Astrophysics
The
Hunt for "Free-Floating" Planets
Supervisor: Prof.
Chris Tinney
Over
230 extra-solar planets are now known to orbit nearby stars.
Most of these
have been discovered by the Doppler wobble technique, and so
have
only been "indirectly" detected via their impact on their host
star. So none of
these
planets has actually been seen directly.
In this project
you will use the recently developed technique of methane imaging
to
search
for, and image, "unbound" planets (ie planets without a host
star)
and brown dwarfs (ie.
stars too low in mass to burn nuclear fuel) in young southern
star
clusters.
Planets are believed to form in the accretion disk via which
interstellar
material is fed onto young forming stars. It is known that both
planets
and stars can be formed over a large range of masses, with the
lowest
mass
objects formed like stars (brown dwarfs) having masses so small
that
they
overlap with the masses of the largest planets. The aim of this
research
project will be to compare the number distribution of the objects
in
young
star clusters with masses of 1-30 Jupiter masses, with the number
distribution of more massive stars, in an effort to disentangle
the
different formation mechanisms of stars and planets.
The primary tool for this will be methane imaging. The coolest
objects
detected to date outside our solar system are "T-dwarfs" - star-like
objects with temperatures of 800-1300 Kelvin that show pronounced
features in their near-infrared spectra due to methane absorption.
Methane imaging (ie near-infrared imaging in bands at 1.5-1.65
and
1.65-1.8um)
can powerfully discriminate these rare objects from all other
contaminating objects in the fields of young star clusters. Moreover,
when used to
detect
young objects, it can reveal objects as low in mass as 1 Jupiter
mass.
In this project, data from 16 nights of observing with the
IRIS2 instrument on with the Anglo-Australian Telescope will
be used,
together with additional data on other telescopes including
Magellan and Gemini to make the deepest searches for objects
of
planetary mass in young, southern star clusters.
See Prof
Tinney's web page
for more details on this project and other research projects
within this
group.
PhD scholarship in astronomy
A PhD scholarship in astronomy is available to work with Professor Michael Burton
investing the earliest stages of massive star formation. The applicant
should have an honours degree in Physics, Chemistry, Mathematics,
Engineering or Computing Science.
The Department of Astrophysics is one of Australia's leading university
research groups in astronomy. We have a particularly strong program in
millimetre-wave astronomy, making use of the world-leading facilities
Australia has for these kinds of observations, which enable us to study
the emission from molecules in space. In particular, we make use of the
22m Mopra telescope, located at Coonabarabran in NSW, together with the NANTEN2 telescope
on the 5,000m elvation altiplano of Chile. These facilities provide
formidable spectrometers which allows one to study the astrochemistry
associated with the formation of stars.
Funded in by part of an ARC Discovery grant, this scholarship will
provide $15K per year. PhD students in the School may simultaneously
accept Postgraduate Assistantships, which provide additional guaranteed
income of up to $10k per year, in return for agreed teaching duties. The
scholarships do not cover tuition fees. Australian and New Zealand
students do not pay tuition fees. The university campus is located in
the East of Sydney, close to Coogee Beach.
For further information, please contact Professor Michael Burton, School
of Physics, University of New South Wales, Sydney, NSW 2052. Tel
02-9385-4553, Email m.burton@unsw.edu.au. URL:http://www.phys.unsw.edu.au/STAFF/ACADEMIC/burton.html
A description of the project is given below:
 The
Earliest Stages of Massive Star Formation
Supervisor: Michael
Burton
The evolution of our Galaxy is driven by the massive stars that reside within it. These are stars greater than ten times the mass of the Sun, and thousands of times brighter. Their prodigious luminosities drive energy flows, which in turn power the cycle of elements between the stars and the gas, and back to the stars again. Each time the cycle is passed through it is enriched by the products of nucleosynthesis, occurring in the cores of the stars. The crucible of this process is the formation of these massive stars. Yet this remains somewhat of an enigma, for a number of reasons. Massive star formation takes place rapidly. The nearest examples are distant from us. It takes place in clusters with stars at different stages of formation. Many different physical processes are taking place simultaneously. This makes it a fascinating challenge to study!
In recent years the advent of sensitive and high angular resolution infrared cameras has made it possible to detect the forming stars.Combined with new millimetre-wave telescopes and interferometers that allow us to observe the rich range of molecules present, we are now able to determine the physical state of the molecular cores where massive stars are born, and to follow their childhood as the star passes through a series of stages being emerging on the Main Sequence.
