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Warped HI gas layers in the outer regions of spiral galaxies usually display a noticeably twisted structure. This structure is thought to arise primarily as a result of differential precession in the HI disk as it settles toward a "preferred orientation" in an underlying dark halo potential well that is not spherically symmetric. In an attempt to better understand the structure and evolution of these twisted, warped disk structures, we have utilized the "twist-equation" formalism originally developed by Petterson (1977, ApJ, 214, 550). Specifically, we have generalized the twist equation presented by Papaloizou \& Pringle (1983, MNRAS, 202, 1811) to allow the treatment of non-Keplerian disks and from it have derived the steady-state structure of twisted disks that develop from free precession in a nonspherical, logarithmic halo potential. This generalized equation can also be used to examine the time-evolutionary behavior of warped galaxy disks. This work has been supported in part by the US National Science Foundation through grant AST-9008166 and in part by NASA through grant NAGW-2447.
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