Search results for "INtRoDuCtIoN"

Dispersal rate and parasitism by Closterocerus chamaeleon (Girault) after its release in Sicily to control Ophelimus maskelli (Ashmead) (Hymenoptera,…

2011

Abstract Spread of the exotic parasitoid Closterocerus chamaeleon (Girault) and its parasitism on the Eucalyptus gall wasp Ophelimus maskelli (Ashmead) (Hymenoptera, Eulophidae) were studied in Sicily after C. chamaeleon introduction in May 2006. Parasitoid spread was evaluated by sampling sites at increasing distances from the five release sites. C. chamaeleon quickly established and spread; within 5 months, it caused 62% parasitism at release sites and 38% parasitism at sites 2 km from release sites. One year after its introduction (spring 2007), C. chamaeleon was detected more than 50 km distant from release sites. By winter 2007–08, the parasitoid was recovered throughout Sicily and in …

Assessing causality in brain dynamics and cardiovascular control

2013

Understanding how different cerebral areas interact to produce an integrated behaviour and disentangling the mechanisms that contribute to cardiovascular control are two of the major challenges of brain and cardiovascular neuroscience. The increasing availability of simultaneous continuous

Using invertebrate remains and pigments in the sediment to infer changes in trophic structure after fish introduction in Lake Fogo: a crater lake in …

2010

Existe-t-il une gestion managériale du flottant et du prix d’offre lors d’une introduction en Bourse sur Euronext Paris?

2015

National audience; L'objectif de cet article est d'étudier dans quelle mesure les motivations à s'introduire en Bourse ainsi que les conséquences ultérieures sur la performance peuvent conditionner le choix du taux de flottant et du prix offert à l'introduction impliquant une décote. Plusieurs motivations sont analysées : la sortie des actionnaires principaux, le financement de la croissance et/ou le rééquilibrage du bilan, l'accroissement de la liquidité du titre. Nous analysons également la relation théorique entre le flottant ou la décote et les performances post-introduction en supposant que les dirigeants anticiperaient les conséquences sur la performance de l'entreprise et ajusteraien…

Generalist invasion in a complex lake food web

2023

Invasive species constitute a threat not only to native populations but also to the structure and functioning of entire food webs. Despite being considered as a global problem, only a small number of studies have quantitatively predicted the food web-level consequences of invasions. Here, we use an allometric trophic network model parameterized using empirical data on species body masses and feeding interactions to predict the effects of a possible invasion of Amur sleeper (Perccottus glenii), on a well-studied lake ecosystem. We show that the modeled establishment of Amur sleeper decreased the biomasses o ftop predator fishes by about 10%–19%. These reductions were largely explained by inc…

Relations for Einstein–Yang–Mills amplitudes from the CHY representation

2017

We show that a recently discovered relation, which expresses tree-level single trace Einstein-Yang-Mills amplitudes with one graviton and $(n-1)$ gauge bosons as a linear combination of pure Yang-Mills tree amplitudes with $n$ gauge bosons, can be derived from the CHY representation. In addition we show that there is a generalisation, which expresses tree-level single trace Einstein-Yang-Mills amplitudes with $r$ gravitons and $(n-r)$ gauge bosons as a linear combination of pure Yang-Mills tree amplitudes with $n$ gauge bosons. We present a general formula for this case.

Gauge-independent off-shell fermion self-energies at two loops: The cases of QED and QCD

2001

We use the pinch technique formalism to construct the gauge-independent off-shell two-loop fermion self-energy, both for Abelian (QED) and non-Abelian (QCD) gauge theories. The new key observation is that all contributions originating from the longitudinal parts of gauge boson propagators, by virtue of the elementary tree-level Ward identities they trigger, give rise to effective vertices, which do not exist in the original Lagrangian; all such vertices cancel diagrammatically inside physical quantities, such as current correlation functions or S-matrix elements. We present two different, but complementary derivations: First, we explicitly track down the aforementioned cancellations inside …

A partial elucidation of the gauge principle

2008

The elucidation of the gauge principle "is the most pressing problem in current philosophy of physics" said Michael Redhead in 2003. This paper argues for two points that contribute to this elucidation in the context of Yang–Mills theories. (1) Yang–Mills theories, including quantum electrodynamics, form a class. They should be interpreted together. To focus on electrodynamics is potentially misleading. (2) The essential role of gauge and BRST symmetries is to provide a local field theory that can be quantized and would be equivalent to the quantization of the non-local reduced theory. If this is correct, the gauge symmetry is significant, not so much because it implies ontological conseque…

Lorentz invariance and gauge equivariance

2014

Trying to place Lorentz and gauge transformations on the same foundation, it turns out that the first one generates invariance, the second one equivariance, at least for the abelian case. This similarity is not a hypothesis but is supported by and a consequence of the path integral formalism in quantum field theory.

INTRODUCTION

2022