# Second European Physical Society Conference on Gravitation: measuring gravity

Europe/Paris
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Description

The second EPS (European Physical Society) Conference on Gravitation will be held online from July 5th to July 7th , 2021. The conference was originally scheduled from April 7th to April 9th,  2020 at King's College  London (London, UK) and postponed because of the COVID-19 pandemia. This event follows  up on a previous successful conference in Rome https://agenda.infn.it/event/15395/,  with the aim  to discuss experimental aspects of Gravity, including General Relativity tests, measurements of the G constant, Geodesy, and Gravitational Waves. The conference is organised in days, each one focused around key topics introduced by invited speakers and  asynchronous contributed talks followed by round tables. The scientific program will be finalised in the upcoming days.

There is no registration fee.

Abstract submission are open  until June 30th, 2021.

The topics for Second EPS Conference on Gravitation: measuring gravity,   are:

• Experimental Challenges in Gravitational Wave Detection

• Gravity: fundamental tests and Equivalence Principle

• Geodesy and Ranging

Participation opportunities for this conference include:

• Plenary highlight talks

• Recorded talks posted in advance (asynchronous talks)

• Round tables

Participants interested in proposing contributions should submit abstracts after the registration on the Indico site of the conference.

Registration
Registration Form
Participants
• Aaron Held
• Alain Geiger
• Aldo Gamboa
• Alexander Jenkins
• Alexey Kupriyanov
• Alexis Menendez-Vazquez
• Ali Mozaffari
• Ameek Malhotra
• André Großardt
• Benliang Li
• BOILEAU Guillaume
• Carlos Martins
• Chetan Vishwakarma
• Christos Karathanasis
• Claus Laemmerzahl
• Daniele Nicolodi
• Daniele Vetrugno
• David Reitze
• David Wands
• Davide Dal Bosco
• Dimitrios Tsoulis
• Dixeena Lopez
• Dorothee Tell
• Eleanor Hamilton
• Eleonora Castelli
• Ernst Rasel
• Fabrizio De Marchi
• Federico De Lillo
• Fienga Agnes
• Florian Seemann
• Francesca Gerardi
• Fulvio Ricci
• Gabriele Perna
• Gerhard Heinzel
• Glass Veronica
• Guglielmo M. Tino
• Heiner Denker
• Helen Margolis
• Houri Ziaeepour
• Jacopo Fumagalli
• Jan Harms
• Jaspar Meister
• Jose A. Font
• Jose Agustin Lozano Torres
• João Dias
• Jürgen Müller
• Katarina Martinovic
• Konstantinos Dimopoulos
• Liliane Biskupek
• Lluïsa-Maria Mir
• Lorenzo Sala
• Luciano Di Fiore
• Luciano Iess
• Luigi Cacciapuoti
• Léo Bernus
• Léo Vacher
• Malte Misfeldt
• Manuel Rodrigues
• Marco de Cesare
• Maria Haney
• Mario Martinez
• Martin C. E. Huber
• Martin Lasser
• Martin Pernot-Borràs
• Martina Gebbe
• Matteo Barsuglia
• Matthias Weigelt
• Michael Ebersold
• Morteza Khamedi
• Mouine Abidi
• Nelson CHRISTENSEN
• Paola Puppo
• Peter Bender
• Philippe Bouyer
• Philippe Jetzer
• Pierre Grandemange
• Pieter Visser
• Quentin Baghi
• Quentin Bailey
• Raúl Carpio Fernández
• Riccardo Buscicchio
• Rita Dolesi
• Roelant van Dierendonck
• Rui Li
• Sandra Boekhoff
• Shubhanshu Tiwari
• Simone Dell'Agnello
• Stefano VITALE
• Stephan Hannig
• Sweta Shah
• Tim Lücke
• Ulrich Schreiber
• valerio ferroni
• Valeriya Kachmar
• Veronica Glass
• Vishwa Vijay Singh
• Vivek Venkatraman Krishnan
• Yumeng Xu
• Zachary Picker
Support
• Monday, 5 July
• 09:00 10:00
Welcome
• 09:30
Introductory Talk 30m
Speaker: Prof. Mairi Sakellariadou (King's College - London)
• 10:00 11:00
Experimental Challenges in Gravitational Wave Detection
Convener: Stefano Vitale (University of Trento)
• 10:00
Instrumental challenges in ground-based gravitational wave detectors 30m

