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PAFT26 - Quantum Frontiers in Gravity

→ Europe/Rome
Lloyd's Baia Hotel - Vietri Sul Mare (SA), Italy

Lloyd's Baia Hotel - Vietri Sul Mare (SA), Italy

Via Benedetto Croce, snc, 84019 Vietri sul mare SA, Italy
Description
The main objective of the conference "PAFT26 - Quantum Frontiers in Gravity" is to bring together theoretical physicists and phenomenologists who are experts in the complementary fields of classical and quantum gravity, modified gravity, and experimental aspects of gravity in quantum systems. The conference will give space to a constructive exchange of ideas and encourage new collaborations.
 
All conference participants will be accommodated at the Lloyd's Baia Hotel (see Accommodation for details). The conference fee is 120 euros. Students can apply for a fee waiver during registration. 

A conference dinner is included in the social program at a cost of 70 euros, to be paid at the venue.

Important Dates

The conference starts on Sunday, March 29, at 2pm (after lunch) and it ends on Wednesday, April 1st, at 1pm (before lunch).

Deadline for Talk submission on February 28
Confirmation of acceptance will be given on March 4
 
Deadline for registration on March 13
 
Deadline for reservation at Lloyd'sBaia on March 7
 
Communication about fee waiver on March 4

Invited Speakers

A preliminary list of invited speakers includes:
 
G. Barnich (ULB), L.-Q. Chen (IQOQI), C. Curceanu (INFN), L. Diosi (Budapest, RMKI), J. Kowalski-Glikman (NCBJ & UWr), R. Loll (Nijmegen U & IMAPP), N. Mavromatos (Natl. Tech. U. Athens and King's Coll. London), A. Pachol (USN), T. Sotiriou (U Nottingham)

Organising Committee

Michele Arzano (Napoli Federico II & INFN Napoli), Massimo Blasone (Salerno & INFN Napoli/Salerno), Goffredo Chirco (Napoli Federico II & INFN Napoli), Gaetano Fiore (Napoli Federico II & INFN. Napoli), Giulia Gubitosi (Napoli Federico II & INFN Napoli), Gaetano Lambiase (Salerno & INFN Napoli/Salerno), Fedele Lizzi (Napoli Federico II & INFN Napoli), Tanmay Kumar Poddar (IPPP, Durham), Luca Visinelli  (Salerno & INFN Napoli/Salerno), Patrizia Vitale (Napoli Federico II & INFN Napoli)
 
PAFT_2026_reservation_form.pdf
RegistrantsBook.pdf
Participants
81 View full list
  • Sunday 29 March
  • Monday 30 March
    • Monday sessions

      (morning)

      • 8
        Lajos Diósi

        Title: A healthier stochastic semiclassical gravity: world without Schrödinger cats

        Abstract: Semiclassical gravity couples classical gravity to the quantized matter in the mean-field approximation, which is problematic for two reasons. It ignores the quantum fluctuation of matter distribution, and it violates the linearity of the quantum dynamics. The first problem can be mitigated by allowing stochastic fluctuations of the geometry, but the second problem lies deep in quantum foundations. Restoration of quantum linearity requires a conceptual approach to
        hybrid classical-quantum coupling. Studies of the measurement problem and the quantum-classical transition point to a solution. It is based on a postulated mechanism of spontaneous quantum monitoring plus feedback. This approach eliminates Schrödinger cat states, takes quantum fluctuations into account, and restores the linearity of quantum dynamics. Such conceptually ’healthier’ semiclassical theory exists in the Newtonian limit, but its relativistic extension hits a wall. The long-known obstacles lie in quantum foundations.

        vietri2026.pdf
      • 9
        Lin-Qing Chen

        Title: Quantum coordinate transformations via matter fields for quantum spacetime

