Rendiconti dell'Istituto di Matematica dell'Università di Trieste: an International Journal of Mathematics vol.32 (2001) s1

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https://www.openstarts.units.it/handle/10077/4160

CONTENTS

Gennaro Amendola, Riccardo Benedetti, Francesco Costantino and Carlo Petronio
Branched spines of 3-manifolds and Reidemeister torsion of Euler structures

Mark Baker, Michel Boileau and Shicheng Wang
Towers of covers of hyperbolic 3-manifolds

Stuart Bratholdt and Daryl Cooper
On the topology ofthe character variety of a free group

Maria Rita Casali and Carlo Gagliardi
A code for m-bipartite edge-coloured graphs

Alberto Cavicchioli, Friedrich Hegenbarth and Dušan Repovš
Special classes of closed four-manifolds

Scipio Cuccagna
La stabilità asintotica dei ground states della NLS

Francesco Domenicucci, Massimo Ferri and Giorgio Nicoletti
Local triangle choice for impact computation in the tactile exploration of a virtual surface

Claude Hayat-Legrand, Elena Kudryavtseva, Shicheng Wang and Heiner Zieschang
Degrees of self-mappings of Seifert manifolds with finite fundamental groups

Sadayoshi Kojima
Complex hyperbolic cone structures on theconfiguration spaces

Mattia Mecchia
Hyperbolic 2-fold branched coverings

Alexander Mednykh, Marco Reni, Andrei Vesnin and Bruno Zimmermann
Three-fold coverings and hyperelliptic manifolds: a three-dimensional version of a result of Accola

Michele Mulazzani and Riccardo Piergallini
Lifting braids

Luisa Paoluzzi
On hyperbolic type involutions

Luisa Paoluzzi and Bruno Zimmermann
Finite quotients of the Picard group and related hyperbolic tetrahedral and Bianchi groups

Marco Reni and Andrei Vesnin
Hidden symmetries of cyclicbranched coverings of 2-bridge knots

Marco Reni and Bruno Zimmermann
Finite simple groups acting on 3-manifolds and homology spheres

Yo’av Rieck
Genus reducing knots in 3-manifolds

Beatrice Ruini and Fulvia Spaggiari
Manifold spines and hyperbolicity equations

Makoto Sakuma
Surgery description of orientation-preserving periodic maps on compact orientable 3- manifolds

Martin Scharlemann
Heegaard reducing spheres for the 3-sphere

Jeffrey R. Weeks
A robust algorithm to determine the topology of space from the cosmic microwave background radiation

Details

Editorial policy The journal Rendiconti dell’Istituto di Matematica dell’università di Trieste publishes original articles in all areas of mathematics. Special regard is given to research papers, but attractive expository papers may also be considered for publication. The journal usually appears in one issue per year. Additional issues may however be published. In particular, the Managing Editors may consider the publication of supplementary volumes related to some special events, like conferences, workshops, and advanced schools. All submitted papers will be refereed. Manuscripts are accepted for review with the understanding that the work has not been published before and is not under consideration for publication elsewhere. Our journal can be obtained by exchange agreements with other similar journals.

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Now showing 1 - 5 of 21

Finite Simple Groups Acting on 3-Manifolds and Homology Spheres
(Università degli Studi di Trieste. Dipartimento di Scienze Matematiche, 2001)
Reni, Marco
;
Zimmermann, Bruno
Any fi{}nite group admits actions on closed 3-manifolds, and in particular free actions. For actions with fi{}xed points, assumptions on the type of the fi{}xed point sets of elements drastically reduce the types of the possible groups. Concentrating on the basic case of fi{}nite simple groups we show in the present paper that, if some involution of a fi{}nite simple group G acting orientation-preservingly on a closed orientable 3-manifold has nonempty connected fi{}xed point set, then G is isomorphic to a projective linear group PSL(2, q), and thus of a very restricted type. The question was motivated by our work on the possible types of isometry groups of hyperbolic 3-manifolds occuring as cyclic branched coverings of knots in the 3-sphere. We characterize also fi{}nite groups which admit actions on $\mathbb{Z}_{2}$-homology spheres, generalizing corresponding results for integer homology spheres.
1013 971
A Robust Algorithm to Determine the Topology of Space from the Cosmic Microwave Background Radiation
(Università degli Studi di Trieste. Dipartimento di Scienze Matematiche, 2001)
Weeks, Jeffrey R.
Satellite measurements of the cosmic microwave back-ground radiation will soon provide an opportunity to test whether the universe is multiply connected. This paper presents a new algorithm for deducing the topology of the universe from the microwave background data. Unlike an older algorithm, the new algorithm gives the curvature of space and the radius of the last scattering surface as outputs, rather than requiring them as inputs. The new algorithm is also more tolerant of errors in the observational data.
1062 500
Heegaard Reducing Spheres for the 3-Sphere
(Università degli Studi di Trieste. Dipartimento di Scienze Matematiche, 2001)
Scharlemann, Martin
There is a natural way of indexing the difference between two collections of reducing spheres for the standard genus g Heegard splitting of S3. Any two collections are related by a sequence of collections, any two of which differ by low index, hence in a simple way.
1169 521
Surgery description of orientation-preserving periodic maps on compact orientable 3-manifolds
(Università degli Studi di Trieste. Dipartimento di Scienze Matematiche, 2001)
Sakuma, Makoto
We show that every orientation-preserving periodic diffeomorphism f on a closed orientable 3-manifold M has a \textquotedblleft{}surgery description\textquotedblright{}, that is, there is a framed link $\mathcal{L}\;\textrm{in}\; S^{3}$ which is invariant by a standard rotation $\varphi$ around a trivial knot, such that M is obtained by surgery on $\varphi$ and that f is conjugate to the periodic diff{}eomorphism induced by $\varphi$. We will illustrate this result, by visualizing isometries of the complements of 2-component hyperbolic links with $\leq$ 9 crossings which do not extend to periodic maps of $S^{3}$.
986 705
Manifold Spines and Hyperbolicity Equations
(Università degli Studi di Trieste. Dipartimento di Scienze Matematiche, 2001)
Ruini, Beatrice
;
Spaggiari, Fulvia
We give a combinatorial representation of compact connected orientable 3-dimensional manifolds with boundary and their special spines by a class of graphs with extrastructure which are strictly related to o-graphs defined and studied in [3] and [4]. Then we describe a simple algorithm for constructing the boundary of these manifolds by using a list of 6-tuples of non-negative integers. Finally we discuss some combinatorial methods for determining the hyperbolicity equations. Examples of hyperbolic 3- manifolds of low complexity illustrate in particular cases the constructions and algorithms presented in the paper.
1009 654

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