In particular a time-dependent chemistry is evident, complex organic molecules created inside "hot molecular cores" surrounding an incipient star. The molecules present at any time provide a signpost which points to the stage star formation has reached - if only we could read the signpost. One aspect of this project is to decode the language the signpost is written - by determining what molecules are present in a variety of cores, and how these change as the cores develop towards the formation of a new star. This involves observation using new millimetre-wave telescopes, both in Australia and under construction on the Atacama plateau of northern Chile.
How many stars form in a hot molecular core? Do they follow a universal initial mass function, and does this vary from core to core? What physical characteristics of the core determine the range of stars that form? Such questions can be tackled through deep infrared observations. These will allow us to uncover the newly forming stars while they remain deeply embedded in their natal cores, and to investigate their spectral characteristics to indicate what type of star(s) will emerge from it.
This PhD project will thus involve millimetre-wave and infrared observations of molecular clouds where massive star formation is underway, and the subsequent analysis and interpretation of this data. It will make use of the single-dish Mopra Telescope and the interferometer of the Australia Telescope to find where the molecular species are. It will use the new NANTEN2 telescope on the 5,000m Atacama plateau of Chile to determine the excitation of the clouds. It will also use infrared telescopes in Chile, combined with data from space infrared telescopes, to measure the stellar content and determine what kind of stars are forming.
Turbulent
Star Formation: the role of turbulence in regulating star formation
in our Galaxy.
Supervisors: Maria
Cunningham and Michael
Burton
Stars
form from within dense cocoons of gas and dust which are hidden
to our view at optical wavelengths. The young stars can, however,
be seen using infrared and millimetre wave telescopes. A comprehensive
theory of star formation is one of the major unsolved problems
of astrophysics, with currently only the collapse of an isolated
cloud into a single star being reasonably well understood. However
most star formation occurs in clusters, so this theory cannot
apply to majority of stars that we see.
Recently
a new "turbulent model" of star formation has been proposed
which has the potential to provide a unified theory for this process.
The model, however, remains relatively untested and unconstrained
by observation. Testing it will be the prime focus of this PhD
project. The idea behind the model is that supersonic turbulence
is driven on galactic-scales to smaller scales via an energy cascade.
This acts both to encourage collapse of a cloud under gravity,
and to also provide support against it. In the theory, turbulence
regulates the rate of star formation in the Galaxy, as well as
determining the efficiency with which it occurs inside a given
molecular cloud. Modelling suggests that density fluctuations
in the cloud depend on the strength of the turbulence and the
scale on which it is injected, and that this can be examined through
observation. In a molecular cloud tracers of low density gas,
such as the carbon monoxide (CO) molecule, will have a different
distribution to that of high density tracers, molecules like carbon
mono-sulphide (CS) and silicon monoxide (SiO), if the turbulence
is weak. On the other hand their distribution should be similar
if the turbulence is strong. All these molecules, and many more,
can be mapped, using the Mopra millimetre wave telescope, together
with a new correlator that we have recently installed. We have
instigated the "Delta Quadrant Survey" to pursue this
investigation, mapping a molecular cloud complex in the southern
galactic plane in a variety of molecular lines that emit at mm-wavelengths.
These molecular maps will then be compared to the distribution
of newly formed stars, as evident through infrared images, to
enable us to examine the role of turbulence in driving and regulating
the formation of stars.
Varying
Constants
Supervisor: Prof
John Webb
Spectroscopic
observations of distant quasars lead to stringent constraints
on any change in physics over cosmological timescales. Theoretical
motivation for seeking cosmological changes in the laws of Nature
come from several new ideas including string theory. Recent advances
in telescope and detector technology, and in analytical methods,
now permit measurements of unprecedented accuracy, providing sensitive
and fundamental tests of Einstein's equivalence principle and
potentially opening the doors to new physics.
This
project is an experimental one. It requires fastidious analyses
of new extremely high quality astrophysical data, from the Keck
telescope and from the ESO VLT, to probe the values of certain
physical constants billions of years ago.
Introductory
articles can be found in: "Inconstant Constants" by
John D. Barrow and John K. Webb, Scientific American, June 2005
and "Are the Laws of Nature Changing with Time?", John
K, Webb, Physics World, Vol. 16, Part 4, pages 33-38; April 2003,
(also available **here** link to: http://www.phys.unsw.edu.au/astro/research/PWAPR03webb.pdf).
