159 citations · 1.6k across the 29 of their papers we have counts for
28 papers · 1 filter
On the weak-gravity bound for a shift-symmetric scalar field
Gustavo P. de Brito, Benjamin Knorr, Marc Schiffer
The weak-gravity bound has been discovered in several asymptotically safe gravity-matter systems. It limits the strength of gravitational fluctuations that are compatible with an u…
Form Factors in Asymptotically Safe Quantum Gravity
Benjamin Knorr, Chris Ripken, Frank Saueressig
Asymptotic Safety implies that observables including scattering amplitudes remain finite at the highest energy scales. Traditionally, this feature is connected to an interacting fi…
Configuration space for quantum gravity in a locally regularized path integral
Benjamin Knorr, Alessia Platania, Marc Schiffer
We discuss some aspects of the metric configuration space in quantum gravity in the background field formalism. We give a necessary and sufficient condition for the parameterizatio…
Cartographing gravity-mediated scattering amplitudes: scalars and photons
Benjamin Knorr, Samuel Pirlo, Chris Ripken +1
The effective action includes all quantum corrections arising in a given quantum field theory. Thus it serves as a powerful generating functional from which quantum-corrected scatt…
Safe essential scalar-tensor theories
Benjamin Knorr
We discuss the renormalisation group flow of all essential couplings of quantum gravity coupled to a shift-symmetric scalar field at fourth order in the derivative expansion. We de…
Sifting quantum black holes through the principle of least action
Benjamin Knorr, Alessia Platania
We tackle the question of whether regular black holes or other alternatives to the Schwarzschild solution can arise from an action principle in quantum gravity. Focusing on an asym…
Form Factors in Quantum Gravity - contrasting non-local, ghost-free gravity and Asymptotic Safety
Benjamin Knorr, Chris Ripken, Frank Saueressig
Form factors constitute the key building block when organising the gravitational dynamics in terms of a curvature expansion. They generalise the concept of momentum-dependent coupl…
Non-perturbative propagators in quantum gravity
Benjamin Knorr, Marc Schiffer
We employ non-perturbative renormalisation group methods to compute the full momentum dependence of propagators in quantum gravity in general dimensions. We disentangle all differe…
The derivative expansion in asymptotically safe quantum gravity: general setup and quartic order
Benjamin Knorr
We present a general framework to systematically study the derivative expansion of asymptotically safe quantum gravity. It is based on an exact decoupling and cancellation of diffe…
Exact solutions and residual regulator dependence in functional renormalisation group flows
Benjamin Knorr
We construct exact solutions to the functional renormalisation group equation of the O(N) model and the Gross-Neveu model at large N for , without specifying the form of the…
Scattering amplitudes in affine gravity
Benjamin Knorr, Chris Ripken
Affine gravity is a connection-based formulation of gravity that does not involve a metric. After a review of basic properties of affine gravity, we compute the tree-level scatteri…
Lessons from conformally reduced quantum gravity
Benjamin Knorr
In this work we study a significantly enlarged truncation of conformally reduced quantum gravity in the context of Asymptotic Safety, including all operators that can be resolved i…
Graviton-Mediated Scattering Amplitudes from the Quantum Effective Action
Tom Draper, Benjamin Knorr, Chris Ripken +1
We employ the curvature expansion of the quantum effective action for gravity-matter systems to construct graviton-mediated scattering amplitudes for non-minimally coupled scalar f…
Finite Quantum Gravity Amplitudes -- no strings attached
Tom Draper, Benjamin Knorr, Chris Ripken +1
We study the gravity-mediated scattering of scalar fields based on a parameterisation of the Lorentzian quantum effective action. We demonstrate that the interplay of infinite towe…
Form Factors in Asymptotic Safety: conceptual ideas and computational toolbox
Benjamin Knorr, Chris Ripken, Frank Saueressig
Over the last years the Asymptotic Safety program has matured into a serious candidate for a quantum theory of gravity compatible with observations. The rapid technical progress in…
Resolving Spacetime Singularities within Asymptotic Safety
Lando Bosma, Benjamin Knorr, Frank Saueressig
A key incentive of quantum gravity is the removal of spacetime singularities plaguing the classical theory. We compute the non-perturbative momentum-dependence of a specific struct…
Momentum dependence of quantum critical Dirac systems
Lennart Dabelow, Holger Gies, Benjamin Knorr
We analyze fermionic criticality in relativistic 2+1 dimensional fermion systems using the functional renormalization group (FRG), concentrating on the Gross-Neveu (chiral Ising) a…
Lorentz symmetry is relevant
Benjamin Knorr
We set up a covariant renormalisation group equation on a foliated spacetime which preserves background diffeomorphism symmetry. As a first application of the new formalism, we stu…
Towards reconstructing the quantum effective action of gravity
Benjamin Knorr, Frank Saueressig
Starting from a parameterisation of the quantum effective action for gravity we calculate correlation functions for observable quantities. The resulting templates allow to reverse-…
Infinite order quantum-gravitational correlations
Benjamin Knorr
A new approximation scheme for nonperturbative renormalisation group equations for quantum gravity is introduced. Correlation functions of arbitrarily high order can be studied by…
Correlation functions on a curved background
Benjamin Knorr, Stefan Lippoldt
We investigate gravitational correlation functions in a curved background with the help of nonperturbative renormalization group methods. Beta functions for eleven couplings are de…
Solving functional flow equations with pseudo-spectral methods
Julia Borchardt, Benjamin Knorr
We apply pseudo-spectral methods to integrate functional flow equations with high accuracy, extending earlier work on functional fixed point equations \cite{Borchardt:2015rxa}. The…
The Gravitational Two-Loop Counterterm is Asymptotically Safe
Holger Gies, Benjamin Knorr, Stefan Lippoldt +1
Weinberg's asymptotic safety scenario provides an elegant mechanism to construct a quantum theory of gravity within the framework of quantum field theory based on a non-Gaußian fix…
Generalized Parametrization Dependence in Quantum Gravity
Holger Gies, Benjamin Knorr, Stefan Lippoldt
We critically examine the gauge, and field-parametrization dependence of renormalization group flows in the vicinity of non-Gaußian fixed points in quantum gravity. While physical…