International Conference on Shallow-Water Acoustics

The conference was jointly organized by the Institute of Acoustics (CAS), Georgia Institute of Technology and Naval Postgraduate School.Shallow water acoustics is currently a topic of great interest world-wide. Strong boundary interaction, multipath propagation and a complex and variable environment make it an extremely challenging field. An international conference could offer the first comprehensive environment in which shallow-water acoustics experts from many nations can exchange information and discuss subjects of common interest.ONR Ocean Acoustics ProgramChinese Academy of SciencesNatural Science Foundation of ChinaChina State Shipbuilding CorporationApproved for public release; distribution unlimite

Intersecting non-SUSY pp-brane with chargeless 0-brane as black pp-brane

Unlike BPS $p$-brane, non-supersymmetric (non-susy) $p$-brane could be either charged or chargeless. As envisaged in [hep-th/0503007], we construct an intersecting non-susy $p$-brane with chargeless non-susy $q$-brane by taking T-dualities along the delocalized directions of the non-susy $q$-brane solution delocalized in $(p-q)$ transverse directions (where $p\geq q$). In general these solutions are characterized by four independent parameters. We show that when $q=0$ the intersecting charged as well as chargeless non-susy $p$-brane with chargeless 0-brane can be mapped by a coordinate transformation to black $p$-brane when two of the four parameters characterizing the solution take some special values. For definiteness we restrict our discussion to space-time dimensions $d=10$. We observe that parameters characterizing the black brane and the related dynamics are in general in a different branch of the parameter space from those describing the brane-antibrane annihilation process. We demonstrate this in the two examples, namely, the non-susy D0-brane and the intersecting non-susy D4 and D0-branes, where the solutions with the explicit microscopic descriptions are known.Comment: 25 page

Analysis of Vibration Eigenfrequencies of a Thin Plate by the Keller-Rubinow Wave Method .1. Clamped Boundary-Conditions with Rectangular or Circular Geometry

The wave method of Keller and Rubinow [Ann. Physics, 9 (1960), p. 24-75] is extended to the biharmonic eigenvalue problem with rectangular or circular geometry and clamped boundary conditions. First, it is noted from the clues of computer graphics that mode shapes of a clamped circular plate and those of a circular membrane look very similar to each other. This suggests that plate and membrane should have very similar vibration behavior and leads to the assumption that the covering space of a rectangular plate is still a torus. By adding several waves on the boundary, approximate eigenfrequency equations are derived. Their solutions are shown to agree remarkably with numerical solutions obtained by the Legendre-tau spectral method here and by the finite-element method elsewhere at all frequency ranges. The same idea is also applied to the circular plate and yields excellent agreement between the exact values of eigenfrequencies and the asymptotic solutions

On the Existence of Equilibrium for Abstract Economies

AbstractIn this paper, several existence theorems for abstract economies have been established, They are natural modifications (strict generalizations when strategy spaces are metrizable) of the main results of Yannelis and Prabhakar [23], Tulcea [22], and Ding, Kim, and Tan [10] for infinite-dimensional casas. For the finite-dimensional case, we show that the topological conditions on correspondences in Shafer and Sonnenschein′s result [20] can be much weaker. Along the proofs, several propositions are established, which are of independent interest. We also show that many existence results in fixed point theory, maximization theory, and generalized quasi-variational inequalities can be encompassed

Fundamental strings and NS5-branes from unstable D-branes in supergravity

By using the non-supersymmetric $p$-brane solutions delocalized in arbitrary number of transverse directions in type II supergravities, we show how they can be regarded as interpolating solutions between unstable D$p$-branes (a non-BPS D-brane or a pair of coincident D-brane-antiD-brane) and fundamental strings and also between unstable D$p$-branes and NS5-branes. We also show that some of these solutions can be regarded as interpolating solutions between NS5/$\bar{\rm NS}$5 and D$p$-branes (for $p \leq 5$). This gives a closed string description of the tachyon condensation and lends support to the conjecture that the open string theory on unstable D-branes at the tachyonic vacuum has soliton solutions describing not only the lower dimensional BPS D-branes, but also the fundamental strings as well as the NS5-branes.Comment: 11 pages, LaTeX, one statement corrected and one reference added, v3: more details of the solution used is given, version to appear in Phys. Lett.

