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Is There Such a Thing As Absolute Hot?
AlpineR writes "Is there an opposite to absolute zero? An article from PBS's NOVA online explains several theories of the maximum possible temperature. Maybe it's the Planck temperature, 10^32 K, beyond which the known laws of physics break down. Or maybe just 10^30 K, the limit of some versions of string theory. If space is actually 11-dimensional then the maximum temperature could even be as low as 10^17 K, attainable by the Large Hadron Collider. Or maybe infinite temperature wraps around to negative temperature and absolute hot is the same as absolute cold."
Temperature is basically the average kinetic energy of the particles, and kinetic energy is half the mass times velocity squared, when things start to get very hot, the particles would eventually start getting up to relativistic speeds.
This has lead some people to suggest that the cosmic speed limit (the speed of light) imposes a cosmic temperature limit - but that's NOT the case.
As things start to move closer and closer to the speed of light, relativity says that their mass increases (as seen from the perspective of an outside observer). Whilst there is a cosmic speed limit - as you approach it, your mass increases without limit. Since unlimited mass and finite velocity means unlimited kinetic energy, relativity does not impose a cosmic temperature limit.
If there is a cosmic temperature limit, it's caused by something else.
www.sjbaker.org
But no one has tied relativity to quantum mechanics yet. Therefore those speed limits only apply to a narrow vision of the universe.
Sorry but Special Relativity and Quantum Mechanics are very well integrated: it was first done by Dirac in ~1932 and led to the prediction of anti-matter which was discovered a few years later with the positron (anti-electron). The Dirac (along with the Klein-Gordon and Proca) equations form the underpinnings of Quantum Field Theory which is what we use in particle physics to describe all the fundamental particles of nature (that we know of) and how they interact (except via gravity). This has Lorentz invariance built into it and is a complete union of QM and SR.
What is harder is to unify QM and GR. This has not been successfully done yet. You can create a quantized gravitational field relatively easily but the problem is that you have to specify a maximum energy scale in order to normalize it (in 3+1D at least). This is bad because there is no justification for a maximum energy scale once you include gravity where the physics will change. Hence either the theory is wrong or there is something else at some really high energy. In either case you cannot use it to make meaningful predictions and so we say we have no valid way, yet, to unify QM nd GR.