These last days, I was thinking I needed the help of a professional mathematician.

I remember a friend of my adolescence sure had career in the field of mathematics.

I found that he did indeed run than expected.

At the same time, I see that I am late:

He died in 2005

I found his obituary on:

http://blogs.iec.cat/scm/wp-content/uploads/sites/20/2011/02/N23.pdf

Javier Chavarriga Soriano:

We offer these notes to give testimony and gratitude to a life dedicated to mathematics.

Javier Chavarriga attended degree in mathematical sciences at the Faculty of Mathematics at the University of Barcelona in the period 1974-1979, specialized in mathematical analysis.

He graduated in June 1979 and obtained the degree of BA, dissertation form in December 1981.

Later, he received his doctorate in mathematical sciences in the same Faculty in November 1985 and obtained the qualification cum laude fit under the direction of Dr. Charles Simon Torres.

During the years 1979-1983 he served as Assistant Professor in the Department of Applied Mathematics and Analysis, University of Barcelona.

Many former students who are now teachers still remember that brand new graduate who taught differential equations and, although he was new to the job, with great intensity transmitted his permanent enthusiasm for mathematics.

He began the 1983-1984 academic year as a lecturer teaching and research at the Faculty of Informatics of the Technical University of Catalonia.

In November 1984 he obtained a position as assistant professor of mathematics interim general at the Faculty of Pharmacy, University of Barcelona, where he developed his teaching activity in the period between November 1984 and June 1992.

In January 1985 he was appointed Associate Professor of Acting and applied mathematics.

In May 1987 contest won by opposition Plaza university professor of applied mathematics at the Department of Applied Mathematics and Analysis, University of Barcelona.

The nineties, there is the restructuring of the Catalan university system. At that time, had only three universities in Catalonia, with several offices in the four provinces of Catalonia.

With such restructuring will restore or create new universities such as the University of Girona, Lleida University and the University Rovira i Virgili.

Emotional and family ties to the land west of the Strip, specifically the town of Sena, a little more than fifty kilometers from the city of Lleida, meant that during this period of change, relying on its joining the University of Lleida, which later feel very proud.

So in October 1992 he joined the mathematics section of Segriá Polytechnic University of Catalonia, the School of Agricultural Engineering of Lleida.

This center was assigned to the University of Lleida in November of the same year.

Finally, in June 1995 he obtained the post of Associate Professor of Applied Mathematics at the Department of Mathematics of the University of Lleida.

From then until his death, we have shared with him a good part of their research interests and scientific study.

It is in this latter university where he developed the main and most fruitful of his teaching and research work.

Javier was one of the initiators of the new Department of Mathematical our University and served as director for a long period.

His big dream was to form a research group in dynamical systems: I wanted to create a school.

To achieve his aim he began to search students and started a PhD course entitled Mathematical Modelling, some members of our Department we take as his disciples.

Of these, Jaume Gine remained as doctors and thus created the initial core of our research group. In 1995 it incorporated Isaac A. García.

The beginning was quite hard and narrowness: we still remember the office of four square meters shared by all three of the old rectory building.

It is a period marked by great sacrifices and many hours of dedication to work.

In this period, Javier showed some of the great virtues that characterize such drive and willpower, he can overcome any obstacles magnitude, and high estimate for a job well done.

The fruits of these efforts are evident with the recognition of many members of the international scientific community and are held the first collaborations and visits.

Establishing scientific collaborations major national and international scale.

Without pretending to be exhaustive, teachers like Hector Giacomini, University of Tours, and Jaume Armengol Gasull Book, UAB Mijhail Popescu, Institute of Mathematics, Bucharest, Laurent Cairo, University of Orleans, Mircea Sofonea, University of Perpignan, Marco Sabatini, University of Trento, etc.., were some of the visiting professors during this initial period.

The consolidation of the research group and Dynamical Systems Seminar these collaborations contributed to the organization of congresses, among which we highlight the Catalan Days of Applied Mathematics and two editions of the Symposium on Planar Vector Fields.

Later, the group was expanded with PhD Joseph Mallol George Sorolla y Maite Grau, so that the continuity of the School of Dynamic Systems, created by Javier, was guaranteed and, therefore, the initial goal of Javier, accomplished.

About the research done, we can frame the continuous dynamic systems and, in particular, in dimension two. These systems can be thought as ordinary differential equations that have been parameterized by a temporary variable.

Are remarkable his contributions to the problem of the center and the integrability problem. He also devoted to the study of topics such as isochronous centers, reversibility, nilpotent and degenerate systems, bifurcations, limit cycles (Hilbert's 16th problem) Lie symmetries, differential equations in the complex projective plane etc..

In recent times was one of the main proponents of the theory of Darboux integrability . This theory is based on the fact that the determination of a sufficiently high number of algebraic solutions to a dynamical system in the plane , if they exist, can give a first integral of the system. The French mathematician Gaston Darboux started this theory and , after reading the report , Javier , with his proverbial mathematical intuition , saw the beginning ideas of Darboux theory of algebraic differential equations , which aims to study the characteristics of invariant algebraic curves of a differential system and its relationship with other system solutions .

Was led largely to the study of these invariant algebraic curves , which allowed him to find families of systems with properties integrability interesting new examples of algebraic limit cycles for quadratic systems and identify properties for systems with quadratic rational first integral.

In July 2002, Javier won the position of university professor of applied mathematics, which was the culmination of the academic and research conducted until then in his college career.

Added to the above, Javier Chavarriga worried about the spread and dissemination of mathematics and science in general, and organized several cycles with conferèmcies Lleida Studies Institute (IEI), of which he was director, at the Institute of Education Sciences (ICE), or from the University of Lleida, where he taught elective courses open to all students of the University and for secondary school teachers.

These popular courses we emphasize math lessons, which led to a great turnout.

In teaching and in the Polytechnic School (EPS), we noted that Javier was involved in the establishment of industrial engineering studies from the initial course from 1997 to 1998, as professor the course of calculation, and collaborated actively in the consolidation degree.

We note that Javier knew how to make attractive the subjects taught and was much appreciated and respected by his students. This is evident, for example, the number of times he was required to sponsor various promotions.

The last stage of Javier has been a member of the management team of the Polytechnic School. Over the past year and a half, Javier led all his hopes and efforts towards the school, and promote the creation of technical studies of architecture, which has been a big fan, as well as the opening of the Center Applied Energy Research (CREA).

In recent months participated in the development of a postgraduate course in engineering and information technology, and got the approval necessary to carry out the project.

As we see, one of the features that was defined seek consensus among people.

From his more human side, all we've been close to him can testify to the great devotion toward his father, to his wife, Cristina, and of course and above all, to his children Marta Xavier, of which he was very proud.

In addition to science, Javier has taught us many things in life and not infrequently has served as a model thanks to his drive and his desire to work, to understand the problems, etc..

His legacy remains in us and in any case it would be if we had not known and we have set considerably.

Now we are sure that we encourage everyone with its unique way of life and his laugh, move forward.

Continue its work, the fruit of his work and dedication is the best way to keep remembering it.

A hug, Javier.

Isaac A. García, Jaume Giné, Maite Grau, Josep Mallol i Jordi Sorolla

A hug from me, too!

(If it really outside possible)

Maurici