Linking pain and the body: neural correlates of visually induced analgesia

The visual context of seeing the body can reduce the experience of acute pain, producing a multisensory analgesia. Here we investigated the neural correlates of this “visually induced analgesia” using fMRI. We induced acute pain with an infrared laser while human participants looked either at their stimulated right hand or at another object. Behavioral results confirmed the expected analgesic effect of seeing the body, while fMRI results revealed an associated reduction of laser-induced activity in ipsilateral primary somatosensory cortex (SI) and contralateral operculoinsular cortex during the visual context of seeing the body. We further identified two known cortical networks activated by sensory stimulation: (1) a set of brain areas consistently activated by painful stimuli (the so-called “pain matrix”), and (2) an extensive set of posterior brain areas activated by the visual perception of the body (“visual body network”). Connectivity analyses via psychophysiological interactions revealed that the visual context of seeing the body increased effective connectivity (i.e., functional coupling) between posterior parietal nodes of the visual body network and the purported pain matrix. Increased connectivity with these posterior parietal nodes was seen for several pain-related regions, including somatosensory area SII, anterior and posterior insula, and anterior cingulate cortex. These findings suggest that visually induced analgesia does not involve an overall reduction of the cortical response elicited by laser stimulation, but is consequent to the interplay between the brain's pain network and a posterior network for body perception, resulting in modulation of the experience of pain

Constraints on Lorentz Invariance Violation from Fermi-Large Area Telescope Observations of Gamma-Ray Bursts

We analyze the MeV/GeV emission from four bright Gamma-Ray Bursts (GRBs) observed by the Fermi-Large Area Telescope to produce robust, stringent constraints on a dependence of the speed of light in vacuo on the photon energy (vacuum dispersion), a form of Lorentz invariance violation (LIV) allowed by some Quantum Gravity (QG) theories. First, we use three different and complementary techniques to constrain the total degree of dispersion observed in the data. Additionally, using a maximally conservative set of assumptions on possible source-intrinsic spectral-evolution effects, we constrain any vacuum dispersion solely attributed to LIV. We then derive limits on the "QG energy scale" (the energy scale that LIV-inducing QG effects become important, E_QG) and the coefficients of the Standard Model Extension. For the subluminal case (where high energy photons propagate more slowly than lower energy photons) and without taking into account any source-intrinsic dispersion, our most stringent limits (at 95% CL) are obtained from GRB090510 and are E_{QG,1}>7.6 times the Planck energy (E_Pl) and E_{QG,2}>1.3 x 10^11 GeV for linear and quadratic leading order LIV-induced vacuum dispersion, respectively. These limits improve the latest constraints by Fermi and H.E.S.S. by a factor of ~2. Our results disfavor any class of models requiring E_{QG,1} \lesssim E_Pl.Comment: Accepted for publication by Physical Review

Some computations in the cyclic permutations of completely rational nets

In this paper we calculate certain chiral quantities from the cyclic permutation orbifold of a general completely rational net. We determine the fusion of a fundamental soliton, and by suitably modified arguments of A. Coste , T. Gannon and especially P. Bantay to our setting we are able to prove a number of arithmetic properties including congruence subgroup properties for $S, T$ matrices of a completely rational net defined by K.-H. Rehren .Comment: 30 Pages Late

Qualité bioécologique d’un milieu lacustre hyper-eutrophisé en zone équatoriale (Afrique Centrale) : peuplement de protozoaires ciliés et macro invertébrés bentho-aquatiques

Le lac d’Obili est un écosystème aquatique situé en plein cœur de Yaoundé en Afrique centrale. Les études physique, chimique, et biologique ont été effectuées dans ce milieu aquatique. Des prélèvements ont été effectués durant six mois sur le site en surface et en profondeur, grâce aux méthodes telles que la spectrophotométrie, la respirométrie et la volumétrie. Des échantillons de boues, d’eau et de vase ont été analysés. Les observations à la loupe et l’identification des espèces grâce aux clés d’identifications ont permis d’avoir une idée claire sur l’état trophique du milieu. A partir des résultats découlant de ces analyses, nous avons pu bâtir une matrice de résultat. Sur celle-ci, des analyses statistiques descriptives ont été appliquées avec le logiciel d’analyse SPSS. De ces résultats, nous observons une légère acidité des eaux en profondeur par rapport à celles de la surface qui sont pratiquement neutre. L’oxygène est croissant sur les deux plans d’eaux sur toute la période d’étude. Le Dioxyde de Carbone (CO2) quant à lui présente une courbe en U. La température est globalement élevée en surface par rapport à la profondeur. La concentration en nitrate est plus élevée en profondeur qu’en surface. La DBO5 évolue en dents de scie et présente des courbes qui se croisent pendant le mois de mars. Des bio-indicateurs de polysaprobité telles que Metopus ovatus Caenomorpha medusa, Paramecium africanum révèlent une dystrophie avancée du milieu. Les dysfonctionnement de ce milieu lentique et la surcharge en ortho phosphate et nitrates sont confirmée par l’identification d’une forte peuplent des macrophytes a l’instar de Nymhea lotus, Pistia stratiotes et d’ Eichhornia crassipes. Les fortes corrélations sont observées entre les paramètres physicochimique et biologique et le test de Mann Whitney montre un unique écosystème avec peu de variation spatio-temporelle.Mots-clés : ciliés, macro invertébrés, bio indicateur, hyper eutrophisation.Bio-ecological assessment of a hyper-eutrophic lake in an equatorial region (Central Africa) : population dynamics of ciliated protozoa and bentho-aquatic macro invertebratesThe Obili Lake is an aquatique ecosystem that is positioned in Yaoundé, Cameroon Physico-chemical and biological assessment were carried out in this lake during a six month duration at the surface and the depth level by spectrophotometry, respirometry and volumetry. Analytical statistical studies reveal a slight acidity from surface to base, while Oxygene concentrations were present in the medium. Carbon dioxide showed a U profile, while temperature is higher at the surface due to the direct incidence of solar radiation. BOD values were variable in the medium. Bio-indicators of polysaprobity such as Metopus ovatus Caenomorpha medusa, Paramecium africanum reveal an advance dystrophication of the milieu. The dysfunctioning of this lentic medium and the high load of orthophosphate and nitrates are confirmed by the identification of a high density of macrophytes such as Nymhea lotus, Pistia stratiotes et d’Eichhornia crassipes. The high correlation that is observed between the physico-chimical and biological parameters and the Mann Whitney test proof a unique ecosystem with low spatial dispersionKeywords : ciliated protozoa, benthic macro-invertebrates, bio-indicator, hyper-eutrophication

