University of Minnesota
School of Physics & Astronomy


The light elements

Keith Olive
Keith Olive
Wendy Tschampl

Professor Keith Olive’s research provides a unique probe into the very early history of the Universe. Olive is a theorist who specializes in high energy particle physics and cosmology. “High Energy” particles are those produced in high-energy situations such as accelerators or the Big Bang.

The light elements, deuterium, helium and lithium, were produced shortly after the
big bang. When the age of the Universe was about a minute old, conditions
were such that the density and temperature of the Universe was favorable for
nuclear reactions involving neutrons and protons to occur, much like the interior
of the sun. At this time, the temperature of the Universe was about a billion degrees K. To grasp this temperature, the corona of the sun is merely millions of degrees K.
At this stage, the Universe had a density throughout of about a 1 gram per cubic centimeter—the same density as water. Unlike the sun, the Universe expanded and cooled so that nucleosynthesis occurs only very briefly during first few minutes. Today, the Universe is at a temperature of only 2.7 degrees K and has a density of only one proton per ten cubic meters.

Theory predicts the abundances of these elements which are subsequently compared with observations. Overall the agreement between theory and observations is quite good, particularly for deuterium and helium. However the success of what is termed the standard model (of both cosmology and particle physics) was never guaranteed. Any non-standard processes which may have occurred could have had consequences for big bang nucleosynthesis and the predicted light element abundances. Olive’s research uses the success of the standard model to place constraints on any deviation from the standard model. For example, the number of new particle species present in the early universe is
constrained. Models which predict the variation of the fundamental constants including Newton's constant are also constrained.

All of the deuterium in the Universe, almost all of the helium and some of the lithium Olive observed were formed in the big bang. As a consequence, the study of the light elements offers a unique probe into the very early history of the Universe.