Numerical study on run-up heights of solitary wave with hydrodynamic pressure model

For many shallow water flows, it is sufficient to consider the depth-averaged equations, referred as the shallow water equations, which are two-dimensional in the horizontal plane, since the length scale of the vertical direction is much smaller than that of the horizontal directions. Assuming that the pressure distribution is hydrostatic, the mathematical formulation and its numerical implementation are considerably simplified. In this study, a numerical model is newly developed to investigate various free surface fl ow problems. The governing equations are the Navier???Stokes equations with the pressure decomposed into the sum of a hydrostatic and a hydrodynamic components. The equation for the free surface movement is a depth???averaged continuity equation which is a free surface equation. These governing equations are simultaneously solved by using a finite difference method with a semi???implicit method and fractional step method. At the first step, the vertical momentum equations are discretized by using an implicit method over the vertical direction. In the second step, the discrete horizontal momentum equations are projected on to the free surface equation. Finally, the hydrodynamic pressure and final velocity field are calculated. To verify the accuracy and stability, the present numerical model is applied to move practical problems such as the run???up process of solitary waves attacking a circular island. The numerically obtained maximum run???up heights around a circular island are compared with available laboratory measurements. A very reasonable agreement is observed

Metallicities of galaxies in the nearby Lynx-Cancer void

Does the void environment have a sizable effect on the evolution of dwarf galaxies? If yes, the best probes should be the most fragile least massive dwarfs. We compiled a sample of about one hundred dwarfs with M_B in the range -12 to -18 mag, falling within the nearby Lynx-Cancer void. The goal is to study their evolutionary parameters -- gas metallicity and gas mass-fraction, and to address the epoch of the first substantial episode of Star Formation. Here we present and discuss the results of O/H measurements in 38 void galaxies, among which several the most metal-poor galaxies are found with the oxygen abundances of 12+log(O/H)=7.12-7.3 dex.Comment: 2 pages, one figure. To appear in proceedings of 'Environment and the Formation of Galaxies: 30 years later,' (Lisbon, September 2010), published by Springer-Verla

Thomson and Compton scattering with an intense laser pulse

Our paper concerns the scattering of intense laser radiation on free electrons and it is focused on the relation between nonlinear Compton and nonlinear Thomson scattering. The analysis is performed for a laser field modeled by an ideal pulse with a finite duration, a fixed direction of propagation and indefinitely extended in the plane perpendicular to it. We derive the classical limit of the quantum spectral and angular distribution of the emitted radiation, for an arbitrary polarization of the laser pulse. We also rederive our result directly, in the framework of classical electrodynamics, obtaining, at the same time, the distribution for the emitted radiation with a well defined polarization. The results reduce to those established by Krafft et al. [Phys. Rev. E 72, 056502 (2005)] in the particular case of linear polarization of the pulse, orthogonal to the initial electron momentum. Conditions in which the differences between classical and quantum results are visible are discussed and illustrated by graphs

Thermally activated flux flow in superconducting epitaxial FeSe0.6Te0.4 thin film

AbstractThe thermally activated flux flow effect has been studied in epitaxial FeSe0.6Te0.4 thin film grown by a PLD method through the electrical resistivity measurement under various magnetic fields for B//c and B//ab. The results showed that the thermally activated flux flow effect is well described by the nonlinear temperature-dependent activation energy. The evaluated apparent activation energy U0(B) is one order larger than the reported results and showed the double-linearity in both magnetic field directions. Furthermore, the FeSe0.6Te0.4 thin film shows the anisotropy of 5.6 near Tc and 2D-like superconducting behavior in thermally activated flux flow region. In addition, the vortex glass transition and the temperature dependence of the high critical fields were determined

