Bruno Buchberger and the world of Gröbner bases

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Journal of Symbolic Computation 46 (2011) 495–497 Contents lists available at ScienceDirect Journal of Symbolic Computation journal homepage: www.elsevier.com/locate/jsc Foreword Bruno Buchberger and the world of Gröbner bases In 1965, Bruno Buchberger submitted his remarkable dissertation (Buchberger, 1965) at the University of Innsbruck in Austria. Given the stature now accorded to the work, it was met initially with a curious absence of fanfare. In fact, Buchberger had completely solved the problem given to him by his advisor Wolfgang Gröbner (1899–1980), namely to build An algorithm for finding the basis elements of the residue class ring of a zero-dimensional polynomial ideal (German title ‘‘Ein Algorithmus zum Auffinden der Basiselemente des Restklassenringes nach einem nulldimensionalen Polynomideal’’), and he coined the term ‘‘Gröbner bases’’ in Buchberger (1976) as a tribute to his mentor. At that time only few mathematicians were interested in the algorithmic solution of algebraic problems, and the dawning field of computer science did not feel a strong need for deeper algebra. Despite its modest title, the algorithm presented in Buchberger’s thesis (now duly referred to as ‘‘Buchberger’s algorithm’’) is actually developed for ideals of any dimension. In addition to the standard ingredients of Gröbner bases theory (e.g. the leading term ideal, S-polynomials, uniqueness properties, ideal membership), first applications in algebraic geometry become visible: characterizing nontrivial and zero-dimensional ideals, computation of Hilbert functions, and deriving the multiplication table for the residue class ring. The thesis is available in an English translation in the JSC Special Issue (Buchberger, 2006); the interested reader is strongly advised to read Buchberger’s own comments in the editorial of Buchberger (2006). It should also be emphasized that the original algorithm was implemented on the university’s state-of-the-art machine, a ZUSE Z23, complete with examples successfully computed by the implementation. The original magnetic drum of the Z23 can now be seen in a showcase at the Kepler university. The article (Buchberger, 1970), translated into English in Buchberger (1998), is usually regarded as the journal version of Buchberger’s dissertation. It also put forth some important extensions now considered basic to Gröbner bases theory: the characterization by a confluent reduction relation, a termination proof equivalent to Dickson’s lemma, the triangularization of polynomial systems using lexicographic term orders. The latter is achieved by a change of basis from a graded ordering, an idea that was later elaborated into FGLM and the Gröbner walk. The period 1965–75 appears, by and large, as a ‘‘lost time’’ for Gröbner bases as Buchberger, presumably discouraged by the lack of interest in his results, turned to mathematical logic. One important result that he achieved in this field is a characterization of all possible input, transition and output functions of Gödel numberings. On the face of it, this is entirely unrelated to Gröbner bases, but we will see below that the engagement in logic has also borne good fruit for the latter. In fact, Bruno Buchberger always emphasizes the organic unity and inter-fertilization of mathematics, logic, and computer science (Hong et al., 2006; Hong, 2006). The comeback of Gröbner bases started around 1975 when Buchberger heard some influential mathematicians propose a new candidate for the blacklist of important undecidable problems in mathematics: checking the solvability of a polynomial system. With due respect, he said, I believe that I already have an algorithm for deciding just that and even more! He was soon approached 0747-7171/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jsc.2010.10.001

Transcript of Bruno Buchberger and the world of Gröbner bases

Page 1: Bruno Buchberger and the world of Gröbner bases

Journal of Symbolic Computation 46 (2011) 495–497

Contents lists available at ScienceDirect

Journal of Symbolic Computation

journal homepage: www.elsevier.com/locate/jsc

Foreword

Bruno Buchberger and the world of Gröbner bases

In 1965, Bruno Buchberger submitted his remarkable dissertation (Buchberger, 1965) at theUniversity of Innsbruck in Austria. Given the stature now accorded to the work, it was met initiallywith a curious absence of fanfare. In fact, Buchberger had completely solved the problem givento him by his advisor Wolfgang Gröbner (1899–1980), namely to build An algorithm for findingthe basis elements of the residue class ring of a zero-dimensional polynomial ideal (German title ‘‘EinAlgorithmus zum Auffinden der Basiselemente des Restklassenringes nach einem nulldimensionalenPolynomideal’’), and he coined the term ‘‘Gröbner bases’’ in Buchberger (1976) as a tribute to hismentor. At that time only fewmathematicianswere interested in the algorithmic solution of algebraicproblems, and the dawning field of computer science did not feel a strong need for deeper algebra.

