# Search results for: José M. Sigarreta

Acta Mathematica Sinica, English Series > 2019 > 35 > 3 > 338-354

*G*of order

*n*is the polynomial $$B(G;x):={\sum}_{k=-n}^{\partial(G)}B_k(G)x^{n+k}$$ B ( G ; x ) := ∑ k = − n ∂ ( G ) B k ( G ) x n + k , where

*B*

_{k}(

*G*) denotes the number of vertex subsets of

*G*with differential equal to

*k*. We state some properties of

*B*(

*G*;

*x*) and its coefficients. In particular,...

Bulletin of the Iranian Mathematical Society > 2018 > 44 > 2 > 481-503

*H*is a

*minor*of a graph

*G*if a graph isomorphic to

*H*can be obtained from

*G*by contracting some edges, deleting some edges, and deleting some isolated vertices. The study of hyperbolic graphs is an interesting topic since the hyperbolicity of a geodesic metric space is equivalent to the hyperbolicity of a graph related to it. One of the main aims in this work is to obtain quantitative information...

Discussiones Mathematicae Graph Theory > 2017 > 38 > 1 > 301-317

Journal of Mathematical Chemistry > 2018 > 56 > 7 > 1849-1864

Journal of Mathematical Chemistry > 2018 > 56 > 7 > 1865-1883

Discrete Applied Mathematics > 2017 > 225 > C > 22-32

Discrete Applied Mathematics > 2017 > 219 > C > 65-73

Open Mathematics > 2017 > 15 > 1 > 800-814

Discrete Mathematics > 2016 > 339 > 12 > 3073-3084

Journal of Mathematical Chemistry > 2017 > 55 > 7 > 1376-1391

Applied Mathematics and Computation > 2016 > 277 > C > 142-153

_{1}from an algebraic viewpoint. Since this index...

Graphs and Combinatorics > 2015 > 31 > 5 > 1311-1324

*geodesic triangle*$$T=\{x_1,x_2,x_3\}$$ T = { x 1 , x 2 , x 3 } is the union of three geodesics $$[x_1x_2]$$ [ x 1 x 2 ] , $$[x_2x_3]$$ [ x 2 x 3 ] and $$[x_3x_1]$$ [ x 3 x 1 ] in $$X$$ X . The space $$X$$...

Aequationes mathematicae > 2015 > 89 > 5 > 1311-1327

*geodesic triangle*

*T*= {

*x*

_{1},

*x*

_{2},

*x*

_{3}} is the union of the three geodesics [

*x*

_{1}

*x*

_{2}], [

*x*

_{2}

*x*

_{3}] and [

*x*

_{3}

*x*

_{1}] in

*X*. The space

*X*is

*δ-hyperbolic*(in the Gromov sense) if any side of

*T*is contained in a

*δ*-neighborhood of the union of the two other sides, for every geodesic triangle

*T*in

*X*. If

*X*is hyperbolic,...

Electronic Notes in Discrete Mathematics > 2014 > 46 > Complete > 313-320

Electronic Notes in Discrete Mathematics > 2014 > 46 > Complete > 57-64

Electronic Notes in Discrete Mathematics > 2014 > 46 > Complete > 281-288

Electronic Notes in Discrete Mathematics > 2014 > 46 > Complete > 265-272

Discrete Mathematics > 2013 > 313 > 15 > 1575-1585

Proceedings - Mathematical Sciences > 2013 > 123 > 4 > 455-467

*X*is a geodesic metric space and

*x*

_{1},

*x*

_{2},

*x*

_{3}∈

*X*, a

*geodesic triangle*

*T*= {

*x*

_{1},

*x*

_{2},

*x*

_{3}} is the union of the three geodesics [

*x*

_{1}

*x*

_{2}], [

*x*

_{2}

*x*

_{3}] and [

*x*

_{3}

*x*

_{1}] in

*X*. The space

*X*is

*δ*-

*hyperbolic*(in the Gromov sense) if any side of

*T*is contained in a

*δ*-neighborhood of the union of the two other sides, for every geodesic triangle

*T*in

*X*. If

*X*is hyperbolic, we denote by

*δ*(

*X*) the sharp hyperbolicity...

Central European Journal of Mathematics > 2012 > 10 > 3 > 1141-1151

*X*is a geodesic metric space and

*x*

_{1};

*x*

_{2};

*x*

_{3}∈

*X*, a

*geodesic triangle T*= {

*x*

_{1};

*x*

_{2};

*x*

_{3}} is the union of the three geodesics [

*x*

_{1}

*x*

_{2}], [

*x*

_{2}

*x*

_{3}] and [

*x*

_{3}

*x*

_{1}] in

*X*. The space

*X*is

*δ-hyperbolic*(in the Gromov sense) if any side of

*T*is contained in a

*δ*-neighborhood of the union of the two other sides, for every geodesic triangle

*T*in

*X*. We denote by

*δ*(

*X*) the sharp hyperbolicity constant of

*X*...