Constraints on cosmological parameters from MAXIMA-1

We set new constraints on a seven-dimensional space of cosmological paramet ers within the class of inflationary adiabatic models. We use the angular p ower spectrum of the cosmic microwave background measured over a wide range of l in the first flight of the MAXIMA balloon-borne experiment (MAXIMA-1) and the low-l results from the COBE Differential Microwave Radiometer expe riment. We find constraints on the total energy density of the universe, Om ega = 1.0(-0.30)(+0.15), the physical density of baryons, Omega (b)h(2) = 0 .03 +/- 0.01, the physical density of cold dark matter, Omega (cdm)h(2) = 0 .2(-0.1)(+0.2), and the spectral index of primordial scalar fluctuations, n (s) = 1.08 +/- 0.1, all at the 95% confidence level. By combining our resul ts with measurements of high-redshift supernovae we constrain the value of the cosmological constant and the fractional amount of pressureless matter in the universe to 0.45 < <Omega>(Lambda) < 0.75 and 0.25 < Omega (m) < 0.5 0, at the 95% confidence level. Our results are consistent with a hat unive rse and the shape parameter deduced from large-scale structure, and in marg inal agreement with the baryon density from big bang nucleosynthesis.