FAU² Workshop: Quantum Gravity Meets Quantum Information – Foundations, Frameworks and Frontiers

7 Jul 2026, 00:00 → 9 Jul 2026, 22:00 Europe/Berlin

ECAP Laboratory Building

The workshop "FAU²: Quantum Gravity Meets Quantum Information – Foundations, Frameworks and Frontiers” focuses on the rapidly developing interface between quantum gravity, quantum foundations, and quantum information theory. Recent advances have shown that concepts such as quantum reference frames, entanglement and geometry, quantum thermodynamics in gravitational settings, measurement and observers in diffeomorphism-invariant systems, black hole information, and open quantum systems offer new insights into the structure of spacetime and the formulation of gravitational dynamics. At the same time, gravitational physics poses profound foundational challenges to quantum theory, particularly regarding time, subsystems, and the role of information.

The workshop brings together researchers from these areas to exchange perspectives, establish a shared conceptual framework, and discuss both foundational and technical developments. Topics will include quantum gravity theories and relation with information and philosophy, holography, relational approaches, decoherence, quantum clocks, and information-theoretic aspects of emergent geometry. By promoting focused interdisciplinary dialogue and identifying common research directions, the meeting aims to clarify open questions and initiate new collaborations.

Confirmed invited speakers include:

• Mehdi Assanioussi (NCBJ, Warsaw)
• Eugenio Bianchi (Pennsylvania State University)
• Caslav Brukner (IQOQI, Universität Wien, remotely)
• Gemme Des Les Coves (Universitat Pompeu Fabra in Barcelona, remotely)
• Max Fahn (Università di Bologna, remotely)
• Flaminia Giacomini (Università di Roma Tor Vergata, remotely)
• Stephan Hartmann (LMU München)
• Philipp Höhn (OIST, remotely)
• Yichen Hu (Florida Atlantic University)
• Viktoria Kabel (ETH)
• Joshua Kirklin (Perimeter Institute for Theoretical Physics)
• Eduardo Martin-Martinez (University of Waterloo)
• Fabio Mele (Louisiana State University)
• Daniele Oriti (Universidad Complutense de Madrid)
• Lin-Qing Chen (IQOQI)
• Kasia Rejzner (University of York)
• Carlo Rovelli (Centre de Physique Théorique, AMU University, Perimeter Institute, Santa Fe Institute, Rotman Institute, remotely)
• Alexander Stottmeister (Universität Hannover)
• Thomas Thiemann (FAU Erlangen-Nürnberg)
• Wolfgang Wieland (FAU Erlangen-Nürnberg)

 

 

Organizers: Francesco Fazzini, Kristina Giesel and Muxin Han 

     

 

Tuesday 7 July

10:00 → 11:00 Registration

11:00 → 12:30 0: Lunch at cafeteria optional (voucher provided)

12:30 → 14:30 1 Tue: Session 1 Tue

12:30 Local Operations and Field Mediated Entanglement without a Local Tensor Product Structure (online)

Quantum information has become a powerful tool for probing the structure of quantum field theories, yet its application to gauge theories remains subtle. On the one hand, quantum information theory assumes subsystem locality, i.e. the factorization of the total Hilbert space into subsystems. On the other hand, gauge constraints prevent the total Hilbert space to decompose into a spacetime-local tensor product structure. Because the Hilbert space structure of gauge theories does not accommodate the subsystem decomposition used in quantum information theory, standard information-theoretic results, such as the Local Operations and Classical Communication (LOCC) theorem, cannot be used straightforwardly in the context of gauge theories. In my talk, I will show how to bridge this gap in the case of a two-dimensional lattice gauge model that captures key features of electromagnetism. In particular, we construct gauge-invariant local algebras and derive a physically meaningful decomposition of the Hilbert space, providing an operationally consistent notion of locality in the absence of a local tensor-product structure. We apply this framework to field-mediated entanglement protocols relevant to proposed tests of the quantum nature of gravity. We show that the discretized version of electromagnetism satisfies an analogue of the LOCC theorem: entanglement cannot be generated without genuine quantum field interactions, even in the absence of a spacetime-local tensor product factorization of the Hilbert space. This may point towards an operational way to define a subsystem structure for gauge theories.