High
Redshift UV Background Radiation
Supervisor: Prof
John Webb
Knowing
the ultra-violet background radiation field at high redshift is
fundamental to our understanding of cosmology, galaxy formation
and galaxy evolution.
This
project involves using new large astrophysical databases to make
the most precise measurement of the UV flux to date. The new database
should permit the first ever detection of cosmological evolution
of the UV flux.
The
results will reveal new details of the early history of the universe,
provide new information about the formation of the first collapsed
objects formed and about the so-called epoch of re-ionization,
will constrain the number of massive black holes formed at early
times, and will also provide new constraints on the nature of
the dark matter.
Extra-Solar
Planets
Supervisor: Prof
John Webb
One
of the most exciting recent developments in astrophysics is the
discovery of extra-solar planets. This is a rapidly expanding
scientific field, still in its infancy, with the prospect of many
discoveries ahead.
At
present, the known extrasolar planets have been discovered almost
exclusively using the Doppler wobble method, i.e. searching for
periodic velocity shifts in the host star due to the orbiting
planet. This method has proved very successful but requires large
amounts of observing time on large telescopes.
Extrasolar
planets can also be found using large field imaging telescopes
to search for a periodic decrease in the host star apparent brightness
as a planet eclipses it. This requires a favourable alignment
of the planetary orbital plane with respect to our line of sight,
but wide field imaging provides the necessary statistics to potentially
discover large numbers of objects.
A
fundamental advantage of discovering planets eclipsing their host
stars is the potential for studying any atmospheric absorption
features from the planet using the background star as a probe.
A
project of this sort is underway in our department using the "Automated
Patrol Telescope" at Siding Spring, NSW. In 2006 we shall
take delivery of a new CCD camera currently being constructed
by the Anglo-Australian Observatory. The new camera will provide
roughly a 10-fold efficiency gain for our search and producing
a world-class facility for this kind of research.
The
PhD project will involve working on all aspects of this challenging
and exciting new programme.
Biophysics
Thermal
ecology.
Australia's alpine environments, including snow gum forests, are
often limited by freezing damage (and plants raised on high CO2
are more freezing sensitive). Leaves can be significantly colder
than air
temperature because of radiation into the cold sky, which can
limit the reestablishment of forests.
Thermal imaging and electron microscopy have revolutionised investigations
in this area. This project would involve field, lab and modelling
studies in collaboration with the ecology lab at RSBS, ANU.
(More at www.phys.unsw.edu.au/~jw/snowgums.html
Contact Joe
Wolfe.)
Cellular
mechanisms of salt tolerance.
Plant Membrane Biophysics.
Dr.
Mary Jane Beilby.
Ph.D project starting in 2006
Background.
All plant cells evolved from the ancient ocean, where they had
to survive in a world rich in common salt, NaCl. When plants moved
onto the land, they found themselves in a less saline world, either
growing in the soil or living in rivers and ponds. All cells,
animal, plant and bacterial, accumulate K+ and exclude
Na+, which can have deleterious effects on the functioning
of proteins, and can cause cells to lose water. It is thought
that cells achieve this via protein channels and energy-consuming
pumps in the cell membrane. These are often called transporters.
Many modern land plants, including most crops, experience Na+
as a toxin and are unable to exclude it from their cells. Fortunately,
some land and aquatic plants retained the ancient ability to tolerate
NaCl. This involves many types of adaptations, including salt-extruding
glands. The challenge of high salt must be also met by individual
cells. Plant cells are encased in cellulose walls. The cells accumulate
K+, attracting water, which generates internal pressure (turgor)
that is balanced by tension in the cell walls. Turgor enables
non-woody plants to stand up. Salt-tolerant plants are able to
exclude Na+ from the living cytoplasm, and change their
internal concentration of salts to retain enough water and keep
turgor at a comfortable level. All cells, from bacterial to animal
to plant, employ K+ and usually Cl- as the
ions gained or lost during volume and/or turgor regulation. The
ability to take up or expel these ions is central to surviving
high salinity and/or salinity fluctuations. Turgor regulation
essentially involves conversion of mechanical stimulus to electrochemical
regulatory events, such as ion flows into or out of the cell.
Survival in salty environments dates back to the earliest plants,
yet we still do not understand how the structure of the cell and
its electric circuitry work together to enable this to happen.
