120 citations · 607 across the 31 of their papers we have counts for
22 papers · 1 filter
Spherically Symmetric Gravity on a Graph I: Theoretical Foundations
Klaus Liegener, Saeed Rastgoo, Jorden Roberts
This manuscript is the first in a series of instalments that investigate spherically symmetric solutions within the effective dynamics program of Loop Quantum Gravity. The choice o…
Quantum speed limit and stability of coherent states in quantum gravity
Klaus Liegener, Łukasz Rudnicki
Utilizing the program of expectation values in coherent states and its recently developed algorithmic tools, this letter investigates the dynamical properties of cosmological coher…
Properties of the Hamiltonian Renormalisation and its application to quantum mechanics on the circle
Benjamin Bahr, Klaus Liegener
We consider the Hamiltonian renormalisation group flow of discretised one-dimensional physical theories. In particular, we investigate the influence the choice of different embeddi…
Algorithmic approach to Cosmological Coherent State Expectation Values in LQG
Klaus Liegener, Łukasz Rudnicki
In the lattice approach to Loop Quantum Gravity on a fixed graph computations tend to be involved and are rarely analytically manageable. But, when interested in the expectation va…
Symmetry restriction and its application to gravity
Wojciech Kamiński, Klaus Liegener
In the Hamiltonian formulation, it is not a priori clear whether a symmetric configuration will keep its symmetry during evolution. In this paper, we give precise requirements of w…
Hamiltonian Renormalisation V: Free Vector Bosons
Klaus Liegener, Thomas Thiemann
In a recent proposal we applied methods from constructive QFT to derive a Hamiltonian Renormalisation Group in order to employ it ultimately for canonical quantum gravity. The prop…
Effective LQC model for k=+1 isotropic cosmologies from spatial discretisations
Klaus Liegener, Stefan Andreas Weigl
The closed, spatially isotropic FLRW universe (k=+1) is endowed with modifications due to a discrete underlying space-structure. Motivated from Loop Quantum Gravity techniques, a f…
Challenges in recovering a consistent cosmology from the effective dynamics of loop quantum gravity
Andrea Dapor, Klaus Liegener, Tomasz Pawłowski
We reexamine a set of existing procedures aimed at recovering the effective description of the dynamics of LQG in the context of cosmological solutions. In particular, the studies…
Some physical implications of regularization ambiguities in SU(2) gauge-invariant loop quantum cosmology
Klaus Liegener, Parampreet Singh
The way physics of loop quantum gravity is affected by the underlying quantization ambiguities is an open question. We address this issue in the context of loop quantum cosmology u…
New Loop Quantum Cosmology Modifications from Gauge-covariant Fluxes
Klaus Liegener, Parampreet Singh
Loop quantum cosmology is a symmetry reduced quantization of cosmological spacetimes based on loop quantum gravity. While it has been successful in resolution of various cosmologic…
Perspectives on the dynamics in a loop quantum gravity effective description of black hole interiors
Mehdi Assanioussi, Andrea Dapor, Klaus Liegener
In the loop quantum gravity context, there have been numerous proposals to quantize the reduced phase space of a black hole, and develop a classical effective description for its i…
Emergent de Sitter epoch of the Loop Quantum Cosmos: a detailed analysis
Mehdi Assanioussi, Andrea Dapor, Klaus Liegener +1
We present a detailed analysis of a quantum model for Loop Quantum Cosmology based on strict application of the Thiemann regularization algorithm for the Hamiltonian in Loop Quantu…
Gauge-invariant bounce from loop quantum gravity
Klaus Liegener, Parampreet Singh
We present a gauge-invariant treatment of singularity resolution using loop quantum gravity techniques with respect to local SU(2) transformations. Our analysis reveals many novel…
Emergent de Sitter epoch of the quantum Cosmos
Mehdi Assanioussi, Andrea Dapor, Klaus Liegener +1
The quantum nature of the Big Bang is reexamined in the framework of Loop Quantum Cosmology. The strict application of a regularization procedure to the Hamiltonian, originally dev…
Hamiltonian Renormalisation II. Renormalisation Flow of 1+1 dimensional free scalar fields: Derivation
Thorsten Lang, Klaus Liegener, Thomas Thiemann
In the companion paper we motivated a renormalisation flow on Osterwalder-Schrader data (OS-data) consisting of 1. a Hilbert space, 2. a cyclic vacuum and 3. a Hamiltonian annihila…
Hamiltonian Renormalisation IV. Renormalisation Flow of D+1 dimensional free scalar fields and Rotation Invariance
Thorsten Lang, Klaus Liegener, Thomas Thiemann
In this article we extend the test of Hamiltonian Renormalisation proposed in this series of articles to the D-dimensional case using a massive free scalar field. The concepts we i…
Hamiltonian Renormalization III. Renormalisation Flow of 1+1 dimensional free scalar fields: Properties
Thorsten Lang, Klaus Liegener, Thomas Thiemann
This is the third paper in a series of four in which a renormalisation flow is introduced which acts directly on the Osterwalder-Schrader data (OS data) without recourse to a path…
Hamiltonian Renormalisation I: Derivation from Osterwalder-Schrader Reconstruction
Thorsten Lang, Klaus Liegener, Thomas Thiemann
A possible avenue towards a non-perturbative Quantum Field Theory (QFT) on Minkowski space is the constructive approach which employs the Euclidian path integral formulation, in th…
Cosmological Coherent State Expectation Values in LQG I. Isotropic Kinematics
Andrea Dapor, Klaus Liegener
This is the first paper of a series dedicated to LQG coherent states and cosmology. The concept is based on the effective dynamics program of Loop Quantum Cosmology, where the clas…
Cosmological Effective Hamiltonian from full Loop Quantum Gravity Dynamics
Andrea Dapor, Klaus Liegener
The concept of effective dynamics has proven successful in LQC, a loop-inspired quantization of cosmological spacetimes. We apply the same idea of its derivation in LQC to the full…
Towards the fundamental spectrum of the Quantum Yang-Mills Theory
Klaus Liegener, Thomas Thiemann
In this work we focus on the quantum Einstein-Yang-Mills sector quantised by the methods of Loop Quantum Gravity (LQG). We point out the improved UV behaviour of the coupled system…
Matrix Elements of Lorentzian Hamiltonian Constraint in LQG
Emanuele Alesci, Klaus Liegener, Antonia Zipfel
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 Euclidea…