  Angle-resolved photoemission spectroscopy (ARPES) is a powerful experimental
technique for directly probing electron dynamics in solids. The energy vs.
momentum dispersion relations and the associated spectral broadenings measured
by ARPES provide a wealth of information on quantum many-body interaction
effects. In particular, ARPES allows studies of the Coulomb interaction among
electrons (electron-electron interactions) and the interaction between
electrons and lattice vibrations (electron-phonon interactions). Here, we
report ab initio simulations of the ARPES spectra of graphene including both
electron-electron and electron-phonon interactions on the same footing. Our
calculations reproduce some of the key experimental observations related to
many-body effects, including the indication of a mismatch between the upper and
lower halves of the Dirac cone.
