Abstract:
Time-dependent density functional generally suffers from an
ultra-nonlocality problem, namely the local density approximation
for the exchange-correlation potential always fails, no matter how
slowly varying is the density. I show that this problem is
particularly severe in time-dependent spin density functional
theory, but can be cured by switching to a formulation in which the
spin currents are the basic variables. I discuss the physical
significance of the new terms that appear in the spin-current
dependent functional, and review the progress that has been made in
providing explicit expressions for the latter.
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