Speaker: Flaminia Giacomini (University of Rome Tor Vergata)

13:10 When Born Probabilities Become Quantum Observables (online)

Quantum theory denies jointly well-defined outcomes for incompatible measurements, but still assumes jointly well-defined Born probabilities. We argue that this second form of joint definiteness relies on the idealization of a classical reference frame. If relative frequencies are defined with respect to a finite quantum reference frame, their large-run limits can become incompatible observables, obeying uncertainty relations and violating Bell inequalities. This suggests that, where ideal reference frames are unavailable, the quantum state may need to encode a “probability of probabilities.” We close by discussing why such a possibility may be relevant for quantum gravity.

Speaker: Caslav Brukner

13:50 Quantum Reference Fields Transformations in Linearized Quantum Gravity

Diffeomorphism invariance is a central feature of general relativity. Without external reference structures, matter and geometry must be specified relationally, with respect to internal subsystems serving as reference frames. In quantum gravity, these reference systems must themselves be treated as quantum, motivating the use of quantum reference frames. In this work, we address how such a relational description could be formulated within linearized quantum gravity. To this purpose, we introduce quantum reference fields, i.e. sets of four dynamical scalar fields whose stress-energy tensors enter the gravitational constraints. These fields extend the notion of quantum reference frames to local field-theoretic reference systems, allowing matter and gravitational degrees of freedom to be described relationally with respect to physical quantum systems. By generalizing the perspective-neutral construction of quantum reference frames, we show that relational, gauge invariant observables admit reduced descriptions in the perspective of each quantum reference field, and we derive the unitary transformations relating them. The resulting unitary maps implement local quantum coordinate changes between different internal perspectives, and act on the linearized gravitational field with an analogous structure to a linearized diffeomorphism, but with the classical gauge parameter replaced by a physical quantum field. Finally, we construct a relational von Neumann-type measurement scheme, showing how the corresponding reduced observables can be accessed operationally from the perspective of a quantum reference field.

Speaker: Lin-Qing Chen (IQOQI-Vienna)

14:30 → 15:00 Coffee break

15:00 → 17:00 3 Tue: Session 2 Tue

15:00 Mutual Information Across QRF Perspectives

In quantum information theory, most standard notions depend crucially on how we partition the world into subsystems, a choice encoded in the tensor product structure of the Hilbert space. Yet, the subsystem structure has been shown to depend on the choice of quantum reference frame (QRF). This observation underlies many interesting features of QRFs, such as the relativity of entanglement, entropy, and coherence. It also raises a broader question: to what extent can quantum information measures be extended to regimes in which no fixed tensor product structure is available?

In this talk, we will address this question for quantum mutual information - the measure of the information that is “shared” between two systems. In order to formulate a notion of mutual information across different QRF perspectives, we focus on algebras of observables rather than tensor product structures - in line with the extension of these notions to quantum field theory. Moreover, we argue that it is advantageous to focus on information rather than entropy when working with more general subsystems. Based on these two observations, we propose a notion of mutual information between subsystems relative to different reference frames. Investigating this question not only sheds light on some important features of quantum information that also arise in recent discussions of the observer-dependence of gravitational entropy, but also provides a way to quantify what it means to be in the perspective of a QRF from an information-theoretic point of view.

Speaker: Viktoria Kabel

15:40 Classical Gravity Meets Classical Information

As two classical black holes inspiral and merge, they emit a significant amount of energy and angular momentum in the form of gravitational waves—a phenomenon now routinely observed by the LIGO-Virgo-KAGRA collaboration. Predicting the mass and spin of the final black hole typically requires solving Einstein’s equations through highly accurate numerical-relativity simulations. Surprisingly, recent work (https://arxiv.org/abs/2601.22388) has shown that the mass and the spin of the final black hole can also be predicted by a maximum entropy principle. In this talk I discuss the notion of entropy of the classical gravitational field and argue that black hole mergers provide a striking example of how classical gravity meets classical information.

