@article{oai:kanazawa-u.repo.nii.ac.jp:00008693,
 author = {Komatsu, Nobuyoshi and Kimura, Shigeo and Kiwata, Takahiro},
 issue = {4},
 journal = {Physical Review E - Statistical, Nonlinear, and Soft Matter Physics},
 month = {Oct},
 note = {Gravity-dominated systems have a negative specific heat. We investigate the negative specific heat of self-gravitating systems enclosed in a spherical container with reflecting walls by means of N -body simulations. To simulate nonequilibrium processes, a particle reflected at a nonadiabatic wall is cooled to mimic energy loss by reflecting walls, while an adiabatic wall is employed for microcanonical ensembles. We show that a negative specific heat occurs not only in the microcanonical ensemble but also in certain nonequilibrium processes with the nonadiabatic wall. With increasing cooling rates, the dependence of temperature T on energy ε, i.e., the ε- T curve, gradually deviates from the microcanonical ensemble and approaches a certain common curve at a low-energy region. The common curve agrees with an ε- T curve for stellar polytropes, especially for the polytrope index of n∼5. We show that the stellar polytrope should be related to the present nonequilibrium process appearing in the self-gravitating system with the nonadiabatic wall. In the nonequilibrium process, a rapid change in velocity at the nonadiabatic wall significantly affects the velocity and density profiles. In particular, the greater the cooling rate, the greater the local velocity gradient at a low-energy region. © 2009 The American Physical Society., 金沢大学理工研究域機械工学系, 金沢大学環日本海域環境研究センターエコテクノロジー研究部門},
 title = {Negative specific heat in self-gravitating N -body systems enclosed in a spherical container with reflecting walls},
 volume = {80},
 year = {2009}
}