# Y. Iwata

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Articles: 2

### Abstract formulation of the Cole-Hopf transform

Yoritaka Iwata

MFAT 25 (2019), no. 2, 142-151

142-151

Operator representation of Cole-Hopf transform is obtained based on the logarithmic representation of infinitesimal generators. For this purpose the relativistic formulation of abstract evolution equation is introduced. Even independent of the spatial dimension, the Cole-Hopf transform is generalized to a transform between linear and nonlinear equations defined in Banach spaces. In conclusion a role of transform between the evolution operator and its infinitesimal generator is understood in the context of generating nonlinear semigroup.

### Infinitesimal generators of invertible evolution families

Yoritaka Iwata

MFAT 23 (2017), no. 1, 26-36

26-36

A logarithm representation of operators is introduced as well as a concept of pre-infinitesimal generator. Generators of invertible evolution families are represented by the logarithm representation, and a set of operators represented by the logarithm is shown to be associated with analytic semigroups. Consequently generally-unbounded infinitesimal generators of invertible evolution families are characterized by a convergent power series representation.