We have measured compressibility of a two-dimensional hole gas in
p-GaAs/AlGaAs heterostructure, grown on a (100) surface, in the presence of a
tilted magnetic field. It turns out that the parallel component of magnetic
field affects neither the spin splitting nor the density of states. We conclude
that: (a) g-factor in the parallel magnetic field is nearly zero in this
system; and (b) the level of the disorder potential is not sensitive to the
parallel component of the magnetic field
