Mapping the Arnold web with a GPU-supercomputer

The Arnold diffusion constitutes a dynamical phenomenon which may occur in the phase space of a non-integrable Hamiltonian system whenever the number of the system degrees of freedom is $M \geq 3$. The diffusion is mediated by a web-like structure of resonance channels, which penetrates the phase space and allows the system to explore the whole energy shell. The Arnold diffusion is a slow process; consequently the mapping of the web presents a very time-consuming task. We demonstrate that the exploration of the Arnold web by use of a graphic processing unit (GPU)-supercomputer can result in distinct speedups of two orders of magnitude as compared to standard CPU-based simulations.Comment: 7 pages, 4 figures, a video supplementary provided at http://www.physik.uni-augsburg.de/~seiberar/arnold/Energy15_HD_frontNback.av

The fate of spiral galaxies in clusters: The star formation history of the anemic Virgo cluster galaxy NGC 4569

We present a new method for studying the star formation history of late-type cluster galaxies undergoing gas starvation or a ram pressure stripping event by combining bidimensional multifrequency observations with multizone models of galactic chemical and spectrophotometric evolution. This method is applied to the Virgo Cluster anemic galaxy NGC 4569. We extract radial profiles from recently obtained UV GALEX images at 1530 and 2310 Å, from visible and near-IR narrow (Hα) and broadband images at different wavelengths (u, B, g, V, r, i, z, J, H, and K), from Spitzer IRAC and MIPS images, and from atomic and molecular gas maps. The model in the absence of interaction (characterized by its rotation velocity and spin parameter) is constrained by the unperturbed H-band light profile and by the Hα rotation curve. We can reconstruct the observed total gas radial density profile and the light surface brightness profiles at all wavelengths in a ram pressure stripping scenario by making simple assumptions about the gas removal process and the orbit of NGC 4569 inside the cluster. The observed profiles cannot be reproduced by simply stopping gas infall, thus mimicking starvation. Gas removal is required, which is more efficient in the outer disk, inducing radial quenching in the star formation activity, as observed and reproduced by the model. This observational result, consistent with theoretical predictions that a galaxy cluster-IGM interaction is able to modify structural disk parameters without gravitational perturbations, is discussed in the framework of the origin of lenticular galaxies in cluster

Thermal quark production in ultra-relativistic nuclear collisions

We calculate thermal production of u, d, s, c and b quarks in ultra-relativistic heavy ion collisions. The following processes are taken into account: thermal gluon decay (g to ibar i), gluon fusion (g g to ibar i), and quark-antiquark annihilation (jbar j to ibar i), where i and j represent quark species. We use the thermal quark masses, $m_i^2(T)\simeq m_i^2 + (2g^2/9)T^2$, in all the rates. At small mass ($m_i(T)<2T$), the production is largely dominated by the thermal gluon decay channel. We obtain numerical and analytic solutions of one-dimensional hydrodynamic expansion of an initially pure glue plasma. Our results show that even in a quite optimistic scenario, all quarks are far from chemical equilibrium throughout the expansion. Thermal production of light quarks (u, d and s) is nearly independent of species. Heavy quark (c and b) production is quite independent of the transition temperature and could serve as a very good probe of the initial temperature. Thermal quark production measurements could also be used to determine the gluon damping rate, or equivalently the magnetic mass.Comment: 14 pages (latex) plus 6 figures (uuencoded postscript files); CERN-TH.7038/9

Novel Methodology for Measuring the Coefficient of Restitution from Various Types of Balls and Surfaces

Abstract The determination of the coefficient of restitution is of major interest in the design of balls and surfaces. Tennis courts are required to be resurfaced every five years. Players that slide on the court trust the surface to be uniform. Tennis court surfaces change as the ball fluff builds up, the heavily used playing areas are compacted more, the surface on clay is scuffed, and the sun and rain degrades the surface. Injuries can be caused by a player losing footing because of surface variability. With bouncing balls, the ball type and pressure are variable and depend on temperature and age. An investigation on the bounce of various balls (diameter less than 150 mm) from surfaces using an accelerometer on a novel, low cost, portable apparatus is presented. The mechanical structure holds both the moving ball and an inertial sensor. The quality and age of balls and the wear on playing surfaces is particularly important for reflex actions of elite athletes. Courts, pitches and other sports surfaces can be routinely quantified using sport specific balls and this simple, low cost method. Good agreement was observed between the coefficient of restitution using the portable device and a vertical drop test using a high speed camera. The error obtained using the portable device on various types of sports balls with the variation in CoR ≤ 0.01 which falls within the standards of the International Tennis Federation. There is a significant difference ( p = 0.0003) between a hardcourt tennis CoR and a synthetic grass tennis court