Speaker: Eugenio Bianchi (Penn State)

16:20 TBA

Speaker: Kasia Rejzner

17:00 → 17:30 Coffee break

17:30 → 19:30 3 Tue

17:30 Covariant quantization of perturbative gravitational null rays

I’ll describe recent work with Laurent Freidel in which we quantize the perturbative gravitational data on a null ray in a gauge-invariant manner. The main technical difficulty is due to anomalies in quantum diffeomorphism invariance. I'll explain how these originate in the use of a background time dependent renormalization procedure, and I’ll describe how to eliminate the anomalies by replacing the background time with a dynamical time (the dressing time), thus invoking a quantum reference frame (QRF) dependent renormalization prescription. The fluctuations of the QRF have implications for QG observables. The algebra of non-anomalous gauge invariant operators obtained in this way has the structure of a Virasoro crossed product.

Based on:
https://arxiv.org/abs/2510.26589
https://arxiv.org/abs/2604.02228

Speaker: Josh Kirklin (Perimeter Institute)

18:10 Reduced phase space quantisation and quantum reference frames

Abstract:
Reduced phase space quantisation of general relativity is a promising route to
quantum gravity. We show that this offers a natural interface with quantum reference frames. The talk focuses on conceptual ideas and connections with related
research areas such as constraint quantisation, relational and Dirac observables and addresses some frequently asked questions that arise in this context.

Speaker: Thomas Thiemann (FAU Erlangen-Nuremberg)

18:50 Quantum Reference Frames and Relational Entanglement Entropy

At the interface of quantum gravity and quantum information, growing evidence suggests that spacetime structure can be understood through quantum information-theoretic notions, with entanglement playing a central role. Yet, in the presence of gauge or diffeomorphism constraints, the notion of subsystems, crucial to define entanglement, becomes subtle: the Hilbert space does not factorize, and even when reduced density matrices can be defined, their von Neumann entropy does not capture operational entanglement.

I will argue that quantum reference frames (QRFs) provide a natural resolution of this problem. In lattice gauge theories, using internal degrees of freedom as reference frames, we can define relational subsystems (relative to the frame) that admit a clean Hilbert space factorization, together with a notion of distillable entanglement entropy. Different choices of frame give rise to a hierarchy of relational operator algebras, offering new insights into the role of edge modes, boundary symmetries, and observers in diffeomorphism-invariant systems, while recovering previous constructions within a unified perspective.

Speaker: Francesco Sartini (OIST)

19:30 → 20:30 Final Discussion with all speakers of the day

20:30 → 23:00 Poster Session: welcome get together with drinks and snacks

Wednesday 8 July

11:00 → 12:00 0: Lunch at cafeteria optional (voucher provided)

12:00 → 14:20 9 Thu: Session 4 Wed

12:00 Rethinking coarse graining relationally in quantum gravity (online)

In quantum field theory, coarse graining (or renormalization) is a well-established procedure: physics is formulated on a fixed spacetime background, correlators are computed between fields at different points, and the renormalization group organizes physics in terms of length scales defined by external rulers. In quantum gravity, this framework has to be reconsidered: there is no fixed background geometry and no external notion of scale. After introducing the renormalization group in quantum gravity, with an emphasis on asymptotic safety, I will discuss how a relational perspective changes the notion of coarse graining, allowing it to acquire a more physical meaning in a quantum gravity context.

