Semiclassical gravity
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An Asymptotically Safe Guide to Quantum Gravity and Matter Open
Asymptotic safety generalizes asymptotic freedom and could contribute to understanding physics beyond the Standard Model. It is a candidate scenario to provide an ultraviolet extension for the effective quantum field theory of gravity thro…
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Gravitational decoherence Open
We discuss effects of loss of coherence in low energy quantum systems caused by or related to gravitation, referred to as gravitational decoherence. These effects, resulting from random metric fluctuations, for instance, promise to be acce…
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Quadratic Gravity Open
Adding terms quadratic in the curvature to the Einstein-Hilbert action renders gravity renormalizable. This property is preserved in the presence of the most general renormalizable couplings with (and of) a generic quantum field theory (QF…
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Global flows in quantum gravity Open
We study four-dimensional quantum gravity using non-perturbative renormalization group methods. We solve the corresponding equations for the fully momentum-dependent propagator, Newton's coupling and the cosmological constant. For the firs…
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Weak gravity conjecture Open
The weak gravity conjecture holds that in a theory of quantum gravity any gauge force must mediate interactions stronger than gravity for some particles. This statement has surprisingly deep and extensive connections to many different area…
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Islands in asymptotically flat 2D gravity Open
The large-$\\textit{N}$ limit of asymptotically flat two-dimensional dilaton gravity coupled to $\\textit{N}$ free matter fields provides a useful toy model for semiclassical black holes and the information paradox. Analyses of the asympto…
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Testing gravity with cold atom interferometry: results and prospects Open
Atom interferometers have been developed in the last three decades as new powerful tools to investigate gravity. They were used for measuring the gravity acceleration, the gravity gradient, and the gravity-field curvature, for the determin…
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Aspects of asymptotic safety for quantum gravity Open
We study fixed points of quantum gravity with renormalisation group methods, and a procedure to remove convergence-limiting poles from the flow. The setup is tested within the $f(R)$ approximation for gravity by solving exact recursive rel…
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Semiclassical 3D gravity as an average of large-c CFTs Open
A bstract A two-dimensional CFT dual to a semiclassical theory of gravity in three dimensions must have a large central charge c and a sparse low energy spectrum. This constrains the OPE coefficients and density of states of the CFT via th…
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Planck star tunneling time: An astrophysically relevant observable from background-free quantum gravity Open
A gravitationally collapsed object can bounce-out from its horizon via a\ntunnelling process that violates the classical equations in a finite region.\nSince tunnelling is a non-perturbative phenomenon, it cannot be described in\nterms of …
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Quantum gravity fluctuations flatten the Planck-scale Higgs potential Open
We investigate asymptotic safety of a toy model of a singlet-scalar extension\nof the Higgs sector including two real scalar fields under the impact of\nquantum-gravity fluctuations. Employing functional renormalization group\ntechniques, …
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Sourcing semiclassical gravity from spontaneously localized quantum matter Open
The possibility that a classical space-time and quantum matter cohabit at the\ndeepest level, i.e. the possibility of having a fundamental and not\nphenomenological semiclassical gravity, is often disregarded for lack of a good\ncandidate …
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Low-energy effects in a higher-derivative gravity model with real and complex massive poles Open
The most simple superrenormalizable model of quantum gravity is based on the general local covariant six-derivative action. In addition to graviton such a theory has massive scalar and tensor modes. It was shown recently that in the case w…
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Cosmological implications of modified gravity induced by quantum metric fluctuations Open
\n We investigate the cosmological implications of modified gravities induced by the quantum fluctuations of the gravitational metric. If the metric can be decomposed as the sum of the classical and of a fluctuating part, of quantum origin…
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Stellar Equilibrium in Semiclassical Gravity Open
The phenomenon of quantum vacuum polarization in the presence of a gravitational field is well understood and is expected to have a physical reality, but studies of its backreaction on the dynamics of spacetime are practically nonexistent …
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Dissecting the ensemble in JT gravity Open
