Search results for "Actif"
showing 10 items of 212 documents
Aspects of D-brane Dynamics in Supergravity Backgrounds with Fluxes, Kappa-symmetry and Equations of Motion. Part IIB
2006
We derive and carry out a detailed analysis of the equations of motion of the type IIB D branes in generic supergravity backgrounds with fluxes making account of the worldvolume Born-Infeld gauge field and putting a special emphasis on the structure of the Dirac equation for Dp brane fermionic modes. We present an explicit form of the worldvolume field equations for each of the Dp branes (p=1,3,5,7,9) in the cases in which the Neveu-Schwarz flux and the Ramond-Ramond p-form flux along the Dp-brane worldvolume are zero and the supergravity backgrounds do not necessarily induce the worldvolume Born-Infeld flux. We then give several examples of D3, D5 and D7 brane configurations in which the w…
Modular invariant dynamics and fermion mass hierarchies around τ = i
2021
We discuss fermion mass hierarchies within modular invariant flavour models. We analyse the neighbourhood of the self-dual point $\tau=i$, where modular invariant theories possess a residual $Z_4$ invariance. In this region the breaking of $Z_4$ can be fully described by the spurion $\epsilon \approx \tau - i$, that flips its sign under $Z_4$. Degeneracies or vanishing eigenvalues of fermion mass matrices, forced by the $Z_4$ symmetry at $\tau=i$, are removed by slightly deviating from the self-dual point. Relevant mass ratios are controlled by powers of $|\epsilon|$. We present examples where this mechanism is a key ingredient to successfully implement an hierarchical spectrum in the lepto…
The Minkowski and conformal superspaces
2006
We define complex Minkowski superspace in 4 dimensions as the big cell inside a complex flag supermanifold. The complex conformal supergroup acts naturally on this super flag, allowing us to interpret it as the conformal compactification of complex Minkowski superspace. We then consider real Minkowski superspace as a suitable real form of the complex version. Our methods are group theoretic, based on the real conformal supergroup and its Lie superalgebra.
Pseudospectrum and Black Hole Quasinormal Mode Instability
2020
We study the stability of quasinormal modes (QNM) in asymptotically flat black hole spacetimes by means of a pseudospectrum analysis. The construction of the Schwarzschild QNM pseudospectrum reveals the following: (i) the stability of the slowest-decaying QNM under perturbations respecting the asymptotic structure, reassessing the instability of the fundamental QNM discussed by Nollert [H. P. Nollert, About the Significance of Quasinormal Modes of Black Holes, Phys. Rev. D 53, 4397 (1996)] as an "infrared" effect; (ii) the instability of all overtones under small-scale ("ultraviolet") perturbations of sufficiently high frequency, which migrate towards universal QNM branches along pseudospec…
Oh, wait, O8 de Sitter may be unstable!
2021
We analyze the stability of four-dimensional de Sitter vacua constructed by compactifying massive Type IIA supergravity in the presence of two O8 sources [1]. When embedded in String Theory the first source has a clear interpretation as an O8$_-$ plane, but the second one could correspond to either an O8$_+$ plane or to an O8$_-$ plane with 16 D8-branes on top. We find that this latter solution has a tachyonic instability, corresponding to the D8-branes moving away from the O8$_-$ plane. We comment on the possible ways of distinguishing between these sources.
Holomorphic Aspects of String Theory
1989
A string is a piecewise smooth map of the interval to a manifold M. A closed string is a map of the circle S1 into M. In string theory the strings replace the points of the manifold M as fundamental objects. The enormous amount of work done on quantized string models in physics has been motivated by the hope that the quantum string theory would produce a finite quantized theory of gravity, free of the divergences of the ordinary quantized Einstein theory of gravitation. So far the proof is missing but work is continuing. It has been proposed that some kind of string theory would be the unified theory of all fundamental interactions in physics. However, the fundamental principles of string t…
Caution. Liquidation judiciaire clôturée pour insuffisance d'actif, Art. 169 de la loi de 1985, Subsistance du droit de poursuite des créanciers cont…
1993
International audience; (Com. 8 juin 1993, Bonneau c/ Banque Nationale de Paris)
Nullité facultative. Appréciation par les juges du fond de l'opportunité d'annuler le paiement d'une dette échue, eu égard à une condamnation antérie…
2008
International audience; (Versailles, 13e ch., 7 févr. 2008, n° 07/5043, Mandin ès.-qual. c/ James, Juris-Data, n° 2008-356823)
Vers une tridimensionalité du contrôle interactif
2011
We propose in this paper to revisit the concept of interactive control, highlighted by Robert Simons, examining the use of "environmental control systems" in Ten French Companies proactive in ecology. By showing that interactivity of "control systems" is not limited to a vertical dimension as suggested by Simons, but it tends towards three-dimensional (vertical, transversal and external), this study highlights the interest of explore further upstream the concept of interactive control little studied in the literature.
Recherche d'information sur Internet et expérience de consultation
2001
International audience; Le propos de cet article est de caractériser, sur un plan théorique, la nature de l'expérience vécue par le consommateur lors de la consultation d'Internet, de façon à trouver le meilleur design d'un site commercial. Il compare l'expérience de consultation vécue selon que l'objectif initial poursuivi par l'utilisateur est la distraction ou la recherche d'information. Il examine les sources de gratifications et de frustrations contribuant à la valorisation de cette expérience.