  Many warm Jupiters (WJs) have substantial eccentricities, which are linked to
their formation and migration histories. This paper explores eccentricity
excitation of WJs due to planet-planet scattering, beginning with 3-4 planets
in unstable orbits, with the innermost planet placed in the range (0.1 - 1)AU.
Such a setup is consistent with either in-situ formation or arrival at sub-AU
orbits due to disk migration. Most previous N-body experiments have focused on
"cold" Jupiters at several AU, where scattering results in planet ejections,
efficiently exciting the eccentricities of surviving planets. In contrast,
scattering at sub-AU distances results in a mixture of collisions and
ejections, and the final eccentricities of surviving planets are unclear. We
conduct scattering experiments for a range of planet masses and initial
spacings, including the effect of general relativistic apsidal precession, and
systematically catalogue the scattering outcomes and properties of surviving
planets. A comparable number of one-planet and two-planet systems are produced.
Two-planet systems arise exclusively through planet-planet collisions, and tend
to have low eccentricities/mutual inclinations and compact configurations.
One-planet systems arise through a combination of ejections and collisions,
resulting in higher eccentricities. The observed eccentricity distribution of
solitary WJs (lacking detection of a giant planet companion) is consistent with
roughly 60% of the systems having undergone in-situ scattering, and the
remaining experiencing a quiescent history.
