Quantum Gravity and Cosmology 2026

9 Feb 2026, 08:30 → 13 Feb 2026, 18:55 Europe/Rome

Sala Ulisse (Bologna)

General Relativity (GR) perfectly describes a variety of phenomena in gravity at energy scales much less than the Planck mass. However, this theory calls for an ultraviolet (UV) completion at higher energies. 

Various approaches have been developed in this direction in the past decades, including (but not limited to) string theory, which naturally contains the limit of GR. The low-energy effective field theory (EFT) of GR can also have a UV completion which is formulated as a field theory, perturbatively including higher curvature operators or non- perturbatively with an asymptotically safe fixed point. Formulation of new methods, especially working for gravity in the non-perturbative regime, requires more exchanges between the scientific communities that used to be separated. We believe that cross-team discussions will lead to significant progress in understanding the self-consistency and potential phenomenological implications of UV complete descriptions of gravity.

The goal of the workshop is to bring together the experts working on different UV complete approaches to quantum gravity, from string theory to various perturbative and non-perturbative approaches. Given the promising opportunity to probe quantum gravity effects in the very early Universe with future CMB and gravitational wave experiments, we expect the in-depth discussions on predictions and self-consistency of low- energy effective theories on top of cosmological backgrounds.

The meeting will be mainly focused on the following directions:

• Non-perturbative methods, in application to quantum gravity, such as string theory, amplitudes bootstrap, functional renormalisation group, loop quantum gravity, etc.
• Quantum gravity effects in the early Universe: inflation, cosmological correlators, non-gaussianities, gravitational waves.
• EFT of gravity in connection with cosmology and Black Holes.
  other related topics.

 

Preliminary list of speakers

Manuel Asorey (Zaragoza U.)

Andrei Barvinsky (Lebedev Inst.)

Robert Brandenberger (McGill U.)

Mariana Carrillo González (Imperial Coll., London)

Calvin Y.R. Chen (Taiwan, Natl. Taiwan U.)

Niccolo Cribiori (KULeuven)

Gia Dvali (Max Planck Inst. and Munich U., ASC)

Kelian Haring (Amsterdam U.)

Song He (Ningbo University)

Denis Karateev (UNIGE)

Shun-Pei Miao (Taiwan, Natl. Cheng Kung U.)

Viatcheslav F. Mukhanov (Munich U. and Korea Inst. Advanced Study, Seoul)

Alessandro Podo (IHES, Bures-sur-Yvette)

Sébastien Renaux-Petel (Paris, Inst. Astrophys.)

Francesco Riva (Geneva U.)

Diederik Roest (Groningen U.)

Alberto Salvio (Rome U., Tor Vergata)

Fabio Scardigli (Politecnico di Milano)

Richard Woodard (Florida U.)

Zhong-Zhi Xianyu (Tsinghua U., Beijing)

Masahide Yamaguchi (Tokyo Inst. Tech.)

 

Organizing Committee

• Fiorenzo Bastianelli (UniBO)
• Luca Buoninfante (IGFAE, Santiago de Compostela U.)
• Roberto Casadio (UniBO)
• Andrea Giusti (UniBO)
• Alexander Kamenschchik (UniBO)
• Alexey Koshelev (ShanghaiTech U. and Beira Interior U.)
• Alessandro Pesci (INFN)
• Anna Tokareva (HIAS, UCAS, Hangzhou)
• Alessandro Tronconi (INFN)

 

 

This meeting is a regular yearly conference organized since 2021. It used to be jointly co-organized in different years by Imperial College London, NORDITA, Tokyo Institute of Technology, University of Portsmouth, ShanghaiTech University, Universidade da Beira Interior, and other institutions.

"Due to strict limitations in venue capacity and funding availability, the number of conference participants is limited. The organizers reserve the right to confirm registration requests.”

