More on supersymmetric tensionless rotating strings in AdS_5 x S^5

Rotating IIB strings in AdS_5 x S^5 become ultra-relativistic, and hence effectively tensionless, in the limit of large angular momentum on S^5. We have shown previously that such tensionless strings may preserve supersymmetry. Here we extend this result to include a class of supersymmetric tensionless strings with arbitrary SO(6) angular momentum. We close with some general comments on tensionless strings in AdS_5 x S^5.Comment: Contribution to the 3rd International Symposium on Quantum Theory and Symmetries (QTS3), Cincinnati, 10-14 Sep 200

A review of name-based ethnicity classification methods and their potential in population studies

Several approaches have been proposed to classify populations into ethnic groups using people's names, as an alternative to ethnicity self-identification information when this is not available. These methodologies have been developed, primarily in the public health and population genetics literature in different countries, in isolation from and with little participation from demographers or social scientists. The objective of this paper is to bring together these isolated efforts and provide a coherent comparison, a common methodology and terminology in order to foster new research and applications in this promising and multidisciplinary field. A systematic review has been conducted of the most representative studies that develop new name-based ethnicity classifications, extracting methodological commonalities, achievements and shortcomings; 13 studies met the inclusion criteria and all followed a very similar methodology to create a name reference list with which to classify populations into a few most common ethnic groups. The different classifications' sensitivity varies between 0.67 and 0.95, their specificity between 0.80 and 1, their positive predicted value between 0.70 and 0.96, and their negative predicted value between 0.96 and 1. Name-based ethnicity classification systems have a great potential to overcome data scarcity issues in a wide variety of key topics in population studies, as is proved by the 13 papers analysed. Their current limitations are mainly due to a restricted number of names and a partial spatio-temporal coverage of the reference population data-sets used to produce name reference lists. Improved classifications with extensive population coverage and higher classification accuracy levels will be achieved by using population registers with wider spatio-temporal coverage. Furthermore, there is a requirement for such new classifications to include all of the potential ethnic groups present in a society, and not just one or a few of them. Copyright (c) 2007 John Wiley & Sons, Ltd

Chaotic Transport and Current Reversal in Deterministic Ratchets

We address the problem of the classical deterministic dynamics of a particle in a periodic asymmetric potential of the ratchet type. We take into account the inertial term in order to understand the role of the chaotic dynamics in the transport properties. By a comparison between the bifurcation diagram and the current, we identify the origin of the current reversal as a bifurcation from a chaotic to a periodic regime. Close to this bifurcation, we observed trajectories revealing intermittent chaos and anomalous deterministic diffusion.Comment: (7 figures) To appear in Physical Review Letters (in January 2000

Supertubes and special holonomy

We obtain a $\frac 14$-supersymmetric 6-brane solution of IIA Supergravity by T-dualizing the supertube recently found. The resulting $C_{\it 1}$ electric charge is related to the original $D0$-brane charge. The uplifted solution to eleven dimensions results to be a purely geometrical configuration, which can be interpreted as a bound state of a Taub-NUT space and a pp-wave. Being the non trivial part of the metric pseudo-Riemannian, the resulting reduced holonomy group is non-compact and locally isomorphic to a semidirect product of an Abelian four dimensional group and SU(2).Comment: 11 pages, latex, no figure

Supertubes and Supercurves from M-Ribbons

We construct 1/4 BPS configurations, `M-ribbons', in M-theory on T^2, which give the supertubes and supercurves in type IIA theory upon dimensional reduction. These M-ribbons are generalized so as to be consistent with the SL(2,Z) modular transformation on T^2. In terms of the type IIB theory, the generalized M-ribbons are interpreted as an SL(2,Z) duality family of super D-helix. It is also shown that the BPS M-ribbons must be straight in one direction.Comment: 10 pages, 1 figure, references added, footnote added, BPS eq. (36) is examined without using the solution of field equations, some expressions are improve

Dynamical Sieve of Eratosthenes

In this document, prime numbers are related as functions over time, mimicking the Sieve of Eratosthenes. For this purpose, the mathematical representation is a uni-dimentional time line depicting the number line for positive natural numbers N, where each number n represents a time t. In the same way as the Eratosthenes' sieve, which iteratively mark as composite the multiples of each prime, starting at each prime. This dynamical prime number function P(s) zero-cross all composite numbers departing from primes, following a linear progression over time.Comment: 9 page

Forenames and Surnames in Spain in 2004

This paper quantifies the corpus of forenames and surnames in Spain in 2004 using the telephone directory. It describes their frequency patterns, major measurable characteristics, and gives some geographical distributions, international comparisons, and historical explanations. The research presented here is set in a context of a broader study of the quantitative properties of the corpus of personal names in several countries undertaken by Tucker. Amongst the most significant findings are a much more highly skewed distribution towards the most popular surnames than in other countries, the permanence of language regions since the Middle Ages, and important differences in top Hispanic names frequencies between five countries across the Atlantic. It is also suggested that the innovative techniques presented here, combining geographical and statistical analysis of names and their language of origin, opens up enormous possibilities for multidisciplinary work on onomastics

Bright branes for strongly coupled plasmas

We use holographic techniques to study photon production in a class of finite temperature, strongly coupled, large-Nc SU(Nc) quark-gluon plasmas with Nf << Nc quark flavours. Our results are valid to leading order in the electromagnetic coupling constant but non-perturbatively in the SU(Nc) interactions. The spectral function of electromagnetic currents and other related observables exhibit an interesting structure as a function of the photon frequency and the quark mass. We discuss possible implications for heavy ion collision experiments.Comment: 29 pages, 14 figure