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Linking covariant and canonical LQG II: spin foam projector
- T. Thiemann, Antonia Zipfel
- Physics
- 22 July 2013
In a seminal paper, Kaminski et al for the first time extended the definition of spin foam models to arbitrary boundary graphs. This is a prerequisite in order to make contact to the canonical…
Emergent four-dimensional linearized gravity from a spin foam model
- Muxin Han, Zichang Huang, Antonia Zipfel
- PhysicsPhysical Review D
- 5 December 2018
Spin Foam Models (SFMs) are covariant formulations of Loop Quantum Gravity (LQG) in 4 dimensions. This work studies the perturbations of SFMs on a flat background. It demonstrates for the first time…
On the relation between reduced quantisation and quantum reduction for spherical symmetry in loop quantum gravity
- N. Bodendorfer, Antonia Zipfel
- Physics
- 1 December 2015
Building on a recent proposal for a quantum reduction to spherical symmetry from full loop quantum gravity, we investigate the relation between a quantisation of spherically symmetric general…
Lorentzian proper vertex amplitude: Classical analysis and quantum derivation
- J. Engle, Antonia Zipfel
- Mathematics
- 16 February 2015
Spin foam models, an approach to defining the dynamics of loop quantum gravity, make use of the Plebanski formulation of gravity, in which gravity is recovered from a topological field theory via…
Linking covariant and canonical loop quantum gravity: New solutions to the Euclidean scalar constraint
- Emanuele Alesci, T. Thiemann, Antonia Zipfel
- Physics
- 6 September 2011
It is often emphasized that spin-foam models could realize a projection on the physical Hilbert space of canonical Loop Quantum Gravity (LQG). As a first test we analyze the one-vertex expansion of a…
Matrix elements of Lorentzian Hamiltonian constraint in loop quantum gravity
- Emanuele Alesci, K. Liegener, Antonia Zipfel
- Physics
- 4 June 2013
The Hamiltonian constraint is the key element of the canonical formulation of LQG coding its dynamics. In Ashtekar-Barbero variables it naturally splits into the so called Euclidean and Lorentzian…
Lorentzian proper vertex amplitude: Asymptotics
- J. Engle, Ilya Vilensky, Antonia Zipfel
- Mathematics
- 25 May 2015
In previous work, the Lorentzian proper vertex amplitude for a spin-foam model of quantum gravity was derived. In the present work, the asymptotics of this amplitude are studied in the semi-classical…
Stable coherent states
- Antonia Zipfel, T. Thiemann
- Physics, Mathematics
- 29 June 2015
We analyze the stability under time evolution of complexifier coherent states (CCS) in one-dimensional mechanical systems. A system of coherent states is called stable if it evolves into another…
Spin foam propagator: A new perspective to include the cosmological constant
- Muxin Han, Zichang Huang, Antonia Zipfel
- Physics
- 30 November 2017
In recent years, the calculation of the first non-vanishing order of the metric 2-point function or graviton propagator in a semiclassical limit has evolved as a standard test for the credibility of…
On the relation of canonical and covariant formulations of Loop Quantum Gravity
- Antonia Zipfel
- Physics
- 11 May 2015
Loop Quantum Gravity (LQG) is a background independent approach towards a quantum theory of gravity that splits into a canonical and a covariant branch the latter of which is also often called spin…
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