Rendiconti dell'Istituto di Matematica dell'Università di Trieste: an International Journal of Mathematics vol.30 (1998)https://www.openstarts.units.it/handle/10077/43152024-05-30T07:43:03Z2024-05-30T07:43:03Z131Irreducible unitary representations of a diffeomorphisms group of an infinite-dimensional real manifoldLüdkovsky, S.V.https://www.openstarts.units.it/handle/10077/43622019-03-02T00:15:28Z1998-01-01T00:00:00Zdc.title: Irreducible unitary representations of a diffeomorphisms group of an infinite-dimensional real manifold
dc.contributor.author: Lüdkovsky, S.V.
dc.description.abstract: Groups of diffeomorphisms $Diff_{\beta,\Upsilon}^{t}$ (M) of infinite-dimensionai
real Banach manifolds M are defined. Their structure is studied. Irreducible
unitary representations of a group of diffeomorphisms associated with
quasi-invariant measures on a Banach manifold are constructed.
1998-01-01T00:00:00ZDetermination of convex bodies from $\pm \infty$-chord functionsSoranzo, Alessandrohttps://www.openstarts.units.it/handle/10077/43612019-03-02T22:35:18Z1998-01-01T00:00:00Zdc.title: Determination of convex bodies from $\pm \infty$-chord functions
dc.contributor.author: Soranzo, Alessandro
dc.description.abstract: We generalize the concept of i-chord function to the cases $i=+\infty$
and $i=-\infty$, and we extend two results concerning the determination
of convex bodies from i-chord functions to those new values of i.
1998-01-01T00:00:00ZTwistor Bundles of Almost Symplectic ManifoldsNannicini, Antonellahttps://www.openstarts.units.it/handle/10077/43602019-03-02T05:44:13Z1998-01-01T00:00:00Zdc.title: Twistor Bundles of Almost Symplectic Manifolds
dc.contributor.author: Nannicini, Antonella
dc.description.abstract: In this paper we introduce the twistor bundle of a 2n-dimensional
almost symplectic manifold M as the quotient bundle $\frac{P\left(M,Sp\left(2n\right)\right)}{U\left(n\right)}$.
Given a symplectic connection on M we introduce a natural almost Hermitian
structure on the twistor bundle and we prove that this structure is
K$\ddot{\textrm{a}}$hler if and only if M is symplectic and the chosen
connection has vanishing curvature and (0,2)-part of the torsion.
Moreover we prove that in the case of $\mathbb{R}^{2n}$ with standard
symplectic structure the twistor bundle turns out to be K$\ddot{\textrm{a}}$hler
with constant scalar curvature for a certain class of symplectic connections.
1998-01-01T00:00:00ZTotally geodesic horizontally conformal mapsMustafa, M.T.https://www.openstarts.units.it/handle/10077/43592019-03-02T00:14:29Z1998-01-01T00:00:00Zdc.title: Totally geodesic horizontally conformal maps
dc.contributor.author: Mustafa, M.T.
dc.description.abstract: We obtain a characterization of totally geodesic horizontally conformal
maps by a method which arises as a consequence of the Bochner technique
for harmonic morphisms. As a geometric consequence we show that the
existence of a non-constant harmonic morphism $\textrm{Ø}$ from a
compact Riemannian manifold M$^{m}$ of non-negative Ricci curvature
to a compact Riemannian manifold of non-positive scalar curvature,
forces M$^{m}$ either to be a global Riemannian product of integral
manifolds of vertical and horizontal distributions or to be covered
by a global Riemannian product.
1998-01-01T00:00:00ZComplex foliations in generalized twistor spacesMigliorini, MassimilianoTommasini, Adrianohttps://www.openstarts.units.it/handle/10077/43582019-03-02T05:58:46Z1998-01-01T00:00:00Zdc.title: Complex foliations in generalized twistor spaces
dc.contributor.author: Migliorini, Massimiliano; Tommasini, Adriano
dc.description.abstract: We consider a natural almost complex distribution on the associated
bundle $F^{\left(n\right)}M$ to the principal bundle of the g-orthogonal
oriented frames on a Riemannian manifold (M, g), with standard fibre
$\frac{SO\left(2n+k\right)}{U\left(n\right)\times SO\left(k\right)}$:
we find necessary and sufficient conditions ensuring that the distribution
is an almost complex foliation in $F^{\left(n\right)}M$ and we compute
the Nijenhuis tensor. Finally, we characterize the local sections
of $F^{\left(n\right)}M$.
1998-01-01T00:00:00ZA short proof of regularity for solutions to semilinear elliptic problems with exponential critical growthLakkis, O.https://www.openstarts.units.it/handle/10077/43572019-03-02T00:15:25Z1998-01-01T00:00:00Zdc.title: A short proof of regularity for solutions to semilinear elliptic problems with exponential critical growth
dc.contributor.author: Lakkis, O.
dc.description.abstract: We show that the weak solutions of the elliptic semilinear Dirichlet problem (P) are classical solutions. The proof's simplicity is based on the fact that the nonlinearity is of exponential type, in contrast to nonlinearities of polynomial type.
