VictorJuiz/thesis huggingface dataset:
Analysis of various estimators for multi-dimensional Zakai equations
Keywords: SPDE
Monte Carlo
Zakai equation
Finite difference

We first consider a one-dimensional stochastic partial differential equation (SPDE) of Zakai type describing a large credit portfolio. Specifically, we construct estimators of linear functionals of the solution from an implicit Milstein scheme on a space-time mesh. We compare the complexity of a multi-index Monte Carlo (MIMC) approach with the multilevel Monte Carlo (MLMC) method of Giles and Reisinger (2012), and find, by means of Fourier analysis, that the MIMC method has slightly improved complexity O(ε-2|log ε|) for a root mean square error (RMSE) ε if a carefully adapted discretisation is used.
Then, we propose an implicit finite difference scheme for a two-dimensional parabolic SPDE of Zakai type, based on a Milstein approximation to the stochastic integral and an alternating direction implicit (ADI) discretisation of the elliptic term. We prove its mean-square stability and convergence in L2 of first order in time and second order in space, by Fourier analysis, in the presence of Dirac initial data.
Next, we analyse the accuracy and computational complexity of estimators for linear functionals of the solution to the 2-d SPDE, coupled with the sparse combination technique and MLMC. We find, by detailed Fourier analysis, that for a RMSE ε, MLMC with sparse combination has the optimal complexity O(ε-2), whereas MLMC on regular grids has O(ε-2(log ε)2), standard MC with sparse combination O(ε-7/2(|log ε|)5/2), and MC on regular grids O(ε-4). We give a discussion of the higher-dimensional setting without detailed proofs, which suggests that MLMC with sparse combination always leads to the optimal complexity.
Finally, we consider a particular two-dimensional SPDE with fast mean-reverting volatility on a timescale O(ε-1), and study the small ε asymptotics. We find an asymptotic expansion of the solution to the SPDE as ε → 0 and conclude from numerical experiments the convergence order 1=2 of the leading term and order 1 after inclusion of the first correction term.
Educational expansion, skills diffusion, and a new dimension of the OED triangle
Keywords: educational credentials
social closure
skills
human capital
labour market outcomes
meritocracy
parental education
signalling

Among wide-ranging functions of education, sociologists have paid close attention to its role in social stratification and mobility. While research has promoted our understanding of the association between origins, education, and destinations (OED triangle), the distinction between educational credentials and skills has been largely overlooked at both individual and societal levels. This paper thus empirically investigates the OED association in consideration of educational specifications (the combination of credentials and skills that individuals possess) and the degree of skills diffusion (the proportion of highly skilled people in a given society), which is a different societal condition from educational expansion that has been quantified by the share of highly educated people. Multilevel logistic regression analyses, using internationally comparable data for approximately 30,000 individuals in 26 OECD countries, reveal that educational credentials play more significant roles, as compared with skills, in forming the OED triangle. This supports the soundness of conventional approach focused on educational qualifications. Nevertheless, whereas credentials are likely to lose their economic returns in societies where the degree of educational expansion is relatively high, skills are not devalued even though their scarcity diminishes due to the higher extent of skills diffusion. Meanwhile, the impact of origins becomes smaller in association with the larger share of highly skilled people as well as that of highly educated people in a nuanced way. This suggests that what we have understood as the consequence of educational expansion is significantly shaped by skills diffusion. It is particularly important to note that, while educational expansion undermines the contribution of origins whilst penalising highly educated people, skills diffusion operates as an equaliser without diminishing rewards for high skills. This implies that skills diffusion is the key to realising meritocracy. I argue that these perspectives markedly contribute to elucidating the nuanced OED triangle and broader social mechanisms.
Crime and equality, or crime and punishment?
Keywords: Inequality
Redistribution
Political science
Political economy
Crime

Despite its significance as a social, economic and—as I argue below—fundamentally political phenomenon, crime remains a largely overlooked topic in political economy. This dissertation argues that this represents an unfortunate omission. Over the pages that follow, I analyse the political implications of crime and fear of crime for the politics of inequality and redistribution. Modelling fear of crime as a negative externality of inequality, I argue that its consequences depend on who the criminals are: building on work in social psychology, I find that the identity of those who are perceived as likely perpetrators of crime significantly affects how criminal behaviour is interpreted. This comes with important implications for views about how crime as a social problem can (and should) be solved. Using a combination of observational data from Western Europe and the US, together with the results from a laboratory experiment conducted in Oxford, I first demonstrate that there exists a robust and systematic positive relationship between the local level of income inequality and fear of crime. In a second step, I show that shared group membership—manifested empirically as low population heterogeneity—facilitates situational explanations of crime, including poverty, while divergent identities promote dispositional attributions unrelated to inequality. As a result, while fear of crime in homogenous contexts is associated with a significant increase in demand for redistribution, particularly among high-income voters, I find no parallel effect in settings that are more diverse. The opposite relationship holds true for support for harsher punishment and law enforcement spending: whereas fear of crime increases support for such policies in settings that are sufficiently heterogenous, the same does not hold true when the level of population heterogeneity is lower. This finding both challenges previous accounts of the relationship between inequality, fear of crime and support for redistribution, and helps to explain cross-national differences in criminal justice policy.
Reliable automatic model reduction combining a posteriori error analysis and a posteriori model reduction
Keywords: a posteriori error analysis

