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Dr Zumalacarregui, Miguel (Max Planck Institute for Gravitational Physics - Albert Einstein Institut)25/05/2026, 09:30
Just like light, gravitational waves (GWs) are gravitationally lensed by massive objects in the Universe. Moreover, their low frequency, phase coherence, and lack of absorption make GWs complementary to lensed electromagnetic sources. In addition to gravitational magnification and the formation of multiple images, lensed GWs exhibit genuine wave-propagation effects such as diffraction, that...
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Prof. Rubiera-Garcia, Diego (Complutense University of Madrid)25/05/2026, 11:00
The field of black hole imaging - the observational appearance of a black hole when illuminated by its accretion disk - has quickly become one of our main tools in order to test the strong-field regime of the gravitational interaction. In this talk I will discuss the conceptual foundations of this field and discuss the features of images of several kinds of modified black holes and horizonless...
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Prof. Sáez-Chillón Gómez, Diego25/05/2026, 11:40
The reconstruction of the images of the supermassive objects at the centres of the M87 and Milky Way galaxies show two objects characterized by a central depression in luminosity (the so-called shadow) and a ring-shaped light structure around them. Both properties are closely linked to the emission intensity profile of the accretion disk and to the structure of spacetime. In addition, the...
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28/05/2026, 17:00
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Ruchika, Ruchika (University of Salamanca)
As next-generation telescopes and observational surveys continue to expand the boundaries of our understanding, tensions and discrepancies between observational datasets are becoming increasingly prominent. In this work, we focus on one such discrepancy: the differences between 2D and 3D Baryon Acoustic Oscillation (BAO) measurements. Without extending beyond the standard $\Lambda$CDM...
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Marañón González, Francisco Javier (Universidad de Valencia - IFIC)
We present a closed-form framework for the renormalized stress-energy tensor of a scalar quantum field in arbitrary $3+1$-dimensional curved spacetimes through a reformulation of the Hadamard scheme. This approach allows one to construct explicit expressions bypassing the standard mode-sum procedure and rendering the semiclassical field equations more tractable. As an application, we construct...
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Ovcharenko, Hryhorii (Charles University, Faculty of Mathematics and Physics, Institute of Theoretical Physics, V Holesovickach 2, 18000 Prague 8, Czechia)
We present a large family of twisting and expanding solutions to the Einstein-Maxwell equations of algebraic type D, for which the two double principal null directions (PNDs) of the Weyl tensor are not aligned with the null eigendirections of the Faraday tensor. In addition to systematically deriving this new class, we present its various metric forms and convenient parameterizations. We show...
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Silva, Francisco (Faculdade de Ciências da Universidade de Lisboa)
In this talk, we investigate the horizon structure of accelerating black holes described by the C-metric, including its superaccelerating limit. We then analyze the stability of the Cauchy horizon in these configurations using Christodoulou’s formulation of Strong Cosmic Censorship.
To this end, we classify the families of quasinormal modes of the spacetime and study their properties for...
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Mr Peñalver Mares, Daniel (Universitat de València - IFIC)
In the context of Hawking-like radiation in sonic black holes formed by BECs we investigate the modifications of the emission spectrum caused by a finite width of the sonic transition region connecting the subsonic to supersonic flow [1].
Acoustic black holes formed by Bose-Einstein condensates (BEC) undergoing transonic motion have shown the presence of Hawking-like radiation [2,3,4]. The...
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Giorgi, Giacomo (Universidad de Murcia)
In this talk, I will give a brief introduction to p-brane Aristotelian geometry, the underlying geometry of physical models without boost symmetry, and take the first steps in constructing matter-coupled Aristotelian gravity theories through a conformal approach. I will distinguish between three cases of Aristotelian gravity: electric, magnetic, and electric-magnetic, and then discuss how to...
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Pnigouras, Pantelis (University of Alicante)
During the late stages of a neutron star binary inspiral finite-size effects come into play, with the tidal deformability of the supranuclear density matter leaving an imprint on the gravitational-wave signal. As demonstrated in the case of GW170817—the first direct detection of gravitational waves from a neutron star binary—this can lead to constraints on the neutron star equation of state....
