The rotation curve of a point particle in stringy gravity
  Double Field Theory suggests to view the whole massless sector of closed
strings as the gravitational unity. The fundamental symmetries therein,
including the $\mathbf{O}(D,D)$ covariance, can determine unambiguously how the
Standard Model as well as a relativistic point particle should couple to the
closed string massless sector. The theory also refines the notion of
singularity. We consider the most general, spherically symmetric,
asymptotically flat, static vacuum solution to ${D=4}$ Double Field Theory,
which contains three free parameters and consequently generalizes the
Schwarzschild geometry. Analyzing the circular geodesic of a point particle in
string frame, we obtain the orbital velocity as a function of
$R/(M_{\scriptscriptstyle{\infty}}G)$ which is the dimensionless radial
variable normalized by mass. The rotation curve generically features a maximum
and thus non-Keplerian over a finite range, while becoming asymptotically
Keplerian at infinity, $R/(M_{\scriptscriptstyle{\infty}}G)\rightarrow \infty$.
The adoption of the string frame rather than Einstein frame is the consequence
of the fundamental symmetry principle. Our result opens up a new scheme to
solve the dark matter/energy problems by modifying General Relativity at
`short' range of $R/(M_{\scriptscriptstyle{\infty}}G)$.
