Quantum Fields, Quantum Gravity and Quantum Particles

The STFC research programme of the Theoretical High Energy Physics Group at
Cambridge University is focused on the fundamental problems of collider
phenomenology, quantum field theory and quantum gravity, and analysing a
class of strongly interacting particles called hadrons.

In this research, we
shall perform calculations to understand the fundamentals underlying
reality and our understanding of the universe and matter within it.
Much of this effort supports particle physics experiments at CERN and
elsewhere, as well as astrophysical and cosmological observations of the
universe.

Technical, difficult, and detailed calculations deep in quantum theory are
required in order to interpret some of the experimental data and to learn
everything we can from them. The structure of the proton (the particles
that collided at the Large Hadron Collider) will be understood better in order to get
robust and reliable predictions on the collisions. We are analysing
and interpreting Large Hadron Collider data from CERN to do
various things: looking for signs of new particles or forces, developing
search and measurement strategies for them, or making high precision
predictions of various theories. The Standard Model is the current model of
particle physics that is well accepted, verified, and measured. Most of its
predictions agree well with collider data. However, it leaves many questions
unanswered: why do the fundamental particles have the particular pattern they
do in their masses? We shall be developing mathematical models, based on
current data, to try to explain some such features, and provide experimental
tests at the same time. We are also busy supporting the science case for future
colliders, investigating which questions they could answer well.

How gravity behaves at small distance scales is badly understood
theoretically, although string theory may be an interesting framework for
understanding it.
We will be developing and investigating theories of quantum
gravity mathematically in order to push the understanding forward.
Black
holes provide a particular focus for the calculations: these are objects
around which gravity is very strong, and we will learn much from their
theoretical study. Various
calculations in new developments of string theory are important for this, and
for the development of how to calculate particle scattering in general.
String theories will be constructed to see how close they come to the universe
we see. Also, models of inflation (a time in the early universe when the
universe underwent extremely rapid expansion) will be investigated, developed, and compared with observations.

Some particles, such as hadrons, are strongly bound states of smaller
ones. For these, sophisticated computer programs are built which break
space and time up into a grid of points, and the quantum
fluctuations of the sub-nuclear interactions are simulated using random
numbers on this lattice. Analytic calculations must be done to match the
numbers obtained on the computer to experimental data. We shall develop
these calculations, and perform new ones so that data can be used to
extract the level to which various quarks (for example, the up quark and
the b-quark) mix. This helps provide an accurate description of an
unexplained phenomenon: how the funny pattern of quark mixing comes
about. These calculations also help the extraction of the difference
between matter and anti-matter from experimental data. We can predict
much about which strongly bound states may exist and their properties,
and studies of the more exotic and puzzling varieties seen in experiments
will be an important avenue of work.