408 research outputs found

    Towards a quantum field theory of primitive string fields

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    We denote generating functions of massless even higher spin fields "primitive string fields" (PSF's). In an introduction we present the necessary definitions and derive propagators and currents of these PDF's on flat space. Their off-shell cubic interaction can be derived after all off-shell cubic interactions of triplets of higher spin fields have become known [2],[3]. Then we discuss four-point functions of any quartet of PSF's. In subsequent sections we exploit the fact that higher spin field theories in AdSd+1AdS_{d+1} are determined by AdS/CFT correspondence from universality classes of critical systems in dd dimensional flat spaces. The O(N) invariant sectors of the O(N) vector models for 1≀N≀∞1\leq N \leq \infty play for us the role of "standard models", for varying NN, they contain e.g. the Ising model for N=1 and the spherical model for N=∞N=\infty. A formula for the masses squared that break gauge symmetry for these O(N) classes is presented for d = 3. For the PSF on AdSAdS space it is shown that it can be derived by lifting the PSF on flat space by a simple kernel which contains the sum over all spins. Finally we use an algorithm to derive all symmetric tensor higher spin fields. They arise from monomials of scalar fields by derivation and selection of conformal (quasiprimary) fields. Typically one monomial produces a multiplet of spin ss conformal higher spin fields for all s≄4s \geq 4, they are distinguished by their anomalous dimensions (in CFT3CFT_3) or by their mass (in AdS4AdS_4). We sum over these multiplets and the spins to obtain "string type fields", one for each such monomial.Comment: 16 pages,Late

    Coulombic Energy Transfer and Triple Ionization in Clusters

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    Using neon and its dimer as a specific example, it is shown that excited Auger decay channels that are electronically stable in the isolated monomer can relax in a cluster by electron emission. The decay mechanism, leading to the formation of a tricationic cluster, is based on an efficient energy-transfer process from the excited, dicationic monomer to a neighbor. The decay is ultrafast and expected to be relevant to numerous physical phenomena involving core holes in clusters and other forms of spatially extended atomic and molecular matter.Comment: 5 pages, 1 figure, to be published in PR

    Hommes et femmes dans les tournois du Moyen Ăąge

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    Au cours des diverses pĂ©riodes allant de 1062 au dĂ©but du xviie siĂšcle, hommes et femmes se spĂ©cialisent dans des rĂŽles diffĂ©rents dans les tournois, en fonction des types d’épreuves et du pays oĂč elles se dĂ©roulent. En commençant par le haut, une reine comme Catherine d’Aragon pouvait ĂȘtre la promotrice dĂ©signĂ©e d’un tournoi royal et, sur le continent, Ă  l’occasion de mariages de cour, les Ă©pouses et leurs filles d’honneur constituaient le groupe central des personnages regardant les actions depuis leurs balcons. En Allemagne, seules les jeunes femmes vertueuses Ă©taient admises Ă  la finale de la danse de la bougie. À la Cour anglaise, les femmes ne dĂ©terminaient pas les vainqueurs des tournois ; cela Ă©tait une prĂ©rogative rĂ©servĂ©e aux hĂ©rauts et juges du tournoi. Lors de la cĂ©rĂ©monie pour les vainqueurs, seules les dames des plus hauts Ă©chelons de la sociĂ©tĂ© distribuaient les prix Ă  partir des dĂ©cisions des hĂ©rauts. MĂȘme si, lors des cĂ©rĂ©monies d’ouverture, les adversaires et/ou rĂ©pondants paradaient occasionnellement avec leurs « inĂ©vitables jeunes demoiselles » dans un char, les jeunes femmes n’appartenaient pas Ă  la liste des prix, mais Ă  l’imagination des chevaliers. Les faits et la fiction Ă©taient des mondes sĂ©parĂ©s qui, cependant, s’influençaient mutuellement fortement. MalgrĂ© les tentations, les amours courtisanes et les tournois ne se sont jamais vraiment rencontrĂ©s sur les terrains de joutes. Les hommes restaient entre eux et les reprĂ©sentantes du beau sexe de toutes les strates sociales infĂ©rieures n’étaient autorisĂ©es qu’en tant que spectatrices.In the tournament and its various periods and phases from about 1062 to the early beginnings of the 17th century men and women featured in different roles depending on the forms played and on the countries in which they were staged. Starting from the top a queen, such as Catherine of Aragon could function as the nominal promoter of a royal tournament, and on the continent – on the occasion of courtly weddings – the bride with her maids of honour formed the pivot at the lists watching the actions from their balconies. In Germany only virtuous maidens were admitted to the final candle-dance. At the English court women did not determine the winners of tournaments; this was the sole prerogative of the heralds and tournament judges. At the victory ceremony ladies of the highest echelons only distributed the prizes on the bases of the heralds’ decisions. Even if – in opening ceremonies – challengers and/or answerers occasionally paraded round with their “inevitable young damsel” in a chariot, maidens did not belong to one of the prizes, but to chivalric fiction. Fact and fiction were separate worlds, which greatly influenced one another. Despite tempting aspirations courtly love and tournaments never found together in the tiltyard. In the lists men stayed among themselves, and the fair sex of any lower social stratum was only allowed to attend as spectators

