# Quantum Fields, Quantum Gravity and Quantum Particles

Lead Research Organisation:
University of Cambridge

Department Name: Applied Maths and Theoretical Physics

### Abstract

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.

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.