Radiation thermodynamics and cosmic string thermodynamics

What is it about?

The paper related thermodynamics of photons to thermodynamics of cosmic string loops. The energy of photons is inversely proportional to their "size" (their wavelength) whereas the energy of comic string is proportional to their "size" (their length). This microscopic symmetry leads to a duality symmetry in the respective thermodynamic behaviours of photon gases and cosmic loops gases, which is explored in the paper. For instance, entropy per unit volume is proportional to the cube of temperature T in photon gases and inversely proportional to the cube of T in cosmic loop gases, and the pressure of photon gases is 1/3 of their energy density and that of cosmic loops gases is proportional to -1/3 of their energy density.

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Why is it important?

It relates in a simple way the microscopic symmetry between entities whose energy is inversely proportional to their size (photons) and entities whose energy is proportional to their size (cosmic string loops), to a series of symmetry relations between their respective thermodynamic behaviours. It turns out that photons and cosmic strings are mutually dual, the temperature of the former ones varying as 1/R with R a characteristic cosmic size, and the temperature of the latter varying as R. This may set a duality relation between the thermodynamic behaviour of the early universe, dominated by photons, and the old universe, dominated by cosmic string loops

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