There is a certain family of conformally invariant first order elliptic systems which include the Dirac operator as its first and simplest member. Their general definition is given and some of their basic properties are described. A special attention is paid to the Rarita-Schwinger operator, the second simplest operator in the row. Its basic properties are described in more details. In the last...

We discuss new results in QCD obtained with string-based methods. These methods were originally derived from superstring theory and are significantly more efficient than conventional Feynman rules. This technology was a key ingredient in the first calculation of the one-loop five-gluon amplitude. We also present a conjecture for a particular one-loop helicity amplitude with an arbitrary number ...

Human settlements experience continual change. In recent years, many rural areas have experienced dispersed grow (rural sprawl) and population declines in traditional village centers (Hollowing). These paradoxical phenomena have occurred in most developing countries, including rural Iran. This study examines this phenomena in three Iranian villages of Kahak area of Qom province, and develops a ...

The helicity amplitudes A 1/2 and S 1/2 for the electromagnetic transition γ∗N → N∗(1535) are calculated in the quark model that is extended to include the lowest lying qqqqq̄ components in addition to the qqq component. It is found that with admixture of 5-quark components with a proportion of 20% in the nucleon and 25-65% in the N∗(1535) resonance the calculated helicity amplitude A 1/2 decrea...

We discuss the implications of charged lepton energy cut to the hadronic invariant mass spectrum in charmless semileptonic B decays. Charged-lepton energy cut is inevitable in order to remove secondary leptonic events such as b → c, τ → l, and to identify the chaged leptons at detectors experimentally. We consider three possible lepton energy cuts, Ecuts l = 0.6, 1.5, 2.3 GeV, and found that wi...

the aim of this study was to evaluate sound and decayed wood of iranianbeech (fagus orientalis) with a nondestructive stress wave method. wood samples,with dimensions of 9 by 19 by 200 mm were decayed in laboratory soil-bed tests,based on european pre-standard env-807. the decay was evaluated by measuringbending dynamic modulus of elasticity (moed) and longitudinal dynamicmodulus of elasticity ...

many constants and coefficient effect on the modeling results. in many cases, it is possible these constants and coefficients differ from their real values in the environment, but the modeling results adapted with real boundary conditions due to other factors adjustment during modeling. uncertainty analysis is a tool for assessing the effect of uncertainty of various factors on the modeling res...

Utilizing boundary integral method (BIM), we investigate molecularspontaneous emission rate enhancement in the vicinity of plasmonic nanoparticles ofelliptical cross section. These types of nanoparticles can considerably enhance themolecule decay rate. The spontaneous emission rate can be modified by altering theaspect ratio of the elliptical nanoparticle, the background refractive index andnan...