Chapter 270 Qiu Chengtong's Praise

In the area of ​​natural basic sciences, we have to admit that there is indeed a big gap between China and those Western countries.

If he were in Princeton, Xu Chuan would easily find people to exchange mathematics with him. Deligne, Feferman, Sarnak, Witten, Nash, and Xu Jun'er are all Fields Medal winners, and Princeton can find a handful of them.

In China, there are only two people who have won the Fields Medal.

One is him, and the other is Qiu Chengtong, who served as the dean of the Yanqi Lake Applied Mathematics Institute of Shuimu University after returning to China last year.

If we talk about top Chinese mathematicians, China is actually not short of them. For example, the golden generation of Peking University in the 1980s, Zhang Wei, Xu Chenyang, Yun Zhiwei and others can all be called mathematicians.

And Zhang Wei, Zhang Yitang and others are even more popular candidates for the Fields Medal. Even in the international arena, they are among the top mathematicians.

But unfortunately, these people basically do not work in China now.

This also led to Xu Chuan's inability to find a suitable person to exchange mathematical problems with in China.

Taking the high-speed rail, Xu Chuan came to Beijing again.

In Shuimu University, energetic students walked back and forth on campus.

Because he had visited once before, he found Qiu Chengtong's office smoothly this time.

Qiu Chengtong is also well-known in China, but his reputation is mixed, with praise and disdain.

On the one hand, it is because he is a Fields Medal winner and one of the world's top mathematicians.

On the other hand, it is because of the sharp conflict between him and the School of Mathematics of Peking University, as well as his nationality.

He and his student Tian Gang had a sensational academic plagiarism. Not to mention the academic world, even ordinary people who would go online knew about it at the time.

However, as one of the two top universities in China at the time, Peking University had a considerable influence in the academic world. In addition, Tian Gang had become a leader in the Department of Mathematics of Peking University at that time and was strongly supported by Peking University.

In addition, Qiu's nationality is American, which is quite criticized in China, so the matter was left unresolved.

But in the international mathematics community, Qiu's reputation is still quite large.

In the field of mathematics, in addition to the Abel Prize, he has won other top awards, such as the Fields Medal, the Wolf Prize in Mathematics, and the Crafford Prize in Mathematics.

He is also praised by Harvard University as the "ace professor" and the emperor of mathematics, who is equivalent to a mathematics department;

He is also praised by the international mathematics master Donaldson as "the most influential mathematician in the past quarter century", which shows that his mathematical ability is top-notch.

He knocked on the door and there was movement inside.

The person who opened the door was a student-like person. He didn't seem to recognize Xu Chuan, and he asked curiously: "Who are you looking for?"

Xu Chuan: "Excuse me, is Professor Qiu Chengtong here?"

"What do you want to do with Professor Qiu?" Looking at the visitor in front of him who seemed younger than himself, the middle school student in the office frowned and asked.

Since his teacher returned to China and settled in the Institute of Applied Mathematics of Shuimu University, students have come to ask questions almost every day.

It's not that students asking questions to teachers is bad, but the questions raised by those students are too low-level for his teacher.

These are ordinary problems that can be solved by any math professor, but they have to come here.

Maybe they want to win the favor of the teacher by asking questions, so as to be noticed, but this will only waste a lot of the professor's time and delay his research.

The visitor in front of him, who looks younger than himself, may also have this idea.

Xu Chuan didn't think so much. He didn't see the young man in front of him last time, but he could study in Qiu Chengtong's office. He guessed that he might be a new student of Qiu.

He smiled and said, "I want to talk to Professor Qiu about the NS equation."

Hearing this, the student sneered in his heart.

This is another person who pretends to win the favor of the teacher with high-level problems, but he doesn't know that the teacher hates this kind of pretending to know the most in his life.

Studying NS equations, do you think you are the God of Chuan?

He snorted in his heart, and just as he was thinking, the student looked at Xu Chuan and suddenly froze.

Looking at him, he suddenly shuddered. Why does he feel that this person looks so familiar? Like the God of Chuan?

Suddenly, he shuddered again, and the idol figure in his memory gradually overlapped with the person in front of him.

