Determination of the strange quark mass from Cabibbo-suppressed tau decays with resummed perturbation theory in an effective scheme

We present an analysis of the m_s^2-corrections to Cabibbo-suppressed tau lepton decays employing contour improved resummation within an effective scheme which is an essential new feature as compared to previous analyses. The whole perturbative QCD dynamics of the tau-system is described by the beta-function of the effective coupling constant and by two gamma-functions for the effective mass parameters of the strange quark in different spin channels. We analyze the stability of our results with regard to high-order terms in the perturbative expansion of the renormalization group functions. A numerical value for the strange quark mass in the MS scheme is extracted m_s(M_\tau)=130\pm 27_{exp}\pm 9_{th} MeV. After running to the scale 1 GeV this translates into m_s(1 GeV)=176 \pm 37_{exp}\pm 13_{th} MeV.Comment: 32 pages, latex, 4 postscript figures, revised version to appear in European Physical Journal C, discussion of the choice of the moments added, some errors correcte

Asymptotic structure of perturbative series for τ\tau lepton decay observables: ms2m_s^2 corrections

In a previous paper we performed an analysis of asymptotic structure of perturbation theory series for semileptonic $\tau$-lepton decays in massless limit. We extend our analysis to the Cabibbo suppressed $\Delta S=1$ decay modes of the $\tau$ lepton. In particular we address the problem of $m_s^2$ corrections to theoretical formulas. The properties of the asymptotic behavior of the finite order perturbation theory series for the coefficient functions of the $m_s^2$ corrections are studied.Comment: 25 page

Asymptotic structure of perturbative series for tau lepton observables

We analyze tau lepton decay observables, namely moments of the hadronic spectral density in the finite energy interval (0,M_\tau), within finite order perturbation theory including \alpha_s^4 corrections. The start of asymptotic growth of perturbation theory series is found at this order in a scheme invariant manner. We establish the ultimate accuracy of finite order perturbation theory predictions and discuss the construction of optimal observables.Comment: 21 page

Renormalization group-like proof of the universality of the Tutte polynomial for matroids

In this paper we give a new proof of the universality of the Tutte polynomial for matroids. This proof uses appropriate characters of Hopf algebra of matroids, algebra introduced by Schmitt (1994). We show that these Hopf algebra characters are solutions of some differential equations which are of the same type as the differential equations used to describe the renormalization group flow in quantum field theory. This approach allows us to also prove, in a different way, a matroid Tutte polynomial convolution formula published by Kook, Reiner and Stanton (1999). This FPSAC contribution is an extended abstract.Comment: 12 pages, 3 figures, conference proceedings, 25th International Conference on Formal Power Series and Algebraic Combinatorics, Paris, France, June 201

Experimental investigation on the bending behaviour of hybrid and steel thin walled box beams—The role of adhesive joints

In the automotive design, nowadays there are two fundamental drivers. On one hand there are the environmental problems, on the other hand there are the safety matters. Within this contest, the weight reduction has become a key driver in the design of vehicles and it is necessary to consider and to study the use of nonconventional materials taking advantage from their high potential of weight reduction and energy absorption capability. In this perspective, the aim of this work is the study of the structural behaviour of box beams by means of a series of three points bending tests. The examined cross sections are those typically used in automotive construction. Different type of materials (steel, composite) and joining technologies (adhesive, spot weld) have been examined, considering different configurations. The work put in evidence the advantages coming from the use of adhesive, which allows structures with important weight reduction and better mechanical properties than traditional joining solution

Archetypal narratives : toward a theological appreciation of early Celtic hagiography.

This study aims to interpret Lives of Christian saints as examples of religious literature. Hagiography is commonly studied as an historical artefact indicative of the politics or linguistics of the time in which a text was composed, but few theorists have attempted to interpret its religious content. As these texts were composed within monastic environments I argue that the religious content may be illumined by a methodology which identifies an implicit theology of sanctity within the narrative. The biblical hermeneutic method proposed by Paul Ricoeur in the mid-twentieth century is applied to the earliest Lives of Samson, Cuthbert, and Brigit. These three date from the mid- to late-seventh century, a time of secular and ecclesiastical change, in some cases profound turmoil. Historical context for the composition of each text is presented; texts are analysed for biblical allusions and literary sources, and submitted to structural analysis. Motifs of religious and archetypal significance are derived from the work of theorists in folklore, anthropology, Bible, and the History of Religions. Each text is examined for motifs and patterns that disclose the structural framework used to organize the work. The structural analysis is then used to highlight central themes in the text. This interpretive process imagines a dynamic encounter between text and reader which combines historical inquiry with biblical hermeneutic, fulfilling Ricoeur’s expectation that the encounter would expand the reader’s horizon of meaning. Samson’s encounters with serpents and sorceress function as an initiatory pattern drawing monastics into a dynamic of spiritual growth. Cuthbert’s time on Farne Island includes echoes of the Desert Saints as well as the crucifixion of Christ and results in a brief but powerfully kenotic episcopal ministry. Brigit’s Kildare becomes the locus of the New Jerusalem, City of Refuge and Peaceable Kingdo

An algebraic Birkhoff decomposition for the continuous renormalization group

This paper aims at presenting the first steps towards a formulation of the Exact Renormalization Group Equation in the Hopf algebra setting of Connes and Kreimer. It mostly deals with some algebraic preliminaries allowing to formulate perturbative renormalization within the theory of differential equations. The relation between renormalization, formulated as a change of boundary condition for a differential equation, and an algebraic Birkhoff decomposition for rooted trees is explicited

Why Matrix theory works for oddly shaped membranes

We give a simple proof of why there is a Matrix theory approximation for a membrane shaped like an arbitrary Riemann surface. As corollaries, we show that noncompact membranes cannot be approximated by matrices and that the Poisson algebra on any compact phase space is U(infinity). The matrix approximation does not appear to work properly in theories such as IIB string theory or bosonic membrane theory where there is no conserved 3-form charge to which the membranes couple.Comment: 8 pages, 4 figures, revtex; references adde

Phylogeny of ‘core Gruiformes’ (Aves: Grues) and resolution of the Limpkin–Sungrebe problem

Abstract Opinions on the systematic relationships of birds in the avian order Gruiformes have been as diverse as the families included within it. Despite ongoing debate over monophyly of the order and relationships among its various members, recent opinion has converged on the monophyly of a ''core'' group of five families classified as the suborder Grues: the rails (Rallidae), the cranes (Gruidae), the Limpkin (Aramidae), the trumpeters (Psophiidae), and the finfoots (Heliornithidae). We present DNA sequence data from four mitochondrial (cytochrome b, 12S rRNA, Valine tRNA, and 16S rRNA) and three nuclear loci (intron 7 of b-fibrinogen, intron 5 of alcohol dehydrogenase-I, and introns 3 through 5 of glyceraldehyde-3-phosphate dehydrogenase) to test previous hypotheses of interfamilial relationships within Grues, with particular attention to the enigmatic family Heliornithidae. Separate and combined analyses of these gene sequences confirm the monophyly of Grues as a whole, and of the five families individually, including all three species of Heliornithidae. The preferred topology unambiguously supports relationships among four of the five families, with only the position of Psophiidae remaining equivocal. Bayesian ''relaxed-clock'' dating methods suggest that the divergences of the three heliornithid species occurred in the mid-Tertiary, suggesting that their present disjunct pantropical distribution is a result of early-to mid-Tertiary dispersal