  The large difference between the Planck scale and the electroweak scale,
known as the hierarchy problem, is addressed in certain models through the
postulate of extra spatial dimensions. A search for evidence of extra spatial
dimensions in the diphoton channel has been performed using the full set of
proton-proton collisions at sqrt(s) = 7 TeV recorded in 2011 with the ATLAS
detector at the CERN Large Hadron Collider. This dataset corresponds to an
integrated luminosity of 4.9 fb. The diphoton invariant mass spectrum is
observed to be in good agreement with the Standard Model expectation. In the
context of the model proposed by Arkani-Hamed, Dimopoulos and Dvali, 95%
confidence level lower limits of between 2.52 TeV and 3.92 TeV are set on the
ultraviolet cutoff scale Ms depending on the number of extra dimensions and the
theoretical formalism used. In the context of the Randall--Sundrum model, a
lower limit of 2.06 (1.00) TeV at 95% confidence level is set on the mass of
the lightest graviton for couplings of k/Mpl = 0.1 (0.01). Combining with the
ATLAS dilepton searches based on the 2011 data, the 95% confidence level lower
limit on the Randall--Sundrum graviton mass is further tightened to 2.23 (1.03)
TeV for k/Mpl = 0.1 (0.01).
