  It was recently noted that the on-shell Einstein-Hilbert action with
York-Gibbons-Hawking boundary term has an imaginary part, proportional to the
area of the codimension-2 surfaces on which the boundary normal becomes null.
We discuss the extension of this result to first-order formulations of gravity.
As a side effect, we settle the issue of the Holst modification vs. the
Nieh-Yan density by demanding a variational principle with suitable boundary
conditions. We then set out to find the imaginary action in the large-spin
4-simplex limit of the Lorentzian EPRL/FK spinfoam. It turns out that the
spinfoam's effective action indeed has the correct imaginary part, but only if
the Barbero-Immirzi parameter is set to +/- i after the quantum calculation. We
point out an agreement between this effective action and a recent black hole
state-counting calculation in the same limit. Finally, we propose that the
large-spin limit of loop quantum gravity can be viewed as a high-energy
'transplanckian' regime.