Speaker: Renata Ferrero

12:40 Panel: Bridging Quantum Gravity and Quantum Information: Lin-Qing Chen, Philipp Höhn, Wolfgang Wieland

13:40 Tractatus Quanticus

With Niccolò Covoni and Andrea di Biagio, we are finishing a book merging our previous works in philosophy and mathematics, on the best way to think the relational view of quantum mechanics. To this aim, we have re-edited Wittgenstein celebrated "Tractatus", taking the Quantum into account. I illustrate our results, synthesized in the 7 propositions:
1. The world is everything that is the case from a perspective.
2. My knowledge about the world is a particular kind of perspective.
3. Perspectives themselves are facts, when considered from another perspective.
4. Facts can be expressed as values of variables, which are ways systems interact.
5. Perspectives are transparent to one another, because they are facts.
6. There is nothing wrong in circularity.
7. What we cannot have information about, we must pass over in silence.

Speaker: Carlo Rovelli (Aix-Marseille University)

14:20 → 14:50 Coffee break

14:50 → 16:50 9 Thu: 5 Wed

14:50 Localised Quantum Reference Fields

Quantum reference frames (QRFs) are internal subsystems that transform non-trivially under a symmetry group and provide the means to describe quantum systems "from the inside" in purely relational terms. QRFs are therefore essential whenever no external reference frame for the relevant symmetry group is available. As such, they play a central role in several research areas, ranging from quantum foundations and quantum information to gauge theory and (quantum) gravity.


However, QRFs have so far been developed primarily in quantum-mechanical settings, while much less is understood about their formulation in quantum field theory (QFT). In this talk, based on ongoing work with Ivan Agullo, I will introduce a notion of localised quantum reference fields in linear QFT. These are localised finite-dimensional subsystems of a quantum field theory that allow quantum fields to be described "from the inside". Focusing on the simple example of a real massless scalar field in 1+1-dimensional Minkowski spacetime, I will illustrate how some of the key features of the QRF programme, such as the quantum relativity of subsystems, also arise in QFT.

Speaker: Fabio Mele (LSU)

15:30 Reduced Quantum-Reference-Frame Channels for Open Quantum Systems

The subsystem structure of quantum theory is relative to the choice of quantum reference frame (QRF). This raises a basic question for open quantum systems: is decoherence an intrinsic property of the system–environment interaction, or can part of it arise from the physical reference frame used to describe the system?

I will address this question through reduced quantum-reference-frame channels: completely positive trace-preserving maps obtained by performing a QRF transformation and then discarding inaccessible reference and environmental degrees of freedom. These channels capture the operational reduced description available to an observer after a change of frame, and allow one to characterize which features of an open-system dynamics are robust under changes of QRF.

I will apply the framework to pure dephasing dynamics, identifying a necessary and sufficient condition for its population structure to be preserved under changes of QRF. In particular, when the energy decomposition is preserved, coherences acquire an additional reference-dependent factor, leading to a split between environmental and reference-induced decoherence rates.

I will conclude with the operational interpretation of this split in Ramsey interferometry and with a gravity-motivated dephasing model, where degradation of a quantum phase reference can reproduce signatures usually associated with intrinsic decoherence.

Speaker: Paolo Luppi (University of Milan)

16:10 Physical projector and spectrum of kinematical operators

The physical projector (or rigging map in Refined Algebraic Quantization) is a powerful tool in the quantisation of constrained systems. In this talk, we argue that the physical projector alone —even without well-defined quantum constraint operators— is sufficient to define physical states and physical observables, within an framework alternative to the relational approach.

This viewpoint is motivated by the longstanding heuristic interpretation of the gravitational path integral as a projector onto the solutions of the Wheeler–DeWitt equation. We provide strong support for this idea by showing that spin-foam amplitudes always define a rigging map,

Speaker: Matteo Bruno (Centre de Physique Théorique (CPT))

16:50 → 17:20 Coffee break

17:20 → 19:20 8 Thu: 6 Wed

17:20 The large-scale structures of entanglement

Quantum systems with unboundedly many degrees of freedom may exhibit large-scale structures in their entanglement properties. The emergence of these structures is comparable to the emergence of sharp macroscopic properties in the thermodynamic limit. A particular example is the embezzlement of entanglement, first discovered by van Dam and Hayden in an approximate form.
In the first part of this talk, I will discuss the intimate relation of this effect with the classification of von Neumann algebras, specifically, Connes’ classification of type III factors.
In the second part, I will illustrate that this effect is ubiquitous in quantum many-body systems and quantum field theory.
Based on joint work with Lauritz van Luijk, Reinhard F. Werner, and Henrik Wilming.

