Exploració per autor "Pfeifle, Julián"
Ara es mostren els items 14-26 de 26
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Kalai's squeezed 3-spheres are polytopal
Pfeifle, Julián (2002)
Article
Accés obertIn 1988, Kalai [5] extended a construction of Billera and Lee to produce many triangulated(d−1)-spheres. In fact, in view of upper bounds on the number of simplicial d-polytopes by Goodman and Pollack [2, 3], he derived ... -
Kalai's squeezed three-spheres are polytopal
Pfeifle, Julián (2001)
Article
Accés obertIn 1988, Kalai [5] extended a construction of Billera and Lee to produce many triangulated(d−1)-spheres. In fact, in view of upper bounds on the number of simplicial d-polytopes by Goodman and Pollack [2,3], he derived ... -
Large final polynomials from integer programming
Pfeifle, Julián (2021-09)
Article
Accés obertWe introduce a new method for finding a non-realizability certificate of a simplicial sphere S. It enables us to prove for the first time the non-realizability of a balanced 2-neighborly 3-sphere by Zheng, a family of ... -
MÈTODES MATEMÀTICS III (Examen 1r quadrimestre, 2n parcial)
Pfeifle, Julián (Universitat Politècnica de Catalunya, 2016-01-11)
Examen
Accés restringit a la comunitat UPC -
On polytopality of Cartesian products of graphs
Pfeifle, Julián; Pilaud, Vincent; Santos Pérez, Francisco Javier (2010-07)
Text en actes de congrés
Accés obertWe study the polytopality of Cartesian products of non-polytopal graphs. On the one hand, we prove that a product of graphs is the graph of a simple polytope if and only if its factors are. On the other hand, we provide ... -
On the monotone upper bound problem
Pfeifle, Julián; Ziegler, Günter M. (2004)
Article
Accés obertThe Monotone Upper Bound Problem asks for the maximal number M(d,n) of vertices on a strictly-increasing edge-path on a simple d-polytope with n facets. More specifically, it asks whether the upper bound M(d,n) ≤ ... -
Overlapping community search for social networks
Padrol Sureda, Arnau; Perarnau Llobet, Guillem; Pfeifle, Julián; Muntés Mulero, Víctor (IEEE Press. Institute of Electrical and Electronics Engineers, 2010)
Text en actes de congrés
Accés obertFinding decompositions of a graph into a family of clusters is crucial to understanding its underlying structure. While most existing approaches focus on partitioning the nodes, real-world datasets suggest the presence ... -
Polygons as sections of higher-dimensional polytopes
Padrol Sureda, Arnau; Pfeifle, Julián (2015-02-09)
Article
Accés obertWe show that every heptagon is a section of a 3-polytope with 6 vertices. This implies that every n-gon with n >= 7 can be obtained as a section of a (2 + [n/7])-dimensional polytope with at most [6n/7] vertices; and ... -
Positive Plücker tree certificates for non-realizability
Pfeifle, Julián (2022-01-24)
Article
Accés obertWe introduce a new method for finding a non-realizability certificate of a simplicial sphere S: we exhibit a monomial combination of classical 3-term Pl¨ucker relations that yields a sum of products of determinants that ... -
Prodsimplicial-neighborly polytopes
Matschke, Benjamin; Pfeifle, Julián; Pilaud, Vincent (2010-11)
Article
Accés obertWe introduce PSN polytopes whose k-skeleton is combinatorially equivalent to that of a product of r simplices. They simultaneously generalize both neighborly and neighborly cubical polytopes. We construct PSN polytopes ... -
Root polytopes and growth series of root lattices
Ardila, Federico; Beck, Matthias; Hosten, Serkan; Pfeifle, Julián; Seashore, Kim (2011)
Article
Accés obertThe convex hull of the roots of a classical root lattice is called a root polytope. We determine explicit unimodular triangulations of the boundaries of the root polytopes associated to the root lattices $A_n$, $C_n$, and ... -
Showing non-realizability of spheres by distilling a tree
Pfeifle, Julián (2021)
Text en actes de congrés
Accés obertIn [Zhe20a], Hailun Zheng constructs a combinatorial 3-sphere on 16 vertices whose graph is the complete 4-partite graph K4;4;4;4. Such a sphere seems unlikely to be realizable as the boundary complex of a 4-dimensional ... -
The rotation graph of k-ary trees is Hamiltonian
Huemer, Clemens; Hurtado Díaz, Fernando Alfredo; Pfeifle, Julián (Crete University Press, 2006)
Article
Accés restringit per política de l'editorialIn this paper we show that the graph of k-ary trees, connected by rotations, contains a Hamilton cycle. Our proof is constructive and thus provides a cyclic Gray code for k-ary trees. Furthermore, we identify a basic ...