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Dr Mariam Bouhmadi-López (University of the Basque Country)29/06/2026, 09:15
Understanding the origin of cosmic acceleration and the persistent H_0 and S_8 tensions remains a major challenge in cosmology. In this talk, I explore alternatives to the standard LambdaCDM model based on both modified gravity and dynamical dark energy. Within the teleparallel framework, I discuss f(Q) and f(T) theories, showing how non-metricity and torsion can lead to novel cosmological...
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Dr Aneta Wojnar (University of Wroclaw)29/06/2026, 10:35Oral talk
This presentation introduces the FuSe Action (CA24101) and its main scientific challenges to a broad audience working on the mathematical formulation of fundamental interactions. A central focus of the talk is the role of thermodynamics in understanding physical phenomena. In particular, the presentation highlights the need for a consistent formulation of thermodynamics in systems governed by...
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Dr Konstantinos Dialektopoulos (University of Malta)29/06/2026, 11:25
In this seminar, I will present a novel mechanism for cosmic acceleration driven by primordial black holes with effective repulsive behavior. Using a new Swiss Cheese cosmological framework, I will discuss four black hole spacetimes—Hayward, Bardeen, Dymnikova, and de Sitter-Schwarzschild—to show that this acceleration emerges naturally from the geometry itself. The results suggest that...
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29/06/2026, 13:30
The f(R)-gravity represents the most straightforward extension of the General Relativity. Among the different possible formulations, the starting action can be selected using the Noether symmetry approach, a phisically motivated criterion based on Noether's theorem aimed at identifying viable models that exhibit symmetries. An advantage in applying such an approach is the reduction of the...
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29/06/2026, 13:30
We investigate static, spherically symmetric black holes in regularised four-dimensional Einstein–scalar–Gauss–Bonnet gravity, with the aim of determining whether the theory admits non-asymptotically flat solutions beyond the known special cases. Working in standard spherical coordinates, we use a Frobenius-type expansion of the symmetry-reduced field equations to classify possible local...
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29/06/2026, 13:55
In Non-Minimally Coupled Weyl Connection Gravity the spacetime geometry is not fully determined by the metric alone, but also involves the Weyl connection characterized by an independent non-metricity vector. As a result, the gravitational sector is enriched by a dynamical vector field, which contributes to the field equations and modifies the curvature terms. This model also introduces an...
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29/06/2026, 13:55
I will talk about static spacetimes that are spherically symmetric in three space dimensions, and have also n extra dimensions with Euclidean symmetry. I show that a specific ansatz leads to a limited set of vacuum solutions of the Einstein field equations, which can also be classified as Weyl solutions. I will talk about properties of these spacetimes investigated through the Kretschmann...
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29/06/2026, 14:20
We consider unified dark sector models in which the fluid can collapse and cluster into halos, allowing for hierarchical structure formation to proceed as in standard cosmology. We show that both background evolution and linear perturbations tend toward those in Λ cold dark matter (ΛCDM) as the clustered fraction f→1. We confront such models with various observational datasets, with emphasis...
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29/06/2026, 14:20
Resonant excitations during inflation can amplify the primordial curvature perturbation within a narrow range of k values. This suggests a novel mechanism to generate Primordial Black Holes (PBHs). We study such resonances within the context of the Running-Mass-Inflation model. Generated PBHs can explain the totality of Dark Matter. The mechanism also predicts enhanced induced Gravitational...
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29/06/2026, 14:45
We investigate the phase structures of Lorentzian Dyonic Taub-NUT-AdS spacetimes with spherical, flat, and hyperbolic horizon geometries. First, we construct a consistent approach for the thermodynamics of these solution, which is verified through the first law, the Gibbs-Duhem relation, and the generalized Smarr relation. Second, to analyze these phases we consider both canonical and mixed...
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29/06/2026, 14:45
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29/06/2026, 15:50
Metric affine gravity (MAG) represents an extension of general relativity (GR) in which the metric and affine connection are independent geometrical variables. This leads to two, in addition to curvature, tensors describing the geometry of spacetime, torsion and nonmetricity. And a new tensor describing its matter content together with the stress energy tensor, the hypermomentum tensor. I will...
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29/06/2026, 15:50
Cartan Khronon framework provides a foundation for unconventional space-time structure with a clock field, dubbed ‘khronon’, which spontaneously breaks the symmetry between space and time. This allows gravitational theory to have a Spin(4) gauge structure with a Euclidean background. This talk aims to clarify the motivation for the Euclidean background, the procedure of dimensional Wick...
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29/06/2026, 16:15
In this talk, I will discuss how a small anisotropic “solid remnant” left over after inflation could affect the early Universe. This model is inspired by solid inflation and its generalizations, in which matter is described by a triplet of fields. In our model, the full internal global Euclidean symmetry of this triplet is broken, leading to anisotropic expansion of the Universe. Superhorizon...
