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4th Einstein Telescope Annual Meeting
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Opatija, Croatia
Opatija, Croatia
Description
The 4th Einstein Telescope Annual Meeting presents an opportunity to discuss key aspects of the ET collaboration and design.
Hosted by the University of Rijeka, the event will be held at the Drago Gervais multifunctional hall, located in the heart of the nearby Opatija.
The meeting is open to all members of the ET collaboration, beginning on the morning of Tuesday, November 11, and concluding on Friday, November 14 at lunchtime.
Participants can join all sessions online via Zoom. Zoom links will be provided as attachments in the session timetable.
Social events:
Early Career Researchers Meeting: November 11
Conference Dinner: November 13
Local Organizing Committee:
Marin Karuza, Marina Manganaro, Nenad Kralj, Karlo Veličan, Jonatan Lerga from University of Rijeka and Željka Bošnjak from University of Zagreb
We look forward to welcoming all participants, both in person and online, for a productive and engaging meeting!
The registration is not needed for online participants.
Contact
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Registation
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Plenary: Plenary 1: Welcome and ET Collaboration Overview
Plenary 1: Welcome and ET Collaboration Overview
Conveners: Harald Lueck, Michele Punturo (INFN)-
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Welcome by local authorities
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LOC practical indicationsSpeaker: Marin Karuza
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Recent and future challenges in ET and in the ET CollaborationSpeakers: Harald Lueck, Michele Punturo (INFN)
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ET CoordinatorsSpeakers: Antonio Zoccoli (INFN), Jorgen D'Hondt, marco pallavicini
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Coffee
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Plenary: Plenary 2: ET Collaboration Activities
Plenary 1: Welcome and ET Collaboration Overview
Conveners: Harald Lueck, Michele Punturo (INFN)- 6
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ET = Excellent Training: developing an Einstein Telescope training network for early-career scientists and engineers
In this talk I will provide a short update on work being carried out as part of the ET-PP project to develop plans for an Einstein Telescope mentorship and training programme. I will first briefly summarise recent consultations with early-career colleagues on the scope of a possible ET mentoring programme, before switching focus to the question of what a collaboration-wide, coordinated approach to an ET training network might look like. Finally, I will launch a short google forms survey seeking feedback from ET Collaboration members on training needs and possible future opportunities.
Speaker: Martin Hendry (University of Glasgow) - 9
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Lunch
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Instrument Science (ISB): ISB - Contributed talksConveners: Jan Harms, Stefan Hild
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The status of CAOS laboratory
The CAOS international laboratory (Center for Gravitational Wave and Seismology Applications) of the University of Perugia, in collaboration with INFN and EGO and primarily funded by the ETIC (Einstein Telescope Infrastructure Consortium) project, is mainly designed to develop and test new technologies for the Einstein Telescope. The facility will focus on the development and fine-tuning of new 12-meter seismic attenuators, low-noise automatic control systems, and payload integration techniques, supported by innovative 15-meter truncated-cone vacuum chambers. CAOS aims to become a reference hub for scientific collaboration and a platform for developing new ideas. This presentation will provide an update to the scientific community on the progress of civil works, seismic attenuators, vacuum chambers, and laboratory instrumentation.
Speaker: Gabriele Capoccia (INFN-PG) -
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Status and Plans of ETpathfinder
ETpathfinder is a R&D fieldlab aiming to provide a testbed for research, development, integration and validation of ET-LF technologies in an environment similar to ET. In particular the interferometer configuration featuring four cryogenic towers and two flexible bench towers (for input and output optics) allows for the construction of full Fabry-Perot Michelson interferometer, with a displacement sensitivity of 1e-18m/sqrt(Hz). This talk will give an status update of the ETpathfinder project and detail some of the recent achievements, not only from the academic partners within the ETpathfinder collaboration, but also highlighting several contributions from industry partners. We conclude by giving an outlook of potential future developments.
Speaker: Prof. Stefan Hild (Maastricht University and Nikhef) -
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Summary of MAD substrate discussion
Identifying suitable substrate materials is a key challenge for the development of future cryogenic gravitational-wave detectors. Achieving both low thermal noise and low optical absorption is critical for ensuring detector sensitivity and stable cryogenic operation. At the Materials for Advanced Detectors (MAD) workshop, that held in October at IKZ (Berlin) these challenges will be discussed extensively, with particular focus on crystalline silicon and sapphire as leading substrate candidates. Each material offers clear advantages, but also presents open questions regarding surface absorption, scattering, production, coating integration and so on. With this contribution, I will present an overview of the substrate-related discussions at MAD, highlighting the current understanding, unresolved issues, and ongoing efforts to advance mirror substrates for next-generation detectors.
Speaker: Laura Silenzi -
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Silicon optics for ETpathfinder
ETpathfinder is a testbed for interferometry at cryogenic temperatures. Following the design of ET-LF, ETpathfinder's arm cavities will consist of silicon mirrors at an operating temperature of around 18K. In our field, silicon is a new material for high-precision, low-loss optics, with many open questions on material properties and manufacturing capabilities. Here we will give an overview of the current state of our silicon mirrors, the measurements performed, and the lessons that we have learned on the way.
Speaker: Sebastian Steinlechner -
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Squeezing Working Group Status
In this presentation we will present an overview of the status of the squeezing subsystem from the squeezing source to its injection into the interferometer, including the filter cavities and the control strategy.
This presentation will be based on the work inside the squeezing working group, the task force and the preparation of the TDR. It will include discussion on R&D developments on-going, foreseen or missing for this subsystem.Speaker: Angélique Lartaux (IJCLab) -
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Straylight suppression with tunable coherence in a power-recycled Michelson at 10 Hz
As straylight is an important limitation for the sensitivity of gravitational wave detectors, we investigate new laser operation concepts and interferometer topologies for a more straylight-resilient detector configuration.
Our focus is the use of tunable coherence realized by phase modulation following a pseudo-random-noise (PRN)-sequence on the interferometer laser. This breaks the coherence of the delayed straylight reducing its intrusive impact with the remaining coherence length only depending on the PRN frequency. Thus, effectively realizing a pseudo white-light interferometer with tunable coherence length.
After successful demonstration in a Michelson interferometer and optical cavity, we now optimized our setup of a power-recycled Michelson interferometer. With this, we present successful suppression of straylight by more than 50 dB at 10 Hz. Further, relying on the resonant enhancement inside a cavity, we demonstrate the reduction of coherence length down to the wavelength scale by using a PRN frequency of up to 10 GHz.
Combining these results, we discuss what constrains a potential implementation for straylight reduction in the Einstein Telescope.Speaker: Daniel Voigt
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Observational Science (OSB): Update from divisions & OSB roadmapConveners: Archisman Ghosh (Universiteit Gent), Marica Branchesi, Michele Maggiore
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Div 2 updateSpeakers: Angelo Ricciardone, Riccardo Sturani
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Div 4 updateSpeaker: Giancarlo Ghirlanda (Istituto Nazionale di Astrofisica - Osservatorio di Brera & INFN sezione di Milano Bicocca)
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Div 5 updateSpeaker: B.S. Sathyaprakash
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Div 10 updateSpeakers: Anuradha Samajdar, Prof. Gianluca Maria Guidi, Justin Janquart, Tito Dal Canton (IJCLab)
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OSB @ ET Program + ESO whitepapersSpeaker: Marica Branchesi
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Site Preparation & Characterization (SCB)Conveners: Andreas Rietbrock, Domenico D'Urso, Dr Wim Walk (Nikhef)
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Introduction to SCB session and general update for EMR siteSpeaker: Dr Wim Walk (Nikhef)
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Update on geology and optimisation of triangle positioning in the ET-EMR region.Speaker: Dr Hannes Claes et al. (KU Leuven)
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New geological and hydrogeological insights from public tender investigations at Sos Enattos for the Einstein Telescope configurations L and T.
Recent deliverables from RockSoil S.p.A. have significantly advanced our geological and hydrogeological understanding of the Sos Enattos area, which is being considered as a potential location for the Einstein Telescope (ET). The dataset includes results from eleven deep boreholes, geophysical surveys (ERT and SRT) and magnetometry and radon gas measurements. These results have been integrated across both the L-shaped and triangular (T) configurations of the underground infrastructure.