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Omarouayache, Amin (University of Sheffield)
We present a unified geometric framework for hidden
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symmetries in the broad class of Conformal St\"{a}ckel Spacetimes. While the
analytic separability of the Hamilton-Jacobi equation is well-established for
specific metrics, the geometric origin of the associated Conformal
Killing-St\"{a}ckel tensors has remained obscured by the limitations of standard
Killing-Yano theory, which often... -
Riahi, Natascha (Universität Wien)
Unimodular quantum cosmology results in a Schrödinger-like equation that governs the dynamics of the wave function of the universe.
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The explicit time dependence makes it possible to compare directly and independently the dynamics of the expectation values of the scale factor, the Hubble parameter and the matter density with their classical counterparts. We construct wave packet solutions... -
Pravda, Vojtech (Institute of Mathematics of the Czech Academy of Sciences)
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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Vicente-Cano, Aitor (ICCUB - University of Barcelona)
It has recently been shown that the Schwarzschild singularity is generically resolved by the introduction of infinite towers of higher-curvature corrections to the Einstein-Hilbert action. In such theories, matter collapse leads to the formation of regular black holes. In my talk, I will present new results on spherically symmetric stars within this framework, showing how Buchdahl's...
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Gadioux, Maxime (University of Cambridge)
A few years ago, Kehle and Unger proved that, by sending finely-tuned pulses of a charged scalar field into a black hole, it is possible to form an extremal Reissner-Nordström black hole in finite time, i.e. the third law is false. The proof makes use of characteristic gluing: a framework to build solutions to Einstein's equations by gluing two regions of spacetime along a null cone. In this...
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Prof. Sakellariadou, Maria (King's College Londom)
I will summarise the results of the LIGO-Virgo-KAGRA paper arXiv:2510.26848 [gr-qc]
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In this paper we derive gravitational-wave background energy density upper limits from the O1-O4a data to constrain parameters associated with various possible processes in the early Universe: first-order phase transitions, cosmic strings, domain walls, stiff equation of state, axion inflation, second-order... -
Estonba-Loinaz, Julen (EHU)
Domain walls arise in theories where a discrete symmetry is spontaneously broken, a mechanism that appears in a wide range of high-energy physics models and makes the formation of domain walls in the early Universe a well-motivated possibility. In this work, we study the evolution of domain wall networks by analysing their scaling regime, an attractor solution in which the network evolves...
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Dr Chakraborty, Sumanta (IACS)
Tidal Love numbers provide us a handle to test the nature of compact objects, as well as theories of gravity. There have been several clarifications recently, which makes our understanding of these Love numbers better. But further investigations have led to more confusion. I plan to discuss these recent developments and the confusing nature of recent literature on these issues. I will show...
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del Rio, Adrian (Universidad Carlos III de Madrid)
Maxwell's equations in vacuum exhibit a duality invariance under electric-magnetic rotations. This is a Noether symmetry of the source-free Maxwell theory in any curved spacetime, and implies that the circular polarization state (the Stokes V parameter) of classical electromagnetic waves is conserved during propagation, even in the presence of strong gravitational fields.
Remarkably,...
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Aranguren, Eneko (University of the Basque Country (EHU))
Static and spherically symmetric isotropic compact stars are known to exist and be unique for a given monotonic equation of state E(P) and central pressure Pc, provided that Λ ≤ 0, or 0 < Λ < κE(r)/2 holds inside the star. In this work, we extend these results in two directions. First, we relax the standard condition for monotonicity and smoothness of E(P), and generalize the formalism for...
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Castells, Lucía (University of Barcelona)
We perform a detailed holographic analysis of linear fluctuations in a strongly coupled plasma subject to a first-order phase transition. This analysis is done through the characterization of the energy-momentum tensor correlation functions across the phase diagram. Particular attention is given to the behavior of modes near the spinodal region of the phase transition, where the instability...
