# T-duality constraint on R-R couplings

## TL;DR

This paper investigates how T-duality constrains Ramond-Ramond couplings in string theory, showing that these couplings can be derived by imposing T-duality symmetry, consistent with the known democratic form.

## Contribution

It extends the T-duality constraint approach to include R-R couplings, explicitly deriving their form at the supergravity level.

## Key findings

- R-R couplings are consistent with T-duality constraints.
- Dimensional reduction of R-R fields aligns with known democratic form.
- T-duality imposes strong restrictions on R-R interactions.

## Abstract

It has been speculated that the metric, $B$-field and dilaton couplings in the low energy effective action of string theory at any order of $\alpha'$ may be found by imposing the gauge symmetries and the T-duality on the effective action. This proposal can be extended to include the Ramond-Ramond (R-R) couplings as well. In this paper, we first find the dimensional reduction of the R-R fields and then perform explicitly the T-duality constraint on the R-R couplings at the supergravity level. Up to an overall factor, it reproduces the democratic form of the R-R couplings.