The geological framework, supported by detailed cartographic outputs at a scale of 1:10,000 and stratigraphic logs of unparalleled detail, is consistent with previous boreholes drilled in the area and confirms the predominance of Palaeozoic crystalline basement units (granites, gneisses, micaschists and phyllites) in the projected tunnel areas. Both fieldwork and subsurface exploration support the idea that localised brittle fault zones of limited extension influence both lithological variability and geomechanical behaviour. While the regional model aligns with prior knowledge, new fault-related features and small-scale heterogeneities have been identified.
Hydrogeological analyses based on 54 Lugeon tests and flow modelling reveal low primary porosity and fracture-controlled permeability. Estimated drainage rates differ between configurations, with higher cumulative flows in the L setup (80–100 L/s) than in the T setup (60–75 L/s). However, the current piezometric network, which is limited to deep filters, restricts the vertical resolution of hydraulic gradients and potential interactions with shallow water resources.
These findings provide a robust basis for pre-feasibility assessments and future 3D geological modelling. Nevertheless, additional shallow investigations, multi-level piezometry and hydraulic testing are critical to fully characterising subsurface conditions and optimising design parameters for the ET infrastructure.Speaker: Dr Giovanni Luca Cardello (Università degli Studi di Sassari) -
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Groundwater modelling for the EMR region Einstein Telescope facility: Geological and hydro(geo)logical refinements to resolve surface drawdown and tunnel inflows using FEFLOW models
Comprehensive hydrogeological and groundwater modelling studies are underway to assess feasibility of the construction of the Einstein Telescope (ET) facility in the Euregion Meuse-Rhine (EMR) region. The facility includes ~30 km tunnels with 10 m of width arranged in a triangular shape, and shafts and cavern structures in the corners. The construction and operation of this facility will require dewatering altering groundwater flow in the surrounding and shallow aquifers, where groundwater level drawdowns and baseflow loss are expected.
To understand the impacts of this proposed facility on drawdown and baseflow, we develop and refine geological and hydrogeological understanding through models. Using these models, we improve existing predictions and support the design of the facility and mitigation of hydro-environmental impacts.
The geology of the EMR region is complex; characterized by a highly fractured rock geology, faulted subsurface, and changing stratigraphy across the proposed tunnel site. For that reason, the geological model has been updated with new drilling data and packer tests. From the gathered data, the software Leapfrog have been selected to build a complex regional geological model to represent the geological context as well as to be refined with new borehole data in order be as accurate as possible and export this data to a groundwater flow simulation software.
To numerically evaluate this situation, we used FEFLOW to build groundwater models based on the Leapfrog model data. We represent fractures and conductivity based on hydrogeological units, and the most recent tunnel location and cavern geometry. To generate our models, we emphasize local refinement of geology and hydraulic conductivity around the triangle corners in order to assess drawdowns and tunnel drainage accurately. At the tunnel boundary, we consider a 1st type pressure boundary condition (set to atmospheric pressure) and flow is inhibited by the conductivity of the grouting layer. Tunnel engineers for the site suggest an inflow of 10L/100m/min at the tunnels and 50L/100m/min at the caverns. Previous models have calculated acceptable scenarios based on grouting conductivities ranging between 5 * 10-10 m/s (3800m3/d total drainage) and 1 10-10 m/s (776 m3/d). Conceptual geological and parameter permeability uncertainty is included in the analysis of results. Hydraulic conductivity geometric mean values obtained from at the different boreholes from packer tests range from 6.010-06 m/s to 3.1 * 10-09 m/s and expected grouting conductivity in the tunnels range from 1.0*10-09 to 1.0 * 10-10 m/s.
Overall, and considering previous models and new updated data, results are consistent and our work demonstrate how modelling tools like FEFLOW can provide estimations and solutions for drawdowns expected because of the tunnel. Information generated from this task will inform the ET project bid and mitigation strategies such as grouting, water reuse or management aquifer recharge (MAR) solutions.Speakers: Dwight Baldwin (Vrije Universiteit Brussel), Alberto Roman Gessa Fernandez (Vrije Universiteit Brussel), Marijke Huysmans (Vrije Universiteit Brussel) -
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EMR Field hydrogeology characterization campaignSpeaker: Philippe Orban
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Characteristics of sustainable integration of the Einstein Telescope into the distinctive landscape of EMRSpeaker: Johan Rutten MSc.
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Coffee
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Instrument Science (ISB): ISB - Contributed talksConveners: Jan Harms, Stefan Hild
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Cryogenics research in ETpathfinder
In preparation for Einstein telescope, strategies to cool down the cryogenic payloads and cryotraps without introducing excess technical noise need to be developed and validated. A viable, ultra-low vibrational-noise strategy is to employ sorption coolers for low temperatures and sub-cooled liquid Nitrogen for intermediate temperatures. This technology is chosen in ETpathfinder. We will present aspects of this technology, describe how it is being implemented in ETpathfinder and sketch the roadmap to scale up and reach technical readiness level 9 for Einstein Telescope.
Speaker: Dr Michiel van Limbeek (University Twente) -
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Vacuum chambers, Outgassing, and Cryogenic Pumping in the Vacuum System of ET
The Einstein Telescope (ET) will be the first third-generation gravitational wave observatory, requiring an underground vacuum system of unprecedented scale. The system will comprise more than 60 large unbaked chambers (“towers”), spanning ∼10^5 m² of surface area and a volume of ∼10^4 m³. Achieving and maintaining the required vacuum levels presents a unique challenge: ET must reach pressures in the low 10^–9 mbar range in many room temperature towers while accommodating large gas loads, extensive use of high-outgassing materials and not degrade the long arms' vacuum (low 10^-10 mbar range).
This contribution presents ongoing work on the design of several types of tower chambers and integrated vacuum system, addressing outgassing issues, materials selection and characterization, and the use of cryogenic pumping as both an necessity for cooled optics, but also for an effective vacuum solution.
The scale and complexity of the project necessitate a departure from traditional laboratory approaches, requiring an industrial-level strategy to ensure both technical feasibility and cost effectiveness.Speaker: Julien Gargiulo -
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Environmental noise characterization of cryogenic facilities at CERN and UTokyoSpeaker: Matteo Di Giovanni
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Discussion of ET detector pre-TDRSpeakers: Jan Harms, Stefan Hild
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Observational Science (OSB): Divs 1, 2 contributionsConveners: Archisman Ghosh (Universiteit Gent), Marica Branchesi, Michele Maggiore
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Beyond GR tests with Einstein Telescope
Gravitational waves from compact binary coalescences (CBCs) have become a robust and powerful tool for testing General Relativity (GR), in fact, to date, the LIGO-Virgo-KAGRA collaboration has provided significant consistency tests of GR.
In this talk, I will present forecasts for the precision with which GR can be tested using third-generation interferometers, such as the Einstein Telescope. The anticipated large number of detected sources makes full Bayesian analyses computationally infeasible. To address this, we employ the newly released GWJulia code, which enables studies of large CBC populations using the Fisher information formalism.
Using this framework, we explore the constraints the Einstein Telescope could place on post-Newtonian (PN) coefficients within a hierarchical Bayesian approach. In addition, we will discuss the number of events required to identify deviations from GR at various PN orders and under different detector configurations.Speaker: Andrea Begnoni -
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Spin-induced quadrupole moment test for eccentric compact binaries
Testing the binary black hole nature of compact binaries relies on the “no-hair” conjecture, which posits that a Kerr black hole's properties are fully characterized by its mass and spin. This conjecture underpins tests applied to circular compact binaries detected by gravitational wave (GW) detectors, where the quadrupole moment depends solely on mass and spin. In contrast, exotic compact objects may require additional parameters, such as the equation of state, encoded in spin-induced quadrupole moments. Extending previous tests to binaries on eccentric orbits, we use Fisher matrix analysis to quantify parameter uncertainties and assess eccentricity's impact. Next-generation detectors like the Einstein Telescope and Cosmic Explorer, with their enhanced low-frequency sensitivity, will make these tests more powerful, allowing for tighter constraints on higher-order multipole moments.
