By Augustin Fruchard

The goal of those lecture notes is to strengthen a concept of asymptotic expansions for services regarding variables, whereas even as utilizing capabilities concerning one variable and features of the quotient of those variables. Such composite asymptotic expansions (CAsEs) are quite well-suited to describing recommendations of singularly perturbed traditional differential equations close to turning issues. circumstances indicate internal and outer expansions close to turning issues. therefore our process is heavily concerning the strategy of matched asymptotic expansions. circumstances supply specified benefits, in spite of the fact that. First, they supply uniform expansions close to a turning aspect and clear of it. moment, a Gevrey model of instances is offered and specific within the lecture notes. 3 difficulties are provided during which instances are invaluable. the 1st program issues canard options close to a a number of turning element. the second one software issues so-called non-smooth or angular canard recommendations. eventually an Ackerberg-O’Malley resonance challenge is solved.

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Extra resources for Composite Asymptotic Expansions

Example text

Similarly, we 40 2 Composite Asymptotic Expansions: General Study also get pn2 Ce n1 Ä e n2 , this contradicts the assumption n2 ¤ 0. Since n1 < n2 and e t u that the product ye y is reduced to the monomial Ák . e. at least one of the fast terms gn is non zero. Here we would like to discuss the case of a domain with two vertices on its boundary. The following statement shows that it not necessary to generalize the concept of CAsE for uniform expansions on domains that have several vertices on their boundary, because we can reduce this situation to the case of a single vertex.

3 Composite Expansions: Definition and Basic Properties 27 Integration. V /. If all these terms are absent, integration poses no problem, as the following statement shows. 8. X 2 / as X ! 1. ˛ Z 1 ; ˇ1 ; r0 /. x; Á/ 7! t; Á/ dt has a CAsE. T / d T . r; Á/ with the formal series in which Gn 1 . r / has been Here we have identified Y Á replaced by its asymptotic expansion as Á ! 0. V /. Before stating the result in the general case, we introduce some notation. g. X / with … V . X 2 C L2 / with L Á large enough.

D n 0 gn1 Á . ˛1 ; ˇ1 ; r0 /. T / d T . r; Á/ with the formal expression obtained by replacing Again, we have identified Y r r ` Á and Hn Á by their expansions as Á tends to 0. Proof. Á/ as asymptotic expansion. 8, so its integral has a CAsE. The “generalized CAsE” for y follows. t u We also have a statement similar to the classical Borel–Ritt theorem. Á/ defined and holomorphic on S and having the formal series 1 a Á as n nD0 asymptotic expansion. an /n2N is a sequence of bounded analytic functions of a complex variable x.