A bstract We calculate bulk and boundary correlators in JT gravity by summing over geometries. The answers are reproduced by computing suitable ensemble averages of correlators of chaotic quantum systems. We then consider bulk correlators …
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Bulk entanglement gravity without a boundary: Towards finding Einstein’s equation in Hilbert space Open
We consider the emergence from quantum entanglement of spacetime geometry in a bulk region. For certain classes of quantum states in an appropriately factorized Hilbert space, a spatial geometry can be defined by associating areas along co…
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Dark Energy from Quantum Gravity Discreteness Open
We argue that discreteness at the Planck scale (naturally expected to arise from quantum gravity) might manifest in the form of minute violations of energy-momentum conservation of the matter degrees of freedom when described in terms of (…
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Cosmological perturbations from full quantum gravity Open
The early universe provides an opportunity for quantum gravity to connect to\nobservation by explaining the large-scale structure of the Universe. In the\ngroup field theory (GFT) approach, a macroscopic universe is described as a GFT\ncon…
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On the corpuscular theory of gravity Open
The aim of this work is to provide a general description of the corpuscular theory of gravity. After reviewing some of the major conceptual issues emerging from the semiclassical and field theoretic approaches to Einstein’s gravity, we pre…
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Phenomenological investigation of a quantum gravity extension of inflation with the Starobinsky potential Open
We investigate the pre-inflationary dynamics of inflation with the Starobinsky potential, favored by recent data from the Planck mission, using techniques developed to study cosmological perturbations on quantum spacetimes in the framework…
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Gauge assisted quadratic gravity: A framework for UV complete quantum gravity Open
We discuss a variation of quadratic gravity in which the gravitational interaction remains weakly coupled at all energies, but is assisted by a Yang-Mills gauge theory which becomes strong at the Planck scale. The Yang-Mills interaction is…
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What is the entropy in entropic gravity? Open
We explore theories in which gravity arises as a consequence of entropy. We distinguish between two approaches to this idea: holographic gravity, in which Einstein’s equation arises from keeping entropy stationary in equilibrium under vari…
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Essential Quantum Einstein Gravity Open
The non-perturbative renormalisation of quantum gravity is investigated allowing for the metric to be reparameterised along the RG flow, such that only the essential couplings constants are renormalised. This allows us to identify a univer…
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Complex critical points and curved geometries in four-dimensional Lorentzian spinfoam quantum gravity Open
This paper focuses on the semiclassical behavior of the spinfoam quantum\ngravity in 4 dimensions. There has been long-standing confusion, known as the\nflatness problem, about whether the curved geometry exists in the semiclassical\nregim…
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Black hole solutions in the quadratic Weyl conformal geometric theory of gravity Open
We consider numerical black hole solutions in the Weyl conformal geometry and its associated conformally invariant Weyl quadratic gravity. In this model, Einstein gravity (with a positive cosmological constant) is recovered in the spontane…
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Nonlinear stability in nonlocal gravity Open
We address the stability issue of Ricci-flat and maximally symmetric spacetimes in nonlocal gravity to all perturbative orders in the gravitational perturbation. Assuming a potential at least cubic in curvature tensors but quadratic in the…
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Principle of least decoherence for Newtonian semiclassical gravity Open
Recent works have proved that semi-classical theories of gravity needed not\nbe fundamentally inconsistent, at least in the Newtonian regime. Using the\nmachinery of continuous measurement theory and feedback, it was shown that one\ncould …
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Critical Collapse of a Scalar Field in Semiclassical Loop Quantum Gravity Open
We study the collapse in spherical symmetry of a massless scalar field minimally coupled to gravity using the semiclassical equations that are expected from loop quantum gravity. We find the critical behavior of the mass as a function of t…
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Beyond-one-loop quantum gravity action yielding both inflation and late-time acceleration Open
A unified description of early-time inflation with the current cosmic\nacceleration is achieved by means of a new theory that uses a quadratic model\nof gravity, with the inclusion of an exponential $F(R)$-gravity contribution\nfor dark en…