228,800 research outputs found
Nearly Conformal QCD and AdS/CFT
The AdS/CFT correspondence is a powerful tool to study the properties of
conformal QCD at strong coupling in terms of a higher dimensional dual gravity
theory. The power-law falloff of scattering amplitudes in the non-perturbative
regime and calculable hadron spectra follow from holographic models dual to QCD
with conformal behavior at short distances and confinement at large distances.
String modes and fluctuations about the AdS background are identified with QCD
degrees of freedom and orbital excitations at the AdS boundary limit. A
description of form factors in space and time-like regions and the behavior of
light-front wave functions can also be understood in terms of a dual gravity
description in the interior of AdS.Comment: 8 pages, LateX, 3 figures. Presented at First Workshop on
Quark-Hadron Duality and the Transition to pQCD, Frascati, Italy, 6-8 June
2005. AdS LFWF mapping reexamine
Assessment of a 3-D boundary layer code to predict heat transfer and flow losses in a turbine
Zonal concepts are utilized to delineate regions of application of three-dimensional boundary layer (DBL) theory. The zonal approach requires three distinct analyses. A modified version of the 3-DBL code named TABLET is used to analyze the boundary layer flow. This modified code solves the finite difference form of the compressible 3-DBL equations in a nonorthogonal surface coordinate system which includes coriolis forces produced by coordinate rotation. These equations are solved using an efficient, implicit, fully coupled finite difference procedure. The nonorthogonal surface coordinate system is calculated using a general analysis based on the transfinite mapping of Gordon which is valid for any arbitrary surface. Experimental data is used to determine the boundary layer edge conditions. The boundary layer edge conditions are determined by integrating the boundary layer edge equations, which are the Euler equations at the edge of the boundary layer, using the known experimental wall pressure distribution. Starting solutions along the inflow boundaries are estimated by solving the appropriate limiting form of the 3-DBL equations
Surface-tension-driven Stokes flow: a numerical method based on conformal geometry
AbstractA novel numerical scheme is presented for solving the problem of two dimensional Stokes flows with free boundaries whose evolution is driven by surface tension. The formulation is based on a complex variable formulation of Stokes flow and use of conformal mapping to track the free boundaries. The method is motivated by applications to modelling the fabrication process for microstructured optical fibres (MOFs), also known as “holey fibres”, and is therefore tailored for the computation of multiple interacting free boundaries. We give evidence of the efficacy of the method and discuss its performance
Non-classical Rotational Inertia in a Two-dimensional Bosonic Solid Containing Grain Boundaries
We study the occurrence of non-classical rotational inertia (NCRI) arising
from superfluidity along grain boundaries in a two-dimensional bosonic system.
We make use of a standard mapping between the zero-temperature properties of
this system and the statistical mechanics of interacting vortex lines in the
mixed phase of a type-II superconductor. In the mapping, the liquid phase of
the vortex system corresponds to the superfluid bosonic phase. We consider
numerically obtained polycrystalline configurations of the vortex lines in
which the microcrystals are separated by liquid-like grain boundary regions
which widen as the vortex system temperature increases. The NCRI of the
corresponding zero-temperature bosonic systems can then be numerically
evaluated by solving the equations of superfluid hydrodynamics in the channels
near the grain boundaries. We find that the NCRI increases very abruptly as the
liquid regions in the vortex system (equivalently, superfluid regions in the
bosonic system) form a connected, system-spannig structure with one or more
closed loops. The implications of these results for experimentally observed
supersolid phenomena are discussed.Comment: Ten pages, including figure
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