33,555 research outputs found

    Time and Tachyon

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    Recent analysis suggests that the classical dynamics of a tachyon on an unstable D-brane is described by a scalar Born-Infeld type action with a runaway potential. The classical configurations in this theory at late time are in one to one correspondence with the configuration of a system of non-interacting (incoherent), non-rotating dust. We discuss some aspects of canonical quantization of this field theory coupled to gravity, and explore, following earlier work on this subject, the possibility of using the scalar field (tachyon) as the definition of time in quantum cosmology. At late `time' we can identify a subsector in which the scalar field decouples from gravity and we recover the usual Wheeler - de Witt equation of quantum gravity.Comment: LaTeX file, 24 page

    D-Brane Probe and Closed String Tachyons

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    We consider a D-brane probe in unstable string background associated with flux branes. The twist in spacetime metric reponsible for the supersymmetry breaking is shown to manifest itself in mixing of open Wilson lines with the phases of some adjoint matter fields, resulting in a nonlocal and nonsupersymmetric form of Yang-Mills theory as the probe dynamics. This provides a setup where one can study fate of a large class of unstable closed string theories that include as a limit type 0 theories and various orbifolds of type II and type 0 theories. We discuss the limit of C/Zn{\bf C}/Z_n orbifold in some detail and speculate on couplings with closed string tachyons.Comment: LaTeX, 17 pages, typos fixed, references update

    Energy Momentum Tensor and Marginal Deformations in Open String Field Theory

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    Marginal boundary deformations in a two dimensional conformal field theory correspond to a family of classical solutions of the equations of motion of open string field theory. In this paper we develop a systematic method for relating the parameter labelling the marginal boundary deformation in the conformal field theory to the parameter labelling the classical solution in open string field theory. This is done by first constructing the energy-momentum tensor associated with the classical solution in open string field theory using Noether method, and then comparing this to the answer obtained in the conformal field theory by analysing the boundary state. We also use this method to demonstrate that in open string field theory the tachyon lump solution on a circle of radius larger than one has vanishing pressure along the circle direction, as is expected for a codimension one D-brane.Comment: LaTeX file, 25 pages; v2: minor addition

    D0-brane tension in string field theory

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    We compute the D0-brane tension in string field theory by representing it as a tachyon lump of the D1-brane compactified on a circle of radius RR. To this aim, we calculate the lump solution in level truncation up to level L=8. The normalized D0-brane tension is independent on RR. The compactification radius is therefore chosen in order to cancel the subleading correction 1/L21/L^2. We show that an optimal radius R∗R^* indeed exists and that at R∗R^* the theoretical prediction for the tension is reproduced at the level of 10−510^{-5}. As a byproduct of our calculation we also discuss the determination of the marginal tachyon field at R→1R\to 1.Comment: 13 pages, 3 Eps figure

    Black Hole Entropy Function and the Attractor Mechanism in Higher Derivative Gravity

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    We study extremal black hole solutions in D dimensions with near horizon geometry AdS_2\times S^{D-2} in higher derivative gravity coupled to other scalar, vector and anti-symmetric tensor fields. We define an entropy function by integrating the Lagrangian density over S^{D-2} for a general AdS_2\times S^{D-2} background, taking the Legendre transform of the resulting function with respect to the parameters labelling the electric fields, and multiplying the result by a factor of 2\pi. We show that the values of the scalar fields at the horizon as well as the sizes of AdS_2 and S^{D-2} are determined by extremizing this entropy function with respect to the corresponding parameters, and the entropy of the black hole is given by the value of the entropy function at this extremum. Our analysis relies on the analysis of the equations of motion and does not directly make use of supersymmetry or specific structure of the higher derivative terms.Comment: LaTeX file, 12page

    Delocalized, non-SUSY pp-branes, tachyon condensation and tachyon matter

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    We construct non-supersymmetric pp-brane solutions of type II supergravities in arbitrary dimensions (dd) delocalized in one of the spatial transverse directions. By a Wick rotation we convert these solutions into Euclidean pp-branes delocalized in the transverse time-like direction. The former solutions in d=10d=10 nicely interpolate between the (p+1)(p+1)-dimensional non-BPS D-branes and the pp-dimensional BPS D-branes very similar to the picture of tachyon condensation for the tachyonic kink solution on the non-BPS D-branes. On the other hand the latter solutions interpolate between the (p+1)(p+1)-dimensional non-BPS D-branes and the tachyon matter supergravity configuration very similar to the picture of rolling tachyon on the non-BPS D-branes.Comment: 15 pages, typos correcte