Origin of negative temperatures in systems interacting with external fields

abstract

• The controversial existence of negative temperatures has stirred interesting debates that have reached the foundations of thermodynamics, including questions on the second law, the Carnot efficiency and the statistical definition of entropy. Here we show that for systems interacting with an external field, negative temperatures arise from an energy mis-attribution in which the interaction energy with the field is treated as a form of internal energy. We discuss how negative temperatures are avoided when using a proper thermodynamic formalism, which accounts for the intensive and extensive variables associated to the external field. We use the paramagnetic system and a perfect gas in a gravitational field to illustrate these ideas. Considerations about the isothermal and adiabatic work done by the field or the system also shed light on the inconsistency of super-Carnot efficiencies.

authors

• Calabrese, Salvatore

published proceedings

• PHYSICS LETTERS A

altmetric score

• 0.5

author list (cited authors)

• Calabrese, S., & Porporato, A.

citation count

• 4

complete list of authors

• Calabrese, Salvatore||Porporato, Amilcare

publication date

• June 2019

publisher

• Elsevier  Publisher

published in

• Physics Letters, Section A: General, Atomic and Solid State Physics  Journal

keywords

• External Field
• Gravitational Field
• Ideal Gas
• Magnetic Field
• Negative Temperatures
• Paramagnetic System

Digital Object Identifier (DOI)

• 10.1016/j.physleta.2019.04.027

start page

• 2153

end page

• 2158

volume

• 383

issue

• 18

URL

• http://dx.doi.org/10.1016/j.physleta.2019.04.027