1,721,540 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Strong ball coverings of manifolds
No full textWe improve two results of Kobayashi and Tsukui about minimal ball coverings of manifolds, deducing them from the existence theorem of contracted triangulations
Crystallisation moves
No full textA crystallisation of a closed PL manifold is an edge-coloured graph, which represents it via a contracted triangulation. Any two crystallisations of the same manifold are proved to be joined by a finite sequence of moves, two alternative sets of which are defined. A further move in dimension 3 is introduced. Note that this result solve the equivalence theorem for cristallisations of closed manifolds of arbitrary dimension
Ricordo di Mario Pezzana
No full textIl lavoro contiene un ricordo della vita e traccia un quadro dell'attività scientifica di Mario Pezzana, scomparso nel 1999. Contiene inoltre la bibliografia completa degli articoli (oltre 200)relativi a cristallizzazioni ed argomenti connessi, prodotti da ricercatori di vari paesi (Brasile, Spagna, Francia, Slovenia, Messico, Corea, Giappone, USA, Italia)
A characterization of punctured n-spheres
No full textWe prove some graph-theoretical propositions and apply them to a characterization of punctured n-spheres with h boundary components, as the manifolds with vanishing regular genus and hole number equal to h
Alcune proprietà caratteristiche delle triangolazioni contratte
No full textSi confrontano tre differenti metodi per definire il concetto di triangolazione contratta di uno spazio topologico e se ne studiano le principali proprietà. Si fornisce quindi una completa formalizzazione del Teorema di Pezzana sulla triangolazione contratta delle varietà lineari a tratti
On the genus of 4-dimensional products of manifolds
No full textWe determine bounds for the regular genus of any 4-manifold, which is the product of S^1 by a closed 3-manifold, or a product of two closed surfaces. This is done by an explicit construction of a graph representing the manifold, and by finding a minimal regular imbedding of it. Note that the same construction in dimension 3 enables to find the Heegaard genus of S^1 by a closed surbface, thus improving a result obtained, for the orientable case, by M. Ochiai in Yokohama Math J., 25 (1977), 109-112
The only genus zero n-manifold is S^n
No full textAll closed PL n-manifolds of regular genus zero, i.e. admitting a crystallization which regularly imbeds in S^2, are proved to be PL homeomorphic to S^n. A conjecture, implying the Poincarè conjecture in dimension four, is also formulated
- …
