Sharif Digital Repository

The effective action for the low energy scattering of two gravitons with a D-brane in the presence of a constant antisymmetric B field in bosonic string theory is calculated and the modification to the standard D-brane action to first order in α′ is obtained  

We obtain an exact analytical expression for magnetoresistance using noncommutative geometry and quantum groups. We then show there is a deep relationship between magnetoresistance and the quantum group suq(2), from which we understand the quantum interpretation of the quantum corrections to the conductivity  

The Konishi anomalies for noncommutative N = 1 supersymmetric U(1) gauge theory arising from planar and nonplanar diagrams are calculated. Whereas planar Konishi anomaly is the expected *-deformation of the commutative anomaly, nonplanar anomaly reflects the important features of nonplanar diagrams of noncommutative gauge theories, such as UV/IR mixing and the appearance of nonlocal open Wilson lines. We use the planar and nonplanar Konishi anomalies to calculate the effective superpotential of the theory. In the limit of vanishing |⊖p, with ⊖ the noncommutativity parameter, the noncommutative effective superpotential depends on a gauge invariant superfield, which includes supersymmetric... 

We obtain an exact analytical expression for magnetoresistance using noncommutative geometry and quantum groups. Then we will show that there is a deep relationship between magnetoresistance and the quantum group su q(2), from which we understand the quantum interpretation of the quantum corrections to the conductivity. © 2003 Elsevier B.V. All rights reserved  

In the first part of this work, a perturbative analysis up to one-loop order is carried out to determine the one-loop β-function of noncommutative U(1) gauge theory with matter fields in the adjoint representation. In the second part, the conformal anomaly of the same theory is calculated using Fujikawa's path integral method. The value of the one-loop β-function calculated in both methods coincides. As it turns out, noncommutative QED with matter fields in the adjoint representation is asymptotically free for the number of flavor degrees of freedom Nf < 3  

The axial anomaly of the noncommutative U(1) gauge theory is calculated by a number of methods and compared with the commutative one. It is found to be given by the corresponding Chern class  

Anomalies arising from nonplanar triangle diagrams of noncommutative gauge theory are studied. Local chiral gauge anomalies for both noncommutative U(1) and U(N) gauge theories with adjoint matter fields are shown to vanish. For noncommutative QED with fundamental matters, due to UV/IR mixing a finite anomaly emerges from the nonplanar contributions. It involves a generalized *-product of gauge fields  

We apply the Dirac bracket quantization to open strings attached to branes in the presence of background antisymmetric field and recover an inherent noncommutativity in the internal coordinates of the brane. © 2000 Elsevier Science B.V. All rights reserved  

The equations of a string inspired noncommutative gravity model on a brane are shown to admit a first integral, generalizing the five dimensional Friedman equation for the FRW Hubble parameter. Copyright © 2007 by World Scientific Publishing Co. Pvt. Ltd  

The noncommutative dipole QED is studied in detail for the matter fields in the adjoint representation. The axial anomaly of this theory is calculated in two and four dimensions using various regularization methods. The Ward-Takahashi identity is proved by making use of a nonperturbative path integral method. The one-loop β-function of the theory is calculated explicitly. It turns out that the value of the β-function depends on the direction of the dipole length L, which defines the noncommutativity. Finally using a semiclassical approximation a nonperturbative definition of the form factors is presented and the anomalous magnetic moment of this theory at one-loop order is computed  

Local noise can produce quantum correlations on an initially classically correlated state, provided that it is not represented by a unital or semiclassical channel. We find the power of any given local channel for producing quantum correlations on an initially classically correlated state. We introduce a computable measure for quantifying the quantum correlations in quantum-classical states, which is based on the noncommutativity of ensemble states in one party of the composite system. Using this measure we show that the amount of quantum correlations produced is proportional to the classical correlations in the initial state. The power of an arbitrary channel for producing quantum...