GARETTO, C. and RUZHANSKY, M., 2014. A note on weakly hyperbolic equations with analytic principal part. Journal of Mathematical Analysis and
Applications, 412 (1), pp. 1 - 14.
In this note we show how to include low order terms in the C∞ well-posedness results for weakly hyperbolic equations with analytic time-dependent coefficients. This is achieved by doing a different reduction to a system from the previously used one. We find the Levi conditions such that the C∞ well-posedness continues to hold.
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Engineering and Physical Sciences Research Council