  We investigate a general relativistic mechanism in which spikes generate
matter overdensities in the early universe. When the cosmological fluid is
tilted, the tilt provides another mechanism in generating matter
inhomogeneities. We numerically investigate the effect of a sign change in the
tilt, when there is a spike but the tilt does not change sign, and when the
spike and the sign change in the tilt coincide. We find that the tilt plays the
primary role in generating matter inhomogeneities, and it does so by creating
both local overdensities and underdensities. We discuss of the physical
implications of the work.
