Dr Chris Clarkson's Project Abstracts
BSc/MSci Review Project Abstracts
These are suitable for the Physics, Astrophysics and Theoretical Physics streams.
Gravitational Lensing
Gravitational lensing is the bending of light around massive objects due to the curvature of spacetime. This project will explore this effect from a theoretical and observational point of view. Simple gravitational lens models will be constructed and investigated. Different lensing regimes - strong, weak, and micro - will be considered and their use in understanding the universe explored.
Why is the expansion rate of the universe speeding up? Einstein's general theory of relativity accounts for this with a cosmological constant. But this apparent constant of nature is not motivated from a quantum point of view leading to researchers proposing a huge variety of so-called dark energy models, including modifications of general relativity itself. This project will review the observational evidence for dark energy, and undertake a survey of the different types of models proposed to replace the cosmological constant.
The evolution of sound waves during the first 400,000 years of the universe's history have left a frozen imprint of the early universe in the cosmic microwave background radiation that we observe today. This pattern encoded in this radiation tells us about the big bang, the origin of the distribution of galaxies at late times, as well as the composition of the constituent matter in the universe. This project will explore the radiation era of the early universe, and investigate how to calculate the cosmic microwave background temperature fluctuations, and determine how the spectrum of these fluctuations tells us a lot about our universe.
Some general relativity knowledge and good programming skills will be needed.
Gravitational waves are fluctuations in spacetime and are generated with massive energies when black holes collide - the first instance was just detected with the LIGO observatory. This project will explore how gravitational waves are produced, and the calculation of some gravitational waveforms will be undertaken for a test particle orbiting a black hole. The `ringdown' phase - the waveform emitted as the final black hole settles into its equilibrium state - will also be investigated.
Good general relativity knowledge and good programming skills will be needed.
MSci Research/Investigate Projects
General relativity in cosmology
The coming decade in cosmology will see surveys of large-scale structure of unprecedented scale and depth, mapping the universe in great detail on the largest scales. Modelling the universe to the required precision requires corrections to the usual Newtonian and linear approximations usually used arriving from Einstein’s general relativity. The modifications come both in how structure evolves, and in the way we observe and count galaxies, for example. This offers new ways to test GR on cosmological scales. This project will investigate these effects, and investigate how they can be observed.
This project will require knowledge of general relativity and cosmology; it will require strong mathematical and programming skills.
Gravitational lensing - from weak to strong
Gravitational lensing is the bending of light around massive objects. Modelling of this is done in a variety of ways, but is typically analysed differently in strongly lensed (where drastic shape changes and multiple images appear) versus weakly lensed (%-level changes to an objects ellipticity) regimes. Cosmological surveys constrain cosmological parameters in the weak lensing regime, and cluster mass reconstruction can be achieved in the strong lensing regime. This project will investigate a unified approach to both the weak and strong lensing regimes.