Despite its modest title, the algorithm presented in Buchberger’s thesis (now duly referredto as ‘‘Buchberger’s algorithm’’) is actually developed for ideals of any dimension. In additionto the standard ingredients of Gröbner bases theory (e.g. the leading term ideal, S-polynomials,uniqueness properties, ideal membership), first applications in algebraic geometry become visible:characterizing nontrivial and zero-dimensional ideals, computation of Hilbert functions, and derivingthemultiplication table for the residue class ring. The thesis is available in an English translation in theJSC Special Issue (Buchberger, 2006); the interested reader is strongly advised to read Buchberger’sown comments in the editorial of Buchberger (2006). It should also be emphasized that the originalalgorithm was implemented on the university’s state-of-the-art machine, a ZUSE Z23, complete withexamples successfully computed by the implementation. The original magnetic drum of the Z23 cannow be seen in a showcase at the Kepler university.

The article (Buchberger, 1970), translated into English in Buchberger (1998), is usually regardedas the journal version of Buchberger’s dissertation. It also put forth some important extensions nowconsidered basic to Gröbner bases theory: the characterization by a confluent reduction relation, atermination proof equivalent to Dickson’s lemma, the triangularization of polynomial systems usinglexicographic term orders. The latter is achieved by a change of basis from a graded ordering, an ideathat was later elaborated into FGLM and the Gröbner walk.

The period 1965–75 appears, by and large, as a ‘‘lost time’’ for Gröbner bases as Buchberger,presumably discouraged by the lack of interest in his results, turned to mathematical logic. Oneimportant result that he achieved in this field is a characterization of all possible input, transition andoutput functions of Gödel numberings. On the face of it, this is entirely unrelated to Gröbner bases,but we will see below that the engagement in logic has also borne good fruit for the latter. In fact,Bruno Buchberger always emphasizes the organic unity and inter-fertilization of mathematics, logic,and computer science (Hong et al., 2006; Hong, 2006).

The comeback of Gröbner bases started around 1975 when Buchberger heard some influentialmathematicians propose a new candidate for the blacklist of important undecidable problems inmathematics: checking the solvability of a polynomial system. With due respect, he said, I believethat I already have an algorithm for deciding just that and even more! He was soon approached

0747-7171/$ – see front matter© 2010 Elsevier Ltd. All rights reserved.doi:10.1016/j.jsc.2010.10.001

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by Rüdiger Loos, who encouraged him to publish his findings in the SIGSAM Bulletin (now renamedCommunications in Computer Algebra). The contact with Loos proved to be productive also in lateryears. Many readers will know their remarkable monograph Computer Algebra: Symbolic and AlgebraicComputation, co-edited with George Collins.

Since our focus is on Gröbner bases, we skip such important events as Buchberger’s founding ofthe Research Institute for Symbolic Computation (RISC), the Hagenberg Softwarepark (SWP), and eventhe Journal of Symbolic Computation (JSC). We jump forward to our junction, the 1998 Conference 33Years of Gröbner Bases, organized by Bruno Buchberger and FranzWinkler in Hagenberg, just a third ofa century after Gröbner bases were born. This conference brought together many leading experts onGröbner bases theory, by this time a vast research areawith an impressive spectrum of applications infields as diverse as commutative algebra, symbolic analysis and cryptography. The neat proceedingsvolume (Buchberger, 1998) is worth reading even now, a decade later.

But research in Gröbner bases was continuously expanding (Hong, 2000). The next major eventin the Gröbner bases community was conducted at a substantially larger scale, at the SpecialSemester on Gröbner Bases and Related Methods in 2006. Jointly organized by Bruno Buchbergeron behalf of RISC and by Heinz W. Engl on behalf of RICAM (Radon Institute for Computational andApplied Mathematics), this semester was truly special in its impact on the research community, inspreading creative ideas and fostering collaborations. This has led to, besides multiple proceedingsand numerous joint publications, a comprehensive online Gröbner Bases Bibliography (Gröbner BasesBibliography Project, 0000).

Any account of Buchberger’s struggle with Gröbner bases would be incomplete withoutmentioning another victory, not in Gröbner bases theory itself but on its metalevel. Many readersknow that Buchberger came back tomathematical logic in the 1990swhen he founded the TH∃OREM∀

project, an endeavor to create an integrated environment for inventing and verifying theorems aswellas algorithms. Fewer know that his return to logic was once again driven by Gröbner bases—by thegrand vision of an ideal textbook on the subject! In this book all the theorems would be formalizedand verified, the simpler proofs automatically generated, and the algorithms implemented within thesame formal framework. This endeavor is still under way; some terrain has been conquered but thebuilding of a formal database for Gröbner bases is bound to be a long battle.

And how about the invention part of this TH∃OREM∀ project? It may sound incredible at first that,cum grano salis, the Buchberger algorithmhas nowbeen synthesized by ameta-algorithm—whichwasinvented by Bruno Buchberger himself in 2004! In his own words, ‘‘it took me nearly forty years toreplace myself by an algorithm. . . ’’. The idea behind his synthesis method is to launch a prover on theproblem specification, extracting a suitable algorithm scheme from a scheme library. In the case of theBuchberger algorithm, one chooses the generic critical-pair/completion scheme, which also containsthe Knuth–Bendix algorithm and Robinson’s resolution procedure.

