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34
BPS Action and Superpotential for Heterotic String Compactifications with Fluxes
, 2003
"... We consider N = 1 compactifications to four dimensions of heterotic string theory in the presence of fluxes. We show that up to order O (α ′2) the associated action can be written as a sum of squares of BPSlike quantities. In this way we prove that the equations of motion are solved by backgrounds ..."
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Cited by 81 (4 self)
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We consider N = 1 compactifications to four dimensions of heterotic string theory in the presence of fluxes. We show that up to order O (α ′2) the associated action can be written as a sum of squares of BPSlike quantities. In this way we prove that the equations of motion are solved by backgrounds which fulfill the supersymmetry conditions and the Bianchi identities. We also argue for the expression of the related superpotential and discuss the radial modulus
Gravity in Warped Compactifications and the Holographic Stress Tensor
, 2001
"... We study gravitational aspects of BraneWorld scenarios. We show that the bulk Einstein equations together with the junction condition imply that the induced metric on the brane satisfies the full nonlinear Einstein equations with a specific effective stress energy tensor. This result holds for any ..."
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Cited by 21 (4 self)
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We study gravitational aspects of BraneWorld scenarios. We show that the bulk Einstein equations together with the junction condition imply that the induced metric on the brane satisfies the full nonlinear Einstein equations with a specific effective stress energy tensor. This result holds for any value of the bulk cosmological constant. The analysis is done by either placing the brane close to infinity or by considering the local geometry near the brane. In the case that the bulk spacetime is asymptotically AdS, we show that the effective stress energy tensor is equal to the sum of the stress energy tensor of matter localized on the brane and of the holographic stress energy tensor appearing in the AdS/CFT duality. In addition, there are specific highercurvature corrections to Einstein’s equations. We analyze in detail the case of asymptotically flat spacetime. We obtain asymptotic solutions of Einstein’s equations and show that the effective Newton’s constant on the brane depends on the position of the brane.
Highenergy black hole production
, 709
"... Abstract. Black hole production in highenergy collisions is briefly surveyed. Included is a summary of recent developments and open problems relevant to collider (LHC) production, as well as of some theoretical issues pointing towards fundamental principles of quantum gravity. ..."
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Cited by 18 (4 self)
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Abstract. Black hole production in highenergy collisions is briefly surveyed. Included is a summary of recent developments and open problems relevant to collider (LHC) production, as well as of some theoretical issues pointing towards fundamental principles of quantum gravity.
Tunneling into Extra Dimension and HighEnergy Violation of Lorentz Invariance
"... We consider a class of models with infinite extra dimension, where bulk space does not possess SO(1,3) invariance, but Lorentz invariance emerges as an approximate symmetry of the lowenergy effective theory. In these models, the maximum attainable speeds of the graviton, gauge bosons and scalar par ..."
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Cited by 16 (2 self)
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We consider a class of models with infinite extra dimension, where bulk space does not possess SO(1,3) invariance, but Lorentz invariance emerges as an approximate symmetry of the lowenergy effective theory. In these models, the maximum attainable speeds of the graviton, gauge bosons and scalar particles are automatically equal to each other and smaller than the maximum speed in the bulk. Additional finetuning is needed in order to assure that the maximum attainable speed of fermions takes the same value. A peculiar feature of our scenario is that there are no truly localized modes. All fourdimensional particles are resonances with finite widths. The latter depends on the energy of the particle and is naturally small at low energies. 1 Introduction and
AdS/CFT and RandallSundrum model without a brane”, hepth 0010141
"... We reformulate the RandallSundrum (RS) model on the compactified AdS by adding a term proportional to the area of the boundary to the usual gravity action with a negative cosmological constant and show that gravity can still be localized on the boundary without introducing singular brane sources. T ..."
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Cited by 5 (0 self)
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We reformulate the RandallSundrum (RS) model on the compactified AdS by adding a term proportional to the area of the boundary to the usual gravity action with a negative cosmological constant and show that gravity can still be localized on the boundary without introducing singular brane sources. The boundary conditions now follow from the field equations, which are obtained by letting the induced metric vary on the boundary. This approach gives similar modes that are obtained in [1] and clarifies the complementarity of the RS and the AdS/CFT pictures. Normalizability of these modes is checked by an innerproduct in the space of linearized perturbations. The same conclusions hold for a massless scalar field in the bulk.
