Framing the dark: theory and phenomenology of a non-minimally coupled dark matter fluid

The standard Lambda Cold Dark Matter (\u39bCDM) model has proven to be extremely powerful in predicting the evolution and formation of the structure we see in the Universe. However, this success comes at the price of accepting that the energy/matter content of the Universe is dominated by two unknown components: dark matter and dark energy. Moreover, in the case of dark matter some tension between simulations and observations exists at galactic scales, while in the case of dark energy long-standing theoretical issues are still unresolved, thus making the investigation of alternative models a powerful and necessary tool to improve the understanding of the Universe dynamics. In this thesis we study a modified gravity model for dark matter, investigating both its theoretical and phenomenological consequences. In particular, we consider a CDM model in which a dark fluid becomes non-minimally coupled to gravity at recent times and investigate and discuss how this modified picture may be able to address some of the issues the CDM paradigm is facing at small scales, while preserving the successes of the model at large scales. On a more formal level we investigate the properties of the Horndeski action under disformal metric transformation, providing the form of the transformations that leaves it invariant. More than a mathematical curiosity, this invariance represents a first step to formalize some recently notices relations between different models of dark energy, which may be seen as equivalent representation of the same fundamental theory

Internalist priorities in a philosophy of words

Words appear to be denizens of the external world or, at any rate, not wholly mental, unlike our pains. It is the norm for philosophical accounts of words to reflect this appearance by offering various socio-cultural conditions to which an adequate account of wordhood must cleave. The paper argues, to the contrary, that an adequate account of word phenomena need avert to nothing other than individual psychology along with potential external factors that in-themselves do not count as linguistic. My principal leverage will be that, by everyone’s lights, whatever words are, they are syntactically combinable and possess structural properties. But such conditions cannot be externally realised; instead, they are aspects of our internally realised cognitive capacity. It will also be argued, however, that the position is consistent with much of our common lore about words, albeit sans an externalist linguistic ontology

Modified Gravity and Cosmology

In this review we present a thoroughly comprehensive survey of recent work on modified theories of gravity and their cosmological consequences. Amongst other things, we cover General Relativity, Scalar-Tensor, Einstein-Aether, and Bimetric theories, as well as TeVeS, f(R), general higher-order theories, Horava-Lifschitz gravity, Galileons, Ghost Condensates, and models of extra dimensions including Kaluza-Klein, Randall-Sundrum, DGP, and higher co-dimension braneworlds. We also review attempts to construct a Parameterised Post-Friedmannian formalism, that can be used to constrain deviations from General Relativity in cosmology, and that is suitable for comparison with data on the largest scales. These subjects have been intensively studied over the past decade, largely motivated by rapid progress in the field of observational cosmology that now allows, for the first time, precision tests of fundamental physics on the scale of the observable Universe. The purpose of this review is to provide a reference tool for researchers and students in cosmology and gravitational physics, as well as a self-contained, comprehensive and up-to-date introduction to the subject as a whole.Comment: 312 pages, 15 figure

How dark is dark matter? Robust limits on dark matter - radiation interactions from cosmological observations

Extensions to the canonical LCDM model which incorporate elastic scattering between dark matter and Standard Model radiation predict the suppression of matter perturbations on small scales and modifications to the cosmic microwave background anisotropies. Studying these scenarios not only allows us to constrain the particle physics properties of dark matter, it also reveals if they can alleviate remaining tensions in cosmological data sets. In this context, the present thesis considers several aspects of dark matter-photon and dark matter-neutrino interactions. One central aspect of our work is the accurate description of additional scattering terms in the numerical solutions. In the context of dark matter-photon interactions, we demonstrate the robustness of earlier studies with respect to inconsistencies in the tight coupling approximation and to the negligence of the dark matter sound speed. Accounting for the latter, however, potentially tightens limits from large-scale structure observations for light dark matter candidates. Our updated constraints, derived from the Planck 2015 data release, are about 20% tighter than previous CMB limits in the most conservative case. We further extend dark matter-photon interactions to a mixed dark matter scenario in which two components, one collisional and one collisionless, contribute to the relic abundance. In particular a small fraction of interacting dark matter impacts the matter power spectrum in a fashion very similar to massive neutrinos. In this case, CMB data only imposes weak constraints on the interaction strength, and our Fisher forecast for the DESI survey predicts notably larger error margins on the neutrino mass. Dark matter-neutrino interactions alter the initial conditions and cause inconsistencies in the ultra-relativistic fluid approximation, which impact the matter power spectrum on small scales. Still, we can reinforce the validity of previous studies that neglected those effects. In addition to the canonical collisional damping, dark matter-neutrino interactions imply the suppression of structure by mixed damping. Indeed, our exploration of the parameter space reveals the relevance of mixed damping for observational constraints. To provide insight into the underlying physical processes, we derive an analytical approximation to the evolution of dark matter perturbations in the mixed damping regime, which accomplishes to capture all qualitative features of our full numerical results