Speaker: Syed Naqvi -
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Detection prospects of parity-violating gravitational waves in third-generation ground detectors
We investigate the prospects for detecting a parity-violating gravitational-wave background with third-generation ground-based detector networks through an adapted theoretical approach combined with a data-based approach. We focus on a variety of networks consisting of an Einstein Telescope and two Cosmic Explorer detectors, varying the Einstein Telescope design, detector locations, orientations, and arm lengths to assess the impact of geometry and scale on detection capabilities. We show that the modified theoretical approach is an excellent proxy for parity violation detection and matches more robust data analysis strategies. We demonstrate that networks with an L-shaped Einstein Telescope design have stronger parity violation constraining power than networks with a triangular Einstein Telescope design, particularly seen when studying Einstein Telescope designs on their own. Our results underscore the critical role of detector configuration in probing parity violation in a gravitational-wave background.
Speaker: Hannah Duval -
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Multi-probe Cosmology with Standard Sirens: a GWxHI Cross-correlation Approach
Multi-probe techniques have proven to be powerful tools in modern cosmology.
By breaking degeneracies, they provide new ways to gain insights into the large-scale structure (LSS) of the Universe and its evolution.In this talk, we explore the potential of cross-correlation between gravitational waves (GWs) and 21 cm intensity mapping from neutral hydrogen emission (HI), focusing on its role in view of future high-precision observatories, specifically Einstein Telescope (ET) and the Square Kilometer Array Observatory (SKAO).
Assuming that GW and HI are different tracers of the same underlying dark matter density field, we infer cosmological parameters from both the angular power spectrum (auto-correlation) and the angular cross-power spectrum (cross-correlation) of these probes.
We show that synergies between future GW and HI experiments will significantly improve standard-sirens measurements, thanks to increased sensitivity and high-redshift coverage, allowing us to constrain cosmological parameters to a level comparable to that of well-established alternative probes.Speaker: Matteo Schulz (Gran Sasso Science Institute) -
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From Astrophysics to Cosmology: forecasting Einstein Telescope's potential with improved merger rate models for spectral siren methods
The persistence of the Hubble tension requires new validation methods. While gravitational waves provide a promising solution, the rarity of standard sirens has forced to rely on dark sirens and as such, a wealth of dark sirens methods have been developed.
In this talk we will explore our new state-of-the-art models for binary black hole (BBH) merger rates and their applications to spectral siren methods for the Einstein Telescope (ET) era.
First, we will begin with a detailed look at the astrophysical modeling and its key aspects for the evolution of the merger rate: the role of star formation history and the results from population synthesis simulations. Building on this, we will then present projected number counts and conduct a comparative analysis for different proposed design configurations for the ET.
Finally, we will showcase forecast results demonstrating the cosmological and astrophysical constraints achievable through BBH number counts alone; and then we will outline a tentative approach for a complete spectral siren method, by constructing semi-parametric mass models with redshift evolution coming naturally from our merger rate formalism.
Speaker: Giovanni Antinozzi
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Site Preparation & Characterization (SCB): SCBConveners: Andreas Rietbrock, Domenico D'Urso, Dr Wim Walk (Nikhef)
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Developing a Comprehensive Digital Framework for Sustainable ET Design: A Prototype for the Sardinia site
The Einstein Telescope (ET) research infrastructure is set to become the pioneering next-generation underground observatory for gravitational wave detection.
ET engineering design demands a multi-criteria approach to identify and address geological, geotechnical, environmental, and landscape challenges. To address these complexities, a Design Digital Twin (DDT) is being developed as a dynamic, data-driven platform that seamlessly integrates Building Information Modelling (BIM), GIS datasets, and multidisciplinary simulations. This comprehensive and federated system facilitates scenario analysis, optimizes tunnel alignment, and enhances cross-disciplinary coordination, while effectively mitigating risks and promoting sustainable design solutions in construction sites.
A crucial component of the DDT is the 3D surface and underground models integrated with the structural engineering models. To characterize the underground setting, stratigraphic, geotechnical, and hydrogeological investigations can support accurate subsurface characterization by defining engineering geological units with consistent lithological and mechanical properties. The integration of these datasets into the DDT ensures that geological uncertainty and geotechnical variability are explicitly addressed, improving risk evaluation and contributing to resilient and sustainable infrastructure planning.
As part of the initiatives launched under the ETIC PNNR project, the ET-3G Lab at Sapienza University of Rome—a research laboratory specializing in 3D engineering modeling—has developed a multidisciplinary framework. This innovative environment supports workflows and tools for ET Digital Twin (ET-DT) enrichment through the integration of GIS and BIM systems, combined with advanced computational multi-criteria analysis. These efforts will play a fundamental role in refining and validating methodologies embedded within the Digital Twin (DT) framework, thereby contributing to the advancement of research infrastructure development.
By anticipating the integration of increasingly accessible datasets into digital twin technologies, this study aims to showcase how comprehensive approaches can enhance ET’s sustainable design while laying the groundwork for future Construction and Operational Twins.Speaker: Francesca Scipione (Sapienza Università di Roma) -
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Probing the quiet site: multidisciplinary characterization at Sos Enattos for the Einstein Telescope
The Sos Enattos site in Sardinia remains a key location for multidisciplinary research activities in support of the development of the Einstein Telescope (ET), a next-generation gravitational wave observatory. Current efforts include deploying advanced seismic, magnetic and environmental sensor arrays at various depths to enable long-term monitoring of site stability and noise levels. Complementary studies in geology, hydrology and rock mechanics are also being conducted to improve our understanding of the underground environment, as well as engineering and geotechnical investigations. This presentation will outline recent findings from site characterisation campaigns.
Speaker: Andrea Contu (INFN Cagliari) -
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Results of the 2025 active seismic campaign at the EMR-site
Taking the experience from the 2022 drilling and seismic acquisition campaign on board the subsurface team of the EMR-regions devised a second data acquisition program that was executed from Q2 2024 to Q1 2025. The purpose of the campaign was to enable the construction of a 3D integrated subsurface model in support of civil engineering, and hydrogeological as well as seismic noise modelling.
As part of the drilling campaign four wells at potential corner points of the ET-triangle were newly instrumented with optical fiber for digital strain, temperature, and acoustic sensing (DAS). During the active campaign the DAS-fiber were used to acquire vertical-seismic-profiles (VSP’s), simultaneously with the acquisition of 2D seismic lines that connect prospective corner-points. In total some 95km of 2D data and 5 VSP’s were acquired.
The 2D surface seismic was acquired with a 4m source and receiver spacing, which allowed just an adequate sampling of the seismic wavefield. In contrast to conventional acquisition design not a group of vibrators but only one single vibrator was used. This avoided the interference noise that occurs when using multiple vibrators at the same time and likely contributes to the improved near surface image. To reduce the environmental impact and being allowed to enter ecologically sensitive areas an electrical vibrator was employed. It operated reliably between 2-120Hz at 7000N. As geophones 1-component nodes with a frequency range of 1-125Hz were deployed, to at least a maximum offset of 1200m. For the VSP’s the vertical sampling was set at 8m being a compromise between obtaining a sufficient signal-to-noise ratio and an acceptable vertical resolution. The source spacing was again 4m.
