Bøger i Publications of the Scuola Nor serien

Neuronal plasticity is the term generally used to describe a great variety of changes in neuronal structure and functions, in particular activity-dependent, prolonged functional changes, accompanied by corresponding biochemical and possibly morphological alterations. The first insights about neuronal plasticity have been obtained on simple forms of life. Today, many areas in the mammalian central nervous system are under investigation, in particular the cortex and the hippocampus. In these areas, neuronal plasticity is considered to be at the basis of learning and memory. The study of brain plasticity in sensory systems has been particularly fruitful, because these systems can be experimentally manipulated in a very precise manner by changes in the sensory imput.

Little more than one hundred years have gone by since the birth of Ettore Majorana, a highly renowned theoretical physicist. His career was brief and irregular but very intense, and he disappeared in March 1938 in circumstances that are still not completely clear. This volume is a contribution to a better understanding of the scientific, academic and human personality of Ettore Majorana, beyond the layers of legendary aspects which have accumulated over the years. Based on primary sources alone - scientific literature of the period and numerous archival documents - the figure of Ettore Majorana emerges in a completely new light. The young scientist is intensely involved in scientific research, completely independent, always striving to offer innovative contributions of the highest level according to the most advanced international standards, and very determined to make his results known by following a shrewd publication strategy. He is profoundly interested in his academic career, very scrupulous with institutional relationships, and attentive to his students. Moreover, his documented scholarly activity is much wider than previously reported. This historical analysis shows also that Majorana had a very important role in orienting research in Rome, especially in the sector of the statistical model of the atom and in Nuclear Physics. It is also clear that there are aspects of Ettore Majorana's life which transmit a solid historical legacy from the cultural and human points of view, besides the scientific legacy which is universally recognized to him. A rich reproduction of original documents completes the volume.

The experimental achievement of Bose-Einstein condensation (1995) and of Fermi degeneracy (1999) in ultra-cold, dilute gases has opened a new field in atomic physics and condensed matter physics. This thesis presents an overview of theoretical and experimental facts on ultra-cold atomic gases. A Green's function scheme is examined, and the book also applies a novel spin-density-functional approach to the study of Fermi gases inside one-dimensional optical lattices.

Since neutrinos interact so weakly with matter, most of their basic properties are still largely unknown. One of the most important issues to be settled concerns their rest mass. We have no idea why neutrinos are so much lighter than their charged lepton partners; no fundamental symmetry in nature requires massless neutrinos. Massive neutrinos are demanded to explain the anomalous counting rate of experiments measuring the solar and the atmospheric neutrino fluxes. The discrepancy between experimental data and theoretical predictions can be accounted for in terms of neutrino oscillations, which would take place only in the case of massive neutrinos. The subject of this thesis is the search for neutrino oscillations in CHOOZ, the first long baseline experiment to explore a neutrino mass region where hints at neutrino oscillations came from the atmospheric neutrino anomaly.

In this thesis I study the untwisted affine quantum algebras and their specialization at a primitive l-th root of unity. In particular my goal is the complete description of the center, when l is odd. The center of the specialization of the quantum algebra at odd roots of unity is already known in the finite case, that is for finite dimensional semisimple Lie algebras. In this thesis I prove that analogous results hold in the affine untwisted case.

This thesis is devoted to investigating some aspects of the geometry and function theory on domains in complex vector spaces. The link between geometry and function theory stems from the standard approach whereby, if D is a domain in Cn, S is a semigroup of holomorphic maps of D into itself, and Hol(D) is the space of all scalar valued holomorphic functions on D, then S induces a semigroup of linear operators on Hol(D) whose invariant subspaces give information on the structure of S. In the one-dimensional case, the theory of Riemann surfaces leads to precise results. Passing from one to several complex variables the situation changes radically. In order to obtain further information on Aut D, one has to drastically restrict the class of bounded domains D under consideration, focusing the attention on bounded homogeneous domains or even on the narrower class of bounded symmetric domains.

Low energy neutrino astrophysics studies the evolutionary life of the stars via the neutrinos emitted during the quiescent phase (solar neutrinos) and during the explosive death of big mass stars (supernova neutrinos). The neutrino mean free path in matter is about twenty orders of magnitude greater than that of light; therefore neutrinos reaching us can be produced also in deep and high-density levels of stars. Since massless neutrinos are unaffected by their travel in the interstellar space, their energies and arrival directions carry information on the star history. The subject of this thesis is the search for neutrino bursts from galactic stellar gravitational collapses performed in the MACRO experiment, a large area modular detector, operating since autumn 1989.

This book contains expositions of talks of the Colloquio De Giorgi, given by eminent experts and addressed to a 'general' public (audience) of mathematicians. The topics are prepared in such a way that readers will get some idea of recent progress in several mathematical fields.

