LISA's gravitational wave observation will have unprecedented accuracy and is expected to detect a new basic field.

A new study published in the journal Nature-Astronomy shows that the gravitational wave observation of laser interferometric space antenna (LISA) will have unprecedented accuracy, and it will be able to detect new basic fields.

Is general relativity the correct theory of gravity? Can gravity be used to detect new fundamental fields? According to this letter published in Nature-Astronomy on February 9, 2022 (written by GSSI researchers and researchers from SISSA, Nottingham University and La Sapienza in Rome), the answers to these questions may come from LISA, a space-based gravitational wave (GW) detector, which is expected to be launched by ESA/NASA in 2037.

New fundamental fields, especially scalars, have been assumed in various situations: as an explanation of dark matter, as a reason for the accelerated expansion of the universe, or as a low-energy expression that gives a consistent and complete description of gravity and elementary particles.

The observation of astrophysical objects with weak gravitational field and small curvature of spacetime has not provided evidence of such field so far. However, researchers believe that under large curvature, the deviation from general relativity or the interaction between gravity and new field will be more prominent. Therefore, the detection of GW-which opens a new window for the strong gravitational field system-represents a unique opportunity to detect these fields.

Extreme mass ratio spine (EMRI) is one of Lisa's target sources. A dense celestial body with the mass of a star, whether it is a black hole or a neutron star, is accreted into a black hole with the mass millions of times that of the sun, which provides a "golden stage" for detecting the strong gravitational field system. Smaller celestial bodies will make tens of thousands of orbital cycles before falling into supermassive black holes, which leads to long signals, enabling people to detect even the smallest deviation predicted by Einstein's theory and the standard model of particle physics.

The author develops a new signal modeling method, and critically evaluates LISA's ability to detect the existence of scalar field coupled with gravitational interaction for the first time, and measures the scalar charge, which is a measure of how many scalar fields EMRI small celestial bodies carry. It is worth noting that this method has nothing to do with theory, because it does not depend on the source of charge itself, nor on the nature of small celestial bodies. The analysis also shows that this kind of measurement can be mapped to the strong limitation of theoretical parameters that mark deviation from general relativity or standard model.

LISA is committed to detecting gravitational waves from astrophysical sources and will run in a constellation of three satellites, orbiting the sun, millions of kilometers away from each other. LISA will observe gravitational waves emitted at low frequency, which cannot be used by ground interferometer due to environmental noise. LISA's visible spectrum will allow the study of a series of new astrophysical sources. Different from the astrophysical sources observed by Virgo and LIGO, as EMRIs, it opens a new window for the evolution of dense celestial bodies in various environments in the universe.