The first round of seismic processing of the 2D surface lines and VSP’s has just been finalized. The results show an improved near surface image, which is relatively consistent across the lines and agrees reasonably well with the borehole data. The check-shot velocities obtained from the VSP data correspond in a number of boreholes with the obtained sonic logs and can be used for the time-to-depth conversion of the surface seismic. The first arrivals of the VSP data can also be used to obtain attenuation profiles, which will be useful for realistic seismic noise modelling.Speaker: Michael Kiehn -
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Seismic array measurements in the Italian candidate site for the Einstein Telescope, the third-generation gravitational wave detector
The characterization of local seismic noise is of paramount importance for evaluating candidate locations for hosting the Einstein Telescope (ET), the third-generation gravitational wave detector. Three temporary seismic arrays were installed at the Italian candidate site for ET, each with different geometrical layouts, recording durations, and total numbers of stations. Here, we provide an overview on the noise characteristics and its azimuthal distribution, obtained through beamforming analysis. Moreover, we leverage the noise recordings to extract (i) Rayleigh wave dispersion curves using FK-analysis, which are then inverted to obtain a one-dimensional, shear-wave velocity model of the subsurface and (ii) HVSR spectra across all arrays' stations. The recordings confirm the exceptionally low level of seismic noise approaching Peterson's New Low Noise Model for frequencies >1 Hz. The arrays allowed to reliably reconstruct the seismic wavefield in the 10-20 Hz range, showing an almost azimuthally homogeneous noise source distribution, with slowness values between 0.4 and 0.5 s/km. The inversion of dispersion curves in the same frequency range highlighted a rather homogeneous, high-velocity terrain (V_S=2-3 km/s) in the first $100$ m. The flat HVSR spectra across all arrays excludes the presence of a resonant, low-velocity layer at shallow depth.
Speaker: Dr Marco Olivieri (Istituto Nazionale di Geofisica e Vulcanologia) -
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Infrasound monitoring system for characterizing the candidate sites of third-generation terrestrial interferometric gravitational-wave detectors
Third-generation terrestrial gravitational-wave detectors, such as the Einstein Telescope and Cosmic Explorer, would offer significantly greater sensitivity and a wider frequency range than existing detectors. Third-generation detectors are designed to be able to detect gravitational waves below 10 Hz. In this frequency range, seismic noise and gravitational gradient noise (also known as Newtonian noise) limit the measurement range of the Einstein Telescope and Cosmic Explorer. The main contributors of Newtonian noise are seismic disturbances, but changes in air density caused by infrasound waves must also be taken into account as a potential sensitivity limiting factor. Therefore, when characterizing potential installation sites for detectors, environmental infrasound must be examined alongside other types of noise, such as seismic and electromagnetic noise. Long-term measurements are necessary to understand changes in infrasonic noise: during the day and at night, on weekdays and weekends, and throughout the changing seasons. Infrasound monitoring systems used for this purpose must be weatherproof and have adequate wind protection. Without wind protection, pressure changes caused by turbulence can override the infrasound.
In my presentation, I will introduce an infrasound monitoring system designed for site characterization measurements of third-generation gravitational-wave detectors. The system was developed by two institutes of the Hungarian Research Network, ATOMKI and Wigner Research Centre for Physics. ATOMKI microphones have already monitored infrasound at the following underground locations: Mátra Gravitational and Geophysical Laboratory (MGGL, Gyöngyösoroszi, Hungary), Sos Enattos mine (Lula, Sardinia, Italy), which is one of the candidate sites for the future Einstein Telescope. One microphone is part of the environmental monitoring system at the VIRGO gravitational-wave detector (Cascina, Italy) . Now the microphones have the protection needed for field measurements.Speaker: Edit Fenyvesi (Wigner RCP) -
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Ground Motion Analysis for the Einstein Telescope: ShakeMap, Seismic Hazard, and Case Studies
The Einstein Telescope (ET) project, a significant leap in gravitational wave observatories, demands an exceptionally stable environment to minimise seismic noise. To ensure the most suitable site selection, we conducted a meticulous ground motion analysis, integrating historical and recent instrumental earthquakes relevant to the area. By utilising ShakeMaps and severe ground motion measurements (e.g., Peak ground acceleration, Peak spectral acceleration at several periods), we were able to parameterise key seismic events and evaluate expected shaking patterns in a comprehensive manner.
We analysed scenarios including historical relevant earthquakes at Euro-Mediterranean scale. By comparing estimated shaking levels with European seismic hazard models, we provide a comprehensive overview of the expected ground motion at the site. These findings, which contribute to a refined understanding of site suitability for ET, are of utmost importance in ensuring optimal conditions both for the future gravitational wave observations and the long-term operativity of ET infrastructure and its duty cycle.Speaker: Marco Olivieri
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ECR Social Event
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ET e-Infrastructure Board (EIB)Conveners: Patrice Verdier (IP2I Lyon - IN2P3), Stefano Bagnasco
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EIB status & updates from the divisionsSpeakers: Patrice Verdier (IP2I Lyon - IN2P3), Stefano Bagnasco
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Computing Model (ET-PP D8.2) statusSpeaker: Paul Laycock
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MADDEN & ETAP projects status report
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Status of the Rucio test setup and the cluster for Technology Tracking.
The Einstein Telescope will be able to observe a sky volume one thousand times larger than the second generation observatories and this will be reflected in a higher observation rate. The physics information contained in the strain time series will increase, while on the machine side the size of the raw data from the interferometers will scale with the number and the complexity of the detectors. To meet ET specific computing needs, an adequate choice of the technologies, the tools and the framework to handle the collected data, share them among the interested users and enable their offline analysis is mandatory.
The solution currently under test for the data management and distribution is based on Rucio and on the concept of Data Lake. Rucio is a tool originally developed in the high energy physics domain and now used by many HEP and non-HEP experiments. This talk will report on the status of the test setup in place for ET and on the development of a multi-Research Infrastructure access to the data, in view of the co-operation with the Cosmic Explorer. On the computing side, since ET is expected to begin the data taking in no less than ten years, it is crucial to keep up with the technology that is always improving and to test the new architectures which gradually become available. A computing cluster dedicated to Technology Tracking is under construction in the scope of the ETIC project: in this talk an update on the status of this deployment will be given.Speaker: Lia Lavezzi (INFN Torino) -
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Building a Virtual Research Environment for the Einstein Telescope Bologna Site
The Einstein Telescope (ET) is a next-generation, underground gravitational-wave observatory designed to explore the Universe across its cosmic history. Its ambitious scientific goals, ranging from probing black-hole physics and neutron-star matter to investigating dark energy and the early Universe, require a new generation of computational
and data-analysis infrastructures. Our contribution consists in the development of a Virtual Research Environment (VRE) for the ET Bologna site, aimed at enabling collaborative, high-performance, and reproducible research within the ET community.
The ET Bologna VRE builds upon the BETIF/DIFAET computing infrastructure, adopting a modular architecture based on widely used open-source technologies such as Docker, Kubernetes, Jupyter, and Rucio/Reana developed at CERN. This design allows users to perform both interactive analyses and large-scale computations within an orchestrated and
containerized environment. The system is fully customizable, supporting multiple software stacks through CERN Virtual Machine File System (CVMFS) and providing seamless integration with external Rucio Storage Elements for distributed data management.
Authentication and authorization are managed via Indigo-IAM, ensuring compliance with the ET federation’s identity and access policies.
The platform supports heterogeneous computing resources, including CPU and
GPU-accelerated environments, and offers a range of virtual configurations that can scale according to workload and user needs within the available hardware. Through its Python-friendly interface and integration with scientific frameworks, the VRE lowers the entry barrier for analysis development while ensuring portability and reproducibility of workflows
across the collaboration.
Beyond its immediate use for data analysis and algorithm prototyping, the ET Bologna VRE serves as a testbed for future computational strategies within the broader Einstein Telescope project. It demonstrates how local resources can be orchestrated into a flexible, cloud-native environment, paving the way for a distributed data analysis model that will be crucial during ET’s construction and operational phases. This work contributes to the establishment of a sustainable, collaborative computational ecosystem for the next era of gravitational-wave astronomy.Speaker: Stefano Dal Pra (INFN-CNAF) -
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Towards a Sustainable ET Computing Center
Minimizing environmental impact is essential for the Einstein Telescope, both as a societal responsibility and to meet the expectations of funding agencies. Computing will account for a significant share of operational energy use and is therefore a key focus. We are developing a concept for a climate-neutral ET computing center that uses intelligent workload scheduling to align load with periods of high renewable energy availability, on-site energy production and storage, and waste heat reuse. These measures aim to enable fully climate-neutral operation and extend hardware lifecycles to reduce production impact. To test these concepts in practice, we plan to deploy a transportable, shipping-container-sized prototype.
