Page 22 - 2012-01-20

This is a SEO version of 2012-01-20. Click here to view full version

« Previous Page Table of Contents Next Page »
String theory is a theoretical framework aimed at
producing a unified description of all particles and forces
in nature. It is based on the idea that at very short distances, all
particles should be seen as one-dimensional objects or “strings.” String
theory has strong connections to other research areas, including quantum
gravity, particle physics, and cosmology, as well as mathematics. Notably,
members of the string research area at Perimeter are leading the world in the
cutting-edge area of advanced field theory methods.
To find out what’s inside a piñata, one makes it collide with a stick. In a similar vein, to reveal the
basic building blocks of matter, particle accelerators like the Large Hadron Collider (LHC) smash
subatomic particles together at very high speeds. With the piñata, the stick does not produce
any candy that was not there already; by contrast, particles in an accelerator collide, bounce off
each other, and emit or absorb additional new particles in a process called scattering.
As the most powerful particle accelerator on the planet, the LHC is the focal point for physicists
around the world. Many feel that it will bring breakthroughs in our understanding of the universe’s
first moments, as well as what matter is made of, and even why matter exists at all.
In order to answer such questions, particle theorists need to be able to precisely calculate what
our current theories predict about what should be seen, which experimentalists check against the
actual data from high energy particle collisions. “Scattering amplitudes” are precise theoretical
predictions about the probabilities for obtaining various outgoing particles when a given set of
incoming particles collide.
When experimental results conform to theorists’ predictions, that’s good. But when something
unexpected happens instead, that’s even better – it means scientists have discovered something
new about physics.
While traditional methods for calculating predictions for simple processes of a few particles
bouncing off one another are fairly straightforward, they are hopelessly complex for describing
processes with a great morass of particles all crashing together at once. Yet this is exactly the
situation at the LHC. Thus, over the past several years, theorists have been pushing hard to
develop a range of techniques aimed at better understanding both how to compute scattering
amplitudes and what they actually tell us.
In the past year, Perimeter scientists have made great strides in this quest.