| Title: | A d.c. $C^1$ function need not be difference  of convex $C^1$ functions (English) | 
| Author: | Pavlica, David | 
| Language: | English | 
| Journal: | Commentationes Mathematicae Universitatis Carolinae | 
| ISSN: | 0010-2628 (print) | 
| ISSN: | 1213-7243 (online) | 
| Volume: | 46 | 
| Issue: | 1 | 
| Year: | 2005 | 
| Pages: | 75-83 | 
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| Category: | math | 
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| Summary: | In [2] a delta convex function on $\Bbb R^2$ is constructed which is strictly differentiable at $0$ but it is not representable as a difference of two convex function of this property. We improve this result by constructing a delta convex function of class $C^1(\Bbb R^2)$ which cannot be represented as a difference of two convex functions differentiable at 0. Further we give an example of a delta convex function differentiable everywhere which is not strictly differentiable at 0. (English) | 
| Keyword: | differentiability | 
| Keyword: | delta-convex functions | 
| MSC: | 26B05 | 
| MSC: | 26B25 | 
| idZBL: | Zbl 1121.26011 | 
| idMR: | MR2175860 | 
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| Date available: | 2009-05-05T16:49:41Z | 
| Last updated: | 2012-04-30 | 
| Stable URL: | http://hdl.handle.net/10338.dmlcz/119509 | 
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| Reference: | [2] Kopecká E., Malý J.: Remarks on delta-convex functions.Comment. Math. Univ. Carolinae 31.3 (1990), 501-510. MR 1078484 | 
| Reference: | [3] Penot J.-P., Bougeard M.L.: Approximation and decomposition properties of some classes of locally d.c. functions.Math. Programming 41 (1988), 195-227. Zbl 0666.49005, MR 0945661 | 
| Reference: | [4] Rockafellar R.T.: Convex Analysis.Princeton University Press, Princeton (1970). Zbl 0193.18401, MR 0274683 | 
| Reference: | [5] Shapiro A.: On functions representable as a difference of two convex functions in inequality constrained optimization.Research report University of South Africa, 1983. | 
| Reference: | [6] Veselý L., Zajíček L.: Delta-convex mappings between Banach spaces and applications.Dissertationes Math. 289 (1989), 1-52. MR 1016045 | 
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