The Work-Hamiltonian Connection and the Usefulness of the Jarzynski Equality for Free Energy Calculations

The connection between work and changes in the Hamiltonian for a system with a time-dependent Hamiltonian has recently been called into question, casting doubt on the usefulness of the Jarzynski equality for calculating free energy changes. In this paper, we discuss the relationship between two possible definitions of free energy and show how some recent disagreements regarding the applicability of the Jarzynski equality are the result of different authors using different definitions of free energy. Finally, in light of the recently raised doubts, we explicitly demonstrate that it is indeed possible to obtain physically relevant free energy profiles from molecular pulling experiments by using the Jarzynski equality and the results of Hummer and Szabo.Comment: 3 page

Description of quantum effects in the condensed phase

Recent experiments on light harvesting complexes have shown clear indication of coherent transport of excitations in these aggregates. We review the theoretical models that have been used to study energy transfer in molecular aggregates, beginning with the early models of Förster and Davydov. We cover the Redfield and Haken Strobl models in some detail, in order to set the nomenclature and because they are the most common and easiest models to understand and work with. We briefly discuss more complex models.United States. Dept. of Energy. Office of Basic Energy Sciences (Massachusetts Institute of Technology. Energy Frontier Research Center for Excitonics. Award DE-SC0001088

Cross-Examining Film

The Supreme Court decision in Scott v. Harris holds that a Georgia police officer did not violate a fleeing suspect\u27s Fourth Amendment rights when he caused the suspect\u27s car to crash. The court\u27s decision relies almost entirely on the filmed version of the high-speed police chase taken from a dash-cam, a video camera mounted on the dashboard of the pursuing police cruiser. The Supreme Court said that in light of the contrary stories told by the opposing parties to the lawsuit, the only story to be believed was that told by the video. In Scott v. Harris, the court fell into a dangerous and common trap of believing - to the point of enshrining in our law - that film captures reality. As Justice Breyer said in oral argument of the case seemingly flabbergasted by contrary findings below: I see with my eyes ... what happened, what am I supposed to do? The Supreme Court is not the first court to fall prey to the persuasive power of film. It is typical for courts and advocates to naively treat filmic evidence as a transparent window revealing the whole truth, as a presentation of unambiguous reality. But film has a history in art as a constructed medium. As filmmakers and critics have known since the beginning of cinema, film\u27s appearance of reality is an illusion, an illusion based on conventions of representation. How could Mr. Scott have countered the weight of the film and its persuasive power? When faced with prejudicial filmic evidence, how does an advocate undermine the assertive nature of film and its overwhelming appearance of exposure? The advocate must cross-examine the film the way she cross-examines witnesses. Because films are assertive in nature, an advocate faced with filmic evidence must treat it the way she treats other testimonial evidence, critically and with careful scrutiny. She must cross-examine the film. This article will set forth certain examination techniques using a piece of filmic evidence (linked to the article) from a recent case as an example. By doing so, it aspires to be a teaching tool for other courts and advocates in their treatment and consideration of filmic evidence