Abstract
In the present paper, several issues concerning the second law of thermodynamics, Maxwell's demon and Landauer's principle are dealt with. I argue that if the demon and the system on which it operates without dissipation of external energy are made of atoms and molecules (gas, liquid or solid) in thermal equilibrium (whose behaviour is described by a canonical distribution), then the unavoidable reason why the demon cannot successfully operate resides in the ubiquity of thermal fluctuations and friction. Landauer's principle appears to be unnecessary. I also suggest that if the behaviour of the demon and the system on which it acts is not always describable by a canonical distribution, as would happen for instance with the ballistic motion of electrons at early stages of thermionic emission, then a successful working demon cannot be ruled out a priori. A critical review of two recent experiments on thermionic emission Maxwell's demons is also given.
Highlights
Classical thermodynamics was essentially born in the nineteenth century and its original goal was to understand the fundamental principles that underlie the operation of heat engines with the aim of making them as effective as possible.Heat engines are machines having almost always a gas as working substance and performing cyclic transformations on the Pressure–Volume (P V ) diagram
If the demon and the system on which it operates without dissipation of external energy are made of atoms and molecules in thermal equilibrium, the fluctuations/friction exorcism is unavoidable
I have shown that if one only deals with classical thermodynamics, i.e., with a gas, a system status defined by macroscopic variables V, P, T and transformations on a P V diagram, the second law in the Kelvin–Planck formulation is true by necessity
Summary
Classical thermodynamics was essentially born in the nineteenth century and its original goal was to understand the fundamental principles that underlie the operation of heat engines with the aim of making them as effective as possible (note that the 1824 seminal work by Sadi Carnot, who is considered as the father of thermodynamics, deals with heat, power energy and engine efficiency). The work WA1 →B externally done to the gas is equal to kT ln 2, which is equal to the heat transferred by the gas to the heat reservoir at temperature T Note that this part of the cycle is independent of which side of the partition the molecule is on at step A1 , we do not need any information acquisition (with subsequent memory erasure). If information acquisition and/or memory erasure entropy costs are strictly necessary to defeat original Szilard’s engine, this means that no other mechanisms are able to prevent its operation. The true reason why the demon cannot operate, namely cannot macroscopically violate the second law and create usable work, is the ubiquity of thermal fluctuations and friction in the physical matter, the matter that inevitably constitutes both gas and every device conceived to sort molecules. Norton in a recent paper [4]
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