1998-01-01T00:00:00ZSingular behavior of the Dirichlet problem in Hölder spaces of the solutions to the Dirichlet problem in a coneNajmi, MohamedLabbas, RabahMoussaoui, Mohandhttps://www.openstarts.units.it/handle/10077/43562019-03-02T04:56:25Z1998-01-01T00:00:00Zdc.title: Singular behavior of the Dirichlet problem in Hölder spaces of the solutions to the Dirichlet problem in a cone
dc.contributor.author: Najmi, Mohamed; Labbas, Rabah; Moussaoui, Mohand
dc.description.abstract: In the present study we consider the solution of the Dirichlet problem
in conical domain. For general elliptic problems in non Hilbertian
Sobolev spaces built on $L^{p},1<p<\infty$ the theory of sums of
operators developed by Dore-Venni $\left[8\right]$ provides an optimal
result. Holder spaces, as opposed to LP spaces, are not UMD. Using
the results of Da Prato-Grisvard $\left[6\right]$ and Labbas $\left[14\right]$
we cope with the singular behaviour of the solution in the framework
of H$\ddot{\textrm{o}}$lder and little H$\ddot{\textrm{o}}$lder
spaces.
1998-01-01T00:00:00ZAnalogue of Gidas-Ni-Nirenberg result in hyperbolic space and sphereKumaresan, S.Prajapat, Jyotshanahttps://www.openstarts.units.it/handle/10077/43552019-03-02T05:44:10Z1998-01-01T00:00:00Zdc.title: Analogue of Gidas-Ni-Nirenberg result in hyperbolic space and sphere
dc.contributor.author: Kumaresan, S.; Prajapat, Jyotshana
dc.description.abstract: Let $u\epsilon C^{2}\left(\overline{\Omega}\right)$be a positive
solution of the differential equation $\Delta u+f\left(u\right)=0$
in $\Omega$ with boundary condition u=0 on $\partial\Omega$ where
f is a C$^{1}$ function and $\Omega$ is a geodesic ball in the hyperbolic
space $\mathbf{H}^{\mathbf{n}}$ $\left(\textrm{respectively}\:\textrm{sphere}\:\mathbf{S^{\mathbf{n}}}\right)$.
Further in case of sphere we assume that $\overline{\Omega}$ is contained
in a hemisphere. Then we prove that u is radially symmetric.
1998-01-01T00:00:00ZSemi-free circle actions: the multiplicative structureKiihl, J. Carlos S.Izepe Rodrigues, Claudinahttps://www.openstarts.units.it/handle/10077/43542019-03-02T00:15:20Z1998-01-01T00:00:00Zdc.title: Semi-free circle actions: the multiplicative structure
dc.contributor.author: Kiihl, J. Carlos S.; Izepe Rodrigues, Claudina
dc.description.abstract: In this paper we study the bordism groups of manifolds with semi-free
$S^{1}$-actions, denoted by $SF_{n}\left(S^{1}\right)$. We study
the multiplicative structure by using a J -homomorphism map. We also
study the construction K, which gives a set of multiplicative generators,
presenting an algebraic interpretation of this geometric construction.
As an application, we analyze the homomorphisms $r_{p}:SF_{*}\left(S^{1}\right)\rightarrow SF_{*}\left(\mathbb{Z_{\textrm{p}}}\right)$
from the bordism group of semi-free $S^{1}$-actions on the bordism
group of $\mathbb{Z_{\textrm{p}}}$ -actions induced by the restriction
functors.
1998-01-01T00:00:00ZThe $\pi$-weights and $\pi$-characters of hyperspaces with the hit-and-miss topologiesHou, Ji-Chenghttps://www.openstarts.units.it/handle/10077/43532019-03-02T05:35:31Z1998-01-01T00:00:00Zdc.title: The $\pi$-weights and $\pi$-characters of hyperspaces with the hit-and-miss topologies
dc.contributor.author: Hou, Ji-Cheng
dc.description.abstract: We prove that $\pi w\left(\Delta\left(x\right)\right)=\pi\chi\left(\Delta\left(x\right)\right)=\textrm{max}\left\{ \pi w\left(x\right),\tau k\left(\Delta\right)\right\} $
for the hit-and-miss topologies $\tau\Delta$ on the closed subsets
of either a quasi-regular and $\mathbf{R}_{0}$ or $T_{1}$ space
$\left(X,\tau\right)$, where $\tau k\left(\Delta\right)$ is a cardinal
invariant associted with $\Delta$.
1998-01-01T00:00:00Z