Mathematical models are used for simulations and predictions of various phenomena and processes that can be translated into mathematical language. Nowadays, with easy access to powerful computers and specialised software, even complicated models can be handled. Model output can be generated even by users that may not have specialised mathematical training. A consequence of the increase in complexity of the models on the one hand, and the relative ease of numerical output generation on the other hand, can be a loss of insight into the mathematical model. One way to regain this is to reduce the original model to a simpler form that will nevertheless capture the key features of the model and elucidate the processes that are modelled, especially those that are of interest to the user.
In this thesis I develop a model reduction algorithm that is based on a technique borrowed from finite element methods. An a posteriori error estimate, where the error is defined as the difference between the unknown solution and a FE approximation thereof, is used to ensure that the mesh on the computational domain is fine enough such that the discretised scheme approximates the differential operator sufficiently accurately. Model reduction on the other hand uses an a posteriori error estimate, where the error is defined as the difference between the solutions to the original model and a reduced model, to generate a differential operator that is a close enough approximation of the original operator.
The main research chapter focuses on the mathematical analysis that this automated method entails. The model reduction technique is then applied to model problems to validate the numerical methods that are employed. An enzyme kinetic reaction model is discussed in detail as the application of the developed model reduction method satisfies the aim of this thesis to a great extent. In particular, I can show with that example that the reduced models which were automatically generated correspond to those obtained by asymptotic analysis. The same elucidation of the processes that are modelled could therefore be achieved with the automatic model reduction technique as with methods that usually need considerable mathematical expertise.
Psycho-social dynamics of shame in poverty: a South Korean case study
Keywords: psycho-social dimension
social policy
poverty
shame
cultural discourse
modern capitalism

Poverty studies worldwide have continuously demonstrated that poverty entails not only material hardships but also other non-material hardships, such as shame. Yet, a substantive empirical investigation of why and how shame is experienced in poverty and its relevance for social policy interventions has been significantly lacking in the literature. Accordingly, this thesis documents an in-depth empirical investigation of an increasingly significant, yet under-researched, psycho-social dimension of shame in poverty. Acknowledging the limitations of focusing either on the individual or the social level processes alone in poverty and shame research, it employs a psycho-social approach that takes a comprehensive account of the dual dimensions of shame. Empirical investigations are conducted with three different qualitative research methods (in-depth interviews with people living in poverty, sociological discourse analysis of popular films, and social policy analysis of the social assistance programme in South Korea), together with a historical contextualization of the empirical findings with secondary historical sources. Taking South Korea as a case study, it offers an empirically-based theoretical framework that explains the root causes, working mechanisms and impacts of shame in poverty, and the fundamental nature of the association between poverty and shame. It demonstrates that the current psycho-social dynamics of shame in poverty is a contemporary phenomenon underpinned by the socio-relational conditions that emerged from the major socio-historical shift to modern capitalism. The social level dynamics are shown to equally manifest in the personal level working mechanisms and subsequent impacts of shame in poverty. The findings show that in order for the anti-poverty social assistance in South Korea to continue promoting the improvement of people’s lives via their own self-agency, its design and implementation should equally be geared toward improving people’s self-agency rather than undermining it as it currently stands.
The illusion of solution? The politics of Jakarta’s quest to achieve water security
Keywords: Jakarta
Seawall
Historical institutionalism
Infrastructure
Political ecology
Water security
Urban water