Are the transporters different in salt-tolerant and salt-sensitive
plants? Is more of some transporter expressed in salt-tolerant
species at the time of stress? Or is it the way the transporters
work together in salt tolerant species? One approach to studying
this fundamental problem is to go back to the ancient group of
giant celled algae, the charophytes. One branch of their family
evolved into the land plants, whilst other branches became modern
charophytes. Some charophytes (Lamprothamnium succinctum)
survive in a fluctuating environment, from freshwater to twice
the saltiness of seawater, whilst other charophytes (Chara
australis) live in freshwater, and, like many crop plants,
cannot cope with highly salty environments. The giant size of
charophyte cells (of up to 1 mm in diameter and several cm in
length) enables us to study salt tolerance at the level of single
cells, with minimal disturbance to the extracellular matrix (ECM),
a cell wall- membrane-cytoskeleton continuum.
The
project. The research combines three types of techniques,
applied to the cells under osmotic/salt stress:
(i) Electrophysiology, which measures ion fluxes across the cell
membranes. We concentrate on the potassium and chloride ion channels,
which mediate efflux of these ions upon exposure to hypotonic
(less salty) medium. A proton pump and the chloride/proton co-transporter
are monitored at the time of hypertonic (more salty) stress.
(ii) Fluorescence microscopy, to observe structural changes in
the connections between the membrane, the protein network called
the cytoskeleton, and the cell wall (ECM).
(iii) Exploration of the cell wall structure through physical/chemical
means and neutron scattering, performed at Lucas Heights nuclear
reactor in collaboration with Dr. C. Garvey.
The
student can learn the whole range of techniques or concentrate
on one of the strands, depending on their background and interests.
Music
Acoustics
Vocal tract acoustics - singing.
The voice is often described in terms of a simplified source-filter model: the source is the harmonic-rich signal produced by the vocal folds and the filter is the upper tract, which has several resonances and which acts as a variable, tunable impedance matcher to the external radiation field. Singers trained in different styles both adjust the source function and tune the resonances to achieve a range of different effects. With suitable feedback, singers may learn these advanced techniques more easily. The lab has unique technologies and has published several papers on the acoustics of singing, but there is much more to investigate, especially regarding interactions between the vocal fold motion and the standing waves in the tract. (More details at www.phys.unsw.edu.au/music. Contact John Smith or Joe Wolfe.)
Vocal tract acoustics - speech.
In speech, the frequency of the source signal produced by the vibrating vocal folds is not of primary importance. This project will examine the characteristic resonances associated with different vowel sounds in different languages, and examine how the available phoneme space is subdivided for both production and perception. This research has a range of potential applications, some of which may be followed according to the inclination of the student. We also study the interactions between the vocal fold motion and the standing waves in the tract, but list this under singing, because experiments are more readily conducted on sustained steady phonations. (More details at www.phys.unsw.edu.au/speech. Contact John Smith or Joe Wolfe.)
Acoustics of brass instruments - the effect of the player's vocal tract.
When playing a brass instrument, the player's lips are coupled acoustically to two resonators. The acoustical properties of the bore of the instrument are relatively well understood, but those of the player's vocal tract have hitherto been difficult to measure. This is now possible, using techniques developed in the lab. This project looks at the influence of the tract on timbre and pitch in different aspects of performance, and will build upon the measurement techniques we developed for the dijeridu and for woodwinds. (More details at www.phys.unsw.edu.au/music. Contact John Smith or Joe Wolfe.)
Acoustics of woodwind instruments - fingering, embouchure and tract interactions.
How are the many control parameters varied in woodwind playing? What is required to produce desirable sounds and smooth, reliable transitions between notes on a wind instrument? Why do players spend so much time practising scales and arpeggi? This project investigates how fingers, embouchure and vocal tract configuration are adjusted and coordinated in different aspects of performance. This project uses unique technologies in the lab to measure the performance of real musicians. We also use an automated clarinet player to test some of the ideas. (More details at www.phys.unsw.edu.au/music. Contact John Smith or Joe Wolfe.)
Acoustics of wind instruments – vibrato, tone colour and expression.
This project looks at timbre and expression, including vibrato, its causes, use and effects. Spectral envelope may be varied by players, and vibrato and other features of the temporal envelope are important aspects of musical expression. What physiological parameters are varied to vary timbre and to produce vibrato? What effect do they have on the output sound? How these physical and physiological effects used in performance, and what are the corresponding perceived qualities in the sound? The project will combine measurements of embouchure and vocal tract response with measurements of the sound. (Contact John Smith or Joe Wolfe.)
