School of Physics & Astronomy

We trace the origin of the dark matter, dark energy and quantum gravity problems to the extrapolation of the standard Newton-Einstein wisdom to beyond its solar system origins. We show that this same solar system wisdom can be obtained from the conformal gravity theory, with its extrapolation leading to a resolution of all of the dark matter, dark energy and quantum gravity problems.

I am a Lecturer in the School of Physics and Astronomy and my research interests lie primarily in the development of innovative optical technologies that push the boundaries in life sciences. Specifically, my team and I work on developing novel optical microscopy techniques to investigate the function and structure of the heart. In addition, I am working to increase inclusion and diversity in the STEM community.
In this talk I will give an overview of the various research activities pursued in our group including light-sheet microscopy of clarified tissues, fast remote focusing for vertical line scanning, 3-photon microscopy and random-access parallel microscopy. I will also briefly introduce our efforts towards quantum-enhanced multiphoton microscopy and our recent application for an inverted CDT model.

Artist Dr Gregor Harvie will talk about his ongoing exploration of quantum theory, asking whether there is a fundamental structure underpinning our world, what that might look like and how it might be represented visually as art. He will discuss the long and close relationship between art and science and the potential for using languages other than maths to explore and describe physics.

He will also introduce the project he is developing with the help of the university to engage a wider audience in the quantum world and will invite anyone with a particular interest in the subject to help steer his work to ensure it is a genuine reflection of scientific thinking.

Encapsulating a sample between two inert and impermeable few-layer 2D sheets (such as graphene or hexagonal boron nitride) is one approach to enable transfer of materials from an inert vacuum or glove box environment to the transmission electron microscope (TEM) without exposing them to atmospheric conditions. We have applied this approach to study air sensitive 2D materials, including local point defects, doping and edge structures in a wide range of 2D crystals (e.g. CrBr3, GaSe, black phosphorus) [1,2]. We also use the approach to preserve the delicate surface structure of hydrated layered crystals, enabling the visualization of exchangeable surface cations on few layer clays and micas [3] and a route to understand the changes in atom/ion motion at interfaces where the 2D materials are twisted with respect to each other (Fig. 1d) [3,4]. This 2D heterostructure approach can also be used to investigate solid-liquid interfaces. Building on nanochannel technology developed by the group of Andre Geim [5] we have developed in-situ liquid phase TEM imaging using 2D heterostructure nanochannels. The in-situ 2D heterostructure liquid cell approach provides atomic resolution imaging and analysis and makes it possible to study the earliest stage of chemical synthesis [6]. The method can also reveal large differences in adatom adsorption sites on surfaces in vacuum compared to hydrated environments and allows study of dynamic adatom motion at solid liquid interfaces [7]; something that was not previously possible by any technique.

Fig 1) i) Scanning TEM imaging of exchangeable surface cations on few layer clays [3], (ii) Schematic of the graphene liquid mixing cell and atomic imaging in liquids geometry, with an example of the liquid phase imaging of Pt on MoS2 in aqueous salt solution [7]. 

References: [1] Hopkinson, et al. ACS Nano, (2019), 13, 5, 5112; [2] Hamer et al. Nano Lett. (2020), 20, 9, 6582 [3] Zou et al, Nature Materials (2021), 20, (12) 1677; [4] Weston et al, Nature Nanotechnology (2020), 15 (7), 592; [5] A Keerthi et al, Nature, (2018), 558 (7710), 420; [6] Kelly et al, Advanced Materials, (2021) 33, 29, 2100668; [7] Clark et al. Nature 609, 942, (2022);

Taking a bit of inspiration from Caroline, I figured I'd introduce myself and my research a little, given that I joined the university just before the pandemic hit and somewhat missed introductions. I'm a Research Fellow in the Quantum Theory group, though I work quite closely with the Extreme Light group and the Atom Optics part of the Optics group. My research is a fairly eclectic mix, but it (mostly) focuses on using, producing and understanding quantum light. Today I thought I'd talk briefly about two recent examples of this: using sonoluminescence as a tool to activate light-sensitive drugs, and the importance of causality in modelling light emission in structured environments.

