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A differential equation related to the l p -norms

Jacek Bojarski, Tomasz Małolepszy, Janusz Matkowski (2011)

Annales Polonici Mathematici

Let p ∈ (1,∞). The question of existence of a curve in ℝ₊² starting at (0,0) and such that at every point (x,y) of this curve, the l p -distance of the points (x,y) and (0,0) is equal to the Euclidean length of the arc of this curve between these points is considered. This problem reduces to a nonlinear differential equation. The existence and uniqueness of solutions is proved and nonelementary explicit solutions are given.

A differential inclusion : the case of an isotropic set

Gisella Croce (2005)

ESAIM: Control, Optimisation and Calculus of Variations

In this article we are interested in the following problem: to find a map u : Ω 2 that satisfies D u E a.e. in Ω u ( x ) = ϕ ( x ) x Ω where Ω is an open set of 2 and E is a compact isotropic set of 2 × 2 . We will show an existence theorem under suitable hypotheses on ϕ .

A differential inclusion: the case of an isotropic set

Gisella Croce (2010)

ESAIM: Control, Optimisation and Calculus of Variations

In this article we are interested in the following problem: to find a map u : Ω 2 that satisfies D u E a.e. in Ω u ( x ) = ϕ ( x ) x Ω where Ω is an open set of 2 and E is a compact isotropic set of 2 × 2 . We will show an existence theorem under suitable hypotheses on φ.

A differential Puiseux theorem in generalized series fields of finite rank

Mickaël Matusinski (2011)

Annales de la faculté des sciences de Toulouse Mathématiques

We study differential equations F ( y , ... , y ( n ) ) = 0 where F is a formal series in y , y , ... , y ( n ) with coefficients in some field of generalized power series 𝕂 r with finite rank r * . Our purpose is to express the support Supp y 0 , i.e. the set of exponents, of the elements y 0 𝕂 r that are solutions, in terms of the supports of the coefficients of the equation, namely Supp F .

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