Oh my god, this person in front of him is not really Chuan Shen, right?

He swallowed nervously and asked tremblingly: "Are you Xu Chuan, Chuan Shen?"

Xu Chuan raised his eyebrows and smiled: "It's me."

"Chuan Shen! Is it really you?!!"

Hearing this, Xu Chuan's mouth twitched. How did he become an old man? This generation has increased too fast.

"Come in quickly, Chuan Shen, the teacher just went out for something, and he should be back soon. You sit down first."

The student blocking the door quickly made way, and excitedly and tremblingly invited Xu Chuan to enter the office.

Hearing this title, Xu Chuan shook his head and said: "Just call me Professor Xu, forget about Chuan Shen and old man, these titles are not appropriate."

"Professor Xu Chuan, what would you like to drink? There are coffee, tea, juice and Red Bull here." The young student asked nervously.

Xu Chuan smiled and said, "Just a glass of water will do. No need to bother."

As he said that, he found a chair and sat down. His eyes fell on the manuscript paper on the desk. There were several questions on it, which belonged to the field of partial differential equations. The research was not conventional mathematics, but computational applied mathematics, and intelligent neuroscience. There was something about networking, which piqued his interest.

It has to be said that Qiu Chengtong's knowledge in the field of partial differential equations is at its peak, and you can get a glimpse of it from the test questions given to a graduate student.

He moved the partial differential method into differential geometry with great proficiency, and compiled these extremely spiritual problems.

Partial differential equations are a very magical and widely used field of mathematics. It is very good at describing changes in time and space. It is very useful in describing various phenomena. It can be used to describe everything from planetary motion, weather changes, to changes in the structure of time and space. .

But it is notoriously difficult to solve.

For example, if you try to simulate air turbulence, the Navier-Stokes equation is the pinnacle of this field.

By solving this partial differential equation, you can know the motion of the fluid at any point in time and model how it will continue to move or how it was moving before.

But these calculations are very complex and computationally intensive, so supercomputers are often relied upon to perform the math.

And this is where the fields of artificial intelligence and intelligent neural networks can come into play, by using deep learning to speed up solutions, which will be of great benefit to scientific exploration and engineering applications.

Several questions on the manuscript paper on the desk are all related to this aspect. It seems that they are homework left by Qiu Chengtong to his students. Some of them have answers already written on them. Xu Chuan is looking at the part with the answers.

"This idea is somewhat interesting. By approximating the Fourier function in Fourier space, a series of operations are completed. However, this answer is not perfect. Without transformation, the entanglement cannot be reduced, and the answer cannot be accurately obtained."

On the manuscript paper, the answer to a question aroused Xu Chuan's interest.

For him, it can be said that the answers and methods can be seen at a glance, as well as the flaws and problems in the answers.

But the above idea did surprise him. This was a solution he had never thought of.

This is normal.

Everyone has their own unique thoughts and ideas. Even if Gauss and Newton are reborn, they dare not say that they understand all mathematics and can find all solutions to a mathematical problem.

Xu Chuan never thought that he could surpass everyone by winning the Fields Medal. In the field of mathematics, no one has such qualifications.

In the office, as soon as the young student came over with a glass of water, he heard Xu Chuan's soliloquy and was shocked in his heart.

Is this what a Fields Medalist is capable of? The flaw in his answer was immediately apparent.

After thinking about it, he finally couldn't hold it back and asked: "So, Sichuan God, is there a way to change this entangled nature?"

He has been stuck on this problem for a long time and has never thought of a good solution. Now a top expert in mathematics is right in front of him and he is interested in the problem. How can he resist asking.

Hearing the inquiry, Xu Chuan came to his senses, took the water glass and said with a smile: "What's your name?"

"Wei Yong, Sichuan God can call me Xiao Wei or Xiao Yong." The young student quickly replied.

Xu Chuan smiled and said: "Your idea is quite interesting, but subsequent expansion is not something you can solve at this stage."

"If I guess correctly, you should be Professor Qiu's new graduate student, right?"

Wei Yong nodded and said, "Well, I only studied with Professor Qiu in the second half of last year."

Xu Chuan continued: "Let me ask first, how did you come up with the idea of ​​using Fourier space to approximate the Fourier function to complete a series of operations in intelligent neural network data calculation?"

