%0 Journal Article %T Semilinear hyperbolic systems in one space dimension with strongly singular initial data %A Kirsten E. Travers %J Electronic Journal of Differential Equations %D 1997 %I Texas State University %X In this article interactions of singularities in semilinear hyperbolic partial differential equations in R^2 are studied. Consider a simple non-linear system of three equations with derivatives of Dirac delta functions as initial data. As the micro-local linear theory prescribes, the initial singularities propagate along forward bicharacteristics. But there are also anomalous singularities created when these characteristics intersect. Their regularity satisfies the following ``sum law'': the ``strength'' of the anomalous singularity equals the sum of the ``strengths'' of the incoming singularities. Hence the solution to the system becomes more singular as time progresses. %K anomalous singularities %K semilinear hyperbolic equations %K delta waves. %U http://ejde.math.txstate.edu/Volumes/1997/14/abstr.html