BraneWorld charges
"... As opposed to usual Einstein gravity in four dimensions, the BraneWorld scenario allows the construction of a local density of gravitational energy (and also of momentum, of angular momentum, etc...). This is a direct consequence of the hypothesis that our universe is located at the boundary of a f ..."
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Cited by 3 (2 self)
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As opposed to usual Einstein gravity in four dimensions, the BraneWorld scenario allows the construction of a local density of gravitational energy (and also of momentum, of angular momentum, etc...). This is a direct consequence of the hypothesis that our universe is located at the boundary of a fivedimensional diffeomorphism invariant manifold. We compute these BraneWorld densities of charge using the LanczosIsrael boundary conditions. To proceed, we implement an explicitely covariant generalization of the Hamiltonian procedure of Regge and Teitelboim given in a previous work. We finally study two simple BraneWorld examples. 1 The idea that our fourdimensional universe could be the boundary of a fivedimensional spacetime has been recently revived as an alternative to KaluzaKlein compactification [1]. The classical theory in the bulk is nothing but
Trap Surface Formation in HighEnergy Black Holes Collision
, 2003
"... We investigate classical formation of a trap surface in Ddimensional Einstein gravity in the process of a headon collision of two highenergy particles, which are treated as AichelburgSexl shock waves. From the condition of the trap surface volume local maximality we deduce an explicit form of th ..."
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Cited by 2 (0 self)
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We investigate classical formation of a trap surface in Ddimensional Einstein gravity in the process of a headon collision of two highenergy particles, which are treated as AichelburgSexl shock waves. From the condition of the trap surface volume local maximality we deduce an explicit form of the inner trap surface. Imposing the continuity condition on the fronts we obtain a timedependent solution for the trap surface. We discuss trap surface appearance and evolution. 1
Lensed Density Perturbations in Braneworlds: An Alternative to Perturbations from Inflation
, 2002
"... We consider a scenario in which our observable universe is a 3dimensional surface (3brane) living in extra dimensions with a warped geometry. We show that “lensed ” density perturbations from other branes serve as possible seeds for structure formation on our observable brane (without inflation), ..."
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Cited by 2 (1 self)
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We consider a scenario in which our observable universe is a 3dimensional surface (3brane) living in extra dimensions with a warped geometry. We show that “lensed ” density perturbations from other branes serve as possible seeds for structure formation on our observable brane (without inflation), and, in addition, provide constraints on braneworld scenarios with warped bulk geometry. Due to the warped bulk metric, any perturbation generated on one brane (or in the bulk matter) appears to an observer on a second brane to have a significantly different amplitude. We analyze lensed perturbations in the RandallSundrum type scenarios and the “shortcut metric ” scenarios. For Lorentz violating metrics in the bulk, we find the attractive possibility that large density fluctuations that are causally produced elsewhere can lead to small density fluctuations on our brane on superhorizon (acausal) length scales, as required by structure formation. Our most interesting result is that the “shortcut metrics ” in which geodesics traverse the extra dimensions provide an alternative to inflation with two important features: a possible solution to the horizon problem and a mechanism to generate perturbations necessary for structure formation.
THE COSMOLOGICAL CONSTANT AND THE BRANE WORLD SCENARIO ∗
, 2001
"... Although the cosmological constant has primarily cosmological consequences, its smallness poses one of the basic problems in particle physics. Various attempts have been made to explain this mystery, but no satisfactory solution has been found yet. The appearance of extra dimensions in the framework ..."
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Cited by 1 (0 self)
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Although the cosmological constant has primarily cosmological consequences, its smallness poses one of the basic problems in particle physics. Various attempts have been made to explain this mystery, but no satisfactory solution has been found yet. The appearance of extra dimensions in the framework of brane world systems seems to provide some new ideas to address this problem form a different point of view. We shall discuss some of these new approaches and see whether or not they lead to an improvement of the situation. We shall conclude that we are still far from a solution of the problem. 1