1,721,023 research outputs found
Size homotopy groups for computation of natural size distances
No full textFor every manifold M endowed with a structure described by a function from M to the vector space Rk, a parametric family of groups, called size homotopy groups, is introduced and studied. Some lower bounds for natural size distances are obtained in this way
The complexity of orientable graph manifolds
Full text linkWe give an upper bound for the Matveev complexity of the whole class of closed connected orientable prime graph manifolds; this bound is sharp for all 14502 graph manifolds of the Recogniser catalogue (available at http://matlas.math.csu.ru/?page=search
Strongly-cyclic branched coverings of (1, 1)-knots and cyclic presentations of groups
No full textWe study the connections among the mapping class group of the twice punctured torus, the cyclic branched coverings of (1, 1)-knots and the cyclic presentations of groups. We give the necessary and sufficient conditions for the existence and uniqueness of the n-fold strongly-cyclic branched coverings of (1, 1)-knots, through the elements of the mapping class group. We prove that every n-fold strongly-cyclic branched covering of a (1, 1)-knot admits a cyclic presentation for the fundamental group, arising from a Heegaard splitting of genus n. Moreover, we give an algorithm to produce the cyclic presentation and illustrate it in the case of cyclic branched coverings of torus knots of type (k, hk ± 1)
Corrigendum to “Extending homeomorphisms from punctured surfaces to handlebodies” [Topology Appl. 155 (6) (2008) 610–621]
No full textAbstractWe correct the statements of Theorems 9 and 10 of [A. Cattabriga, M. Mulazzani, Extending homeomorphisms from punctured surfaces to handlebodies, Topology Appl. 155 (2008) 610–621], by adding missing generators, and improve the statement of Theorem 10, by removing some redundant generators
La costruzione delle case del balilla e l'edilizia nell'Italia fascista
No full textIl saggio ripercorre le vicende di realizzazione delle case del balilla più significative e si sofferma sul modo di organizzare i cantieri e di impiegare tecniche costruttive e materiali edilizi. Gli argomenti sono trattati tenendo sullo sfondo la realtà sociale, tecnologica e produttiva e gli sviluppi dell’architettura nell’Italia degli anni trenta del Novecento
Compact n-manifolds via (n+1)-colored graphs: a new approach
Full text linkWe introduce a representation via (n+1)-colored graphs of compact n.manifolds with (possibly empty) boundary, which appears to be very convenient for computer aided study and tabulation
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