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Inverse Function Theorems and Jacobians over Metric Spaces

Luca Granieri (2014)

Analysis and Geometry in Metric Spaces

We present inversion results for Lipschitz maps f : Ω ⊂ ℝN → (Y, d) and stability of inversion for uniformly convergent sequences. These results are based on the Area Formula and on the l.s.c. of metric Jacobians.

Iterated quasi-arithmetic mean-type mappings

Paweł Pasteczka (2016)

Colloquium Mathematicae

We work with a fixed N-tuple of quasi-arithmetic means M , . . . , M N generated by an N-tuple of continuous monotone functions f , . . . , f N : I (I an interval) satisfying certain regularity conditions. It is known [initially Gauss, later Gustin, Borwein, Toader, Lehmer, Schoenberg, Foster, Philips et al.] that the iterations of the mapping I N b ( M ( b ) , . . . , M N ( b ) ) tend pointwise to a mapping having values on the diagonal of I N . Each of [all equal] coordinates of the limit is a new mean, called the Gaussian product of the means M , . . . , M N taken on b. We effectively...

On the 1/2 Problem of Besicovitch: quasi-arcs do not contain sharp saw-teeth.

Hany M. Farag (2002)

Revista Matemática Iberoamericana

In this paper we give an alternative proof of our recent result that totally unrectifiable 1-sets which satisfy a measure-theoretic flatness condition at almost every point and sufficiently small scales, satisfy Besicovitch's 1/2-Conjecture which states that the lower spherical density for totally unrectifiable 1-sets should be bounded above by 1/2 at almost every point. This is in contrast to rectifiable 1-sets which actually possess a density equal to unity at almost every point. Our present method...

Quantitative Isoperimetric Inequalities on the Real Line

Yohann de Castro (2011)

Annales mathématiques Blaise Pascal

In a recent paper A. Cianchi, N. Fusco, F. Maggi, and A. Pratelli have shown that, in the Gauss space, a set of given measure and almost minimal Gauss boundary measure is necessarily close to be a half-space.Using only geometric tools, we extend their result to all symmetric log-concave measures on the real line. We give sharp quantitative isoperimetric inequalities and prove that among sets of given measure and given asymmetry (distance to half line, i.e. distance to sets of minimal perimeter),...

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