Renormalization of noncommutative phi 4-theory by multi-scale analysis

In this paper we give a much more efficient proof that the real Euclidean phi 4-model on the four-dimensional Moyal plane is renormalizable to all orders. We prove rigorous bounds on the propagator which complete the previous renormalization proof based on renormalization group equations for non-local matrix models. On the other hand, our bounds permit a powerful multi-scale analysis of the resulting ribbon graphs. Here, the dual graphs play a particular r\^ole because the angular momentum conservation is conveniently represented in the dual picture. Choosing a spanning tree in the dual graph according to the scale attribution, we prove that the summation over the loop angular momenta can be performed at no cost so that the power-counting is reduced to the balance of the number of propagators versus the number of completely inner vertices in subgraphs of the dual graph.Comment: 34 page

On the Effective Action of Noncommutative Yang-Mills Theory

We compute here the Yang-Mills effective action on Moyal space by integrating over the scalar fields in a noncommutative scalar field theory with harmonic term, minimally coupled to an external gauge potential. We also explain the special regularisation scheme chosen here and give some links to the Schwinger parametric representation. Finally, we discuss the results obtained: a noncommutative possibly renormalisable Yang-Mills theory.Comment: 19 pages, 6 figures. At the occasion of the "International Conference on Noncommutative Geometry and Physics", April 2007, Orsay (France). To appear in J. Phys. Conf. Se

One-loop Beta Functions for the Orientable Non-commutative Gross-Neveu Model

We compute at the one-loop order the beta-functions for a renormalisable non-commutative analog of the Gross Neveu model defined on the Moyal plane. The calculation is performed within the so called x-space formalism. We find that this non-commutative field theory exhibits asymptotic freedom for any number of colors. The beta-function for the non-commutative counterpart of the Thirring model is found to be non vanishing.Comment: 16 pages, 9 figure

Exorcizing the Landau Ghost in Non Commutative Quantum Field Theory

We show that the simplest non commutative renormalizable field theory, the $\phi^4$ model on four dimensional Moyal space with harmonic potential is asymptotically safe to all orders in perturbation theor

Innovative Approaches to Analysing Carbon Sequestration as a Mitigation Strategy in Tropical Pasture Landscapes in Two Emblematic Contexts, the Amazon and the West African Sahel

The relationship between ruminant production systems and climate change is complex. As a major contributor to greenhouse gas (GHG) emissions, the sector has been the subject of considerable controversy, with particularly severe criticism in the 2000s. However, ten years ago, the attitude towards grazing lands began to change. Their efficient use of non-renewable energy and their contribution to carbon (C) sequestration were considered as key factors in the new environmental challenge. The reality of this mitigation potential was recently called into question once again in the global agriculture and climate change debate, including that of sequestration in the soil where grazing lands occupy a major position (30-40% of the land surface representing 30% of the soil organic C of the world). Few scientific references are available on these questions in tropical regions, and the standard metrics and methods used may turn out to be unsuitable for the correct evaluation of grazed ecosystems in these regions. Significant work is therefore required to establish baselines and design strategies to ensure sustainable grazing in these regions where the global sequestration potential is high relative to the surface areas concerned. To contribute to this debate, we focus on mitigation options offered by rangelands and grasslands and their management in two emblematic tropical contexts, humid and dry tropics, where field studies have been based on original and holistic approaches at different levels. In Amazonia, if curbing deforestation remains a priority, it needs to be accompanied by sustainable management of deforested areas. In the French Amazon (French Guiana), monitoring fields using chronosequences and flux towers has produced scientific knowledge on the significant mitigation capacities of grassland ecosystems. In the Brazilian Amazon, the spatial logic of the agro-ecological intensification of forage production has enabled a transition from individual extractive systems to farm management at communal levels. In the West African Sahelian region (Northern Senegal), an integrative study at landscape scale revealed the unexpected capacity of soil and shrubs for C sequestration that can offset the GHG emissions for which pastoralism in dry tropical zones is usually blamed

Renormalization of the commutative scalar theory with harmonic term to all orders

The noncommutative scalar theory with harmonic term (on the Moyal space) has a vanishing beta function. In this paper, we prove the renormalizability of the commutative scalar field theory with harmonic term to all orders by using multiscale analysis in the momentum space. Then, we consider and compute its one-loop beta function, as well as the one on the degenerate Moyal space. We can finally compare both to the vanishing beta function of the theory with harmonic term on the Moyal space.Comment: 16 page

Vacuum configurations for renormalizable non-commutative scalar models

In this paper we find non-trivial vacuum states for the renormalizable non-commutative $\phi^4$ model. An associated linear sigma model is then considered. We further investigate the corresponding spontaneous symmetry breaking.Comment: 17 page

Overview of the parametric representation of renormalizable non-commutative field theory

We review here the parametric representation of Feynman amplitudes of renormalizable non-commutative quantum field models.Comment: 10 pages, 3 figures, to be published in "Journal of Physics: Conference Series

Degenerate noncommutativity

We study a renormalizable four dimensional model with two deformed quantized space directions. A one-loop renormalization is performed explicitly. The Euclidean model is connected to the Minkowski version via an analytic continuation. At a special value of the parameters a nontrivial fixed point of the renormalization group occurs.Comment: 16 page

Relapsing macrophage activating syndrome in a 15-year-old girl with Still's disease: a case report

<p>Abstract</p> <p>Introduction</p> <p>Macrophage activating syndrome is a severe, potentially life-threatening condition that may accompany Still's disease. It is characterized by fever, hepatosplenomegaly, lymphadenopathy, severe cytopenia, serious liver dysfunction, coagulopathy and neurologic involvement. The principal treatment for patients with this syndrome includes etoposide 150 mg/2 M twice a week for two weeks, dexamethasone 10 mg/2 M for two weeks and cyclosporine 3 mg/kg to 5 mg/kg for a longer period. Cases of relapse of macrophage activating syndrome are relatively rare.</p> <p>Case presentation</p> <p>We describe the case of a 15-year-old Iraqi girl with Still's disease who developed macrophage activating syndrome with acute respiratory distress syndrome that required resuscitation and mechanical ventilation. Following intensive treatment, including high dose steroids and cyclosporine, the patient improved significantly. Two weeks after cyclosporine was discontinued, however, she was readmitted with an acute relapse of macrophage activating syndrome manifested by spiking fever, arthralgias, maculopapular rash and leukocytosis. This time the patient recovered following the reintroduction of treatment with cyclosporine and the addition of mycophenolate mofetil (Cellcept).</p> <p>Conclusion</p> <p>We believe that cyclosporine is a cornerstone for the treatment of Still's disease. We recommend continuing this medication for several weeks following the patient's clinical recovery in order to prevent macrophage activating syndrome relapses.</p