Speaker: Stefan Krischer (RWTH Aachen University) -
55
Encapsulating Textual Contents into a MOC data Structure for Advanced Applications
The recent article published in Astronomy and Computing, Encapsulating Textual Contents into a MOC data Structure for Advanced Applications, introduces the first steps toward preliminary standards for Generative Artificial Intelligence within the Virtual Observatory framework.
In this talk, we will present the main concepts of the work, focusing on how to design agentic workflows in the era of multimessenger astronomy, highlighting the role of ET in enabling low-latency operations.Speaker: Giuseppe Greco
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ET-PP WP4&9Convener: maria marsella (Sapienza University, Rome)
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Instrument Science (ISB): ISB - businessConveners: Jan Harms, Stefan Hild
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Observational Science (OSB): OSBConveners: Archisman Ghosh (Universiteit Gent), Marica Branchesi, Michele Maggiore
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56
Population Properties of Binary Black Holes from Star Clusters and Active Galactic Nuclei
Disentangling the astrophysical origins of gravitational waves requires confronting population properties of observed source catalogs with theoretical predictions. We investigate the formation of merging binary black holes in two distinct environments: stellar clusters and active galactic nuclei (AGNs). In clusters, repeated three-body interactions determine the dynamical assembly of binaries. Using binary population synthesis combined with post-Newtonian N-body simulations, we quantify the occurrence of highly eccentric mergers in the LVK and Einstein Telescope bands, identifying them as potential diagnostics of the cluster channel. In AGNs, we model the migration of stellar-mass black holes embedded in gaseous disks. We map the regions of parameter space where single–single encounters can occur, leading to binary formation, versus regimes where black hole pairs are trapped in mean-motion resonances, suppressing binary assembly.
Speaker: Alessandro Trani -
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Probing increasingly younger neutron stars through continuous gravitational waves with higher-order spin-down parameters.
Wide-band searches for continuous gravitational waves are essential to reveal unknown neutron stars without an electromagnetic counterpart. Such searches, however, cover a huge parameter space that makes them computationally bounded. Neutron stars are predicted to slow down their rotation by losing energy through a variety of physical mechanisms, including, e.g, electromagnetic and gravitational-wave emission. The simplest possible model describes neutron stars slowing down at a constant rate by a first-order spin-down parameter that, for one-year long observing runs, is expected by neutron stars thousands or more years old. In this talk I will show that, to exploit the improved sentitivity of Einstein Telescope at low frequencies and the many-years long runs, there is the need to enlarge the parameter space to higher-order spin-down terms. I will show that in this way we can broaden the search to younger neutron stars, up to hundreds of years old or less, and discuss a possible implementation of a search including this extended model.
Speaker: Lorenzo Pierini (Istituto Nazionale di Fisica Nucleare) -
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Gravitational wave properties of the HESS J1731-347 Object as a Twin Compact Star
In this work we present the properties of gravitational waves emitted from the f-mode oscillation of a compact star corresponding to the Object HESS J1731-347 as a Twin Compact Star, a hybrid neutron star with the same mass as a larger, purely hadronic neutron star. HESS J1731-347 is a peculiar object due to its reported compactness consisting of a mass of 0.77 solar masses and a radius of 10.4 km. Gravitational waves carry information of the damping time of the f-mode and are thought to be associated with pulsar glitches, thus providing the possibility of an upcoming multi-messenger observation performed by future gravitational waves observatories like the Einstein Telescope or the Cosmic Explorer.
Speaker: Dr David Alvarez Castillo (Institute of Nuclear Physics Polish Academy of Sciences) -
59
An incremental approach for all-sky searches for continuous gravitational wave signals
All-sky searches for continuous gravitational wave signals, like those expected from asymmetric rotating neutron stars, require to analyse long stretches of data in order to increase the signal-to-noise ratio.
Typically, the heavy processing part starts after all the data to be analysed have been collected. Such a strategy is sub-optimal from a computational perspective and can significantly delay in the dissemination of results. This will be a very relevant problem for third generation detectors, like ET, due to the expected long data taking periods and the anticipated large overall computing cost of the analyses.
Analysing the data as long as they are produced, on the other hand, is not feasible without a careful algorithmic design, due to the huge amount of disk space it would be needed to store the intermediate products.
In this talk we introduce a promising implementation of an incremental search (based on the Frequency-Hough transform pipeline), which allows us to pile up the analysis intermediate products with a reasonable storage burden, and with a very small or null sensitivity loss with respect to the standard non-incremental approach. This allows to better distribute the available computing power making the analysis faster, more robust with respect to possible temporary shortages of computing resources or malfunctions of relevant services and, possibly, opening the way toward more sensitive searches.Speaker: Cristiano Palomba -
60
Recent results on the high-energy emission from GRB jets
The detection of gravitational waves associated with short GRBs and
observations of the TeV photons from very energetic events were the
main breakthroughs in the gamma-ray burst field in past few years. I will
discuss the recent multi-wavelength observations and theoretical progress
in modelling of prompt GRB emission, including the lepto-hadronic emission
model and the model for VHE gamma-rays from a structured jet, similar to
GW170817/GRB 170817A when viewed off-axis.Speaker: Prof. Zeljka Bosnjak (FER) -
61
Test of a deep anomaly detection algorithm using MDC1
We present the implementation, testing, and results of an anomaly detection pipeline based on convolutional autoencoders. After testing on white noise, we proceed to a test using MDC 1 focusing on mergers involving IMBHs and provide the results.
Speaker: Dr Huw Haigh (MBI Vienna)
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56
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Coffee
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CommunicationsConvener: Prof. Dorota Rosinska (University of Warsaw)
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IntroductionSpeaker: Prof. Dorota Rosinska (University of Warsaw)
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63
ET-PP project: building framework for ET supranational communication
The presentation will highlight recent achievements within WP 10 of the Einstein Telescope Preparatory Phase (ET-PP), covering communication, education, and citizen engagement. It will focus on recent deliverables, updates in social media and website activities, and the development of outreach materials and resources within the shared communication repository.
Speakers: Prof. Dorota Rosinska (University of Warsaw), Yuliya Hoika (University of Warsaw) -
64
ET EMR: Updates on Communication activities.
Einstein Telescope: much more than a scientific project!
And in the field of communication in het EMR-project: need to know and nice to know, four languages, but one voice. And customised solutions where necessary.Speaker: Henk Schroen (Nikef) -
65
ET Italy: updates on communication and public engagement activities
ET Italy: updates on communication and public engagement activities
In this talk we present the latest updates on the communication activities underway to promote Italy's candidacy to host the Einstein Telescope. These activities range from institutional communication to the organization of local, national and international events, as well as media relations and public engagement initiatives.Speaker: Matteo Serra -
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Ten Years of Gravitational Waves: Educational Tools for the New GenerationsSpeakers: Giuseppe Greco, Matteo Tuveri (Università di Cagliari e INFN Cagliari), simone mastrogiovanni
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62
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Instrument Science (ISB): ISB + ETOConveners: Benoît Tuybens (Nikhef), Jan Harms, Stefan Hild
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PBS update and the configuration databaseSpeakers: Alessandro Variola (Istituto Nazionale di Fisica Nucleare), Fiodor Sorrentino, oussama EL MECHERFI
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Model Based System Engineering hands-onSpeakers: Frederik Moers (MSE, RWTH Aachen), Romano Meijer (Nikhef)
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67
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Observational Science (OSB): OSB + EIBConveners: Archisman Ghosh (Universiteit Gent), Marica Branchesi, Michele Maggiore
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70
QTAM: Qtransform from visualization to physicsSpeakers: Francesco Sarandrea (INFN Torino), Lorenzo Asprea
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71
Discussion: resource evaluationSpeaker: Gonzalo Merino
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MDC discussion
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70
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Site Preparation & Characterization (SCB)Conveners: Andreas Rietbrock, Domenico D'Urso, Dr Wim Walk (Nikhef)
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73
Newtonian Noise in non-spherical cavernsSpeaker: Dr Valentin Tempel (RWTH)
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Towards an improved analytical framework and interpretation of seismic data for understanding Newtonian NoiseSpeaker: Dr Stan Bentvelsen (Nikhef)
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Estimating Newtonian Noise in complex media based on 2D/3D seismic wavefield simulationsSpeaker: Dr Andreas Rietbrock
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Assessment of seismic noise induced by Next-Generation Wind Turbines in the Fulgatore Area, NW Sicily
The detection of gravitational waves with large-scale laser interferometers such as LIGO and VIRGO has opened a new era in physics, and the scientific community is now planning to build the Einstein Telescope (ET), a next-generation detector with significantly higher sensitivity. These instruments are highly sensitive to seismic noise from natural and anthropogenic sources. In particular, the seismic noise generated by wind turbines may have a pernicious effect on gravitational waves detectors. Understanding the implications of the seismic noise generated by wind farms is crucial for mitigating the potential impact that this source of noise poses on their operational performance. For this reason, one of the candidate site to host the ET is located in Sardinia (Italy), one of the quietest seismic sites worldwide. However in this are next-generation wind turbines might be installed in the near future, hence assessing their impact in terms of seismic noise is essential.
