VictorJuiz/thesis huggingface dataset:
Exploring the Fermi surfaces of novel quantum materials using high magnetic fields
Keywords: Quantum oscillations
Density functional theory

This thesis presents the results of torque magnetometry and resistivity measurements of the electronic structure of novel quantum materials, specifically using the techniques of quantum oscillations and angle-dependent magnetoresistance oscillations. Measurements of the Fermi surfaces of these materials, alongside comparisons to the electronic structure predicted by density functional theory calculations, can elucidate much about the novel physical properties they exhibit and the competing interactions which govern their phase diagrams.
The first system studied is the Iron-based superconductor FeSe1-xSx, an isoelectronically doped version of a system of much current interest, FeSe. Doping up to x = 0.2 is found to suppress the structural transition in this system entirely, with superconductivity continually present at low temperatures. Shubnikov-de Haas measurements across this range find a small quasi-two dimensional Fermi surface that increases in size and warping continuously with doping, with orbital dependent effective masses that do not change significantly within the orthorhombic phase.
The second material studied is the antiferromagnetic intermetallic CeZn11 which, featuring an unpaired 4f electron, is considered a possible candidate for heavy fermion behaviour. De Haas-van Alphen oscillations are seen once the antiferromagnetic phase is suppressed, and comparable frequencies of oscillation are measured in the non-magnetic analogue LaZn11, although with relatively smaller effective masses. GGA+U calculations, once magnetic breakdown is considered, match well the measured frequencies, confirming CeZn11 to be a localised moment system with the 4f electron well below the Fermi level.
The final material studied is the transition metal dichalcogenide IrTe2, which undergoes dimerisation upon cooling into a number of possible charge modulated structures. Low temperature de Haas-van Alphen measurements find multiple domains of a quasi-two dimensional Fermi surface, no longer perpendicular to the lattice planes. Angular-dependent magnetoresistance oscillations observe a similarly tilted quasi-one dimensional Fermi surface, again with many domains present. Together these measurements confirm the unusual dimensionality of the dimerised Fermi surface of IrTe2.
Measurement of equation of state of compressed hydrogen and deuterium
Keywords: deuterium
fusion
hydrogen
plasma physics
x-ray scattering
planetary structure
equation of state
warm dense matter

Detailed understanding of the equation of state of light elements such as the hydrogen isotopes in the warm dense matter (WDM) regime is essential for the modeling of the inner structure of many astrophysical objects, in particular Jovian planets as well as inertial confinement fusion (ICF) research. In these systems quantum degeneracy and strong inter-particle forces play an important role making its theoretical description extremely challenging.
The Omega laser was used to drive a planar shock wave in cryogenically cooled deuterium creating WDM conditions. We used a set of independent diagnostics to measure the thermodynamic conditions of WDM including velocity interferometry (VISAR), streaked optical pyrometry (SOP) and x-ray Thomson scattering (XRTS). With a narrow-band x-ray backlighter probe at backscattering geometry the spectrally resolved XRTS accessed the boundary of collective and non-collective regimes making our measurement sensitive to both electron temperature and density.
This work presents a full set of measurements of the thermodynamic properties for different laser intensity drives creating warm dense deuterium at various degrees of degeneracy and coupling. The measured electron densities and temperatures ranged between 0.2 and 2.15×1023 cm−3 and 0.6 − 20 eV respectively. The scattering measurement confirmed the findings from the VISAR and SOP data and together densityfunctional molecular dynamics (DFT-MD) simulations provides a novel self-consistent approach for an accurate characterization of the microscopic structure of WDM.
Complementary to the laser compression work, findings from project employing static compression hydrogen with the use of diamond anvil cells is also be presented. The first direct measurement of the local field correction to the Coulomb interactions in degenerate plasma was obtained from inelastic scattering (20 keV probe) at the Diamond Light Source synchrotron facility.
Measurement of the neutrino oscillation parameters sin²θ23, Δm²32, sin²θ13, and δCP in neutrino and antineutrino oscillation at T2K
Keywords: Neutrino physics
Neutrino
Antineutrino
Neutrino oscillation
CP violation