The Abelian/Nonabelian Correspondence and Frobenius Manifolds

We propose an approach via Frobenius manifolds to the study (began in math.AG/0407254) of the relation between rational Gromov-Witten invariants of nonabelian quotients X//G and those of the corresponding ``abelianized'' quotients X//T, for T a maximal torus in G. The ensuing conjecture expresses the Gromov-Witten potential of X//G in terms of the potential of X//T. We prove this conjecture when the nonabelian quotients are partial flag manifolds.Comment: 35 pages, no figure

The antiferromagnetic phi4 Model, II. The one-loop renormalization

It is shown that the four dimensional antiferromagnetic lattice phi4 model has the usual non-asymptotically free scaling law in the UV regime around the chiral symmetrical critical point. The theory describes a scalar and a pseudoscalar particle. A continuum effective theory is derived for low energies. A possibility of constructing a model with a single chiral boson is mentioned.Comment: To appear in Phys. Rev.

Search for Small Trans-Neptunian Objects by the TAOS Project

The Taiwan-America Occultation Survey (TAOS) aims to determine the number of small icy bodies in the outer reach of the Solar System by means of stellar occultation. An array of 4 robotic small (D=0.5 m), wide-field (f/1.9) telescopes have been installed at Lulin Observatory in Taiwan to simultaneously monitor some thousand of stars for such rare occultation events. Because a typical occultation event by a TNO a few km across will last for only a fraction of a second, fast photometry is necessary. A special CCD readout scheme has been devised to allow for stellar photometry taken a few times per second. Effective analysis pipelines have been developed to process stellar light curves and to correlate any possible flux changes among all telescopes. A few billion photometric measurements have been collected since the routine survey began in early 2005. Our preliminary result of a very low detection rate suggests a deficit of small TNOs down to a few km size, consistent with the extrapolation of some recent studies of larger (30--100 km) TNOs.Comment: 4 pages, 3 figures, IAU Symposium 23

Time-frequency detection algorithm for gravitational wave bursts

An efficient algorithm is presented for the identification of short bursts of gravitational radiation in the data from broad-band interferometric detectors. The algorithm consists of three steps: pixels of the time-frequency representation of the data that have power above a fixed threshold are first identified. Clusters of such pixels that conform to a set of rules on their size and their proximity to other clusters are formed, and a final threshold is applied on the power integrated over all pixels in such clusters. Formal arguments are given to support the conjecture that this algorithm is very efficient for a wide class of signals. A precise model for the false alarm rate of this algorithm is presented, and it is shown using a number of representative numerical simulations to be accurate at the 1% level for most values of the parameters, with maximal error around 10%.Comment: 26 pages, 15 figures, to appear in PR

Off-Shell Interactions for Closed-String Tachyons

Off-shell interactions for localized closed-string tachyons in C/Z_N superstring backgrounds are analyzed and a conjecture for the effective height of the tachyon potential is elaborated. At large N, some of the relevant tachyons are nearly massless and their interactions can be deduced from the S-matrix. The cubic interactions between these tachyons and the massless fields are computed in a closed form using orbifold CFT techniques. The cubic interaction between nearly-massless tachyons with different charges is shown to vanish and thus condensation of one tachyon does not source the others. It is shown that to leading order in N, the quartic contact interaction vanishes and the massless exchanges completely account for the four point scattering amplitude. This indicates that it is necessary to go beyond quartic interactions or to include other fields to test the conjecture for the height of the tachyon potential.Comment: 37 pages, 3 figures, LaTeX, JHEP class. Typos corrected, references added, published versio

Oscillations of a solid sphere falling through a wormlike micellar fluid

We present an experimental study of the motion of a solid sphere falling through a wormlike micellar fluid. While smaller or lighter spheres quickly reach a terminal velocity, larger or heavier spheres are found to oscillate in the direction of their falling motion. The onset of this instability correlates with a critical value of the velocity gradient scale $\Gamma_{c}\sim 1$ s$^{-1}$. We relate this condition to the known complex rheology of wormlike micellar fluids, and suggest that the unsteady motion of the sphere is caused by the formation and breaking of flow-induced structures.Comment: 4 pages, 4 figure