1.Small scale structure on cosmic strings in anisotropic backgrounds

peaceshiveringAI and Robotics

Oct 24, 2013 (4 years and 7 months ago)


Prof Mairi Sakellariadou


Small scale structure on cosmic strings in anisotropic backgrounds

We will investigate the effect of an anisotropic background (Kasner

type for instance) on the evolution of
a cosmic string network. In particular, we will first study whether a scaling regime can be reached and
then, considering small perturbations on the strings, we will investigate observational consequences, for
ce the effect on gravitational lensing.

Research Category


Prof. Lev Kantorovich

Room S7.25

Equilibrium Green’s Functions and their application to quantum conductance (TC)

In this project a student will learn a succession

of techniques from quantum field theory to quantum
statistical mechanics, including the second quantisation for electrons, a solution of the Schrodinger
equation with a time
dependent Hamiltonian, and non
equilibrium Green’s functions, in order to
r a conductance of molecular junctions. These systems have great applications in nano
electronics (e.g. nano
devices and scanning tunnelling microscopy). Several simple tight
binding toy
models will be considered and the current will be calculated as a fun
ction of the applied bias,
temperature and the electronic structure of the molecule modelled as a set of electronic energy levels
coupled to the contacts.

The project involves a lot of rather complicated mathematics, so only students who feel strong in mat
should consider it. Some of the work at a later stage would involve writing simple computer codes for
calculating the transmission function and the current
voltage characteristics. Working on this project
will give a student a chance to familiarise him/
self with some of the modern theoretical methods for
studying non
equilibrium systems.

Required skills: Strong analytical skills, ability to learn independently and some familiarity with a
computer language (C++ or Fortran).

Eugene Lim



The Sine

soliton and Backlund tranforms

You will study the sine
Gordon soliton system, and understand how its solutions can be generated by a
mathematical trick called the Backlund transform. You will study its generalizations.

Research Category

Klaus Suhling Room S7.31

Fluorescent particle uptake by worms

Fluorescence microscopy is a powerful optical imaging technique in the life and biomedical sciences,
because it is minimally invasive and al
lows the observation of living specimens. The project, in
collaboration with Stephen Sturzenbaum, Analytical & Environmental Sciences Division, Franklin
Building and Mark Green, Department of Imaging Chemistry and Biology, Division of Imaging Scien
ces &
Biomedical Engineering, St Thomas, will focus on feeding a range of fluorescent particles and dyes such
as, for example, quantum dots, fluorescent molecular rotors, nanodiamonds, gold nanoparticles to
, a non
parasitic model nematode. The w
orms will subsequently be imaged under a fluorescence
microscope to map the location and progression of the particles through the specimen. This is of
interest for toxicology studies, and also for evaluation where and how the worms process nanoparticles.

kills required: knowledge of basic image analysis software and an interest in fluorescence, microscopy
and invertebrate model systems. For more info on worms, see: www.toxicogenomics.info

Research Category: Biophysics, Fluorescence Microscopy

Dr. Klaus
Suhling Room S7.31

Photon counting Imaging

The use of a photon counting image intensifier coupled to a CCD camera is an established method to
acquire images at a low
light level. The Hubble Space Telescope’s faint object camera, and the o
monitor of the x
ray multi
mirror mission (XMM) are both based on low light level photon counting
imaging devices. Linearity, a high dynamic range, large active area and high sensitivity in the UV are
particular strengths of this technique. Photon c
ounting imaging is not restricted to astronomy, its
advantages have also recently been harnessed in fields such as autoradiography, bioluminescence and
fluorescence imaging.

One characteristic feature of this method is a centroiding technique, where the in
tensity distribution of
each individual photon event is converted into positional information. The resolution lost in the
amplification and readout stages of the detector can thereby be recovered and subpixel resolution be
obtained. An important factor to
consider in the design of a photon counting imaging system is the
choice of a suitable centroiding algorithm.

The project will focus on the optimization of software
based centroiding

algorithms, and it is envisaged
that this will be tested on biological samples under a fluorescence microscope.

