We study numerically the effect of varying the equation of state ( EOS ) on the formation of stellar clusters in turbulent molecular clouds .
Our results show that the EOS plays an important role in the fragmentation of the clouds , and the determination of the initial mass function ( IMF ) of the protostellar cores .
Fragmentation decreases with increasing adiabatic index \gamma in the range 0.2 < \gamma < 1.4 , although the total amount of mass accreted appears to remain roughly constant through that range , resulting in more massive cores at higher \gamma .
Fragmentation and collapse ceases entirely for \gamma > 1.4 as expected from analytic arguments .
Primordial gas may have effective \gamma > 1 , in which case these results may help explain why models of the formation of the first stars produce isolated , massive objects .