Entropy

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In a study published in Physical Review Letters, physicists have demonstrated that black holes satisfy the third law of thermodynamics, which states that entropy remains positive and vanishes at extremely low temperatures, just like ordinary quantum systems. The finding provides strong evidence that black holes possess isolated ground states, a hallmark of quantum mechanical behavior.

Prior calculations showed that black hole entropy might become negative at low temperatures, a result that appeared physically puzzling. In this work, researchers addressed the paradox by incorporating wormhole effects in the two-dimensional Jackiw-Teitelboim (JT) gravity model.

In quantum systems, entropy measures the number of possible microscopic configurations. If a system has an isolated ground state—a unique lowest energy configuration—its entropy should vanish as temperature approaches absolute zero.

https://phys.org/news/2025-11-probing-quantum-nature-black-holes.html

Hydrodynamics theory offers quantum physicists with an alternative route for simulating the interactions between particles in large systems. If a system is chaotic, in fact, researchers can assume that the particles will interact in ways that will ensure a state of local thermal equilibrium.

"Quantum systems are fundamentally different from their classical counterparts because their constituent particles can exhibit quantum phenomena like entanglement, which defy everyday intuition," said Wienand. "They are also much harder to calculate, so being able to describe them using FHD could help us understand such systems better and make predictions about them."

https://phys.org/news/2024-09-team-emergence-fluctuating-hydrodynamics-chaotic.html

On the other hand, studying the dynamics of individual microscopic degrees of freedom comprehensively becomes too cumbersome even when considering systems of a moderate number of particles. To describe the interface between these opposite ends of the scale, stochastic field theories are commonly used to characterize the dynamics of complex systems and the effect of the microscopic fluctuations.

https://phys.org/news/2025-11-randomness.html