X(3872) and its Partners in the Heavy Quark Limit of QCD

In this letter, we propose interpolating currents for the X(3872) resonance, and show that, in the Heavy Quark limit of QCD, the X(3872) state should have degenerate partners, independent of its internal structure. Magnitudes of possible I=0 and I=1 components of the X(3872) are also discussed.Comment: 12 page

Exploiting timescale separation in micro and nano flows

In this paper we describe how timescale separation in micro/nano flows can be exploited for computational acceleration. A modified version of the seamless heterogenous multiscale method (SHMM) is proposed: a multi-step SHMM. This maintains the main advantages of SHMM (e.g., re-initialisation of micro data is not required; temporal gearing (computational speed-up) is easily controlled; and it is applicable to full and intermediate degrees of timescale separation) while improving on accuracy and greatly reducing the number of macroscopic computations and micro/macro coupling instances required. The improved accuracy of the multi-step SHMM is demonstrated for two canonical one-dimensional transient flows (oscillatory Poiseuille and oscillatory Couette flow) and for rarefied-gas oscillatory Poiseuille flow

Time-step coupling for hybrid simulations of multiscale flows

A new method is presented for the exploitation of time-scale separation in hybrid continuum-molecular models of multiscale flows. Our method is a generalisation of existing approaches, and is evaluated in terms of computational efficiency and physical/numerical error. Comparison with existing schemes demonstrates comparable, or much improved, physical accuracy, at comparable, or far greater, efficiency (in terms of the number of time-step operations required to cover the same physical time). A leapfrog coupling is proposed between the ‘macro’ and ‘micro’ components of the hybrid model and demonstrates potential for improved numerical accuracy over a standard simultaneous approach. A general algorithm for a coupled time step is presented. Three test cases are considered where the degree of time-scale separation naturally varies during the course of the simulation. First, the step response of a second-order system composed of two linearly-coupled ODEs. Second, a micro-jet actuator combining a kinetic treatment in a small flow region where rarefaction is important with a simple ODE enforcing mass conservation in a much larger spatial region. Finally, the transient start-up flow of a journal bearing with a cylindrical rarefied gas layer. Our new time-stepping method consistently demonstrates as good as or better performance than existing schemes. This superior overall performance is due to an adaptability inherent in the method, which allows the most-desirable aspects of existing schemes to be applied only in the appropriate conditions

Fermion mass hierarchy and non-hierarchical mass ratios in SU(5) x U(1)_F

We consider a SU(5) x U(1)_F GUT-flavor model in which the number of effects that determine the charged fermions Yukawa matrices is much larger than the number of observables, resulting in a hierarchical fermion spectrum with no particular regularities. The GUT-flavor symmetry is broken by flavons in the adjoint of SU(5), realizing a variant of the Froggatt-Nielsen mechanism that gives rise to a large number of effective operators. By assuming a common mass for the heavy fields and universality of the fundamental Yukawa couplings, we reduce the number of free parameters to one. The observed fermion mass spectrum is reproduced thanks to selection rules that discriminate among various contributions. Bottom-tau Yukawa unification is preserved at leading order, but there is no unification for the first two families. Interestingly, U(1)_F charges alone do not determine the hierarchy, and can only give upper bounds on the parametric suppression of the Yukawa operators.Comment: 14 pages, one figure. Few typos correcte

Long-distance structure of the X(3872)

We investigate heavy quark symmetries for heavy meson hadronic molecules, and explore the consequences of assuming the X(3872) and $Z_b(10610)$ as an isoscalar $D\bar D^*$ and an isovector $B\bar B^*$ hadronic molecules, respectively. The symmetry allows to predict new hadronic molecules, in particular we find an isoscalar $1^{++}$ $B\bar B^*$ bound state with a mass about 10580 MeV and the isovector charmonium partners of the $Z_b(10610)$ and the $Z_b(10650)$ states. Next, we study the $X(3872) \to D^0 \bar D^0\pi^0$ three body decay. This decay mode is more sensitive to the long-distance structure of the X(3872) resonance than its $J/\psi\pi\pi$ and $J/\psi3\pi$ decays, which are mainly controlled by the short distance part of the X(3872) molecular wave function. We discuss the $D^0 \bar D^0$ final state interactions, which in some situations become quite important. Indeed in these cases, a precise measurement of this partial decay width could provide precise information on the interaction strength between the $D^{(*)}\bar D^{(*)}$ charm mesons.Comment: Talk presented at the "XI International Conference on Hyperons, Charm and Beauty Hadrons (BEACH 2014)", Birmingham (U.K.), July 201

Complexity management and multi-scale governance : a case study in an Amazonian indigenous association

Even if Community Operational Research provides methodologies and tools to support community development, there are no published works illustrating how we can support an assessment of self-governance in an indigenous community using COR tools. In this paper we present exploratory research to provide such support to an indigenous association in the Amazon jungle. To address issues of multi-culturalism, we used a creative choice of methods, which included elements of boundary critique, the Viable System Model, rich pictures and social cartography research. We explore the possibilities that this mixed methods approach to COR offers to clarify the core dilemmas and paradoxes of self-governance for sustainability that such communities are facing. The analysis is done through VSM mapping of the community, at different levels and scales of organisation. Our analysis reveals key paradoxes and dilemmas of self-governance, which is helping them to collectively decide on action paths and their needs to (re) develop certain adaptive capabilities. In particular, we show that loss of power from traditional (spiritual) authorities, and loss of rituals and other cooperative practices have negatively affected indigenous ways of implementing life plans and respecting sustainability principles. This research contributes to COR, in presenting an innovative application of the VSM in an indigenous community, supported by expert facilitation, as the basis for reflecting on their self- governance challenges and acting upon them. It takes into account a more critical and ethnographic approach to research, capable of better dealing with the variety of a multi-cultural context

Empirical evidence on volatility estimators

Are historical volatilities better then implied volatilities in estimeting future (also kown as actual or realised) volatilities? Which method of measuring historical or implied volatility is best? In this paper we discuss the methodology for calculating these approaches to volatility, carry out empirical tests on each estimator, as well as on their interrelations. In order to test the "quality" of the estimators, comparisons among historical, implied and future volatilities were used for a full range of estimators. This identifies some of the criticisms for each estimator. The differences found among different estimators are statistically significant and should became fully noted by users of volatilities in the pricing and trading "volatility dependent securities" such as options. Moreover we observed some empirical evidence of the so-called "smile effect" that explains why implied volatility estimators that embody the moneyness effect show lower errors in predicting future volatilities. We also found some empirical evidence for the increase of the smile effect with the approach of the maturity. We also found that the selection of a specific estimator can lead to biased conclusions when studying the forecast ability of implied volatilities. Finally the exercise price effect seems to be asymmetrically dependent on stock price changesinfo:eu-repo/semantics/publishedVersio