Speaker: Alexander Stottmeister

18:00 Imprints of different descriptions of (quantum) gravity on gravitational decoherence models (online)

This talk discusses two scenarios in which quantum systems interact with gravity. The central question is to which extend different descriptions of the (quantum) gravitational sector leave distinct imprints on the effective dynamics of the quantum system, particularly on the resulting decoherence.
The first part considers two quantum mechanical toy models describing a neutrino which propagates in an environment representing gravitational waves. This environment is described by a bath of harmonic oscillators in Schrödinger quantisation. The interaction is realised either through a linear coupling to the oscillators' position operators or to their Weyl elements. The latter provides a first step towards a polymer quantisation, which is unitarily inequivalent to the Schrödinger quantisation and inspired by loop quantum gravity. Within the parameter regime investigated, comparing the resulting neutrino dynamics shows that the decoherence pattern in the oscillation probabilities differs perturbatively between the two models.
The second part focuses on the decoherence of a spatial superposition in the presence of a black-hole horizon. While a horizon with underlying classical geometry yields an unavoidable decoherence of the superposition, the implementation of a minimal area gap for the horizon, interpreted as an effective description of a quantum horizon geometry, suppresses the decoherence. For an area gap of the order of the Planck length squared, the resulting decoherence becomes negligibly small.
Together, these two scenarios illustrate how different descriptions of the (quantum) gravitational sector can leave distinct imprints on decoherence phenomena in quantum systems.

Speaker: Max Joseph Fahn (University of Bologna and INFN Bologna)

18:40 Entangling Interactions and the Meaning of Quantumness (online)

Entanglement generation is often regarded as evidence that the interaction responsible for it is quantum, and has become a central ingredient in many recent proposals to probe the quantum nature of gravity and other fundamental interactions. In this talk we revisit this intuition by asking a simple question: what features of an interaction are truly required to generate entanglement? We discuss how two quantum systems can become entangled through interactions that admit effective descriptions without local quantum mediators, and how such descriptions can reproduce the predictions of fully quantum field-theoretic models within their regime of validity. We then show where these effective descriptions inevitably fail, revealing the role of relativistic causality in delimiting their validity and clarifying what entanglement generation can (and cannot) tell us about the quantumness of the underlying interaction. Together, these results provide a more nuanced perspective on mediator-free models, the quantum channels they enable, and the operational meaning of quantum interactions, thereby sharpening the theoretical framework for interpreting (and improving the design of) future experiments that probe the quantum nature of gravity.

Speaker: Eduardo Martin-Martinez (University of Waterloo)

19:20 → 20:00 Final Discussion with all speakers of the day

20:00 → 22:45 Workshop Dinner Barbecue

Thursday 9 July

11:00 → 12:00 0: Lunch at cafeteria optional (voucher provided)

12:00 → 14:20 8 Thu: 7 Thu

12:00 Quantum Reference Frames for Quantum Gravity: The Relational Gravitational Path Integral

Internal quantum reference frames provide a general framework for handling symmetries in quantum theory, with applications ranging from quantum gravity and gauge theories to quantum information and foundational physics. I will first introduce the formalism in simple mechanical systems, before turning to classical gravity. There, I will motivate the need for internal, dynamical frames in background-independent theories to define relationally local gauge-invariant observables, and show how this framework leads to a relational update of general covariance: frame covariance.

