arXiv subjects
Publications and source records attributed to Pablo Castañeda.
The present work focuses on the study of the renowned Collatz conjecture, also known as the $3x +1$ problem. The distinguished analysis approach lies on the dynamics of an iterative map in binary form. A new estimation of the enlargement of iterated numbers is given. Within the associated iterative map, characteristic periods for periodic orbits are identified.
In 1977 Korchinski presented a new type of shock discontinuity in conservation laws. These singular solutions were coined $δ$-shocks since there is a time dependent Dirac delta involved. A naive description is that such $δ$-shock is of the overcompressive type: a two-family shock wave the four characteristic lines of which impinge into the shock itself. In this work, we open the fan of solutions by studying two-family waves without intermediate constant states but, possessing central rarefactions and also comprising $δ$-shocks.
For a family of Riemann problems for systems of conservation laws, we construct a flux function that is scalar and is capable of describing the Riemann solution of the original system.
This paper deals with a hyperbolic system of two nonlinear conservation laws, where the phase space contains two contact manifolds. The governing equations are modelling bidisperse suspensions, which consist of two types of small particles that are dispersed in a viscous fluid and differ in size and viscosity. For certain parameter choices quasi-umbilic points and a contact manifold in the interior of the phase space are detected. The dependance of the solutions structure on this contact manifold is examined. The elementary waves that start in the origin of the phase space are classified. Prototypic Riemann problems that connect the origin to any point in the state space and that connect any state in the state space to the maximum line are solved semi-analytically.