To assess the potential impact of next-generation wind farms on the potential ET site, we analyzed the seismic noise generated by a new class of wind turbines (taller and heavier than older models) operating at Fulgatore (TP), Sicily. A one-month seismic acquisition was carried out using six broadband three-component seismometers: four installed at the base of different turbines in Fulgatore and 2 deployed at the archaeological park of Segesta, located about 12–13 km away. To correlate seismic records with wind farm activity, we used turbine operational data at 10-minute resolution provided by EDP Renewables, together with hourly wind data from SIAS. Turbine-induced seismic noise was mainly confined to the 0.1–10 Hz frequency band. For each station, power spectral densities (PSD) were computed on 10-minute waveform segments and compared with turbine operating regimes defined by rotor speed intervals. At the Fulgatore array, PSDs consistently showed narrow spectral peaks across all channels (HHZ, HHE, HHN). Spectrograms confirmed that below 2 Hz the dominant signal corresponds to the Blade Passing Frequency (BPF), ranging from 0.30 to 0.54 Hz depending on rotor speed, and its harmonics. In the 2–10 Hz band, stable peaks were observed at about 2.45 Hz and 5.25 Hz, along with an additional peak at 8.60 Hz restricted to the HHZ channel.
To investigate near-field ground motion polarization, we applied Principal Component Analysis (PCA) based on the singular value decomposition of data covariance matrices. The results indicate that the Blade Passing Frequency (BPF) and its harmonics generate predominantly linear oscillations with dips below 30°, consistent with the stronger amplitudes observed in the HHN and HHE power spectral densities. The spectral peak at 5.25 Hz exhibits linear polarization with an average incidence angle of ~60° and maximum amplitude in the HHZ channel, whereas the 8.60 Hz peak shows vertical linear polarization with dips of ~85°, explaining its exclusive presence in the HHZ spectra. Furthermore, the azimuth of the dominant polarization directions varies with the nacelle orientation, which rotates in response to changes in wind direction.
After characterizing the spectral features of the wind turbines, we extended the analysis to the Segesta site to identify correlations with the wind farm's operation. Results show that the wavefield radiated from the wind farm is attenuated and not detectable at 12–13 km under the local geological and noise conditions. During maximum turbine activity, PSD values at Segesta are approximately 40–60 dB lower than those at Fulgatore in the 2–10 Hz band. Instead, in the band below 2 Hz the difference is lower because all PSDs are affected by the secondary microseismic peak at 0.22 Hz.
Finally, we derived a source time function to represent the vertical motion of a single turbine, constructed from four sinusoids at 0.54 Hz, 1.08 Hz, 2.45 Hz, and 5.25 Hz. Each component was assigned a random phase and an amplitude estimated from RMS ground velocity statistics during maximum operational conditions. Cross-correlation analysis between station pairs at the Fulgatore array showed that phase relationships among different sources are random and exhibit no temporal coherence. Based on these findings, we employed a spectral element method together with the extracted source time function to simulate the propagation of turbine-induced seismic waves. The resulting models provide a basis for future studies at the Sardinian site, enabling predictions of wind farm–generated wavefields under realistic geological conditions.
This study has been funded by the project "PNRR ETIC IR0000004 - EINSTEIN TELESCOPE INFRASTRUCTURE CONSORTIUM” – CUP 53C21000420006 MISSIONE 4, COMPONENTE 2, INVESTIMENTO 3.1. CISUP of the University of Pisa is acknowledged for the access to the seismlogical stations and laboratory facilities.
Speaker: Roberto Fontana (University of Pisa)
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73
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Lunch
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CommunicationsConvener: Prof. Dorota Rosinska (University of Warsaw)
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Communication and knowledge transfer at the DZASpeaker: Mike Lindner (DESY - DZA)
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ECR mentorship and training programmeSpeaker: Martin Hendry (University of Glasgow)
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79
MaGIC: international educator school on GW and ET; update on first edition and next steps.
As announced in previous talks at the ET-meetings, an international summer school on teacher professionalisation was in the works: MaGIC. The first edition was held last Summer in Maastricht, hosting 25 teachers from Europe exploring together the theory of gravitational wave physics and their measurements and noise mitigation, as well as the didactics to bring this back into their classroom back home. In this talk, I will report on the 1st edition of MaGIC, its programme and the response of our participants, and lay out the next steps towards local MaGIC-initiatives, so as to create a Europe-wide network of teacher trainers.
Speaker: Gideon Koekoek -
80
Gravitational wave outreach initiatives in the EMR: current status
Throughout Europe and in the Einstein Telescope Collaboration, there exist many great initiatives to share Einstein Telescope out of academica to stakeholders in education, politics, and general public. This is a vital part of our enterprise to realise ET, and many partners are sharing their best practices, including in the EMR. In this talk, I will highlight some of these initiatives and existing collaborations, and see how they can be connected still to other projects in and outside the EMR, making sure that the best case for ET is made to the general public throughout Europe.
Speaker: Gideon Koekoek -
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Discussion
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Forum of National RepresentativesConvener: Michele Punturo (INFN)
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Instrument Science (ISB): ISB - Contributed talksConveners: Jan Harms, Stefan Hild
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82
Deep Loop Shaping: Reinforcement Learning Control for Gravitational-Wave Observatories
Improved low-frequency sensitivity of gravitational wave observatories would unlock study of intermediate-mass black hole mergers and binary black hole eccentricity and provide early warnings for multimessenger observations of binary neutron star mergers. Today’s mirror stabilization control injects harmful noise, constituting a major obstacle to sensitivity improvements. We eliminated this noise through Deep Loop Shaping, a reinforcement learning method using frequency domain rewards. We proved our methodology on the LIGO Livingston Observatory (LLO). Our controller reduced control noise in the 10-to 30-hertz band by over 30x and up to 100x in subbands, surpassing the design goal motivated by the quantum limit. These results highlight the potential of Deep Loop Shaping to improve current and future gravitational wave observatories and, more broadly, instrumentation and control systems.
Speaker: Tomislav Andric -
83
Multi-scale optimal control for Einstein Telescope active seismic isolation
We present a multi-scale optimal control framework for active seismic isolation in the Einstein Telescope, a third-generation gravitational-wave observatory. Our approach jointly optimizes feedback and blending filters in a cross-coupled opto-mechanical system using a unified cost function based on the "acausal optimum," which quantifies sensor signal-to-noise ratios across frequencies. This method enables efficient re-optimization under varying sensor configurations and environmental conditions. We apply the framework to two candidate sensing systems: OmniSens-a six-degree-of-freedom inertial isolation system-and BRS-T360, which combines Beam Rotation Sensor (BRS) as an inertial tilt sensor with T360 as a horizontal seismometer. We demonstrate superior low-frequency isolation with OmniSens, reducing platform motion by up to two orders of magnitude near the microseism. The framework allows for ready optimization and projection of sensor noise to metrics relevant to the performance of the instrument, aiding the design of the Einstein Telescope.
Speaker: Pooya Saffarieh -
84
Towards a more realistic Seismometer Position Optimization for Newtonian Noise Mitigation
At the Einstein Telescope, Newtonian noise is expected to be the dominant noise for low frequencies. Its impact is proposed to be reduced with the help of an array of seismometers that will be placed around the interferometer endpoints. As boreholes for seismometers are expensive, their positions should be optimized. Up to now, this was done based on an analytical calculation that makes simplifying assumptions.
