If the spatial section of the universe is multiply connected, repeated images or patterns are expected to be detected observationally. However, due to the finite distance to the last scattering surface, such pattern repetitions could be unobservable. This raises the question of whether a given cosmic topology is detectable, depending on the values of the parameters of the cosmological model. We...

A Chaplygin gas is an inviscid, compressible fluid in which the acoustic fields are linearly degenerate. We analyse the multi-dimensional shocks, which turn out to be sonic. Two shocks in general position interact rather simply. We investigate several twodimensional Riemann problems and prove the existence of a unique solution. Among them is the supersonic reflection of a planar shock against a...

We consider the generalized Chaplygin gas (GCG) proposal for unification of dark energy and dark matter and show that it admits an unique decomposition into dark energy and dark matter components once phantom-like dark energy is excluded. Within this framework, we study structure formation and show that difficulties associated to unphysical oscillations or blow-up in the matter power spectrum c...

Luis P. Chimento, Alejandro S. Jakubi, and Diego Pavón Departamento de F́ısica, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina Departamento de F́ısica, Universidad Autónoma de Barcelona, 08193 Bellaterra, Spain Abstract In a recent paper we showed that a quintessence scalar field plus a dissipative matter fluid can drive late cosmic accelerated expansion and simultaneously solve the co...

We investigate the cosmological evolution for physical parameters in Weyl integrable gravity a Friedmann–Lemaître–Robertson–Walker universe with zero spatial curvature. For matter component, we assume that it is an ideal gas, and of Chaplygin from scalar field introduced by geometric approach which provides interaction component.We calculate stationary points equations study their stability pro...

We constructively solve the piston problem for one-dimensional isentropic Euler equations a modified Chaplygin gas. give rigorous proof of global existence and uniqueness shock wave separating constant states ahead when advances into The results are quite different from those pure gas or generalized gas, in which Radon measure solution is constructed to deal with concentration mass on piston. W...