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29/06/2026, 16:15
In this talk, the Spin(4) gauge formulation of spacetime with a Cartan khronon field is presented. As motivation, the relation between Euclidean and Lorentzian descriptions is recalled as a Wick-rotation prescription relating two dynamically equivalent descriptions of the same underlying field configurations, once a time direction is selected by the Cartan khronon. Within this setting, the...
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29/06/2026, 16:40
A review of the question how to put the Cartan Khronon into a gauge-gravity unified field theory is provided. The issues are several-fold, from conceptual to technical: suggestions for future developments are provided. The Cartan Khronon is quite special in its particular balance of self-dual Einstein-Cartan gravity constrained to waywiser form, thus producing ideal dust. However, supplying...
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29/06/2026, 16:40
Scalar-tensor theories of gravity are known to generically admit an effective imperfect fluid description, which leads to a natural interpretation of GR as a state of thermal equilibrium. In particular, it is possible to assign a temperature to nonminimally coupled fields, which increases as the theory deviates from GR. However, this temperature is conformally dependent, and can be arbitrarily...
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29/06/2026, 17:05
Physical processes (including field interactions and cosmological evolution) might have different interpretations in different conformal frames. In this talk, we shall discuss how to consistently transform dissipative phenomena between distinct conformal-frame representations of scalar-tensor gravity, and explore the observable consequences thereof in warm inflation scenarios, where the...
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29/06/2026, 17:05
This work investigates inflation in a left-right symmetric extension of Higgs inflation, formulated in a first-order gravitational framework. Specializing to a single-field inflationary trajectory, the model admits two physically distinct cases: real , associated with complex-conjugate non-minimal couplings, and purely imaginary , associated with real non-minimal couplings.
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We explore the... -
Prof. Saeed Rastgoo (University of Alberta)30/06/2026, 10:351Oral talk
I present a new model of a black hole derived systematically from deforming the canonical algebra inspired by the generalized uncertainty principle (GUP). This model has two quantum parameters controlling the onset and strength of quantum gravity effects. I will discuss the geometry of both the static case and the rotating model derived using Newman-Janis algorithm. Furthermore, I show how a...
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Manuel Hohmann (University of Tartu)30/06/2026, 11:00
Many different formulations of general relativity are known. The Palatini action, based on a Lorentz connection and tetrad, can be derived from the MacDowell-Mansouri action, which combines these variables into a Cartan connection. The latter is obtained via gauge fixing and thus explicit symmetry breaking of the Stelle-West action to retain only Lorentz symmetry; the latter enlarges the...
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Fernando Izaurieta (Universidad San Sebastián)30/06/2026, 11:25
A single geometric invariant fixes the relative normalization and structure of gravity, Yang-Mills theory, and fermion kinetic terms, including ghost freedom in the gravitational sector, without tuning. Our results establish a minimal geometric route to unification that does not rely on extra dimensions or symmetry breaking by hand. Unlike previous gauge-gravity constructions, the relative...
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30/06/2026, 13:30
The decay of a metastable (false) vacuum is a crucial non-perturbative phenomenon, as it plays an important role in constraining Standard Model and beyond the Standard Model physics. In particular, it has been shown that gravity can have a significant impact on the calculation of the decay rate. In this context, it is natural to ask whether different but classically equivalent formulations of...
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30/06/2026, 13:30
It is well known that the Teleparallel Equivalent of General Relativity (TEGR) is locally dynamically equivalent to General Relativity in the absence of matter. However, for decades, discussions have persisted about this equivalence when matter is present. These discussions primarily focus on the choice of coupling prescription, whether to use the metric teleparallel or the Levi-Civita one,...
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30/06/2026, 13:55
We study the primary constraint structure of newer general relativity, a gravity theory based on a torsionless teleparallel geometry. The gravitational action consists of a scalar built from quadratic combinations of the nonmetricity tensor with arbitrary coefficients in the Lagrangian. We perform a 3+1 decomposition of the Lagrangian and compute the canonical momenta associated with the...
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30/06/2026, 13:55
Already in general relativity, much of the most interesting physics has to do with semi-classical extensions and their physical effects. Early on, foundational issues were addressed through the introduction of the Unruh–DeWitt detect model which allowed an operational notion of particle detection. This described the then-recently discovered, semi-classical effects—like the Unruh effect and...
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30/06/2026, 14:20
We perform a 3+1 decomposition in a general symmetric metric-affine theory, classifying the extrinsic tensors and deriving the generalized Gauss-Codazzi relations. The latter are exploited to perform the teleparallel limit in a model-independent fashion, thus identifying the extrinsic non-metricity tensor which plays the role of the extrinsic Riemannian curvature. We further prove that no...
