scholarly journals The Geodesic Carathéodory Number

2018 ◽  
Author(s):  
Eduardo S. Lira ◽  
Diane Castonguay ◽  
Erika M. M. Coelho ◽  
Hebert Coelho
Keyword(s):  

Do teorema de Carathéodory surge a definição do número de Carathéodory para grafos. Este número é bem conhecido nas convexidades monofônica e de caminho de triângulos. Ele é limitado para algumas classes de grafos nas convexidades P3 e geodésica, mas apenas na convexidade P3 sabe-se que ele é ilimitado. Neste artigo, nós provamos que o número de Carathéodory é ilimitado na convexidade geodésica.  

COMBINATORICA ◽  
1990 ◽  
Vol 10 (2) ◽  
pp. 185-194 ◽  
Author(s):  
I. Bárány ◽  
M. Perles
Keyword(s):  

2013 ◽  
Vol 510 ◽  
pp. 127-135 ◽  
Author(s):  
Mitre C. Dourado ◽  
Dieter Rautenbach ◽  
Vinícius Fernandes dos Santos ◽  
Philipp M. Schäfer ◽  
Jayme L. Szwarcfiter
Keyword(s):  

Author(s):  
Philipp J. di Dio ◽  
Mario Kummer

AbstractIn this paper we improve the bounds for the Carathéodory number, especially on algebraic varieties and with small gaps (not all monomials are present). We provide explicit lower and upper bounds on algebraic varieties, $$\mathbb {R}^n$$ R n , and $$[0,1]^n$$ [ 0 , 1 ] n . We also treat moment problems with small gaps. We find that for every $$\varepsilon >0$$ ε > 0 and $$d\in \mathbb {N}$$ d ∈ N there is a $$n\in \mathbb {N}$$ n ∈ N such that we can construct a moment functional $$L:\mathbb {R}[x_1,\cdots ,x_n]_{\le d}\rightarrow \mathbb {R}$$ L : R [ x 1 , ⋯ , x n ] ≤ d → R which needs at least $$(1-\varepsilon )\cdot \left( {\begin{matrix} n+d\\ n\end{matrix}}\right) $$ ( 1 - ε ) · n + d n atoms $$l_{x_i}$$ l x i . Consequences and results for the Hankel matrix and flat extension are gained. We find that there are moment functionals $$L:\mathbb {R}[x_1,\cdots ,x_n]_{\le 2d}\rightarrow \mathbb {R}$$ L : R [ x 1 , ⋯ , x n ] ≤ 2 d → R which need to be extended to the worst case degree 4d, $$\tilde{L}:\mathbb {R}[x_1,\cdots ,x_n]_{\le 4d}\rightarrow \mathbb {R}$$ L ~ : R [ x 1 , ⋯ , x n ] ≤ 4 d → R , in order to have a flat extension.


2011 ◽  
Vol 38 ◽  
pp. 105-110 ◽  
Author(s):  
Rommel M. Barbosa ◽  
Erika M.M. Coelho ◽  
Mitre C. Dourado ◽  
Dieter Rautenbach ◽  
Jayme L. Szwarcfiter
Keyword(s):  

2014 ◽  
Vol 06 (04) ◽  
pp. 1450060 ◽  
Author(s):  
Bijo S. Anand ◽  
Manoj Changat ◽  
Iztok Peterin ◽  
Prasanth G. Narasimha-Shenoi

Let G be a graph and W a subset of V(G). A subtree with the minimum number of edges that contains all vertices of W is a Steiner tree for W. The number of edges of such a tree is the Steiner distance of W and union of all vertices belonging to Steiner trees for W form a Steiner interval. We describe both of these for the lexicographic product of graphs. We also give a complete answer for the following invariants with respect to the Steiner convexity: the Steiner number, the rank, the hull number, and the Carathéodory number, and a partial answer for the Radon number.


Author(s):  
Erika M. M. Coelho ◽  
Mitre C. Dourado ◽  
Dieter Rautenbach ◽  
Jayme L. Szwarcfiter

2012 ◽  
Vol 48 (3) ◽  
pp. 783-792 ◽  
Author(s):  
Imre Bárány ◽  
Roman Karasev
Keyword(s):  

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