Review on possible gravitational anomalies

This is an updated introductory review of 2 possible gravitational anomalies that has attracted part of the Scientific community: the Allais effect that occur during solar eclipses, and the Pioneer 10 spacecraft anomaly, experimented also by Pioneer 11 and Ulysses spacecrafts. It seems that, to date, no satisfactory conventional explanation exist to these phenomena, and this suggests that possible new physics will be needed to account for them. The main purpose of this review is to announce 3 other new measurements that will be carried on during the 2005 solar eclipses in Panama and Colombia (Apr. 8) and in Portugal (Oct.15).Comment: Published in 'Journal of Physics: Conferences Series of the American Institute of Physics'. Contribution for the VI Mexican School on Gravitation and Mathematical Physics "Approaches to Quantum Gravity" (Playa del Carmen, Quintana Roo, Mexico, Nov. 21-27, 2004). Updates to this information will be posted in http://www.lsc-group.phys.uwm.edu/~xavier.amador/anomalies.htm

A quantum electron star

We construct and probe a holographic description of state of matter which results from coupling a Fermi liquid to a relativistic conformal field theory (CFT). The bulk solution is described by a quantum gas of fermions supported from collapse into the gravitational well of AdS by their own electrostatic repulsion. In the probe limit studied here, the Landau quasiparticles survive this coupling to a CFT.Comment: 8 pages, 7 figure

Higher Education, Inequality and the Public Good in Four African Countries: Ghana, Kenya, Nigeria and South Africa: Report of Johannesburg Workshop, 22-24 May 2017

This report provides a synthesised overview of the deliberations of the Project Workshop held in Johannesburg, South Africa from 22 to 24 May 2017 for the Economic and Social Research Council (ESRC) Newton/National Research Foundation (NRF) funded project, Higher Education, Inequality and the Public Good in four African countries: Ghana, Kenya, Nigeria and South Africa. The Workshop had two main purposes. As the first face-to-face meeting of the project since its start-up in December 2016, it was designed to provide an opportunity for in-depth planning by the full, cross-country research team, particularly towards the refinement of the research steps and instruments, as well as the further development of the first set of research outputs. In addition, the Workshop was structured to include on the second day a Stakeholder Workshop. This day was aimed at bringing together key higher education stakeholders from the participating countries to engage with them around the conceptual and contextual framing of the project and to strengthen the research design. The three days were therefore designed to enable more in-depth planning for going forward with the project and to begin to facilitate stakeholder involvement in the research. This report is aimed at providing an overview of the proceedings over the three days and, most importantly, drawing out the emerging issues from the Workshop for the project. It is therefore intended as both a record of key milestones within the project process and as a tool to assist in its further development and implementation. It has been organised into two main sections. The first discusses important themes that emerged out of the planning process and stakeholder engagement that are important for the project going forward, particularly towards deepening the conceptual thinking around the project, refining its research design and strengthening the planned research outputs. Discussion on and agreements reached on the next steps that need to be taken in the project are outlined in the second section. Attached to the report are also a number of appendices related to the workshop process and its outcomes

Feasibility of using a flat bottom electrode for PEA space charge measurement on mini-cables under high temperatures

Pulsed Electro-Acoustic (PEA) apparatus has been developed to measure the space charge distribution inside XLPE based mini-cable insulation. The technique relies on the acoustic contact between the cylindrical cable surface and a flat aluminium plate to couple the acoustic waves to the sensor. This work addresses the feasibility of using this technique over a temperature range of 25°C to 70°C. The results demonstrate that increasing the temperature under constant clamping force causes the cable insulation to soften and distort increasing the contact area and signal from the PEA apparatus. However on subsequent cooling to 25°C the mechanical distortion remains frozen-in with little change to the contact area. For reproducible space charge measurements it is necessary to first condition the cable sample by taking the cable and PEA through a temperature cycle before application of the applied voltage

A system for PEA space charge measurement on HVDC mini-cables under different isothermal temperatures: Influence of cable clamping force on PEA measurements on HVDC mini-cables

