Engaging Universities in the Regional Integration Project in Southern Africa

The aim of this paper is to explore the potential for engaging universities in promoting greater regional integration in the southern African region, with the intention of prompting further conversation and debate around the role of universities in supporting regional initiatives

Generalized Gibbs Ensembles in Discrete Quantum Gravity

Maximum entropy principle and Souriau's symplectic generalization of Gibbs states have provided crucial insights leading to extensions of standard equilibrium statistical mechanics and thermodynamics. In this brief contribution, we show how such extensions are instrumental in the setting of discrete quantum gravity, towards providing a covariant statistical framework for the emergence of continuum spacetime. We discuss the significant role played by information-theoretic characterizations of equilibrium. We present the Gibbs state description of the geometry of a tetrahedron and its quantization, thereby providing a statistical description of the characterizing quanta of space in quantum gravity. We use field coherent states for a generalized Gibbs state to write an effective statistical field theory that perturbatively generates 2-complexes, which are discrete spacetime histories in several quantum gravity approaches

Statistical Equilibrium in Quantum Gravity: Gibbs states in Group Field Theory

Gibbs states are known to play a crucial role in the statistical description of a system with a large number of degrees of freedom. They are expected to be vital also in a quantum gravitational system with many underlying fundamental discrete degrees of freedom. However, due to the absence of well-defined concepts of time and energy in background independent settings, formulating statistical equilibrium in such cases is an open issue. This is even more so in a quantum gravity context that is not based on any of the usual spacetime structures, but on non-spatiotemporal degrees of freedom. In this paper, after having clarified general notions of statistical equilibrium, on which two different construction procedures for Gibbs states can be based, we focus on the group field theory formalism for quantum gravity, whose technical features prove advantageous to the task. We use the operator formulation of group field theory to define its statistical mechanical framework, based on which we construct three concrete examples of Gibbs states. The first is a Gibbs state with respect to a geometric volume operator, which is shown to support condensation to a low-spin phase. This state is not based on a pre-defined symmetry of the system and its construction is via Jaynes' entropy maximisation principle. The second are Gibbs states encoding structural equilibrium with respect to internal translations on the GFT base manifold, and defined via the KMS condition. The third are Gibbs states encoding relational equilibrium with respect to a clock Hamiltonian, obtained by deparametrization with respect to coupled scalar matter fields.Comment: v2 31 pages; typos corrected; section 2 modified substantially for clarity; minor modifications in the abstract and introduction; arguments and results unchange

Thermal quantum gravity condensates in group field theory cosmology

The condensate cosmology programme of group field theory quantum gravity has produced several interesting results. The key idea is in the suggestion that a macroscopic homogeneous spacetime can be approximated by a dynamical condensate phase of the underlying microscopic system of an arbitrarily large number of candidate quanta of geometry. In this work, we extend the standard treatments in two ways: by using a class of thermal condensates, the coherent thermal states, which encode statistical fluctuations in quantum geometry; and, by introducing a suitable class of smearing functions as non-singular, well-behaved generalisations for relational clock frames in group field theory. In particular, we investigate an effective relational cosmological dynamics for homogeneous and isotropic spacetimes, extracted from a class of free group field theory models, and subsequently investigate aspects of its late and early times evolution. We find the correct classical limit of Friedmann equations at late times, with a bounce and accelerated inflationary expansion at early times. Specifically, we find additional correction terms in the evolution equations corresponding to the statistical contribution of the new thermal condensates in general; and, a higher upper bound on the number of e-folds, even without including any interactions

Evaluation of pulse wave analysis to assess coronary artery disease

Conventional risk factors for cardiovascular disease, such as age, gender, hyperlipidaemia and hypertension are useful clinical markers of coronary artery disease (CAD) in asymptomatic patients or those without a prior history of atherosclerosis. In patients referred for a cardiology opinion, modification of risk factors by lifestyle changes and cardiac medications as well as confounding co-morbidities limit the value of these markers. Patients are often referred for diagnostic coronary angiography to determine the presence and severity of CAD, stratify the risk of future events and determine appropriate management. Despite the use of a variety of tests to best identify those requiring angiography, up to half of all patients referred do not have significant disease. Pulse wave analysis (PWA) is a novel method to derive indices of central (aortic) blood pressure and arterial stiffness. Pressure waveforms are obtained non-invasively from the radial artery using a simple tonometry method and have been shown to correlate with clinical outcomes and cardiovascular events in selected populations. This thesis will explore, for the first time, the clinical potential for PWA as a non-invasive marker of CAD in an unselected contemporary cohort of patients referred for elective coronary angiography. The main hypotheses tested are first that PWA is a suitable tool for clinical use, including those with cardiac and non-cardiac co-morbidities and second that abnormalities of PWA are independent predictors of the presence and severity of CAD. Data have been derived from a prospective, protocol-driven, multi-centre cohort of 550 patients recruited from 2006-8. Results suggest that PWA has a useful clinical role in stratifying the risk of coronary disease. PWA variables were independent of conventional blood pressure measurement and superior to baseline risk factors, biomarkers and other non-invasive tests