Foreword Bob Kalaba: Teacher, Colleague, and Friend

John L. Casti

Institute for Econometrics, OR&System Theory

Technical University of Vienna A-l 040 Vienna, Austria

One of the few perks of editing a journal is the opportunity to pull editorial rank and insert your own prejudicial remarks at the beginning of special issues like this one. And of all the special issues that Applied

Mathematics and Computation will ever publish under my stewardship, this one, dedicated to Bob Kalaba on the occasion of his 65th birthday, is where the exercise of that editorial prerogative will give me the greatest pleasure. To begin with, Bob was the founding editor of this journal. And as Bob’s successor in the editorial chair, I have been the direct beneficiary over the past ten years of the herculean efforts on his part that resulted in the establishment of AMC as one of the most successful journals in the applied mathematical area. These efforts by Bob have made my job vastly easier than I had any right to expect. But this is only a secondary and somewhat selfish reason underlying my enthusiasm for putting these testimonial words down in print. The main reason is the dominant influence that Bob had on both my personal and professional development long before there ever was such a thing as this journal. To recount that story, let me turn back the calendar a quarter of a century or so.

In June 1967 I arrived in Santa Monica from Portland, Oregon to take up a position as a programmer at The RAND Corporation, a job that I must confess I took on primarily as a means to finance simultaneously a family and the pursuit of a doctoral degree in mathematics at USC with Dick Bellman. One day shortly after my arrival at RAND, I was discussing my course plans for the autumn with Dick in the hallway outside his RAND office. Suddenly, Dick stopped my graduate-student meanderings in midstream, saying, “Here comes someone I want you to meet.” The course of a person’s life can and often does turn on such casual, seemingly random encounters. And so it was for me that midsummer day, as this initial meeting with Bob Kalaba set the course of much of my professional life for many years thereafter.

During that initial conversation, Bob and I agreed with Dick’s suggestion that by doing some RAND work jointly with Bob, I might acquire a bit of semi-real-world polish to complement my formal academic studies at USC.

APPLIED MATHEMATICS AND COMPUTATZON 45:85-88 (1991)

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And so began a collaborative undertaking that was to not only dramatically shorten my graduate-student career, but also produce one book and more than two dozen published research articles. But these written records of my work with Bob represent only the tip of the iceberg insofar as what I learned from him about the process of applied mathematical research, in particular, and intellectual activity, in general. Perhaps the best way to convey the flavor of what I learned and how I learned it is for me to describe how a typical day at BAND would go if one were operating in “ Kalaba-collaborative mode.”

A normal day would go something like this. Based on the previous day’s discussions, a computation of some sort would usually have been called for, a chore that I would write the program for in the late afternoon and leave for overnight processing at the BAND Computer Center. Upon arriving at work the next morning, the first item on my agenda would be to retrieve the output from the Computer Center and check to see how the calculations came out. Then around half past nine or so Bob would call and ask me if the program ran (often it didn’t) and how the results looked. Following some discussion along these lines, we would agree to meet later in the morning in one of the BAND conference rooms, which were the only rooms in the building with blackboards large enough to contain all the speculations and scribblings that were a regular concomitant to our deliberations. At the meeting itself, Bob would usually introduce some new ideas he had dreamt up overnight about how to deal with the problem at hand. This might consist of a novel way to compute the solution to a nonlinear two-point BVP, an unconventional scheme to calculate the solar radiation transmitted through the Earth’s atmosphere, or even some new theoretical approach to the solution of an inverse problem, e.g., a method for deducing the characteris- tics of an optical medium on the basis of observations of light rays passing through the medium. Whatever the problem, we would toss the difficulties around for an hour or so, often with the collaborative help of whoever else happened to be in residence at BAND at the time. Generally the morning meeting would adjourn with an agreement to think some more about the problem and meet for further discussions after lunch. The afternoon meeting would in most respects mirror its morning counterpart-with the notable exception that it usually ended with a proposal by one of us for some sort of computation that could be performed to check and/or validate the day’s speculations. And so went the daily cycle-at least while we were in the research mode-with obvious modifications when we reached the stage where it was time to actually write up our results for publication.

This “plan of the day,” from which we seldom deviated during the four years that I collaborated actively with Bob, is about the best way I can think of for a young researcher to get his or her feet wet in the business of doing research, involving as it does a relentless, intense, single-minded attack on a

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specific problem, a collaborative undertaking in which all parties to the effort participate on an equal footing. In fact, it still amazes me today to think how readily Bob accepted me as a colleague from the moment we first met. And this despite his having had no information whatsoever about me or my scientific credentials other than a few casual words of support from Dick Bellman and my assurances that I was eager to do some joint work. But Bob’s generosity to young researchers is by now the stuff of legends among his many past and present students and collaborators, representing one of the many qualities that makes him such a wonderful teacher. And, in fact, I was to benefit twice over from this generosity when Bob later served as one of the examiners on my doctoral committee, following his departure from RAND to a professorship at USC.

An important side benefit arising out of working with Bob in the above fashion is the chance to meet a lot of people that Bob is in contact with. Just to list a few of the people that I met directly through Bob, let me mention Harriet Kagiwada, Sueo Ueno, Tom Kailath, Melvin Scott, Sid Sridhar, Krishna Murthy, Mike Golberg, and Ron Huss. And this is above and beyond the many other friends, collaborators, and colleagues, like Ed Angel, Bob Larson, Mario Juncosa, Alan Schumitzky, Chris Shoemaker, Alex Letov, and Roger Jeliffe, that I met indirectly through Bob and/or Dick Bellman. Again, these invaluable personal and professional relationships were established as a direct consequence of Bob’s collegial nature and willingness, eagerness even, to share his own intellectual contacts with his students and collaborators.

But as with all golden ages of intellectual innocence, mine was an evanescent and short-lived one, lasting a brief four years. By the early 1970s the environment at RAND was far from congenial for purely academic dreaming, a fact that precipitated Bob’s departure for USC, while I had by then completed my degree and left RAND for other pastures, both domestic and foreign. Constraints of both time and distance now preclude contact with Bob on as regular a basis as I would like. Nevertheless, I still occasionally receive one of those wonderfully compact Kalaba letters, which by empirical observation appear to be rigidly constrained to a length of at most three (short) sentences. Usually these missives are of a dynamic, uplifting tone, conveying a message of the sort that I’m always happy to receive, e.g., a gleeful account of a stirring USC football triumph over Notre Dame (an all too rare event in recent years) or, perhaps, an overly generous pat on the back upon publication of one of my books. And whenever one of these dispatches from the front arrives, my thoughts invariably turn back to those RAND days when Bob showed me by example rather than precept what a thrilling adventure it must be to be a scientist. While I’m pretty sure by now that I’ll never match up to the high scientific and personal standards set by Bob, his model continues to be a source of inspiration for me to this day.

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Hopefully, the papers of this special issue will convey just a small part of the flavor of those standards to the broader community of scholars who have not had the great privilege of working with Bob personally. So let me now turn the floor over to Leigh Tesfatsion, the guest editor of this special issue, for a more systematic account of Bob’s many contributions to scientific and intel- lectual life.