Search results for "Geometria"
showing 10 items of 422 documents
Irreducible components of Hurwitz spaces of coverings with two special fibers
2013
In this paper we prove new results of irreducibility for Hurwitz spaces of coverings whose monodromy group is a Weyl group of type B_d and whose local monodromies are all reflections except two.
Two-Perfect Fluid Interpretation of an Energy Tensor
1990
The paper contains the necessary and sufficient conditions for a given energy tensor to be interpreted as a sum of two perfect fluids. Given a tensor of this class, the decomposition in two perfect fluids (which is determined up to a couple of real functions) is obtained.
Smooth 4-Dimensional Thickening of Singular 2-Dimensional Complex in the non Compact Case.
2009
L'articolo estende la teoria dell'ingrossamento 4-dimensionale nel caso non-proprio.
L’ABSIDE, COSTRUZIONE E GEOMETRIE: ALCUNE RIFLESSIONI
2015
The Apse, Construction and Geometry: some Reflections The interest in apses is the result of a chain of episodes, not always connected to one another, outlining a framework for fruitful inquiry. It is no coincidence that this need is felt in a land like Sicily, an island at risk of earthquakes where history has been forced to make do with an unstable and age-old status-quo existing between innovation and resilience. Many of the possible lines of reasoning can be found in the following essays, while in this paper I will try using some examples (not just strictly Sicilian) to clarify the meaning and requirements of this field of investigation, in the awareness of all the limits that a short d…
Geometric Inverse Problems
2023
This up-to-date treatment of recent developments in geometric inverse problems introduces graduate students and researchers to an exciting area of research. With an emphasis on the two-dimensional case, topics covered include geodesic X-ray transforms, boundary rigidity, tensor tomography, attenuated X-ray transforms and the Calderón problem. The presentation is self-contained and begins with the Radon transform and radial sound speeds as motivating examples. The required geometric background is developed in detail in the context of simple manifolds with boundary. An in-depth analysis of various geodesic X-ray transforms is carried out together with related uniqueness, stability, reconstruc…
Projektiivinen geometria
2017
Tässä tutkielmassa käsittellään projektiivista geometriaa aksioomien ja mallien kautta. Tutkielma keskittyy pääasiassa äärellisiin projektiivisiin geometrioihin ja niistä erityisesti tasogeometriaan. Tutkielmassa luodaan kirjallisuuskatsaus projektiivisen geometrian alkuvaiheiden kautta aksioomajärjestelmän luomiseen ja päätyen tutustumaan yksinkertaisimpiin malleihin projektiiviselta tasolta. Samalla tulee todistettua myös projektiivisen geometrian peruslause ja tutustuttua projektiivisen geometrian hyödyllisyyteen käsiteltäessä euklidisen geometrian tilanteita. Euklidisessa geometriassa vallitsevia lauseita voidaan nimittäin tulkita projektiivisessa geometriassa ja tällöin projektiivisen …
On the tensor degree of finite groups
2013
We study the number of elements $x$ and $y$ of a finite group $G$ such that $x \otimes y= 1_{_{G \otimes G}}$ in the nonabelian tensor square $G \otimes G$ of $G$. This number, divided by $|G|^2$, is called the tensor degree of $G$ and has connection with the exterior degree, introduced few years ago in [P. Niroomand and R. Rezaei, On the exterior degree of finite groups, Comm. Algebra 39 (2011), 335--343]. The analysis of upper and lower bounds of the tensor degree allows us to find interesting structural restrictions for the whole group.
Le scale elicoidali in pietra. Il caracol de husillo nel Palazzo Reale a Palermo
2008
A classification of $\protect \mathbb{R}$-Fuchsian subgroups of Picard modular groups
2018
Asymptoottiset kolmiot hyperbolisessa geometriassa
2016
Elisa Roivainen, Asymptoottiset kolmiot hyperbolisessa geometriassa (engl. Asymptotic Triangles in Hyperbolic Geometry), matematiikan pro gradu -tutkielma, 59 sivua, Jyväskylän yliopisto, Matematiikan ja tilastotieteen laitos, kevät 2016. T ässä työssä esitellään asymptoottisia kolmioita koskevia tuloksia hyperbolisessa geometriassa. Asymptoottisilla kolmioilla tarkoitetaan kolmioita, joiden kärkipisteistä ainakin yksi on niin sanottu äärett ömyyspiste. Kolmion sivuista kaksi lähestyy siis toisiaan asymptoottisesti tuota pistettä kohti, mutta n ämä sivut eivät kuitenkaan leikkaa. Hyperbolisella geometrialla taas tarkoitetaan geometriaa, jossa neutraalin geometrian aksioomien lisäksi aksioom…