A lattice refinement scheme for finding periodic orbits

A lattice refinement scheme based on the principle of linearized stability is introduced to locate periodic orbits in a two-dimensional map. The method locates all periodic orbits of a specified order within a given starting window and it can be equally well applied when the map is only known implicitly, e.g., as a two-dimensional surface of section arising from a three-dimensional flow. Periodic orbits in the Henon Map, the Predator-Prey Map, the Rossler Flow, and the Lorenz Flow are constructed as illustrations of the method

High conservation of the dental plaque microbiome community across populations with differing subsistence strategies and levels of market integration

Industrialization—including urbanization, participation in the global food chain and consumption of heavily processed foods—is thought to drive substantial shifts in the human microbiome. While diet strongly influences stool microbiome composition, the influence of diet on the oral microbiome is largely speculative. Multiple ecologically distinct surfaces in the mouth, each harbouring a unique microbial community, pose a challenge to assessing changes in the oral microbiome in the context of industrialization, as the results depend on the oral site under study. Here, we investigated whether microbial communities of dental plaque, the dense biofilm on non-shedding tooth surfaces, are distinctly different across populations with dissimilar subsistence strategies and degree of industrialized market integration. Using a metagenomic approach, we compared the dental plaque microbiomes of Baka foragers and Nzime subsistence agriculturalists in Cameroon (n = 46) with the dental plaque and calculus microbiomes of highly industrialized populations in North America and Europe (n = 38). We found that differences in microbial taxonomic composition between populations were minimal, with high conservation of abundant microbial taxa and no significant differences in microbial diversity related to dietary practices. Instead, we find that the major source of variation in dental plaque microbial species composition is related to tooth location and oxygen availability, which may be influenced by toothbrushing or other dental hygiene measures. Our results support that dental plaque, in contrast to the stool microbiome, maintains an inherent stability against ecological perturbations in the oral environment.ERC-STG 677576Bioarchaeolog

Spectral flow and boundary string field theory for angled D-branes

D-branes intersecting at an arbitrary fixed angle generically constitute a configuration unstable toward recombination. The reconnection of the branes nucleates at the intersection point and involves a generalization of the process of brane decay of interest to non-perturbative string dynamics as well as cosmology. After reviewing the string spectrum of systems of angled branes, we show that worldsheet twist superfields may be used in the context of Boundary Superstring Field Theory to describe the dynamics. Changing the angle between the branes is seen from the worldsheet as spectral flow with boundary insertions flowing from bosonic to fermionic operators. We calculate the complete tachyon potential and the low energy effective action as a function of angle and find an expression that interpolates between the brane-antibrane and the Dirac-Born-Infeld actions. The potential captures the mechanism of D-brane recombination and provides for interesting new physics for tachyon decay.Comment: 32 pages, 9 figures; v2 references added; v3 discussion clarifie

An Improved Brane Anti-Brane Action from Boundary Superstring Field Theory and Multi-Vortex Solutions

We present an improved effective action for the D-brane-anti-D-brane system obtained from boundary superstring field theory. Although the action looks highly non-trivial, it has simple explicit multi-vortex (i.e. codimension-2 multi-BPS D-brane) multi-anti-vortex solutions. The solutions have a curious degeneracy corresponding to different ``magnetic'' fluxes at the core of each vortex. We also generalize the brane anti-brane effective action that is suitable for the study of the inflationary scenario and the production of defects in the early universe. We show that when a brane and anti-brane are distantly separated, although the system is classically stable it can decay via quantum tunneling through the barrier.Comment: 24 pages, 1 figure, JHEP3.cls; v2: references added, tunneling rate discussion expande

Review on the EFDA work programme on nano-structured ODS RAF steels

This proceeding is: The 14th International Conference on Fusion Reactor Materials (ICFRM-14) was held at the Sapporo Convention Center in Sapporo, Japan from 7 to 12 September 2009.The 2008─2009 work programme of the European research project on nano-structured oxide dispersion strengthened (ODS) reduced activation ferritic (RAF) steels is being organized along the four following programmatic lines: (1) improve the present generation of nano-structured ODS RAF steels; (2) start the industrial fabrication of the present generation of nano-structured ODS RAF steels; (3) develop an optimised generation of nano-structured and nano-grained ODS RAF steels; (4) investigate the stability of present and optimised generation of nano-structured ODS RAF steels under creep and irradiation. This paper presents the main objectives of current R&D activities being performed within the European research project on nano-structured ODS RAF steels, the main obtained results and the main future activities in the case of the four programmatic lines mentioned just above.This work, supported by the European Communities, was carried out within the framework of the European Fusion Development Agreement.Publicad

Is cosmology consistent?

We perform a detailed analysis of the latest CMB measurements (including BOOMERaNG, DASI, Maxima and CBI), both alone and jointly with other cosmological data sets involving, e.g., galaxy clustering and the Lyman Alpha Forest. We first address the question of whether the CMB data are internally consistent once calibration and beam uncertainties are taken into account, performing a series of statistical tests. With a few minor caveats, our answer is yes, and we compress all data into a single set of 24 bandpowers with associated covariance matrix and window functions. We then compute joint constraints on the 11 parameters of the ``standard'' adiabatic inflationary cosmological model. Out best fit model passes a series of physical consistency checks and agrees with essentially all currently available cosmological data. In addition to sharp constraints on the cosmic matter budget in good agreement with those of the BOOMERaNG, DASI and Maxima teams, we obtain a heaviest neutrino mass range 0.04-4.2 eV and the sharpest constraints to date on gravity waves which (together with preference for a slight red-tilt) favors ``small-field'' inflation models.Comment: Replaced to match accepted PRD version. 14 pages, 12 figs. Tiny changes due to smaller DASI & Maxima calibration errors. Expanded neutrino and tensor discussion, added refs, typos fixed. Combined CMB data, window and covariance matrix at http://www.hep.upenn.edu/~max/consistent.html or from [email protected]

Azimuthal anisotropy and correlations in p+p, d+Au and Au+Au collisions at 200 GeV

We present the first measurement of directed flow ($v_1$) at RHIC. $v_1$ is found to be consistent with zero at pseudorapidities $\eta$ from -1.2 to 1.2, then rises to the level of a couple of percent over the range $2.4 < |\eta| < 4$. The latter observation is similar to data from NA49 if the SPS rapidities are shifted by the difference in beam rapidity between RHIC and SPS. Back-to-back jets emitted out-of-plane are found to be suppressed more if compared to those emitted in-plane, which is consistent with {\it jet quenching}. Using the scalar product method, we systematically compared azimuthal correlations from p+p, d+Au and Au+Au collisions. Flow and non-flow from these three different collision systems are discussed.Comment: Quark Matter 2004 proceeding, 4 pages, 3 figure

Azimuthal anisotropy: the higher harmonics

We report the first observations of the fourth harmonic (v_4) in the azimuthal distribution of particles at RHIC. The measurement was done taking advantage of the large elliptic flow generated at RHIC. The integrated v_4 is about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8) harmonics upper limits on the magnitudes are reported.Comment: 4 pages, 6 figures, contribution to the Quark Matter 2004 proceeding