Bourbaki

Definition 1

Tag 08D4, permanent. Cite it as [Bourbaki, Tag 08D4].

Functions of a Real Variable, chapter IV, § 2. LINEAR DIFFERENTIAL EQUATIONS

Given a continuous endomorphism A of E we denote by eAe^A or exp⁡A\exp A the automorphism of E equal to the value at the point t=1t = 1 of the integral of the equation (20) which takes the value I at the point t=0t = 0.

With this notation the remarks preceding def. 1 show that

C(t,t0)=exp⁡(A(t−t0)). C(t, t_0) = \exp \left( A(t - t_0) \right).

The exponential notation just introduced is justified by the following properties, which are entirely analogous to those of the function exp z, for z real or complex (cf. III, p. 98 and 106):

Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.

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Cites

Transcribed from the printed volume. Not translated.