相关论文: Graviton-photon production with a massive spin-2 p…
Recent studies have shown that the poor perturbative behavior of General Relativity in the ultraviolet regime may be ameliorated by the existence of a non-Gaussian fixed point which renders the theory asymptotically safe and possibly…
In the linearized theory of gravity coupled to the electromagnetic field, we calculate the cross sections of two processes in which both the gravitational and electromagnetic interactions play a role. Those processes, in which a graviton is…
We find the correct spinor amplitude for a simple photon-mediated process and show that, in contrast, the result for the same process using the standard constructive techniques do not agree with Feynman diagrams when the fermions are…
We consider a simple class of models in which the dark matter, X, is coupled to a new gauge boson, phi, with a relatively low mass (m_phi \sim 100 MeV-3 GeV). Neither the dark matter nor the new gauge boson have tree-level couplings to the…
Weyl fermions of spin $\frac12$ minimally coupled to Einstein's gravity in 4 dimensions cannot be produced purely gravitationally in an expanding Universe at tree level. Surprisingly, as we showed in a recent letter [1], this changes at…
The production and the final abundance of gravitino dark matter appear to depend crucially on the restoration of the global U(1) $R$-symmetry of GMSB sectors in a threefold way. An $R$-symmetric phase effectively suppresses the production…
We investigate the particle production from thermal gravitational annihilation in the very early universe, which is an important contribution for particles that might not be in thermal equilibrium or/and only have gravitational interaction,…
We study a scale invariant two measures theory where a dilaton field \phi has no explicit potentials. The scale transformations include a shift \phi\to\phi+const. The theory demonstrates a new mechanism for generation of the exponential…
General relativity and quantum field theory are the cornerstones of our understanding of physical processes, from subatomic to cosmic scales. While both theories work remarkably well in their tested domains, they show minimal overlap.…
We show that at tree level, on-shell gauge invariance can be used to fully determine the first subleading soft-gluon behavior and the first two subleading soft-graviton behaviors. Our proofs of the behaviors for n-gluon and n-graviton tree…
We discuss the dRGT massive gravity interacting with spin-0, spin-1/2, or spin-1 matter. The effective theory of a massive spin-2 particle coupled to matter particles is constructed directly at the amplitude level. In this setting we…
Gravitino production in the primordial Universe is investigated into details. After briefly reviewing inflation, supersymmetry and supergravity, we first study the scattering of massive W bosons in the thermal bath of particles, during the…
Gravitational positivity bounds are constraints on a renormalizable theory in the presence of a massless graviton, under the assumption that the gravitational theory is ultraviolet-completed by a perturbative string theory. We derive these…
Monochromatic photons could be produced in the annihilation or decay of dark matter particles. At high energies, the search for such line features in the cosmic gamma-ray spectrum is essentially background free because plausible…
We formulate Positivity Bounds for scattering amplitudes including exchange of massless particles. We generalize the standard construction through dispersion relations to include the presence of a branch cut along the real axis in the…
We study the low-energy effective theories of photons and gravitons, matching them at one loop to a UV completion with a massive spinning matter particle. The matter is allowed to have non-minimal electromagnetic and gravitational…
The possibility that around some astrophysical objects there are non-static magnetic fields of enormous intensity suggests that in these situations real particles may be produced. The slowness of the variation is compensated by the huge…
We consider the production process e-e+ -> G\gamma of invisible gravitons (G) at future linear colliders. We discuss whether the angular distribution of the photon (\gamma) can be used to measure the spin of the invisible graviton, or of…
We have performed a search for new particles which decay to two photons using 1.2/fb of integrated luminosity from p-pbar collisions at sqrt(s) = 1.96 TeV collected using the CDF II Detector at the Fermilab Tevatron. We find the diphoton…
The existence of a new, photon-like, massive particle, the gamma' or dark photon, is postulated in several extensions of the Standard Model. These models are often advocated to explain some recent puzzling astrophysical observations, as…