The increasing number of large water infrastructures built or planned worldwide denotes the (re)turn to a hydraulic mission in water management. Infrastructures are pursued mainly for water supply augmentation and flood control, that is, delivering water security for the people especially in packed urban areas. Jakarta, the capital city of Indonesia, has pressing water issue as the city is experiencing land subsidence. Combined with sea level rise and perennial flooding problem, the city’s risk of sinking is extremely high. Following a major flood in 2013, the Government of Indonesia launched the NCICD (National Capital Integrated Coastal Development) plan to close Jakarta Bay with a 32-km length offshore sea wall for flood control defence. The plan also includes 5,100 hectares of land reclamation (located between the coastal line and the seawall), which was said, to fund the seawall construction. Such a megaproject whose total costs is estimated at USD 40 billion will significantly alter the biophysical as well as the social landscape of Jakarta. This thesis investigates the socio-political dynamics behind this megastructure from historical institutionalism and political ecology lenses, in which both anchored on power relations. Framing the overall discussion using ‘water security’ approach, it asks: How do relations of power drive large infrastructure investments in Jakarta, and how does this contribute and respond to the problem of water security?
Data collection primarily included 48 key informant interviews, around 400 newspaper articles and secondary data (archives and policy documents). In order to analyse these diverse data sources, I employed three types of data analyses accordingly: historical analysis for historical data, thematic analysis for interviews and policy documents, and discourse analysis for newspaper articles. This research reveals that NCICD has advanced the infrastructural pathway in Jakarta’s flood policy which has been established since the colonial times. NCICD as a contemporary project is, thus, a product of the past. Furthermore, rather than dealing with complex institutional challenges associated with multiple water sectors, the government instead focuses on the seawall, which only deals with the flooding issue as a symptom of sinking, rendering the highly political issue apolitical. Reflecting on the power asymmetries manifested in NCICD and situating them on broader literature on water security, I conclude that the politics of water security, in the context of water hazards, is the politics of fear and in consequently meeting demand for security through the prescription of infrastructure. Fear is built from memories of past floods and ultimately from the construction of future uncertainties, where our knowledge is limited.
Algorithmic explanations: to become a mockingbird
Keywords: algorithmic profiles
explainable machine learning
transparency

As algorithms are increasingly used to make potentially life-altering decisions the importance of ensuring they meet certain standards of fairness, accountability, and transparency is becoming paramount. Complex models that are poorly understood are susceptible to bias, reliance on protected or irrelevant features, and adversarial examples. This concern has spawned interest in explainable and interpretable algorithms which allow humans to understand algorithmic decisions. Running parallel to this issue is an increasing reliance on algorithmically generated profiles to target advertisements online. Often these profiles are built on sensitive characteristics, without user knowledge or means of recourse. They can influence user perceptions of self, alter the content users are exposed to, and reveal to other parties characteristics which users have chosen not to share. This project aims to increase user autonomy and privacy online by leveraging techniques in explainable machine learning.
This work begins by creating a prototype tool called Mockingbird that builds more than twenty algorithmically generated profiles based on Twitter data. These profiles are created using various techniques, including lexicons, neural networks, and Gaussian Processes. Mockingbird offers explanations for most of these profiles, primarily using a post-hoc explanatory tool. Finally, using synonym suggestions and techniques used to generate adversarial examples, Mockingbird gives users suggestions on how to alter their tweets in order to change their algorithmic profiles. Mockingbird is novel in combining profiles, explanations, and tools to change algorithmic profiles.
The system was tested through several (n = 6) lab experiments to gauge user response to explanations and willingness to alter their data. It appears that users are generally not concerned about their algorithmic profiles when used for advertising, but would be much more concerned in higher stakes applications. Users were also unwilling to change their existing data to control algorithmically generated profiles, viewing the necessary changes as too disruptive to how they use social media. This work points to avenues of further research focusing explicitly on editing social media data to influence high stakes decisions such as job, visa, and loan applications.
Derogation and the scope of the jus cogens norm in the jus ad bellum
Keywords: Jus cogens
Derogation

It is widely accepted that there is a jus cogens norm in the jus ad bellum. Yet uncertainty exists as to its scope, due to the existence of two exceptions to the prohibition on the use of force: self-defence and force authorised under the UN Charter. This dissertation aims to identify the jus cogens norm in the jus ad bellum by clarifying the meaning of ‘derogation’ in the context of jus cogens norms. In doing so, this dissertation addresses three questions: 1) what does it mean to say that a norm permits no derogation?; 2) do exceptions derogate from jus cogens norms?; and 3) how do the exceptions to the prohibition on the use of force affect the scope of the jus cogens norm in the jus ad bellum?
A jus cogens norm is identified as a norm of general international law ‘accepted and recognised by the international community of States as a whole as a norm from which no derogation is permitted’. Yet scholars understand ‘derogation’ in different ways: a ‘narrow’ view understands derogations as attempts to contract out of the jus cogens norm inter se, while a ‘broad’ view understands derogations as any norm that makes conduct inconsistent with the jus cogens norm lawful. On the broad view, there can be no exceptions to jus cogens norms.
It is argued that to say a norm permits no derogation means that there can be no lawful conduct inconsistent with obligations arising under that norm. As a result, any apparent ‘exceptions’ to jus cogens norms must be limitations on the scope of that norm. Thus, neither force lawfully authorised under the Charter nor force lawfully used in self-defence is prohibited by the jus cogens norm in the jus ad bellum. Such uses of force are defined and regulated by non-jus cogens norms, which are recognised by the jus cogens norm without forming part of it.
Force and possibility: a study in the theory of reasons
Keywords: normativity
reasons

