Achieving Good Angular Resolution in 3D Arc Diagrams

We study a three-dimensional analogue to the well-known graph visualization approach known as arc diagrams. We provide several algorithms that achieve good angular resolution for 3D arc diagrams, even for cases when the arcs must project to a given 2D straight-line drawing of the input graph. Our methods make use of various graph coloring algorithms, including an algorithm for a new coloring problem, which we call localized edge coloring.Comment: 12 pages, 5 figures; to appear at the 21st International Symposium on Graph Drawing (GD 2013

La velocidad del sistema δ Librae

In order to resolve the problem of the difference in the system of δ Librae as found when comparing observations made at Allegheny and at Michigan, all the available material, including the Mount Wilson material secured a few years ago and analyzed by two of the authors (J. Sahade and A .Hernández), was measured with the Grant line spectrum comparator of the Department of Astronomy of the Indiana University. When the measurements were reduced (they were made on only one direction of the carriage) it was found that there were systematic differences between the velocities from diffuse and from sharp lines. The latter are in keeping with the velocities obtained with the conventional type of comparators. The preliminary analysis of the results that are consistent suggest that the announced difference in the system velocity at two epochs has no significance and resulted only from the original method of measurement and reduction.Asociación Argentina de Astronomí

La velocidad del sistema δ Librae

In order to resolve the problem of the difference in the system of δ Librae as found when comparing observations made at Allegheny and at Michigan, all the available material, including the Mount Wilson material secured a few years ago and analyzed by two of the authors (J. Sahade and A .Hernández), was measured with the Grant line spectrum comparator of the Department of Astronomy of the Indiana University. When the measurements were reduced (they were made on only one direction of the carriage) it was found that there were systematic differences between the velocities from diffuse and from sharp lines. The latter are in keeping with the velocities obtained with the conventional type of comparators. The preliminary analysis of the results that are consistent suggest that the announced difference in the system velocity at two epochs has no significance and resulted only from the original method of measurement and reduction.Asociación Argentina de Astronomí

La velocidad del sistema δ Librae

In order to resolve the problem of the difference in the system of δ Librae as found when comparing observations made at Allegheny and at Michigan, all the available material, including the Mount Wilson material secured a few years ago and analyzed by two of the authors (J. Sahade and A .Hernández), was measured with the Grant line spectrum comparator of the Department of Astronomy of the Indiana University. When the measurements were reduced (they were made on only one direction of the carriage) it was found that there were systematic differences between the velocities from diffuse and from sharp lines. The latter are in keeping with the velocities obtained with the conventional type of comparators. The preliminary analysis of the results that are consistent suggest that the announced difference in the system velocity at two epochs has no significance and resulted only from the original method of measurement and reduction.Asociación Argentina de Astronomí

Persistent currents in Moebius strips

Relation between the geometry of a two-dimensional sample and its equilibrium physical properties is exemplified here for a system of non-interacting electrons on a Moebius strip. Dispersion relation for a clean sample is derived and its persistent current under moderate disorder is elucidated, using statistical analysis pertinent to a single sample experiment. The flux periodicity is found to be distinct from that in a cylindrical sample, and the essential role of disorder in the ability to experimentally identify a Moebius strip is pointed out.Comment: 5 pages, 4 figure

Performance evaluation of novel square-bordered position-sensitive silicon detectors with four-corner readout

We report on a recently developed novel type of large area (62 mm x 62 mm) position sensitive silicon detector with four-corner readout. It consists of a square-shaped ion-implanted resistive anode framed by additional low-resistivity strips with resistances smaller than the anode surface resistance by a factor of 2. The detector position linearity, position resolution, and energy resolution were measured with alpha-particles and heavy ions. In-beam experimental results reveal a position resolution below 1 mm (FWHM) and a very good non-linearity of less than 1% (rms). The energy resolution determined from 228Th alpha source measurements is around 2% (FWHM).Comment: 13 pages, 10 figures, submitted to Nucl. Instr. and Meth.

Arithmetical properties of Multiple Ramanujan sums

In the present paper, we introduce a multiple Ramanujan sum for arithmetic functions, which gives a multivariable extension of the generalized Ramanujan sum studied by D. R. Anderson and T. M. Apostol. We then find fundamental arithmetic properties of the multiple Ramanujan sum and study several types of Dirichlet series involving the multiple Ramanujan sum. As an application, we evaluate higher-dimensional determinants of higher-dimensional matrices, the entries of which are given by values of the multiple Ramanujan sum.Comment: 19 page

Selection rules for J^PC Exotic Hybrid Meson Decay in Large-N_c

The coupling of a neutral hybrid {1,3,5...}^-+ exotic particle (or current) to two neutral (hybrid) meson particles with the same J^PC and J=0 is proved to be sub-leading to the usual large-N_c QCD counting. The coupling of the same exotic particle to certain two - (hybrid) meson currents with the same J^PC and J=0 is also sub-leading. The decay of a {1,3,5...}^-+ hybrid to eta pi^0, eta' pi^0, eta' eta, eta(1295) pi^0, pi(1300)^0 pi0, eta(1440) pi^0, a_0(980)^0 sigma or f_0(980) sigma is sub-leading, assuming that these final state particles are (hybrid) mesons in the limit of large N_c.Comment: 16 pages, LaTeX. Main paper shortened/rewritten and appendices expanded. Implications for phenomenology of exotic hybrid mesons clarifie

(Field) Symmetrization Selection Rules

QCD and QED exhibit an infinite set of three-point Green's functions that contain only OZI rule violating contributions, and (for QCD) are subleading in the large N_c expansion. The Green's functions describe the ``decay'' of a J^{PC}={1,3,5 ...}^{-+} exotic hybrid meson current to two J=0 (hybrid) meson currents with identical P and C. We prove that the QCD amplitude for a neutral hybrid {1,3,5 ...}^{-+} exotic current to create eta pi0 only comes from OZI rule violating contributions under certain conditions, and is subleading in N_c.Comment: 20 pages, LaTeX. Two postscript figures. Final published versio

How much time does a measurement take?

We consider the problem of measurement using the Lindblad equation, which allows the introduction of time in the interaction between the measured system and the measurement apparatus. We use analytic results, valid for weak system-environment coupling, obtained for a two-level system in contact with a measurer (Markovian interaction) and a thermal bath (non-Markovian interaction), where the measured observable may or may not commute with the system-environment interaction. Analysing the behavior of the coherence, which tends to a value asymptotically close to zero, we obtain an expression for the time of measurement which depends only on the system-measurer coupling, and which does not depend on whether the observable commutes with the system-bath interaction. The behavior of the coherences in the case of strong system-environment coupling, found numerically, indicates that an increase in this coupling decreases the measurement time, thus allowing our expression to be considered the upper limit for the duration of the process.Comment: REVISED VERSION: 17 pages, 2 figure