On the Anomalies and Schwinger Terms in Noncommutative Gauge Theories

Invariant (nonplanar) anomaly of noncommutative QED is reexamined. It is found that just as in ordinary gauge theory UV regularization is needed to discover anomalies, in noncommutative case, in addition, an IR regularization is also required to exhibit existence of invariant anomaly. Thus resolving the controversy in the value of invariant anomaly, an expression for the unintergrated anomaly is found. Schwinger terms of the current algebra of the theory are derived.Comment: LaTeX, axodraw.sty, 1 figure; v2: Typos corrected, References added, Version to appear in Int. J. Mod. Phys. A (2006

On R**2 Corrections for 5D Black Holes

We study higher order corrections to extremal black holes/black string in five dimensions. These higher order corrections are due to supersymmetric completion of R**2 term in five dimensions. By making use of the results we extend the notion of very special geometry when higher derivative terms are also taken into account. This can be used to make a connection between total bundle space of near horizon wrapped M2's and wrapped M5's in the presence of higher order corrections. We also show how the corrected geometry removes the singularity of a small black hole.Comment: 16 pages, latex file, V3: typos corrected, refs added, V4; minor corrections, few comments added, refs adde

p-p' System with B-field, Branes at Angles and Noncommutative Geometry

We study the generic $p-p^\prime$ system in the presence of constant NS 2-form $B_{ij}$ field. We derive properties concerning with the noncommutativity of D-brane worldvolume, the Green functions and the spectrum of this system. In the zero slope limit, a large number of light states appear as the lowest excitations in appropriate cases. We are able to relate the energies of the lowest states after the GSO projection with the configurations of branes at angles. Through analytic continuation, the system is compared with the branes with relative motion.Comment: 21 pages, Latex. References regarding to section 3 and 4 added. Typos correcte

A Note on Exact Solutions and Attractor Mechanism for Non-BPS Black Holes

We obtain two extremal, spherically symmetric, non-BPS black hole solutions to 4D supergravity, one of which carries D2-D6 charges and the other carries D0-D2-D4 charges. For the D2-D6 case, rather than solving the equations of motion directly, we assume the form of the solution and then find that the assumption satisfies the equations of motion and the constraint. Our D2-D6 solution is manifestly dual to the solution presented in 0710.4967. The D0-D2-D4 solution is obtained by performing certain $[SL(2,{\bf Z})]^{3}$ duality transformations on the D0-D4 solution in 0710.4967.Comment: 20 pages, LaTe

Non-Commutative GUTs, Standard Model and C,P,T

Noncommutative Yang-Mills theories are sensitive to the choice of the representation that enters in the gauge kinetic term. We constrain this ambiguity by considering grand unified theories. We find that at first order in the noncommutativity parameter \theta, SU(5) is not truly a unified theory, while SO(10) has a unique noncommutative generalization. In view of these results we discuss the noncommutative SM theory that is compatible with SO(10) GUT and find that there are no modifications to the SM gauge kinetic term at lowest order in \theta. We study in detail the reality, hermiticity and C,P,T properties of the Seiberg-Witten map and of the resulting effective actions expanded in ordinary fields. We find that in models of GUTs (or compatible with GUTs) right-handed fermions and left-handed ones appear with opposite Seiberg-Witten map.Comment: 28 pages. Added references and comments in the introductio

Towards Noncommutative Fuzzy QED

We study in one-loop perturbation theory noncommutative fuzzy quenched QED_4. We write down the effective action on fuzzy S**2 x S**2 and show the existence of a gauge-invariant UV-IR mixing in the model in the large N planar limit. We also give a derivation of the beta function and comment on the limit of large mass of the normal scalar fields. We also discuss topology change in this 4 fuzzy dimensions arising from the interaction of fields (matrices) with spacetime through its noncommutativity.Comment: 33 page

On The Interaction Of D0-Brane Bound States And RR Photons

We consider the problem of the interaction between D0-brane bound state and 1-form RR photons by the world-line theory. Based on the fact that in the world-line theory the RR gauge fields depend on the matrix coordinates of D0-branes, the gauge fields also appear as matrices in the formulation. At the classical level, we derive the Lorentz-like equations of motion for D0-branes, and it is observed that the center-of-mass is colourless with respect to the SU(N) sector of the background. Using the path integral method, the perturbation theory for the interaction between the bound state and the RR background is developed. We discuss what kind of field theory may be corresponded to the amplitudes which are calculated by the perturbation expansion in world-line theory. Qualitative considerations show that the possibility of existence of a map between the world-line theory and the non-Abelian gauge theory is very considerable.Comment: LaTeX, 28 pages, 4 eps figures. v2 and v3: eqs. (3.18) and (B.2) are corrected, very small change

Amplitudes With Different Helicity Configurations Of Noncommutative QED

The amplitudes of purely photonic and photon{2-fermion processes of non- commutative QED (NCQED) are derived for different helicity configurations of photons. The basic ingredient is the NCQED counterpart of Yang-Mills recursion relations by means of Berends and Giele. The explicit solutions of recursion relations for NCQED photonic processes with special helicity configurations are presented.Comment: 23 pages, 2 figure

Entropy Function for Non-extremal D1D5 and D2D6NS5-branes

We apply the entropy function formalism to non-extremal D1D5 and D2D6NS5-branes whose throat approximation is given by the Schwarzschild black hole in AdS_3\times S^3\times T^4 and AdS_3\times S^2\times S^1\times T^4, respectively. We find the Bekenstein-Hawking entropy and the (alpha')^3R^4 corrections from the value of the entropy function at its saddle point. While the higher derivative terms have no effect on the temperature, they decrease the value of the entropy.Comment: 17 Pages, Latex file; Minor additions, version published in JHE

Corrections to D-brane Action and Generalized Boundary State

In this paper, we generalize a boundary state to the one incorporating non-constant gauge field strength as an external background coupled to the boundary of a string worldsheet in bosonic string theory. This newly defined boundary state satisfies generalized nonlinear boundary conditions with non-constant gauge field strength, and is BRST invariant. The divergence immanent in this boundary state coincide with the one calculated in a string sigma model. We extract the relevant massless part of this generalized boundary state, and give a part of the D-brane action with the non-constant gauge field strength, that is, derivative corrections to the D-brane action.Comment: 21 pages, LaTeX, 2 eps figures, a reference added, typos correcte