Bank Runs Without Sunspots

The literature on bank runs reduces all coordination mechanisms triggering attacks on banks to exogenous sunspots. We present a general equilibrium version of these models where the uncertainty faced by depositors is modeled explicitly, such that bank runs arise as optimal equilibrium outcomes corresponding to Bayesian coordination games played by rational agents before depositing. Differentials in information sets between the bank and its depositors lead to rational self-contained equilibrium runs. The coexistence of different beliefs in equilibrium jointly with the self-fulfilling nature of the attacks follow from Adam Smith's invisible hand principle. The runs obtained do not violate the revelation principle.La literatura sobre pánicos bancarios reduce todo mecanismo de coordinación que de lugar a los ataques a puntos solares exógenos. Presentamos una versión de equilibrio general de dichos modelos en la cual la incertidumbre a la que los agentes económicos se hallan sujetos es modelizada de forma explícita, de manera que los pánicos surgen como resultados óptimos de equilibrio correspondientes a juegos de coordinación Bayesianos jugados por agentes racionales antes de depositar sus fondos en el banco. Diferencias en los conjuntos de información entre el banco y sus clientes dan lugar a pánicos racionales autocontenidos en equilibrio. La coexistencia de diversas creencias probabilísticas en equilibrio, así como la naturaleza auto-contenida de los ataques, derivan del principio de la mano invisible de Adam Smith. Los pánicos obtenidos no violan el principio de revelación.Bank runs, Self-contained attacks, Bayesian coordination games, Revelation principle, Invisible hand principle, Pánicos bancarios, Ataques autocontenidos, Juegos de coordinación Bayesianos, Principio de revelación, Principios de la mano invisible.

Description of nuclear systems with a self-consistent configuration-mixing approach. I: Theory, algorithm, and application to the 12^{12}C test nucleus

Although self-consistent multi-configuration methods have been used for decades to address the description of atomic and molecular many-body systems, only a few trials have been made in the context of nuclear structure. This work aims at the development of such an approach to describe in a unified way various types of correlations in nuclei, in a self-consistent manner where the mean-field is improved as correlations are introduced. The goal is to reconcile the usually set apart Shell-Model and Self-Consistent Mean-Field methods. This approach is referred as "variational multiparticle-multihole configuration mixing method". It is based on a double variational principle which yields a set of two coupled equations that determine at the same time the expansion coefficients of the many-body wave function and the single particle states. The formalism is derived and discussed in a general context, starting from a three-body Hamiltonian. Links to existing many-body techniques such as the formalism of Green's functions are established. First applications are done using the two-body D1S Gogny effective force. The numerical procedure is tested on the $^{12}$C nucleus in order to study the convergence features of the algorithm in different contexts. Ground state properties as well as single-particle quantities are analyzed, and the description of the first $2^+$ state is examined. This study allows to validate our numerical algorithm and leads to encouraging results. In order to test the method further, we will realize in the second article of this series, a systematic description of more nuclei and observables obtained by applying the newly-developed numerical procedure with the same Gogny force. As raised in the present work, applications of the variational multiparticle-multihole configuration mixing method will however ultimately require the use of an extended and more constrained Gogny force.Comment: 22 pages, 18 figures, accepted for publication in Phys. Rev. C. v2: minor corrections and references adde