Invited talk

Speaker: Matteo Barsuglia (APC-CNRS)
• 10:30
Instrumental challenges in space-based gravitational wave detectors 30m

Invited talk

Speaker: Rita Dolesi (TIFP)
• 11:00 11:30
Coffee Break 30m
• 11:30 12:30
Lunch break 1h
• 12:30 13:30
Experimental Challenges in Gravitational Wave Detection
Convener: Karsten Danzmann (AEI Hannover)
• 12:30
Large-scale atom interferometers toward observation of Gravitational Waves and more 30m
Speaker: Philippe Bouyer (Institut d'Optique d'Aquitaine - France)
• 13:00
Radio Pulsars and Relativistic Gravity 30m
Speaker: Venkatraman Krishnan (Max Plank Institute Bonn, Germany)
• 13:30 15:30
Recorded Talks: Experimental Challenges in Gravitational Wave Detection
• 13:30
Parametric Instability Observation in Advanced Virgo 10m

We present the first observation of a parametric instability event in Advanced Virgo. The event occurred on January the 2020 during the locking acquisition procedure and involves for the first time, for a long-arm interferometer, a very high frequency mechanical mode. We will describe this event and the mean adopted for its dampening.

Speaker: Paola Puppo (ROMA1)
• 13:40
Removing Schumann noise from stochastic gravitational wave data 10m

Unlike for transient signals, the stochastic searches at LIGO-Virgo have the trouble of the signal not being greater than the intrinsic noise of the detector, and one should be particularly careful when trying to extract the gravitational wave signal from the data. Correlated noise coming from the Earth's electromagnetic field, in the form of Schumann resonances, could be comparable to the sensitivity of the LIGO-Virgo gravitational wave detectors in the near future. If this is the case, the detection of a stochastic background will not be possible and it will be completely limited by the magnetic noise. In our most recent work, we model the presence of the Schumann noise and remove it from the detector data.

Speaker: Katarina Martinovic (King's College London)
• 13:50
LISA Instrumentation - interferometry and noise challenges 10m

The space based GW detector `Laser Interferometer Space Antenna' (LISA) will probe the low-frequency GW sources such as mergers between massive black holes and compact binaries among others. It will complement the existing ground based GW detectors probing the high frequency sources. LISA is an ESA mission with NASA partnership and a planned launch date in 2034. To achieve it's science goals the laser interferometry that will measure the distance variations between freely falling test-masses is required to achieve sensitivity of picometers in the given frequency range. The presentation covers an overview of the noises challenges in the interferometry chain and solutions to overcome them.

Speaker: Dr Sweta Shah (Max Planck Institute for Gravitational Physics, Albert Einstein Institute, Hannover, Germany)
• 14:00
In depth analysis of LISA Pathfinder results and consequences for LISA 10m

We have analysed the time evolution of the acceleration noise in the LISA Pathfinder mission throughout the course of the entire science operations, from March 2016 to July 2017.
The noise across the LISA bandwidth turned out to be remarkably stable over the course of the mission, with a monotonic and well-understood initial decrease over time associated to the the declining residual gas pressure around the TM, while venting the experiment to space.
However, we observed a transient period of excess noise just below 100 uHz at the beginning of the mission, and a final end-of-mission two-month noisier phase, following a rapid system cooldown and the subsequent mechanical stress with long relaxation time.
We performed a Bayesian estimation of the contribution of all potential coherent noise sources for which we have some independent measurements. When adding the remaining modelled noise sources, the noise budget still does not account for the total noise observed during the core minimal-noise phase of the mission.
We present these results and discuss the most likely sources of the observed excess, based on the set of additional experiments and measurements performed during the mission. We also discuss the measures that need to be taken to maintain the LISA performance at the level demonstrated by LISA Pathfinder.

Speakers: Dr Eleonora Castelli (Università degli Studi di Trento - INFN) , Stefano Vitale, Lorenzo Sala, LPF collaboration
• 14:10
Studies of the correlated noise with LISA Pathfinder data. 10m

We are conducing studies of the LISA Pathfinder data, acceleration and auxiliary channels, to develop an understanding for potential noise sources for the future Laser Interferometry Space Antenna (LISA) Mission. The understanding of correlated noise is a goal to establish limits for the attempts to measure a stochastic gravitational wave background using LISA data. The differential acceleration of the test-masses, as well as the temperature, magnetic fields, µ-thruster signals and photodiode currents are examined. We also develop a Wiener filter for the LISA Pathfinder differential acceleration data to decrease the level of the correlated noise in the LISA observational frequency band.

