Bibliometric Indicators of Young Authors in Astrophysics: Can Later Stars be Predicted?

We test 16 bibliometric indicators with respect to their validity at the level of the individual researcher by estimating their power to predict later successful researchers. We compare the indicators of a sample of astrophysics researchers who later co-authored highly cited papers before their first landmark paper with the distributions of these indicators over a random control group of young authors in astronomy and astrophysics. We find that field and citation-window normalisation substantially improves the predicting power of citation indicators. The two indicators of total influence based on citation numbers normalised with expected citation numbers are the only indicators which show differences between later stars and random authors significant on a 1% level. Indicators of paper output are not very useful to predict later stars. The famous $h$-index makes no difference at all between later stars and the random control group.Comment: 14 pages, 10 figure

Fractional Collections with Cardinality Bounds, and Mixed Integer Linear Arithmetic with Stars

We present decision procedures for logical constraints that support reasoning about collections of elements such as sets, multisets, and fuzzy sets. Element membership in such collections is given by a characteristic function from a finite universe (of unknown size) to a subset of rational numbers specified by user-defined constraints in mixed linear integer-rational arithmetic. Our logic supports standard operators such as union, intersection, difference, or any operation defined pointwise using mixed linear integer-rational arithmetic. Moreover, it supports the notion of cardinality of the collection. Deciding formulas in such logic has application in verification of data structures. Our decision procedure reduces satisfiability of formulas with collections to satisfiability of formulas in an extension of mixed linear integer-rational arithmetic with an “unbounded sum” operator. Such extension is also interesting in its own right because it can encode reachability problems for a simple class of transition systems. We present a decision procedure for the resulting extension, using a satisfiability-preserving transformation that eliminates the unbounded sum operator. Our decidability result subsumes previous special cases for sets and multisets

Monte Carlo simulations of infinitely dilute solutions of amphiphilic diblock star copolymers

Single-chain Monte Carlo simulations of amphiphilic diblock star copolymers were carried out in continuous space using implicit solvents. Two distinct architectures were studied: stars with the hydrophobic blocks attached to the core, and stars with the polar blocks attached to the core, with all arms being of equal length. The ratio of the lengths of the hydrophobic block to the length of the polar block was varied from 0 to 1. Stars with 3, 6, 9 or 12 arms, each of length 10, 15, 25, 50, 75 and 100 Kuhn segments were analysed. Four distinct types of conformations were observed for these systems. These, apart from studying the snapshots from the simulations, have been quantitatively characterised in terms of the mean-squared radii of gyration, mean-squared distances of monomers from the centre-of-mass, asphericity indices, static scattering form factors in the Kratky representation as well as the intra-chain monomer-monomer radial distribution functions.Comment: 12 pages, 11 ps figures. Accepted for publication in J. Chem. Phy

Spectral resolution in hyperbolic orbifolds, quantum chaos, and cosmology

We present a few subjects from physics that have one in common: the spectral resolution of the Laplacian.Comment: 24 pages. Contribution to the TSL Expository Lecture Series V "Computational Physical Sciences 2006", Universiti Putra Malaysi