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Aresté Saló, Llibert
I present the first numerical simulations of binary black holes and binary neutron star mergers in scalar–Gauss–Bonnet gravity performed in the modified puncture gauge, which is a well-motivated theory from an effective field theory point of view. Implemented within both GRChombo and MHDuet Numerical Relativity codes, our modified formulation enables stable evolution through merger and...
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Papajčík, Matúš (Charles University)
Gravitational fields are typically described in terms of local curvature, but the physical interpretation of curvature is not immediately evident. This motivates the study of the motion of test particles, whose relative acceleration is governed, in the simplest approximation, by the equation of geodesic deviation.
In this talk, we apply this concept within topologically massive gravity, a...
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Prof. Santos, JOAO (UFCG, Leibniz University and University of Heidelberg)
The Fast Radio Bursts (FRBs) are some of the most intriguing radio phenomena measured in radio astronomy \cite{lorimer}. These energetic bursts have extremely high radio luminosities, corresponding to $\sim 10^{36} \,–\, 10^{44}$ $\mathrm{erg \,s}^{-1}$, which is not far from gamma ray bursts. Since their discovery in 2007, several investigations have been proposed to model their sources and...
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Olmedo, Javier (Universidad de Granada)
We investigate quantum entanglement in a one-dimensional cavity with an accelerating boundary, serving as a model of Hawking-like particle creation. Employing logarithmic negativity, we study correlations between selected modes and the rest of the field, and for pure states we reconstruct partner modes using the Hotta-Schützhold-Unruh relation. By analyzing vacuum, squeezed, and thermal...
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Hennigar, Robie
Regular, singularity-free black holes have been studied for more than sixty years as a possible resolution of the black hole singularity problem. Progress in this direction, however, has been limited by the lack of a robust dynamical mechanism for their formation. I will argue that, if regular black holes are relevant to the ultimate resolution of spacetime singularities, they are most likely...
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Ossowski, Maciej (Jagiellonian University)
Isolated horizons provide a local generalization of black hole horizons that does not require the existence of a global symmetry and admits matter content arbitrarily close to the surface. Remarkably, in General Relativity, the geometries of Petrov Type D and extremal isolated horizons are governed by equations stated on a 2D local section of the horizon, namely the Petrov type D Equation and...
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Beltrán Jiménez, Jose (University of Salamanca)
The Cosmological Principle establishes the symmetries of the Universe on large scales. The inflationary paradigm and observations suggest that the universe has nearly flat spatial sections and, consequently, it has an approximate Euclidian symmetry group. Most cosmological scenarios realise this symmetry in a trival manner, although some non-trivial realisations have also been explored....
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Martínez Lobo, Jhan Nicolás (Universidad Industrial de Santander)
Our purpose is to give a step forward in the search of nature's options to describe classical gravity. Two reasonable hypotheses are invoked: the spacetime is described by a smooth manifold, which might or might not be Riemannian, and the classical gravitational dynamics is intimately related to the laws of thermodynamics (Jacobson's programme). We have found that the Einstein-Hilbert's...
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DEL VALLE CALZADA, PELAYO (Departamento de Física, Universidad de Alicante)
We develop a statistical framework for logarithmic corrections to black-hole entropy by modeling the horizon as a collection of $N$ identical, non-interacting quantum regions, each carrying a finite set of commuting discrete observables. For fixed collective observables, the horizon is described microcanonically, and a statistical analysis yields
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$$
S_{\mathrm{micro}}(A)= \alpha\,... -
Laporte, Cristóbal (University of Barcelona)
Quantum gravity corrections at the classical level are typically expected to be negligible. In this talk, I will present a mechanism by which even parametrically small corrections to the Schwarzschild solution, Planck-suppressed at asymptotic scales, become dominant in the near-horizon region. By analyzing linear perturbations around the Schwarzschild background, we find that higher-derivative...
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Martinez Donato, Izarne (Univesitat de València)
Nonlinear hyperbolic balance laws with stiff source terms arise in many multiphysics problems, including astrophysical flows where hydrodynamics is coupled with chemical processes. In this work we consider a system of hyperbolic balance laws describing a shock–cloud interaction with a simplified chemical network for ionisation and recombination. This framework is useful in studying the...