Probing the superconducting pairing symmetry from spin excitations in BiS2_2 based superconductors

Starting from a two-orbital model and based on the random phase approximation, spin excitations in the superconducting state of the newly discovered BiS$_2$ superconductors with three possible pairing symmetries are studied theoretically. We show that spin response is uniquely determined by the pairing symmetry. Possible spin resonance excitations might occur for the d-wave symmetry at an incommensurate momentum about $(0.7\pi,0.7\pi)$. For the p-wave symmetry the transverse spin excitation near $(0,0)$ is enhanced. For the s-wave pairing symmetry there is no spin resonance signature. These distinct features may be used for probing or determining the pairing symmetry in this newly discovered compound.Comment: 4 pages, 5 figure

Delocalized, non-SUSY pp-branes, tachyon condensation and tachyon matter

We construct non-supersymmetric $p$-brane solutions of type II supergravities in arbitrary dimensions ($d$) delocalized in one of the spatial transverse directions. By a Wick rotation we convert these solutions into Euclidean $p$-branes delocalized in the transverse time-like direction. The former solutions in $d=10$ nicely interpolate between the $(p+1)$-dimensional non-BPS D-branes and the $p$-dimensional BPS D-branes very similar to the picture of tachyon condensation for the tachyonic kink solution on the non-BPS D-branes. On the other hand the latter solutions interpolate between the $(p+1)$-dimensional non-BPS D-branes and the tachyon matter supergravity configuration very similar to the picture of rolling tachyon on the non-BPS D-branes.Comment: 15 pages, typos correcte

Non-SUSY pp-branes, bubbles and tubular branes

We consider non-supersymmetric $p$-brane solutions of type II string theories characterized by three parameters. When the charge parameter vanishes and one of the other two takes a specific value, the corresponding chargeless solutions can be regular and describe ``bubbles'' in static (unstable) equilibrium when lifted to $d = 11$. In appropriate coordinates, they represent D6 branes with a tubular topology R$^{1,p}$ $\times$ S$^{6-p}$ when reduced to $d=10$, called the tubular D6 branes, held in static equilibrium by a fixed magnetic flux (fluxbrane). Moreover, a `rotation parameter' can be introduced to either of the above two eleven dimensional configurations, giving rise to a generalized configuration labelling by the parameter. As such, it brings out the relations among non-supersymmetric $p$-branes, bubbles and tubular D6 branes. Given our understanding on tubular D6 branes, we are able to reinforce the interpretation of the chargeless non-supersymmetric $p$-branes as representing $p$-brane-anti$p$-brane (or non-BPS $p$-brane) systems, and understand the static nature and various singularities of these systems in a classical supergravity approximation.Comment: 18 pages, footnote 7 removed due to some erro

Static, non-SUSY pp-branes in diverse dimensions

We give explicit constructions of static, non-supersymmetric $p$-brane (for $p \leq d-4$, where $d$ is the space-time dimensionality and including $p=-1$ or D-instanton) solutions of type II supergravities in diverse dimensions. A subclass of these are the static counterpart of the time dependent solutions obtained in [hep-th/0309202]. Depending on the forms of the non-extremality function $G(r)$ defined in the text, we discuss various possible solutions and their region of validity. We show how one class of these solutions interpolate between the $p$-brane--anti $p$-brane solutions and the usual BPS $p$-brane solutions in $d=10$, while the other class, although have BPS limits, do not have such an interpretation. We point out how the time dependent solutions mentioned above can be obtained by a Wick rotation of one class of these static solutions. We also discuss another type of solutions which might seem non-supersymmetric, but we show by a coordinate transformation that they are nothing but the near horizon limits of the various BPS $p$-branes already known.Comment: 29 pages, typos corrected, references adde

Supergravity Solutions for Harmonic, Static and Flux S-Branes

We seek S-brane solutions in D=11 supergravity which can be characterized by a harmonic function H on the flat transverse space. It turns out that the Einstein's equations force H to be a linear function of the transverse coordinates. The codimension one H=0 hyperplane can be spacelike, timelike or null and the spacelike case reduces to the previously obtained SM2 or SM5 brane solutions. We then consider static S-brane configurations having smeared timelike directions where the transverse Lorentzian symmetry group is broken down to its maximal orthogonal subgroup. Assuming that the metric functions depend on a radial spatial coordinate, we construct explicit solutions in D=11 supergravity which are non-supersymmetric and asymptotically flat. Finally, we obtain spacelike fluxbrane backgrounds which have timelike electric or magnetic fluxlines extending from past to future infinity.Comment: 22 pages, v2: references adde