In the academic year 1994/95 I lectured on semigroups in the Scuola Normale Superiore and in the Politecnico di Torino. The purpose of the lectures was to present to an audience of graduate students a self-contained introduction to the theory of strongly continuous semigroups of linear operators acting on a Banach space. The main trust was concentrated on laying down the basic geometrical aspects of the theory as a background for applications to concrete problems in the analysis of differential operators.

These notes contain lectures on the theory of group representations and its applications to the physics of atoms, molecules and crystals, given at Purdue University, Scuola Normale Superiore (Pisa, Italy) and Universidad Técnica Federico Santa Maria (Valparaiso, Chile) on and off over a period of over 25 years. The topics selected reflect my special interests and their scope is limited by the time available to the students. The style is somewhat concise and will require careful attention on the part of the reader.

We consider in Rn a differential operator P(D), P a polynomial, with constant coefficients. Let U be an open set in Rn and A(U) be the space of real analytic functions on U. We consider the equation P(D)u=f, for f in A(U) and look for a solution in A(U). Hormander proved a necessary and sufficient condition for the solution to exist in the case U is convex. From this theorem one derives the fact that if a cone W admits a Phragmen-Lindeloff principle then at each of its non-zero real points the real part of W is pure dimensional of dimension n-1. The Phragmen-Lindeloff principle is reduced to the classical one in C. In this paper we consider a general Hilbert complex of differential operators with constant coefficients in Rn and we give, for U convex, the necessary and sufficient conditions for the vanishing of the H1 groups in terms of the generalization of Phragmen-Lindeloff principle.

Mathematical theory of discrete time decision processes, also known as stochastic control, is based on two major ideas: backward induction and conditioning. It has a large number of applications in almost all branches of the natural sciences. The aim of these notes is to give a self-contained introduction to this theory and its applications. Our intention was to give a global and mathematically precise picture of the subject and present well motivated examples. We cover systems with complete or partial information as well as with complete or partial observation. We have tried to present in a unified way several topics such as dynamic programming equations, stopping problems, stabilization, Kalman-Bucy filter, linear regulator, adaptive control and option pricing. The notes discuss a large variety of models rather than concentrate on general existence theorems.

The birth of condensed matter physics in Italy is linked to a small number of very distinguished scientists. Mario Tosi, Professor of Physics of Matter at the Scuola Normale Superiore, is unquestionably among the leading figures, a true founder of the theoretical activity in the country and a true catalyst of novel research directions internationally. This volume collects the proceedings of a symposium held at Scuola Normale Superiore di Pisa, designed to show Mario Tosi's broad, deep influence in very diverse areas of the quantum theory of condensed matter. The topics covered in the volume represent the breadth of his interests and the highlights in the quantum theory of condensed matter: liquids, electronic states in complex structures, quantum degenerate gases, many-body physics.

In the present thesis we develop new strategies concerning the use of lanthanide cations as spectroscopic probes for the study of molecular structures in solution. A widespread interest for lanthanides is mainly centered in two large fields: organic synthesis and clinical practice. Systems containing lanthanides enjoy a very favorable situation, since these ions feature high coordination numbers, which assure rich binding chemistry, and at the same time they possess the right spectroscopic properties to monitor it. The present thesis develops the potentialities of electronic spectroscopy of lanthanide systems in solution. We point out and overcome the drawbacks which have mainly hampered this kind of study so far, namely: a sensivity problem, an instrumental problem and a calibration problem.

These Lecture Notes are based on a course given in June 2001 at the Cattedra Galileiana of Scuola Normale Superiore di Pisa. The course consisted of a short introduction into the basic concepts of Mathematical Finance, focusing on the notion of "no arbitrage", and subsequently applying these concepts to portfolio optimization. To avoid technical difficulties I mainly dealt with the situation where the underlying probability space is finite and only sketched the difficulties arising in the general case. We then pass to the scheme of utility optimisation for general semi-martingale models. Some topics of this course are not standard: for example, in the treatment of the general existence theorem for the optimal portfolio, we give a direct proof which is not relying on duality theory. Similarly, the treatment of the asymptotic elasticity of utility functions and a related counter-example are original to these notes.

The lectures concentrate on some old and new relations between quasiderivatives of solutions to Ito stochastic equations and interior smoothness of harmonic functions associated with degenerate elliptic equations. Recent progress in the case of constant coefficients is discussed in full detail.

This is a written version of the Cattedra Galileiana lectures, presented in 2002 at the Scuola Normale in Pisa. The objective is to combine an orientation to credit-risk modeling (emphasizing the valuation of corporate debt and credit derivatives) with an introduction to the analytical tractability and richness of affine state processes. This is not a general survey of either topic, but rather is designed to introduce researchers with some background in mathematics to a useful set of modeling techniques and an interesting set of applications.