Probing the Microscopic Origin of Gravity via Precision Polarization and Spin Experiments

TL;DR

This paper discusses how precision polarization and spin experiments can test the microscopic origins of gravity, focusing on axion effects and spin-gravity interactions within an effective field theory framework.

Contribution

It introduces a phenomenological framework to connect experiments with the microscopic theory of gravity, emphasizing the role of axions and spin interactions.

Findings

Potential to test axion effects on cosmic polarization

Proposal of measuring gyrogravitational ratios of particles

Identification of experimental methods for probing gravity's microscopic origin

Abstract

As in other parts of physics, we advocate the interaction approach: experiments <--> phenomenology <--> low-energy effective (field) theory <--> microscopic theory to probe the microscopic origin of gravity. Using chi-g phenomenological framework, we discuss the tests of equivalence principles. The only experimentally unconstrained degree of freedom is the axion freedom. It has effects on the long-range astrophysical/cosmological propagation of electromagnetic waves and can be tested/measured using future generation of polarization measurement of cosmic background radiation. The verification or refutal of this axionic effect will be a crucial step for constructing effective theory and probing the microscopic origin of gravity. The interaction of spin with gravity is another important clue for probing microscopic origin of gravity. The interplay of experiments, phenomenology and effective theory is expounded. An ideal way to reveal the microscopic origin of gravity is to measure the gyrogravitational ratio of particles. Three potential experimental methods are considered.