Skills required: programming in C++

Research Category: Physics, Fluorescence Microscopy

Prof. Nick E. Mavromatos Room

Neutrinos and a geometrical way of generating the Matter
Antimatter Asymmetry in the

Our Universe is mostly made of matter. It had been suggested by Sakharov that this asymmetry may be
due to different decay properties (due to Charge

Parity (CP)

Violation) between particles and
antiparticles in the Early Universe, which could lead to the observed baryon (versus antibaryon)
asymmetry today. This is an out
equilibrium process in the expanding Universe termed Baryogenesis,
On the other hand, sug
gestions had been made that, at the early Universe, out
equilibrium processes
that could generate lepton versus antilepton asymmetries also take place, at an earlier stage (termed
Leptogenesis), and then they are communicated to the baryon sector by sta
ndard model processes that
conserve the quantity ``baryon
lepton’’ number. In all such processes extra (than the ones in the
Standard Model) sources of CP Violation are required in order to produce phenomenologically viable
antimatter asymmetries, a
nd hence physics beyond the standard model is needed. In this
proposal we shall examine a radical new way of thinking along these lines, without the need for such
extra CP violation, by exploring the possibility that Leptogenesis at an early (high
ure) stage of
the Universe, prior to Baryogenesis, may be induced by non
trivial geometries, either of axisymmetric
(rotating) black
hole type type, or axisymmetric Bianchi cosmology type, or geometries with torsion. In
particular, the relativistic field t
heory of Majorana (or Dirac) neutrinos in such non
trivial background
geometries will be formulated, and energy momentum dispersion relations between neutrinos and
antineutrinos will be calculated in such background space times. It will be demonstrated tha
t the
background induces differences in the dispersion relations between neutrinos and antineutrinos, which
imply different population numbers already in thermal equilibrium between neutrino matter and
antimatter. Processes in the early universe, then, tha
t violate lepton number can occur, which freeze out
at certain temperatures, leading to Leptogenesis. Some scenarios for generating phenomenologically
successful Baryogenesis in this way, without the need for extra sources of CP Violation will be briefly

The project requires advanced knowledge of: the Standard Model, Relativistic Quantum Field Theory,
General Relativity Covariant Tensor Calculus, Statistical Mechanics and Elementary knowledge of an
Expanding Universe. Students choosing this pro
ject must have taken General Relativity and Cosmology
and 3rd year Particle Physics while Maths III would also be desirable, while fourth year options on
relativistic quantum fields are desirable but not necessary.

Research Category: Particle Physics, Gen
eral Relativity, Cosmology, Relativistic Quantum Fields,
Statistical Mechanics.

Dr. Shahriar Sajjadi Room

Uniform Drops by Capillary Microfluidics

Emulsions are dispersion of one phase in another with the aid of a surfactant. Surfactants are surface
active materials that adsorb at the oil
water interface, reduce interfacial tension and as a result the
droplet size, and protect droplets against coales
cence. Emulsions are usually prepared using
homogenizers. Due to chaotic nature of flow in the dispersing zone of homogenizers, drops with a high
polydispersity are produced. Microfluidics is a technique which can deliver uniform drops. In a
microfluidic e
mulsification process, a liquid phase is pressed through a capillary to form droplets. The
aim of this research is to investigate the effects of surfactant concentration and location, and the flow
rates on the size and uniformity of droplets.
Drop uniformi
ty will be monitored by a video camera
optical microscopy.

Research Category
Condense Matter, Fluid Mechanics

Prof. Sarben Sarkar


Relativistic Quantum Information

The aim of this project is to see the effects of general r
elativity on quantum information. The latter has
been important in the study of quantum teleportation , computers and cryptography. Most analysis has
been done in the context of a flat universe however.

In this project we will consider entanglement and bla
ck hole thermodynamics, and fidelity of
transportation in accelerated frames. An important theme will the observer dependence of

Prerequisites: This project will require strong skills in quantum mechanics (quantum field theory), general
ivity and mathematical methods in physics. Issues in quantum field theory though can be addressed
during the project.

Research Category: quantum field theory, general relativity, quantum information, Unruh radiation

Dr Cedric



High temperature superconductors

In this project, the student will be introduced to theoretical quantum models of high temperature
superconductors. In particular, the focus will be on the role of strong correlations between electrons in
ese systems. Various types of numerical approaches will be discussed. As a pedagogical introduction
to strong correlations, the student will program his own code for the quantum fermionic Monte Carlo
method, based on a Suzuki
Trotter decomposition of the p
artition function (so
called Hirsch
method). Extensions of the methodology to investigate the interaction between quantum effects and
spatial disorder will be considered.