We have developed a three-dimensional simulation of seismic body waves and their gravitational effect on an array of test masses. It also simulates the displacement measured by arbitrarily placed seismometers. With this flexible simulation, some of the limitations of the analytical calculations can be lifted. Furthermore, it enables the training of machine-learning-based mitigation techniques. First results using convolutional and graph neural networks will be shown in the presentation. This simulation provides an important link between the analytical description and complex seismic models that are currently being developed.
Speaker: Patrick Schillings (RWTH Aachen University) -
85
Double-arm suspended interferometric balance at Sos Enattos. Preliminary sensitivity
In Sos Enattos, the installation of the first double-arm suspended
balance with interferometric reading has been completed. The system
consists of a reference arm with a high moment of inertia and a
measurement arm, with low moment of inertia, suspending at one end a
lead sample and at the other end an aluminum sample. The aluminum sample is in turn. immersed in a thermal chamber to allow for temperature modulation if necessary. The system is under vacuum and properly locked to assure interferometric reading.
The control system and the balance preliminary and excellent sensitivity are shown and discussed in light of the low seismic noise at the Sos Enattos site, Sardinia. Applications in tiltmeters are also presented.Speaker: Enrico Calloni -
86
MAD workshop report on crystalline TM suspension
Crystalline materials play a key role in defining the design and the thermal and structural behavior of suspensions used for the test masses in upcoming gravitational wave interferometers that will employ cryogenic payloads. This talk will highlight the latest advancements from a collaborative research effort involving several laboratories, research centers, and private companies focused on developing cryogenic test mass suspensions capable of supporting 200 kg substrates with exceptional thermal and mechanical performance.
Speaker: Flavio Travasso -
87
Conceptual study of a 6-D active preisolator
We present the conceptual design of a six-degrees-of-freedom (6-D) active preisolator, building on the experience of the Virgo Superattenuator. The goal is to extend active control from the current three translational degrees of freedom to the full 6-D configuration, combining a mechanically optimized supporting structure with piezoelectric actuators and dedicated control strategies. The experimental validation is based on a testbench-sized Superattenuator installed at INFN Pisa. At present, this setup operates in 3-D and is used for transfer function measurements, noise characterization, and validation of numerical models. Its planned upgrade to 6-D will allow us to test the conceptual design under realistic conditions, while benchmarking the simulations against experimental data. This approach will provide a solid foundation for reliable modeling and the design of future full-scale systems.
Speaker: Francesca Spada -
88
ET-LF Sensitivity limitations from vertical thermal noise
The Low Frequency interferometer of the Einstein Telescope will use cryogenic mirror suspensions with long pendulum providing horizontal attenuation to filter out the horizontal thermal noise generated by the seismic attenuation chain and by the heat links. They will be made of crystalline materials to minimize their own thermal noise generation.
It is almost impossible to make passive springs for low-frequency vertical attenuation with the crystalline materials necessary to limit their own internal thermal noise generation. As a result, the large vertical thermal noise injected on the upper mass of the cryogenic suspensions will be directly transmitted to the mirror.
Due to Earth’s limited radius, even if the 10 km long beamlines were perfectly horizontal at the center, a minimum of 0.16% of that thermal noise will be transmitted to the interferometer direction and severely limit ET-LF sensitivity. This fraction grows significantly if the tunnels are longer and/or tilted, or if the mirror suspensions are not perfectly longitudinally symmetric.
A method to soften silicon springs using active feedback between an optical sensor and an electrostatic actuator is presented as a possible solution.Speaker: Riccardo De Salvo (California State University of Los Angeles)
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82
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Observational Science (OSB): Div 10 contributionsConveners: Archisman Ghosh (Universiteit Gent), Marica Branchesi, Michele Maggiore
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89
Fast and accurate parameter estimation of high-redshift sources with the Einstein Telescope
The Einstein Telescope (ET), along with other next-generation gravitational wave (GW) detectors, will be a key instrument for detecting GWs in the coming decades. However, analyzing the data and estimating source parameters will be challenging, especially given the large number of expected detections – of order $10^5$ per year – which makes current methods based on stochastic sampling impractical. In this work, we use Dingo-IS to perform Neural Posterior Estimation (NPE) of high-redshift events detectable with ET. NPE is a likelihood-free inference technique that leverages normalizing flows to approximate posterior distributions. After training, inference is fast, requiring only a few minutes per source, and accurate, as corrected through importance sampling and validated against standard Bayesian inference methods. To confirm previous findings on the ability to estimate parameters for high-redshift sources with ET, we compare NPE results with predictions from the Fisher information matrix (FIM) approximation. We find that NPE correctly recovers the eight degenerate sky modes induced by the triangular detector geometry, which are missed by the FIM analysis, resulting in an underestimation of sky localization uncertainties for most sources. FIM also overestimates the uncertainty in luminosity distance by a factor of $\sim 3$ on average when the injected luminosity distance is $d^{\mathrm{inj}}_{\mathrm{L}} > 10^5$ Mpc, further confirming that ET will be particularly well suited for studying the early Universe.
Speaker: Filippo Santoliquido -
90
Overlapping signals in next-generation gravitational wave observatories: A recipe for selecting the best parameter estimation technique
Third-generation gravitational wave detectors such as Einstein Telescope and Cosmic Explorer will have significantly better sensitivities than current detectors, as well as a wider frequency bandwidth. This will increase the number and duration of the observed signals, leading to many signals overlapping in time. If not adequately accounted for, this can lead to biases in parameter estimation. Our recent work combines the joint parameter estimation method with relative binning to handle full parameter inference on overlapping signals from binary black holes, including precession effects and higher-order mode content [1]. As the joint parameter estimation is computationally more expensive than traditional single-signal parameter estimation, it is crucial to devise a method to determine which method suits the problem at hand, i.e., when joint parameter estimation is necessary and when traditional single-signal parameter estimation is sufficient when analysing two overlapping signals. In an initial step, we test a time-frequency overlap method and a prior-informed Fisher matrix to help us decide when joint parameter estimation is necessary. We find the former method to be accurate in 86% of close binary black hole mergers. We improve upon previous Fisher matrix implementations by including the prior information and performing an optimization routine to better locate the maximum likelihood point point, but we still find the method unreliable. We end by developing our own method of estimating bias due overlaps, where we reweight the single signal parameter estimation posterior to quantify how much the overlapping signals affect it. We show it has 99% accuracy for zero noise injections (98% in Gaussian noise), at the cost of one additional standard sampling run when joint parameter estimation proves to be necessary.
- T. Baka et al., “Overlapping signals in next-generation gravitational wave observatories: A recipe for selecting the best parameter estimation technique,” Phys. Rev. D. (2025), arXiv:2507.10304 [gr-qc].
Speaker: Harsh Narola -
91
Hierarchical Subtraction with Neural Density Estimators as a General Solution to Overlapping Gravitational Wave Signals
Overlapping gravitational wave (GW) signals are expected in the third-generation (3G) GW detectors, leading to one of the major challenges in GW data analysis. Inference of overlapping GW sources is complicated - it has been reported that hierarchical inference with signal subtraction may amplify errors, while joint estimation, though more accurate, is computationally expensive. However, in this work, we show that hierarchical subtraction can achieve accurate results with a sufficient number of iterations, and on the other hand, neural density estimators, being able to generate posterior samples rapidly, make it possible to perform signal subtraction and inference repeatedly. We further develop likelihood-based resampling to accelerate the convergence of the iterative subtraction. Our method provides fast and accurate inference for overlapping GW signals and is highly adaptable to various source types and time separations, offering a potential general solution for overlapping GW signal analysis.
Speaker: Qian Hu -
92
Fast glitch removal method
We describe a fast glitch removal method based on the continuous wavelet transform. We give a full statistical characterization of the method and illustrate it with practical examples based on publicly available LVK data.