Speaker: Guillaume BOILEAU (Artemis OCA UMR 7250)
• 14:20
In orbit calibration of LISA Pathfinder dynamics: results and implications for LISA 10m

In 2015 LISA Pathfinder (LPF), the LISA technological demonstrator, was launched from Kourou, French Guyana. The main goal of the demonstrator was to measure the differential acceleration noise between two freely falling test-masses, $\Delta g(t)$, such that $S^{1/2}_{\Delta g} < 30 ~\textrm{fm}/\textrm{s}^2/\sqrt{\textrm{Hz}}$ at 1 $\textrm{mHz}$. The in-orbit results showed an unprecedented level of differential acceleration noise, much better than the mission requirement, giving a new impulse to the LISA mission, the gravitational wave observer in the mHz band from space. A key step toward reaching this result was the correct calibration of the dynamics of LPF. In this talk, I will present the calibration procedures adopted, the physical parameters of the dynamical model, and the analysis of the performed experiments. The results demonstrate that the dynamics of the system was accurately modeled on-ground and the dynamical parameters were stationary throughout the mission, with impacts on the LISA mission that is now been developing. The possibility to calibrate the system dynamics for future space-based gravitational wave observatories is also briefly discussed.

Speaker: Dr Daniele Vetrugno (University of Trento)
• 14:30
Limitations on LISA sensitivity to gravitational waves from local spacecraft gravitational field 10m

The Laser Interferometer Space Antenna mission LISA measures the strain in 2.5 million km distant free falling test masses couples, for detecting gravitational waves from galactic and extra galactic sources in the low frequency regime between 20 micro-Hz to 1 Hz. The instrument sensitivity is such that LISA would be able also to detect the effect of the gravitational field on its test masses originating from the mass distribution of their housing spacecrafts. We discuss the different levels of coupling, the foreseen design requirements, and the resultant contribution to the current LISA performance budget.

Speaker: Dr Valerio Ferroni (University of Trento, TIFPA)
• 14:40
Space-based Gravitational-wave Data Analysis Beyond Time Delay Interferometry 10m

The future space-based gravitational wave detector LISA will form a network of laser interferometers across a triangular constellation with 2.5 million-kilometer arms. Among other challenges, the success of the mission strongly depends on our ability to cancel laser frequency noise, whose power lies eight orders of magnitude above the gravitational signal. The standard technique to remove this noise is time-delay interferometry (TDI), a set of linear combinations of delayed phasemeter measurements tailored to cancel noise terms. Previous works have demonstrated the relationship between TDI and principal component analysis. We build on this idea to develop an alternative approach to TDI based on a model likelihood that directly depends on single-link measurements and accounts for their correlations. We obtain a comprehensive and compact framework that we call PCI for "principal component interferometry," and show that it provides a powerful description of the LISA data analysis problem.

Speaker: Dr Quentin Baghi (USRA/NASA GSFC)
• 14:50
Coherent Gravitational Waveforms and Memory from Cosmic String Loops 10m

We construct, for the first time, the time-domain gravitational wave strain waveform from the collapse of a strongly gravitating Abelian Higgs cosmic string loop in full general relativity. We show that the strain exhibits a large memory effect during merger, ending with a burst and the characteristic ringdown as a black hole is formed. Furthermore, we investigate the waveform and energy emitted as a function of string width, loop radius and string tension $G\mu$. We find that the mass normalized gravitational wave energy displays a strong dependence on the inverse of the string tension $E_{\mathrm{GW}}/M_0\propto 1/G\mu$, with $E_{\mathrm{GW}}/M_0 \sim {\cal O}(1)\%$ at the percent level, for the regime where $G\mu\geq 10^{-3}$. Conversely, we show that the efficiency is only weakly dependent on the initial string width and initial loop radii. Using these results, we argue that gravitational wave production is dominated by kinematical instead of geometrical considerations.