        Abstract: A central challenge in quantum gravity is to formulate a theory without presupposing a background spacetime. Such a description requires relational observables and a genuinely quantum generalisation of diffeomorphisms. Here we associate coordinate systems with sets of four dynamical scalar fields, whose stress-energy tensors contribute to the constraints of linearised quantum gravity.
        Such quantum coordinate fields (QCFs) extend the notion of quantum reference frames and enable a relational description of other physical systems. By generalizing the perspective-neutral construction of quantum reference frames, we show that relational, gauge invariant observables admit a description in each QCF perspective, and derive consistent transformations between perspectives. The resulting unitary maps implement passive or active, local quantum coordinate changes, yielding quantum linearized diffeomorphisms beyond superpositions of classical ones. We further discuss the operational aspects of relational observables, the conceptual distinction between QCFs and quantum reference frames, and identify the difference between QCFs transformations and the superposition of classical diffeomorphisms.

        Vietri 2026_LQC.pdf
      • 10:40
        coffee break
      • 10
        Giacomo Rosati

        Title: Deformed CPT Symmetry from Curved Momentum Space

        Abstract: The asymmetry of curved momentum space in κ-deformed field theories sheds new light on the fate of CPT symmetry in deformed relativistic frameworks based on Hopf algebras. Based on our recent work (Phys. Rev. D 113 (2026) 2), we show that charge conjugation is incompatible with κ-Poincaré invariance, while the geometric structure of momentum space naturally suggests a deformation of time-reversal symmetry leading to a deformed realization of CPT invariance. These results clarify the role of discrete symmetries in quantum-gravity–inspired models based on Hopf-algebra deformations and may provide a useful framework for exploring phenomenological implications related to tests of discrete symmetries.

        RosatiVietri2026slides.pdf
      • 11
        Vittorio D'Esposito

        Title: Doubly Quantum Mechanics

        Abstract: Motivated by the expectation that relativistic symmetries might acquire quantum features in Quantum Gravity, we take the first steps towards a theory of “Doubly” Quantum Mechanics, a modification of Quantum Mechanics in which the geometrical configurations of physical systems, measurement apparatuses, and reference frame transformations are themselves quantized and described by “geometry” states in a Hilbert space. We develop the formalism for spin-1/2 measurements by promoting the group of spatial rotations SU(2) to the quantum group SUq(2) and generalizing the axioms of Quantum Theory in a covariant way.
        As a consequence of our axioms, probabilities become indefinite: the probability of obtaining a given result in a spin measurement is promoted to a self-adjoint positive definite operator acting on the Hilbert space of geometry states, hence acquiring novel non-classical features. After introducing a suitable class of semi-classical geometry states, which describe near-to-classical geometrical configurations of physical systems, we find that probability measurements are affected, in these configurations, by intrinsic uncertainties stemming from the quantum properties of SUq(2). This feature translates into an unavoidable fuzziness for observers attempting to align their reference frames by exchanging spin-1/2 particles, even when the number of exchanged spins approaches infinity, contrary to the standard SU(2) case.

        Vittorio_D_Esposito_PAFT26.pdf
      • 12
        Samuel Fedida

        Title: A nonlinear gravitisation of quantum field theory?

        Abstract: We develop a relativistically causal generally covariant gravitisation of quantum field theory. The resulting model is similar to Møller-Rosenfeld semiclassical gravity: the classical gravitational field is sourced by the expectation value of the quantum stress-energy tensor, though now taken with respect to the local quantum state at each point of spacetime. We derive the weak-field limit which exhibits the explicitly causal dynamical structure of the theory, and recover the Schrödinger-Newton system in the nonrelativistic limit. This model can thus be understood as a causal completion of the Schrödinger-Newton equation. We then explore relativistic quantum measurements in this nonlinear setup, showing that these need not lead to superluminal signalling should quantum states update in the future light-cone of the measurement region. This aligns with detector-based quantum measurements in quantum field theory. We show that the discontinuities in the expectation value of the stress-energy tensor caused by quantum measurements need not violate the distributional gravitational field equations. We also highlight that the theory presents non-standard measurements -- namely readout devices -- from its nonlinearities, which allows one to approximately determine a quantum state without affecting it through the state's influence on the
        classical gravitational field. This allows for quantum state cloning, though in a way consistent with no-superluminal signaling. If time permits, we will discuss the black-hole information paradox within this model, and explore some routes towards the falsifiability of the theory.