An aesthetics of touch: investigating the language of design relating to form

How well can designers communicate qualities of touch? This paper presents evidence that they have some capability to do so, much of which appears to have been learned, but at present make limited use of such language. Interviews with graduate designer-makers suggest that they are aware of and value the importance of touch and materiality in their work, but lack a vocabulary to fully relate to their detailed explanations of other aspects such as their intent or selection of materials. We believe that more attention should be paid to the verbal dialogue that happens in the design process, particularly as other researchers show that even making-based learning also has a strong verbal element to it. However, verbal language alone does not appear to be adequate for a comprehensive language of touch. Graduate designers-makers’ descriptive practices combined non-verbal manipulation within verbal accounts. We thus argue that haptic vocabularies do not simply describe material qualities, but rather are situated competences that physically demonstrate the presence of haptic qualities. Such competencies are more important than groups of verbal vocabularies in isolation. Design support for developing and extending haptic competences must take this wide range of considerations into account to comprehensively improve designers’ capabilities

Variation and change in the vowel system of Tyneside English

PhD ThesisThis thesis presents a variationist account of phonological variation and change in the vowel system of Tyneside English. The distributions of the phonetic exponents of five vowel variables are assessed with respect to the social variables sex, age and social class. Using a corpus of conversational and word-list material, for which 32 speakers of Tyneside English were recorded, between 30 and 40 tokens per speaker of the variables (i), (u), (e), (o) and (3) were transcribed impressionistically and subclassified by following phonological context. The results of this analysis are significant on several counts. First, the speakers sampled appear to differentiate themselves within the speech community through the variable use of certain socially marked phonetic variants, which can be correlated with the sex, age and class variables. Secondly, the speakers style shift to a greater or lesser degree according to combinations of the three social factors, such that surface variability is reduced as a function of increased formality. Third, the overall pattern among the sample population seems to be one of increasing uniformity or convergence: it is speculated that social mobility among upper working- and lower-middle class groups may lead to accent levelling, whereby local speech forms are supplanted by supra-local or innovative intermediate ones. That is, the patterns observed here may be indicative of change in progress. Last, a comparison of the results for the (phonologically) paired variables (i u) and (e o) shows a strong tendency for Tyneside speakers to use these 'symmetrically', in that choice of variant in one variable predicts choice of variant in the other. It is suggested that the symmetry in the system is exploited by Tyneside speakers for the purposes of indicating social affiliation and identity, and is in this sense an extra sociolinguistic resource upon which speakers can draw. In addition, the variants of (3) are discussed with reference to the reported merger of this variable with (a); it is suggested that the apparent 'unmerging' of these two classes is unproblematic from a structural point of view, as the putative (3)—(o) merger appears never to have been completed.UK Economic and Social Research Council (award number R00429524350