 

REGISTRATION WILL CLOSE ON DECEMBER 26th

Monday 9 February

08:30 → 09:25 Registration and Welcome

Welcome.pdf

09:25 → 10:15 Karateev Denis - Trace anomalies and the dilation-graviton amplitude

We consider four-dimensional quantum field theories (QFTs) coupled to the background dilaton and graviton fields. The IR effective action of these background fields is fixed by trace anomalies. Using this effective action we compute the dilaton-graviton scattering amplitude. We show that it receives a universal helicity-flipping contribution proportional to (∆c − ∆a) along any RG flow, where ∆c and ∆a are the differences of the UV and IR c- and a-trace anomalies respectively. This allows us to relate (∆c − ∆a) to spinning massive states in the spectrum of the QFT. We test our predictions in simple examples. We discuss possible applications.

karateev.pdf

10:15 → 11:05 Renaux-Petel Sébastien - de Sitter momentum space

Renaux-Petel-KLF.pdf

11:05 → 11:35 Coffee Break

11:35 → 12:25 Chen Calvin Y.R. - Extremal black holes and UV Physics

chen_cyr_slides.pdf

12:25 → 12:50 Shao LongQi - Running EFT-hedron with null constraints at loop level

Running EFT hedron.pdf

12:50 → 14:20 Lunch

14:20 → 15:10 Haring Kelian - Scattering on the Coulomb Branch of N=4 SYM

KelianHaring_N4.pdf

15:10 → 15:35 Sauro Dario - Heat kernel of second-order non-minimal operators

The spectra of general non-minimal second-order operators are analyzed using the heat kernel method. In particular, we derive the local part of the trace of the second Seeley-DeWitt heat kernel coefficient for such operators in a completely model-independent way. We provide three examples to show how our result can be applied in practical scenarios, emphasizing on the phenomenological implications for higher-spin fields.

Bologna 2026.pdf

15:35 → 16:05 Coffee Break

16:05 → 16:55 Riva Francesco - TBA

Bologna.pdf

16:55 → 17:20 Parente Luca - Momentum running in higher-derivative gravity

Recent works have argued that improved one-loop beta functions, which incorporate the physical momentum dependence of one-loop–corrected higher-derivative gravity theories, provide the most suitable description of their high-energy behaviour. We critically examined the validity of this claim. We have computed the explicit gauge dependence of the one-loop momentum running of curvature-squared operators in both quadratic gravity and conformal gravity. We have found that this momentum running is gauge-dependent. We then discuss the implications of this result for the consistency of the approach and for the physical predictivity of these theories.

QGC26-Luca Parente-2.pdf

Tuesday 10 February

09:25 → 10:15 Xianyu Zhong-Zhi - Analytical Techniques for Massive Cosmological Correlators

I will introduce several recent developments in analytical studies of cosmological correlators with massive exchanges, with an emphasis on the canonical objects called family trees. These family trees are well-defined hypergeometric functions to which an arbitrary massive tree graph can be reduced. I will discuss their analytical structures, differential equations, as well as generalizations to various degenerate kinematics including folded trees and loop integrands, which are important for phenomenological applications in cosmological collider physics.

10:15 → 11:05 Yamaguchi Masahide - Symmetry of Bounce Solutions at Finite Temperature

Cosmological phase transitions, especially first order phase transitions, have attracted renewed interest as potential sources of gravitational waves. Accurately predicting the resulting gravitational wave signal requires a reliable estimate of the transition rate, which is governed by a saddle-point configuration known as the bounce solution. The seminal work of Coleman, Glaser, and Martin established that at zero temperature, any nontrivial bounce solution to the equations of motion that minimizes the Euclidean action is O(D)-symmetric in D-dimensional spacetime. At finite temperature, however, it has not been proven that an O(D-1)-symmetric bounce solution in the spatial directions indeed yields the minimal Euclidean action, despite this assumption being widely used in the literature. In this talk, we extend the Coleman–Glaser–Martin analysis to finite temperature. We rigorously prove that for a broad class of scalar potentials, any saddle-point configuration with the least action is necessarily O(D-1)-symmetric and monotonic in the spatial directions. This result provides a firm mathematical foundation for the symmetry properties widely assumed in studies of thermal vacuum decay and cosmological phase transitions.

