Discrete and Continuous Models and Applied Computational ScienceDiscrete and Continuous Models and Applied Computational Science2658-46702658-7149Peoples' Friendship University of Russia named after Patrice Lumumba (RUDN University)8831Conference Report, Theses of ReportRiemann’s Wavesin Chaplygin GasVilca ChaichaM BDepartment of Theoretical Physics-RybakovYu PDepartment of Theoretical Physicssoliton4@mail.ruShikinG NDepartment of Theoretical Physics-Peoples’ Friendship University of Russia15042012410310908092016Copyright © 2012,2012We have investigated propagation of Riemann waves in an ideal ﬂuid with negative pressure, the so-called Chaplygin gas. We consider barotropic motion of the medium when the pressure is P = P( ρ) in the assumption u = u( ρ), where u — the velocity, ρ — density of the medium. The system of hydrodynamic equations then reduces to a wave equation of the ﬁrst order, which describes a wave with variable speed. It is shown that these waves have deformed proﬁle, which leads to an ambiguous deﬁnition of ρ. In order to remove this lack in the original equation we have introduced a member with the second derivative, which leads to the appearance of waves with a stationary proﬁle which is a rarefaction wave.state equationChaplygin gasrarefaction wavesуравнение состояниягаз Чаплыгинаволны разрежения