"According to common sense, solving such problems is often promoted through functions between input and output defined in an approximate Euclidean space, right?"

Wei Yong scratched his head, smiled sheepishly, and said: "I minored in computer science in college. I often use Fourier transform for simulation in signal processing, so I want to try the approximation in Fourier space. function can get the answer to this question."

As he spoke, he spread his hands: "The result is obviously easy to see, but I'm stuck and can't find a way to calculate the exact value."

After a pause, Wei Yong continued: "But I always felt that this road should be possible, so I never gave up."

Xu Chuan smiled and picked up the test paper on the table, pointed to the answers on it and said, "Your feeling is right. This path can indeed be taken, but your knowledge reserve is not enough, and you took the wrong step in the second step. "

Just as he was talking, the office door was pushed open, and an old man wearing glasses walked in. Seeing the figure in the office, the old man was stunned for a moment, and then walked over with a smile on his face.

"A rare visitor, why do you think Professor Xu is free to come and sit with me today?" Qiu Chengtong smiled and greeted him warmly.

Xu Chuan stopped talking, stood up and said with a smile: "I encountered a problem in mathematics and wanted to come to you for advice."

A trace of surprise flashed in Qiu Chengtong's eyes, and he smiled and said: "I would like to hear what the problem is that can make you feel difficult."

Xu Chuan said: "It has something to do with the NS equation."

Qiu Chengtong was slightly stunned. Although he knew that the question that could stump the person in front of him would definitely not be simple, he did not expect that it would be directly on the level of the seven millennium problems.

Smiling, he took off his coat, hung it on a hanger nearby, and continued: "This is a big problem. It probably won't be solved for a while. Sit down first. We have plenty of time to chat."

Xu Chuan smiled and said: "I have been studying the NS equation with Fefferman for a while, and I want to continue studying it."

"But I encountered some problems when studying the field of partial differential equations, and in this field, Mr. Qiu, you are the real expert, so I thought I would come over and ask for your advice."

There is nothing wrong with what he said. In the field of partial differential equations, Qiu Chengtong is indeed the top expert, and can even be said to be NO1 in this field.

He not only greatly expanded the role of partial differential equations in differential geometry, but also created the extremely important branch of mathematics "geometric analysis".

Not to mention others, five mathematicians who came out of the field of geometric analysis have won the Fields Medal, which shows the importance.

Qiu Chengtong smiled and shook his head and said: "It's okay to give advice from an expert in front of you. You are the first person in history to win the Nobel Prize and the Fields Medal."

"Xiaowei, go make a pot of tea."

While directing the students to make tea, Qiu Chengtong's eyes also fell on the test paper in Xu Chuan's hand. He smiled and said: "This is just an assignment left for the students. Professor Xu must not just solve it easily."

Xu Chuan said with a smile: "This student is quite interesting. He already has some ideas of his own on partial differential equations, which is quite good."

"oh?"

Hearing Xu Chuan's praise, Qiu Chengtong let out a surprised sound, reached out and took the manuscript paper and read it.

After a while, he smiled and shook his head and said: "This idea is indeed interesting, but there is a problem with this answer and it doesn't work."

Xu Chuan nodded and said: "Yes, he made a key mistake. He forced the conjugate to make the function space a Hilbert space. This will make it impossible to expand in the second step."

Qiu Chengtong thought for a while and asked: "If this problem is to be solved through this approach, what do you think?"

Xu Chuan pondered for a while and then said: "To transform the approximated Fourier function, we need to parameterize the integral kernel in the Fourier space, and then use the function to approximate it by orthogonal decomposition of the complex exponential signal, and then convert it into Describe the wave function of momentum p."

Qiu Chengtong thought for a moment, and then praised: "This is indeed the most suitable way."

"What I just thought about is to use Fourier series to make orthogonal function intersections and Lagrangian interpolation polynomials to make basis functions, and then use the non-singular values ​​of the coefficient matrix to solve it."

"But this method is much more complicated than your method and requires a lot more calculations."

"I didn't expect you to have such a deep understanding in the field of partial differential equations. It's really surprising."

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