QGC26_yamaguchi.pdf

11:05 → 11:35 Coffee Break

11:35 → 12:25 He Song - Geometric realization of stress-tensor deformed field theory

Emergent-Gravity.pdf

12:25 → 12:50 Trugenberger Carlo - Networks as the fundamental constituents of the universe

I will present a model in which both gravity and quantum mechanics emerge as macroscopic statistical effects reflecting the free energy minimization of fundamental binary degrees of freedom. The model is defined by an ultraviolet continuous fixed point of a statistical model on random networks, governed by the combinatorial Ollivier-Ricci curvature, which acts as a network analogue of the Einstein-Hilbert action. The model exhibits two distinct phases separated by this fixed point, a geometric and a random phase, representing space and mat- ter, respectively. At weak coupling and on large scales, the network organizes into a holographic surface whose collective state encodes both an emergent 3D space and the matter distributed in it. The Einstein equations emerge as constitutive relations expressing matter in terms of fundamental network degrees of freedom while dynamics in a comoving frame is governed by relativistic quantum mechanics. Quantum mechanics, however is an effective theory breaking down at the scale of the radius of curvature of the holographic network. On smaller scales, not only relativistic invariance is lost but also the Lorentzian signature of space-time. Finally, the man- ifold nature of space-time breaks down on the Planck length, where the random character of the fundamental network on the smallest scales becomes apparent. The network model seems to naturally encode several of the large-distance features of cosmology, albeit still at a qualitative level. The holographic property of black holes arises intrinsically from the expander nature of random regular graphs. There is a natural mechanism to resolve the cosmological constant problem and dark matter appears naturally as a metastable allotrope in the network fabric of space-time.

QG_Bologna.pdf

12:50 → 14:20 Lunch

14:20 → 15:10 Roest Diederik - Exceptional scalar field theories

exceptional-scalars-Bologna.pdf

15:10 → 15:35 Glavan Dražen - Gauge independent logarithms from inflationary gravitons

In flat space the S-matrix is a gauge-independent observable in perturbative quantum gravity. The gauge-independence owes to the source and observer corrections that need to be included. I will discuss the generalization of this procedure to de Sitter space, without taking the asymptotic limits of the S-matrix, and recent work demonstrating gauge-independence of the construction. This is a step towards constructing renormalized one-loop quantum-gravitational observables in de Sitter.

Glavan_Bologna.pdf

15:35 → 16:05 Coffee Break

16:05 → 16:30 Fahn Max Joseph - Gravitationally induced decoherence models comparing different descriptions of quantum gravity

In this talk, two gravitationally induced decoherence models are analysed that compare different formulations of quantum gravity. The first model discusses decoherence induced by horizons with classical and quantum geometries. In a recent series of papers following arXiv:2205.06279, it was shown that classical horizons constantly induce decoherence on spatial quantum superpositions, which increases linearly with the time during which the superposition is kept open. In this talk, possible effects of black hole quantisation are discussed, the latter being effectively described in terms of a quantisation of the area of its horizon with a minimal value for area variations, i.e., a quantum of the horizon area $\Delta A$, which induces a low frequency cutoff on the modes that can enter the horizon. Focusing on a charged particle and the electromagnetic field accompanying it, it is shown that the quantisation of the horizon can be expected to affect the decoherence of the spatial superposition. More specifically, the resulting decoherence exhibits a constant saturation value, the magnitude of which depends on the assumed value of the quantum of area, and turns out to be quite small for $\Delta A$ of the order of the Planck length squared. In the second part of the talk, a quantum-mechanical toy model describing a neutrino propagating in flat space through an environment of gravitational waves is analysed. The interaction term is motivated by the way in which Fock-quantised linearised gravity couples to matter fields. Within this framework, gravity induces a decoherence effect that damps neutrino oscillations, providing insight into the physical properties of the model. In a subsequent step, the coupling is modified in a Loop Quantum Gravity–inspired manner to mimic certain features of a loop quantisation, leading to a modified decoherence rate compared to the Fock-quantisation–inspired model.