Speaker: Thomas Helfer (Johns Hopkins University )
• 15:00
Search for nonlinear memory from subsolar mass compact binary mergers 10m

We present the first search for the nonlinear memory from subsolar mass binary black hole (BBH) mergers during the second observing run of the LIGO and Virgo detectors. The oscillatory chirp signal from the inspiral and merger of low mass BBHs ($M _\mathrm{Total} \leq 0.4 M_\odot$) are at very high frequencies and fall outside the sensitivity band of the current ground-based detectors. However, the non-oscillatory memory signal during the merger saturates towards the lower frequencies and can be detected for those hypothetical BBHs. We show that the morphology of the memory signal depends minimally upon the binary parameters, only the overall amplitude of the signal is changed, hence the result can be interpolated for extremely low mass BBH mergers. We did not find any signal which can be interpreted as a memory signal and thus for the first time we put upper limits on the rate of BBH mergers with $M _\mathrm{Total} \leq 0.4 M_\odot$.

Speaker: Michael Ebersold (Institute of Physics - University of Zurich)
• 15:10
Targeted search for the kinematic dipole of the gravitational-wave background 10m

One of the most important and exciting observational challenges in gravitational-wave (GW) astronomy is the detection of the stochastic GW background (SGWB): the persistent, pseudo-random GW strain associated with the superposition of many astrophysical and cosmological sources throughout cosmic history. The LIGO/Virgo Collaboration (LVC) has performed both isotropic and directional searches for the SGWB, and has already succeeded in placing the most stringent upper limits to date on the SGWB intensity, and its distribution on the sky.

Here we describe a novel SGWB search method, which targets the kinematic dipole (KD) of the SGWB. This dipole is generated by the Earth's motion with respect to the cosmic rest frame, due to GW sources being blueshifted in the direction the Earth is moving toward, and vice versa. The direction of the KD is already known with excellent precision thanks to Planck and other CMB missions; we leverage this knowledge to optimise the sensitivity of the search. We also comment on the physics encoded in the KD magnitude, and how, once detected, this could be a powerful new tool to characterise the source(s) of the SGWB.

Speaker: Alexander Jenkins (King's College London)
• 15:20
Generation of gravitational waves using high-power lasers 10m

Gravitationnal waves have been predicted from Einstein’s equations since he wrote his theory on General Relativity [1]. A century later, the LIGO [2] and VIRGO interferometers were at last able to pick up a gravitationnal wave from the merging of extremely massive astrophysical objects. The existence of gravitationnal waves now being proved, there is a need to study these waves to better understand how gravitation works, and fondamentally how does the geometry of space-time exactly affects physical phenomenons.
However, observations still rely on the occurrence of a rare and intense astrophysical phenomenon, as if, as a comparison, the only reliable source of observation for high energy photons were gamma-ray bursts. An interesting possibility would be to generate and detect gravitationnal waves in laboratory, which would allow for a more controlled environment for the observation of gravitationnal waves. Unfortunately, deplacements of matter generated in laboratory do not seem to have a big enough yield to allow any detection [3].
Continuing on the path led in 1962 by Gertsenshtein [4] and more recently in a study by Kolosnitsyn and Rudenko [5], we will here evaluate if the generation of gravitationnal waves by light only is a good alternative to the deplacement of mass. We will then discuss on the possibilities of an experiment making use of the peculiar aspects of light only gravitational waves generation and bring more details on what could be a new interesting way to look for gravitationnal waves in the laboratory, but also in the universe. High-power lasers present themselves as an interesting answer for the needs of a source for gravitational wave generation, as they can provide coherent ultra high intensity light beams.
[1] A. Einstein. Sitz. Preuss. Akad. Wiss. Berlin, (1918) [4] M. E. Gertsenshtein. Soviet Phys. JETP, (1962) [2] B.P. Abbott et al. Phys. Rev. X 6, (2016) [5] N. I. Kolosnitsyn, V. N. Rudenko. Phys. Scr., 90, (2015) [3] X. Ribeyre, V. T. Tikhonchuk. WSPC, (2010); E. G. Gelfer et al., Physics of Plasmas, 23, (2016)

Speaker: Lageyre (CNRS-CEA)
• 15:30 16:00
Coffee Break 30m
• 16:00 16:30
Experimental Challenges in Gravitational Wave Detection
Convener: Nelson Christensen (Universite de la Cote d’Azur,)
• 16:00
Future Ground-based Gravitational Wave Observatories: Report from the Gravitational Wave International Committee 25m

Future ground-based gravitational-wave (GW) observatories are planned for the next decade in Europe (Einstein Telescope) and the United States (Cosmic Explorer). Additionally, possible upgrades of the existing LIGO observatories (Voyager) as well as a southern hemisphere detector (NEMO) are under discussion. In this talk, I’ll summarize a series of reports by the Gravitational Wave International Committee (GWIC) ‘3G’ Subcommittee on next generation GW facilities including a summary of the major science themes, needed detector R&D and computing challenges. I’ll also highlight some key recommendations to the GW community addressing some of the opportunities and challenges that come with building the next generation of billion euro/dollar scale GW observatories.