Modular localization and Wigner particles

We propose a framework for the free field construction of algebras of local observables which uses as an input the Bisognano-Wichmann relations and a representation of the Poincare' group on the one-particle Hilbert space. The abstract real Hilbert subspace version of the Tomita-Takesaki theory enables us to bypass some limitations of the Wigner formalism by introducing an intrinsic spacetime localization. Our approach works also for continuous spin representations to which we associate a net of von Neumann algebras on spacelike cones with the Reeh-Schlieder property. The positivity of the energy in the representation turns out to be equivalent to the isotony of the net, in the spirit of Borchers theorem. Our procedure extends to other spacetimes homogeneous under a group of geometric transformations as in the case of conformal symmetries and de Sitter spacetime.Comment: 22 pages, LaTeX. Some errors have been corrected. To appear on Rev. Math. Phy

On intermediate subfactors of Goodman-de la Harpe-Jones subfactors

In this paper we present a conjecture on intermediate subfactors which is a generalization of Wall's conjecture from the theory of finite groups. Motivated by this conjecture, we determine all intermediate subfactors of Goodman-Harpe-Jones subfactors, and as a result we verify that Goodman-Harpe-Jones subfactors verify our conjecture. Our result also gives a negative answer to a question motivated by a conjecture of Aschbacher-Guralnick.Comment: To appear in Comm. Math. Phy

Charged sectors, spin and statistics in quantum field theory on curved spacetimes

The first part of this paper extends the Doplicher-Haag-Roberts theory of superselection sectors to quantum field theory on arbitrary globally hyperbolic spacetimes. The statistics of a superselection sector may be defined as in flat spacetime and each charge has a conjugate charge when the spacetime possesses non-compact Cauchy surfaces. In this case, the field net and the gauge group can be constructed as in Minkowski spacetime. The second part of this paper derives spin-statistics theorems on spacetimes with appropriate symmetries. Two situations are considered: First, if the spacetime has a bifurcate Killing horizon, as is the case in the presence of black holes, then restricting the observables to the Killing horizon together with "modular covariance" for the Killing flow yields a conformally covariant quantum field theory on the circle and a conformal spin-statistics theorem for charged sectors localizable on the Killing horizon. Secondly, if the spacetime has a rotation and PT symmetry like the Schwarzschild-Kruskal black holes, "geometric modular action" of the rotational symmetry leads to a spin-statistics theorem for charged covariant sectors where the spin is defined via the SU(2)-covering of the spatial rotation group SO(3).Comment: latex2e, 73 page

Topological Quantum Field Theories and Operator Algebras

We review "quantum" invariants of closed oriented 3-dimensional manifolds arising from operator algebras.Comment: For proceedings of "International Workshop on Quantum Field Theory and Noncommutative Geometry", Sendai, November 200

Very high energy gamma-ray follow-up observations of novae and dwarf novae with the MAGIC telescopes

In the last few years the Fermi-LAT instrument has detected GeV gamma-ray emission from several novae. Such GeV emission can be interpreted in terms of inverse Compton emission from electrons accelerated in the shock or in terms of emission from hadrons accelerated in the same conditions. The latter might reach much higher energies and could produce a second component in the gamma-ray spectrum at TeV energies. We perform follow-up observations of selected novae and dwarf novae in search of the second component in TeV energy gamma rays. This can shed light on the acceleration process of leptons and hadrons in nova explosions. We have performed observations with the MAGIC telescopes of 3 sources, a symbiotic nova YY Her, a dwarf nova ASASSN-13ax and a classical nova V339 Del, shortly after their outbursts. We did not detect TeV gamma-ray emission from any of the objects observed. The TeV upper limits from MAGIC observations and the GeV detection by Fermi constrain the acceleration parameters for electrons and hadrons.Comment: Proceedings of the 34th International Cosmic Ray Conference, 30 July- 6 August, 2015, The Hague, The Netherlands. The content of this submission is similar to our paper in the Fermi Symposium of novae observations with MAGIC, which appeared as arXiv:1502.05853. arXiv admin note: substantial text overlap with arXiv:1502.0585