Scalar modifications to gravity from unparticle effects may be testable

TL;DR

This paper explores how unparticle physics could lead to testable modifications of gravity, predicting specific power-law deviations from Newton's law that differ from extra dimension models, and discusses potential experimental discrimination.

Contribution

It calculates the ungravity correction to Newtonian gravity under conformal invariance, deriving distinctive power-law modifications and constraints on unparticle dimensions.

Findings

Ungravity induces power-law corrections to gravity with specific dependence on unparticle dimension.

Constraints on unparticle dimension d_U are established for different spin couplings.

Future experiments could distinguish ungravity effects from extra dimension models.

Abstract

Interest has focussed recently on low energy implications of a nontrivial scale invariant sector of an effective field theory with an IR fixed point, manifest in terms of ``unparticles'' with peculiar properties. If unparticle stuff exists it could couple to the stress tensor and mediate a new 'fifth' force which we call 'ungravity' arising from the exchange of unparticles between massive particles, which in turn could modify the inverse square law. Under the assumption of strict conformal invariance in the hidden sector down to low energies, we compute the lowest order ungravity correction to the Newtonian gravitational potential and find scale invariant power law corrections of type $(R_{G}/r)^{2d_{\cal U} -1}$ where $d_{\cal U}$ is an anomalous unparticle dimension and $R_{G}$ is a characteristic length scale where the ungravity interactions become significant. $d_{\cal U}$ is constrained to lie the range $ d_{\cal U} > 3 (2)$ for a spin 2 (spin 0) unparticle coupling to the stress tensor (and its trace) and leads to modification of the inverse square law with $r$ dependence in the range between $1/r^{4+2\delta} (\delta>0)$, while extra dimension models with warping modify the force law with corrections beginning with terms O$(1/r^3)$ for small $r$ but exponentially suppressed for large $r$. Thus a discrimination between extra dimension models and ungravity is possible in future improved submillimeter tests of gravity.