Speaker: Edoardo Milotti (University of Trieste and INFN-Sezione di Trieste) -
93
Bayesian Calibration of Gravitational-Wave Detectors Using Null Streams Without Waveform Assumptions
Gravitational-wave (GW) astronomy has revolutionized our understanding of the universe, but the precision of its discoveries hinges on the accurate calibration of GW detectors. In this talk, we present a novel Bayesian null-stream method for self-calibration of closed-geometry GW detector networks, such as the Einstein Telescope (ET) and LISA. Unlike traditional approaches that rely on electromagnetic counterparts or waveform models, our method leverages sky-independent null streams to constrain calibration errors using GW signals alone, independent of general relativity or waveform assumptions. We demonstrate the feasibility of this approach through proof-of-concept studies, showing that calibration constraints improve linearly with increasing signal-to-noise ratio and the presence of multiple overlapping signals. This method has the potential to enable robust parameter estimation, early-warning alerts, and cosmological studies, particularly for next-generation detectors.
Speaker: Chun-Fung Wong (KU Leuven) -
94
Fast likelihood evaluation of eccentric–precessing binaries using relative binning
As gravitational-wave detectors gain sensitivity at low frequencies, inferring source properties becomes challenging due to long-duration signals and high signal-to-noise ratios. With enhanced low-frequency sensitivity, we also expect to observe many more eccentric binaries, with potentially a large impact on our understanding of binaries. The presence of orbital eccentricity enhances the emission of GW radiation not only at twice the orbital frequency but also across a whole spectrum of integer multiples of the orbital frequency. Consequently, eccentric waveforms are complex and computationally expensive, with both effects increasing with eccentricity.
We present an efficient scheme for likelihood evaluation of eccentric–precessing signals using the relative binning method. Our approach constructs the relative binning approximation mode by mode, enabling accurate incorporation of higher harmonics enhanced in eccentric systems. We apply this method to low-mass binaries with lower cutoff frequencies of 20 Hz and 5 Hz, relevant to current and future detectors. For second-generation detectors, our method achieves speed-ups of a factor of 5–20 compared to standard frequency-domain calculations. For Einstein Telescope, the computational gain is more dramatic, with likelihood evaluations accelerated by a factor of 50–1000, while maintaining accuracy. Finally, we demonstrate that posterior distributions inferred with our method are statistically indistinguishable from those obtained with exact likelihood evaluations.
Speaker: Dr Soumen Roy (UCLouvain / Royal Observatory Belgium)
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89
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Site Preparation & Characterization (SCB)Conveners: Andreas Rietbrock, Domenico D'Urso, Dr Wim Walk (Nikhef)
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95
Low-frequency environmental noise evaluation at Sos Enattos, the Sardinian site proposed for Einstein Telescope
The Sos Enattos area in Sardinia, Italy, is one of the most promising locations for the Einstein Telescope (ET), a next-generation underground gravitational wave observatory. In this study, we present the results of a recent environmental magnetic noise analysis aimed at characterising natural noise sources in the low-frequency band. Using a network of sensors deployed in the region, we assessed the site's noise conditions, focusing on the frequency range below 10 Hz where noise has the greatest impact on the sensitivity of the ET-LF interferometer. Our findings confirm that the site consistently exhibits exceptionally low ambient noise levels. These results reinforce Sos Enattos's potential as an ET location and provide a baseline for future infrastructure planning and noise mitigation strategies. Ongoing and future work will extend this analysis to include seasonal cycles and rare transient events. This will involve correlating noise data with meteorological and marine conditions and localised human activity in order to identify the main sources of noise variability.
Speaker: Davide Rozza (University of Milano-Bicocca & INFN-MIB) -
96
Environmental Noise Monitoring with Distributed Acoustic Sensing: Insights from the WAVE Seismic Network
Distributed Acoustic Sensing (DAS) turns standard telecommunication fibers into dense seismic arrays with thousands of measurement points. Within the WAVE initiative, a 16 km fiber provides more than 16,000 virtual seismic channels in collaboration with DESY on the Bahrenfeld research campus in Hamburg. The project investigates how such large-scale DAS networks can advance environmental monitoring, geophysics, and the operation of large research facilities, especially gravitational wave detectors.
We report on the current status of the WAVE seismic network, ongoing plans to extend fiber installations into experimental halls that contain a high-precision gravitational-wave experiment with active seismic isolation, and recent results. These results include the ability of DAS to record and characterize diverse environmental noise sources, such as wind, tides, temperature variations, and anthropogenic activity like heating, ventilation, and air conditioning systems. Comparisons with conventional seismometers show that DAS achieves comparable sensitivity for the signals observed in this urban setting, underlining its potential as a scalable and cost-effective technology. Looking ahead, this work demonstrates how DAS can enable dense seismic monitoring and contribute to the cancellation of Newtonian noise. This topic will be discussed further in Paul Ophardt's presentation at the ISB ANM board.
Speaker: Mr Reinhardt Rading (Helmut-Schmidt-Universität/Universität der Bundeswehr Hamburg) -
97
Infrasound noise at Sos Enattos
I present the analysis of the infrasound measurements at the Sos Enattos mine. I discuss the correlations between different stations. Additionally I present the level of the infrasound induced newtonian noise and discuss the ways to mitigate its influence on the detector.
Speaker: Tomasz Bulik
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95
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Poster SessionConveners: Andrew Spencer, Anna Green (Nikhef), Jessica Steinlechner
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EB meetingConvener: Michele Punturo (INFN)
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Plenary: Plenary 3: ET Framework
Plenary 1: Welcome and ET Collaboration Overview
Convener: Michele Punturo (INFN)- 98
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SiSeSpeaker: Andrew Harrison
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100
Communicating the Einstein Telescope across Europe
The communication landscape of the Einstein Telescope is evolving into a dynamic European network connecting the Einstein Telescope Preparatory Phase (ETPP) project, local communication teams in Sardinia, the Euregio-Meuse-Rhine region, Lusatia, and beyond. The presentation will highlight recent supranational achievements, including the implementation of the new visual identity, the growing website as a source of stories and resources, and strengthened social media outreach. It will conclude with selected highlights from each candidate site, showcasing how local initiatives contribute to a coherent European communication effort.
Speaker: Yuliya Hoika (University of Warsaw) -
101
Research and development of crystalline suspensions for ET-LF
The Einstein Telescope will utilise cryogenic cooling in the low-frequency detector, and will therefore require crystalline materials in the suspension and optical components. The material properties of these suspension materials should not limit the thermal noise performance, requiring low mechanical loss, high thermal conductivity, and suitable tensile strength. With this, there is an increasing need for novel techniques in suspension fibre fabrication and jointing. The two main material candidates are sapphire and silicon, both of which have promising cryogenic properties, but require detailed characterisation to inform realistic thermal noise models. We report recent developments from the suspensions division in fibre production and jointing methods, and updated experimental characterisation results with the aim of producing realistic thermal noise curves for both sapphire and silicon suspensions.
Speaker: Jennifer Docherty - 102
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Coffee
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Plenary: Plenary 4: ETO
Plenary 1: Welcome and ET Collaboration Overview
Convener: Benoît Tuybens (Nikhef)- 103
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ET-COMPASS project - Contribution to Early Implementation of ET projectSpeakers: Daniela Trani, Mauro Morandin (INFN-PD)
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106
ETO Engineering Department updateSpeaker: Patrick Werneke
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Lunch
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Social Activity: Social activity + dinner
Social Activity + Dinner:
NOTE: Transport is from the conference location to the social activity, and from there directly to dinner. If you want to participate in the dinner, but not in the social activity, you have to organize your own transport.
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Plenary: Plenary 5: ET Collaboration activitie & National host teams
Plenary 1: Welcome and ET Collaboration Overview
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107
SCB common activitiesSpeakers: Domenico D'Urso, Dr Wim Walk (Nikhef)
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107
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Coffee
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Plenary: Plenary 6: ET Collaboration Activities & Conclusions
Plenary 1: Welcome and ET Collaboration Overview
Conveners: Harald Lueck, Michele Punturo (INFN)- 111
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112
OSB PlenarySpeakers: Archisman Ghosh (Universiteit Gent), Marica Branchesi, Michele Maggiore
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114
Announcement of Poster Prize Winners
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