Rendiconti dell'Istituto di Matematica dell'Università di Trieste: an International Journal of Mathematics vol.35 (2003)

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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.

Instructions for Authors Authors are invited to submit their papers by e-mail directly to one of the Managing Editors in PDF format. All the correspondence regarding the submission and the editorial process of the paper are done by e-mail. Papers have to be written in one of the following languages: English, French, German, or Italian. Abstracts should not exceed ten printed lines, except for papers written in French, German, or Italian, for which an extended English summary is required. After acceptance, manuscripts have to be prepared in LaTeX using the style rendiconti.cls which can be downloaded from the web page. Any figure should be recorded in a single PDF, PS (PostScript), or EPS (Encapsulated PostScript) file.

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Recent Submissions

Now showing 1 - 5 of 12
  • Publication
    Dispersive Estimate for the Wave Equation with Short-Range Potential
    (Università degli Studi di Trieste. Dipartimento di Matematica e Informatica, 2003)
    Visciglia, Nicola
    In this paper we consider a potential type perturbation of the three dimensional wave equation: $\Box u + V(x)u = 0 u(x, 0) = 0, \partial_t u(x, 0) = f$, where the potential $V \geq 0$ satisfies the following decay assumption: $|V (x)| \leq \frac{C}{1+|x|^{2+\epsilon_0}}$, for some C, $\epsilon_0 > 0$. We establish some dispersive estimates for the associated propagator.
      865  369
  • Publication
    Blow-up for Semilinear Wave Equations with a Data of the Critical Decay having a Small Loss
    (Università degli Studi di Trieste. Dipartimento di Matematica e Informatica, 2003)
    Kurokawa, Yuki
    ;
    Takamura, Hiroyuki
    It is known that we have a global existence for wave equations with super-critical nonlinearities when the data has a critical decay of powers. In this paper, we will see that a blow-up result can be established if the data decays like the critical power with a small loss such as any logarithmic power. This means that there is no relation between the critical decay of the initial data and the integrability of the weight, while the critical power of the nonlinearity is closely related to the integrability. The critical decay of the initial data is determined only by scaling invariance of the equation. We also discuss a nonexistence of local in time solutions for the initial data increasing at infinity.
      1263  539
  • Publication
    Concentration of Local Energy for Two-dimensional Wave Maps
    (Università degli Studi di Trieste. Dipartimento di Matematica e Informatica, 2003)
    Georgiev, Vladimir
    ;
    Ivanov, Angel
    We construct some particular kind of solution to the two - dimensional equivariant wave map problem with inhomogeneous source term in space-time domain of type $\Omega_\alpha(t) = {x \in \mathbb R^2 : |x|^\alpha < t}$, where $\alpha\in (0, 1]$. More precisely, we take the initial data $(u_0, u_1)$ at time T in the space $H^{1+\epsilon} \times H^\epsilon$ with some $\epsilon > 0$. The source term is in $L^1((0, T); H^\epsilon(\Omega_\alpha(t)))$ and we show that the $H^{1+\epsilon}$ -norm of the solution blows-up, when $t \rightarrow 0_+$ and $\alpha\in (0, 1 − \epsilon)$.
      1079  461
  • Publication
    Isomorphism of Commutative Group Algebras over all Fields
    (Università degli Studi di Trieste. Dipartimento di Matematica e Informatica, 2003)
    Danchev, Peter V.
    It is argued that the commutative group algebra over each field determines up to an isomorphism its group basis for any of the following group classes: • Direct sums of cocyclic groups • Splitting countable modulo torsion groups whose torsion parts are direct sums of cyclics; • Splitting groups whose torsion parts are separable countable • Groups whose torsion parts are algebraically compact • Algebraically compact groups These give a partial positive answer to the R.Brauer’s classical problem.
      682  483
  • Publication
    Functions that are the Directed X-Ray of a Planar Convex Body
    (Università degli Studi di Trieste. Dipartimento di Matematica e Informatica, 2003)
    Black, William
    ;
    Kimble, Jennifer
    ;
    Koop, David
    ;
    Solmon, Donald C.
    We characterize functions that are the directed X-ray of a planar convex body from a source that is a positive distance from the body. In addition to a concavity condition the necessary and sufficient conditions involve the structure of points of zero curvature and a priori estimates for derivatives of the directed X-ray near supporting rays and points of zero curvature. The techniques employed also lead to explicit methods for constructing families of planar convex bodies with a common directed X-ray.
      1143  648