Maxwell Demon: Who said it is useless?

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Since the invention of steam engines has opened up the global industrialization process, the second law of thermodynamics dominates physics, chemistry, engineering and biology. And now it is an upgrade.

The discipline of energy -thermodynamics was born in the nineteenth century, and in the industrial revolution, it appeared with the continuous improvement of steam engines in the industrial revolution. In order to understand the second law of thermodynamics, we assume that a sponge cake that has just been released is placed on the stove to cool down, and the fragrance molecules carrying heat spread out of the cake outward. Physicists may be curious: How many ways do these molecules have in the volume of their current space? We call the number of distribution methods as entropy of these molecules. If the occupied space is only near the cake (such as when the cake is just released), then the entropy is relatively small; if the occupied space is full of the entire kitchen (the molecule has enough time to float a long distance), the entropy will show the index index Grade increase. The second law of thermodynamics pointed out that the entropy of any closed isolation system (such as the kitchen here, assuming that doors and windows are closed) will not decrease. Therefore, the fragrance of the cake will be filled with the entire kitchen without shrinking back to the cake.

We attribute these behaviors of the molecules to an independent style: < /g> , of which is the initial entropy of these smell molecules, and Essence This inequality is very useful but not clear, because in most cases it does not tell us how much entropy will increase, except for a special case: molecules are in a balanced state. The balanced state means that the macro nature of temperature and volume remains unchanged, and there is no net flow of any physical quantities such as energy or particles to enter or leave the system. For example, when the aroma of the cake is completely full of the entire kitchen, they reach a balanced state. In balanced state, the second law of thermodynamics is strengthened to one equal form: < g data-mml-node = "math"> < /g> . This concise and general equation provides accurate information for many balanced and thermodynamics systems.

But most of you, me, and most things in the world are far from balanced state. "Non -balanced state" is a gray zone for theoretical physicists and chemists: difficult to predict and complex and disorderly. For us, it is very difficult to prove that the law of the non -balanced state is like applying the rules to the gray area. Although it is difficult, it is not unable to achieve it. For decades, physicists have been studying some equivalences that can further verify the correctness of the second law of thermodynamics. These equivalent is called the rise and fall relationship. They will be far away from the balance of the balance (difficult to explain in theoretical).

In order to observe the role of ups and downs, assuming that there is a tiny DNA chain floating on the water. When DNA floats calmly, it is in a balanced state and has the same temperature as water. Use laser to fix one end of the DNA chain to stretch the other end. The stretching of the chain will make it leave the balance state. This needs to be done. The significance of the function in physics is to use structured energy to complete useful tasks. Because water molecules randomly impact the DNA chain, the energy required to pull the DNA chain multiple times is not fixed. This means that the energy required in the next stretch may be any value, and each energy value has its own probability of emergence.

It turns out that the probability of these describing DNA away from balanced state is directly related to the nature of the DNA chain balance state. The relationship between the two can be represented by an equation.

This is the core of the rise and fall relationship: the non -balanced state of the system and the balance of the balanced state are connected by a formula. The author's colleague Chris Jarzynski, colleague at the University of Maryland, discovered the relationship in 1997. (Although we call this formula as Yazinuski, he still calls him humblely as a non -balanced state of rising and sunset.) The above DNA experiment provides the most famous verification for this principle, but but The range of this equation is far more than that, including electronics, bacteria, and brass oscillating similar to rubber -like rubber -like rubber.

The rise and fall relationship is of basic and practical significance. First of all, from these equivalent, we can derive the expression of the second law of thermodynamics. Therefore, the rise and fall relationship not only expanded the understanding of the non -balance state as we saw on the DNA chain, but also summarized our understanding of balance.

The true power of the rise and falling relationship is based on the facts of such an iron: Although the nature of the balanced state is easier to describe theoretically, the experiment is more difficult to measure than the non -balanced state. For example, in order to measure the skills made from the DNA chain from the balance state to the non -balance state, we only need to quickly pull the DNA chain in a short time; The balance and measurement of pulling work, then we have to pull it slowly to keep the DNA chain still static at all times, which will consume almost infinitely long time.

Chemists, biologists, and pharmacologists are concerned about the pharmaceutical properties of protein and other molecules, and the application of rising relationships give them experimental basis. They can conduct many simple and non -balanced experiments that are similar to pulling DNA chains and measure the skills done in each experiment. Based on these data, scientists can speculate that the probability of different energy values ​​required in the next non -balanced state experiment. Next, they can substituted these probabilities into the equivalent side of the equivalent of the ups and downs, and calculated the results of the balanced state. Although this method still requires a large number of experiments to obtain enough data, scientists can use mathematical methods to alleviate this difficulty.

In this way, the rise and fall relationship has completely changed thermodynamics. It allows experiments to perform and give fine predictions to the nature of away from balanced state. But its use is more than that.

At the beginning of the 21st century, quantum thermologists were interested in how the classic concepts such as merit, heat, and efficiency in thermodynamics in quantum mechanics were very interested, although quantumization introduced new problems into thermodynamics. Because of the uncertainty of quantum, people do not know how to define and measure "quantum exercises". If you want to measure the energy of a quantum system, measurement itself will change the energy of this system.

As a result, different researchers proposed different definitions of quantum skills, as if various species definitions in the zoo. "Humming Bird Definition" allows us to slowly measure the quantum system and affect energy as small as possible -just like a hummingbird's influence on you in your ears. "Corporal definition" is relatively moderate, focusing on the average energy exchange. Other definitions are also mentioned more or less in quantum thermodynamics literature.

As you may expect, different definitions can derive different quantum rising relationships. The same is true for similar definitions that adapt to different physical environments. Some rise and falling relationships are easily measured in experiments; others are opposite and easy to derive mathematics. Some are suitable for describing high -energy particles, such as particles that collide on high -energy collisions; some chaos that are suitable for describing black holes; and others can describe the expansion of the universe. Experimental physicists have verified some of them with restraint ions, quantum traps and other systems.

Will there be a form of rising and falling relationships to defeat other forms, do you get the widest recognition like a monarch who defeats his opponent to get the throne? I don't think so. In my eyes, which definition and equation depends more on the system of research itself and how to disturb and measure the system.

Physicists have always pursued universality, such as the long -term seeking to unify all basic interactions theory (Theory of Everything), and the diversity of quantum rising and falling relationships are in sharp contrast to this unity. Perhaps some theories can unify various forms of quantum rising relationships in the future, revealing that they are different forms of expression of the same essence; or maybe, quantum thermodynamics is richer and more unified than other physical fields. Author: nicole yunmer hopern

Bleak

Translation: Tibetan idiot

Review: zhenni

Original link:

Beyond the Second Law of thermodynamics | Quanta Magazine

FU

blessing

li

profit

shi

Time

jian

between

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