119754631
Equivalence between the semiclassical and effective approaches to gravity
Semiclassical and effective theories of gravitation are quite distinct from each other as far as the approximation scheme employed is concerned. In fact, while in the semiclassical approach gravity is a classical field and the particles and/or remaining fields are quantized, in the effective approach everything is quantized, including gravity, but the Feynman amplitude is expanded in terms of the momentum exchanged between the particles and/or fields. In this paper, we show that these approaches, despite being radically different, lead to equivalent results if one of the masses under consideration is much greater than all the other energies involved.
120819012
SEMICLASSICAL VIOLATION of THE EQUIVALENCE PRINCIPLE IN THE GRAVITATIONAL LENSES REALM
An expression for the gravitational deflection angle of a high-energy massless scalar boson is computed using the JWKB method. The resulting expression depends on the energy of the scalar boson or, equivalently, on its wavelength, even to first order in $\frac{GM}{b}$, where G is Newton's constant, M is the mass of the gravitational source, and b is the impact parameter. On the other hand, combining the expressions for the magnification of two images obtained from a gravitational lens with the classical expression for the cross section, it is found that for purely gravitational scatterings the gravitational cross sections are proportional to the relative intensities. As a consequence of this remarkable proportionality and of the fact that the deflection angle obtained via the JWKB method is energy dependent, we come to the conclusion that chromatic effects in the gravitational lenses at the semiclassical level are possible, which violates the classical equivalence principle. The probability of detecting t...
55221669
Conflict between the classical equivalence principle and quantum mechanics
Group of Field Theory from First Principles Centro Brasileiro de Pesquisas Fisicas CBPF, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro, RJ
36344802
Quantum mechanics versus equivalence principle
Ctr Brasileiro Pesquisas Fis, Lab Fis Expt LAFEX, Grp Field Theory Principles 1, BR-22290180 Rio de Janeiro, Brazil
122728528
Photon mass and gravitational deflection
The deflection of a massive photon by an external gravitational field is energy-dependent. Interesting enough, any massive quantum particle, no matter what its spin is, undergoes dispersive deflection in external gravitational fields. Exploiting the dispersive deflection of the quantized massive electromagnetic radiation by the gravitational field of the Sun, we find an upper bound for the photon mass.
122713426
Is the equivalence principle doomed forever to Dante's Inferno on account of quantum mechanics?
It is commonly assumed that the equivalence principle can coexist without conflict with quantum mechanics. We shall argue here that, contrary to popular belief, this principle does not hold in quantum mechanics. We illustrate this point by computing the second-order correction for the scattering of a massive scalar boson by a weak gravitational field, treated as an external field. The resulting cross-section turns out to be mass-dependent. A way out of this dilemma would be, perhaps, to consider gravitation without the equivalence principle. At first sight, this seems to be a too much drastic attitude toward general relativity. Fortunately, the teleparallel version of general relativity — a description of the gravitational interaction by a force similar to the Lorentz force of electromagnetism and that, of course, dispenses with the equivalence principle — is equivalent to general relativity, thus providing a consistent theory for gravitation in the absence of the aforementioned principle.
123610165
Teorias Semiclássica e Efetiva da Gravitação
119299320
Introduction to Quantum Gravity
In this talk, we give a glimpse of the problems with quantum gravity and some possible solutions.