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Belkhadria, Zakaria (Université de Genève & Università di Cagliari)
Spontaneous scalarization is a mechanism that allows black holes to develop a non-trivial profile of a scalar field “scalar hair” because of tachyonic instabilities, enabling tests of gravity beyond General Relativity. Motivated by stability and threshold issues in Gauss-Bonnet scalarization, we propose a new model characterized by two nonminimal couplings of the scalar field to both...
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Cisterna, Adolfo (Institute of Theoretical Physics, Charles University)
Constructing exact solutions describing compact objects embedded in dynamical cosmological environments remains a major challenge in General Relativity, with most known results restricted to highly symmetric settings. In this talk, we present new exact solutions and solution-generating techniques that extend the analytical description of dynamical black holes in cosmological...
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Kanatchikov, I (Natl. Quantum Information Center in Gdansk, Poland)
We show that a variety of non-Keplerian galaxy rotation curves, together with the corresponding modifications of the Newtonian potential and dynamics, including MOND, qMOND, and mMOND-type behaviors, can be derived for test particles propagating on a background quantum geometry associated with a fluctuating spin connection, as described by precanonical quantum gravity (pQG).
In particular,...
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Pereñíguez Rodríguez, David
At high frequencies, the dynamics of black holes can be captured by Penrose-limit plane waves adapted to the photon ring. Using that, I will show that gravitational electric–magnetic duality is restored on-shell in that limit, and that this implies QNM isospectrality. I will also show how this perspective on the high-frequency regime can be used to compute exactly nonlinear QNM solutions. I...
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Ogurol, Leyla
We analytically construct initial data for binary black hole systems by solving the Einstein con-
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straint equations within the Bowen–York framework. Allowing for arbitrarily oriented linear mo-
menta and spins, we obtain a perturbative solution of the vacuum Hamiltonian constraint up to third
order in the source parameters. Our solution explicitly incorporates the binary nature of the... -
Lovo, Thomas (SISSA)
Black hole perturbations in general relativity are typically governed by Heun-type differential equations, whose associated connection problem has remained largely unexplored for many years. Recent developments in 2D CFT, however, have led to partial progress on this long-standing issue, allowing for a more transparent treatment of the associated spectral problems, in particular the...
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Málek, Tomáš
We present a classification of four-dimensional gravitational theories exhibiting integrability properties similar to quasi-topological gravity, focusing on metrics that share the symmetries of Schwarzschild and Taub–NUT solutions with spherical, hyperbolic, and planar horizons, as well as their double Wick–rotated counterparts, including B-metrics, the near-horizon extremal Kerr geometry, and...
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Moura, Filipe (ISCTE - Instituto Universitário de Lisboa)
We show that the quasinormal modes, in the eikonal limit, for accelerating (non-rotating) black holes, are related to the angular velocity of the circular null geodesics and to the corresponding Lyapunov exponent, in the same way as the ones for spherically symmetric black holes are. We compute those quasinormal modes and greybody factors for neutral and charged accelerating black holes,...
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Murcia, Ángel (Instituto de Física Teórica)
The celebrated works by Penrose and Hawking established that black holes in general relativity are inevitably doomed to contain singularities in their interiors. This is no longer the case for regular black holes, for which no singularities appear. Recently, it has been shown that the Schwarzschild singularity may be resolved after the addition of an infinite tower of higher-curvature...
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de Cesare, Marco (Scuola Superiore Meridionale (SSM))
I will discuss the scattering problem for a massless scalar field in a Schwarzschild-de Sitter geometry. A rigorous application of the method of matched asymptotic expansions allows us to solve analytically the low-frequency s-wave dynamics, and connect the scalar’s evolution in the proximity of the black-hole horizon with that on cosmological scales. The scattering coefficients, greybody...
