second law of thermodynamics

There May Be A Loophole in the Second Law of Thermodynamics

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IN BRIEF
  • Scientists have formulated a mathematical theorem which shows that the Second Law of Thermodynamics may, at least, have a loophole.
  • The finding may provide the foundation for future discoveries that may allow us to power devices remotely.

BREAKING THE LAW

The Second Law of Thermodynamics states that entropy within an isolated system always increases. This iron-clad law has remained true for a very long time. However, researchers from the U.S. Department of Energy’s (DOE) Argonne National Laboratory may have found a way to violate this.

The foundation of this law is in the H-theorem, which states that if you open a door between two rooms, one hot and the other cold, both rooms’ temperature would eventually reach equilibrium making them both lukewarm.

While the H-theorem has been observed in a macroscopic level, scientists could not fully grasp its fundamental physical origin. In a study published in Scientific Reports, quantum information theory was able to offer a mathematical construct where entropy increases. It predicted that there are certain conditions where entropy might actually decrease in the short term.

“This allowed us to formulate the quantum H-theorem as it related to things that could be physically observed,” said Ivan Sadovskyy, a joint appointee with Argonne’s Materials Science Division and the Computation Institute and one of the authors on the paper. “It establishes a connection between well-documented quantum physics processes and the theoretical quantum channels that make up quantum information theory.”

Valerii Vinokur and Ivan Sadovskyy Credit: Mark Lopez/Argonne National Laboratory
Valerii Vinokur and Ivan Sadovskyy 

BUILDING THE IMPOSSIBLE

Their work is not the only one to theorize a violation of this law. In 1867, physicist James Clerk Maxwell designed a thought experiment where a hypothetical being would act as a sort of night club bouncer between the hot and cold room. That being, known as “Maxwell’s Demon,” would only let in particles of certain speeds. The study could “provide a platform for the practical realization of a quantum Maxwell’s demon,” says Valerii Vinokur, an Argonne Distinguished Fellow and the other author of the study

Vinokur hopes that this could lead into the creation of seemingly impossible machines like a local quantum perpetual motion machine. Another use he sees would be to apply the principles powering devices remotely. In the example he uses, a refrigerator would be able to be cooled at another location.

Does black-hole entropy make sense?

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Abstract

Bekenstein and Hawking saved the second law of thermodynamics near a black hole by assigning to the hole an entropySh proportional to the area of its event horizon. It is tempting to assume thatSh possesses all the features commonly associated with the physical entropy. Kundt has shown, however, thatSh violates several reasonable physical expectations. We review his criticism, augmenting it as follows: (a)Sh is a badly behaved state function requiring knowledge of the hole’s future history; and (b) close analogs of event horizons in other space-times do not possess an “entropy.” We also discuss these questions: (c) IsSh suitable for all regions of a black-hole space-time? And (b) shouldSh be attributed to the exterior of a white hole? One can retainSh for the interior (respectively, exterior) of a black (respectively, white) hole, but we reject this as contrary to the information-theoretic derivation of horizon entropy given by Bekenstein. The total entropy defined by Kundt (all ordinary entropy on space-section cutting through the hole, no horizon term) and that of Bekenstein-Hawking (ordinary entropy outside horizon plus horizon term) appear to be complementary concepts with separate domains of validity. In the most natural choice, an observer inside a black hole will use Kundt’s entropy, and one remaining outside that of Bekenstein-Hawking.