28,995 research outputs found

    Double Ionisation in R-Matrix Theory Using a 2-electron Outer Region

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    We have developed a two-electron outer region for use within R-matrix theory to describe double ionisation processes. The capability of this method is demonstrated for single-photon double ionisation of He in the photon energy region between 80 eV to 180 eV. The cross sections are in agreement with established data. The extended RMT method also provides information on higher-order processes, as demonstrated by the identification of signatures for sequential double ionisation processes involving an intermediate He+^{+} state with n=2n=2.Comment: 5 pages, 4 figure

    On the Approximation Performance of Fictitious Play in Finite Games

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    We study the performance of Fictitious Play, when used as a heuristic for finding an approximate Nash equilibrium of a 2-player game. We exhibit a class of 2-player games having payoffs in the range [0,1] that show that Fictitious Play fails to find a solution having an additive approximation guarantee significantly better than 1/2. Our construction shows that for n times n games, in the worst case both players may perpetually have mixed strategies whose payoffs fall short of the best response by an additive quantity 1/2 - O(1/n^(1-delta)) for arbitrarily small delta. We also show an essentially matching upper bound of 1/2 - O(1/n)

    The potential role of genetic markers in talent identification and athlete assessment in elite sport

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    In elite sporting codes, the identification and promotion of future athletes into specialized talent pathways is heavily reliant upon objective physical, technical, and tactical characteristics, in addition to subjective coach assessments. Despite the availability of a plethora of assessments, the dependence on subjective forms of identification remain commonplace in most sporting codes. More recently, genetic markers, including several single nucleotide polymorphisms (SNPs), have been correlated with enhanced aerobic capacity, strength, and an overall increase in athletic ability. In this review, we discuss the effects of a number of candidate genes on athletic performance, across single-skilled and multifaceted sporting codes, and propose additional markers for the identification of motor skill acquisition and learning. While displaying some inconsistencies, both the ACE and ACTN3 polymorphisms appear to be more prevalent in strength and endurance sporting teams, and have been found to correlate to physical assessments. More recently, a number of polymorphisms reportedly correlating to athlete performance have gained attention, however inconsistent research design and varying sports make it difficult to ascertain the relevance to the wider sporting population. In elucidating the role of genetic markers in athleticism, existing talent identification protocols may significantly improve—and ultimately enable—targeted resourcing in junior talent pathways

    Study made of corrosion resistance of stainless steel and nickel alloys in nuclear reactor superheaters

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    Experiments performed under conditions found in nuclear reactor superheaters determine the corrosion rate of stainless steel and nickel alloys used in them. Electropolishing was the primary surface treatment before the corrosion test. Corrosion is determined by weight loss of specimens after defilming

    Monopole clusters, Z(2) vortices and confinement in SU(2)

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    We extend our previous study of magnetic monopole currents in the maximally Abelian gauge [hep-lat/9712003] to larger lattices at small lattice spacings (20^4 at beta = 2.5 and 32^4 at beta = 2.5115). We confirm that at these weak couplings there continues to be one monopole cluster that is very much longer than the rest and that the string tension, K, is entirely due to it. The remaining clusters are compact objects whose population as a function of radius follows a power law that deviates from the scale invariant form, but much too weakly to suggest a link with the analytically calculable size distribution of small instantons. We also search for traces of Z(2) vortices in the Abelian projected fields; either as closed loops of `magnetic' flux or through appropriate correlations amongst the monopoles. We find, by direct calculation, that there is no confining condensate of such flux loops. We also find, through the calculation of doubly charged Wilson loops within the monopole fields, that there is no suppression of the q=2 effective string tension out to at distances of at least r ~ 1.6/sqrt{K}, suggesting that if there are any vortices they are not encoded in the monopole fields.Comment: 26 pages of LaTeX and PostScript figure

    Beginning of stability theory for Polish Spaces

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    We consider stability theory for Polish spaces and more generally for definable structures. We succeed to prove existence of indiscernibles under reasonable conditions

    Renormalization of heavy-light currents in moving NRQCD

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    Heavy-light decays such as B→πℓνB \to \pi \ell \nu, B→K∗γB \to K^{*} \gamma and B→K(∗)ℓℓB \to K^{(*)} \ell \ell can be used to constrain the parameters of the Standard Model and in indirect searches for new physics. While the precision of experimental results has improved over the last years this has still to be matched by equally precise theoretical predictions. The calculation of heavy-light form factors is currently carried out in lattice QCD. Due to its small Compton wavelength we discretize the heavy quark in an effective non-relativistic theory. By formulating the theory in a moving frame of reference discretization errors in the final state are reduced at large recoil. Over the last years the formalism has been improved and tested extensively. Systematic uncertainties are reduced by renormalizing the m(oving)NRQCD action and heavy-light decay operators. The theory differs from QCD only for large loop momenta at the order of the lattice cutoff and the calculation can be carried out in perturbation theory as an expansion in the strong coupling constant. In this paper we calculate the one loop corrections to the heavy-light vector and tensor operator. Due to the complexity of the action the generation of lattice Feynman rules is automated and loop integrals are solved by the adaptive Monte Carlo integrator VEGAS. We discuss the infrared and ultraviolet divergences in the loop integrals both in the continuum and on the lattice. The light quarks are discretized in the ASQTad and highly improved staggered quark (HISQ) action; the formalism is easily extended to other quark actions.Comment: 24 pages, 11 figures. Published in Phys. Rev. D. Corrected a typo in eqn. (51

    Measurement of Xylary Fluid Movement in Elm by the Thermoelectric Method

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    The thermoelectric method was used to determine the effect of external conditions and diurnal variation on the direction of xylary fluid movement in elm branches. Upward movement was detected under conditions favoring normal transpirational rates. No movement was detected during darkness or rainy conditions. Possible downward movement of branch fluid was indicated during late afternoon. Further refinement of the technique is needed for clarifying the latter observation

    The effect of attenuation on gross earth models

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    In most recent free oscillation studies of the earth's interior the effect of absorption upon the eigenperiods of the earth has been ignored. This is equivalent to assuming that the earth is close to perfectly elastic. Since the actual earth is significantly anelastic over seismic frequencies, a frequency-dependent correction of the order of 1% must be applied to the normal mode periods in order that models based on those modes may be compared with body wave results. The eigenperiods of an earth model based on uncorrected data, model C2 (Anderson and Hart, 1976a), are adjusted for attenuation and then inverted to determine the resulting overall perturbation in the earth model. The corrected normal mode data as well as the uncorrected data can be fitted by a spherically symmetric earth model. The effect of including the attenuation term is to generally increase seismic velocities, particularly shear velocities, throughout the model. An important consequence of this change is to reduce or eliminate base line discrepancies between body wave results and normal mode results
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