A Pulsed Electro-Acoustic (PEA) apparatus has been developed to measure the space charge distribution inside cable insulation. The technique relies on acoustic contact between the cylindrical cable surface and a flat aluminium plate to couple the acoustic waves to the sensor. This work addresses the practical issue of the clamping force required to maintain good contact and how this may alter the measured space charge distribution. Space charge measurements on mini-cables (model cables)were carried out over a wide range of clamping force and additionally a finite-element simulation model has been developed to model mechanical deformation of mini-cables and provide data that cannot be easily obtained from experiments. A clamping force range for reproducible measurements at room temperature has been determined by comparing results from a group test on a mini-cable

Strong subadditivity and the covariant holographic entanglement entropy formula

Headrick and Takayanagi showed that the Ryu-Takayanagi holographic entanglement entropy formula generally obeys the strong subadditivity (SSA) inequality, a fundamental property of entropy. However, the Ryu-Takayanagi formula only applies when the bulk spacetime is static. It is not known whether the covariant generalization proposed by Hubeny, Rangamani, and Takayanagi (HRT) also obeys SSA. We investigate this question in three-dimensional AdS-Vaidya spacetimes, finding that SSA is obeyed as long as the bulk spacetime satisfies the null energy condition. This provides strong support for the validity of the HRT formula.Comment: 38 page

Conceptualising Higher Education and the Public Good in Ghana, Kenya, Nigeria, and South Africa

Higher education has been the object of policy attention in sub-Saharan Africa in recent years. It has been seen as key to unlocking the potential of the youth bulge, responding to the demands of a growing middle class and to transforming commodities-based economies into knowledge societies (World Bank 2009; Cloete, Maassen & Bailey 2015; Chuks, 2017). Yet despite significant expansions of enrolment – including widening participation by women, major barriers to access exist, reflecting inequalities based on class, gender, geographical location, ethnicity, religion, language and disability (AAI 2015; Morley & Lugg 2009; Morley & Croft, 2011). There are quality challenges in relation to teaching and learning, research, and governance. While some comment on a ’renaissance in African higher education’ (Higgs, 2016), and others on the effects and framings of colonial epistemicides (Nyamnjoh, 2012) key questions abound about relevance and power relations highlighting the need to decolonise the curriculum, structure, organisation and cultures of universities. The student protests in South Africa from 2015 highlighted problems of access and funding, but these are not isolated events. They expose an unresolved colonial legacy in these higher education systems. These processes raise questions not only of the public good relevance of higher education - beyond the obvious advantages conferred on those who manage to go to these institutions – but also of how higher education and its relationship with society may be conceptualised given these contexts (Lebeau and Milla, 2008; Mamdani, 2017). An overarching question is who is defining the public good and how? While many of the above issues are global e.g. universities throughout Latin America, Australasia, Asia and Europe are involved in similar debates and protests, this paper explores the relationship between higher education and the public good in the sub- Saharan African context through a consideration of some connections and disconnections. There appear to be two distinct ways in which higher education and the public good have been conceptualised are discussed. Firstly, higher education can be portrayed as instrumental in shaping a version of the public good where its qualifications, knowledge production, innovation, development of the professional classes, and expertise are perceived to lead to particular manifestations of public good, delineated as economic, social, political or cultural (McMahon 2009; Stiglitz 1999). The key arguments that underpin this conceptual framing speak to different levels of the public good, whether individual and community levels or the provision of ‘global public goods’ (Marginson 2007; 2013; Menashy 2009). However, a contrasting set of arguments portray the relationship between higher education and the public good as an intrinsic one, where the intellectual, physical and cultural experiences enabled through higher education express and enact the public good e.g. prejudice reduction, democratisation, critical thinking, active citizenship (Singh 2001; Calhoun 2006; Leibowitz, 2013; Marginson, 2011; Locatelli, 2017). Important here are considerations of the historical conjuncture that shapes experiences of higher education at a particular time and what these may mean. In considering the connections and disjunctures between these two formulations and the way writings on higher education in contemporary Africa have engaged with this debate, the paper makes an argument for discussing the importance of processes that link instrumental and intrinsic visions of higher education and the public good. The analysis of these from a rigorous review of literature leads to a delineation of some different views of time, space and evaluation. The paper argues that these contestations need to be read contextually. Higher education in sub-Saharan Africa has moved through phases, from the establishment of flagship national universities in the post-independence period for state bureaucracy formation (Teferra, 2017), to the emergence of developmental universities with a commitment to indigenising knowledge and benefiting marginalised populations, through more recent tendencies towards the marketisation of public institutions and the significant growth of the private sector (Assié-Lumumba & CODESRIA 2006; ADEA & AAU 2004; Coleman 1986; Mamdani, 2007; McCowan 2016). Appreciating these contextual factors in shaping the role and functioning of higher education and thus its relationship to the public good is a central theme in our analysis. We suggest that mainstream conceptualisations of higher education and the public good are underpinned by particular understandings of the nature and form of higher education and how knowledge is acquired, developed and disseminated – orientations that may be very far from the reality of highly unequal, socially stratified, and politically complex societies within which higher education is deeply embedded. Thus a reconceptualisation of the public is required by these contexts and some challenge to conceptualisations of the private, given the strong obligations of individuals to extended families, and the sharing of the benefits of higher education amongst their communities of origin. The paper concludes with a consideration of what may be important in conceptualising higher education and the public good in the African context and the value of such thinking for broader debates on the role of higher education

