164 research outputs found

    Brane-Bulk Duality and Non-conformal Gauge Theories

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    We discuss non-conformal gauge theories from type IIB D3-branes embedded in orbifolded space-times. Such theories can be obtained by allowing some non-vanishing logarithmic twisted tadpoles. In certain cases with N=0,1 supersymmetry correlation functions in the planar limit are the same as in the parent N=2 supersymmetric theories. In particular, the effective action in such theories perturbatively is not renormalized beyond one loop in the planar limit. In the N=2 as well as such N=0,1 theories quantum corrections in the D3-brane gauge theories are encoded in the corresponding classical higher dimensional field theories whose actions contain the twisted fields with non-vanishing tadpoles. We argue that this duality can be extended to the non-perturbative level in the N=2 theories. We give some evidence that this might also be the case for N=0,1 theories as well.Comment: 36 pages, revtex; minor misprints corrected, references added (to appear in JHEP

    Matrix Model Description of Baryonic Deformations

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    We investigate supersymmetric QCD with N_c+1 flavors using an extension of the recently proposed relation between gauge theories and matrix models. The impressive agreement between the two sides provides a beautiful confirmation of the extension of the gauge theory-matrix model relation to this case.Comment: 33pages, late

    Dissolving N=4 loop amplitudes into QCD tree amplitudes

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    We use the infrared consistency of one-loop amplitudes in N=4 Yang-Mills theory to derive a compact analytic formula for a tree-level NNMHV gluon scattering amplitude in QCD, the first such formula known. We argue that the IR conditions, coupled with recent advances in calculating one-loop box coefficients, can give a new tool for computing tree-level amplitudes in general. Our calculation suggests that many amplitudes have a structure which is even simpler than that revealed so far by current twistor-space constructions.Comment: 9 pages, revtex4. v2: minor changes, typo in (1) correcte

    Limits on the Non-commutativity Scale

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    A non-vanishing vacuum expectation value for an antisymmetric tensor field leads to the violation of Lorentz invariance, controlled by the dimension (-2) parameter, theta_{mu nu}. We assume that the zeroth order term in theta-expansion represents the Standard Model and study the effects induced by linear terms in theta_{mu nu}. If coupling to theta_{mu nu} is realized in strongly interacting sector of the theory, the clock comparison experiments place the limit on the possible size of this background at the level of 1/\sqrt{theta}>~5X10^{14} GeV. If the interaction with theta_{mu nu} is initially present only in the QED sector, this limit can be relaxed to 10^{11}-10^{12} GeV level. The strength of these limits obviates the inferiority of collider physics with regard to experimental checks of Lorentz invariance. Limits of similar strength are expected to hold in the case of mixed non-commutativity between four-dimensional and extra-dimensional coordinates. We also show that in certain models mixed non-commutativity can be interpreted as 4d CPT-violating background.Comment: 5 pages, Talk presented by Irina Mocioiu at CPT01, Bloomington, Indiana, August 200
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