    Supersymmetric Distributions, Hilbert Spaces of Supersymmetric Functions and Quantum Fields

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    The recently investigated Hilbert-Krein and other positivity structures of the superspace are considered in the framework of superdistributions. These tools are applied to problems raised by the rigorous supersymmetric quantum field theory.Comment: 24 page

    The critical O(NN) σ\sigma-model at dimension 2<d<42<d<4: Hardy-Ramanujan distribution of quasi-primary fields and a collective fusion approach

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    The distribution of quasiprimary fields of fixed classes characterized by their O(N)(N) representations YY and the number pp of vector fields from which they are composed at N=∞N=\infty in dependence on their normal dimension [ή][\delta] is shown to obey a Hardy-Ramanujan law at leading order in a 1N\frac{1}{N}-expansion. We develop a method of collective fusion of the fundamental fields which yields arbitrary \qps and resolves any degeneracy.Comment: KL-TH-94/2, 21 pages (uuencoded Postscript file

    Arabidopsis DOF Transcription Factors Act Redundantly to Reduce CONSTANS Expression and Are Essential for a Photoperiodic Flowering Response

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    SummaryFlowering of Arabidopsis is induced by long summer days (LDs). The transcriptional regulator CONSTANS (CO) promotes flowering, and its transcription is increased under LDs. We systematically misexpressed transcription factors in companion cells and identified several DOF proteins that delay flowering by repressing CO transcription. Combining mutations in four of these, including CYCLING DOF FACTOR 2 (CDF2), caused photoperiod-insensitive early flowering by increasing CO mRNA levels. CO transcription is promoted to differing extents by GIGANTEA (GI) and the F-box protein FKF1. We show that GI stabilizes FKF1, thereby reducing CDF2 abundance and allowing transcription of CO. Despite the crucial function of GI in wild-type plants, introducing mutations in the four DOF-encoding genes into gi mutants restored the diurnal rhythm and light inducibility of CO. Thus, antagonism between GI and DOF transcription factors contributes to photoperiodic flowering by modulating an underlying diurnal rhythm in CO transcript levels

    The minimal conformal O(N) vector sigma model at d=3

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    For the minimal O(N) sigma model, which is defined to be generated by the O(N) scalar auxiliary field alone, all n-point functions, till order 1/N included, can be expressed by elementary functions without logarithms. Consequently, the conformal composite fields of m auxiliary fields possess at the same order such dimensions, which are m times the dimension of the auxiliary field plus the order of differentiation.Comment: 15 page

    Design of a robotic hand with a biologically-inspired parallel actuation system for prosthetic applications

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    Trabajo presentado al 34th Annual Mechanisms and Robotics Conference celebrado en Quebec del 15 al 18 de agosto de 2010.This paper presents the design of a robotic hand for prosthetic applications. The main characteristic of this robotic hand is its biologically-inspired parallel actuation system, which is based on the behavior/strength space of the Flexor Digitorum Profundus (FDP) and the Flexor Digitorum Superficialis (FDS) muscles. The design separates the strength space of the FDS and FDP muscles into a lighter strength region where finer manipulation and general approach tasks are executed, and a higher strength region where the more robust grasps are achieved. Two parallel actuator types and kinematic structures are designed to complement the requirements of both strength space regions.This research was performed under an award/contract from Telemedicine Advanced Technology Research Center (TATRC), of the U.S. Army Medical Research and Materiel Command (USAMRMC) of the U.S. Department of Defense.Peer Reviewe

    On Conformal Infinity and Compactifications of the Minkowski Space

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    Using the standard Cayley transform and elementary tools it is reiterated that the conformal compactification of the Minkowski space involves not only the "cone at infinity" but also the 2-sphere that is at the base of this cone. We represent this 2-sphere by two additionally marked points on the Penrose diagram for the compactified Minkowski space. Lacks and omissions in the existing literature are described, Penrose diagrams are derived for both, simple compactification and its double covering space, which is discussed in some detail using both the U(2) approach and the exterior and Clifford algebra methods. Using the Hodge * operator twistors (i.e. vectors of the pseudo-Hermitian space H_{2,2}) are realized as spinors (i.e., vectors of a faithful irreducible representation of the even Clifford algebra) for the conformal group SO(4,2)/Z_2. Killing vector fields corresponding to the left action of U(2) on itself are explicitly calculated. Isotropic cones and corresponding projective quadrics in H_{p,q} are also discussed. Applications to flat conformal structures, including the normal Cartan connection and conformal development has been discussed in some detail.Comment: 38 pages, 8 figures, late
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