Research Category:

Numerical science; superconductors ; condensed matter physics
; Quantum Monte
Carlo; correlations; Quantum physics

Dr Patrick Mesquida


Nanopatterning of surfaces for biophysical experiments

Proteins are large biomolecules
, which adopt a very specific, 3
d conformation to carry out their
biological function in Nature. However, under certain conditions, they can “fold” into a “wrong”
conformation and aggregate. This often leads to devastating diseases such as Alzheimer’s or
Disease. Understanding what leads to mis
folding is particularly important for Western Societies wih
their ageing populations. One hypothesis is that surfaces, for example of cells, induce mis
folding. In this
project, defined test surfaces wil
l be designed and prepared in order to investigate this hypothesis.
Requirements are: Willingness to work experimentally in a lab and interest in biophysics and
biomedicine. Ideally, the student should have opted for the module “Physics of Life” in the 3rd


Requirements: £1000 for chemicals and project materials

Dr Joe Bhaseen


Path Integral Formulation of Quantum Mechanics

The Feynman path integral approach to quantum mechanics is based on a probabilistic summation over
time trajectories.
This theoretical project involves setting up the Feynman path integral
representation for a quantum system and exploring its behaviour. Possible areas for investigation
include the use of instantons in quantum tunnelling, and compa
risons with other approaches.

Prerequisites: Maths III may be useful but it is not essential.

Research Category: Quantum Mechanics, Statistical Mechanics, Mathematical Physics.

Dr Jean Alexandre
oom 7.30

Lorentz symmetry violation

in Field Theory

Relativistic invariance is one of the symmetries the most precisely checked experimentally, but if one
assumes a quantum theory of gravity for example, one can expect Lorentz symmetry to break at high
energies. This would lead to new Physi
cs, beyond the Standard Model, and could explain several
mechanisms, from Collider Physics to Cosmology.

This project deals with Classical Field Theory, and is purely theoretical, although phenomenological
implications of different Lorentz
symmetry violati
ng models will be studied.

The student choosing this project should have an excellent level in Mathematics, Electromagnetism,
Classical/Quantum/Statistical Mechanics, General Relativity.

Research Category: Mathematics, Field Theory, Special and General

Professor Anatoly Zayats Room

Controlling light with nanostructured metals

The project is devoted to experimental studies of optical properties of metallic nanostructures, such as
absorption, transmission, reflection
and photoluminescence. You will measure spectral behavior of
several types of nanostructures and determine nanostructure parameters responsible for these
properties. You will then design a nanosctructure with the spectral response required to detect the
esence of specific molecules in the nanostructure surroundings and will perform proof of principle
measurements of the sensing capabilities of the nanostructure. Prerequisites: Electromagnetism (Y2)
and Optics (Y3); Solid State Physics (Y3) is desirable.

Research Category: Optics & Photonics

Dr Nicola Bonini Room

Computer simulation of two
dimensional crystals

Following the discovery of graphene with its unique physical properties, other one
thick crystals
(e.g. MoS

or BN) have attracted great attention.

What makes these materials so special? Are there other 2D systems with amazing properties just
waiting to be discovered or synthesized?

The aim of the project is to explore the electronic and vibrational properties o
f 2D metal
dichalcogenides that, according to recent studies, could be just as impressive as graphene.

The study will be conducted via computer simulations using quantum mechanical techniques. The
student will become familiar with cutting
edge concepts in
condensed matter physics and state
art first
principles computational techniques.

Research Category: Condensed matter physics, first
principles modelling, two
dimensional crystals.

Dr. Gregory Wurtz Room S7.12

linear optical
properties measurements from plasmonic thin films metamaterials.

The project is to study the third order non
of bi
dimensional plasmonic metamaterials made
of metal
dielectric bilayers and multilayers. These systems have recently stimulated i
ncreasing interest
from the scientific community because of the breadth of physical properties they demonstrate, from
nonlocality to negative index behavior. While many fascinating aspects from these artificial materials
have yet to be discovered and expla
ined, they are already proposed in numerous applications including
superlensing and optical cloaking. Here, we propose to reveal their non
linear optical response in an
effort to design active metamaterials.