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30/06/2026, 14:20
It has been known since 1998 that the dynamics of the bosonic form fields in supergravity can be formulated as a twisted first-order self-duality relation in a Lie superalgebra. I will extend the formalism to the gravity sector and describe how Einstein's equations in vacuum can be derived in a similar way. Conversely, diffeomorphisms can be generalised and unified with gauge transformations...
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30/06/2026, 14:45
We present information geometry from the perspective of divergences, which define a generally asymmetric notion of separation. From this starting point, we show how both the metric tensor and affine connection naturally emerge, and we emphasize the role of nonmetricity in this framework. Within this setting, we demonstrate that a Brownian bridge subject to a canonical physical constraint...
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30/06/2026, 14:45
In metric–affine geometry, autoparallels are generically non-variational, i.e.\,, they are not the extremals of any action integral. The existence of a parametrization-invariant action principle for autoparallels is a long-standing open problem, which is equivalent to the so-called Finsler metrizability of the connection -- that is, to the fact that these autoparallels can be interpreted as...
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30/06/2026, 15:10
The fundamental interactions of nature are formulated in terms of fields classified by mass and spin. Two of the most successful theories, General Relativity (GR) and the Standard Model (SM), can be derived from fields of fixed mass and spin by imposing theoretical consistency conditions. The SM contains well-understood interactions for fields with spin s<2, whereas local interacting theories...
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30/06/2026, 15:10
The series of breakthroughs witnessed at the previous conferences erupted last summer into a full-scale revolution. Presently the foundations of physics and of all sciences are shaken by a kaleidoscopic turmoil. This is a moment at which to revisit the main theme of the conference series.
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Physics cannot rest on a geometrical foundation. The fact that geometrical descriptions are available is... -
Will Barker (Czech Academy of Sciences)01/07/2026, 09:15
Particle dark matter, along with many ultraviolet scenarios, suggest
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that additional low-energy degrees of freedom remain to be discovered.
Theories of new physics may be understood as data models, for which the
Lagrangian couplings are model parameters. The net worth of a theory is
determined by its Bayesian evidence: the likelihood of precision
cosmology data is multiplied by the prior... -
Maria Jose Guzman (University of Tartu, Estonia)01/07/2026, 10:35
In this talk, I will present recent progress in the 3+1 formulation of the metric teleparallel and symmetric teleparallel equivalents of general relativity, TEGR and STEGR. For TEGR, I will discuss the linearized Hamilton's equations and their hyperbolicity properties. Although the original system of differential equations is not hyperbolic, we show that it can be recast as a strongly...
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Martin Krssak (Comenius University in Bratislava)01/07/2026, 11:00
Classical solutions with a finite action play an important role in the path integral quantization of gravity, black hole thermodynamics, and holography. While the teleparallel action avoids the need for boundary terms, it depends on a non-dynamical spin connection that effectively encodes the regularization. We study different choices of this spin connection, as well as various methods for...
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Christian Pfeifer (University of Bremen, ZARM)01/07/2026, 11:251Oral talk
The unification of all physical fields into one mathematical object and the derivation of all physical field equations from that object in one framework is a long-lasting endeavor in fundamental physics. We suggest a new approach to achieve this goal by encoding physical fields into the geometry of the 1-particle phase space on spacetime (the cotangent bundle) through Hamilton geometry. The...
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Kristina Giesel02/07/2026, 09:15
In this talk some recent results in understanding gravitationally induced decoherence from the perspective of relational quantum gravity will be discussed. Starting from microscopic models in which matter fields are coupled to linearised gravity, a gauge-invariant formulation is constructed using relational observables defined in terms of geometric clocks in the context of a reduced phase...
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Vojtech Pravda (Institute of Mathematics of the Czech Academy of Sciences)02/07/2026, 10:35
We study static, spherically symmetric, asymptotically flat and asymptotically (A)dS charged black holes in quadratic gravity. Using the conformal-to-Kundt method, we simplify the field equations and derive the solutions in the form of a power series with coefficients determined by a recurrent formula. In addition to charge and mass, these black holes possess one additional parameter – the...
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Damianos Iosifidis02/07/2026, 11:001Oral talk
I will introduce the Lagrangian formulation of microstructured test bodies containing all spin, dilation and shear charges and moving in a generalized non-Riemannian background. Using the equations of motion derived by this formulation I will study the evolution of the dynamical rest mass of the body. I will show that, due to the presence of non-metricity, the dynamical rest mass is no longer...
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Nassim Bozorgnia02/07/2026, 11:25Oral talk
The Large Magellanic Cloud (LMC) induces a significant time-dependent gravitational perturbation on the Milky Way dark matter halo, altering the local phase-space distribution of dark matter in the Solar neighborhood. Cosmological simulations that sample potential Milky Way formation histories provide a powerful framework to characterize the dynamical response of the halo to such a massive...
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02/07/2026, 13:30
Inspired by the power of algebraic expansions to reveal hidden structures in physical theories, we explore the role of infinite semigroup expansions in the context of gravitational theories, focusing on the derivation of Maxwellian gravity and its relation to the cosmological constant. By systematically extending the symmetry structure of AdS, we unveil a natural path leading from Poincaré...
