Rasulov, MahirUlas, S. Ozgur2024-03-132024-03-132015978-3-319-20239-6978-3-319-20238-90302-9743https://doi.org/10.1007/978-3-319-20239-6_36https://hdl.handle.net/20.500.12662/33176th International Conference on Finite Difference Methods - Theory and Applications (FDM - T and A) -- JUN 18-23, 2014 -- Lozenetz, BULGARIAIn this work, the exact solution of the Riemann problem for first-order nonlinear partial equation with non-convex state function in Q(T) = {(x, t)vertical bar x is an element of I = (-infinity, infinity), t is an element of [0, T)} subset of R-2 is found. Here F is an element of C-2 (Q(T)) and F '' (u) change their signs, that is F(u) has convex and concave parts. In particular, the state function F (u) = -cos u on [pi/2, 3 pi/2] and [pi/2, 5 pi/2] is discussed. For this, when it is necessary, the auxiliary problem which is equivalent to the main problem is introduced. The solution of the proposed problem permits constructing the weak solution of the main problem that conserves the entropy condition. In some cases, depending on the nature of the investigated problem a convex or a concave hull is constructed. Thus, the exact solutions are found by using these functions.eninfo:eu-repo/semantics/closedAccessFirst order nonlinear partial differential equationsRiemann problemCharacteristicsWeak solutionShock waveConvex and concave hullConference Object10.1007/978-3-319-20239-6_362-s2.0-84947087248339Q33329045WOS:000364326600036N/A