  We explore some fundamental differences in the phenomenology, cosmology and
model building of Split Supersymmetry compared with traditional low-scale
supersymmetry. We show how the mass spectrum of Split Supersymmetry naturally
emerges from theories where the dominant source of supersymmetry breaking
preserves an $R$ symmetry, characterize the class of theories where the
unavoidable $R$-breaking by gravity can be neglected, and point out a new
possibility, where supersymmetry breaking is directly communicated at tree
level to the visible sector via renormalizable interactions. Next, we discuss
possible low-energy signals for Split Supersymmetry. The absence of new light
scalars removes all the phenomenological difficulties of low-energy
supersymmetry, associated with one-loop flavor and CP violating effects.
However, the electric dipole moments of leptons and quarks do arise at two
loops, and are automatically at the level of present limits with no need for
small phases, making them accessible to several ongoing new-generation
experiments. We also study proton decay in the context of Split Supersymmetry,
and point out scenarios where the dimension-six induced decays may be
observable. Finally, we show that the novel spectrum of Split Supersymmetry
opens up new possibilities for the generation of dark matter, as the decays of
ultraheavy gravitinos in the early universe typically increase the abundance of
the lightest neutralino above its usual freeze-out value. This allows for
lighter gauginos and Higgsinos, more accessible both to the LHC and to
dark-matter detection experiments.
