Related Experiment Video
Updated: Nov 27, 2025
11:00
Experimental Investigation of Secondary Flow Structures Downstream of a Model Type IV Stent Failure in a 180° Curved Artery Test Section
Published on: July 19, 2016
11.8K
Comment on "Black Hole Entropy: A Closer Look"
Pedro Pessoa1, Bruno Arderucio Costa2
1Department of Physics, University at Albany (SUNY), Albany, NY 12222, USA.
Entropy (Basel, Switzerland)
|December 8, 2020
Summary
Standard entropy definitions are adequate for black hole entropy. This study clarifies the difference between additivity and extensivity, crucial for understanding black hole thermodynamics.
Area of Science:
- Thermodynamics
- Black Hole Physics
- Information Theory
Background:
- Tsallis's recent paper (Entropy 2020) questions the adequacy of Shannon and Kullback-Leibler entropy for black hole thermodynamics.
- Tsallis proposes a new non-additive functional to replace conventional entropy in this context.
Purpose of the Study:
- To counterargue Tsallis's claims regarding black hole entropy.
- To clarify the fundamental properties of entropy, specifically additivity versus extensivity.
- To address other debatable points in Tsallis's analysis of black hole entropy.
Main Methods:
- Conceptual analysis and theoretical argumentation.
- Distinguishing between the properties of additivity and extensivity.
- Critiquing specific statements in Tsallis's paper.
Main Results:
- Additivity is a fundamental property of entropy, essential for its definition.
- Extensivity is a property of specific thermodynamic systems, not a universal requirement for entropy.
- Black hole entropy does not necessarily need to be extensive.
Conclusions:
- Shannon and Kullback-Leibler entropy definitions remain valid for black hole entropy.
- The distinction between additivity and extensivity is key to understanding black hole thermodynamics.
- Tsallis's assertions about the inadequacy of current entropy measures for black holes are debatable.
Related Concept Videos
01:10Detection of Black Holes
2.4K
Although black holes were theoretically postulated in the 1920s, they remained outside the domain of observational astronomy until the 1970s.
Their closest cousins are neutron stars, which are composed almost entirely of neutrons packed against each other, making them extremely dense. A neutron star has the same mass as the Sun but its diameter is only a few kilometers. Therefore, the escape velocity from their surface is close to the speed of light.
Not until the 1960s, when the first neutron...
Their closest cousins are neutron stars, which are composed almost entirely of neutrons packed against each other, making them extremely dense. A neutron star has the same mass as the Sun but its diameter is only a few kilometers. Therefore, the escape velocity from their surface is close to the speed of light.
Not until the 1960s, when the first neutron...
2.4K
02:39Entropy
33.6K
Salt particles that have dissolved in water never spontaneously come back together in solution to reform solid particles. Moreover, a gas that has expanded in a vacuum remains dispersed and never spontaneously reassembles. The unidirectional nature of these phenomena is the result of a thermodynamic state function called entropy (S). Entropy is the measure of the extent to which the energy is dispersed throughout a system, or in other words, it is proportional to the degree of disorder of a...
33.6K
01:18Entropy
3.2K
The first law of thermodynamics is quantitatively formulated via an equation relating the internal energy of a system, the heat exchanged by it, and the work done on it. A quantitative formulation of the second law of thermodynamics leads to defining a state function, the entropy.
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...
3.2K
01:21Schwarzschild Radius and Event Horizon
2.4K
No object with a finite mass can travel faster than the speed of light in a vacuum. This fact has an interesting consequence in the domain of extremely high gravitational fields.
The minimum speed required to launch a projectile from the surface of an object to which it is gravitationally bound so that it eventually escapes the object’s gravitational field is called the escape velocity. The escape velocity is independent of the mass of the object. Merging the idea of escape...
The minimum speed required to launch a projectile from the surface of an object to which it is gravitationally bound so that it eventually escapes the object’s gravitational field is called the escape velocity. The escape velocity is independent of the mass of the object. Merging the idea of escape...
2.4K
01:20Entropy and the Second Law of Thermodynamics
3.9K
The second law of thermodynamics can be stated quantitatively using the concept of entropy. Entropy is the measure of disorder of the system.
The relation between entropy and disorder can be illustrated with the example of the phase change of ice to water. In ice, the molecules are located at specific sites giving a solid state, whereas, in a liquid form, these molecules are much freer to move. The molecular arrangement has therefore become more randomized. Although the change in average...
The relation between entropy and disorder can be illustrated with the example of the phase change of ice to water. In ice, the molecules are located at specific sites giving a solid state, whereas, in a liquid form, these molecules are much freer to move. The molecular arrangement has therefore become more randomized. Although the change in average...
3.9K
01:10Entropy Change in Reversible Processes
3.0K
In the Carnot engine, which achieves the maximum efficiency between two reservoirs of fixed temperatures, the total change in entropy is zero. The observation can be generalized by considering any reversible cyclic process consisting of many Carnot cycles. Thus, it can be stated that the total entropy change of any ideal reversible cycle is zero.
The statement can be further generalized to prove that entropy is a state function. Take a cyclic process between any two points on a p-V diagram.
The statement can be further generalized to prove that entropy is a state function. Take a cyclic process between any two points on a p-V diagram.
3.0K