103,021 research outputs found
La corrispondenza G. Bellavitis - L. Cremona (1860-1880)
No full textPresso la Biblioteca dell’ Istituto Mazziniano di Genova è conservato il Legato Itala
Cremona Cozzolino donato dalla figlia di Luigi Cremona (1830-1903). Si presentano le 61 lettere spedite a Cremona
da Giusto Bellavitis (1803 -1880), distribuite negli anni dal 1860 al 188
Contributions to automorphisms of affine spaces
No full textWe study aspects of the group G_n of polynomial automorphisms of the affine space A^n, the so-called affine Cremona group. Shafarevich introduced on G_n the structure of an ind-variety, an infinite-dimensional analogon to a (classical) variety. The aim of this thesis is to study G_n within the framework of ind-varieties. The thesis consists of five articles. In the following we summarize them.
1. On the Topologies on ind-Varieties and related Irreducibility Questions.
In the literature there are two ways of endowing an affine ind-variety with a topology. One possibility is due to Shafarevich and the other due to Kambayashi. We specify a large class of affine ind-varieties where these two topologies differ. We give an example of an affine ind-variety that is reducible with respect to Shafarevich’s topology, but irreducible with respect to Kambayashi’s topology. Moreover, we give a counter-example of a supposed irreducibility criterion given by Shafarevich which is different from a counter-example given by Homma. We finish the article with an irreducibility criterion similar to the one given by Shafarevich.
2. On Automorphisms of the Affine Cremona Group (joint with Hanspeter Kraft)
We show that every automorphism of the group G_n is inner up to field automorphisms when restricted to the subgroup TG_n of tame automorphisms. This generalizes a result of Julie Déserti who proved this in dimension n = 2 where all automorphisms are tame, i.e. TG_2 = G_2. The methods are different, based on arguments from algebraic group actions.
3. A Note on Automorphisms of the Affine Cremona Group
Let G be an ind-group and let U be a unipotent ind-subgroup. We prove that an abstract automorphism f: G -> G maps U isomorphically onto a unipotent ind-subgroup of G, provided that f fixes a closed torus T in G that normalizes U and the action of T on U by conjugation fixes only the neutral element. As an application we generalize the main result of the article "On Automorphisms of the Affine Cremona Group" as follows: If an abstract automorphism of G_3 fixes the subgroup of tame automorphisms TG_3, then it also fixes a whole family of non-tame automorphisms (including the Nagata automorphism).
4. Automorphisms of the Plane Preserving a Curve (joint with Jérémy Blanc)
We study the group of automorphisms of the affine plane preserving some given curve, over any field. The group is proven to be algebraic, except in the case where the curve is a bunch of parallel lines. Moreover, a classification of the groups of positive dimension occuring is also given in the case where the curve is geometrically irreducible and the field is perfect.
5. Centralizer of a Unipotent Automorphism in the Affine Cremona Group
Let g be a unipotent element of G_3. We describe the centralizer Cent(g) inside G_3. First, we treat the case when g is a modified translation. In the other case, we describe the subset Cent(g)_u of unipotent elements of Cent(g) and prove that it is a closed normal subgroup of Cent(g). Moreover, we show that Cent(g) is the semi-direct product of Cent(g)_u with a closed algebraic subgroup R of Cent(g). Finally, we prove that the subgroup of Cent(g) consisting of those elements that induce the identity on the algebraic quotient Spec O(A^3)^g form a characteristic subgroup of Cent(g)
Una memoria di confine. Domenico Bordigallo e la nascita della Cremona moderna.
No full textPresentazione dell'edizione dell'Urbis Cremonae syti designum di Domenico Bordigallo, a cura di E. Zanesi, Cremona 2011
Storia di Cremona, volume IV. L'età degli Asburgo di Spagna (1535-1707)
No full textIl volume della Storia di Cremona curato da Politi si caratterizza per un taglio innovativo (non più "l'età spagnola", ma "l'età degli Asburgo di Spagna"), per uno spiccato carattere di ricerca fondamentale, e non di bilancio del già noto o di divulgazione, dei diversi saggi, e per la volontà di aprire fronti conoscitivi nuovi, quali per esempio quelli della comunità evangelica cremonese a Ginevra, della Comunità del secondo Seicento o degli intensi rapporti economici fra Cremona e la Serenissima
Il Carteggio Cremona-Tardy (1860-1886)
No full textIn questo volume è pubblicata la corrispondenza tra Placido Tardy e Luigi Cremona. Si tratta complessivamente di 124 lettere, di cui 74 sono le lettere di Cremona a Tardy e sono conservate presso la Biblioteca Universitaria di Genova nella Cassetta Loria, mentre le 50 sono le lettere di Tardy a Cremona sono conservate presso L’istituto Mazziniano (Museo del Risorgimento) di Genova e fanno parte del Legato Itala Cremona Cozzolino. Da un punto di vista cronologico le lettere si possono suddividere in quattro periodi. Un primo gruppo (Maggio 1860), che riguarda le lettere del primo periodo milanese di Cremona, quando egli ancora ambiva ad una cattedra universitaria. Un secondo gruppo (Ottobre 1860-Settembre 1866), che riguarda le lettere del periodo bolognese di Cremona, quando egli era un giovane professore universitario già avviato a una brillante carriera di caposcuola. Un terzo gruppo (Gennaio 1867- Giugno 1870), che riguarda le lettere del secondo periodo milanese di Cremona, quando era professore al Politecnico. Un quarto gruppo (Ottobre 1875-Marzo 1885), che riguarda le lettere del periodo romano di Cremona, quando era divenuto oramai un personaggio autorevole anche sul piano politico.