In this project the non
lineal optical properti
es of metallo
dielectric metamaterials will be characterized
using z
scan measurements. The experimental results will be rationalized using both analytical
calculations and numerical simulations.

Research Category
Optics and photonics, metamaterials, non
linear optics, z

Professor Roy Pike

Room K 1.46

Vowel Recognition by Inverse Potential Scattering.

To produce a vowel the speaker configures the articulators along the vocal tract appropriately. We have
discovered that it is only the second derivative of the vocal tract area with respect to the distance from
the glottis, (which we call the tract potenti
al function) which has a one
one correspondence with the
sound output. The governing equation is the Klein
Gordon equation in which the mass is variable and
corresponds to this potential. Furthermore, we have found that there are only six positions alo
ng the
tract where, by Ehrenfest’s principle, the physics allows perturbations of potential to make a significant
difference to the output.

The aim of the project is to work with an existing comprehensive software package developed in the
Department to ma
p spoken vowels to the potential function which produces them, and hence to be able
to recognise them first time by physical principles, rather than by comparing with large statistical data
bases as is done at present by speech engineers.

The first stage
is to reduce the sound wave output, which repeats in each glottal period, into the glottal
pulse shape and the tract
response components. This is called inverse filtering. The second stage is to
invert the latter component to obtain the potential function.

This is related to quantum
potential scattering but with our acoustic twist. Both stages are now known to be feasible and
examples exist.

The student will survey the literature in these two topics, select the best methods to implement
then to help code software procedures to implement them. These will then be applied to the vowels of
the International Phonetic Alphabet, both synthesised and naturally spoken, already within our package,
to evaluate the method.

An interest in wave pr
opagation and acoustics is desired. Skills in symbolic and high
level coding, in
Mathematica and Delphi respectively, will be developed during the course of the project.

Research Category: Speech acoustics, hyperbolic partial differential equations, finit
difference time
domain solutions.

Professor Roy Pike Room K 1.46


aperture vector diffraction theory and the optics of blu
ray compact
disc systems

Optical recording, like other data
storage technologies, is under constant press
ure from competing
technologies to increase the storage density and the data rate during recording and read out. The
project aims at increasing the storage density that can be detected with a conventional optical pick
unit by adding a specially calculat
ed, so
called singular
function mask in the light path.

We have shown that such masks, when placed either in the pupil plane or the image plane of a lens,
modify the characteristics of the optical channel to increase the effective optical bandwidth.

A sof
tware code has been written to make a complete blu
ray optical
disc player in the computer using
such masks. The student will help to perfect the idea. The work will then be applied to vary and optimise
the relevent parameters to evaluate the method.

We ha
ve long
term contacts with the members of the optical group at Philips Laboratories, Eindhoven,
on this project.

An interest in opto
mechanical systems is desired. Skills in optical diffraction theory, symbolic and high
level coding, in Mathematica and Del
phi respectively, will be developed during the course of the project.

Research Category: High
aperture optical
diffraction theory, Scanning microscopy.

Professor Roy Pike Room K 1.46


To modify and use an existing home
grown computer code

to calculate the

radiation field
from the central region of a linear dipole antenna.

After over one hundred years the “solution” of Pocklington’s equation for a linear dipole antenna is still
not completely under control and this shows up in inevitable li
mitations of the various numerical
algorithms that are used in practice. It should also be noted that the simpler problem of the distribution
of static charge on a perfectly conducting wire has also had a long and troubled history. We can cite
papers since

Maxwell himself to the present day (Jackson, 2002).The solution does not have any simple

A detailed use of Maxwell’s equations indicates that existing treatments of this important problem may
fall short of exact solutions and we will propose a cor
rection term for the current and field distributions
with some computational examples. These are integral equations which are related to Maxwell’s
equations by the theorems of Gauss and Stokes.

The student will assist with the theory and computations. Succ
essful results would be novel and highly

Research Category: Electromagnetic theory. Antenna theory and computation of radiation fields.

Professor Roy Pike Room K 1.46


invariant operators and new ideas in theoreti
cal physics.

