Publication: Ratchets brownianas retroalimentadas e información
Loading...
Files
Official URL
Full text at PDC
Publication Date
2010-05-17
Authors
Advisors (or tutors)
Editors
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad Complutense de Madrid, Servicio de Publicaciones
Citations
Exportar
Abstract
Las ratchets o motores brownianos pueden verse como controladores que actúan sobre sistemas estocásticos con el objetivo de inducir movimiento neto a través de la rectificación de las fluctuaciones. En la presente tesis investigamos ratchets de ciclo cerrado o retroalimentadas, que son aquellas ratchets cuyo mecanismo de rectificación depende explícitamente del estado del sistema. Hemos analizado la dinámica y el rendimiento de ratchets con control retroalimentado centrándonos en lo que las caracteriza, a saber, el uso de la información sobre el estado del sistema. Hemos mostrado que este uso de la información permite a las ratchets de ciclo cerrado incrementar el rendimiento sobre sus análogas de ciclo abierto.
Además, la investigación sobre los efectos del retardo temporal en la retroalimentación nos revela una dinámica rica que exhibe multiestabilidad e inversiones de corriente. Estos estudios que hemos hecho sobre los efectos del retardo temporal junto con los efectos de ruidos en el control retroalimentado nos muestran la viabilidad de realizaciones experimentales de las ratchets retroalimentadas. También hemos encontrado que la combinación de una fuerza oscilante de media cero con el mecanismo de control conduce al máximo flujo que se ha obtenido en una ratchet sin un sesgo a priori. Por otra parte, en esta tesis hemos completado la termodinámica de sistemas generales con control retroalimentado calculando la reducción de entropía cuando el sistema es operado repetidamente por el controlador. Este era el ingrediente que faltaba para establecer la termodinámica de los sitemas con control retroalimentado, y en particular de los demonios de Maxwell. Finalmente, presentamos algunas cuestiones todavía abiertas y futuras perspectivas en el emergente campo de las ratchets retroalimentadas.
Ratchets or Brownian motors can be viewed as controllers that act on stochastic systems with the aim of inducing directed motion through the rectification of fluctuations. In the present thesis, we investigate closed-loop or feedback controlled ratchets, which are those ratchets whose rectification action has an explicit dependence on the state of the system. We have analyzed the dynamics and performance of feedback controlled ratchets focusing on what characterizes them, namely, the use of information about the state of the system. We have shown that this use of information is what allows closed-loop ratchets to increase the performance over their open-loop counterparts. In addition, our research on the effects of time delay in the feedback has revealed a rich dynamics exhibiting multistability and current reversals. These studies of the effects of time delay together with the effects of noise in the feedback have shown the viability of experimental realizations of feedback controlled ratchets. We have also found that the combination of a zero-mean oscillating force with the feedback mechanism leads to the maximum flux that has been achieved in a ratchet device without an a priori bias. On the other hand, in this thesis we have completed the thermodynamics of general feedback controlled systems by computing the entropy reduction when the system is repeatedly operated by the controller. This was the lacking ingredient to establish the thermodynamics of feedback controlled systems, and in particular of Maxwell’s demons. Finally, we present some still open questions and future perspectives in the new emerging field of feedback ratchets.
Ratchets or Brownian motors can be viewed as controllers that act on stochastic systems with the aim of inducing directed motion through the rectification of fluctuations. In the present thesis, we investigate closed-loop or feedback controlled ratchets, which are those ratchets whose rectification action has an explicit dependence on the state of the system. We have analyzed the dynamics and performance of feedback controlled ratchets focusing on what characterizes them, namely, the use of information about the state of the system. We have shown that this use of information is what allows closed-loop ratchets to increase the performance over their open-loop counterparts. In addition, our research on the effects of time delay in the feedback has revealed a rich dynamics exhibiting multistability and current reversals. These studies of the effects of time delay together with the effects of noise in the feedback have shown the viability of experimental realizations of feedback controlled ratchets. We have also found that the combination of a zero-mean oscillating force with the feedback mechanism leads to the maximum flux that has been achieved in a ratchet device without an a priori bias. On the other hand, in this thesis we have completed the thermodynamics of general feedback controlled systems by computing the entropy reduction when the system is repeatedly operated by the controller. This was the lacking ingredient to establish the thermodynamics of feedback controlled systems, and in particular of Maxwell’s demons. Finally, we present some still open questions and future perspectives in the new emerging field of feedback ratchets.
Description
Tesis de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física Atómica, Molecular y Nuclear, leída el 22-10-2009