I will then move to non-perturbative quantum gravity, showing how quantum reference frames can be used to define a manifestly gauge-invariant relational path integral, which is also invariant under transformations between quantum reference frames. It therefore provides a perspective-neutral description of quantum gravitational physics. I will also discuss the associated relational effective actions. Although effective actions are, in general, not frame-covariant off shell, the on-shell physics they encode is.

Finally, I will present several physical consequences of this framework, including the fuzziness of frame-changed local correlators, the non-trivial interplay between quantum-reference-frame transformations and time evolution, and the frame-dependence properties of ground sectors and Hartle-Hawking prescriptions. I will conclude by outlining future directions, with particular emphasis on a relational notion of the renormalization group flow.

Speaker: Luca Marchetti (Okinawa Institute of Science and Technology)

12:40 Panel: Bridging Philosophy of Science and Quantum Foundations: Gemma De les Coves, Stephan Hartmann, Daniele Oriti Chair: Eugenio Bianchi

13:40 The Geometry of the Guiding Center: Vielbein Phase Space, Curvature Moment Maps, and the Spin-GMP Algebra

In the fractional quantum Hall effect, the topological quenching of kinetic energy elevates spatial geometry to the primary dynamical degree of freedom. We demonstrate that macroscopic charge dynamics can be rigorously formulated as a reduced classical phase space of two-dimensional unimodular vielbeins and the physical charge density is exactly identified with the scalar curvature of the vielbein's torsionless spin connection. Consequently, the Girvin-MacDonald-Platzman (GMP) algebra emerges kinematically as the equivariant moment-map algebra of area-preserving diffeomorphisms.

Extending this geometry to spinful fluids, we construct a commutative, Wess-Zumino-like action coupling two vielbein sheets to a local spin frame. This provides a direct physical intuition akin to frame-dragging: because the underlying spatial coordinates are intrinsically noncommutative, applying spatially varying spin rotations inevitably drags the orbital fluid labels. The spin-GMP algebra is shown to be hardwired into this geometry — emerging as frame-dragging on a spin-entangled spatial background.

Speaker: Yichen Hu (Florida Atlantic University)

14:20 → 14:50 Coffee break

14:50 → 16:50 8 Thu

14:50 Effective continuum physics from quantum gravity

The group field theory formalism provides a powerful embedding of canonical LQG states, spin foam amplitudes and lattice gravity path integrals, offering in particular suitable tools for the extraction of continuum, spatiotemporal physics. After reviewing the key aspects of this embedding, the challenges of bridging the gap between fundamental quantum gravity dynamics and effective continuum physics, and outlining the (novel) approximations that it allows, I discuss recent results showing how an effective scalar field theory, on a cosmological background, can be extracted from the fundamental quantum gravity dynamics. The tools used combine: mean field techniques from quantum many-body systems and relational observables constructed via quantum reference frames, in addition to the control over the quantum geometric aspects of the theory. I will also indicate the quantum gravity modifications to usual QFT that this effective field theory shows, of potential interest for quantum gravity phenomenology, and draw some more general lessons about the non-trivial relation between fundamental quantum gravity models and their emergent continuum physics.

Speaker: Daniele Oriti (Dept Fisica Teorica, Universidad Complutense de Madrid)

15:30 Coarse-graining & dynamics of elementary blocks in canonical LQG

In a first part, I will present a coarse-grained model for canonical LQG, with an overview of the construction of the kinematical structure and the effective dynamics. Then, in a second part, I will present an analysis of a simplified classical model, which consists of two vertices, representing the elementary block structure which emerges in the the coarse-grained model. This analysis provides the first basic template for the investigation of the effective dynamics on doubly complete graphs.

Speaker: Mehdi Assanioussi

16:10 Classical Overlap and Area-Type Scaling from Symplectic Reduction

Regularised field theories are usually described by assigning independent degrees of freedom to all modes below a UV cutoff. This gives a volume-scaling kinematical phase space. But for a given solution of the equations of motion, this count need not coincide with the number of independent canonical directions actually used by the dynamics.

