Constraints from CMB on Spacetime Noncommutativity and Causality Violation

TL;DR

This paper uses observational data from ACBAR, CBI, and WMAP to set lower bounds on the energy scale of spacetime noncommutativity and explores how noncommutativity leads to direction-dependent causality violations in primordial scalar fields.

Contribution

It provides observational constraints on the noncommutativity scale and derives a new expression for causality violation due to spacetime noncommutativity.

Findings

ACBAR and CBI data set a lower bound of ~10 TeV on the noncommutativity energy scale.

WMAP data does not constrain the noncommutativity parameter.

Causality violation is direction-dependent for primordial scalar perturbations.

Abstract

We try to constrain the noncommutativity length scale of the theoretical model given in Ref. [1] using the observational data from ACBAR, CBI and five year WMAP. The noncommutativity parameter is not constrained by WMAP data, however ACBAR and CBI data restrict the lower bound of its energy scale to be around 10 TeV. We also derive an expression for the amount of non-causality coming from spacetime noncommutativity for the fields of primordial scalar perturbations that are space-like separated. The amount of causality violation for these field fluctuations are direction dependent.