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RESEARCH
PARTICLE PHYSICS
Particle physics is the science which identifies nature’s
constituents and interactions at the most fundamental level,
with an emphasis on comparing theoretical ideas with both
terrestrial experiments and astrophysical observations. This mandate
gives it a strong overlap with string theory, quantum gravity, and cosmology.
Particle physicists at Perimeter are currently involved in identifying how
cosmological observations and experiments at terrestrial accelerators and
underground laboratories constrain the theoretical possibilities for physics
beyond the Standard Model.
WHY
DOES
DARK
ENERGY
DOMINATE
OUR
UNIVERSE
?
There is clear evidence that our universe is expanding faster and faster. Scientists don’t know
why. The theory of general relativity can only account for it if there is something in the universe that
has bizarre properties, such as negative pressure. For want of a better name, this something is
known as “dark energy.” But the Standard Model of particle physics can’t account for dark energy.
Yet there is more dark energy in the universe than anything else. We appear to be entering what
scientists call “a new epoch of dark-energy domination.”
Now, Associate Faculty member Cliff Burgess and his student Leo van Nierop may have
unravelled this enigma, which has long vexed both the cosmologists who observe the accelerated
expansion and the particle physicists working to explain it.
The researchers began with ideas taken from string theory which predict two things: the existence
of more than the standard three spatial dimensions and the existence of multi-dimensional surfaces
called “branes,” on which elementary particles might be trapped. Building on these models, the
researchers developed the first systematic tools that show how branes that span any number of
spatial dimensions curve their environment. These new tools show how the extra dimension can
curve in a way that looks like dark energy. This not only might explain the current accelerated
expansion of the universe, but also another period of accelerated expansion that is believed to have
happened in the very early universe – the epoch of cosmic inflation.
CAN
PERIMETER
PHYSICISTS
BRIDGE
THE
WORLDS
OF
THEORY
AND
EXPERIMENT
?
Physics advances through the interplay of theory and experiment – theorists’ ideas spark new
forms of experimentation and experimentalists’ data lead to new theoretical models. Despite
this symbiotic relationship, few physicists straddle the worlds of experiment and theory. Faculty
members Philip Schuster and Natalia Toro are rare exceptions.