  Ultralight dark matter (ULDM) is usually taken to be a single scalar field.
Here we explore the possibility that ULDM consists of $N$ light scalar fields
with only gravitational interactions. This configuration is more consistent
with the underlying particle physics motivations for these scenarios than a
single ultralight field. ULDM halos have a characteristic granular structure
that increases stellar velocity dispersion and can be used as observational
constraints on ULDM models. In multifield simulations, we find that inside a
halo the amplitude of the total density fluctuations decreases as $1/\sqrt{N}$
and that the fields do not become significantly correlated over cosmological
timescales. Smoother halos heat stellar orbits less efficiently, reducing the
velocity dispersion relative to the single field case and thus weakening the
observational constraints on the field mass. Analytically, we show that for $N$
equal-mass fields with mass $m$ the ULDM contribution to the stellar velocity
dispersion scales as $1/(N m^3)$. Lighter fields heat the most efficiently and
if the smallest mass $m_L$ is significantly below the other field masses the
dispersion scales as $1/(N^2 m_L^3)$.
