Scalar Modifications to Gravity from Unparticle Effects May Be Testable

Interest has focused 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 (“ungravity”). 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 $(R_G/r{)}^{2d_{\mathcal{U}}-1}$, where $d_{\mathcal{U}}$ is an anomalous unparticle dimension and $R_G$ is a characteristic length scale where the ungravity interactions become significant. It is shown that a discrimination between extra dimension models and ungravity is possible in future improved submillimeter tests of gravity.

Figure 1

Left side: allowed region (below curve) for $R_G$ [Eq. (7)] for a region of $d_{\mathcal{U}}$. Right side: allowed region in $M_{*}-{\Lambda }_{\mathcal{U}}$ parameter space (above curves) for various values of $d_{\mathcal{U}}$. The seeming confluence of the three lines at a single point is not exact.