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02/07/2026, 13:30
We report on the numerical evolutions of black holes with synchronized or resonant hair. We show that in the "very hairy" regime, the horizon gets naturally ejected from the center of its environment. This dynamical splitting is likely to be generic for sufficiently hairy BHs in the broader class of models with synchronized or resonant hair, but possible exceptions may exist.
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02/07/2026, 13:55
Real scalar fields, e.g. the axion, cannot condensate into stationary solitonic configurations to form starlike structures, eventually either dispersing or collapsing. However, by relaxing the stationarity condition on the metric, it has been shown that oscillatory solitonic solutions—known as oscillatons—exist. Oscillatons share several properties with boson stars, including comparable...
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02/07/2026, 13:55
In this talk, I describe in detail how one might understand the termination of the event horizon of a black hole in terms of of quasiregular singularity characterized by points possessing two future-directed light cones and two past-directed light cones (in fact this spacetime is conformal to a region of the 1+1 trousers spacetime). I then discuss Euclidean signature shift-symmetric...
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02/07/2026, 14:20
Recent observations of polarized light from galactic cores motivate the study of polarized exotic compact objects (ECOs), which can mimic the features of black holes (BHs) in the strong-field regime of gravity. In this work, the properties of three ultra-compact classes of models containing light rings are studied — relativistic thin-shell fluid spheres, thin-shell gravitational vacuum stars,...
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02/07/2026, 14:20
A classic theorem of Weyl (1921) states that a Weyl metric—a natural generalisation of a pseudo-Riemannian metric—is uniquely determined by its conformal and projective structures. This theorem forms the basis for the famous Ehlers–Pirani–Schild (EPS) axiomatic reconstruction (1972) of Lorentzian spacetime structure from light rays and the worldlines of massive particles.
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An equivalent... -
02/07/2026, 14:45
The usual approach to perturbation theory presents some mathematical flaws. For instance, when studying gravitational waves (GW) around a Minkwoski background, one usually imposes the weak-field limit, requiring the spacetime metric to be the Minkowski metric plus a small perturbation. However, the bundle of Lorentzian metrics is neither linear nor affine; thus, the addition operation is not...
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02/07/2026, 14:45
The complete set of covariant equations that govern the locally rotationally symmetric torsion spacetimes sourced by Weyssenhoff fluid in Einstein-Cartan-Sciama-Kibble gravity is presented. Using these equations, one can explore in detail the peculiar relationship between conformal structure and torsion. A comprehensive scheme to categorize these torsional spacetimes into distinct classes is...
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Dario Sauro (Theoretical Physics Institute University ofJena)Oral talk
We perform a 3+1 decomposition in a general symmetric metric-affine theory, classifying the extrinsic tensors and deriving the generalized Gauss-Codazzi relations. The latter are exploited to perform the teleparallel limit in a model-independent fashion, thus identifying the extrinsic non-metricity tensor which plays the role of the extrinsic Riemannian curvature. We further prove that no...
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Dr Bilgehan Baris ONERPoster
Mach’s principle can be implemented in general relativity by introducing a vector field, which we call the geometric drift vector, within the framework of teleparallel gravity and the tetrad formalism. We investigate the physical viability of the drift field, the Lorentz covariance of the theory, its limiting cases, and its consistency with current cosmological observations. The model provides...
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Priidik Gallagher (University of Tartu)Oral talk
A review of the question how to put the Cartan Khronon into a gauge-gravity unified field theory is provided. The issues are several-fold, from conceptual to technical: suggestions for future developments are provided. The Cartan Khronon is quite special in its particular balance of self-dual Einstein-Cartan gravity constrained to waywiser form, thus producing ideal dust. However, supplying...
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Pietro Isaia (Università di Torino)Oral or Poster
The usual approach to perturbation theory presents some mathematical flaws. For instance, when studying gravitational waves (GW) around a Minkwoski background, one usually imposes the weak-field limit, requiring the spacetime metric to be the Minkowski metric plus a small perturbation. However, the bundle of Lorentzian metrics is neither linear nor affine; thus, the addition operation is not...
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Ginevra BragaOral talk
Higher-derivative quantum corrections are essential ingredients of scalar-tensor effective field theories (EFTs), yet they generically reintroduce the Ostrogradsky ghost instability that the classical theory was designed to avoid. In this talk, we address this tension by establishing a rigorous equivalence between two independent criteria for theoretical consistency. We consider a general...
