586 research outputs found

    Discrete Symmetries (C,P,T) in Noncommutative Field Theories

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    In this paper we study the invariance of the noncmmutative gauge theories under C, P and T transformations. For the noncommutative space (when only the spatial part of θ\theta is non-zero) we show that NCQED is Parity invariant. In addition, we show that under charge conjugation the theory on noncommutative Rθ4R^4_{\theta} is transformed to the theory on R−θ4R^4_{-\theta}, so NCQED is a CP violating theory. The theory remains invariant under time reversal if, together with proper changes in fields, we also change θ\theta by −θ-\theta. Hence altogether NCQED is CPT invariant. Moreover we show that the CPT invariance holds for general noncommutative space-time.Comment: Revtex File, 4 pages, no figures, minor changes from previous verion. To appear in Phys. Rev. Let

    One Loop Renormalizability of Supersymmetric Yang-Mills Theories on Noncommutative Two-Torus

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    We argue that Yang-Mills theory on noncommutative torus, expressed in the Fourrier modes, is described by a gauge theory in a usual commutative space, the gauge group being a generalization of the area-preserving diffeomorphisms to the noncommutative case. In this way, performing the loop calculation in this gauge theory in the continuum limit we show that this theory is {\it one loop renormalizable}, and discuss the UV and IR limits. The moduli space of the vacua of the noncommutative super Yang-Mills theories in (2+1) dimensions is discussed.Comment: 16 pp, one figure, v2: One reference added, typos corrected. v3: minor exchange

    Classification of Different Branes at Angles

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    In this paper, we consider two D-branes rotated with respect to each other, and argue that in this way one can find brane configurations preserving {1 \f 16} of SUSY. Also we classify different brane configurations preserving {1 \f 2}, {1 \f 4}, {3 \f 16},{1 \f 8}, {1 \f 16} of SUSY.Comment: Tex, 11 page, no figure

    More on Mixed Boundary Conditions and D-branes Bound States

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    In this article, applying different types of boundary conditions; Dirichlet, Neumann, or Mixed, on open strings we realize various new brane bound states in string theory. Calculating their interactions with other D-branes, we find their charge densities and their tension. A novel feature of (p−2,p)(p-2,p) brane bound state is its "non-commutative" nature which is manifestly seen both in the open strings mode expansions and in their scattering off a DpD_p-brane. Moreover we study three or more object bound states in string theory language. Finally we give a M-theoretic picture of these bound states.Comment: Latex file, pages, No Figure

    Noncommutative Open String Theories and Their Dualities

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    The recently found non-critical open string theories is reviewed. These open strings, noncommutative open string theories (NCOS), arise as consistent quantum theories describing the low energy theory of D-branes in a background electric B-field in the critical limit. Focusing on the D3-brane case, we construct the most general (3+1) NCOS, which is described by four parameters. We study S and T -dualities of these theories and argue the existence of a U-duality group.Comment: 10 pages, no figures, The invited talk, presented in the conference "Brane New World and Noncommutative Geometry", Torino, Villa Gualino,(Italy) October, 200

    Solution Phase Space and Conserved Charges: A General Formulation for Charges Associated with Exact Symmetries

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    We provide a general formulation for calculating conserved charges for solutions to generally covariant gravitational theories with possibly other internal gauge symmetries, in any dimensions and with generic asymptotic behaviors. These solutions are generically specified by a number of exact (continuous, global) symmetries and some parameters. We define "parametric variations" as field perturbations generated by variations of the solution parameters. Employing the covariant phase space method, we establish that the set of these solutions (up to pure gauge transformations) form a phase space, the \emph{solution phase space}, and that the tangent space of this phase space includes the parametric variations. We then compute conserved charge variations associated with the exact symmetries of the family of solutions, caused by parametric variations. Integrating the charge variations over a path in the solution phase space, we define the conserved charges. In particular, we revisit "black hole entropy as a conserved charge" and the derivation of the first law of black hole thermodynamics. We show that the solution phase space setting enables us to define black hole entropy by an integration over any compact, codminesion-2, smooth spacelike surface encircling the hole, as well as to a natural generalization of Wald and Iyer-Wald analysis to cases involving gauge fields.Comment: 35 pp, no figure
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