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Del Piano, Manuel (Southern Denmark University)
We investigate the backreaction of a massive scalar configuration (“wig”) on a Schwarzschild black hole within a controlled perturbative framework. Working in ingoing Eddington–Finkelstein coordinates, we adopt the test-field approximation and solve the Einstein equations consistently to leading nontrivial order in the scalar stress-energy tensor. The scalar sector is treated using Detweiler’s...
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Olivares, Hector (Universidade de Aveiro)
Extensions of general relativity and of the Standard Model of particle physics predict the existence of exotic compact objects (ECOs) that can achieve compactness high enough to mimic black holes. For the first time, advances in observational techniques such as very-long-baseline interferometry (VLBI) allow us to probe supermassive black hole candidates at high spatial resolution and test some...
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López Oliver, Pau (Università di Genova & Universitat de València)
Quantum field theory predicts that dynamical curved spacetimes can spontaneously excite particle pairs from the quantum vacuum, a phenomenon extensively studied in expanding universes and in scenarios involving gravitational collapse. In this article, we explore particle creation driven by radial oscillations of 3+1-dimensional spherically symmetric compact objects, such as neutron stars,...
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Borgvall Gonzalez, Oskar (Instituto Superior Tecnico)
In string theory, a natural low energy effective action is the Einstein-Gauss-
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Bonnet gravity, in which a Gauss-Bonnet term accompanies the usual Einstein-
Hilbert action. Born-Infeld electrodynamics arises when considering an Abelian
gauge field coupled to the open bosonic string or open superstring. In this talk,
we analyze the superradiant behavior of a massive, charged scalar field... -
Andric, Tomislav (Gran Sasso Science Institute)
The Einstein Telescope (ET) is a proposed third-generation ground-based gravitational-wave observatory designed to extend the sensitivity of current detectors by an order of magnitude and to access frequencies down to a few hertz. This improvement will dramatically increase the observable volume of the Universe and enable precision studies of compact-object populations, cosmology, and...
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Martínez, Álvaro (Charles University-Institute of Theoretical Physics)
The \emph{classical double copy} is a correspondence between solutions of
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Yang--Mills theory and gravity that extends the color-kinematics duality,
originally discovered in the context of scattering amplitudes, to fully
classical field configurations.
Its most familiar exact realization is the Kerr--Schild double copy, which
identifies the Schwarzschild black hole as the gravitational... -
Musso, Marcello
Inferring abundance, position and size of cosmic structures from the initial conditions is a long standing effort in theoretical cosmology.
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It allows (semi-)analytical predictions of mass function, bias and correlation functions of dark matter haloes, and an intuitive understanding of the formation of the cosmic web, a complementary tool to numerical simulations. Standard methods assume that... -
Wagle, Pratik (Max Planck Institute for Gravitational Physics)
Gravitational-wave observations provide a powerful probe of gravity in the strong-field regime, particularly through the ringdown phase of binary black hole mergers, where the signal is governed by damped quasinormal modes. Recent progress has extended quasinormal-mode calculations beyond general relativity using the modified Teukolsky formalism and spectral methods in several theories,...
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Singha, Chiranjeeb
In this talk, I will first discuss the tidal response of rotating BTZ black holes to scalar perturbations, showing that the real part of the response function is non-zero and therefore leads to finite tidal Love numbers (TLNs). The response also exhibits scale-dependent logarithmic running. Extremal rotating BTZ black holes show qualitatively similar behaviour, and I will outline a procedure...
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Cocco, Marta (University of Perugia and Niels Bohr Institute)
Tidal interactions can significantly impact the dynamics of binary systems and their gravitational-wave signals. In particular, for extreme-mass-ratio inspirals (EMRIs), a fully relativistic description is required to capture the interplay between spin, curvature, and orbital dynamics in the strong-field regime.
We study the response of a Kerr black hole to external tidal fields and its...
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Contreras, Ernesto (Universidad de Alicante)
Regular black holes provide a compelling framework to address spacetime singularities through nonlinear electrodynamics, yielding geometries that remain well-behaved at all scales. In this work, we investigate their response to scalar field perturbations and the onset of spontaneous scalarization. Using a general inverse approach, we reconstruct the electromagnetic sector associated with a...
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