1. Towards a Se lf-Consiste nt and Controllable Graviton Flux - Ne Strate Gy; Bernd Binder
The long standing hierarchyp roblem inp articlep h ysics addresses the 19 orders of magnitudes differe nce in interaction between electromagnetic forces and grav itation. Referring to string and conformal field th eories it is commonly agreed that the weakness of gravity can in general be assigned to extra-dimensions (holograp h icp rincip le). But there are nop ractical rules regarding dimensio nal adjustments andp rop er dynamic scaling imp rovin g the coup ling of fields with different dimensionality, i.e. trans forming electromagnetic flux into higher-dimensiona l gravitational fields for sp acep rop ulsionp urp oses. Regarding the flux...

2. "Investigação sobre a interação entre os campos escalar e gravitacional no espaço não comutativo" - Manoel Reinaldo Elias Filho
A formulação de uma teoria da relatividade geral em espaços não-comutativos tem sido investigada usando-se diferentes abordagens atualmente. Neste contexto, é feita uma revisão do formalismo que descreve a não-comutatividade do espaço-tempo. A seguir, são investigadas as interações entre os campos do gráviton e o bóson escalar, formuladas em um espaço comutativo mostrando-se um método alternativo para reescrever a ação desta interação. Finalmente, utilizando-se este método, obtém-se o termo dominante da ação de interação entre os campos do gráviton e escalar em espaços não-comutativos. Deste modo, somos levados a considerar transformações de coordenadas restritas, com parâmetro infinitesimal "~ 'SOBRE' W...

3. On the Size of a Graviton - Nikita A. Nekrasov
. We propose an approximate wavefunction of the bound state of N D0-branes. Its spread grows as N 1 3 per particle, i.e. it saturates the Polchinski's bound. 1. Introduction Denition of M-theory [1][2] using its ten dimensional compactication requires the knowledge of the behaviour of the Kaluza-Klein modes of the graviton. These are realized as the bound states [3] of D0-branes of Type IIA string theory, originally discovered as the black holes in the supergravity [4]. The aim of this paper is to get a good grip on the wavefunction N of the boundstate of N D0-branes, for any N . Of course, the quantum mechanics of N D0-branes contains...

4. Four Graviton Scattering Amplitude From ... Supersymmetric Orbifold Sigma Model
In the IR limit the Matrix string theory is expected to be described by the S N R 8 supersymmetric orbifold sigma model. Recently Dijkgraaf, Verlinde and Verlinde proposed a vertex that may describe the type IIA string interaction. In this paper using this interaction vertex we derive the four graviton scattering amplitude from the orbifold model in the large N limit. Keywords: Matrix string; orbifold conformal field theory. 1 Introduction According to the Matrix theory conjecture [1] the quantum mechanics of N D-particles [2] of type IIA string theory in the large N limit describes the eleven-dimensional dynamics of M-theory [3, 4]. In particular, some subspace of the Hilbert space of...

5. Graviton Production In Elliptical And Hyperbolic Universes - M. R. De Garcia Maia,J. A. S. Lima
The problem of cosmological graviton creation for homogeneous and isotropic universes with elliptical (" = +1) and hyperbolical (" = Gamma1) geometries is addressed. The gravitational wave equation is established for a self-gravitating fluid satisfying the barotropic equation of state p = (fl Gamma 1)ae, which is the source of the Einstein's equations plus a cosmological-term. The time dependent part of this equation is exactly solved in terms of hypergeometric functions for any value of fl and spatial curvature ". An expression representing an adiabatic vacuum state is then obtained in terms of associated Legendre functions whenever fl 6= 2 3 (2n+1) (2nGamma1) , where n is an integer. This includes most cases...

6. General Estimate for the Graviton Lifetime. - Giovanni Modanese,Fohringer Ring,D Munchen (germany
By means of general kinematical arguments, the lifetime ø of a graviton of energy E for decay into gravitons is found to have the form ø Gamma1 = 1 EG P j=1;2;::: c j (G) j . Some recent, preliminary results of non perturbative simplicial quantum gravity are then employed to estimate the effective values of G and G. It turns out that a short lifetime of the graviton cannot be excluded. The recent advances of non perturbative simplicial quantum gravity [1, 2, 3] have made possible a computation of the scale dependence of the Newton constant G and especially of the adimensional product G. In this paper we consider a process, the decay of the...

7. The Graviton
The search is still on for a unifying quantum theory of the gravitational force and hopes are pinned on the graviton - a hypothetical elementary particle that transmits the force of gravity. Why is the search for the graviton a major goal of theoretical physics? How will the measurement of gravitational waves and the detection of supersymmetric partners help prove its existence? And how might the graviton unite the seemingly incompatible theories of general relativity and quantum mechanics? This radio broadcast addresses these questions in an interview format. It is 41 minutes and 43 seconds in length. Educational levels: General...

8. Graviton Physics - Holstein, Barry R.
The interactions of gravitons with matter are calculated in parallel with the familiar photon case. It is shown that graviton scattering amplitudes can be factorized into a product of familiar electromagnetic forms, and cross sections for various reactions are straightforwardly evaluated using helicity methods.

9. Constraints On Inflation At The Planck Scale From The Relic Graviton Spectrum - M. Gasperini,M. Giovannini
Constraints on the maximum allowed scale for de Sitter inflation can be evaded if the de Sitter phase is preceded by an epoch of growing curvature and accelerated expansion (superinflation). In this case the universe can inflate up to a Planckian curvature scale. The duration of the final de Sitter phase, however, turns out to depend crucially on the power-law behaviour of the former superinflationary epoch, and is significatively constrained by the limit imposed by pulsar-timing data on the presently surviving background of cosmic gravitons. ------------------------------------ To appear in Phys.Lett.B 1. Introduction It has been repeatedly stressed [1-4] that the energy distribution of relic gravitons, produced by the cosmological expansion, can...

