The reduction of the energy gap due to Landau level mixing, characterized by
the dimensionless parameter λ=(e2/ϵl0)/ℏωc, has
been calculated by variational Monte Carlo for the fractional quantum Hall
effect at filling fractions ν=1/3 and 1/5 using a modified version of
Jain's composite fermion wave functions. These wave functions exploit the
Landau level mixing already present in composite fermion wave functions by
introducing a partial Landau level projection operator. Results for the energy
gaps are consistent with experimental observations in n-type GaAs, but we
conclude that Landau level mixing alone cannot account for the significantly
smaller energy gaps observed in p-type systems.Comment: 11 pages, RevTex, 2 figures in compressed tar .ps forma