  In recent years, there is considerable experimental effort using cold atoms
to study strongly correlated many-body systems. One class of phenomena of
particularly interests is quantum critical (QC) phenomena. While prevalent in
many materials, these phenomena are notoriously difficult theoretical problems
due to the vanishing of energy scales in QC region. So far, there are no
systematic ways to deduce QC behavior of bulk systems from the data of trapped
atomic gases. Here, we present a simple algorithm to use the experimental
density profile to determine the T=0 phase boundary of bulk systems, as well as
the scaling functions in QC regime. We also present another scheme for removing
finite size effects of the trap. We demonstrate the validity of our schemes
using exactly soluble models.
