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Complex Ashtekar Variables and Reality Conditions for Holst’s Action
- W. Wieland
- Physics
- 8 December 2010
From the Holst action in terms of complex valued Ashtekar variables, additional reality conditions mimicking the linear simplicity constraints of spin-foam gravity are found. In quantum theory with…
Horizon energy as the boost boundary term in general relativity and loop gravity
- Eugenio Bianchi, W. Wieland
- Physics
- 24 May 2012
We show that the near-horizon energy introduced by Frodden, Ghosh and Perez arises from the action for general relativity as a horizon boundary term. Spin foam variables are used in the analysis. The…
Twistorial structure of loop-gravity transition amplitudes
- Simone Speziale, W. Wieland
- Physics
- 26 July 2012
The spin foam formalism provides transition amplitudes for loop quantum gravity. Important aspects of the dynamics are understood, but many open questions are pressing on. In this paper we address…
Twistorial phase space for complex Ashtekar variables
- W. Wieland
- Mathematics
- 25 July 2011
We generalize the SU(2) spinor framework of twisted geometries developed by Dupuis, Freidel, Livine, Speziale and Tambornino to the Lorentzian case, that is the group . We show that the phase space…
Spin connection of twisted geometry
- Hal M Haggard, C. Rovelli, F. Vidotto, W. Wieland
- Mathematics
- 9 November 2012
Twisted geometry is a piecewise-flat geometry less rigid than Regge geometry. In Loop Gravity, it provides the classical limit for each step of the truncation utilized in the definition of the…
Cosmological evolution as squeezing: a toy model for group field cosmology
- Eugene Adjei, Steffen Gielen, W. Wieland
- Physics
- 19 December 2017
We present a simple model of quantum cosmology based on the group field theory (GFT) approach to quantum gravity. The model is formulated on a subspace of the GFT Fock space for the quanta of…
Fock Representation of Gravitational Boundary Modes and the Discreteness of the Area Spectrum
- W. Wieland
- Physics
- 1 June 2017
In this article, we study the quantum theory of gravitational boundary modes on a null surface. These boundary modes are given by a spinor and a spinor-valued two-form, which enter the gravitational…
First-order formulation of teleparallel gravity and dual loop gravity
- M. Dupuis, F. Girelli, A. Osumanu, W. Wieland
- Geology, PhysicsClassical and Quantum Gravity
- 6 June 2019
There are at least two ways to encode gravity into geometry: Einstein's general theory of relativity (GR) for the metric tensor, and teleparallel gravity, where torsion as opposed to curvature…
Null infinity as an open Hamiltonian system
- W. Wieland
- PhysicsJournal of High Energy Physics
- 3 December 2020
Abstract
When a system emits gravitational radiation, the Bondi mass decreases. If the Bondi energy is Hamiltonian, it can thus only be a time-dependent Hamiltonian. In this paper, we show that the…
Discrete gravity as a topological field theory with light-like curvature defects
- W. Wieland
- Physics
- 9 November 2016
A bstractI present a model of discrete gravity as a topological field theory with defects. The theory has no local degrees of freedom and the gravitational field is trivial everywhere except at a…
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