Search results for "Processes"
showing 10 items of 3831 documents
Synchronization and fluctuations for interacting stochastic systems with individual and collective reinforcement
2020
The Pólya urn is the paradigmatic example of a reinforced stochastic process. It leads to a random (non degenerated) time-limit. The Friedman urn is a natural generalization whose a.s. time-limit is not random anymore. In this work, in the stream of previous recent works, we introduce a new family of (finite) systems of reinforced stochastic processes, interacting through an additional collective reinforcement of mean field type. The two reinforcement rules strengths (one componentwise, one collective) are tuned through (possibly) different rates n −γ. In the case the reinforcement rates are like n −1 , these reinforcements are of Pólya or Friedman type as in urn contexts and may thus lead …
Exact simulation of diffusion first exit times: algorithm acceleration
2020
In order to describe or estimate different quantities related to a specific random variable, it is of prime interest to numerically generate such a variate. In specific situations, the exact generation of random variables might be either momentarily unavailable or too expensive in terms of computation time. It therefore needs to be replaced by an approximation procedure. As was previously the case, the ambitious exact simulation of exit times for diffusion processes was unreachable though it concerns many applications in different fields like mathematical finance, neuroscience or reliability. The usual way to describe exit times was to use discretization schemes, that are of course approxim…
Persistent random walks, variable length Markov chains and piecewise deterministic Markov processes *
2013
A classical random walk $(S_t, t\in\mathbb{N})$ is defined by $S_t:=\displaystyle\sum_{n=0}^t X_n$, where $(X_n)$ are i.i.d. When the increments $(X_n)_{n\in\mathbb{N}}$ are a one-order Markov chain, a short memory is introduced in the dynamics of $(S_t)$. This so-called "persistent" random walk is nolonger Markovian and, under suitable conditions, the rescaled process converges towards the integrated telegraph noise (ITN) as the time-scale and space-scale parameters tend to zero (see Herrmann and Vallois, 2010; Tapiero-Vallois, Tapiero-Vallois2}). The ITN process is effectively non-Markovian too. The aim is to consider persistent random walks $(S_t)$ whose increments are Markov chains with…
Monopolium production from photon fusion at the Large Hadron Collider
2008
6 pages, 6 figures.-- PACS nrs.: 14.80.Hv; 95.30.Cq; 98.70.-f; 98.80.-k.-- Printed version published Aug 2009.-- ArXiv pre-print available at: http://arxiv.org/abs/0809.0272
Contrôle quantique optimal et robuste dans des systèmes de petite dimension
2020
Optimal control theory (OCT) is the basic and comprehensive method to obtain the optimal solutions of quantum systems controlled by external fields. It provides a powerful set of tools and concepts. One of the goals of the thesis is to design the technique of OCT in two- and three-state quantum systems taking into account losses and robustness, which is of primary importance for the implementation of control techniques in a broad class of platforms.Based on inverse-engineering techniques and the Pontryagin maximum principle (PMP), we establish and test the different optimal strategies showing how to control the transfer in three-level quantum systems considering energy- and time-minimum opt…
Impact of proportion on configural perception of odor mixtures in a newborn mammal
2009
International audience; Configural perception of odor mixtures appears functional early in life. Recent results underline that after the learning of a binary mixture. (AB) that blends in humans, newborn rabbits respond both to the mixture and to its components. However, after the learning of. a single component they do not generalize to the mixture. This suggests that they perceive more in the mixture than the odor of each. constituent (Coureaud et al., Physiol. Behav. 2008). Here, we pursued the assessment of their configural perception of AB, with the. aim to determine whether specific component proportions of A and B elicit the perceptual emergence of an additional odor in AB. Starting. …
DOES FETAL AND NEONATAL EXPOSURE TO ODOUR VARIETY AFFECT LATER RESPONSE TO NOVELTY IN MICE?
2009
Vertebrate embryos and neonates are competent to encode odor information, and to later use it in guiding neonatal, juvenile, and, sometimes, adult behaviour. These data generally derive from experiments in which single odorants were administered. Here, we consider whether the perinatal exposure to multiple odorants administered sequentially will affect later behaviour. Mouse perinates were exposed to contrasted chemosensory regimen through the mother's ingestion of odorized water from days E15 through P21. The effects of 3 treatments were considered: 1/ olfactory monotony (MON; females accessing a benzaldehyde solution 5 days/week; n=46); 2/ olfactory variety (VAR; females accessing each ot…
Spotlight on the Survival Processing Advantage': An FNIRS Study on Adaptive Memory
2015
International audience; In the present study, participants had to rate words for their relevance in an ancestral survival scenario (e.g., is bottle relevant in the fictious scenario of being stranded in the grasslands of a foreign land without basic supplies) and for their pleasantness (e.g., is bottle a pleasant word?). A distractor task lasting a few minutes followed and the participants were then tested on their recall of the words. We used fNIRS to bilaterally monitor the dorsolateral-prefrontal cortex (DLPFC, known to be involved in strategic encoding) during the processing of verbal material in these two deep encoding situations. At the behavioral level, we replicated the survival pro…
Growth response of the saltbush Atriplex nummularia L. to inoculation with the arbuscular mycorrhizal fungus Glomus intraradices
2005
Abstract Plantlets of Atriplex nummularia were inoculated with the arbuscular mycorrhizal fungi Glomus intraradices in a pot experiment. Plants were grown in a low P soil. Highly significant growth response of a Chenopodiaceae was recorded for the first time. Mycorrhizal colonization of roots was well developed, internal hyphae and vesicles were observed, but not arbuscules. These observations suggest that arbuscules are not necessary to obtain significant growth stimulation from mycorrhizal inoculation. Atriplex nummularia is already used as forage crops, its high mycorrhizal dependency offers possibilities to develop this production and revegetation strategies.
Straw mulch as a sustainable solution to decrease runoff and erosion in glyphosate-treated clementine plantations in Eastern Spain. An assessment usi…
2019
[EN] In many Mediterranean areas, citrus orchards exhibit high soil loss rates because of the expansion of drip irrigation that allows cultivation on sloping terrain and the widespread use of glyphosate. To mitigate these non-sustainable soil losses, straw mulch could be applied as an efficient solution but this has been poorly studied. Therefore, the main goal of this paper was to assess the use of straw mulch as a tool to reduce soil losses in clementine plantations, which can be considered representative of a typical Mediterranean citrus orchard. A total of 40 rainfall simulation experiments were carried out on 20 pairs of neighbouring bare and mulched plots. Each experiment involved app…