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The metric jets, introduced here, generalize the jets (at order one) of Charles Ehresmann. In short, for a ``good'' map f (said to be ``tangentiable'' at a) between metric spaces, we define its metric jet tangent at a (composed of all the maps which are locally lipschitzian at a and tangent to f at a) called the ``tangential'' of f at a, and denoted Tf_a. So, in this metric context, we define a ``new differentiability'' (called ``tangentiability'') which extends the classical differentiability (while preserving most of its properties) to new maps, traditionally pathologic.
@article{TAC_2010_23_a9, author = {Elisabeth Burroni and Jacques Penon}, title = {A metric tangential calculus}, journal = {Theory and applications of categories}, pages = {199--220}, publisher = {mathdoc}, volume = {23}, year = {2010}, language = {en}, url = {http://geodesic.mathdoc.fr/item/TAC_2010_23_a9/} }
Elisabeth Burroni; Jacques Penon. A metric tangential calculus. Theory and applications of categories, The Bourn Festschrift, Tome 23 (2010), pp. 199-220. http://geodesic.mathdoc.fr/item/TAC_2010_23_a9/