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Thomas Guillermo Albers RaviolaPoster
In General Relativity, the Bondi-Sachs formalism is used to study the energy
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emitted from an isolated gravitational system in the form of gravitational waves
as observed at future null-infinity. It introduces the concept of the Bondi
mass, whose decrease is connected to the the news tensor through the famous
Bondi mass loss formula. This work investigates the changes in the Bondi... -
Paul Martin Kull (University of Tartu)Oral or Poster
Our current understanding of the Universe is that it is isotropic, which means that spherically symmetric models of spacetime are the preferred choice for any geometrical considerations about the Universe. However, some observations point to an asymmetry in the CMB, the "axis of evil," that could be explained by a non-isotropic Universe. This can potentially be leveraged to help solve another...
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Dr Bilgehan Baris ONER, Mr Melih GUMUSPoster
Black hole singularities continue to pose a major topic in almost all gravitational theories. Here we propose a geometric picture for regular (non-singular) black hole interiors in teleparallel gravity, formulated in terms of geometric drift vectors. In a comoving tetrad setup, gravity is described by an evolving drift field whose spatial variations give rise to torsion instead of curvature....
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Francesca Spinnato (Scuola Superiore Meridionale)Oral talk
The f(R)-gravity represents the most straightforward extension of the General Relativity. Among the different possible formulations, the starting action can be selected using the Noether symmetry approach, a phisically motivated criterion based on Noether's theorem aimed at identifying viable models that exhibit symmetries. An advantage in applying such an approach is the reduction of the...
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Mahmoud Hashim (Centre for Theoretical Physics, the British University in Egypt)Oral talk
We consider unified dark sector models in which the fluid can collapse and cluster into halos, allowing for hierarchical structure formation to proceed as in standard cosmology. We show that both background evolution and linear perturbations tend toward those in Λ cold dark matter (ΛCDM) as the clustered fraction f→1. We confront such models with various observational datasets, with emphasis...
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Joosep Lember (University of Tartu)Oral or Poster
Shortcomings of GR motivate the study of extended theories of gravity, while other fundamental interactions, successfully formulated as gauge theories, drive the development of a gauge theory of gravity. We will present a gauge-theoretic framework of gravity based on spontaneous symmetry breaking of the conformal group to the Lorentz group. The geometry can be defined from a connection and two...
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David F. Mota
Several modifications to general relativity have been proposed to explain the nature of dark energy and the accelerated expansion of the Universe. In this talk, I will review the current status of modified theories of gravity, focusing on astrophysical probes in the nonlinear regime. I will begin by outlining the expected behavior of theories beyond General Relativity in various astrophysical...
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Ilaria Andrei (University of Tartu)Oral talk
Metric affine gravity (MAG) represents an extension of general relativity (GR) in which the metric and affine connection are independent geometrical variables. This leads to two, in addition to curvature, tensors describing the geometry of spacetime, torsion and nonmetricity. And a new tensor describing its matter content together with the stress energy tensor, the hypermomentum tensor. I will...
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Petri Muinonen (Independent researcher)1Poster
We present a non-perturbative framework in which two compatible 4D spatial geometries emerge from sheer arithmetic properties of growing set of positive integers. The process of adding integers conceived as time, Lagrange's four-square theorem provides the dimensional foundation. Integer distances between integers in a ring algebra admit decomposition into four coordinates, with multiple...
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Mr Matteo Pinna1Poster
The Discrete Emergent Gravity (DEG) framework derives macroscopic physics from a single postulate: spacetime consists of N Planck-scale atoms, each carrying g = 442 internal quantum states from an SU(21)×U(1) gauge structure, governed by H = 0. No parameters are fitted to observation at any stage.
Two results are highlighted. The observed cosmological constant Λ = (1.088 ± 0.030) × 10⁻⁵²...
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Adrián Casado-Turrión (Center for Physical Sciences and Technology (FTMC))Oral talk
Physical processes (including field interactions and cosmological evolution) might have different interpretations in different conformal frames. In this talk, we shall discuss how to consistently transform dissipative phenomena between distinct conformal-frame representations of scalar-tensor gravity, and explore the observable consequences thereof in warm inflation scenarios, where the...
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Purnendu Karmakar (University of Tartu)Oral or Poster
We discuss the implications of the most recent DESI Baryon Acoustic Oscillations (BAO) DR2 and DESyr5 compilation of supernovae (SNe) datasets for modified gravity, focusing on non-metricity-based f(Q) theory, by employing a ‘model-independent’ approach. We reconstruct dark energy density, which is then extended to estimate the perturbation-level quantities, sourced by the modified gravity,...
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Ms Mehraveh Nikjoo (University of Gdansk)Oral talk
This work investigates inflation in a left-right symmetric extension of Higgs inflation, formulated in a first-order gravitational framework. Specializing to a single-field inflationary trajectory, the model admits two physically distinct cases: real $\bar{\gamma}$, associated with complex-conjugate non-minimal couplings, and purely imaginary $\bar{\gamma}=i\gamma_I$, associated with real...
