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On the domain of the implicit function and applications


The implicit function theorem asserts that there exists a ball of nonzero radius within which one can express a certain subset of variables, in a system of equations, as functions of the remaining variables. We derive a lower bound for the radius of this ball in the case of Lipschitz maps. Under a sign-preserving condition, we prove that an implicit function exists in the case of a set of inequalities. Also in this case, we state an estimate for the size of the domain. An application to the local Lipschitz behavior of solution maps is discussed.

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Correspondence to Marco Papi.

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Papi, M. On the domain of the implicit function and applications. J Inequal Appl 2005, 373250 (2005).

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