Determination of the local structure of Sr2−x_{2-x}Mx_xIrO4_4 (M = K, La) as a function of doping and temperature

The local structure of correlated spin-orbit insulator Sr$_{2-x}$M$_x$IrO$_4$ (M = K, La) has been investigated by Ir L$_3$-edge extended x-ray absorption fine structure measurements. The measurements were performed as a function of temperature for different dopings induced by substitution of Sr with La or K. It is found that Ir-O bonds have strong covalency and they hardly show any change across the N\'eel temperature. In the studied doping range, neither Ir-O bonds nor their dynamics, measured by their mean square relative displacements, show any appreciable change upon carrier doping, indicating possibility of a nanoscale phase separation in the doped system. On the other hand, there is a large increase of the static disorder in Ir-Sr correlation, larger for K doping than La doping. Similarities and differences with respect to the local lattice displacements in cuprates are briefly discussed.Comment: Main text: 6 pages, 4 figures, Supplemental information: 2 pages, 2 figure

Measurement of K^+ \to \pi^0 \mu^+ \nu \gamma decay using stopped kaons

The K^+ \to \pi^0 \mu^+ \nu \gamma ($K_{\mu 3 \gamma}$) decay has been measured with stopped positive kaons at the KEK 12 GeV proton synchrotron. A $K_{\mu 3 \gamma}$ sample containing 125 events was obtained. The partial branching ratio $Br(K_{\mu 3 \gamma}, E_{\gamma}>30 {\rm MeV}, \theta_{\mu^+ \gamma}>20^{\circ})$ was found to be $[2.4 \pm 0.5(stat) \pm 0.6(syst)]\times 10^{-5}$, which is in good agreement with theoretical predictions.Comment: 12 pages, 3 figures, to be published in Physics Letters

Generalized Farey trees, transfer Operators and phase transitions

We consider a family of Markov maps on the unit interval, interpolating between the tent map and the Farey map. The latter map is not uniformly expanding. Each map being composed of two fractional linear transformations, the family generalizes many particular properties which for the case of the Farey map have been successfully exploited in number theory. We analyze the dynamics through the spectral analysis of generalized transfer operators. Application of the thermodynamic formalism to the family reveals first and second order phase transitions and unusual properties like positivity of the interaction function.Comment: 39 pages, 10 figure

Definitions of terms relating to individual macromolecules, macromolecular assemblies, polymer solutions, and amorphous bulk polymers (IUPAC Recommendations 2014)

This document defines terms relating to the properties of individual macromolecules, macromolecular assemblies, polymer solutions, and amorphous bulk polymers. In the section on polymer solutions and amorphous bulk polymers, general and thermodynamic terms, dilute solutions, phase behaviour, transport properties, scattering methods, and separation methods are considered. The recommendations are a revision and expansion of the IUPAC terminology published in 1989 dealing with individual macromolecules, macromolecular assemblies, and dilute polymer solutions. New terms covering the principal theoretical and experimental developments that have occurred over the intervening years have been introduced. Polyelectrolytes are not included.△1143Ysciescopu

Measurement of direct photon emission in K+→π+π0γK^+ \to \pi^+ \pi^0 \gamma decay using stopped positive kaons

The radiative decay $K^+ \to \pi^+ \pi^0 \gamma$ ($K_{\pi 2 \gamma}$) has been measured with stopped positive kaons. A $K_{\pi 2 \gamma}$ sample containing 4k events was analyzed, and the $K_{\pi 2 \gamma}$ branching ratio of the direct photon emission process was determined to be $[6.1\pm2.5({\rm stat})\pm1.9({\rm syst})]\times 10^{-6}$. No interference pattern with internal bremsstrahlung was observed.Comment: 12 pages, 6 figures, 2 tables, to be published in Phys. Lett.

Superconductivity in a new layered triangular-lattice system Li2IrSi2

We report on the crystal structure and superconducting properties of a novel iridium-silicide, namely Li2IrSi2. It has a Ag2NiO2-type structure (space group R-3m) with the lattice parameters a = 4.028 30(6) Å and c = 13.161 80(15) Å. The crystal structure comprises IrSi2 and double Li layers stacked alternately along the c-axis. The IrSi2 layer includes a two-dimensional Ir equilateral-triangular lattice. Electrical resistivity and static magnetic measurements revealed that Li2IrSi2 is a type-II superconductor with critical temperature (Tc) of 3.3 K. We estimated the following superconducting parameters: lower critical field Hc1(0) ~ 42 Oe, upper critical field Hc2(0) ~ 1.7 kOe, penetration depth λ0 ~ 265 nm, coherence length ξ0 ~ 44 nm, and Ginzburg–Landau parameter κGL ~ 6.02. The specific-heat data suggested that superconductivity in Li2IrSi2 could be attributed to weak-coupling Cooper pairs

Photoproduction of Lambda(1405) and Sigma^{0}(1385) on the proton at E_\gamma = 1.5-2.4 GeV

Differential cross sections for $\gamma p \to K^+\Lambda(1405)$ and $\gamma p \to K^+\Sigma^0(1385)$ reactions have been measured in the photon energy range from 1.5 to 2.4 GeV and the angular range of $0.8<\cos(\Theta)<1.0$ for the $K^+$ scattering angle in the center-of-mass system. This data is the first measurement of the $\Lambda(1405)$ photoproduction cross section. The lineshapes of \LamS measured in $\Sigma^+\pi^-$ and $\Sigma^-\pi^+$ decay modes were different with each other, indicating a strong interference of the isospin 0 and 1 terms of the $\Sigma\pi$ scattering amplitudes. The ratios of \LamS production to \SigS production were measured in two photon energy ranges: near the production threshold ($1.5<E_\gamma<2.0$ GeV) and far from it ($2.0 <E_\gamma<2.4$ GeV). The observed ratio decreased in the higher photon energy region, which may suggest different production mechanisms and internal structures for these hyperon resonances

Numerical solution of a pursuit-evasion differential game involving two spacecraft in low earth orbit

This paper considers a spacecraft pursuit-evasion problem taking place in low earth orbit. The problem is formulated as a zero-sum differential game in which there are two players, a pursuing spacecraft that attempts to minimize a payoff, and an evading spacecraft that attempts to maximize the same payoff. We introduce two associated optimal control problems and show that a saddle point for the differential game exists if and only if the two optimal control problems have the same optimal value. Then, on the basis of this result, we propose two computational methods for determining a saddle point solution: a semi-direct control parameterization method (SDCP method), which is based on a piecewise-constant control approximation scheme, and a hybrid method, which combines the new SDCP method with the multiple shooting method. Simulation results show that the proposed SDCP and hybrid methodsare superior to the semi-direct collocation nonlinear programming method (SDCNLP method), which is widely used to solve pursuit-evasion problems in the aerospace field

A new limit of T-violating transverse muon polarization in the K+→π0μ+νK^{+}\to\pi^{0}\mu^{+} \nu decay

A search for T-violating transverse muon polarization ($P_T$) in the $K^{+}\to \pi^{0}\mu^{+}\nu$ decay was performed using kaon decays at rest. A new improved value, $P_T= -0.0017\pm 0.0023 (stat)\pm 0.0011 (syst)$, was obtained giving an upper limit, $| P_T | < 0.0050$. The T-violation parameter was determined to be Im$\xi = -0.0053 \pm 0.0071(stat)\pm 0.0036(syst)$ giving an upper limit, $|$Im$\xi| <0.016$.Comment: 5 pages, 4 figure