Professor S. Havlin: a tribute�

It is a pleasure and a privilege to say a few words about the Guest of Honor of thisConference, Professor Shlomo Havlin. I open with a maxim well known to Shlomoand enunciated by a Talmudic sage: “Much have I learned from my teachers, morefrom my colleagues and most of all from my students”. I think this maxim is relevantto all types of scholarship, and certainly to scienti%c research.When I joined Bar-Ilan in the summer of 1981 Shlomo was a junior member of

sta- in the Physics Department. His main research interest had been in ferroelectricity,and he had published some 25 papers. It is interesting that only one of these wason his own—all of the rest involved collaborators. This points to one of Shlomo’soutstanding characteristics—an enthusiasm for working with other people. He is happyto share even his best ideas and to cooperate in their development; this outgoing naturehas paid very good dividends.Shlomo was the %rst member of the Physics Department with whom I had any

interaction. He was beginning to take an interest in self-avoiding walks and criticalphenomena; I was able to bring him up to date on the current situation and introducedhim to the key papers in the massive literature. He was also keen to learn aboutfractals; I knew Benoit Mandelbrot well—his %rst book had been published a few yearsback, and I was able to provide a personal introduction. We had a few discussions,and I think on the basis of what he learned from me I can claim to have been histeacher for a short period. I want to tell you tonight of the “very much more” whichI have learned from him, my student, in the ensuing years. But %rst, I would like tomention one other positive result of our interaction at this time. Shlomo was due fora long period of sabbatical leave. I suggested that he spend it with my good friendsGeorge Weiss in Washington and Gene Stanley in Boston, and I provided him withstrong recommendations. He accepted my advice, and the results proved extraordinarilyfruitful, as many of you know.A few illustrative facts demonstrate Shlomo’s amazing research output during the

past 20 years. He has participated in the publication of well over 450 papers, 45 ofthem in Physical Review Letters and 10 in Nature. He is the Editor and co-authorof 10 books, and he has delivered over 60 plenary or invited lectures at Scienti%cConferences. Of a long list of Academic Distinctions I shall mention only three: theIsraeli Landau Prize for outstanding research in 1988; the Bar-Ilan Prize for the bestscienti%c paper of 2000; the Israeli Ministry of Science Prize for the best popularscienti%c paper (awarded in 2002). Several of his papers rank high in the CitationIndex.

� After Dinner Address at the Conference Banquet.

doi:10.1016/j.physa.2003.08.020

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I would like to focus on the service, which I think that Shlomo and his colleaguesGeorge Weiss, Armin Bunde, Gene Stanley, Danny Ben Avraham and other like-mindedindividuals at this conference and elsewhere, have rendered to the Physics communityat large.Let me %rst reminisce and tell you of the Battelle Colloquium on Critical Phe-

nomena held in Geneva in 1970 to celebrate the 25th anniversary of the publica-tion of Onsager’s classic paper. There were very exciting developments reDected inthe program of the Colloquium, and the organizers had invited Leon van Hove, adistinguished theoretical physicist and one of the Directors of CERN, to give theafter-dinner address. Van Hove [1] chose as topic “The Changing Face of Physics”and he started by emphasizing what he regarded as the basic task of physics: “weshould constantly recall and reassert that elucidation of the fundamental laws re-mains the most essential task of physics”. He then proceeded to tell us that whatwe were discussing should really be regarded as chemistry rather than physics—all the basic laws governing our phenomena were known, we were concerned onlywith intermediate concepts to obtain a quantitative understanding of the phenom-ena. By this criterion, none of the papers presented at our present conference arereally physics. A similar attitude was adopted by Stephen Hawking in his Inaugu-ral Lecture, which he entitled “The End of Physics?” He envisaged that all remain-ing fundamental problems in physics would be solved, possibly by super-computers,in the not too distant future and Physics would then close down. A bleak prospectindeed.Fortunately, an alternative point of view has been put very coherently by John Ziman