The first observation of gravitational waves (2017 nobel prize for physics) opened up a new window into particle physics as well as astronomy. In particular gravitational waves can be produced from first order cosmological phase transitions that occur early in the Universe. Cosmological phase transitions play a key role in particle physics leading to the Higgs mechanism where electroweak symmetry is broken and the transition from the quark- gluon plasma to confined hadrons such as protons and neutrons. They also appear in many extensions of the standard model of particle physics such as grand unified theories and first order cosmological phase transitions are a vital ingredient in solutions to the matter anti-matter asymmetry. Observation of a stochastic gravitational wave background from a cosmological phase transition would be a discovery of new physics beyond the standard model of particle physics, because the standard model predicts the electroweak and QCD phase transitions to be smooth crossover transitions. In this colloquium I will give an overview of first order cosmological phase transitions and how they lead to gravitational wave predictions. This is a very active and open area of research with many unknowns and uncertainties, so I will highlight the limitations in our knowledge andexciting opportunities for new work to have a large impact.

We give a summary of our work on the dynamics of open system dynamics given by iterated quantum maps and give several examples of possible applications. Among others we discuss how the properties of the network can determine the asymptotic dynamics and point out the link between the asymptotic dynamics and the Jaynes principle. 

Since the foundational results of the BATSE satellite in the early 90s, gamma-ray bursts have been classified into two distinct populations using their observed duration. The discovery and observation of GRB afterglows has shown that these two populations are likely from two types of progenitors; the collapse of massive stars for long duration GRBs, associated with star forming galaxies and supernovae, and compact binary mergers for short duration GRBs. The merger origin of short GRBs is supported by the diversity of host galaxies, often without any star formation, the spatial offset of the GRB from the candidate host galaxies, and the (rarely observed due to its faintness) kilonova emission hidden within the rapidly fading afterglow. Additionally, a short GRB was temporally associated with the gravitational wave detected neutron star merger, GW170817. I will discuss the observation and analysis of two long duration GRBs, 211211A and 230307A, that have kilonova within their afterglow, and have offsets from their candidate host galaxies that are consistent with the short GRB population. These two, “new class”, merger origin GRBs have the clearest examples of kilonova emission within their afterglow when compared to the catalogue of other GRB-kilonova. For GRB 230307A, via JWST observations, we have obtained the unprecedented nebula phase spectroscopy of its kilonova. These spectra reveal the emission signatures of elements from r-process nucleosynthesis, with features consistent with each of the three r-process peaks. Merger origin long duration GRBs challenge the standard gamma-ray burst model and opens the door to a more diverse range of potential electromagnetic counterparts to gravitational wave detected neutron star mergers and may help us to understand the merger contribution to the heavy metal enrichment history of the Universe.

Shaping light fields in time, space, and polarization has become a versatile tool to explore fundamental optics effects and explore fruitful applications in various fields of photonics. In this talk, I will present two of our recent studies in this thriving branch of optics
At first, I will describe our recent results in structuring light in polarization, space, and wavelength. Through a combination of a polarization-dependent modulation in time and in orbital angular momentum, we are able to realize pulses of light, that are fully correlated in all three degrees of freedom, which we term spatio-spectral vector beams. We show that such beams have a complex polarization pattern over the wavelength spectrum as well as transverse angle. We further explore an interesting feature, namely that the degree of polarization of the field is only unveiled when the field is narrowly defined in space and wavelength, which is analog to non-separable quantum systems.
In the second part of the talk, I will discuss higher-order aberration effects that are natural to reflections of light with spatial structures such as phase vortices. In such scenarios, it was predicted that higher-order vortices split into a constellation of unit-charged vortices, a phenomenon termed as topological aberration. We were able to observe this phenomenon for the first time experimentally through the transformation of a vortex constellation upon reflection. We developed a general theoretical framework to study topological aberrations in terms of elementary symmetric polynomials of the coordinates of a vortex constellation. This mathematical abstraction, which we prove to be the physical quantity of interest, not only allowed us to verify the effect experimentally, but might also be applicable to vortex constellations of more complex structured light fields as well as other physical systems e.g. superfluids and Bose-Einstein condensates.

Sculpted light has emerged as the tool of choice to produce configurable and flexible confining potentials at the nano and micron-scales. Extensive research has been conducted on the use of structured light in fields such as quantum atom optics and optical tweezers. It provides means of production of ever more complex potential landscapes. Several methods have been used for production of these versatile potential landscapes and many applications have emerged. I will describe in my talk some of these application including studies of quantum turbulence on one hand and ballistic Brownian motion on the other.