QGC26_Talk_Fahn.pdf

16:30 → 16:55 Culetu Hristu - Vacuum energy and strong gravity with running gravitational constant

Astatic geometry with applications ni microphysics is studied in this paper. The source of curvature is given by an anisotropic stress tensor. The null and timelike
radial geodesics are investigated and found to represent hyperbolae, but with different accelerations. Due to the very high acceleration, close to the maximum one ($a \approx 10^{34}cm/s^{2}$) [1], a massless particle reach very quickly the velocity $c$. That si related to the Zeldovich vacuum energy density [2] $\epsilon$
which, using the strong gravitational constant $G_{s} = c\hbar/m_{p}^{2}$ instead
of Newton's constant $G_(N}$, appears as Slepsilon_{vac} = m_ip?^{4)0^453/hbar^{3}, i.e. proportional to Sm_ip,^{435, where Sm_Ip}S si the proton mass. Asimilar dependence has recently been obtained by LeClair [3).
Some numerical examples are given, emphasizing the strong curvatures near $r =1/a$. The energy-momentum tensor creating the curvatures corresponds to a massless scalar field with negative kinetic energy (antiscalar field) [4,5].

Bologna2026.culetu.slides.pdf

16:55 → 17:20 Gionti SJ Gabriele - Quantum Measure in Regge Calculus

D’Adda has shown that by assigning a length to each link and coordinates to each labelled vertex, one can define a non-Euclidean flat metric and a reference frame within each simplex that is invariant under GL(n,R). In this formulation, the metric tensor is a function of both the link lengths and the vertex coordinates. In this talk, we show that by performing an appropriate gauge fixing of the metric tensor, it is possible to compute explicitly the Faddeev–Popov determinant entering the quantum measure of Regge calculus. The determination of this measure has been a longstanding open problem, and our results represent a step toward its resolution. A well-defined quantum measure has important implications for numerical investigations of quantum gravity. In particular, our approach may lead to improved simulations in Quantum Regge Calculus and could also have consequences for Dynamical Triangulations and, potentially, for Causal Dynamical Triangulations.

GIONTI_Quantum_Gravity_and_Cosmology_2026.pdf

Wednesday 11 February

09:25 → 10:15 Woodard Richard - A Nonlocal Realization of MOND that Interpolates from Cosmology to Gravitationally Bound Systems

This talk is based on arXiv:2512.10513 with Cedric Deffayet.
Nonlocal modifications of gravity derive from corrections to the quantum
gravitational stress tensor which grow nonperturbatively strong during
primordial inflation and may persist to the current epoch. Phenomenological
constructions have been given that realize MOND in gravitationally bound
systems and, separately, reproduce all the cosmological phenomena usually
ascribed to dark matter, including the cosmic microwave background radiation,
baryon acoustic oscillations and linearized structure formation. In this work
we exhibit a single model that interpolates between the two regimes.

Bologna.pdf

10:15 → 11:05 Miao Shun-Pei - Quantum cosmology in accelerating spacetimes

We simplify the gravitational equations that apply in accelerating spacetimes and are consistent with the cosmological principle. Solutions to these equations should be tantamount to all order resummations of the perturbative leading logarithms. We discuss the “null hypothesis” and study the observable local expansion rate.

QCinAcceleratingSpacetimes.pdf

11:05 → 11:35 Coffee Break

11:35 → 12:25 Brandenberger Robert - Emergent Spacetime and Early Universe Cosmology from the BFSS Matrix Model

I will discuss a proposal to obtain an emergent spacetime
and early universe cosmology starting from a thermal state of the
BFSS matrix model. The emergent space has three infinite classical
dimensions. Like in String Gas Cosmology, thermal fluctuations in
the initial state lead to a spectrum of density fluctuations which
is consistent with observations, and predicts a roughly scale-invariant
spectrum of gravitational waves with a slight blue tilt.