        Presentation.pdf
      • 13
        Alexander Kamenshchik

        Title: Is the many-worlds interpretation of quantum theory counter-intuitive?

        Abstract: The many-worlds (Everett) interpretation of quantum mechanics is very well adapted for the application to cosmology because it does not require the existence of an external observer. At the same time it is often considered as being a "counter-intuitive". Analyzing the problem of the choice of the preferred basis, I argue that this interpretation is less counter-intuitive and bizarre than many researchers think.

        Kamenshchik-talk.pdf
      • 12:50
        Lunch break
      • 14
        Catalina Oana Curceanu

        Title: Testing Quantum Mechanics Underground: Collapse models and Pauli
        Exclusion Principle

        Abstract: We are experimentally investigating possible departures from the standard quantum mechanics’ predictions at the Gran Sasso underground
        laboratory in Italy. In particular, with radiation detectors we are searching for signals predicted by the collapse models (spontaneous emission of radiation) which were proposed to solve the “measurement problem” in quantum physics and signals coming from a possible violation of the Pauli Exclusion Principle. I shall present our recent results and future plans for gravity-related collapse studies and also more generic results on testing CSL (Continuous Spontaneous Localization) collapse models and discuss future perspectives. I shall as well present the VIP experiment with which we look for possible violations of the Pauli Exclusion Principle by searching for “impossible” atomic transitions and the impact of this research in relation to Quantum Gravity models.

      • 15
        Domenico Frattulillo

        Title: Planckian bound on IR/UV mixing from cold-atom interferometry

        Abstract: IR/UV mixing (a mechanism causing ultraviolet quantum-gravity effects to manifest themselves also in a far-infrared regime) is a rare case of feature found in several approaches to the quantumgravity problem. We here derive the implications for ”soft” IR/UV mixing (corrections to the dispersion relation that are linear in momentum) of some recent cold-atom-interferometry measurements. For both signs of the IR/UV-mixing correction term we establish bounds on the characteristic length scale which reach the Planck-length milestone. Intriguingly, for values of the characteristic scale of about half the Planck length we find that IR/UV mixing provides a solution for a puzzling discrepancy between Cesium-based and Rubidium-based atom-interferometric measurements of the fine structure constant.

        vietri_slides_Frattulillo.pdf
      • 16
        Emanuele Panella

        Title: Stochastic gravitational waves in classical gravity

        Abstract: The quest for a quantum description of gravity has been long, diverse, and productive. Yet, despite decades of theoretical progress, there is still no direct experimental evidence for the quantum nature of spacetime. In this talk, I explore an alternative, indirect route to probing quantum gravity by assuming the fundamental classicality of the gravitational field and examining the resulting observational conflicts. In particular, I will discuss a key consistency condition—known as the decoherence–diffusion trade-off—that any theory of fundamentally classical gravity coupled to quantum matter must satisfy. By analysing a toy model of a linearised classical–quantum (CQ) gravity–matter system, I will explicitly show how this trade-off implies unavoidable, measurable
        effects, such as a fundamental stochastic gravitational-wave background, which cannot be eliminated by fine-tuning the model parameters.