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Justin FengOral talk
In this talk, I describe in detail how one might understand the termination of the event horizon of a black hole in terms of of quasiregular singularity characterized by points possessing two future-directed light cones and two past-directed light cones (in fact this spacetime is conformal to a region of the 1+1 trousers spacetime). I then discuss Euclidean signature shift-symmetric...
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Daniel RačkoOral or Poster
In this talk, I will discuss how a small anisotropic “solid remnant” left over after inflation could affect the early Universe. This model is inspired by solid inflation and its generalizations, in which matter is described by a triplet of fields. In our model, the full internal global Euclidean symmetry of this triplet is broken, leading to anisotropic expansion of the Universe. Superhorizon...
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Miguel ZilhãoOral talk
We report on the numerical evolutions of black holes with synchronized or resonant hair. We show that in the "very hairy" regime, the horizon gets naturally ejected from the center of its environment. This dynamical splitting is likely to be generic for sufficiently hairy BHs in the broader class of models with synchronized or resonant hair, but possible exceptions may exist.
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Sebastian Schuster (Stockholm University)Oral talk
Already in general relativity, much of the most interesting physics has to do with semi-classical extensions and their physical effects. Early on, foundational issues were addressed through the introduction of the Unruh–DeWitt detect model which allowed an operational notion of particle detection. This described the then-recently discovered, semi-classical effects—like the Unruh effect and...
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Daniel Blixt (Chalmers University of Technology)Poster
General relativity is conventionally described by the Einstein-Hilbert action in terms of the curvature of the Levi-Civita connection. However, this formulation does not come without foundational issues. It needs to be supplemented by boundary terms in order for it to have a well-defined variational principle as well as finite sensible derivations of quantities such as mass. Boundary terms can...
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Dr Laur Järv (University of Tartu)Poster
In the phase space perspective, scalar field slow roll inflation is described by a heteroclinic orbit from a saddle type fixed point to a final attractive point. In many models the saddle point resides in the scalar field asymptotics, and thus for a comprehensive view of the dynamics a global phase portrait is necessary. For this task, in the literature one mostly encounters dynamical...
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Stylianos Papadopoulos (University of Tartu, Estonia)Oral or Poster
\textbf{Abstract:\}
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In this talk, the Spin(4) gauge formulation of spacetime with a Cartan khronon field is presented. As motivation, the relation between Euclidean and Lorentzian descriptions is recalled as a Wick-rotation prescription relating two dynamically equivalent descriptions of the same underlying field configurations, once a time direction is selected by the Cartan khronon. Within... -
Stylianos Papadopoulos (University of Tartu, Estonia)Poster
Abstract
We present the Spin(4) gauge formulation of gravity based on a Cartan Khronon field, in which spacetime geometry is described through a gauge-theoretic framework and the coframe structure emerges from the covariant derivative of the Khronon field. The theory naturally decomposes into self-dual and anti-self-dual sectors associated with the Spin(4) connection, allowing for a chiral...
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Joakim Flinckman (Stockholm University)Poster
The fundamental interactions of nature are formulated in terms of fields classified by mass and spin. Two of the most successful theories, General Relativity (GR) and the Standard Model (SM), can be derived from fields of fixed mass and spin by imposing theoretical consistency conditions. The SM contains well-understood interactions for fields with spin s<2, whereas local interacting theories...
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Martin Kováč (Comenius University Bratislava)Poster
We present the Hamiltonian formulation of the Teleparallel Gravity in the language of differential forms. Using a (3+1) decomposition, we identify the dynamical variables and their canonically conjugate momenta. The Hamiltonian is shown to be a linear combination of the Hamiltonian and diffeomorphism constraints arising from the teleparallel field equations. Adding the Nieh-Yan boundary term...
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Dr Armin van de Venn (University of Tartu)Oral talk
We present information geometry from the perspective of divergences, which define a generally asymmetric notion of separation. From this starting point, we show how both the metric tensor and affine connection naturally emerge, and we emphasize the role of nonmetricity in this framework. Within this setting, we demonstrate that a Brownian bridge subject to a canonical physical constraint...
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In the phase space perspective, scalar field slow roll inflation is described by a heteroclinic orbit from a saddle type fixed point to a final attractive point. In many models the saddle point resides in the scalar field asymptotics, and thus for a comprehensive view of the dynamics a global phase portrait is necessary. For this task, in the literature one mostly encounters dynamical...
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Ujjwal Agarwal (Institute of Theoretical Physics, Charles University)Oral talk
The complete set of covariant equations that govern the locally rotationally symmetric torsion spacetimes sourced by Weyssenhoff fluid in Einstein-Cartan-Sciama-Kibble gravity is presented. Using these equations, one can explore in detail the peculiar relationship between conformal structure and torsion. A comprehensive scheme to categorize these torsional spacetimes into distinct classes is...