Bologna-26.pdf

12:25 → 12:50 Naskar Abhishek - Prospects of Non-Local Field Theories in Early Universe Cosmology

Non-local field theoretic frameworks can provide ghost free renormalizable description of gravity. Recently it is shown that a non-local extension of Starobinsky gravity can consistently realize inflation and have interesting observational features in the three point functions of scalar perturbations. In this talk we will describe inflation with a scalar field having non-local kinetic term and discuss the observational consequences of non-locality. Specifically we will highlight the modifications in three point functions of scalar perturbations. Additionally, we will present a bouncing scenario from a non-local gravitational setup and discuss its observational consequences.

Abhishek_Naskar.pdf

12:50 → 14:20 Lunch

14:20 → 15:10 Asorey Manuel - Reflection positivity in a higher-derivative model with physical bound states of ghosts

The inclusion of higher derivatives is a necessary condition for a renormalizableor superrenormalizable local theory of quantum gravity. On the other hand, higher derivatives lead to classical instabilities and a loss of unitarity at the quantum level. A standard way to detect such issues is by examining the reflection positivity condition and the existence of a Kallen--Lehmann spectral representation for the two-point function. We show that these requirements for a consistent The inclusion of higher derivatives is a necessary condition for a bulding a superrenormalizable local theory of quantum gravity. On the other hand, higher derivatives lead to classical instabilities and a loss of unitarity at the quantum level. A standard way to detect such issues is by examining the reflection positivity condition and the existence of a Kallen--Lehmann spectral representation for the two-point function. We show that these requirements of a consistent quantum theory are satisfied in a high derivative theory recently proposed. This theory is based on a six-derivative scalar field action featuring a pair of ghost fields with complex conjugated masses that form a bound state. These results support the interpretation that physical observables can emerge from ghost dynamics in a consistent and unitary framework.

Bologna-asorey-2026.pdf

15:10 → 15:35 Moschella Ugo - Plane waves and two-point functions in AdS QFT

I present some recent developments in AdS QFT:
two new formulae for two-point functions and their application
to compute Feynman diagrams in the real AdS manifold

Moschella - bologna QG.pptx

15:35 → 16:05 Coffee Break

16:05 → 16:55 Salvio Alberto - Infrared and Ultraviolet Properties of Quadratic Gravity

I will discuss infrared enhancements that are present in four-derivative theories in four dimensions (and presumably also in two-derivative theories in two dimensions). I will illustrate these effects using the example of quadratic gravity. Both the tree-level and one-loop approximations will be discussed. I will point out that these enhancements cannot be captured by running couplings. I will then also discuss running couplings that arise from genuine ultraviolet divergences.

Salvio-Quantum-Gravity-and-Cosmology-2026 2.pdf

16:55 → 17:20 Paci Gregorio - Auxiliary-Field Formalism for Higher-Derivatives Boundary CFTs

bologna_2026.pdf

20:00 → 23:00 Social Dinner - Cantina Bentivoglio, Via Mascarella, 4/b, Bologna

Thursday 12 February

09:25 → 10:15 Dvali Gia - TBA

10:15 → 11:05 Podo Alessandro - Naturalness of vanishing black-hole tides

tides.pdf

11:05 → 11:35 Coffee Break

11:35 → 12:00 Di Russo Giorgio - EFT corrected black holes through quantum Seiberg–Witten theory

The quantum Seiberg–Witten (SW) curve approach to the black hole (BH) perturbation theory problem provides a solid framework for obtaining analytical results. The Coulomb branch moduli space of the SW theory is topologically a torus and is therefore characterized by two cycles. In the quantum theory, these cycles enter the exact Born–Sommerfeld like quantization condition for quasi-normal modes (QNMs). After a brief theoretical overview of the N=2 SU(2) SYM theory, I will show how to apply this framework to compute the QNMs of Reissner–Nordström BHs with effective-field-theory corrections. The main result is that the causality requirement of the gravitational theory, formulated at the level of QNMs, translates into the same constraint on EFT couplings that appears in the Weak Gravity Conjecture. Furthermore, using a geodesic analogy, I will discuss certain resummation properties of the SW cycles in the Post-Minkowskian regime.