The T2K experiment is a long-baseline neutrino oscillation experiment, in which a muon neutrino beam is directed over a 295 km baseline from the J-PARC facility to the Super-Kamiokande detector. This allows neutrino oscillation to be studied in two channels: disappearance of νμ and appearance of νe. The T2K beam can be run either in neutrino or antineutrino configuration, for a neutrino beam which is predominantly composed of νμ or anti ¯νμ respectively.
This thesis presents the first oscillation analysis to combine neutrino-mode and antineutrino-mode data sets, giving the first ever sensitivity to the CP-violating phase δCP from T2K data alone, as well as the most precise T2K measurement of the other neutrino oscillation parameters. The analysis uses a Markov Chain Monte Carlo method to construct a sample from the Bayesian posterior distribution, from which the oscillation parameters of interest and their uncertainties are estimated. Data samples from the T2K near detector, ND280, are fit simultaneously with data from the far detector in order to reduce the uncertainty in the far-detector prediction.
When fitting the T2K data alone, the best-fit oscillation parameter values are sin2 θ23= 0.519+0.031-0.059, sin2 θ13= 0.0257+0.0106-0.0440, Δm232= 2.54+0.12-0.10 × 10-3eV2,and δCP=-1.91 rad. The 90% credible interval for δCP excludes values around π/2: δCP ∉ [0.38, 2.60] rad. When fitting the T2K data with a constraint on sin2 θ13 from measurements by reactor experiments, the best-fit oscillation parameter values are sin2 θ23= 0.519+0.061-0.029, sin2 θ13= +0.0014-0.0014, Dm232= 2.54+0.12-0.12 × 10-3eV2, and δCP=-1.72 rad. The 90% credible interval for δCP contains values δCP ∈ [-3.10,-0.17] rad, excluding the CP-conserving values 0 and ±π at 90% probability.
Experiments on multi-level superconducting qubits and coaxial circuit QED
Keywords: transmon
coaxmon
quantum computing
circuit quantum electrodynamics
coherence
higher levels
decoherence
superconducting qubits
artificial atom
3D cavity

Superconducting qubits are a promising technology for building a scalable quantum computer. An important architecture employed in the field is called Circuit Quantum Electrodynamics (circuit QED), where such qubits are combined with high quality microwave cavities to study the interaction between artificial atoms and single microwave photons. The ultra-strong coupling achieved in these systems allows for control and readout of the quantum state of qubits to perform quantum information processing. The work on circuit QED performed in this thesis consisted of realizing an experimental setup for qubit experiments in a new laboratory, investigating the coherence and decay of higher energy levels of superconducting transmon qubits and finally demonstrating a novel coaxial form of circuit QED.
Designing and building a 3D circuit QED setup involved the following main accomplishments: producing high quality 3D cavities; designing and installing the cryogenic microwave setup as well as the room temperature amplification and data acquisition circuitry; successfully developing a recipe for the fabrication of Josephson junctions; controlling and measuring superconducting 3D transmon qubits at 10mK. Several qubits were fully characterised and have shown coherence times of several microseconds and relaxation times up to 25μs.
Superconducting qubits in fact possess higher energy levels that can provide significant computational advantages in quantum information applications. In experiments performed at MIT, preparation and control of the five lowest states of a transmon qubit was demonstrated, followed by an investigation of the phase coherence and decay dynamics of these higher energy levels. The decay was found to proceed mainly sequentially with relaxation times in excess of 20μs for all transitions. A direct measurement of the charge dispersion of these levels was performed to explore their characteristics of dephasing. This experiment was also reproduced on a 3D transmon fabricated and measured in Oxford, where due to a higher effective qubit temperature a multi-level decay model including thermal excitations was developed to explain the observed relaxation dynamics.
Finally, a coaxial transmon, which we name the coaxmon, is presented and measured with a coaxial LC readout resonator and input/output coupling ports placed inline along the third dimension. This novel coaxial circuit QED architecture holds great promise for developing a scalable planar grid of qubits to build a quantum computer.
Investigating the interplay between cellular mechanics and decision-making in the C. elegans germ line
Keywords: stem cell
C. elegans
cell based modelling
numerical methods
simulation

