Brian Dolan
Particle physics and cosmology answer fundamental questions about the very stuff that our Universe is made of and where it comes from -- including such fascinating ideas as Black Holes and quarks, the Big Bang and the very early Universe. Many of the techniques necessary for the study of particle physics and cosmology have applications in other areas of physics as well, such as condensed matter and solid state physics.In particle physics we study both the basic building blocks of the matter in our Universe -- electrons and quarks -- and the forces between them. In the 100 years since Becquerel discovered natural radioactivity we have been gathering information about the structure of atoms, but it is only in the last 25 years that a coherent picture has emerged which can explain it. This picture unifies three of the four fundamental forces of Nature: electro-magnetism which is responsible for all optical phenomena such as rainbows, sunsets and the aurora Borealis; the weak nuclear force, which keeps the sun shining; and the strong nuclear force which binds protons and neutrons together inside atomic nuclei, and quarks inside protons and neutrons. However, Einstein's dream of unification with the fourth force, gravity, still eludes us.
The mathematics that underlies the unification of the first three forces marries two of the most far reaching theoretical developments of twentieth century physics -- Einstein's special theory of relativity and the theory of quantum mechanics -- into a single theory we call relativistic quantum field theory. Relativistic quantum field theory and its application to particle physics, as well as what it can teach us about other areas of physics, are my main research interests.
Surprisingly, relativistic quantum field theory predicts that the electric charge of an electron is not really a constant but depends on the energy at which it is measured -- it increases at higher energies. For example electrons accelerated to high energies available in the large particle accelerator at CERN in Geneva, have a charge which is 7% higher than in an ordinary television tube. This dependence of physical quantities on energy is a universal feature of particle physics and has parallels in the theory of semi-conductors and ferro-magnets -- and it has been one of my principle areas of interest in recent years.
Another key ingredient in our search for unification is symmetry. An idea that is very popular at the moment is to go even further in the unification process with what we call super-symmetry. There are two types of particles in Nature: electrons and quarks, which make up the matter of our Universe; and particles which cause the forces between them, photons for the electro-magnetic force and gluons for the strong force. Super-symmetry aims at removing this distinction between matter' particles and force, particles, so that there is only one type of stuff' in our Universe.
Super-symmetric models of particle physics have remarkable parallels with the quantum Hall effect -- a phenomenon in semi-conductor physics that occurs at very low temperatures and high magnetic fields. The discovery of the quantum Hall effect has twice won the Nobel prize for physics -- once in 1985 and again in 1998. The connection between super-symmetric particle physics and the quantum Hall effect is in how they react to changing energy scales, something that I am actively investigating at the moment.
The final force, gravity, is a fascinating subject in its own right. Our modern understanding of this force comes from Einstein's general theory of relativity which describes gravity in terms of geometry and the curvature of space and time. The amazing consequences of Einstein's vision include Black Holes and the Big Bang theory of the early Universe, where matter experiences extremes of temperature and pressure, at very high energies. Here again relativistic quantum field theory is an invaluable tool and the physics of Black Holes and the early Universe are among my other research interests.
Click here to find out how the strong nuclear force (quantum chromo-dynamics) is related to the quantum Hall effect.
More technical details about my research here
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