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Diego Molina (Universidad Arturo Prat)Oral or Poster
Inspired by the power of algebraic expansions to reveal hidden structures in physical theories, we explore the role of infinite semigroup expansions in the context of gravitational theories, focusing on the derivation of Maxwellian gravity and its relation to the cosmological constant. By systematically extending the symmetry structure of AdS, we unveil a natural path leading from Poincaré...
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Tomi Koivisto (University of Tartu)1Oral talk
The series of breakthroughs witnessed at the previous conferences erupted last summer into a full-scale revolution. Presently the foundations of physics and of all sciences are shaken by a kaleidoscopic turmoil. This is a moment at which to revisit the main theme of the conference series.
Physics cannot rest on a geometrical foundation. The fact that geometrical descriptions are available...
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Margarida Lima (Instituto Superior Técnico)Oral talk
In Non-Minimally Coupled Weyl Connection Gravity the spacetime geometry is not fully determined by the metric alone, but also involves the Weyl connection characterized by an independent non-metricity vector. As a result, the gravitational sector is enriched by a dynamical vector field, which contributes to the field equations and modifies the curvature terms. This model also introduces an...
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Lehel Csillag (Transilvania University Brasov)Oral talk
In metric–affine geometry, autoparallels are generically non-variational, i.e.\,, they are not the extremals of any action integral. The existence of a parametrization-invariant action principle for autoparallels is a long-standing open problem, which is equivalent to the so-called Finsler metrizability of the connection -- that is, to the fact that these autoparallels can be interpreted as...
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João LuísOral talk
Real scalar fields, e.g. the axion, cannot condensate into stationary solitonic configurations to form starlike structures, eventually either dispersing or collapsing. However, by relaxing the stationarity condition on the metric, it has been shown that oscillatory solitonic solutions—known as oscillatons—exist. Oscillatons share several properties with boson stars, including comparable...
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Katherine Horton (University College London)Poster
I will present certain results from a paper in preparation in which we discuss the motion of massive uncharged and charged test particles in space-times of electric and dyonic black holes which carry scalar hair. We will look at the stable and unstable circular orbits for both charged and uncharged particles, and aim to demonstrate how the presence of the scalar hair of the black hole changes...
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Hanna Liis Tamm (University of Tartu)Oral talk
Recent observations of polarized light from galactic cores motivate the study of polarized exotic compact objects (ECOs), which can mimic the features of black holes (BHs) in the strong-field regime of gravity. In this work, the properties of three ultra-compact classes of models containing light rings are studied — relativistic thin-shell fluid spheres, thin-shell gravitational vacuum stars,...
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Carmen Ferrara (Scuola Superiore Meridionale)Oral talk
We study the primary constraint structure of newer general relativity, a gravity theory based on a torsionless teleparallel geometry. The gravitational action consists of a scalar built from quadratic combinations of the nonmetricity tensor with arbitrary coefficients in the Lagrangian. We perform a 3+1 decomposition of the Lagrangian and compute the canonical momenta associated with the...
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Mindaugas Karciauskas (Center for Physical Sciences and Technology (FTMC))1Oral talk
Resonant excitations during inflation can amplify the primordial curvature perturbation within a narrow range of k values. This suggests a novel mechanism to generate Primordial Black Holes (PBHs). We study such resonances within the context of the Running-Mass-Inflation model. Generated PBHs can explain the totality of Dark Matter. The mechanism also predicts enhanced induced Gravitational...
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Peter Mészáros (Department of Theoretical Physics, Comenius University, Bratislava, Slovakia)Oral talk
I will talk about static spacetimes that are spherically symmetric in three space dimensions, and have also n extra dimensions with Euclidean symmetry. I show that a specific ansatz leads to a limited set of vacuum solutions of the Einstein field equations, which can also be classified as Weyl solutions. I will talk about properties of these spacetimes investigated through the Kretschmann...
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Daniel Blixt (Chalmers University of Technology)Oral or Poster
Metric teleparallelism assumes both the curvature of the affine connection and non-metricity to vanish. Within this framework it is possible to construct an action which is quadratic in torsion and parity-preserving (known as new general relativity). For decades it was thought that only two subcases of this theories would be ghost-free. One being equivalent with general relativity, and the...
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Hanna Liis Tamm (University of Tartu)Poster
The increased precision of horizon-scale imaging achieved by interferometric instruments motivates a closer examination of the shadow of the black hole (BH) and its constraints on the geometry in the center of Sgr A$^\ast$. While these have been applied to solutions in general relativity (GR) and in its metric modifications, we investigate the shadow sizes set by various non-Riemannian...
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Lucy Zheng (University of Tartu)Oral talk
Cartan Khronon framework provides a foundation for unconventional space-time structure with a clock field, dubbed ‘khronon’, which spontaneously breaks the symmetry between space and time. This allows gravitational theory to have a Spin(4) gauge structure with a Euclidean background. This talk aims to clarify the motivation for the Euclidean background, the procedure of dimensional Wick...
