Abstract of a paper by Horst Martini, Konrad J. Swanepoel, and P. Oloff de Wet
This is an announcement for the paper "Absorbing angles, Steiner minimal trees, and antipodality" by Horst Martini, Konrad J. Swanepoel, and P. Oloff de Wet. Abstract: We give a new proof that a star $\{op_i:i=1,\dots,k\}$ in a normed plane is a Steiner minimal tree of its vertices $\{o,p_1,\dots,p_k\}$ if and only if all angles formed by the edges at $o$ are absorbing [Swanepoel, Networks \textbf{36} (2000), 104--113]. The proof is more conceptual and simpler than the original one. We also find a new sufficient condition for higher-dimensional normed spaces to share this characterization. In particular, a star $\{op_i: i=1,\dots,k\}$ in any CL-space is a Steiner minimal tree of its vertices $\{o,p_1,\dots,p_k\}$ if and only if all angles are absorbing, which in turn holds if and only if all distances between the normalizations $\frac{1}{\|p_i\|}p_i$ equal $2$. CL-spaces include the mixed $\ell_1$ and $\ell_\infty$ sum of finitely many copies of $R^1$. Archive classification: math.MG math.FA Mathematics Subject Classification: 46B20 (Primary). 05C05, 49Q10, 52A21 (Secondary) Citation: Journal of Optimization Theory and Applications, 143 (2009), The paper may be downloaded from the archive by web browser from URL http://front.math.ucdavis.edu/1108.5046 or http://arXiv.org/abs/1108.5046
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alspach@math.okstate.edu