Space-Bounded Kolmogorov Extractors

An extractor is a function that receives some randomness and either "improves" it or produces "new" randomness. There are statistical and algorithmical specifications of this notion. We study an algorithmical one called Kolmogorov extractors and modify it to resource-bounded version of Kolmogorov complexity. Following Zimand we prove the existence of such objects with certain parameters. The utilized technique is "naive" derandomization: we replace random constructions employed by Zimand by pseudo-random ones obtained by Nisan-Wigderson generator.Comment: 12 pages, accepted to CSR201

Evolution and models for skewed parton distributions

We discuss the structure of the ``forward visible'' (FW) parts of double and skewed distributions related to usual distributions through reduction relations. We use factorized models for double distributions (DDs) f(x, alpha) in which one factor coincides with the usual (forward) parton distribution and another specifies the profile characterizing the spread of the longitudinal momentum transfer. The model DDs are used to construct skewed parton distributions (SPDs). For small skewedness, the FW parts of SPDs H(x, xi) can be obtained by averaging forward parton densities f(x- xi alpha) with the weight rho (alpha) coinciding with the profile function of the double distribution f(x, alpha) at small x. We show that if the x^n moments f_n (alpha) of DDs have the asymptotic (1-alpha^2)^{n+1} profile, then the alpha-profile of f (x,alpha) for small x is completely determined by small-x behavior of the usual parton distribution. We demonstrate that, for small xi, the model with asymptotic profiles for f_n (alpha) is equivalent to that proposed recently by Shuvaev et al., in which the Gegenbauer moments of SPDs do not depend on xi. We perform a numerical investigation of the evolution patterns of SPDs and gave interpretation of the results of these studies within the formalism of double distributions.Comment: 24 pages, Latex, 12 figure

Short lists with short programs in short time - a short proof

Bauwens, Mahklin, Vereshchagin and Zimand [ECCC TR13-007] and Teutsch [arxiv:1212.6104] have shown that given a string x it is possible to construct in polynomial time a list containing a short description of it. We simplify their technique and present a shorter proof of this result

Power-Law Wave Functions and Generalized Parton Distributions for Pion

We propose a model for generalized parton distributions of the pion based on the power-law ansatz for the effective light-cone wave function.Comment: 27 pages, Latex; Revised and Extended Version, to be published in Phys. Rev.

Private equity industry: Southwest firms draw on regional expertise

Neiman Marcus, Harrah’s, Petco, J. Crew—these well-known names are among the holdings of companies owned or co-owned by private equity (PE) firms in the Federal Reserve’s Eleventh District. The region is home to more than 175 PE firms, including the world’s third-largest, Fort Worth-based TPG Capital.[1] Together, these entities have raised more than $109 billion over the past 10 years and sit on$31 billion pending investment. ; While the PE business model goes back to the times of early seafaring enterprises funded by limited private partners, its modern U.S. iteration dates back to the 1950s and the first venture capital funds. More recently, the industry and its sometimes opaque operations have come under increased regulatory scrutiny amid concern about their riskiness and systemic importance to the financial system. Although detailed data are hard to come by, regionally based PE firms are distinguished from their counterparts nationwide by the sectors they favor.Investments ; Venture capital

Plasma measurements conducted in the vincinity of Venus on the spacecraft VENERA-4

Plasma flux measurements in vicinity of Venus by charged particle traps on Venera-4 spacecraf

On high Q2Q^{2} behavior of the pion form factor for transitions γ∗γ→π0\gamma^{\ast} \gamma \to \pi^{0} and γ∗γ∗→π0\gamma ^{\ast} \gamma^{\ast} \to \pi^{0} within the nonlocal quark-pion model

The behavior of the transition pion form factor for processes \gamma^*\gamma -> \pi^0 and \gamma^* \gamma^* -> \pi^0 at large values of space-like photon momenta is estimated within the nonlocal covariant quark-pion model. It is shown that, in general, the coefficient of the leading asymptotic term depends dynamically on the ratio of the constituent quark mass and the average virtuality of quarks in the vacuum and kinematically on the ratio of photon virtualities. The kinematic dependence of the transition form factor allows us to obtain the relation between the pion light-cone distribution amplitude and the quark-pion vertex function. The dynamic dependence indicates that the transition form factor \gamma^* \gamma -> \pi^0 at high momentum transfers is very sensitive to the nonlocality size of nonperturbative fluctuations in the QCD vacuum.Comment: LaTex file with 3 ps-figure