up to the maximum flux densities observed. An additional argument suggesting the maser was unsaturated is the relatively moderate degree of linear polarization (≈30%), nearly half the value displayed by the Galactic kilomasers in Orion KL. The accurate distance estimate for IRAS 18316-0602 (12.5 kpc) and the flux density at the flare maximum (≈1.3 × 10^5 Jy) makes this the most powerful Galactic kilomaser known. The double form of the flare with exponential rises in flux density rules out the possibility that the flare is the effect of directivity of a radiation beam relative to the observer. The physical nature of the flare is most likely related to internal parameters of the medium in which the maser clumps radiating in the water line are located. A rapid, exponential growth in the flux density of a kilomaser and associated exponential decays requires the presence of an explosive increase in the density of the medium and the photon flux, leading to an increase in the temperature by 10-40 K above the initial base level. A mechanism for the primary energy release in IRAS 18316-0602 is proposed, which is associated with a multiple massive star system located in a stage of evolution preceding its entry onto the main sequence. A flare in this object could initiate gravitational interaction between the central star and a massive companion at its periastron. The resulting powerful gravitational perturbation could lead to the ejection of the envelope of the central supermassive star, which gives rise to an explosive increase in the density and temperature of the associate gas-dust medium when it reaches the disk, where the maser clumps are located

Study of the radiative decay ϕ→ηγ\phi \to \eta \gamma with CMD-2 detector

Using the $1.9 pb^{-1}$ of data collected with the CMD-2 detector at VEPP-2M the decay mode $\phi \to \eta \gamma$, $\eta \to \pi^+\pi^-\pi^0$ has been studied. The obtained branching ratio is B($\phi \to \eta \gamma) = (1.18 \pm 0.03 \pm 0.06)$.Comment: 13 pages, 5 figures, LaTex2e, to be published in Phys. Lett.

Study of the process e+e- to pi+pi-pi+pi-pi0 with CMD-2 detector

The process e+e- to pi+ pi- pi+ pi- pi0 has been studied in the center of mass energy range 1280 -- 1380 MeV using 3.0 1/pb of data collected with the CMD-2 detector in Novosibirsk. Analysis shows that the cross section of the five pion production is dominated by the contributions of the eta pi+pi- and omega pi+pi- intermediate states.Comment: 8 pages, 3 figure. Submitted to Phys. Lett.

The classical R-matrix of AdS/CFT and its Lie dialgebra structure

The classical integrable structure of Z_4-graded supercoset sigma-models, arising in the AdS/CFT correspondence, is formulated within the R-matrix approach. The central object in this construction is the standard R-matrix of the Z_4-twisted loop algebra. However, in order to correctly describe the Lax matrix within this formalism, the standard inner product on this twisted loop algebra requires a further twist induced by the Zhukovsky map, which also plays a key role in the AdS/CFT correspondence. The non-ultralocality of the sigma-model can be understood as stemming from this latter twist since it leads to a non skew-symmetric R-matrix.Comment: 22 pages, 2 figure