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A Mathematical Model for a Contracting Interstellar Cloud

Meri Lisi;  Silvia Totaro — 2009

Bollettino dell'Unione Matematica Italiana

In this paper, we study a one-dimensional mathematical model for a contracting interstellar cloud, with a star inside. Existence and uniqueness of a positive solution are proved by means of the fixed point theorem. A time discretization procedure is given and the case of an expanding interstellar cloud is also considered.

Identification of a localized source in an interstellar cloud: an inverse problem

Meri Lisi;  Silvia Totaro — 2005

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

We study an inverse problem for photon transport in an interstellar cloud. In particular, we evaluate the position x 0 of a localized source q ⁢ x = q 0 ⁢ δ ⁢ x - x 0 , inside a nebula (for example, a star). We assume that the photon transport phenomenon is one-dimensional. Since a nebula moves slowly in time, the number of photons U inside the cloud changes slowly in time. For this reason, we consider the so-called quasi-static approximation u to the exact solution U . By using semigroup theory, we prove existence and uniqueness...

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