Precis of neuroconstructivism: how the brain constructs cognition

Neuroconstructivism: How the Brain Constructs Cognition proposes a unifying framework for the study of cognitive development that brings together (1) constructivism (which views development as the progressive elaboration of increasingly complex structures), (2) cognitive neuroscience (which aims to understand the neural mechanisms underlying behavior), and (3) computational modeling (which proposes formal and explicit specifications of information processing). The guiding principle of our approach is context dependence, within and (in contrast to Marr [1982]) between levels of organization. We propose that three mechanisms guide the emergence of representations: competition, cooperation, and chronotopy; which themselves allow for two central processes: proactivity and progressive specialization. We suggest that the main outcome of development is partial representations, distributed across distinct functional circuits. This framework is derived by examining development at the level of single neurons, brain systems, and whole organisms. We use the terms encellment, embrainment, and embodiment to describe the higher-level contextual influences that act at each of these levels of organization. To illustrate these mechanisms in operation we provide case studies in early visual perception, infant habituation, phonological development, and object representations in infancy. Three further case studies are concerned with interactions between levels of explanation: social development, atypical development and within that, developmental dyslexia. We conclude that cognitive development arises from a dynamic, contextual change in embodied neural structures leading to partial representations across multiple brain regions and timescales, in response to proactively specified physical and social environment

The Democratization of Artificial Intelligence

After a long time of neglect, Artificial Intelligence is once again at the center of most of our political, economic, and socio-cultural debates. Recent advances in the field of Artifical Neural Networks have led to a renaissance of dystopian and utopian speculations on an AI-rendered future. Algorithmic technologies are deployed for identifying potential terrorists through vast surveillance networks, for producing sentencing guidelines and recidivism risk profiles in criminal justice systems, for demographic and psychographic targeting of bodies for advertising or propaganda, and more generally for automating the analysis of language, text, and images. Against this background, the aim of this book is to discuss the heterogenous conditions, implications, and effects of modern AI and Internet technologies in terms of their political dimension: What does it mean to critically investigate efforts of net politics in the age of machine learning algorithms

The Democratization of Artificial Intelligence: Net Politics in the Era of Learning Algorithms

After a long time of neglect, Artificial Intelligence is once again at the center of most of our political, economic, and socio-cultural debates. Recent advances in the field of Artifical Neural Networks have led to a renaissance of dystopian and utopian speculations on an AI-rendered future. Algorithmic technologies are deployed for identifying potential terrorists through vast surveillance networks, for producing sentencing guidelines and recidivism risk profiles in criminal justice systems, for demographic and psychographic targeting of bodies for advertising or propaganda, and more generally for automating the analysis of language, text, and images. Against this background, the aim of this book is to discuss the heterogenous conditions, implications, and effects of modern AI and Internet technologies in terms of their political dimension: What does it mean to critically investigate efforts of net politics in the age of machine learning algorithms

Language Science Meets Cognitive Science: Categorization and Adaptation

Questions of domain-generality—the extent to which multiple cognitive functions are represented and processed in the same manner—are common topics of discussion in cognitive science, particularly within the realm of language. In the present dissertation, I examine the domain-specificity of two processes in speech perception: category learning and rate adaptation. With regard to category learning, I probed the acquisition of categories of German fricatives by English and German native speakers, finding a bias in both groups towards quicker acquisition of non-disjunctive categories than their disjunctive counterparts. However, a study using an analogous continuum of non-speech sounds, in this case spectrally-rotated musical instrument sounds, did not show such a bias, suggesting that at least some attributes of the phonetic category learning process are unique to speech. For rate adaptation, meanwhile, I first report a study examining rate adaptation in Modern Standard Arabic (MSA), where consonant length is a contrastive part of the phonology; that is, where words can be distinguished from one another by the length of the consonants that make them up. I found that changing the rate of the beginning of a sentence can lead a consonant towards the end of the sentence to change in its perceived duration; a short consonant can sound like a long one, and a long consonant can sound like a short one. An analogous experiment examined rate adaptation in event segmentation, where adaptation-like effects had not previously been explored, using recordings of an actor interacting with a touchscreen. I found that the perception of actions can also be affected by the rate of previously-occurring actions. Listeners adapt to the rate at the beginning of a series of actions when deciding what they saw last in that series of actions. This suggests that rate adaptation follows similar lines across both domains. All told, this dissertation leads to a picture of domain-specificity in which both domain-general and domain-specific processes can operate, with domain-specific processes can help scaffold the use of domain-general processing