1 citations · 1 across the 5 of their papers we have counts for
7 papers
A question on the Cauchy problem in the Gevrey classes for weakly hyperbolic equations
Tatsuo Nishitani
For a homogeneous polynomial in with Gevrey coefficients, it is known that the Cauchy problem for any realization of is well-posed in the Gevrey class of o…
A direct energy estimates for effectively hyperbolic operators
Tatsuo Nishitani
This paper is devoted to a simpler derivation of energy estimates compared to previously existing ones, for effectively hyperbolic operators. One of main points is no use of genera…
Diagonal symmetrizers for hyperbolic operators with triple characteristics
Tatsuo Nishitani
Symmetrizers for hyperbolic equations are obtained by diagonalizing the Bezoutian matrix of hyperbolic symbols. Such diagonal symmetrizers are applied to the Cauchy problem for hyp…
Notes on symmetrization by Bezoutiant
Tatsuo Nishitani
Let be a monic hyperbolic polynomial and let be the Bezoutian matrix of and . Then symmetrizes the Sylvester matrix associated with . This fact is observed b…
A Discrete Algorithm for General Weakly Hyperbolic Systems
Ferruccio Colombini, Tatsuo Nishitani, Jeffrey Rauch
This paper studies the Cauchy problem for variable coefficient weakly hyperbolic first order systems of partial differential operators. The hyperbolicity assumption is that for eac…
Cauchy problem for hyperbolic operators with triple effective characteristics on the initial plane
Tatsuo Nishitani, Vesselin Petkov
We study effectively hyperbolic operators with triple characteristics points lying on . Under some conditions on the principal symbol of one proves that the Cauchy pr…