Results 211 to 220 of about 49,504 (245)
Some of the next articles are maybe not open access.
Functional integrals and canonical quantum gravity
Physical Review D, 1992The functional-integral sum-over-histories formulation of quantum gravity in the canonical Arnowitt-Deser-Misner formalism is examined. Reduced phase-space quantization (RPSQ) is contrasted with Dirac quantization (DQ). While it does not appear that RPSQ is even defined for gravity, there do exist minisuperspace models in which different ...
, Guven, , Ryan
openaire +2 more sources
In earlier companion papers, we showed that non-singular primordial black holes (PBHs) could account for all the dark matter (DM) over a significantly wider mass range compared to Schwarzschild PBHs.
Marco Calzà +3 more
semanticscholar +1 more source
Canonical approach to quantum gravity
Classical and Quantum Gravity, 1987Summary: Dirac's canonical programme for the quantization of gravity is discussed. The order of operators in the `kinetic' part of the generator of normal deformations, \(\hat H_{\perp}\), is chosen to give the Laplace-Beltrami form. This follows from the requirement of invariance of the quantum theory under arbitrary contact transformations of the ...
Christodoulakis, Theodosios +1 more
openaire +2 more sources
Black holes and covariance in effective quantum gravity
Physical Review DThe longstanding issue of general covariance in effective models of quantum gravity is addressed, which arises when canonical quantum gravity leads to a semiclassical model described by an effective Hamiltonian constraint.
Cong Zhang +3 more
semanticscholar +1 more source
1992
Dirac’s theory of constrained Hamiltonian systems is first described, discussing in detail primary and secondary constraints, first-class and second-class constraints, Dirac brackets, effective Hamiltonian, total Hamiltonian and extended Hamiltonian. On quantization, the operator versions of first-class constraints become supplementary conditions on ...
openaire +1 more source
Dirac’s theory of constrained Hamiltonian systems is first described, discussing in detail primary and secondary constraints, first-class and second-class constraints, Dirac brackets, effective Hamiltonian, total Hamiltonian and extended Hamiltonian. On quantization, the operator versions of first-class constraints become supplementary conditions on ...
openaire +1 more source
Testing general covariance in effective models motivated by loop quantum gravity
Classical and quantum gravityIn this work we introduce a criterion for testing general covariance in effective quantum gravity theories. It adapts the analysis of invariance under general spacetime diffeomorphisms of the Einstein–Hilbert action to the case of effective canonical ...
Juan Carlos Del Águila +1 more
semanticscholar +1 more source
Canonical Loop Quantum Gravity
This article presents a comprehensive and self-contained review of Loop Quantum Gravity (LQG), focusing on both its canonical (Hamiltonian) formulation and covariant (spin foam) path integral approach. Beginning with the reformulation of General Relativity using Ashtekar–Barbero variables, it systematically constructs the kinematical Hilbert space ...openaire +1 more source
A constraint on canonical quantum gravity?
Nature, 2003Gamma rays from the γ-ray burst (GRB) 021206 have been reported to be strongly linearly polarized1, with the estimated degree of polarization (80 ± 20%) being close to the absolute maximum of 100% — affording us the opportunity to constrain models of quantum gravity, which has had 1010 years to act on the photons as they travelled towards us.
openaire +1 more source
Canonical Quantum Gravity and Effective Theory
2009Effective actions provide a powerful way to understand low-energy, semiclassical or other regimes of quantum field theories. Although canonical quantum gravity theories, such as loop quantum gravity, are not directly accessible to the usual techniques of computing effective actions, equivalent methods to derive an effective Hamiltonian and effective ...
openaire +1 more source
Quantum guidelines for solid-state spin defects
Nature Reviews Materials, 2021Gary Wolfowicz +2 more
exaly