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Search Results: 1 - 10 of 462510 matches for " A Bashir "
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Chiral Symmetry Breaking for Fundamental Fermions
A. Bashir
Physics , 1994,
Abstract: This talk gives an overview of the recent development in the study of non-perturbative fermion-boson vertex in quenched QED towards achieving that the fermion propagator satisfies the Ward-Takahashi identity, is multiplicatively renormalizable, agrees with perturbation theory for weak couplings and has a critical coupling for dynamical mass generation that is strictly gauge independent. The use of such a vertex may lead to a realistic calculation of t(tbar) condensates as the source of electroweak symmetry breaking. (Talk given at The Advanced Study Institute on Frontiers in Particle Physics, Cargese, Ajaccio, France, August 1-13, 1994.)
Non-perturbative Fermion Propagator for the Massless Quenched QED3
A. Bashir
Physics , 2000, DOI: 10.1016/S0370-2693(00)01043-1
Abstract: 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.
Market and Value Chain Analyses of Marketable Natural Products from Agroforestry Systems in Eastern Sudan  [PDF]
Bashir A. El Tahir, Akshay Vishwanath
Journal of Geoscience and Environment Protection (GEP) , 2015, DOI: 10.4236/gep.2015.39006
Abstract: The objectives of the present study were: 1) to identify the prioritized marketable natural products (NPs) from agroforestry systems (AFS), and 2) to conduct market value chain analyses of the most important and prioritized NPs to identify markets and marketing channels; actors, functions and characteristics; constraints and opportunities to entry and growth; opportunities for value addition, and conduct analysis of strengths, weaknesses, opportunities and threats (SWOT analysis). The study was conducted in the Refugees’ camps and their hosting communities in Eastern Sudan. Using the participatory value chain analysis (PVCA) approach, it was found that communities in the project sites obtained a multiplicity of NPs for sustenance and for increasing their incomes. Eight products were identified and ranked as the most important NPs with greatest opportunities for enterprise development at the community level. These are: gum Arabic, honey, fodder, non-timber forest products (NTFPs) and tree seeds. Gum Arabic has been shown to score higher ranks in terms of a) marketability b) ecological suitability (availability), c) social suitability, and d) potential for value addition. The results show that marketing of gum Arabic in the study site is characterized by a large number of producers and relatively few traders and companies work through seven marketing channels. The results demonstrate that in the customary marketing channel there is an upward skewed benefit distribution among the value chain actors. The total relative commercialization margin was 80% indicating that “traders” accrued higher proportion, while “producers”, receive less income (20%) of the end market price. Poor land security, one-sided prices, taxes and levies, lack of finance and appropriate skills are major impediments to gum commodity growth and development. One of the most important opportunities for growth and entry of Gum Arabic are: it is natural organic product and thus well-fit for fair trade, environmentally sustainable and organic market development. Numerous opportunities exist in the site for value addition and distribution synergies and gender-specific development, including that gum Arabic has high synergy with natural resource management and other sectors for enhancing regional and national growth. The study concludes that Gum Arabic production and marketing is financially profitable for producers, traders and
Vault Hematoma after Vaginal Hysterectomy: An Invariable Complication  [PDF]
Laila Yahya A. Alhubaishi, Atif Bashir Fazari
Open Journal of Obstetrics and Gynecology (OJOG) , 2019, DOI: 10.4236/ojog.2019.95056
Abstract: Hysterectomy is common major operation performed in gynecological field practice after Caesarean section. Vaginal hysterectomy is preferred surgery for uterovaginal prolapsed. Vaginal hysterectomy has advantages over abdominal hysterectomy. Post hysterectomy hematomas are responsible for serious morbidity. Ultrasound is an accurate diagnostic tool and so Computed tomography. Conservative management, analgesia and antibiotics will work in small hematoma, but the significant sized hematoma needs surgical drainage and the infected hematoma. Refinement in surgical techniques is recommended to minimize the formation vaginal vault hematomas after vaginal hysterectomy.
Gauge Covariance and the Chiral Condenate in QED3
Bashir, A.;Raya, A.;
Brazilian Journal of Physics , 2007, DOI: 10.1590/S0103-97332007000200024
Abstract: the ambiguities associated with the lack of gauge invariance in the non-perturbative truncations of schwinger-dyson equations (sdes) are a challenging problem which has not yet been resolved in a decisive fashion. pursuing this aim, we study dynamical chiral symmetry breaking in quantum electrodynamics in three space-time dimensions (qed3). we investigate the gauge dependence of the chiral condensate both in the quenched and the unquenched versions of the theory and emphasize the importance of taking into account the gauge covariance properties of the fermion propagator as dictated by its landau-khalatnikov-fradkin transformation (lkft). we present numerical solutions of the sde of the fermion propagator which respect ward-green-takahashi identities (wgti) and lkft simultaneously. as a striking consequence, we obtain a practically gauge independent chiral condensate.
Constructing the fermion-boson vertex in QED3
A. Bashir,A. Raya
Physics , 2001, DOI: 10.1103/PhysRevD.64.105001
Abstract: We derive perturbative constraints on the transverse part of the fermion-boson vertex in massive QED3 through its one loop evaluation in an arbitrary covariant gauge. Written in a particular form, these constraints naturally lead us to the first non-perturbative construction of the vertex, which is in complete agreement with its one loop expansion in all momentum regimes. Without affecting its one-loop perturbative properties, we also construct an effective vertex in such a way that the unknown functions defining it have no dependence on the angle between the incoming and outgoing fermion momenta. Such a vertex should be useful for the numerical study of dynamical chiral symmetry breaking, leading to more reliable results.
Truncated Schwinger-Dyson Equations and Gauge Covariance in QED3
A. Bashir,A. Raya
Physics , 2005, DOI: 10.1007/s00601-007-0177-3
Abstract: 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.
On the three-dimensional CR-submanifolds of the six-dimensional sphere
M. A. Bashir
International Journal of Mathematics and Mathematical Sciences , 1991, DOI: 10.1155/s0161171291000893
Abstract: We show that the six-dimensional sphere does not admit three-dimensionel totally umbilical proper CR-submanifolds.
CR-hypersurfaces of complex projective space
M. A. Bashir
International Journal of Mathematics and Mathematical Sciences , 1994, DOI: 10.1155/s0161171294000876
Abstract: We consider compact n-dimensional minimal foliate CR-real submanifolds of a complex projective space. We show that these submanifolds are great circles on a 2-dimensional sphere provided that the square of the length of the second fundamental form is less than or equal to n ¢ ’1.
On totally umbilical CR-submanifolds of a Kaehler manifold
M. A. Bashir
International Journal of Mathematics and Mathematical Sciences , 1993, DOI: 10.1155/s016117129300050x
Abstract: Let M be a compact 3-dimensional totally umbilical CR-submanifold of a Kaehler manifold of positive holomorphic sectional curvature. We prove that if the length of the mean curvature vector of M does not vanish, then M is either diffeomorphic to S3 or RP3 or a lens space Lp,q3.
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