  A particularly attractive feature of inflation is that quantum fluctuations
in the inflaton field may have seeded inhomogeneities in the cosmic microwave
background (CMB) and the formation of large-scale structure. In this paper, we
demonstrate that a scalar field with zero active mass, i.e., with an equation
of state rho+3p=0, where rho and p are its energy density and pressure,
respectively, could also have produced an essentially scale-free fluctuation
spectrum, though without inflation. This alternative mechanism is based on the
Hollands-Wald concept of a minimum wavelength for the emergence of quantum
fluctuations into the semi-classical universe. A cosmology with zero active
mass does not have a horizon problem, so it does not need inflation to solve
this particular (non) issue. In this picture, the 1-10 degree fluctuations in
the CMB correspond almost exactly to the Planck length at the Planck time,
firmly supporting the view that CMB observations may already be probing
trans-Planckian physics.
