Dynamics of domain walls and strings

The leading order finite-width corrections to the equation of motion de-scribing the motion of a domain wall are derived. The r&me in which this equation of motion is invalid is discussed. Spherically and cylindrically sym-metric solutions to this equation of motion are found. We also clarify a miscon-ception that has arisen in recent years reguding the rigidity (or otherwise) of cosmic strings. e Operated by Universities Research Association Inc. under contract with the United States Department 01 Energy There has recently been renewed interest in domain walls as possible sources of large scale structure in the universel. With a few exceptions, most of the work done on the motion of walls has used the zero thickness approximation. The numerical studies of Widrow2 and Press, Ryden and Sperge13 have given much insight into the dynamics and evolution of finite thickness walls; however, it would be desirable to develop an analytic description of domain wall evolution which would preferably be model independent. In other words, we would like to obtain an approximate equation for a wall &ace withou