Flowing Between Fermionic Fixed Points

We study holographic Wilsonian renormalization group flows for bulk spinor fields in AdS. We use this to compute the all-loop beta function for fermionic double trace operators in the dual conformal field theory.Comment: 21 pages. V2: Acknowledgement added; v3: Typo correcte

Holographic Wilsonian flows and emergent fermions in extremal charged black holes

We study holographic Wilsonian RG in a general class of asymptotically AdS backgrounds with a U(1) gauge field. We consider free charged Dirac fermions in such a background, and integrate them up to an intermediate radial distance, yielding an equivalent low energy dual field theory. The new ingredient, compared to scalars, involves a `generalized' basis of coherent states which labels a particular half of the fermion components as coordinates or momenta, depending on the choice of quantization (standard or alternative). We apply this technology to explicitly compute RG flows of charged fermionic operators and their composites (double trace operators) in field theories dual to (a) pure AdS and (b) extremal charged black hole geometries. The flow diagrams and fixed points are determined explicitly. In the case of the extremal black hole, the RG flows connect two fixed points at the UV AdS boundary to two fixed points at the IR AdS_2 region. The double trace flow is shown, both numerically and analytically, to develop a pole singularity in the AdS_2 region at low frequency and near the Fermi momentum, which can be traced to the appearance of massless fermion modes on the low energy cut-off surface. The low energy field theory action we derive exactly agrees with the semi-holographic action proposed by Faulkner and Polchinski in arXiv:1001.5049 [hep-th]. In terms of field theory, the holographic version of Wilsonian RG leads to a quantum theory with random sources. In the extremal black hole background the random sources become `light' in the AdS_2 region near the Fermi surface and emerge as new dynamical degrees of freedom.Comment: 37 pages (including 8 pages of appendix), 10 figures and 2 table

Determinant and Weyl anomaly of Dirac operator: a holographic derivation

We present a holographic formula relating functional determinants: the fermion determinant in the one-loop effective action of bulk spinors in an asymptotically locally AdS background, and the determinant of the two-point function of the dual operator at the conformal boundary. The formula originates from AdS/CFT heuristics that map a quantum contribution in the bulk partition function to a subleading large-N contribution in the boundary partition function. We use this holographic picture to address questions in spectral theory and conformal geometry. As an instance, we compute the type-A Weyl anomaly and the determinant of the iterated Dirac operator on round spheres, express the latter in terms of Barnes' multiple gamma function and gain insight into a conjecture by B\"ar and Schopka.Comment: 11 pages; new comments and references added, typos correcte