**Lecture by L.O. Chua.** As previously announced,
professor Leon O. Chua will give a lecture on **Tuesday, July 8, 3.00
pm**, at the "Auditorium of the Graduate College Santa Chiara", Via Valdimontone
1, Siena (note: **not at CSC**, the venue of Siena2003 school). The
title and abstract of the lecture are the following:

THE ORIGIN OF COMPLEXITY Prof. Leon Chua, University of California, Berkeley

Abstract. Complexity will be defined in this lecture as the emergence of nonhomogeneous spatial-temporal patterns in homogeneous media. We will show that no homogeneous physical system can exhibit complexity unless its constituent cells, or their coupling, are locally active in a precise mathematical sense. Constructive mathematical criteria will be given for identifying a subset of the system parameter space where the system is locally active. Contrary to a common misconception, a locally active system need not be unstable at an equilibrium point. The parameter region where a locally active system is asymptotically stable at an isolated cell's equilibrium point is called the edge of chaos. Such a parameter region is often much smaller than the cell's locally active region, and is where complex phenomena are most likely to emerge. Practical mathematical criteria for identifying such parameter region will be given.

A discussion and a coffee break will follow. The
lecture is open to everybody. The participants in the School, if already
in Siena, are especially encouraged to attend.
*(June 26, 2003)*

**Lecture by L.O. Chua. **Professor Leon O.
Chua (EECS Department, University of California at Berkeley) will give
a lecture in the afternoon of Tuesday, July 8 (the day before the beginning
of the School). The lecture will be entitled "The origin of complexity",
and will be given at CSC (the venue of the School). Further details (the
hour, in particular) will be communicated within few days. The lecture
is open to everybody. The participants in the School, if already in Siena,
are especially encouraged to attend the lecture.
*(June 6, 2003)*

**Guided tours. **Two guided tours through Siena
will take place on July 9 and July 10, starting at 18.00 from the CSC (the
venue of the school). Each tour will last 60-90 minutes. An expert of the
history and of the art treasures of Siena will accompany us for a walk
through the town, and will illustrate (in English) the most important monuments.
All participants, lecturers, and their accompanying persons are welcome.
*(June 5, 2003)*