GDR presentation.pdf

12:00 → 12:25 Zantedeschi Michael - Evaporating black holes: how the burden of their memory stabilizes them

The memory burden effect describes how an object's stored information resists its own decay. This mechanism is especially pronounced in saturons—systems that saturate unitarity bounds on entropy—with black holes providing the prime example. I will show how memory burden can halt Hawking evaporation and dynamically stabilize black holes against complete decay. Crucially, this phenomenon is not exclusive to gravity: it arises naturally in generic quantum many-body systems and renormalizable field theories, underscoring its broader theoretical relevance. I will then discuss the phenomenological consequences, focusing on potential signatures in the early Universe and today. In particular, memory-stabilized black holes can produce distinctive high-energy cosmic-ray signals and leave characteristic imprints on the CMB, offering correlated cosmological and astrophysical probes of this peculiar form of dark matter.

Zantedeschi_Bologna.pdf

12:25 → 12:50 Rinaldi Massimiliano - Black hole event horizons are cosmologically coupled

We shown that an exactly static and spherically symmetric black hole event horizon cannot be embedded in a time-dependent geometry. Forcing it to do so results in a naked null singularity arising at the would-be horizon location. Therefore, black holes are expected to couple to the cosmological expansion and show a growth of their mass, which is unrelated to usual accretion mechanisms. We briefly also discuss possible observational signatures to test this result.

rinaldi.pdf

12:50 → 14:20 Lunch

14:20 → 15:10 Mukhanov Viatcheslav F. - Thick wall instantons

InstantoQC - 20260209_185617.pdf

15:10 → 15:35 Ferrarin Francesco - Impact of quantum gravity on the UV sensitivity of extremal black holes

Bologna_Impact of quantum gravity on the UV sensitivity of extremal black holes.pdf

15:35 → 16:00 Coffee Break

16:00 → 16:50 Scardigli Fabio - Bekenstein Bound and Generalized Entropies

We review the Bekenstein bound for thermodynamic entropy, and its dervation from arguments of black hole physics. Then we consider different generalized entropies as Tsallis-Cirto, Barrow, Tsallis-Jensen, and Renyi entropies. Thus, we establish new quantitative bounds on such entropies, arriving in this way to new formulations of the Bekenstein bound itself. We also briefly comment on the connections between the Bekenstein bound and the (generalized) uncertainty principle.

Bekenstein Bound & Gen Entropies_QGC2026-Bologna_(12-2-26).pdf

16:50 → 17:15 Antonelli Tommaso - Higher order differentiability of static and spherically symmetric geometries

I will present a result about the classification of singularities in static and spherically symmetric spacetimes. The theorem will allow us to conclude from fairly simple mathematical conditions the presence or absence of singular behaviour in some popular black hole solutions. These results are very general and stem from considerations of differential geometry, without resorting to any particular model of gravitational theory.

Presentation_Bologna-1.pdf

Friday 13 February

09:25 → 10:15 Barvinsky Andrei - TBA

TalkQGC-26(Bologna).pdf

10:15 → 11:05 Carrillo González Mariana - Graviton Correlators in (A)dS from Twistor Space

AdSTwistors_Correl.pptx

11:05 → 11:35 Coffee Break

11:35 → 12:25 Cribiori Niccolo - Bounds on cosmology from UV/IR Mixing

A central lesson of the swampland program in quantum gravity is that ultraviolet and infrared regimes may be intertwined in subtle and nontrivial ways. This UV/IR mixing can have significant implications for low-energy gravitational effective field theories. Building on recent bounds that explicitly realize such mixing, I will derive new constraints on inflationary models, and also establish a relation between the number of extra spacetime dimensions and the tensor-to-scalar ratio. The implications of these bounds will be discussed.

NC_bologna26.pdf

12:25 → 12:45 CONFERENCE END