April 19, 2024

Gravitational Waves: LISA and the Detection of New Fundamental Fields – Is General Relativity Correct?

Observations of astrophysical items with weak gravitational fields and little spacetime curvature have supplied no evidence of such fields so far. LISA is a space-based gravitational wave observatory structure on the success of LISA Pathfinder and LIGO. The Authors have established a new approach for modeling the signal and performed for the very first time a strenuous quote of LISAs ability to spot the presence of scalar fields coupled with the gravitational interaction, and to measure the scalar charge, a quantity which measures how much scalar field is brought by the little body of the EMRI. LISA will observe gravitational waves released at low frequency, within a band not available to terrestrial interferometers due to environmental noise.

A recent Letter released on February 9, 2022, in Nature Astronomy, authored by a scientist of the GSSI and coworkers from SISSA, the University of Nottingham, and from La Sapienza of Rome, recommends that a response to these concerns may come from LISA, the space-based gravitational-wave (GW) detector which is expected to be launched by ESA/NASA in 2037.
Short section of the orbital path followed by the excellent component of an EMRI around a spinning black hole. Credit: N. Franchini
New essential fields, and in particular scalars, have been postulated in a range of scenarios: as explanations for dark matter, as the cause for the accelerated expansion of deep space, or as low-energy manifestations of a complete and constant description of gravity and primary particles.
Observations of astrophysical things with weak gravitational fields and small spacetime curvature have supplied no proof of such fields up until now. There is reason to anticipate that discrepancies from General Relativity, or interactions between gravity and new fields, will be more prominent at big curvatures. For this reason, the detection of GWs– which opened a novel window on the strong-field routine of gravity– represents an unique opportunity to detect these fields.
Severe Mass Ratio Inspirals (EMRI) in which a stellar-mass compact object, either a great void or a neutron star, inspirals into great void up to countless times the mass of the Sun, are among the target sources of LISA, and supply a golden arena to penetrate the strong-field routine of gravity. The smaller sized body carries out 10s of thousands of orbital cycles prior to it plunges into the supermassive great void and this results in long signals that can enable us to detect even the smallest deviations from the predictions of Einsteins theory and the Standard Model of Particle Physics.
Artists impression of LISA Pathfinder, ESAs objective to evaluate innovation for future gravitational-wave observatories in area. LISA is a space-based gravitational wave observatory building on the success of LISA Pathfinder and LIGO. Credit: ESA– C.Carreau.
The Authors have established a brand-new technique for modeling the signal and performed for the first time an extensive estimate of LISAs ability to discover the presence of scalar fields coupled with the gravitational interaction, and to determine the scalar charge, an amount which determines just how much scalar field is brought by the little body of the EMRI. Remarkably, this technique is theory-agnostic, given that it does not depend on the origin of the charge itself, or on the nature of the little body. The analysis also shows that such measurement can be mapped to strong bounds on the theoretical parameters that mark variances from General Relativity or the Standard Model.
LISA (Laser Interferometer Space Antenna), dedicated to identify gravitational waves by astrophysical sources, will operate in a constellation of 3 satellites, orbiting around the Sun millions of kilometers far from each other. LISA will observe gravitational waves produced at low frequency, within a band not readily available to terrestrial interferometers due to ecological sound. The noticeable spectrum for LISA will enable to study brand-new families of astrophysical sources, different from those observed by Virgo and LIGO, as the EMRIs, opening a new window on the evolution of compact items in a big variety of environments of our Universe.
Recommendation: “Detecting fundamental fields with LISA observations of gravitational waves from severe mass-ratio inspirals” by Andrea Maselli, Nicola Franchini, Leonardo Gualtieri, Thomas P. Sotiriou, Susanna Barsanti and Paolo Pani, 10 February 2022, Nature Astronomy.DOI: 10.1038/ s41550-021-01589-5.

Illustration of 2 orbiting black holes deforming spacetime and generating gravitational waves.
Released in Nature Astronomy the work which shows the unprecedented accuracy with which gravitational wave observations by the area interferometer LISA will have the ability to spot new essential fields
Published in Nature Astronomy the work by Andrea Maselli, researcher at GSSI and INFN associate, together with researchers from SISSA, the University of Nottingham and La Sapienza of Rome, which shows the extraordinary precision with which gravitational wave observations by the space interferometer LISA will have the ability to spot brand-new fundamental fields.
Is General Relativity the proper theory of gravitation? Can gravity be used to find brand-new fundamental fields?