Discrete quantum gravity: cosmological examples
نویسندگان
چکیده
منابع مشابه
Quantum gravity and cosmological observations
Quantum gravity places entirely new challenges on the formulation of a consistent theory as well as on an extraction of potentially observable effects. Quantum corrections due to the gravitational field are commonly expected to be tiny because of the smallness of the Planck length. However, a consistent formulation now shows that key features of quantum gravity imply magnification effects on co...
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Just as for non-abelian gauge theories at strong coupling, discrete lattice methods are a natural tool in the study of non-perturbative quantum gravity. They have to reflect the fact that the geometric degrees of freedom are dynamical, and that therefore also the lattice theory must be formulated in a background-independent way. After summarizing the status quo of discrete covariant lattice mod...
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We discuss the causal set approach to discrete quantum gravity. We begin by describing a classical sequential growth process in which the universe grows one element at a time in discrete steps. At each step the process has the form of a causal set and the “completed” universe is given by a path through a discretely growing chain of causal sets. We then introduce a method for quantizing this cla...
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In contrast to scalar and tensor modes, vector modes of linear perturbations around an expanding Friedmann–Robertson–Walker universe decay. This makes them largely irrelevant for late time cosmology, assuming that all modes started out at a similar magnitude at some early stage. By now, however, bouncing models are frequently considered which exhibit a collapsing phase. Before this phase reache...
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A quantum theory of gravity is described in the case of a positive cosmological constant in 3 + 1 dimensions. Both old and new results are described, which support the case that loop quantum gravity provides a satisfactory quantum theory of gravity. These include the existence of a ground state, discoverd by Kodama, which both is an exact solution to the constraints of quantum gravity and has a...
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ژورنال
عنوان ژورنال: Classical and Quantum Gravity
سال: 2003
ISSN: 0264-9381,1361-6382
DOI: 10.1088/0264-9381/20/15/305