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Roald Heinrich Ivask (University of Tartu)Oral or Poster
Because of the mixing of gravity and inertia in GR, no coordinate-independent local energy density of the gravitational field can be defined. Many years of theoretical explorations have revealed that the same GR field equations can also be derived from a more general teleparallel connection which carries torsion and nonmetricity while the curvature vanishes. After further development of the...
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Michal Stano (Institute of Mathematics of the Czech Academy of Sciences)Oral or Poster
We investigate static, spherically symmetric black holes in regularised four-dimensional Einstein–scalar–Gauss–Bonnet gravity, with the aim of determining whether the theory admits non-asymptotically flat solutions beyond the known special cases. Working in standard spherical coordinates, we use a Frobenius-type expansion of the symmetry-reduced field equations to classify possible local...
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Sotirios Karamitsos (University of Tartu)Oral talk
Scalar-tensor theories of gravity are known to generically admit an effective imperfect fluid description, which leads to a natural interpretation of GR as a state of thermal equilibrium. In particular, it is possible to assign a temperature to nonminimally coupled fields, which increases as the theory deviates from GR. However, this temperature is conformally dependent, and can be arbitrarily...
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Sofía Vidal Guzmán (University of Tartu)Poster
In this contribution we analyze the effects of a finite temperature equation of state on the equilibrium structure of white dwarfs in massive Brans-Dicke theory as well as for the symmetron and dilaton screening mechanisms. We show that assuming a non-zero temperature effectively results in a larger radius while leaving the total mass of the star essentially unchanged. We discuss the interplay...
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Dr Jakob Palmkvist (Chalmers University of Technology)1Oral talk
It has been known since 1998 that the dynamics of the bosonic form fields in supergravity can be formulated as a twisted first-order self-duality relation in a Lie superalgebra. I will extend the formalism to the gravity sector and describe how Einstein's equations in vacuum can be derived in a similar way. Conversely, diffeomorphisms can be generalised and unified with gauge transformations...
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Petri Muinonen (Independent researcher)Poster
We show that the observed value of the cosmological constant, Λ ≈ 10⁻¹²² in Planck units, follows from two independently meaningful and empirically known scales, with no free parameters and no fine-tuning. Building on the discrete arithmetic framework presented in the companion contribution, in which space is a 3-sphere whose radius grows as the square root of the total element count N, we...
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Tomi Koivisto (University of Tartu)Poster
A covariant reformulation of Einstein gravity in terms of an auxiliary frame field renders the canonical Noether current for translations tensorial, and thereby admits a local covariant interpretation of gravitational-wave energy. For both weak spin-2 waves and exact plane waves, we recover the expected energy in a rigid detector frame, but zero energy in the canonical frame co-moving with the...
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Sebastian Brezina (Comenius University in Bratislava)Oral talk
It is well known that the Teleparallel Equivalent of General Relativity (TEGR) is locally dynamically equivalent to General Relativity in the absence of matter. However, for decades, discussions have persisted about this equivalence when matter is present. These discussions primarily focus on the choice of coupling prescription, whether to use the metric teleparallel or the Levi-Civita one,...
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Muhammad Azzam Alwan (Hiroshima University)Poster
We study the thermal evolution of neutron stars in covariant f(Q) gravity, extending our previous work (Alwan, 2025), by coupling a modified TOV with the BSk21 equation of state to the NSCool thermal evolution calculation for non-linear f(Q) models; logarithmic, exponential, and quadratic. Since f(Q) modifications act purely through stellar structure rather than microphysics, they shift the...
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Adel Awad (Ain Shams U & American University in Cairo)Oral talk
We investigate the phase structures of Lorentzian Dyonic Taub-NUT-AdS spacetimes with spherical, flat, and hyperbolic horizon geometries. First, we construct a consistent approach for the thermodynamics of these solution, which is verified through the first law, the Gibbs-Duhem relation, and the generalized Smarr relation. Second, to analyze these phases we consider both canonical and mixed...
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Orest Hrycyna (National Centre for Nuclear Research)Oral or Poster
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Filippo Contino (Scuola Superiore Meridionale)Oral talk
The decay of a metastable (false) vacuum is a crucial non-perturbative phenomenon, as it plays an important role in constraining Standard Model and beyond the Standard Model physics. In particular, it has been shown that gravity can have a significant impact on the calculation of the decay rate. In this context, it is natural to ask whether different but classically equivalent formulations of...
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Philip Schwartz (Leibniz Universität Hannover, Institut für Theoretische Physik)Oral talk
A classic theorem of Weyl (1921) states that a Weyl metric—a natural generalisation of a pseudo-Riemannian metric—is uniquely determined by its conformal and projective structures. This theorem forms the basis for the famous Ehlers–Pirani–Schild (EPS) axiomatic reconstruction (1972) of Lorentzian spacetime structure from light rays and the worldlines of massive particles.
An equivalent...
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