Absolute hot is a concept of temperature that postulates the existence of a highest attainable temperature of matter. The concept has been popularized by the television series Nova. In this presentation, absolute hot is assumed to be the high end of a temperature scale starting at absolute zero, which is the temperature at which entropy is minimal and classical thermal energy is zero.
Contemporary models of physical cosmology postulate that the highest possible temperature is the Planck temperature, which has the value 1.416785(71)×1032 kelvin. Above ~1032K, particle energies become so large that gravitational forces between them would become as strong as other fundamental forces according to current theories. There is no existing scientific theory for the behavior of matter at these energies. A quantum theory of gravity would be required. The models of the origin of the universe based on the Big Bang theory assume that the universe has passed through this temperature about 10−42 seconds after the Big Bang as a result of enormous entropy expansion.
Another theory of absolute hot is based on the Hagedorn temperature, where the thermal energies of the particles exceed the mass-energy of a hadron particle-antiparticle pair. Instead of temperature rising, at the Hagedorn temperature more and heavier particles are produced by pair production, thus preventing effective further heating, given that only hadrons are produced. However, further heating is possible (with pressure) if the matter undergoes a phase change into a quark–gluon plasma. For hadrons, the Hagedorn temperature is 2 × 1012 K, which has been reached and exceeded in LHC and RHIC experiments. However, in string theory, a separate Hagedorn temperature can be defined, where strings similarly provide the extra degrees of freedom. However, it is so high (1030 K) that no current or foreseeable experiment can reach it.
Quantum physics formally assumes infinitely positive or negative temperatures in descriptions of spin system undergoing population inversion from the ground state to a higher energy state by excitation with electromagnetic radiation. The temperature function in these systems exhibits a singularity, meaning the temperature tends to positive infinity, before discontinuously switching to negative infinity. However, this applies only to specific degrees of freedom in the system, while others would have normal temperature dependency. If equipartitioning were possible, such formalisms ignore the fact that the spin system would be destroyed by the decomposition of ordinary matter before infinite temperature could be reached uniformly in the sample.
- International Temperature Scale of 1990
- Negative temperature
- Orders of magnitude (temperature)
- Thermodynamic temperature
- PBS. "Absolute zero." NOVA. Season 33. Ep. 1.
- Absolute Hot. NOVA.
- Tyson, Peter (2007). "Absolute Hot: Is there an opposite to absolute zero?". PBS.org. Archived from the original on 6 August 2009. Retrieved 2009-08-11.
- Hubert Reeves (1991). The Hour of Our Delight. W. H. Freeman Company. p. 117. ISBN 0-7167-2220-8.
The point at which our physical theories run into most serious difficulties is that where matter reaches a temperature of approximately 1032 degrees, also known as Planck's temperature. The extreme density of radiation emitted at this temperature creates a disproportionately intense field of gravity. To go even farther back, a quantum theory of gravity would be necessary, but such a theory has yet to be written.
- Atick, Joseph J.; Witten, Edward. "The Hagedorn transition and the number of degrees of freedom of string theory". Nuclear Physics B. Elsevier. Retrieved 17 February 2014.
- C. Kittel, H. Kroemer (1980). Thermal Physics (2 ed.). W. H. Freeman Company. ISBN 0-7167-1088-9.