We finally come to the very cause of this Special Issue—the session Gröbner Bases and theirApplications, organized by the editors at the 2008 Conference on Applications of Computer Algebra(ACA’08). This session was distinguished in at least two ways: Being an annual conference, ACA hastaken place in various towns all over the globe since 1995. It was hosted by Hagenberg in 2008, as itwas already in 1996, at the dawn of ACA. But over and above that, it was a special privilege for us tohave Bruno Buchberger as an honorary session chairman. OnMay 13 of the same year, Buchberger hadbeen awarded the 2007 ACM Paris Kanellakis Theory and Practice Award, a well-deserved distinctionthat we have commemorated with a video streaming presented at the opening of the session.

It remains to say a few words about the contents of this Special Issue, whose bulk consists ofpolished and refereed versions of lectures given at the aforesaid ACA’08 session. We have received 15submissions, fromwhich 10were accepted, some after several extensive rounds of revision. The topicsspan applications of Gröbner bases (or related standard bases) in traditional areas like optimization(Blanco, Puerto), cryptography (Caboara, Caruso, Traverso), and singularity theory (Frühbis-Krüger)as well as in novel fields like origami (Ida, Kasem, Ghourabi, Takahashi), Boolean Gröbner basesand Sudoku (Sato, Inoue, Suzuki, Nabeshima, Sakai), and concurrency model checking (Kalorkoti).Crucial efficiency issues of the Buchberger algorithm are treated in the context of saturation (Bigatti,Caboara, Robbiano). In the noncommutative world, one paper is devoted to the efficient computationof Jacobson forms (Schindelar, Levandovskyy). Explicit Gröbner bases are constructed for the effective

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handling of polynomial functions over modular rings (Greuel, Seelisch, Wienand). Last but not least, anovel suite of explicit examples is provided as a tangible illustration of non-Cohen–Macaulay factorialdomains (Marcelo, Schenzel).

Besides attesting to the undiminished vitality of Gröbner bases theory, this Special Issue is alsointended as a resounding THANK YOU from the symbolic computation community for creating sucha wonderful mathematical world, rich in structural beauty and powerful in applications. We are verypleased to dedicate this Special Issue to Bruno Buchberger.

References

Buchberger, Bruno, 1965. Ein Algorithmus zumAuffinden der Basiselemente des Restklassenringes nach einem nulldimension-alen Polynomideal. Ph.D. Thesis, University of Innsbruck. English translation in Buchberger (2006).

Buchberger, Bruno, 1970. Ein algorithmisches Kriterium für die Lösbarkeit eines algebraischenGleichungssystems. AequationesMath. 4, 374–383. English translation: An algorithmical criterion for the solvability of a system of algebraic equations, inBuchberger (1998).

Buchberger, Bruno, 1976. A theoretical basis for the reduction of polynomials to canonical forms. ACM SIGSAM Bull. 10 (3),19–29.

Buchberger, Bruno, 2006. Bruno Buchberger’s PhD thesis 1965: an algorithm for finding the basis elements of the residue classring of a zero dimensional polynomial ideal. J. Symbolic Comput. 41 (3–4), 475–511. Translated from the 1965 Germanoriginal by Michael P. Abramson.

Buchberger, Bruno,Winkler, Franz (Eds.), 1998. Gröbner Bases and Applications. In: LondonMathematical Society Lecture NoteSeries, vol. 251. Cambridge University Press, Cambridge.

Gröbner Bases Bibliography Project. See http://www.ricam.oeaw.ac.at/Groebner-Bases-Bibliography.Hong, Hoon, Kapur, Deepak, Paule, Peter, Winkler, Franz, 2006. Bruno Buchberger—a life devoted to symbolic computation. J.

Symbolic Comput. 41 (3–4), 255–258.Kapur, Deepak (Ed.), 2006. Logic, mathematics and computer science: interactions in honor of Bruno Buchberger (60th

birthday). J. Symbolic Comput. 41 (3–4).Tran, Quoc-Nam (Ed.), 2000. Applications of the Gröbner basis method. J. Symbolic Comput. 30 (4) (special issue).

Guest EditorElizabeth Arnold

Department of Mathematics and Statistics,James Madison University, Harrisonburg,

VA 22807, United StatesE-mail address: [email protected].

Guest EditorIlias Kotsireas1

Department of Physics and Computer Science,Wilfrid Laurier University,

75 University Avenue West, Waterloo,Ontario N2L 3C5, Canada

E-mail address: [email protected].

Guest EditorMarkus Rosenkranz

School of Mathematics, Statistics and Actuarial Science,University of Kent, Canterbury,Kent CT2 7NZ, United Kingdom

E-mail address:[email protected].

30 September 2010Available online 13 October 2010

1 Tel.: +1 519 884 0710x2218; fax: +1 519 746 0677.