The two D6R4 type invariants and their higher order generalisation

We show that there are two distinct classes of D6R4 type supersymmetry invariants in maximal supergravity. The second class includes a coupling in F2D4R4 that generalises to 1/8 BPS protected F2kD4R4 couplings. We work out the supersymmetry constraints on the corresponding threshold functions, and argue that the functions in the second class satisfy to homogeneous differential equations for arbitrary k>0, such that the corresponding exact threshold functions in type II string theory should be proportional to Eisenstein series, which we identify. This analysis explains in particular that the exact D6R4 threshold function is the sum of an Eisenstein function and a solution to an inhomogeneous Poisson equation in string theory.Comment: 53 page

Minimal unitary representations from supersymmetry

We compute the supersymmetry constraints on the R^4 type corrections in maximal supergravity in dimension 8, 6, 4 and 3, and determine the tensorial differential equations satisfied by the function of the scalar fields multiplying the R^4 term in the corresponding invariants. The second order derivative of this function restricted to the Joseph ideal vanishes in dimension lower than six. These results are extended to the d^4 R^4 and the d^6 R^4 corrections, based on the harmonic superspace construction of these invariants in the linearised approximation. We discuss the solutions of these differential equations and analysis the consequences on the non-perturbative type II low energy string theory effective action.Comment: 84 pages, Corrected version for publication in JHEP, additional comment on d^6 R^4 in four dimension

Les sources historiques du quotidien en exil

Le 29 novembre 1830, de jeunes officiers polonais portés par le vent révolutionnaire qui soufflait sur l’Europe prirent les armes dans les rues de Varsovie. Ce fut l’étincelle qui déclencha l’une des plus importantes luttes de la Pologne pour son indépendance face à l’Empire russe. Après dix mois de conflit et une défaite, ce sont près de 6 000 Polonais qui prirent la route de l’exil, majoritairement vers la France (Bielecki, 1986, p. 21). À partir de 1831, s’initie un vaste mouvement migrato..

Mesoscopic modeling of hidden spiking neurons

Can we use spiking neural networks (SNN) as generative models of multi-neuronal recordings, while taking into account that most neurons are unobserved? Modeling the unobserved neurons with large pools of hidden spiking neurons leads to severely underconstrained problems that are hard to tackle with maximum likelihood estimation. In this work, we use coarse-graining and mean-field approximations to derive a bottom-up, neuronally-grounded latent variable model (neuLVM), where the activity of the unobserved neurons is reduced to a low-dimensional mesoscopic description. In contrast to previous latent variable models, neuLVM can be explicitly mapped to a recurrent, multi-population SNN, giving it a transparent biological interpretation. We show, on synthetic spike trains, that a few observed neurons are sufficient for neuLVM to perform efficient model inversion of large SNNs, in the sense that it can recover connectivity parameters, infer single-trial latent population activity, reproduce ongoing metastable dynamics, and generalize when subjected to perturbations mimicking optogenetic stimulation

Topological recursion for Orlov-Scherbin tau functions, and constellations with internal faces

We study the correlators $W_{g,n}$ arising from Orlov-Scherbin 2-Toda tau functions with rational content-weight $G(z)$, at arbitrary values of the two sets of time parameters. Combinatorially, they correspond to generating functions of weighted Hurwitz numbers and $(m,r)$-factorisations of permutations. When the weight function is polynomial, they are generating functions of constellations on surfaces in which two full sets of degrees (black/white) are entirely controlled, and in which internal faces are allowed in addition to boundaries. We give the spectral curve (the "disk" function $W_{0,1}$, and the "cylinder" function $W_{0,2}$) for this model, generalising Eynard's solution of the 2-matrix model which corresponds to $G(z)=1+z$, by the addition of arbitrarily many free parameters. Our method relies both on the Albenque-Bouttier combinatorial proof of Eynard's result by slice decompositions, which is strong enough to handle the polynomial case, and on algebraic arguments. Building on this, we establish the topological recursion (TR) for the model. Our proof relies on the fact that TR is already known at time zero (or, combinatorially, when the underlying graphs have only boundaries, and no internal faces) by work of Bychkov-Dunin-Barkowski-Kazarian-Shadrin (or Alexandrov-Chapuy-Eynard-Harnad for the polynomial case), and on the general idea of deformation of spectral curves due to Eynard and Orantin, which we make explicit in this case. As a result of TR, we obtain strong structure results for all fixed-genus generating functions.Comment: 43 pages. v2: added Section 7 covering the case of a rational-exponential weight function. The rest of the paper is unchange

High-Resolution Ultrasound Imaging System for the Evaluation of the Vascular Response to Stent or Balloon Injuries in the Rabbit Iliac Arteries

For novel therapeutic approaches of cardiovascular diseases, the preclinical investigation is of paramount and required appropriate technologies. We investigated the use of high-resolution ultrasound imaging system to evaluate the progression of vascular lesions in a rabbit model. Animals underwent vascular injury using two standard procedures. A bare-metal stent was placed within the left iliac artery, and a balloon injury was induced in the contralateral artery. The animals were kept on a regular diet for 8 weeks. A Vevo3100© VisualSonic high-resolution ultrasound imaging system and the associated software VevoVasc were used for the longitudinal evaluation of the injured arteries and the distal abdominal aorta. The lumen size increased rapidly after the intervention in both iliac arteries. In the balloon-injured artery, the augmentation was transient and significantly reversed, inducing an alteration of the blow flow. In contrast, in the stented segment, the lumen size was maintained enlarged overtime. We demonstrated a significant correlation for the wall thickness and the lumen size between ultrasonic and histological quantification. High-resolution ultrasound imaging in rabbit iliac arteries and the distal abdominal aorta is feasible, reliable and of relevance to investigate novel strategies for the inhibition of hyperplasia induced with standard injury models

The Quality-Diversity Transformer: Generating Behavior-Conditioned Trajectories with Decision Transformers

In the context of neuroevolution, Quality-Diversity algorithms have proven effective in generating repertoires of diverse and efficient policies by relying on the definition of a behavior space. A natural goal induced by the creation of such a repertoire is trying to achieve behaviors on demand, which can be done by running the corresponding policy from the repertoire. However, in uncertain environments, two problems arise. First, policies can lack robustness and repeatability, meaning that multiple episodes under slightly different conditions often result in very different behaviors. Second, due to the discrete nature of the repertoire, solutions vary discontinuously. Here we present a new approach to achieve behavior-conditioned trajectory generation based on two mechanisms: First, MAP-Elites Low-Spread (ME-LS), which constrains the selection of solutions to those that are the most consistent in the behavior space. Second, the Quality-Diversity Transformer (QDT), a Transformer-based model conditioned on continuous behavior descriptors, which trains on a dataset generated by policies from a ME-LS repertoire and learns to autoregressively generate sequences of actions that achieve target behaviors. Results show that ME-LS produces consistent and robust policies, and that its combination with the QDT yields a single policy capable of achieving diverse behaviors on demand with high accuracy.Comment: 10+7 page