  Recent observations by the James Webb Space Telescope (JWST) discovered
unexpectedly abundant luminous galaxies at high redshift, posing possibly a
severe challenge to popular galaxy formation models. We study early structure
formation in a cosmological model with a blue, tilted power spectrum (BTPS)
given by $P(k) \propto k^{m_{\rm s}}$ with $m_{\rm s} > 1$ at small length
scales. We run a set of cosmological $N$-body simulations and derive the
abundance of dark matter halos and galaxies under simplified assumptions on
star formation efficiency. The enhanced small-scale power allows rapid
nonlinear structure formation at $z>7$, and galaxies with stellar mass
exceeding $10^{10}\,M_\odot$ can be formed by $z=9$. Because of frequent
mergers, the structure of galaxies and galaxy groups appears clumpy. The BTPS
model reproduces the observed stellar mass density at $z=7-9$, and thus eases
the claimed tension between galaxy formation theory and recent JWST
observations. The large-scale structure of the present-day Universe is largely
unaffected by the modification of the small-scale power spectrum. We conduct a
systematic study by varying the slope of the small-scale power spectrum to
derive constraints on the BTPS model from a set of observations of
high-redshift galaxies.