Collaborative projects between the School of Physics and the School of Music and Music Education.
Many questions of great importance to music performance involve physical questions. A keen musician, with a strong practical bent, would be capable of doing serious research that involves direct measurement of the physics of instrumental performance. The two Schools have collaborated in the past and are continuing to do so. Students who are interested in enrolling for a postgraduate degree in music, with external part-supervision from the Acoustics Group should discuss the project with us. (Contact John Smith or Joe Wolfe.)
Theoretical
Physics
Computational Methods for Strongly Correlated Models in Two Dimensions
(Supervisor: A/Prof. Chris Hamer)
The treatment of strongly correlated quantum lattice models in two dimensions is one of the ‘grand challenges’ for theorists. Such models may represent high-temperature superconductors, organic conductors, exotic magnetic materials, or even gauge models in particle physics. Quantum fluctuations are especially large in two dimensions, and strong correlations are predicted to lead to exotic phenomena such as ‘spin liquid’ states, ‘deconfined’ quantum phase transitions with fractional excitations, as well as high-temperature superconductivity and other new effects. Unfortunately, our traditional techniques of numerical calculation have proved inadequate to confirm these predictions.
Recently, new techniques involving matrix product representations of wave functions by Cirac, Verstraete and Vidal have attracted great interest for these two-dimensional models. The project is to develop, test and apply an alternative technique involving localized cluster correlation coefficients on the lattice, which may be more efficient than the matrix product approach. The work will suit those with a computational bent.
High-temperature superconductivity.
Supervisor Prof. O. P. Sushkov
The quest for understanding the mechanism of high-temperature superconductivity in the copper oxide materials has been at the forefront of condensed matter physics research for two decades. The experimental situation in the field has advanced dramatically during the past several years. These advancements represent a challenge for theory, and, more importantly, have created a great opportunity for theory to provide deeper insights into the physical phenomena. The superconductivity project of our group can accommodate 2-3 PhD students.
PhD research projects are aimed at:
1)Spin dynamics in high-temperature superconductors.
2)Charge dynamics in high-temperature superconductors.
Lyapunov
Modes and Correlation time scales
Supervisor A/Professor
Gary Morriss
The
study of the Lyapunov stability of classical systems of particles
has revealed that as well as a spectrum of eigenvalues, called
the Lyapunov spectrum, there are the associated eigenvectors of
the time evolution which have some unexpected properties. The
eigenvectors associated with the smallest positive and negative
exponents are delocalised and represent global motion of the system.
The time dependence of these modes is likewise unexpected and,
in at least one case, related to the decay of correlations. There
are a number of possible research directions based on the initial
studies of Taniguchi & Morriss.
Atomic clocks and fundamental physics.
Supervisors: Prof.
V. V. Flambaum, Dr.
V. A. Dzuba
The study of atomic clocks is a rapidly developing area of research due to important role atomic clocks play in metrology, navigation and fundamental research. For example, the metric second is defined as duration of 9,192,631,770 periods of oscillations between the two hyperfine levels of the ground state of the cesium atom. The error of this clock is less than a second in 60 million years! In spite of this incredible accuracy atomic clocks are still not sufficiently accurate for some navigation tasks, e.g. automatic aircraft landing. There are many proposals to build even more accurate clocks by using atomic optical transitions or appropriate nuclear transitions.
Fundamental research would also benefit a lot from improving the accuracy of atomic clocks. For example, some theories unifying gravity with other interactions allow the fundamental constants to very. Variation of fundamental constants may be an indication of extra dimensions in our Universe or even parallel universes. The variation of fundamental constants in space may explain famous fine tuning of fundamental constants which is need for life to appear. We appeared in the area of the Universe where the fundamental constants are consistent with existence of life.
The temporal variation of the fundamental constants can be studied by comparing different atomic clocks over long period of time. The best current result of this kind comes from comparison of optical transitions in aluminium and mercury ions. It reads that if the fine structure constant changes in time than it changes no faster than tiny fraction of 10-17 a year!
We search for the ways to improve the accuracy of atomic clocks, perform atomic and nuclear calculations to help in the clocks design and for the interpretation of the measurements. The student may choseto be involved in any aspects of this work on his/her and the supervisor's discretion.
A scholarship top-up is possible for exceptionally good applicants.