Speaker: David Reitze (University of Florida)
• 16:30 18:00
Round Table: Experimental Challenges on Gravitational waves
Conveners: David Reitze (University of Florida) , Fulvio Ricci (ROMA1) , Karsten Danzmann (AEI Hannover) , Matteo Barsuglia (APC-CNRS) , Philippe Bouyer (Institut d'Optique d'Aquitaine - France) , Rita Dolesi (TIFP) , Stefano Vitale (University of Trento) , Venkatraman Krishnan (Max Plank Institute Bonn, Germany)
• Tuesday, 6 July
• 09:30 10:30
Fundamental Tests and Equivalence Principle

Fundamental Tests and Equivalence Principle

Convener: David Wands (University of Portsmouth)
• 09:30
Space clock and fundamental tests. the ACES experiment 30m

Atomic Clock Ensemble in Space (ACES) is developing high performance clocks and links to test Einstein’s theory of general relativity. From the International Space Station, the ACES payload will distribute a clock signal with fractional frequency instability and inaccuracy of 1E-16 establishing a global network to compare clocks in space and on the ground. ACES will provide an accurate measurement of the Einstein’s gravitational redshift, it will search for time variations of fundamental constant and perform Standard Model Extension tests.
The two on-board clocks, PHARAO and SHM, have been tested and integrated on the ACES payload. The microwave (MWL) and optical (ELT) link are currently under test. Once installed on ACES, performance and environmental tests on the complete system will follow to release the final acceptance for flight of the payload.
Recent test results will be presented together with the major milestones that will lead us to the ACES launch.

Speaker: Luigi Cacciapuoti (European Space Agency)
• 10:00
Testing fundamentally semiclassical gravity 30m

Invited talk

Speaker: Andre Grossardt (University of Trieste)
• 10:30 11:00
Coffee Break 30m
• 11:00 12:30
Fundamental Tests and Equivalence Principle

Fundamental Tests and Equivalence Principle

Convener: Renate Loll (Institute for Theoretical Physics, Utrecht University, The Netherlands)
• 11:00
Testing Gravity with Atoms 30m

Invited talk

Speaker: Guglielmo Tino (University of Florence)
• 11:30
Testing the equivalence principle in space with MICROSCOPE: countdown to the final results 30m

The MICROSCOPE satellite was launched in April 2016 and ended its operations in October 2018. Aiming at testing the Equivalence Principle (EP) with an accuracy better than ever tested, the satellite has provided usefull scientific data during more than two years. The EP is the funding hypothesis of the General Relativity (GR) established by Einstein in 1917. It states the equivalence between gravitational and inertial mass: commonly called the universality of free-fall. The science motivation relies mainly in the observation of an eventual violation that could give the first clue of a new interaction, bridging GR to Quantum Physics.

Onera was responsible for the instrument developpement, production and test. In addition, it is also responsible for the science and the mission science center which deals with the science operations and data process. In December 2017, the first results, based on only 7$\%$ of the available data, were published in PRL and improved the best laboratory results by one order of magnitude.

The de-orbitation of MICROSCOPE has started, thanks to two deployed wings. The final data process is almost complete in conjonction to the assessment of systematic errors. A particular emphasis will be placed on the handling of glitches. The glitches are mainly produced by the satellite MLI cracking when it is more or less enlightened by the Sun or the Earth. Their temporal distribution could be in competition to an eventual violation signal.

With the preparation of the final result paper, a mission called MICROSCOPE 2 is beeing studied in order to improve by an additional factor 100 the previous mission. By taking advantage of of the MICROSCOPE experiment return, the instrument and satellite design will be improved. Three concentric test-masses are envisaged with optical sensing as the main deep change.