This thesis is a study in the theory of reasons. In the main, it comprises three chapters that investigate a single question from different angles, namely, the question of what it is that makes reasons possible.
In Chapter 1, I propose a theory of what makes reasons possible. The theory progresses by defending a version of the thesis that ought implies can against an argument by John Gardner. What emerges from this defence is a formal model of possibility for facts that qualify as reasons for action. This contributes a new analytical test to the existing literature on normativity in respect of the question of what it is for a fact to be a reason.
In Chapter 2, I take up the question of whether legal rules are possible reasons for action. They are, indeed, commonly regarded in this way. Yet are such rules reasons for action themselves (the reflexivity thesis) or is a statement of a rule a way of paraphrasing reasons that we may already have (the paraphrastic thesis)? I argue for a version of the paraphrastic thesis.
In Chapter 3, I examine an influential methodology in the philosophy of law that underpins some influential theories on how legal rules can be possible reasons for action. I focus specifically on conceptual analysis as the methodology behind the requirement of compliance in Joseph Raz’s theory of mandatory norms. This requirement holds that if such norms are to be reasons, then they must allow for the possibility that one can do as a reason requires one to do because it requires one to do it. I argue against this view, holding that the requirement is impossible on methodological grounds.
What unifies the chapters of this thesis is a concern for what makes reasons possible. The take-home message is threefold. First, not all possible facts are possible reasons (Chapter 1). Second, legal rules are not themselves possible reasons (Chapter 2). And third, if we misuse the methods of conceptual analysis, we will end up with impossible reasons on our hands (Chapter 3). My tactic is to begin broadly by examining facts as possible reasons, then narrow down to one kind of reasons, namely, legal ones, and then step back to diagnose one source of impossible reasons.
Dynamics underlying Plasmodium vivax mitochondrial genome diversity across the Eastern Hemisphere
Keywords: historic epidemiology
phylogenetics
human migration
global distribution
vector disease
mitochondrial
malaria

Plasmodium vivax (Pv) malaria is a human infecting blood parasite distributed widely across both tropical and temperate regions. In order to increase the understanding of past dynamics influencing its current distribution, this thesis explores its origins, spread and evolutionary past through diversity and evolution of the mitochondrial genome. Exploring several different factors that would have affected its dispersal, including mosquito vector species and geographic distance, the main focus of Chapter 2 is on understanding when and with which past human migrations it spread across the continents of the Eastern Hemisphere. A special emphasis on the Melanesian region is included in Chapter 3, which shows considerable diversity in human populations and cultures, and has high incidence of all four species of human infecting malarias (P. vivax, P. falciparum, P. malariae, P. ovale). Although previous publications indicated an especially high level of diversity in Pv mitochondrial genomes in Melanesia; in this study it is shown to be a sampling artefact due to denser sampling. In both chapters a novel cross-disciplinary data comparison is undertaken, matching Pv mitochondrial genome phylogeny and population genetics with modern human mitochondrial genome data, human and hominid archaeological data, archaeological data from human commensal species and phylogenetic data from human associated diseases. Results indicate that not only the current Melanesian Pv but also the Pv strains found across the Asian continent to the east of India were likely introduced by the first wave of anatomically modern humans (Homo sapiens) to leave Africa. The strong patterning seen across this eastern region has ostensibly been shaped not only by relatively stable human populations for the last several thousand years, but is also associated with a strong regional heterogeneity of mosquito vector species and clades. In contrast, the present study confirms previously observed homology in Pv mitochondrial genetics from India to the west. Presumably the homology is due to increased human population movement and contact between the western regions, as well as greater overlap in mosquito vector species across the region, as shown in this study. Even so, with the addition of data from new sites across the western half of the Eastern Hemisphere, including samples from central and western Asia, there is a detection of low levels of population diversity. Lastly, Chapter 4 gives an overview of the applications of different genetic markers used in malaria research over time, reviewing the continued value of using mitochondrial DNA, on its own and in combination with other available genetic data – in an age of whole genome sequencing.