5,462 research outputs found

    Inclusion of Yang-Mills Fields in String Corrected Supergravity

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    We consistently incorporate Yang Mills matter fields into string corrected (deformed), D=10, N=1 Supergravity. We solve the Bianchi identities within the framework of the modified beta function favored constraints to second order in the string slope parameter \g also including the Yang Mills fields. In the torsion, curvature and H sectors we find that a consistent solution is readily obtained with a Yang Mills modified supercurrent AabcA_{abc}. We find a solution in the F sector following our previously developed method.Comment: 11 pages, LaTeX file, PACS number: 04.65.+

    Structure and stability of the compressible Stuart vortex

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    The structure and two- and three-dimensional stability properties of a linear array of compressible Stuart vortices (CSV; Stuart 1967; Meiron et al. 2000) are investigated both analytically and numerically. The CSV is a family of steady, homentropic, two-dimensional solutions to the compressible Euler equations, parameterized by the free-stream Mach number M_∞, and the mass flux _ inside a single vortex core. Known solutions have 0 < M_∞ < 1. To investigate the normal-mode stability of the generally spatially non-uniform CSV solutions, the linear partial-differential equations describing the time evolution of small perturbations to the CSV base state are solved numerically using a normal-mode analysis in conjunction with a spectral method. The effect of increasing M_∞ on the two main classes of instabilities found by Pierrehumbert & Widnall (1982) for the incompressible limit M_∞ → 0 is studied. It is found that both two- and three-dimensional subharmonic instabilities cease to promote pairing events even at moderate M_∞. The fundamental mode becomes dominant at higher Mach numbers, although it ceases to peak strongly at a single spanwise wavenumber. We also find, over the range of ε investigated, a new instability corresponding to an instability on a parallel shear layer. The significance of these instabilities to experimental observations of growth in the compressible mixing layer is discussed. In an Appendix, we study the CSV equations when ε is small and M_∞ is finite using a perturbation expansion in powers of ε. An eigenvalue determining the structure of the perturbed vorticity and density fields is obtained from a singular Sturm–Liouville problem for the stream-function perturbation at O(ε). The resulting small-amplitude steady CSV solutions are shown to represent a bifurcation from the neutral point in the stability of a parallel shear layer with a tanh-velocity profile in a compressible inviscid perfect gas at uniform temperature

    Smooth transonic flow in an array of counter-rotating vortices

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    Numerical solutions to the steady two-dimensional compressible Euler equations corresponding to a compressible analogue of the Mallier & Maslowe (Phys. Fluids, vol. A 5, 1993, p. 1074) vortex are presented. The steady compressible Euler equations are derived for homentropic flow and solved using a spectral method. A solution branch is parameterized by the inverse of the sound speed at infinity, c1c_{\infty}^{-1}, and the mass flow rate between adjacent vortex cores of the corresponding incompressible solution, ϵ\epsilon. For certain values of the mass flux, the solution branches followed numerically were found to terminate at a finite value of c1c_{\infty}^{-1}. Along these branches numerical evidence for the existence of extensive regions of smooth steady transonic flow, with local Mach numbers as large as 1.276, is presented
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