Calculation of isotope shift in many-electron atoms and study of fundamental interactions.
Supervisors: Prof.
V. V. Flambaum, Dr.
V. A. Dzuba
Isotope shift is the difference in optical spectra of different isotopes of the same atom. This difference is due to difference in mass and nuclear structure. Examining the effect of isotope shift on the atomic spectra of distant objects in the universe provides an opportunity to study isotope abundance evolution in early universe and test theories of nuclear reactions in stars and supernova. On the other hand, study of isotope shift in heavy atoms can be used to obtain valuable information about nuclear structure. This information is to be used to reduce uncertainty of experimental study of fundamental interactions in heavy many-electron atoms. In both cases accurate atomic calculations are needed for interpretation of experimental results.
The project involves using existing and developing new computer codes in Fortran, running these codes and combining theoretical and experimental results to extract information about fundamental interactions.
A scholarship top-up is possible for exceptionally good applicants.
Study of relativistic and quantum electrodynamics effects in many-electron atoms.
Supervisors: Prof.
V. V. Flambaum, Dr.
V. A. Dzuba
Electrons in heavy atoms move with speeds close to the speed of light. Therefore they should be treated relativistically for accurate results. Dominant relativistic corrections are usually included by replacing Schrödinger equations for single-electron states by Dirac equations. Breit and quantum-electrodynamic (QED) corrections are smaller relativistic effects which are not included in Dirac equation but still play important role in heavy atoms. Breit interaction is the difference between exact relativistic expression for the inter-electron interaction and its non-relativistic Coulomb approximation (e^2/r). Leading terms in this difference are magnetic interaction and retardation. QED corrections are due to interaction of atomic electrons with vacuum fluctuations.
Project involves developing and running Fortran computer codes for accurate relativistic calculations for heavy atoms. The results would contribute to the relativistic theory of atoms and help in interpretation of experimental investigation of fundamental interactions in heavy atoms.
A scholarship top-up is possible for exceptionally good applicants.
Effects of variation of fundamental constants of Nature from Big Bang to atomic clocks.
Supervisors:Prof.
V. V. Flambaum, Dr.
V. A. Dzuba
Variation of fundamental constants (speed of light, electron electric charge, etc.) in space and time is suggested by theories unifying gravity with other interactions. Another argument for the variation comes from the anthropic principle. There must be very fine tuning of the fundamental constants which allows humans (and any life) to appear. This fine tuning can be naturally explained by the spatial variation of the fundamental constants. We appeared in the area of the Universe where the values of the fundamental constants are consistent with our existence.
The aim of this project is to search for the manifestation of the variation and perform necessary calculations of observable effects. For example, a change of the fundamental constants influences outcome of the Big Bang nucleosynthesis. The primordial amounts of deuterium, helium and lithium have been measured by astronomers. Comparing the calculations and measurements one can determine values of the fundamental constants after Big Bang. Variation of the fundamental constants also influences quasar spectra and ticking of different atomic clocks. A number of such measurements are now in progress. To interpret these measurements we should perform calculations of the variation effects for atomic transition frequencies. These calculations can be done using computer codes developed in our group. It is also very important to find new, enhanced effects of the variation and suggest new measurements.
This project may involve both analytical and numerical calculations in different areas of physics and cosmology, and may accommodate several PhD students.
A scholarship top-up is possible for exceptionally good applicants.
Violation of fundamental symmetries in atoms and test of grand unification theories.
Supervisors:Prof.
V. V. Flambaum, Dr.
V. A. Dzuba
Recently great progress has been made in experiments on violation of parity and time reversal invariance in atoms. The aim of this project is to perform necessary atomic and nuclear calculations of the observed effects which are needed to test theories unifying all interactions of Nature. Different theories predict different strengths of weak interactions which violate parity and time reversal invariance, and comparison between the calculations and measurements will help to select correct theory.
It is also very important to find new, enhanced effects of the violation of the fundamental symmetries and suggest new measurements.
This project may involve both analytical and numerical calculations in atomic, nuclear and particle physics, and may accommodate several PhD students. Atomic calculations can be done using computer codes developed in our group.
A scholarship top-up is possible for exceptionally good applicants.
Reaction-Diffusion
Models
(Supervisor: A/Prof.
Chris Hamer)
Reaction-diffusion
models describe particles which can travel over a grid, or evaporate
from or condense onto the grid. They can be used to model chemical
reactions, or adsorption or desorption of particles from a surface,
or even the flow of traffic. They can be formulated in terms of
a master equation like the Schroedinger equation, but with a non-Hermitian
Hamiltonian, in the general case.