        PAFT26.pdf
      • 17
        Hou Yau

        Title: Excitations of Spacetime in a Quantized Field

        Abstract: We investigate the possibility of a Proper Time Oscillator—the temporal analog of the quantum harmonic oscillator. Such an oscillator exhibits the same properties consistent with those of a particle in both quantum theory and general relativity. First, we find that spacetime can be quantized at a distance scale much larger than Planck. The quanta of this spacetime excitation field are proper-time oscillators. The field is characterized as bosonic, and each proper time oscillator possesses the properties of a boson. We further extends our results for a fermionic
        field. Next, we examine the spacetime geometry outside a stationary proper time oscillator, treating it as a classical object (i.e., neglecting quantum effects). The resulting geometry is Schwarzschild, corresponding to a rest mass in general relativity. Together, these results indicate that a particle's intrinsic proper-time oscillation provides the means for direct spacetime interaction and the generation
        of a gravitational field, assuming the particle is an excitation of its quantum field and the underlying spacetime. We also explore how such oscillations might affect neutrino arrival-time measurements. Our analysis indicates that spatial oscillations of a 1-TeV neutrino may not be entirely beyond observational reach in a laboratory, offering a potential signature of time-based fluctuations. References [1] Yau, H. Y.: Quantized field with excitations of spacetime. Sci Rep 15, 30844 (2025) [2] Yau, H. Y.: Matter, spacetime and proper time oscillator. To appear in (2024) Marcel Grossman Conference Proceeding [3] Yau, H. Y.: Proper time operator and its uncertainty relation. J. Phys, Commun. 105001 (2021) [4] Yau, H. Y.: Schwarzschild field of a proper time oscillator. Symmetry 12(2), 312 (2020) [5] Yau, H. Y.: Self-adjoint time operator in a quantum field. J. Quant. Info. 1941016 (2020).

        presentation (PAFT26).pdf
      • 16:25
        coffee break
      • 18
        Alfonso Lamberti

        Title: Gravity model from (A)dS Yang-Mills theory

        Abstract: We investigate the relationship between a one-parameter family of (anti-)de Sitter Yang-Mills models and a model of Einstein-Palatini gravity with matter, realized through Inönu-Wigner contraction of the (A)dS algebra. By setting the group parameter to zero, the gauge transformation of the potential becomes consistent with the transformation properties of the tetrad form and spin connection. We show that a sector of the Yang-Mills dynamics exists in which the equations decouple. Moreover, a subset of the gauge transformations can be related to diffeomorphisms, leading to the identification of the tetrad field. Finally, the resulting dynamics is consistent with a gravitational dynamics in the first-order formalism.

        Lavoro 300326 Lamberti Alfonso.pdf
      • 19
        Riccardo Falcone

        Title: An inequality for relativistic local quantum measurements

        Abstract: We investigate the trade-off between vacuum insensitivity and sensitivity to excitations in finite-size detectors, taking measurement locality as a fundamental constraint. We derive an upper bound on the detectability of vacuum excitation, given a small but nonzero probability of false positives in the vacuum state. The result is independent of the specific details of the measurement or the underlying physical mechanisms of the detector and relies only on the assumption of locality. Experimental confirmation or violation of the inequality would provide a test of the axioms of algebraic quantum field theory, offer new insights into the measurement problem in relativistic quantum physics, and establish a fundamental technological limit in local particle detection.

        Talk.pdf
      • 20
        Ali Akil

        Title: Black Hole Information From Non-vacuum Localised Quantum States

        Abstract: We revisit Hawking's black hole radiation derivation, including the quantum state of the initial matter forming the black hole. We investigate how non-vacuum initial quantum states, at the past of a black hole geometry, influence the black hole radiation observed at future null infinity. We further classify which of the initial state excitations are distinguishable from one another through measurements on the black hole radiation state. We use Algebraic Quantum Field Theory (AQFT) to provide a clear physical interpretation of the results, in terms of localized operations. We then take a concrete example of a black hole made of one large collapsing excitation of mass M and compare it to a same-mass black hole formed due to the collapse of two smaller excitations, of mass M/2 each. We find using our formalism that the two cases yield different radiation states and can in principle be distinguished. Our results provide a mechanism for partial information recovery in evaporating black holes, classify what information is recoverable through stimulated emission, and a concrete understanding of the classification based on the AQFT localisation.

        Stimulated Emission Vietri2.pdf
    • Conference Dinner
  • Tuesday 31 March
  • Wednesday 1 April