Speaker: Mr Manuel Rodrigues (ONERA)
• 12:00
Antimatter, Gravity and Fundamental Test 30m
Speaker: Marco Giulio Giammarchi (MI)
• 12:30 14:00
Lunch break 1h 30m
• 14:00 16:10
Recorded Talks: Fundamental Test and Equivalence Principle
• 14:00
The Archimedes Experiment 10m

Saverio Avino, Enrico Calloni, Sergio Caprara, Martina De Laurentis,
Rosario De Rosa, Tristano Di Girolamo, Luciano Errico, Gianluca Gagliardi,
Marco Grilli, Valentina Mangano, Maria Antonietta Marsella, Luca Naticchioni,
Giovanni Piero Pepe, Maurizio Perciballi, Gabriel Pillant, Paola Puppo, Piero Rapagnani,
Fulvio Ricci, Luigi Rosa, Carlo Rovelli, Paolo Ruggi, Naurang L. Saini, Daniela
Stornaiuolo, Francesco Tafuri and Arturo Tagliacozzo

The Archimedes project aims to measure the interaction between the electromagnetic vacuum fluctuations and the gravitational field. The experiment can shed light on some question marks still open in cosmology like the dark energy nature.
A very sensitive balance has been constructed to weight the vacuum e.m. field energy induced in a multi-Casimir cavity system by temperature modulation techniques. The system is a high TC superconductor like the YBCo material having multilayered structure useful for this purpose.
This experiment is being installed in the SARGRAV laboratory placed Sardinia a very low seismic noise site, suitable for null force experiments.
In this talk the status of the experiment will be reported.

Speaker: Paola Puppo (ROMA1)
• 14:10
Present status of the LAG experiment 10m

LAG (Liquid Actuated Gravity) is an experiment funded by the INFN (National Institute of Nuclear Physics) for the development and testing of a new actuation technique for gravity experiments based on a liquid field mass. The basic idea of the experiment is to modulate the gravitational force acting on a test mass by controlling the level of a liquid in a suitable container, thereby producing a periodically varying gravitational force without moving parts (apart from the liquid level) close to the test mass. The scientific goal is to improve upon present limits that test the gravitational inverse-square law in the mm to cm distance region. The experiment is now in the R&D phase; a prototype has been assembled for testing with a torsion pendulum facility in Napoli and is now under commissioning. First data with the prototype apparatus are expected this year. We will report on present status, next steps and scientific perspectives for the LAG experiment

Speaker: Luciano Di Fiore (NA)
• 14:20
Testing general relativity in the solar system: present and future perspectives 10m

The increasing precision of spacecraft radiometric tracking data experienced in the last decade, combined with the huge amount of data collected from space missions and the long time span of the available datasets, has enabled a refined analysis of the Solar System dynamics. High precision tests of General Relativity can be performed through the measurement of the post-Newtonian parameters, including the Nordtvedt parameter $\eta$, and the Compton wavelength of the graviton. In this work we investigate the relative contributions to these tests provided by the most relevant past, present and future interplanetary missions, with the goal of assessing the accuracies that can be realistically reached in the next 10–15 years.

A semi-analytical model, validated by means of a comparison with well-established numerical models, has been developed to compute the signatures generated by the parameters of interest in the measurements and to assess the precision of their retrieval. We also revisit some of the hypotheses and constrained analysis schemes that have been proposed until now to overcome geometric weaknesses and model degeneracies, proving that many of the previously adopted strategies introduce model inconsistencies.

We apply our semi-analytical model to perform a covariance analysis on three groups of interplanetary missions:
(1) those for which data are available now (e.g. Cassini, MESSENGER, MRO, Juno),
(2) those expected in the next years (BepiColombo) and
(3) those still to be launched or proposed, such as JUICE and VERITAS (the latter, chosen as a representative of a state-of-the-art Venus orbiter).

Finally, we describe the preliminary results of a more rigorous and general procedure: a global, multi-mission data analysis.

Speaker: Dr Fabrizio De Marchi (University of Rome "La Sapienza")
• 14:30
Measuring gravitation with antihydrogen: the ALPHA-g experiment 10m

ALPHA (Antihydrogen Laser PHysics Apparatus) is a leading antihydrogen experiment located at CERN, the European Organization for Nuclear Research in Geneva, Switzerland. The ALPHA-g project is a new initiative by the ALPHA collaboration to measure the gravitational interaction of antimatter. ALPHA-g apparatus features a 3 meter tall cryogenic, superconducting magnetic trap. Antihydrogen atoms will be created, captured, cooled and then dropped, in order to study if antimatter behaves the same way as matter does in the field of the Earth gravity.

