2,122 research outputs found
Bohmian quantum gravity and cosmology
Quantum gravity aims to describe gravity in quantum mechanical terms. How
exactly this needs to be done remains an open question. Various proposals have
been put on the table, such as canonical quantum gravity, loop quantum gravity,
string theory, etc. These proposals often encounter technical and conceptual
problems. In this chapter, we focus on canonical quantum gravity and discuss
how many conceptual problems, such as the measurement problem and the problem
of time, can be overcome by adopting a Bohmian point of view. In a Bohmian
theory (also called pilot-wave theory or de Broglie-Bohm theory, after its
originators de Broglie and Bohm), a system is described by certain variables in
space-time such as particles or fields or something else, whose dynamics
depends on the wave function. In the context of quantum gravity, these
variables are a space-time metric and suitable variable for the matter fields
(e.g., particles or fields). In addition to solving the conceptual problems,
the Bohmian approach yields new applications and predictions in quantum
cosmology. These include space-time singularity resolution, new types of
semi-classical approximations to quantum gravity, and approximations for
quantum perturbations moving in a quantum background.Comment: 45 pages, 6 figures, PDFLaTeX; written for "Applied Bohmian
Mechanics: From Nanoscale Systems to Cosmology", edited by Xavier Oriols
Pladevall and Jordi Mompart; v2 typos correcte
Gravitational wave background in perfect fluid quantum cosmologies
We discuss the gravitational wave background produced by bouncing models
based on a full quantum evolution of a universe filled with a perfect fluid.
Using an ontological interpretation for the background wave function allows us
to solve the mode equations for the tensorial perturbations, and we find the
spectral index as a function of the fluid equation of state.Comment: 12 pages, 5 figures, to appear in Phys. Rev. D (2006
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