Wider research context 

The search for generalized gravitational theories is highly topical now. Observational cosmology led to the introduction of the concepts of dark matter and dark energy. Theoretically, the high-energy behavior and existence of gravitational singularities motivates the search for extensions of Einstein’s General Relativity.

A well-motivated extension are gravitational theories including torsion, with historical roots going back to Cartan’s work in 1922. In such theories, the anti-symmetric part of the affine connection comprising the torsion tensor does not vanish, as in General Relativity. This leads to a new natural geometrical quantity in addition to the metric tensor. From a modern group theoretical and from a differential geometric point of view, theories with torsion appear more natural than Einstein’s original formulation of General Relativity with only a symmetric affine connection.

Hypotheses / research questions / objectives

Only recently, experimentally obtained sensitivities allow us the effective search for torsion. Our team at TU Wien developed Gravity Resonance Spectroscopy (GRS), a new measuring technique combining quantum measurements and gravity experiments. Torsion or Lorentz invariance violating forces would provide an additional potential to Newton’s gravity law thus changing the energy states of a neutron in the gravity potential.

Approach / methods

Within this project, GRS will be applied to the most sensitive measuring technique, the Ramsey Method of Oscillating Fields. Neutrons are put in defined energy states in the gravity potential of the Earth. GRS measures precisely these energy states by driving transitions allowing to search for deviations from the laws of gravity. We expect a sensitivity of 7 ^. 10^-17 eV. If some undiscovered particles interact with neutrons, this should result in a measurable energy shift of the observed quantum states shown in Fig. 1 of the proposal.