The behaviour of individual cells must be carefully coordinated across a tissue to achieve correct function. In particular, proliferation and differentiation decisions must be precisely regulated throughout development, tissue maintenance, and repair. A better understanding of how these processes are controlled would have implications for human health; cancer is, after all, dysregulated proliferation, while regenerative medicine relies on being able to influence cell decisions accurately. To investigate such fundamental biological processes, it is common practice to use an experimentally tractable model organism. Here, we focus on the germ line of the nematode worm C. elegans, which provides opportunities to study organogenesis, tissue maintenance, and ageing effects. Despite the advantages of this organism as a biological model, certain questions about germ cell behaviour and coordination remain challenging to address in the lab. There is therefore a need for computational models of the germ line to complement experimental approaches.
In this thesis, we develop a new in silico model of the C. elegans germ line. Novel aspects include working in three dimensions, covering the late larval period, and integrating a logical model of germ cell behaviour into a wider cell mechanics simulation. Our model produces a reasonable fit to wild-type germline behaviour, and provides the first cell tracking and labelling predictions for the larval period. It also suggests two new biological hypotheses: 1) that “stretching” growth plays a significant role in gonadogenesis, and 2) that a feedback mechanism acts on the germ cell cycle to prevent overproliferation. Having introduced the full model, we address some technical questions arising from our work, namely: what is the effect of applying a more physically realistic force law?; and can simulation performance be improved by changing the numerical scheme? Finally, we use in silico modelling to compare a number of hypothesised germ line maintenance mechanisms. There, our results support a model with functionally equivalent germ cells undergoing at most infrequent, transient cell cycle arrests.
The linguistic elements of Old Germanic metre: phonology, metrical theory, and the development of alliterative verse
Keywords: Alliterative verse
Beowulf
Phonology
Resolution
Metrics
Syllabification
Fornyrðislag
Edda
Ljóðaháttr
Kaluza's law
Proto-Germanic

I examine those linguistic features of Old English and Old Norse which serve as the basic elements for the metrical systems of those languages. I begin with a critical survey of recent work on Old English metrical theory in chapter 1, which suggests that the four-position and word-foot theories of metre are the most viable current frameworks. A further conclusion of this chapter is that stress is not, as is often claimed, a core element of the metre. In chapter 2, I reassess the phonological-metrical phenomenon of Kaluza's law, which I find to be much more regular and widely applicable within B&emacr;owulf than has previously been recognized. I further argue that the law provides evidence that Old English phonological foot structure is based on a preference for precise bimoraism. In chapter 3, I examine the role of syllables in the Norse Eddic metre fornyrðislag, which supports a view of resolution and phonological feet similar to that found in Old English, though Norse prosody is much more tolerant of degenerate, light feet. I reconsider the other major Eddic metre, ljóðaháttr, in chapter 4, integrating the insights of Andreas Heusler and Geoffrey Russom to propose a new system of scansion for this notoriously recalcitrant verse form. This scansion provides important support for the word-foot theory, and suggests that linguistic elements larger than syllables or phonological feet play a crucial role in early Germanic verse. In the final chapter, I give a diachronic account of Germanic metre and relevant linguistic structures, arguing that the word-foot theory provides the best metrical framework for understanding the development of Germanic alliterative verse. This metrical system is linguistically supported by Germanic word structures and compounding rules, and interacts with bimoraic phonological feet, all of which have a long history in Proto- and pre-Germanic.
Ultrafast indoor optical wireless communications
Keywords: Beamsteering
Optical Wireless Communications
Ultrafast wireless communications
Adaptive optics
Localization and tracking systems
indoor wireless coverage
Spatial Light Modulators

Traffic from wireless and mobile devices is predicted to increase 10-fold between 2014 and 2019, surpassing wired data traffic by 2016. Given the expected radio frequency (RF) capacity crunch, this growing wireless demand will have to be met using a variety of new technologies exploiting other parts of the electromagnetic spectrum. Promising research areas include the Millimetre Band as well as Optical Wireless Communications (OWC).
Millimetre Band demonstrations have accomplished ultrafast multi-Gigabit links, making use of state-of-the-art fibre transmission systems. However, complex opto-electronic (OE) interfaces are required to convert the optical carrier into Millimetre wireless signals. To avoid these interfaces, an all-optical transparent network is proposed here, spanning over both the fibre and OWC domains, in order to deliver ultrahigh data rates to mobile end-users in indoor environments. This is supported by the recent deployment of fibre-to-the-home (FTTH) networks creating the potential for Terabit aggregate connections at the user’s doorstep.
Therefore, infrared fibre-wireless-fibre (FWF) links are studied to support data rates over 100 Gb/s in nomadic applications. The link coverage is achieved via narrow beam beamsteering over a wide field-of-view (FOV) using suitable localization and tracking techniques. The proposed model is inherently bidirectional and transparent, i.e. independent of the data rate and modulation format.
In this thesis, the potential for ultrafast wide coverage OWCs using SMF-based transceivers and coherent transmission is demonstrated. A record data rate of 418 Gb/s and 209 Gb/s with a wide FOV of θFOV=±30° and θFOV=±20°, respectively, is shown at a free space range of 3 m. To the best of our knowledge, this is the fastest demonstration of an indoor wireless link that offers practical room-scale coverage. The automated alignment of this FWF link is also demonstrated with the design and implementation a mm-accurate localization and tracking system. Finally, architectures for point-to-multipoint communications are explored in order to adapt the system to multiple users.
Producing Piers Plowman to 1475: author, scribe, and reader
Keywords: literature
history
piers plowman
manuscripts
medieval
textual history
scribes