The
project, formulated in collaboration with Dr. R. Stinchcombe from
the University of Oxford, is to calculate the phase structure
and properties of these models using series expansion techniques.
Our group has great expertise in perturbation series expansion
techniques for the usual Hermitian systems; but the treatment
of non-Hermitian systems requires the development of new techniques
and algorithms. The work would involve advanced computational
techniques. This is a new venture for our group, and there is
considerable scope for future work in this area.
Application of the PEPS method to Strongly Correlated Systems in Two Dimensions
(Supervisor: A/Prof.
Chris Hamer)
The treatment of strongly correlated lattice models in two dimensions presents a special challenge to theorists. Such models may represent high-temperature superconductors, organic conductors, exotic magnetic materials, or even gauge models in particle physics. Quantum fluctuations are especially large in two dimensions, and strong correlations are predicted to lead to exotic phenomena such as ‘spin liquid’ states, ‘deconfined’ quantum phase transitions with fractional excitations, and other new effects. Unfortunately, our traditional techniques of numerical calculation have proved inadequate to confirm these predictions.
Recently a new technique called ‘PEPS’ involving matrix product representations of wave functions has been formulated by Cirac, Verstraete and Vidal, which may provide much improved results for these two-dimensional models. The project is to develop, test and apply these techniques to some of these interesting models. The work will suit those with a computational bent.
Quantum
properties of black holes.
Supervisor: Dr.
Michael Kuchiev
Black
holes are surrounded by event horizons, which represent a boundary
between the outside world and the inside region. Well known classical
description of the problem reveals that a particle, which approaches
a black hole, crosses the horizon quite smoothly; the probability
to penetrate inside is 100%. However, it was demonstrated recently
in Refs.[1,2] that quantum corrections change this conclusion
qualitatively. Quantum effects make it possible reflection from
the event horizon, which is a surprising result. The reflection
is possible for any particle, being stronger for long-wave particles.
For sufficiently large wavelengths the particle cannot cross the
horizon at all, being predominantly reflected. In other words,
the black hole in this situation behaves as a good mirror.
The
project aims to study relations of this new property of black
holes with their other properties, in particular with the Hawking
radiation, the information paradox and related phenomena.
References:
1. M.Yu.Kuchiev. Reflection from black holes and space-time topology,
Europhys. Lett. 65, 445 (2004)
2. M.Yu.Kuchiev, Reflection, radiation and interference for black
holes, Phys. Rev. D 69, 124031 (2004);
gr-qc/0310051
3. M.Yu.Kuchiev and V.V.Flambaum, Scattering of scalar particles
by a black hole, Phys. Rev. D 70,
044022 (2004); gr-qc/0312065
The
Quantum Electronic Devices Group studies the fundamental electronic
and magnetic properties of advanced nanostructure devices. Research
students use state-of-the-art semiconductor clean-room processing
equipment to fabricate these devices, and ultra-low temperatures
and sensitive electronics to study them. Students regularly make
international trips to conferences and to visit collaborators
- the group has active links with leading laboratories in the
USA, UK (Cambridge), Japan (NTT), Denmark (Niels-Bohr Institute)
and Italy.
Semiconductor
Nanostructures: We are world leaders in fabricating p-type
quantum wires, which show outstanding electrical properties and
possibilities for spintronics applications. High-resolution electron
beam lithography is used to fabricate nanoscale devices from custom
grown ultra-low disorder GaAs-AlGaAs heterostructures. The project
will also develop devices with both electrons and holes, where
the attractive Coulomb interaction may allow the formation of a bosonic
superfluid.
High
speed quantum devices: Most quantum devices are studied
at low speeds (<1kHz). Higher speeds(~1GHz) provide new tools
for probing many body quantum states (c.f. the 1998 Nobel prize
in Physics). This project will study high-frequency properties
of quantum wires, and the change in ‘noise’ when an excitonic
superfluid forms.
Organic
electronics and new nanofabrication techniques: Projects
are available to use soft-lithography to develop new devices based
on organic molecules and carbon nanotubes. This has the potential to
allow the electrical properties to be tailored with suitable chemical
preparation.
See
www.phys.unsw.edu.au/QED
for details or contact A/Prof.
Alex Hamilton, Dr.
Adam Micolich .
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