[2]: “Think of physics as the ‘fundamental’ science and it is oversubscribed almost tobankruptcy. But, de%ne it as the science whose aim is to describe natural phenomenain the most mathematical or numerical language, and you will understand its pastand have con%dence in its future... The task of the modern physicist is to determinethe mathematically comprehensible characteristics of the natural world and of humanartifacts...”I think all of us here can identify with Ziman’s formulation of the aim of modern

physics. What Shlomo and his colleagues have done is to show how widely the netcan be spread. (This is also reDected in many of the papers at this conference.) Let uslook at the titles of a few of their papers:“Magnitude and Sign Correlations in Heartbeat Fluctuations”. This is not medicine

but physics.“Breakdown of the Internet under International Attack”. This is not computer science

but physics.“Global Climate Models Violate Scaling of the Observed Atmospheric Variability.”

This is not meteorology but physics!With admirable discretion, all of these papers were sent to, and published by, the

premier world physics journal, Physical Review Letters; a remarkable substantiation ofZiman’s “the mathematically comprehensible characteristics of the natural world andof human artifacts”. Many other examples of a similar kind could be quoted.Let me return to statistical mechanics and continue my reminiscences on critical

phenomena. The early 1970s registered incredible progress. The concepts of scaling

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and universality crystallized, and Kenneth Wilson by his brilliant adaptation of therenormalization group from high-energy physics showed how these concepts couldbe explained theoretically and their consequences calculated mathematically. For this,he was awarded a Nobel Prize in 1982. De Gennes showed how self-avoiding walks%tted into the picture, and Kasteleijn and Fortuin extended the treatment topercolation.There could not have been a better demonstration of the narrowness of the outlook

of van Hove for whom this remarkable achievement would not have been part of“physics”.The Dood of papers triggered by these developments cleared up all of the outstand-

ing problems in the %eld, and by the time I arrived at Bar-Ilan in 1981, I and mostof the older generation in critical phenomena felt that there were only a few crumbsleft, and a mass migration took place to apparently greener pastures. But the youngergeneration, to which Shlomo and his colleagues belong, generated a new vitality byapplying the ideas of critical phenomena in totally new areas. “Scaling Behavior inthe Growth of Companies”, “Scaling and Crossover in Heartbeats”, “Scaling Conceptsand Complex Fluids”, “Long Range Correlations in DNA”, “Modeling Urban GrowthPatterns”, “Indication of a Universal Persistence Law Governing Atmospheric Variabil-ity”, “Percolation Theory and Avalanches”. Note that Ziman’s de%nition of physics isextended to cover economic and social phenomena. I can again add that several of thepapers at this conference are also in this category.I have so far dealt only with the pioneering and less conventional aspects of Shlomo’s

research. But he has also contributed substantially to conventional research. WithGeorge Weiss, he has obtained signi%cant new results on the random walk problem;with Danny Ben Avraham he has investigated di-usion in disordered media; he hasrevealed interesting aspects of percolation theory, and has found new practical appli-cations; and most of all he has devoted energy and enthusiasm to the exploration andpromulgation of fractals.May I add %nally that the excitement and interest generated by last night’s Poster

session provide simple evidence of the fertility of Shlomo’s imagination. He had ahand in several of the papers presented, but with his usual modesty his name does notappear in a position of much prominence.Shlomo comes from a family background well versed in Jewish scholarship, and he

has maintained the family tradition. When I visited him while he was mourning for hisfather, he proudly showed me some of his father’s learned publications. A major aim ofBar-Ilan University is to show how %rst-rate scienti%c research can be combined withmaintenance of Jewish tradition and contact with Jewish scholarship. For this purposeShlomo Havlin could well serve as a role model. He is currently at the height of hiscreative powers and we all hope that with God’s help he will be granted many moreyears of creative activity.

Cyril DombDepartment of Physics;

Bar-Ilan University;Ramat-Gan 52900; Israel

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References

[1] L. Van Hove, in: R.G. Mills, E. Ascher, R.I. Ja-ee (Eds.), Critical phenomena in alloys, magnets andsuperconductors, McGraw-Hill, New York, 1971, p. xxv.

[2] J.M. Ziman, Phys. Bull. 25 (1974) 280.