Chiral expansion of the nucleon mass to order q^6

We present the results of a complete two-loop calculation at order q^6 of the nucleon mass in manifestly Lorentz-invariant chiral perturbation theory. The renormalization is performed using the reformulated infrared renormalization, which allows for the treatment of two-loop integrals while preserving all relevant symmetries, in particular chiral symmetry.Comment: 6 pages, 2 figures, REVTeX

Improving the ultraviolet behavior in baryon chiral perturbation theory

We introduce a new formulation of baryon chiral perturbation theory which improves the ultraviolet behavior of propagators and can be interpreted as a smooth cutoff regularization scheme. It is equivalent to the standard approach, preserves all symmetries and therefore satisfies the Ward identities. Our formulation is equally well defined in the vacuum, one- and few-nucleon sectors of the theory. The equations (Bethe-Salpeter, Lippmann-Schwinger, etc.) for the scattering amplitudes of the few-nucleon sector are free of divergences in the new approach. Unlike the usual cutoff regularization, our 'cutoffs' are parameters of the Lagrangian and do not have to be removed.Comment: 19 pages, 3 figures, REVTeX 4; version to be published in Phys. Rev. D, additional section on issues of renormalization in few-body sector include

Quantum electrodynamics for vector mesons

Quantum electrodynamics for $\rho$ mesons is considered. It is shown that, at tree level, the value of the gyromagnetic ratio of the $\rho^+$ is fixed to 2 in a self-consistent effective quantum field theory. Further, the mixing parameter of the photon and the neutral vector meson is equal to the ratio of electromagnetic and strong couplings, leading to the mass difference $M_{\rho^0}-M_{\rho^\pm}\sim 1 {\rm MeV}$ at tree order.Comment: 4 pages, 2 figures, REVTeX 4, accepted for publication in PR

Two-nucleon problem in semi-relativistic baryon chiral perturbation theory

We consider a symmetry-preserving approach to the nucleon-nucleon scattering problem in the framework of the higher-derivative formulation of baryon chiral perturbation theory. Within this framework the leading-order amplitude is calculated by solving renormalizable equations and corrections are taken into account perturbatively.Comment: 3 pages, talk given at 20th European Conference on Few-Body Problems in Physics (EFB 20), Pisa, Italy, 10-14 Sep 200

Signed double Roman domination on cubic graphs

The signed double Roman domination problem is a combinatorial optimization problem on a graph asking to assign a label from $\{\pm{}1,2,3\}$ to each vertex feasibly, such that the total sum of assigned labels is minimized. Here feasibility is given whenever (i) vertices labeled $\pm{}1$ have at least one neighbor with label in $\{2,3\}$; (ii) each vertex labeled $-1$ has one $3$-labeled neighbor or at least two $2$-labeled neighbors; and (iii) the sum of labels over the closed neighborhood of any vertex is positive. The cumulative weight of an optimal labeling is called signed double Roman domination number (SDRDN). In this work, we first consider the problem on general cubic graphs of order $n$ for which we present a sharp $n/2+\Theta(1)$ lower bound for the SDRDN by means of the discharging method. Moreover, we derive a new best upper bound. Observing that we are often able to minimize the SDRDN over the class of cubic graphs of a fixed order, we then study in this context generalized Petersen graphs for independent interest, for which we propose a constraint programming guided proof. We then use these insights to determine the SDRDNs of subcubic $2\times m$ grid graphs, among other results

Universality of the rho-meson coupling in effective field theory

It is shown that both the universal coupling of the rho-meson and the Kawarabayashi-Suzuki-Riadzuddin-Fayyazuddin expression for the magnitude of its coupling constant follow from the requirement that chiral perturbation theory of pions, nucleons, and rho-mesons is a consistent effective field theory. The prerequisite of the derivation is that all ultraviolet divergences can be absorbed in the redefinition of fields and the available parameters of the most general effective Lagrangian.Comment: 4 pages, 2 figures, REVTeX 4, accepted for publication in PR

Infrared renormalization of two-loop integrals and the chiral expansion of the nucleon mass

We describe details of the renormalization of two-loop integrals relevant to the calculation of the nucleon mass in the framework of manifestly Lorentz-invariant chiral perturbation theory using infrared renormalization. It is shown that the renormalization can be performed while preserving all relevant symmetries, in particular chiral symmetry, and that renormalized diagrams respect the standard power counting rules. As an application we calculate the chiral expansion of the nucleon mass to order O(q^6).Comment: Version accepted for publication in Nucl. Phys. A, missing one-loop diagram added, minor changes in notation, discussion of results improve

Methods of sputum processing for cell counts, immunocytochemistry and in situ hybridisation.

Since the first attempts to use standardised methods for sampling induced airways sputum, two methods for processing the expectorate have evolved. The first involves selecting all viscid or denser portions from the expectorated sample with the aid of an inverted microscope. This method has been extensively evaluated and reported in detail. The second approach involves processing the entire expectorate, comprising sputum plus variable amounts of saliva. Recent modifications to this method include collecting saliva and sputum separately in order to reduce salivary contamination. Both methods have advantages and disadvantages. The advantages of using selected sputum are: squamous cell contamination is v5%, making cell counting easier and quicker to perform, the total cell count (TCC) can be expressed per gram of lower airway secretions, and concentrations of chemicals in the fluid phase are unaffected by the confounding influence of saliva, and can be accurately corrected for dilution. The disadvantage is that selection takes a few minutes longer to perform and requires an inverted microscope. The advantage of using the entire expectorate is that the technique is quicker to perform, but there are some disadvantages that require consideration. The expectorate contains a variable mixture of sputum plus saliva which maydilute the sputum and confound its analysis. The reproducibility of cell counts has been reported to be lower if squamous cell contamination represents w20% of all recovered cells. There is conflicting data as to whether or not differential cell counts (DCCs) differ between the two methods. One study reported a higher percentage of eosinophils in sputum processed by the selection method compared to the entire expectorate but this has not been confirmed in other studies. Although, both the selected sputum and the entire expectorate methods have the same ability to distinguish asthmatics or bronchitics from healthy subjects, they are not interchangeable, and, once a technique has been adopted for a given study, it should always be applied