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Cotonou, Benin

Samary D.O.,University Abomey Calavi
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

This manuscript reports the first order β-functions of recently proved just renormalizable random tensor models endowed with a U(1)d gauge invariance. The models that we consider are polynomial Abelian φ64 and φ56 models. We show in this work that both models are asymptotically free in the UV. © 2013 American Physical Society.

Ousmane Samary D.,Perimeter Institute for Theoretical Physics | Ousmane Samary D.,University Abomey Calavi
Classical and Quantum Gravity | Year: 2014

In this paper, we provide the closed equations that satisfy two-point correlation functions of rank 3 and 4 tensorial group field theory. The formulation of the current problem extends the method used by Grosse and Wulkenhaar (2009 arXiv:0909.1389) to the tensor case. Ward - Takahashi identities and Schwinger - Dyson equations are combined to establish a nonlinear integral equation for the two-point functions. In the three-dimensional case, the solution of this equation is given perturbatively at the second order of the coupling constant. © 2014 IOP Publishing Ltd.

Geloun J.B.,Perimeter Institute for Theoretical Physics | Geloun J.B.,University Abomey Calavi | Rivasseau V.,University Paris - Sud
Communications in Mathematical Physics | Year: 2013

We prove that an integrated version of the Gurau colored tensor model supplemented with the usual Bosonic propagator on U(1)4 is renormalizable to all orders in perturbation theory. The model is of the type expected for quantization of space-time in 4D Euclidean gravity and is the first example of a renormalizable model of this kind. Its vertex and propagator are four-stranded like in 4D group field theories, but without gauge averaging on the strands. Surprisingly perhaps, the model is of the φ{symbol}6 rather than of the φ{symbol}4 type, since two different φ{symbol}6-type interactions are log-divergent, i. e. marginal in the renormalization group sense. The renormalization proof relies on a multiscale analysis. It identifies all divergent graphs through a power counting theorem. These divergent graphs have internal and external structure of a particular kind called melonic. Melonic graphs dominate the 1/N expansion of colored tensor models and generalize the planar ribbon graphs of matrix models. A new locality principle is established for this category of graphs which allows to renormalize their divergences through counterterms of the form of the bare Lagrangian interactions. The model also has an unexpected anomalous log-divergent (∫ φ{symbol}2)2 term, which can be interpreted as the generation of a scalar matter field out of pure gravity. © 2012 Springer-Verlag.

Agency: Cordis | Branch: FP7 | Program: CP | Phase: ENV.2013.6.1-1 | Award Amount: 12.17M | Year: 2013

Tropical Atlantic climate recently experienced pronounced shifts of great socio-economic importance. The oceanic changes were largest in the eastern boundary upwelling systems. African countries bordering the Atlantic strongly depend upon their ocean - societal development, fisheries, and tourism. They were strongly affected by these climatic changes and will face important adaptation challenges associated with global warming. Furthermore, these upwelling regions are also of great climatic importance, playing a key role in regulating global climate. Paradoxically, the Tropical Atlantic is a region of key uncertainty in earth-climate system: state-of-the-art climate models exhibit large systematic error, climate change projections are highly uncertain, and it is largely unknown how climate change will impact marine ecosystems. PREFACE aims to address these interconnected issues, and has the following goals: To reduce uncertainties in our knowledge of the functioning of Tropical Atlantic climate. To improve climate prediction and the quantification of climate change impacts in the region. To improve understanding of the cumulative effects of the multiple stressors of climate variability, greenhouse induced climate change, and fisheries on marine ecosystems, and ecosystem services (e.g., fisheries, coastal vulnerability). To assess the socio-economic vulnerabilities and evaluate the resilience of Atlantic African fishing communities to climate-driven ecosystem shifts and global markets. To meet these goals we bring together European and African expertise to combine regional and global scale modelling capabilities, field experiments and observation systems. Our target region includes areas more affected by climate change and by its consequences, European outermost regions, and African countries bordering the Atlantic.

Agency: Cordis | Branch: FP7 | Program: ERC-SG | Phase: ERC-SG-SH6 | Award Amount: 893.16K | Year: 2011

Knowledge of the last 1000 years in the West African Sahel comes largely from historical sources, which say that many regions were ruled by vast polities. The aim of my archaeological project is to seize how, in fact, lhe empires of this region structured the landscape, and the movemenl of peoples, ideas, and things, with a focus on the period AD 1200-1850. Is empire really a useful term? I will confront historical evidence with archaeological data from one area at the intersection of several polities: the dallols in Niger. This area is rich in remains, said to result from population movements and processes of religious and political change, but these remains have been only briefly described so far. As this region is a key area of migrations and cross-influences, it is the ideal laboratory for exploring the materialisation of contacts and boundaries, through a mapping of material culture distributions. My project will approach these sites holistically, carrying out archaeological regional survey and prospection. Excavation will indicate chronology and cultural affiliation. At lhe same time, I will take an interdisciplinary approach, using anthropological and oral-historical enquiries to obtain background information to test hypotheses generated by the archaeological data. Enquiries will assess how material culture can show group belonging and population shifts, and examine the role of individuals called technical specialists. This will help solve the current impasse in our understanding of vast empires which, though they are historically known, remain poorly understood. My project will not just improve our knowledge of an almost-unknown part of the world, but thanks to its geographical location, interdisciplinary nature and strong thematic framework, open up avenues of thinking about the relalion between archaeological and historical data, the mediation of relations through artefacts, and the archaeology of empires, all widely-relevant research issues

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