I briefly review recent work on the comparison between two and three graviton scattering in supergravity and matrix theory 1 Motivations In the low-energy regime, M-theory is D = 11, N = 1 supergravity. In the matrix model the fundamental degrees of freedom of M-theory are 0-branes (that is, Derichlet particles). For this model to be a correct description of M-theory, it must then reproduce sup...

To describe a massive graviton in 4D Minkowski space-time one introduces a quadratic term in the Lagrangian. This term, however, can lead to a readjustment or instability of the background instead of describing a massive graviton on flat space. We show that for all local Lorentz-invariant mass terms Minkowski space is unstable. We start with the Pauli-Fierz (PF) term that is the only local mass...

A general prediction of the 5-d Randall-Sundrum (RS) hierarchy model is the emergence of spin-2 Kaluza Klein (KK) gravitons with weak scale masses and couplings. The lowest order effective theory of the RS model is given by 5-d Einstein gravity which uniquely fixes the self-interactions of gravitons. We demonstrate that large numbers of light KK resonances could be produced at a future lepton-c...

A general prediction of the 5-d Randall-Sundrum (RS) hierarchy model is the emergence of spin-2 Kaluza Klein (KK) gravitons with weak scale masses and couplings. The lowest order effective theory of the RS model is given by 5-d Einstein gravity which uniquely fixes the self-interactions of gravitons. We demonstrate that large numbers of light KK resonances could be produced at a future lepton-c...

We point out some subtleties with gauge fixings (which sometimes include the so-called “brane bending” effects) typically used to compute the graviton propagator on the Randall-Sundrum brane. In particular, the brane, which has non-vanishing tension, explicitly breaks some part of the diffeomorphisms, so that there are subtleties arising in going to, say, the axial gauge or the harmonic gauge. ...

We have proposed that the cosmic ray spectrum “knee”, the steepening of the cosmic ray spectrum at energy E > ∼ 1015.5 eV, is due to “new physics”, namely new interactions at TeV cm energies which produce particles undetected by the experimental apparatus. In this letter we examine specifically the possibility that this interaction is low scale gravity. We consider that the graviton propagates,...

Instead of imagining space-time as being warped by mass and energy, one can speak of a classical spin-2 graviton field (in flat, Minkowski space-time) that generates gravitation. Although we don’t know yet how to quantize this field, we can think of it in a way similar to how we think of electromagnetism being mediated by photons. And just as a 1/r2 Coulomb force generates magnetism when the fi...

The consequences of abnormally low lithium abundance in a nearby population II star (which is almost as old as the supposed population III stars) as represented by HE0107-5240 are that standard BBN theory is out of sync with observations. Analysis of the big bang nucleosynthesis may help explain the anomalously low value of lithium abundance in the star HE0107-5240, which by orthodox BBN, shoul...

We analyze the propagation of a scalar field in multidimensional theories which include kinetic corrections in the brane, as a prototype for gravitational interactions in a four dimensional brane located in a (nearly) flat extra dimensional bulk. We regularize the theory by introducing an infrared cutoff given by the size of the extra dimensions and a physical ultraviolet cutoff of the order of...

Fhotons can mix with low-mass bosons in the presence of external electromagnetic fields if these particles —not necessarily of spin 1—couple by a two-photon vertex. Important examples are the hypothetical axion (spin 0) and graviton (spin 2). We develop a formalism which is adapted to study the evolution of a photon (axion, graviton) beam in the presence of external fields. We apply our results...