Il quadro di riferimento di tale progetto è quello dell’edizione della corrispondenza dei matematici italiani dell’Ottocento, e si colloca in continuità con quella, già intrapresa da qualche tempo, riguardante la corrispondenza di L. Cremona
Association between PM10, PM2.5, NO2, O3 and self-reported diabetes in Italy: A cross-sectional, ecological study
No full textIntroduction Air pollution represents a serious threat to health on a global scale, being responsible for a large portion of the global burden of disease from environmental factors. Current evidence about the association between air pollution exposure and Diabetes Mellitus (DM) is still controversial. We aimed to evaluate the association between area-level ambient air pollution and self-reported DM in a large population sample in Italy. Materials and methods We extracted information about self-reported and physician diagnosed DM, risk factors and socio-economic status from 12 surveys conducted nationwide between 1999 and 2013. We obtained annual averaged air pollution levels for the years 2003, 2005, 2007 and 2010 from the AMS-MINNI national integrated model, which simulates the dispersion and transformation of pollutants. The original maps, with a resolution of 4 x 4 km2, were normalized and aggregated at the municipality class of each Italian region, in order to match the survey data. We fit logistic regression models with a hierarchical structure to estimate the relationship between PM10, PM2.5, NO2 and O3 four-years mean levels and the risk of being affected by DM. Results We included 376,157 individuals aged more than 45 years. There were 39,969 cases of DM, with an average regional prevalence of 9.8% and a positive geographical North-to-South gradient, opposite to that of pollutants’ concentrations. For each 10 μg/m3 increase, the resulting ORs were 1.04 (95% CI 1.01–1.07) for PM10, 1.04 (95% CI 1.02–1.07) for PM2.5, 1.03 (95% CI 1.01–1.05) for NO2 and 1.06 (95% CI 1.01–1.11) for O3, after accounting for relevant individual risk factors. The associations were robust to adjustment for other pollutants in two-pollutant models tested (ozone plus each other pollutant). Conclusions We observed a significant positive association between each examined pollutant and prevalent DM. Risk estimates were consistent with current evidence, and robust to sensitivity analysis. Our study adds evidence about the effects of air pollution on diabetes and suggests a possible role of ozone as an independent factor associated with the development of DM. Such relationship is of great interest for public health and deserves further investigation. © 2018 Orioli et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Automorphisms of the affine Cremona group
No full textWe show that every automorphism of the group Gn := Aut(An) of polynomial automorphisms of complex affine n-space An = Cn is inner up to field automorphisms when restricted to the subgroup TGn of tame automorphisms. This generalizes a result of Julie Deserti who proved this in dimension n = 2 where all automorphisms are tame: TG2 = G2. The methods are different, based on arguments from algebraic group actions
Modular symbols over number fields
No full textLet K be a number field, R its ring of integers. For some classes of fields, spaces of cusp forms of weight 2 for GL(2;K) have been computed using methods based on modular symbols. J.E. Cremona [9] began the programme of extending the classical methods over Q to the case of imaginary quadratic fields. This work was continued by some of his Ph.D. students [35, 6, 22], and results have been obtained for some imaginary quadratic fields with small class number. More recently, P. Gunnells and D. Yasaki [18] have developed related algorithms for real quadratic fields.
The aim of this thesis is to contribute to the extension of the modular symbols method, when possible developing algorithms and implementations for effective computations. Some parts of the theory are purely algebraic and can be extended to all number fields. We generalise the theory for cusps and Manin symbols; we also describe a generalisation of Atkin-Lehner involutions and study other normaliser elements. On the other hand, all previous explicit computations for the imaginary quadratic field case were done only for specific fields. In the last part of this thesis we begin work towards a general implementation of the techniques used in this case. In particular, we are able to compute a fundamental domain of the hyperbolic 3-space for any imaginary quadratic field.
Implementations of the algorithms described in this thesis have been written by the author in the open-source mathematics software Sage [31]
Per l'attività giovanile di Girolamo da Cremona
No full textIl saggio analizza l'attività giovanile del miniatore Girolamo da Cremona presentando nuove opere e precisando l'evoluzione stilistica dell'artista
Danimarca: intersezionalità e parità di genere nei procedimenti di nomina delle autorità indipendenti
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