Speaker: Pierre Grandemange (CERN)
• 14:40
Antigravity, a Force yet to be Recognized by Physics 15m

The general belief is that the gravitational force is always attractive and no repulsive force could result. This is contrary to properties of electric and magnetic forces, which can cause in both attraction and repulsion. The investigation presented here on the movement of liquid water droplets in still air, prompts us to believe a hidden force, a force against the gravitational pull, hitherto unknown to the world of science. Anti-gravity is proportionate to the temperature, which is an indication of the thermal energy of the matter. It is widely accepted that gravity is proportionate to the mass of the matter. Any gravitational interaction could be considered the resultant effect of the gravitational and antigravitational forces inherent in the two bodies under consideration. The gravitational force is considered a weak force in classical physics. Being what we can observe in nature is the resultant of these two forces, the gravitational force manifests itself as a weak force. It is felt, as shown by the reasoning adduced herein, that the upward movement of the water droplets cannot be explained by the conventional principles of physics known to us. Hence the need of the antigravity hypothesis.

• 14:45
Measuring Gravity with very long baseline Atom Interferometer 15m
Speaker: Dorothee Tell (Leibniz University Hannover)
• 14:55
Testing the speed of gravity and deviations from GR with LISA 10m

We explore prospects for measuring the speed of gravity using future gravitational-wave surveys in the multi-messenger approach, and probe implications for cosmological models.

Speaker: Dr Maria Haney (University of Zurich)
• 15:05
Clock developments for fundamental physics tests and space 15m
Speaker: Patrick Gill (National Physical Laboratory UK)
• 15:20
Constraint on the Yukawa suppression from the planetary ephemeris INPOP19a 10m

We use the latest solution of the ephemeris INPOP (19a) in order to improve our previous constraint on the existence of a Yukawa suppression to the Newtonian potential [1], generically associated to the graviton's mass. Unlike the solution INPOP17a, several residuals are found to degrade significantly at roughly the same amplitudes of the Compton wavelength associated to the mass of the Yukawa field. As a consequence, we introduce a novel statistical method in order to derive the constraint with INPOP19a. After checking that it leads to a constaint consistent with our previous result when applied on INPOP17b, we apply the method to the new solution INPOP19a. We show that the residuals of Mars orbiters, Cassini, Messenger, and Juno, degrade significantly when $\lambda_g >2.61 \times 10^{13}$ km with a 99,7% confidence level---corresponding to a graviton mass bigger than $4.75 \times 10^{-23}$ eV$/c^2$. The solar system constraint on the Compton wavelength becomes better than the one obtained so far by the LIGO-Virgo collaboration in the radiative regime [2].

References :

[1] L. Bernus, O. Minazzoli, A. Fienga, M. Gastineau,
J. Laskar, and P. Deram, “Constraining the mass of the
graviton with the planetary ephemeris inpop,” Phys. Rev.
Lett. 123, 161103 (2019).

[2] The LIGO Scientific Collaboration and the Virgo Col-
laboration, “Tests of General Relativity with the Bi-
nary Black Hole Signals from the LIGO-Virgo Cata-
log GWTC-1,” Phys. Rev. D. 100, 104036 (2019)

Speaker: Léo Bernus (IMCCE)
• 15:30 16:00
Coffee Break 30m
• 16:00 17:30
Round Table: Fundamental Tests and Equivalence Principle
• Wednesday, 7 July
• 09:30 10:30
Geodesy and Ranging
• 09:30
Gravity in the solar system 30m

Invited talk

Speaker: Luciano Iess (Universita' La Sapienza)
• 10:00
Future costallations for observing Earth's time variable gravity field 30m

Invited talk

Speaker: Pieter Visser (Delft University of Technology)
• 10:30 11:00
Coffee Break 30m
• 11:00 12:30
Geodesy and Ranging
• 11:00
Relativistic Geodesy Using Optical Clocks 30m

Invited Talk

Speaker: Helen Margolis (National Physical Laboratory Teddington UK)
• 11:30
Lunar and interplanetary laser ranging 30m

Invited talk

Speaker: Simone Dell'Agnello (LNF)
• 12:00
The first interspacecraft laser ranging interfrometer on GRACE Follow-On and conclusions for future gravity missions 30m
Speaker: Gerhard Heinzel (AEI Max-Planck Institut)
• 12:30 14:00
Lunch Break 1h 30m
• 14:00 15:30
Recorder Talks: Geodesy and Ranging
• 15:30 16:00
Coffee Break 30m
• 16:00 17:30
Round Table: Geodesy and Ranging
• 17:30 18:00
Concluding Remarks