In recent work in the department on electrical and acoustic waveguides we have uncovered a
connection with a new theoretical “bandwagon”, namely the parity
time (PT) invariant operator. This is
more general than the conventional parity
time (PCT) invariant operator of quantum mechanics
and gives rise to new ideas in various areas of theoretical physics. Among other applications, real
eigenvalues of PT
invariant matrices are relevent to non
uniform waveguides and to recent discussions
unit systems in physics.

The student will help in an investigation of these ideas and possible new experimental verifications. The
principal instigator of the new global interest in PT
invariant operators, Prof Carl Bender, of Washington
University in St.

Louis often spends time in the Department.

The student will assist with the theory and computations. Successful results would be novel and highly
publishable. He/she will work alongside a PhD student shared with UCL and Imperial College

Research Category
Theoretical Physics, Non
uniform dielectrics, Kramers
Krönig relations.

Dylan Owen Room

Characterising a new environmentally sensitive membrane dye

The cell membrane is composed of a lipid bilayer which can exist in either

an ordered or disordered
state. Fluorescent dyes exist which change their fluorescent properties depending on the degree of
membrane order. In this project you will characterize the newest such dye


recently developed in the US, nothi
ng is known of its sensing properties. You will create artificial
ordered membranes and measure the dye’s excitation and emission spectra. You will culture live cells,
image the dye in cell membranes by a variety of cutting
edge microscope techniques and q
uantify its
performance against the current state
art alternative probes.

Research Category: Biophysics, Optics, Microscopy

Samjid Mannan Room

Experimental Investigation of Nanoparticle Sintering

This project aims

to shed light on fundamental mechanisms of nanoparticle sintering and the properties
of the resulting nanostructured material through experiment. Sintering metallic nanoparticles together
results in a material which can have dramatically different propert
ies from those in the bulk metal. In
particular, the high density of grain boundaries and porosity left over from the sintering process can lead
to rapid diffusion of atoms through the sintered material. Experiments will attempt to probe whether
atomic dif
fusion is primarily caused by transport along the grain boundaries or by surface diffusion
across the pores by using electron microscopy. Novel applications of the nanostructured materials will
be explored.

Research Category: Nanotechnology


Fairbairn Room

22. Warp Drives

We will look at the Albubierre

Warp Drive Metric and seek to understand why it requires exotic energy
to be a valid solution of Einstein's field equations.

This project will require a first class mark in third year
GR and a reasonable understanding and confidence with general relativi
ty as a subject.

Annual modulation of Dark Matter direct detection signal.

We will look at the direct detection of dark matter and how the event rate

changes as the earth moves
around the Sun.

We will try to understand how different distributions and can
didates of dark matter
affect the signal.

The student will require to be able to code relatively confidently in Fortran, C, Python
or Java. Mathematica, Maple or Matlab are NOT acceptable alternatives.

The project has the potential
to get to research lev
el and lead to a publication.

Genetic Algorithms and Top Quark Tagging

These are algorithms which can solve problems by modelling how genes and genomes work.

They can
solve problems which cannot be solved by other kinds of algorithms.

We will apply them
to identifying
top quark pairs at the LHC, a very difficult problem which career researchers in the field find challenging.

This is an extremely complicated project which should only be attempted by a very capable and
resourceful student, however the pote
ntial outputs are significant.

The student will require to be able
to code relatively confidently in Fortran, C, Python or Java.

Mathematica, Maple or Matlab are NOT
acceptable alternatives.

Dr. Riccardo Sapienza Room

n random lasing

When we think of a laser, we usually imagine a device that can emit a monochromatic light beam in a
specific direction. However, neither of these characteristics forms part of the definition of laser: light
amplification by stimulated emiss
ion of radiation. In fact there are lasers, known as random lasers,
which emit in every direction and in many different colors.

A random laser is a system formed by a random white powder dispersed into an optical gain medium
like fluorescent dyes. The stra
line path of light propagation in a conventional laser is broken into a
random walk when light is scattered by the nano
sized powder grains. When the various ingredients are
mixed in the right way lasing can be initiated, as shown in the figure below.

The project consists in the realization of a random laser that can be painted on a given object. The
project is mainly experimental, and it requires optimisation of the optical setup and the experimental
proof of random lasing action as a narrowing of the

emission spectrum.

Skills required: knowledge of optics and quantum optics and basic experimental skills. Familiarity with
basic Chemistry and data analysis is also desirable.

Research Category:
Optics & Photonics, Material Science