Fermion Propagator in Quenched QED3 in the light of the Landau-Khalatnikov-Fradkin transformation

We study the gauge dependence of the fermion propagator in quenched QED3 with and without dynamical symmetry breaking in the light of its Landau-Khalatnikov-Fradkin Transformation (LKFT). In the former case, starting with the massive bare propagator in the Landau gauge, we obtain non perturbative propagator in an arbitrary covariant gauge. At the one-loop level it yields exact wavefunction renormalization and correct $(\alpha \xi)$ terms for the mass fuction. Also, we obtain valuable information for the higher order perturbative expansion of the propagator. As for the case of dynamical chiral symmetry breaking, we start by approximating the numerical solution to the Schwinger-Dyson equation in Landau gauge in the rainbow approximation in terms of analytic functions. We then LKF transform this result to obtain the dynamically generated fermion propagator in an arbitrary covariant gauge. We find that the results obtained have nice qualitative features. We also extend this exercise to the cases involving more reliable ans\"atze for the vertex and encounter similar (and improved) qualitative features.Comment: 6 pages, 6 figures. Contribution to the Proceedings of QCD Downunder 2004 Workshop, held at the Special Centre for the Subatomic Structure of Matter, University of Adelaide, March, 2004. Uses espcrc2.st

Non-perturbative Fermion Propagator for the Massless Quenched QED3

For massless quenched QED in three dimensions, we evaluate a non-perturbative expression for the fermion propagator which agrees with its two loop perturbative expansion in the weak coupling regime. This calculation is carried out by making use of the Landau-Khalatnikov-Fradkin transformations. Any improved construction of the fermion-boson vertex must make sure that the solution of the Schwinger-Dyson equation for the fermion propagator reproduces this result. For two different gauges, we plot the fermion propagator against momentum. We then make a comparison with a similar plot, using the earlier expression for the fermion propagator, which takes into account only the one loop result.Comment: 11 pages, 3 figures, to appear in Phys. Lett.

The Role of Agricultural Growth in South Asian Countries and the Affordability of Food: An Inter-country Analysis

Agriculture is the mainstay of the most developing countries, which supplies food and employment to the majority of the population. Because of the dominance of the agricultural sector, a sufficient supply of domestic food is indispensable to support stable socio-economic and political systems in these countries. To attain a sustained growth of agricultural productivity, sufficient investment in the agricultural sector is crucial, particularly in the initial stages of economic development. This increases agricultural production and as a result, there is a shift in (human) resources from the agricultural sector to the industrial and services sectors. According to Duranton (1998), in order to transform from agricultural sector to industrial sector a significant increase in the agricultural sector productivity is necessary. On the demand-side, the growth in agricultural production increases agricultural income which leads to increase in the demand for industrial products; whereas on the supplyside, the increase in the agricultural productivity shifts human resources from the agricultural to the industrial sector [Jorgenson (1967)]. Economists have further explained these interdependences and linkages between agricultural and industrial sectors. According to Kaldor’s (1978) two-sector model, agricultural and industrial sectors supply inputs to each other and provide market for their outputs but differ in a number of ways. The agricultural sector has disguised unemployment and produces consumer goods for competitive markets, while industrial sector produces investment goods which are sold in imperfectly competitive markets at mark-up prices.

Truncated Schwinger-Dyson Equations and Gauge Covariance in QED3

We study the Landau-Khalatnikov-Fradkin transformations (LKFT) in momentum space for the dynamically generated mass function in QED3. Starting from the Landau gauge results in the rainbow approximation, we construct solutions in other covariant gauges. We confirm that the chiral condensate is gauge invariant as the structure of the LKFT predicts. We also check that the gauge dependence of the constituent fermion mass is considerably reduced as compared to the one obtained directly by solving SDE.Comment: 17 pages, 11 figures. v3. Improved and Expanded. To appear in Few Body System

Non-perturbative Aspects of Schwinger-Dyson Equations

Schwinger-Dyson equations (SDEs) provide a natural staring point to study non-perturbative phenomena such as dynamical chiral symmetry breaking in gauge field theories. We briefly review this research in the context of quenched quantum electrodynamics (QED) and discuss the advances made in the gradual improvement of the assumptions employed to solve these equations. We argue that these attempts render the corresponding studies more and more reliable and suitable for their future use in the more realistic cases of unquenched QED, quantum chromodynamics (QCD) and models alternative to the standard model of particle physics.Comment: 8 pages, 1 figure, Talk given at the X Mexican School of Particles and Fields, Playa del Carmen, Mexico, 2002 (uses AIP style files

The Role of Internet in Marketing Strategies

The use of the Internet has increased in recent years remarkably. Conducting business in the digital economy means using Web- based systems on the Internet and other electronic networks to do some form of electronic commerce. Many research findings confirm and support being of positive effects of Internet on an enterprise's competitive advantage. In this paper, I will illustrate that enterprises can acquire relational and informational competency through Internet technology, and based on these competencies they can succeed in competitive cyber markets. According to the Internet competencies, Internet marketing strategies can be divided into five categories: Transactional, Profile, Customer-oriented, Relationship, and Knowledge strategies. Choosing and implementing any category of strategies depends on the degree of internet competencies (informational and relational) that a firm has. When both are high, proper internet marketing strategy seems to be knowledge strategies; and when both are low, transactional internet marketing strategies would be the suitable category.Internet marketing strategies; Information technologies; Network computing; Digital economy; Information system.