Andrew F. Rex

Resource Letter MD‐1: Maxwell’s demon

This Resource Letter provides a comprehensive guide to the voluminous literature that has developed around Maxwell’s demon, and offers a perspective on issues for which the hypothetical character Maxwell introduced over 120 years ago has inspired continuing research and debate. The code (E) indicates elementary level or general interest material useful to persons just learning the field; (I) indicates intermediate level or somewhat specialized material; and (A) indicates advanced or highly specialized material. No accompanying AAPT reprint book will be available, because an extensive reprint collection (Ref. 29) edited by the authors will be published separately.

Entropy of measurement and erasure: Szilard’s membrane model revisited

It is widely believed that measurement is accompanied by irreversible entropy increase. This conventional wisdom is based in part on Szilard’s 1929 study of entropy decrease in a thermodynamic system by intelligent intervention (i.e., a Maxwell’s demon) and Brillouin’s association of entropy with information. Bennett subsequently argued that information acquisition is not necessarily irreversible, but information erasure must be dissipative (Landauer’s principle). Inspired by the ensuing debate, we revisit the membrane model introduced by Szilard and find that it can illustrate and clarify (1) reversible measurement, (2) information storage, (3) decoupling of the memory from the system being measured, and (4) entropy increase associated with memory erasure and resetting.

The effect of spin on the flight of batted baseballs

Distances traveled by batted baseballs with various spin types and rates have been calculated using a computer. It is found that balls hit with backspin tend to travel farther than balls hit with little spin or topspin, particularly for lower trajectories. Two types of hits are considered specifically: the long fly ball of potential home run distance and the low line drive to the outfield.

The Improvement of Mossbauer Spectra by FIRO Deconvolution

A deconvolution method similar to that used by Shimokoshi, Kanzaki, and Jones [Applied Spectroscopy 39, 1014 (1985)] has been used to study 57Fe Mossbauer spectra containing various mixtures of iron compounds. In all cases the spectra studied contained one or more sets of overlapping spectral lines. The resolution of these overlapping lines can often be improved by deconvolution to the point at which the integrated intensities of the deconvoluted peaks provide reliable information about sample concentrations. A comparison of the results which can be obtained for different deconvolution parameters and different degrees of overlapping is presented.

Entropy And Information For An Automated Maxwell's Demon

Andy Rex Ross Larsen Physics Department University of Puget Sound Tacoma, WA 98416 In an attempt to create a Maxwells demon that does not depend on information, we have developed a computational simulation of a demon that uses an automated, refrigerated trapdoor. We keep track of and compare the entropy reduction by the demon and tlhe entropy cost of running the

The operation of Maxwell’s demon in a low entropy system

The problem of Maxwell’s sorting demon traditionally has been studied for the case in which the hot and cold regions differ very little in temperature. In this article a solution is presented for the case in which the temperature difference is great so that the total entropy is lower. Calculations indicate that in this case the demon must use a large number of photons to observe the proper kinds of particles. This causes an increase in entropy which more than offsets the decrease caused by an exchange of particles.

Maxwell's Demon And The Second Law

Maxwell’s demon emanates from a thought experiment proposed by James Clerk Maxwell in 1867 to illustrate the statistical nature of the second law of thermodynamics. Subsequently researchers wondered whether such a demon could in fact violate the second law. Leon Brillouin argued that the entropy produced during the demon’s measurement precluded such a violation. Years later Oliver Penrose and Charles Bennett observed (independently) that a Maxwell’s demon gathers information and stores it in a memory. Penrose showed that erasure of such a memory sends sufficient entropy to the environment to preclude violation of the second law. Notably this is so even when measurement produces arbitrarily little entropy. Bennett obtained the same result using Rolf Landauer’s seminal research on the thermodynamics of computation. The stunning shift in focus from measurement to erasure provided the impetus to better understand the role of information in quantum mechanics and thermodynamics. Indeed the linkage of informatio...

On the Use of a Gauss Filter in the Deconvolution of Lorentzian Spectral Lines

It is well known that when the FIRO deconvolution method is used, maximum resolution enhancement results from self-deconvolution, e.g., when a Lorentz filter is used to deconvolute a mostly Lorentzian line shape [Applied Spectroscopy 35, 271 (1981)]. Unfortunately, self-deconvolution can also distort the line shape and introduce side lobes. In this paper it is shown that a Gauss filter can be used to deconvolute a Lorentzian line or lines and produce some resolution enhancement without significantly distorting the line shape or introducing other undesirable features.