My doctoral thesis, "Producing Piers Plowman to 1475: Author, Scribe, and Reader," charts a new material history of William Langland's fourteenth-century dream vision, Piers Plowman, from its earliest composition to the onset of print in England. The study is divided into three sections, which examine the production of Piers from three perspectives: textual history, manuscript circulation, and medieval reception. The first section of the thesis conducts a study of Langland's revisionary process, presenting a new theory of authorial revision from the A to B version that has important implications for our understanding of authorship in Piers Plowman and for the future editing of the poem. The second section transitions into an examination of the early circulation of the Piers manuscripts in various geographical and social milieux. It examines two case studies of manuscript circulation in the Southwest Midlands and East Anglia, linking them to regionalized networks of scribes and patrons. Finally, Section III moves into a discussion of the literary contexts in which Piers circulates, particularly in multi-text manuscripts, examining how the poem’s reception by a medieval audience affected its development as a literary text. This section treats production from a more theoretical standpoint, investigating the relationship between the poem's audience and the "production" of meaning in a social and historical context. As I will argue, each of these sections acts as an important frame of reference for understanding the multifaceted formation of Piers Plowman as a literary text and cultural landmark. In particular, the thesis emphasizes the importance of Piers's various contexts, from its textual genesis in the author's composition and revision to its circulation and reception in an unstable manuscript culture. It suggests that the people and the places that surrounded Piers Plowman in its early development fundamentally shaped the poem we have today.
Brain power: the political economy of higher education
Keywords: core voters
voter preferences
distributive politics
higher education
swing voters
policy preferences
voter mobilisation
voter conversion
turn out
voting power

This dissertation disputes conventional interpretations of the comparative political economy literature on higher education. In particular, I challenge the common assumption that access to higher education is structured by income. Instead, based on insights from the relevant psychology, sociology and economics literature, I argue that a child’s probability of entering higher education is predominantly a function of her abilities, and that her abilities are strongly related to her parents’ level of education. I develop a theory of the distributive politics of higher education solidly grounded in this relationship. The result of this model is the counter intuitive hypothesis that the initial expansions of higher education benefit the children of more highly educated parents. Moreover, more highly educated families are the net beneficiaries of free higher education and generous subsidies. Extensive survey evidence from Britain, Australia, Canada and Sweden of higher education policy preferences confirms this picture of the politics of higher education as a zero-sum distributive game between highly and lesser educated families. In order to analyse the consequences of these preference patterns for higher education policy, I develop a theoretical and empirical measure of voting power for multi-party systems. Voting power measures how many votes a party stands to gain from converting and mobilising voters by distributing resources from one group to another. Using data from 15 EU countries, I show that parliaments and cabinets, on average, stand to win more votes from pleasing highly educated voters than from targeting less educated voters. Furthermore, the conversion imperative is much stronger than the mobilisation imperative. Statistical analyses show that variations in the voting power of highly educated individuals over the government help to explain variations in higher education policy across countries and within countries over time. All in all, the theoretical and empirical analyses presented in this dissertation represent a significant contribution towards understanding the specific distributive politics of higher education, and the political economy of redistribution more generally.
Universal D-modules, and factorisation structures on Hilbert schemes of points
Keywords: Factorisation algebras
Chiral algebras
Stacks of etale germs
Hilbert schemes

This thesis concerns the study of chiral algebras over schemes of arbitrary dimension 𝑛.
In Chapter I, we construct a chiral algebra over each smooth variety 𝑋 of dimension 𝑛. We do this via the Hilbert scheme of points of 𝑋, which we use to build a factorisation space over 𝑋. Linearising this space produces a factorisation algebra over 𝑋, and hence, by Koszul duality, the desired chiral algebra. We begin the chapter with an overview of the theory of factorisation and chiral algebras, before introducing our main constructions. We compute the chiral homology of our factorisation algebra, and show that the 𝒟-modules underlying the corresponding chiral algebras form a universal 𝒟-module of dimension 𝑛.
In Chapter II, we discuss the theory of universal 𝒟-modules and 𝒪𝒪- modules more generally. We show that universal modules are equivalent to sheaves on certain stacks of étale germs of 𝑛-dimensional varieties. Furthermore, we identify these stacks with the classifying stacks of groups of automorphisms of the 𝑛-dimensional disc, and hence obtain an equivalence between the categories of universal modules and the representation categories of these groups. We also define categories of convergent universal modules and study them from the perspectives of the stacks of étale germs and the representation theory of the automorphism groups.