Synthetic Mudscapes: Human Interventions in Deltaic Land Building

In order to defend infrastructure, economy, and settlement in Southeast Louisiana, we must construct new land to mitigate increasing risk. Links between urban environments and economic drivers have constrained the dynamic delta landscape for generations, now threatening to undermine the ecological fitness of the entire region. Static methods of measuring, controlling, and valuing land fail in an environment that is constantly in flux; change and indeterminacy are denied by traditional inhabitation. Multiple land building practices reintroduce deltaic fluctuation and strategic deposition of fertile material to form the foundations of a multi-layered defence strategy. Manufactured marshlands reduce exposure to storm surge further inland. Virtual monitoring and communication networks inform design decisions and land use becomes determined by its ecological health. Mudscapes at the threshold of land and water place new value on former wastelands. The social, economic, and ecological evolution of the region are defended by an expanded web of growing land

Multitouch Experiment Instructions to Promote Self-Regulation in Inquiry-Based Learning in School Laboratories

Multitouch experiment instructions (MEIs), implemented as interactive eBooks, are learning tools for pupils that offer various digital support tools and enable pupils to individualize their learning. They may be applied to contexts such as inquiry-based experiments in school laboratories, which involve highly demanding cognitive processes and require a high level of self-regulation. Self-regulation has been shown to be reliably promoted by interventions which include the targeted training of self-regulation strategies. A MEI was designed as an interactive eBook on experiments on the topic “Analysis of Cola”, suitable for an inquiry-based learning environment such as a school lab. The MEI’s potential to promote self-regulated learning was investigated by comparing it to a MEI with digital, integrated self-regulation training. The data revealed a significant increase of self-regulation in the control group, which consisted of pupils experimenting with the MEI on its own, and one experimental group, which included pupils that were supported by the MEI with an additional self-regulation training. It can be assumed that the MEI’s ability to promote self-regulated learning is comparable to the results achieved by an additional self-regulation training which explicitly addressed self-regulation strategies. This highlights the MEI’s potential to promote self-regulated learning in an indirect approach

What's Decidable About Sequences?

We present a first-order theory of sequences with integer elements, Presburger arithmetic, and regular constraints, which can model significant properties of data structures such as arrays and lists. We give a decision procedure for the quantifier-free fragment, based on an encoding into the first-order theory of concatenation; the procedure has PSPACE complexity. The quantifier-free fragment of the theory of sequences can express properties such as sortedness and injectivity, as well as Boolean combinations of periodic and arithmetic facts relating the elements of the sequence and their positions (e.g., "for all even i's, the element at position i has value i+3 or 2i"). The resulting expressive power is orthogonal to that of the most expressive decidable logics for arrays. Some examples demonstrate that the fragment is also suitable to reason about sequence-manipulating programs within the standard framework of axiomatic semantics.Comment: Fixed a few lapses in the Mergesort exampl

Noncommutative Quantum Cosmology

We consider noncommutative quantum cosmology in the case of the low-energy string effective theory. Exacts solutions are found and compared with the commutative case.The Noncommutative quantum cosmology is considered in the case of the low-energy string effective theory. Exacts solutions are found and compared with the commutative case.Comment: Revtex4, 3 pages, 2 figures, to appear in Gen.Rel.Gra

Topological Reduction of 4D SYM to 2D σ\sigma--Models

By considering a (partial) topological twisting of supersymmetric Yang-Mills compactified on a 2d space with `t Hooft magnetic flux turned on we obtain a supersymmetric $\sigma$-model in 2 dimensions. For N=2 SYM this maps Donaldson observables on products of two Riemann surfaces to quantum cohomology ring of moduli space of flat connections on a Riemann surface. For N=4 SYM it maps $S$-duality to $T$-duality for $\sigma$-models on moduli space of solutions to Hitchin equations.Comment: 30 pages, harvma