Time flies.

On April 20, Academician Lu returned to Jinda from Shanghai for a meeting, and after the meeting, Lu Zhou went to the office.

As soon as Lu Zhou entered the door, the old man looked over and asked with a smile.

"How's the preparation going?"

Lu Zhou: "It's almost there...... I hope that the professor will show mercy. ”

Academician Lu: "Almost?" Okay, I'll just test you two questions. ”

As he spoke, he pulled open the drawer, pulled out an A4 piece of paper, and placed it on the table.

"The pen is here, take it and write it?"

Lu Zhou took the pen and paper, looked at the topic on it, and his brows twitched fiercely.

The two questions that are said are clearly written on the paper.

And if you say that you can take the test casually, it doesn't look like it's easy in any question......

Academician Lu smiled and asked, "What, I don't understand?" ”

"How come," Lu Zhou smiled, looking at the topic, a thoughtful expression appeared on his face, "It just looks like it's not easy." ”

Academician Lu smiled and didn't speak, cocked Erlang's legs, and waited for him to start writing.

Not so easy?

If it's easy, what's the point of getting a test?

How can he also be said to be an academician, can the graduate students led by academicians be the same as the graduate students led by ordinary professors?

These questions were not originally for graduate students, but when he recruited doctoral students, he used them to test the professional knowledge level of those interviewers.

If you can make two of the three questions, then you are qualified, and if you can make three of the three questions, it can be said to be excellent.

The four doctoral students he brought with him were all at the level of being able to make three questions. Although the topics examined are different, the level is similar.

Just when Academician Lu was waiting for Lu Zhou to start writing, Lu Zhou had already quickly gone through all three questions, and then looked at the first question, which was also the easiest question for him.

The first question examines group theory.

However, it is not the mathematical group theory that is examined, but the application of group theory in quantum mechanics.

Since the branch of mathematics "group theory" was independently created by mathematicians long before the advent of "quantum mechanics", unlike "calculus", which was founded by physicists and mathematicians. Therefore, group theory is a "foreign product" for physicists, which is difficult to learn and difficult to use.

However, for Lu Zhou, who was "born in mathematics" and then entered "mathematical physics", it is not so difficult to deal with it.

[Group Theory Explanation of Accidental Degeneracy of Hydrogen Atomic Energy Levels]

The topic is very short, but the amount of information is not small.

The phenomenon that the degree of degeneracy of hydrogen atoms is higher than that of ordinary atoms is called "accidental degeneration". However, traditional quantum mechanics could not explain the phenomenon of accidental degeneracy, and it was not until the introduction of group theory that this phenomenon was theoretically explained.

Closing his eyes, Lu Zhou recalled in his mind the knowledge of quantum mechanics he had learned before, and recalled everything about the hydrogen atom.

Then, the model is built mathematically......

Opening his eyes, Lu Zhou took a deep breath, finally picked up the pen, and wrote on the paper.

[Make the Hamiltonian operator of hydrogen atom H=P²/2μ-Ze²/r......]

[In the case of Coulomb potential, there is a Runge-Leng vector in the system, which is denoted as M'=......]

【The eigenvalue of the Casimir operator of the group C=......】

【……】

Seeing the speed at which Lu Zhou was doing the question, Academician Lu's eyebrows raised slightly.

He originally thought that Lu Zhou would have to spend at least twenty minutes thinking about this question, but he didn't expect him to start writing.

Moreover, the line of thought is exactly right.

Originally, he planned to mention it when Lu Zhou couldn't think of it, but now it seems that he doesn't need it.

[For energy levels E(n+1) and quantum numbers (n, 1), the degree of degeneracy is Σ2(l+1)=n²......]

Seeing the answer, Academician Lu nodded silently in his heart.

Question 1, correct!

Without paying attention to the expression on Academician Lu's face, Lu Zhou continued to cast a focused gaze on the next question.

The second question is about some questions about Dirac hole theory in quantum field theory, which examines the understanding of Dirac equations and some theoretical knowledge about field theory.

This kind of pure theoretical knowledge is not difficult for Lu Zhou, and in the state of concentration guided by drugs, what he sees is basically not forgotten.

For him, this is a scoring question compared to the first question that requires a little bit of thought.

Without stopping, Lu Zhou quickly started writing and answered various theoretical questions raised in the title in explanatory language.

Seeing that Lu Zhou made this question, a smile of relief appeared on Academician Lu's face.

Yes, he really didn't look away.

This kid is a good seedling for the study of theoretical physics, and with the talent he is showing now, he is even more likely to inherit his mantle than the four doctoral students he has brought with him.

If it weren't for the fact that the school had already formulated a talent training plan for him to a higher platform, he would have even thought about simply letting him do it directly with him.

Of course, he also thinks about it this way, and he also supports going to a higher platform to absorb scientific research nutrients.

After solving the second question, Lu Zhou continued to look at the third question.

However, when he saw the third question, he was stunned.

The third question is about "string theory".

The so-called string theory mainly tries to solve the contradiction between the two main physical theories that are incompatible on the surface, that is, quantum mechanics and general relativity, and wants to create a "theory of everything" that describes the entire universe, that is, the legendary "grand unification theory".

Speaking of which, the discovery of this theory has a lot to do with mathematics.

Venecino, who worked at CERN, was looking for a mathematical formula to describe the strong forces in the nucleus, but he found Euler's formula in an old mathematics book that was 200 years old, and was surprised to find that this formula could successfully describe the strong forces he was trying to solve.

It sounds a lot like a plot in martial arts, but it's such a coincidence.

It was by this coincidence that the prototype of string theory was born.

Including the later Bose string theory, superstring theory, and the famous Edward Witten's M theory of "unifying the rivers and lakes", all of which were developed on this basis.

Establishing a "grand unified formula" describing everything in the universe is almost the ultimate goal of theoretical physics.

However, what is more embarrassing is that the development of string theory in China is in a very embarrassing situation.

Condensed matter physics itself stands on the opposite side of theoretical physics, and the theoretical physics community seems reluctant to accept this "mathematical freak".

Even Mr. Yang, one of the most influential physicists in the world today, one of the most influential physicists in the world, even expressed his disapproval of string theory. On the contrary, the domestic mathematical community has an accepting and open attitude towards string theory. For example, Mr. Qiu has crossed over to "like" string theory.

However, what makes Lu Zhou a little puzzled is that this third question does not test the knowledge of string theory, but asks his own views on string theory.

Opinion?

What do you think about the theory? Or is it a perception of the development of theories?

Is this a subjective question?

The tip of the pen stopped on the paper for a long time, and Lu Zhou, who had passed all the way to the last level, was a little confused for a while.