10. Peak and End Point of the Relic Graviton Background in String Cosmology - R. Brustein,M. Gasperini
Using general arguments we determine the allowed region for the end point frequency and the peak energy density of the stochastic background of gravity waves expected in string cosmology. We provide an accurate estimate of the minimal experimental sensitivity required to detect a signal in the Hz to GHz range. To appear in Phys. Rev. D CERN-TH/96-37 April In a recent paper [1] we computed, in collaboration with M. Giovannini, the spectrum of relic gravity waves produced in the context of the so-called "pre-big-bang" scenario of string cosmology [2, 3]. We showed that the spectral energy density of the produced gravitons grows with frequency following a Rayleigh-Jeans-type behaviour at low...

11. Graviton-Dilaton Cosmology - Rama, S. Kalyana
We show that the evolution of the universe is singularity free in a class of graviton-dilaton models.

12. Theoretical physics - Study of the graviton emission process - Tourrenc, A.
Graviton emission process

13. On the Graviton Mass - Gruzinov, Andrei
It was suggested that observations of the solar system exclude massive gravity, in the sense that the graviton mass must be rigorously zero. This is because there is a discontinuity in the linearized gravity theory at graviton mass equal to zero. The linearized Schwarzschild metric is not recovered for infinitesimal graviton mass, contradicting observations on light deviation by the Sun and Mercury perihelion advance. It was then argued that non-perturbative effects make the massive gravity theory continuous in the graviton mass. Both the original suggestion and its refutation were based on a non-covariant and linearized action, and the physical interpretation of these results remained questionable. Here we use a...

14. Infrared behavior of graviton-graviton scattering - Donoghue, J. F.; Torma, T.
The quantum effective theory of general relativity, independent of the eventual full theory at high energy, expresses graviton-graviton scattering at one loop order O(E^4) with only one parameter, Newton's constant. Dunbar and Norridge have calculated the one loop amplitude using string based techniques. We complete the calculation by showing that the 1/(d-4) divergence which remains in their result comes from the infrared sector and that the cross section is finite and model independent when the usual bremsstrahlung diagrams are included.

15. Factorization in graviton interactions - Choi, S. Y.; Shim, J. S.; Song, H. S.
The study of factorization in the linearized gravity is extended to the graviton scattering processes with a massive scalar particle, with a massless vector boson and also with a graviton. Every transition amplitude is shown to be completely factorized and the physical implications of their common factors are discussed.

16. BGU-PH-96/05 hep-th/9604084 Peak and End Point of the Relic Graviton Background - R. Brustein,M. Gasperini
Using general arguments we determine the allowed region for the end point frequency and the peak energy density of the stochastic background of gravity waves expected in string cosmology. We provide an accurate estimate of the minimal experimental sensitivity required to detect a signal in the Hz to GHz range.

17. Graviton-induced Bremsstrahlung - Dvergsnes, Erik; Osland, Per; Ozturk, Nurcan
We discuss photon Bremsstrahlung induced by virtual graviton exchange in proton-proton interactions at hadronic colliders, resulting from the exchange of Kaluza-Klein excitations of the graviton. The relevant subprocesses, gg to G to e^+e^-gamma and q barq to e^+e^-gamma are discussed in both the ADD and the RS scenarios. Although two-body final states (or real graviton emission) would presumably be the main discovery channels, a search for three-body final states could be worthwhile since such events have characteristic features that could provide additional confirmation. In particular, the k_perp-distribution of the photon is in both scenarios harder than that of the Standard-model background.

18. Mass for the graviton - Visser, Matt
Can we give the graviton a mass? Does it even make sense to speak of a massive graviton? In this essay I shall answer these questions in the affirmative. I shall outline an alternative to Einstein Gravity that satisfies the Equivalence Principle and automatically passes all classical weak-field tests (GM/r approx 10^{-6}). It also passes medium-field tests (GM/r approx 1/5), but exhibits radically different strong-field behaviour (GM/r approx 1). Black holes in the usual sense do not exist in this theory, and large-scale cosmology is divorced from the distribution of matter. To do all this we have to sacrifice something: the theory exhibits {*prior geometry*}, and depends on a...

19. Weakly-coupled metastable graviton - Gabadadze, Gregory
A graviton of a nonzero mass and decay width propagates five physical polarizations. The question of interactions of these polarizations is crucial for viability of models of massive/metastable gravity. This question is addressed in the context of the DGP model of a metastable graviton. First, I argue that the well-known breakdown of a naive perturbative expansion at a low scale is an artifact of the weak-field expansion itself. Then, I propose a different expansion -- the constrained perturbation theory -- in which the breakdown does not occur and the theory is perturbatively tractable all the way up to its natural ultraviolet cutoff. In this approach the couplings of...

20. Model of graviton-dusty universe - Ivanov, Michael A.
Primary features of a new cosmological model, which is based on conjectures about an existence of the graviton background and superstrong gravitational quantum interaction, are considered. An expansion of the universe is impossible in such the model because of deceleration of massive objects by the graviton background, which is similar to the one for the NASA deep space probes Pioneer 10, 11. Redshifts of remote objects are caused in the model by interaction of photons with the graviton background, and the Hubble constant depends on an intensity of interaction and an equivalent temperature of the graviton background. Virtual massive gravitons would be dark matter particles. They transfer energy, lost...

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