The Science Fiction World of Xueba

The most important point of m-theory is that on the basis of superstring theory, the study of non-perturbative strings is added.

In addition to one-dimensional strings, non-perturbative string theory also includes high-dimensional objects such as two-dimensional membranes and three-pyramids (collectively referred to as membranes).

Before Pang Xuelin and Witten formally began to study m-theory, the international physics community generally believed that superstring theory and supermembranes with a space dimension greater than one were two different theories, and there was no necessary connection between the two.

However, after Pang Xuelin and Witten conducted research on non-perturbative string theory, they discovered that on the basis of unifying quantum mechanics and general relativity, not only can one-dimensional strings be connected with other superbranes, but also other superbranes can be connected. membranes are unified within the same theoretical framework.

These supermembranes are the unified dynamic objects of the theory, especially when the interaction of strings is large (that is, the strings are in the non-perturbation region), the dynamic effects of these high-dimensional membranes are more important than those of one-dimensional strings.

This also proves to a certain extent why perturbed strings cannot give a complete theoretical framework of low-energy physics, because it ignores the more important dynamical effects of high-dimensional membranes.

Therefore, in the past six months, Pang Xuelin and Witten have been using Ponzi geometry to establish the dual relationship between five different superstring theories.

The so-called dual is essentially a mathematical concept, defined as follows: If two logical expressions are equal, then their dual expressions are also equal.

Here, it refers to the fact that there is some degree of equivalence between two seemingly different physical theories.

Pang Xuelin and Witten found that this kind of duality is mainly divided into two types, one is s-duality, and the other is t-duality.

The s-duality refers to a set of strongly interacting particles in a perturbative string theory, which in some cases can be regarded as a set of weakly interacting particles in a completely different theory.

The t-dual means that the chord propagating in a circle with radius r is equivalent to the chord propagating in a circle with radius 1/r.

They found that type I string theory is equivalent to so(32) hybrid string theory under s-duality.

Type iia string theory is equivalent to type iib string theory under t-duality.

...

Through the various duality and equivalence relations between the five string theories and eleven-dimensional supergravity, the five string theories can be unified.

Each of the five string theories is the result of a different extreme case of m-theory.

This is the m-theory proposed by Witten in the real world, and it triggered the second superstring revolution.

M-theory reveals the nature of interactions as well as spacetime, implying their nonfundamental nature.

In particular, the theory predicts the existence of extra dimensions and supersymmetry, providing for the first time a microscopic explanation for some black hole entropy.

However, in the process of establishing m-theory, Pang Xuelin and Witten also discovered some problems.

The first is the vacuum problem.

There are various vacuum states in the m-theory, given mathematical calculations, they conservatively estimate that there are at least 10^500 such vacuum solutions.

Moreover, the physical constants and cosmological constants of each vacuum solution are different.

The recent cosmological observations show that the universe where the earth is located has a small positive cosmological constant, which governs the current accelerated expansion of the universe and constitutes the main matter (dark matter and dark energy) in the universe.

How to find the vacuum solution of the existing universe from many vacuum solutions, and give a first-principles explanation, is a question that m-theory needs to answer.

Secondly, m-theory also needs to answer the source and nature of dark energy.

According to Pang Xuelin's calculations, at present, the cosmological model of the inflation of the early universe can be given through the m-theory, and even directly calculated that the tensor disturbance in the very early universe is much smaller than the scalar disturbance.

This is consistent with the latest cosmological observations.

But when it comes to dark energy and dark matter, there is no way to give a reasonable explanation for the time being.

Third, they also found in their calculations that m-theory also exists in how to explain the strong coupling behavior in quantum chromodynamics, such as the vacuum properties of quantum chromodynamics, the properties of quark-gluon plasmas under high temperature conditions, etc. A certain difficulty.

Neither Pang Xuelin nor Witten have done much research on the first two questions.

They are very clear that under the existing experimental conditions and astronomical observations, there is no way to make further breakthroughs in these two problems for the time being.

But on the third question, Pang Xuelin and Witten disagreed.

"Pang, our m-theory has perfectly unified the five string theories and eleven-dimensional supergravity. Although we have not yet been able to confirm that our theory is completely correct, these seamless dual relations and the relationship between the theories Other wonderful relationships are enough to prove that we have no problems in the general direction..."

On the small terrace of the villa, Witten was drinking tea while smiling at Pang Xuelin.

The research in the past six months has been smoother than he imagined.

In particular, the various dual relations established by using Ponzi geometry very cleverly connect different perturbative string theories.

Witten is sure that once this result is proposed, it will definitely cause a sensation in the physics community.

If it is not that the existing experimental conditions cannot verify this theory, the significance of this theory in the history of physics is comparable to that of Einstein's theory of relativity and the research by Max Planck, Niels Bohr, Werner Heisenberg, Quantum mechanics developed by Erwin Schrödinger and others.

But just when he thought he could write a paper to show this great achievement to the physics community, Pang Xuelin objected.

"Professor Witten, I don't think we need to be so anxious." Pang Xuelin said, "According to my previous calculations, m-theory can explain the strong coupling behavior in quantum chromodynamics, but there is no way to explain it now. We must still Something was missing."

In fact, this is not only the result of calculations. In the real world, Pang Xuelin also learned quantum chromodynamics during the process of studying materials science and chemistry.

He remembers clearly that in the real world, the strong coupling problem in quantum chromodynamics has been solved and has applications in condensed matter physics, materials science and other fields.

Witten smiled and said: "Pang, the results we have achieved so far are quite perfect. Even if there are still some dual relationships that we have not found, they are enough to support the existing theoretical framework system. We don't need to continue to nitpick."

Pang Xuelin was slightly taken aback, his eyes lit up suddenly, and he said, "Professor Witten, what did you just say?"

Witten said: "There is no need to continue to nitpick."

"No, it's the last sentence."

"The last sentence? Our results are already perfect, even if there are still some dual relationships that we haven't found..."

"Yes, it's a dual relationship!"

Pang Xuelin clapped his hands and said, "Professor Witten, how about this, why don't you write the paper first, and I will continue to research on the current basis, what do you think?"

"Fine!"

Witten hesitated for a moment, then nodded.

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