Can Quantum Effects Prevent Reaching Absolute Zero?

In summary, the article discusses the possibility of a supermassive black hole having a temperature of 10^-14 degrees Kelvin in an ideal, isolated setting. However, in our actual universe, the black hole would be continually absorbing CMBR radiation and its mass would be increasing. There is no minimum temperature theoretically, but reaching absolute zero becomes increasingly difficult as the temperature decreases. There are no known quantum effects that would prevent reaching absolute zero.
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nomadreid
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Do quantum effects as well as thermodynamic laws forbid zero Kelvin? Is there a non-zero greatest lower bound?
In https://phys.org/news/2016-09-cold-black-holes.html it is stated that a supermassive black hole interior could be 10^-14 degrees Kelvin. Is there a limit, perhaps due to quantum effects, below which a temperature (in a black hole or elsewhere) can go? Or do the possibilities approach 0 asymptotically, with only 0 being the theoretical minimum?

Putting it slightly differently: Usually the laws of thermodynamics are invoked to forbid absolute zero; in https://en.wikipedia.org/wiki/Absolute_zero, it is stated that one cannot reach absolute zero by thermodynamic means. Are there other means besides thermodynamic that could subtract energy, or are there quantum effects that would forbid it as well?
 
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nomadreid said:
In https://phys.org/news/2016-09-cold-black-holes.html it is stated that a supermassive black hole interior could be 10^-14 degrees Kelvin.
This would be true (assuming our current beliefs about Hawking radiation are correct) if the hole was alone in the universe, but it's not. In our actual universe, the hole would be, even if no other matter fell in, continually absorbing CMBR radiation at 2.7 K, so (a) its mass would be increasing, not decreasing, and (b) the Hawking temperature is not a good description of its actual conditions.

As usual, phys.org does not bother to mention all of the relevant items.

nomadreid said:
Is there a limit, perhaps due to quantum effects, below which a temperature (in a black hole or elsewhere) can go? Or do the possibilities approach 0 asymptotically, with only 0 being the theoretical minimum?
As far as I know, theoretically, there is no minimum and absolute zero can in principle be approached asymptotically. The practical issue is that the colder something is, the harder it gets to remove any more heat from it, with the difficulty increasing without bound as absolute zero is approached. I don't know of any quantum effects that change that.
 
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  • #3
Thanks for the very helpful reply, PeterDonis.
 
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nomadreid said:
Thanks for the very helpful reply, PeterDonis.
You're welcome!
 
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