John Collins

John Collins

Distinguished Professor Emeritus of Physics (at the Physics Department of Penn State University)
Ph.D., University of Cambridge, 1975
Mailing address: 104 Davey Lab. #208, Penn State University, University Park PA 16802, U.S.A.

Elementary Particles and Fields

Perturbative Quantum Chromodynamics

Prof. Collins' research is predominantly in the theory of the strong interactions of elementary particles, but with occasional excursions into other areas. (One particular case is the investigation of observations of cosmic rays from X-ray binary stars. These extraordinary objects behave like particle accelerators of energies much beyond those available on earth. Observations can shed new light both on elementary particle physics and on stellar physics.)

The theory of the strong nuclear interaction is quantum chromodynamics (QCD). Protons and other strongly interacting particles are bound states of quarks held together by what is called a "gluon field". A key property of QCD is "asymptotic freedom". This means that on long distance scales the interaction is strong, so that quarks are permanently confined, but that on shorter distance scales the interaction becomes progressively weaker. In principle, QCD should be able to predict the properties of atomic nuclei from first principles, but, in practice, this is very difficult because one has to treat strong coupling, relativistic many-body dynamics.

In the twenty years since the discovery of QCD, substantial progress has nevertheless been made in understanding the consequences of the theory. Much of the progress has been concerned with phenomena that occur on distance scales smaller than the size of a proton, for there one can try to exploit the weakness of the interactions that is a consequence of asymptotic freedom. Prof. Collins has played an important role in this work.

Originally, calculations in QCD were possible only for a few exotic processes. As experiments on elementary particle collisions have progressed to higher and higher energies, the products of the collisions have become more complex, but at the same time they probe shorter distances. The quantitative predictions that can now be made from first principles, for a wide range of processes, are in substantial agreement with experiment. In obtaining these predictions, Prof. Collins and many others have discovered interesting mathematical properties of the theory. Only with the aid of these results, can one interpret experimental data from modern high energy particle accelerators.

The result is that these accelerators can now be used in effect as microscopes which probe fundamental physics at distance scales that are now of the order of a hundredth or a thousandth of the size of a proton. One aim of current research in elementary particle physics is to discover what lies inside the many known "elementary" particles, and what causes them to have the properties that they have. In these investigations, the results of QCD calculations play a critical role.

Prof. Collins is an emeritus member of the CTEQ Collaboration, which is a collaboration of experimentalists and theorists at many universities and laboratories who work on QCD.

Systems neuroscience

Commonly it has been supposed that the coding by neuronal firing for the various percepts recognized by a brain is in complex distributed patterns of firing. However, in recent years it has increasingly been found that there are also neurons that respond very simply, in a wide variety of organisms from birds to primates, both non-human and human. For example, there are neurons that fire exactly at one moment in the song of a zebra finch, and there are neurons that fire when a human sees an image of one particular person. We aim at understanding the algorithms in which these neurons participate, and to relate these to the properties of individual neurons. How do neurons create the complex sequences in birdsong? How are memories formed? How are they represented? Possible algorithms are highly constrained in order that large amounts of information can be processed and stored without running out of space.


Research Articles

See my publications in the INSPIRE database for a fairly accurate list of my publications in elementary particle physics.

Selected publications:


I have developed a number of programs and other software, notably latexmk.

Scottish Country Dancing and music

One of my pastimes is Scottish country dancing. For some of my musical activities, see also Strath Hanna for my band, and David Rosenbaum at 60 for a tune I've composed.
John Collins,, 12 November 2023.