I will present recent results on this question for a UV/IR-regulated classical scalar field. Using symplectic model order reduction, one can ask for the smallest Hamiltonian system that reproduces a field trajectory while preserving the symplectic structure. For the free theory, the answer is fixed by the number of distinct normal-mode frequencies. This gives area-type scaling in flat space and controlled curvature-dependent deviations on maximally symmetric backgrounds. Weak interactions smooth the sharp free-theory threshold, but numerical results suggest that the same scale persists over quasi-integrable time intervals.

The reduced phase space also changes the algebra of reconstructed field variables: many apparent modes are represented by fewer independent canonical variables, leading to induced overlap in their Poisson brackets. This provides a simple classical setting for separating apparent field-theoretic variables from dynamically independent degrees of freedom.

Speaker: Varun Kushwaha (Ludwig-Maximilians-Universität München)

16:50 → 17:20 Coffee break

17:20 → 19:20 9 Thu

17:20 Quantum effects on local observers in an exactly solvable model of quantum gravity

Recent developments in quantum gravity have emphasized the role of an "observer" in making sense of quasi-local quantum-gravitational effects. In this talk, we will describe an explicit model of a gravitationally dressed observer in Jackiw-Teitelboim (JT) gravity. This is a dilaton gravity model in two spacetime dimensions that is fully solvable both classically and quantum-mechanically, thereby allowing us to study quantum gravity effects far beyond the semiclassical regime. We will show how properly accounting for gravitational dressing in JT gravity affects the experience of a local probe crossing the horizon of a black hole, and also study nonperturbative effects on the thermal atmosphere outside the black hole in this model. In particular, we will see that quantum-gravitational effects can allow a particle detector to sense the location of a black hole horizon locally, unlike in semiclassical gravity, and also that nonperturbative effects lead to an explicitly finite entanglement entropy for matter fields in the exterior of a black hole.

Speaker: Bruno Torres (Ghent University)

18:00 A loop quantization of the marginally bound Lemaitre-Tolman-Bondi dust model

We present a loop quantization of the marginally bound Lemaitre-Tolman-Bondi (LTB) model, describing the gravitational collapse of pressureless dust in spherical symmetry. The full quantum LTB model is constructed as a collection of noninteracting shells, each governed by an individual single-shell loop quantum dynamics. We show that the single-shell evolution is non-singular and that wave packets initially peaked on a collapsing trajectory undergo a bounce at Planckian energy densities and subsequently follow an expanding classical trajectory, resolving the classical central curvature singularity. Specifically, we find that expectation values associated with sharply peaked wave packets closely follow their semiclassical counterparts throughout the evolution, except near the bounce, where quantum interference effects typically arise, limiting the validity of the effective theory.
Unlike the semiclassical theory, access to a fully quantum description may open the possibility of formulating quantum field theory on quantum spacetimes, with potential applications to Hawking radiation and black holes thermodynamics.

Speaker: Luca Cafaro (University of Warsaw)

18:40 Parametrization of the primordial power spectrum in Loop Quantum Cosmology (online)

In this talk, I examine the impact of the hybrid and dressed-metric quantization approaches in loop quantum cosmology (LQC) on the angular power spectrum of cosmological perturbations. We introduce a new parametrization of the primordial power spectrum which depends on the characteristics of the quantum bounce epoch. For a total cosmic expansion of about 140 e-folds, the model predicts a suppression of power at low multipoles, while maintaining excellent agreement with Planck Collaboration observations at high multipoles. These results provide a consistent framework to probe potential imprints of LQC in the cosmic microwave background and open the door to future studies based on detailed Bayesian analyses of cosmological data.

Speaker: Antonio Vicente-Becerril (IEM-CSIC (Madrid))

19:20 → 20:20 Final Discussion with all speakers of the day: Final discussion with all speakers of the day

20:20 → 20:40 Closing remarks