Guido Altarelli’s legacy

“From my vast repertoire …” is a rather peculiar opening to a seminar or a lecture. The late CERN theorist Guido Altarelli probably intended it ironically, but his repertoire was indeed vast, and it spanned the whole of the “famous triumph of quantum field theory,” as Sidney Coleman puts it in his classic monograph Aspects of Symmetry. There can be little doubt that a conspicuous part of this triumph must be ascribed to the depth and breadth of Altarelli’s contributions: the HERA programme at DESY, the LEP and LHC programmes at CERN, and indeed the current paradigms of the strong and electroweak interactions themselves, bear the unmistakable marks of Guido’s criticism and inspiration.

From My Vast Repertoire … is a memorial volume that encompasses the scientific and human legacies of Guido. The book consists of 18 well-assorted contributions that cover his entire scientific trajectory. His wide interests, and even his fear of an untimely death, are described with care and respect. For these reasons the efforts of the authors and  editors will be appreciated not only by his friends, collaborators and fellow practitioners in the field, but also by younger scientists, who will find a timely introduction to the current trends in particle physics, from the high-energy scales of collider physics to the low-energy frontier of the neutrino masses. The various private pictures, which include a selection from his family and friends, make the presence of Guido ubiquitous even though his personality emerges more vividly in some contributions than others. Guido’s readiness to debate the relevant physics issues of his time is one of the recurring themes of this volume; the interpretation of monojets at the SPS, precision tests of the Standard Model at LEP, the determination of the strong coupling constant, and even the notion of naturalness, are just a few examples.

While lecturing at CERN in 2005, Nobel prize-winning theorist David Gross outlined some future perspectives on physics, and warned about the risk of a progressive balkanisation. The legacy of Guido stands out among the powerful antidotes against a never-ending fission into smaller subfields. He understood which problems are ripe to study and which are not, and that is why he was able to contribute to so many conceptually different areas, as this monograph clearly shows. The lesson we must draw from Guido’s achievements and his passion for science is that fundamental physics must be inclusive and diverse. Lasting progress does not come by looking along a single line of sight, but by looking all around where there are mature phenomena to be scrutinised at the appropriate moment.