Chapter 799 The email that affected the entire history of mathematics

In the previous letter sent to Chang Haonan, Li Yabo had already expressed his hope to use structural mechanics as a research field.

However, "structural mechanics" is still a huge field after all, and most people can only choose a more specific direction of specialization from it throughout their lives.

Not to mention a mere graduation project.

Of course, under normal circumstances, undergraduate graduates are just handed over to a certain senior brother or sister to get started while getting familiar with the research group and project, and then it's almost over.

However, as Chang Haonan's first disciple, Li Yabo's treatment is naturally extraordinary——

Chang Haonan is going to take him with him personally.

The kind that starts with formulating a training plan.

But at present, Chang Haonan only has one turbofan 10 project left at hand.

After all, Li Yabo is still an undergraduate.

No matter from the perspective of ability or confidentiality, it is not suitable for him to directly contact a project of this level——

After all, Chang Haonan's direct participation in the August 3rd Project was a special situation and could not be regarded as a regular occurrence.

So, just let the other party choose.

Anyway, with Chang Haonan's current position in the Science and Technology Commission system, as long as the direction is not too outrageous, he can get projects immediately.

And Li Yabo did not disappoint.

Such a specific and targeted answer has obviously been considered long ago.

Composite material thin-walled boxes are also a subject with a very wide range of applications.

And very prophetic.

The "box" here is not limited to horizontal and vertical hexahedrons, but also includes cylinders, ellipsoids or other irregular shapes.

Basically, it is the main research direction in the aerospace field in the next 20 to 30 years.

For example, the body of large passenger aircraft and the casings of rockets and missiles will gradually increase the amount of composite materials used to reduce the structural weight.

For example, when Eurocopter designed the NH90, it had already considered using a large number of composite materials in the fuselage.

It's just that the operating environment of helicopters is indeed quite harsh. Giving up ease of maintenance and damage resistance for the sake of a small amount of weight is like throwing sesame seeds at the expense of watermelon, so Chang Haonan stopped it.

However, at the end of the 90s, the application of composite materials was still a cutting-edge field. It is really surprising that a senior undergraduate student could choose it so accurately.

"Tell me why you want to go in this direction?"

Chang Haonan asked.

"Didn't I work on a small drone structural design project with Mr. Li Guang... At the beginning, because the engine provided by Party A was not powerful enough, Mr. Li considered using carbon fiber instead of metal to make the body of the drone. "

"But in the end, because we had never done any research in this area before, Party A was worried that the design risk would be too great, and of course there were cost issues. In the end, we ended up using magnesium-aluminum alloy."

Chang Haonan was speechless for a moment.

It is indeed risky to consider a 100% composite body.

At present, Huaxia aircraft generally uses less composite materials, and its main applications are secondary skins and other locations that do not bear high loads.

"So...how was the problem of the overweight body solved in the end?"

This question is just out of pure curiosity.

The intersection between Chang Haonan and Professor Li Guang was limited to when they were first reborn. The other party served as a judge in Teacher Liu Hongbo's class and was shocked by his design plan.

So the former doesn't quite know what the drone project is about.

"Not solved."

Li Yabo replied:

"Party A later replaced the piston engine in the original plan with a more powerful lightweight turboprop, so it was overweight. That project did not have high requirements for us. Basically, it only needs to be able to fly..."

"alright."

Chang Haonan never expected that it would end like this:

"Now that you are sure, let's go in this direction."

After speaking, he lowered his head and thought for a moment:

"However, scientific research must be carried out step by step. Research on composite material structures is a brand new topic for our country... and the world, so we cannot start large-scale projects right away..."

"I have some relevant information and literature that I will give you to look at today to familiarize yourself with the basic research methods of material mechanics and structural mechanics. I will officially start after I apply for the project."

"it is good."

After talking about the project, Chang Haonan asked Li Yabo to go to Liu Chenchen to get a stamp to prove that he had indeed entered the research group and completed the topic selection process.

Graduation project is regarded as a "course" that takes up more than ten credits in the training program.

If the topic opening link is missing, although Chang Haonan can handle it, it is still more troublesome.

"call……"

Seeing Li Yabo's back disappearing from the door, Chang Haonan, who almost revealed that he had forgotten about her, finally breathed a sigh of relief, then returned his attention to the computer screen and began to think about how to write a reply to Perelman.

……

A few days later.

Moscow, Steklov Institute of Mathematics.

Grigory Perelman, who had been working for more than ten hours straight and was about to go home for a break, opened his mailbox as usual and prepared to check if there were any new emails that he needed to deal with.

This is his personal habit.

Plan your next day's work before you leave work the day before, rather than waiting until after you arrive at work that day.

Over the past decade or so, this has always been the case.

"Invitation to Princeton's Annual Mathematics Meeting..."

"Millennium Mathematics Prize..."

"The invitation for a review of the Journal of Mathematics... ha... seems to have been affected by the actions of the Annual Journal of Mathematics. They are really stupid. If they continue like this, their influence will never catch up with the Annual Journal of Mathematics..."

"..."

Perelman deftly sent emails he deemed unimportant to the recycling bin.

It even included a notice awarding him the Millennium Mathematics Prize and informing him to receive it.

He has no plans to leave Russia in the near future.

At least I won't leave because of these "trivial" things.

What Perelman loves is the beauty and mystery of mathematics itself. After successfully proving the soul conjecture a few years ago, he discovered that if he won an award for solving a certain mathematical problem, it would dilute his ability to solve a certain mathematical problem. The joy derived from the problem itself.

From that time on, he refused to accept any personal awards, and even gradually tended to publish his results directly to the public rather than in the form of written papers.

"and many more……"

Just when Perelman thought tomorrow would be another boring day, he suddenly caught a glimpse of an email he had been waiting for.

To be precise, it was a reply letter.

"Finally here..."

He clicked quickly.

About a month ago, he was shocked when he saw this paper published in the Annals of Mathematics.

There is actually another person in the world who is solving the application problem of Ricci flow under three-dimensional conditions with a similar idea to him.

Moreover, he was half a step ahead of him.

So, after getting some inspiration from it, Perelman wrote his thoughts in an email and sent it to the author of the paper.

For more than a week, he did not receive a reply.

until today.

[Dear Professor Perelman, thank you for your letter. The content of the email has greatly inspired my research...]

Perelman skimmed over the pleasantries.

Fortunately, Chang Haonan's reply style was similar to his, and the second paragraph went directly to the point:

[I have verified your conclusion and there is no problem, but the derivation process of the theorem seems to be more concise and direct...]

[The function of the non-local collapse theorem is that it can give a local injective radius estimate, and the Ricci flow after surgery can still satisfy this property. In this case, based on Hamilton's injective radius estimation theorem, it can be derived For the marked (Mk, gk(t), pk) that satisfies certain conditions, there must be a convergent subsequence...]

【…】

The expression on Perelman's face changed from relaxed to serious, then to excited...

He quickly pulled out a ballpoint pen and a piece of paper from the desk next to him, lowered his head and began to calculate quickly.

"That's right... This verification process needs to be more straightforward..."

About half an hour later, Perelman looked at the calculation process that only used one positive and negative space, and said to himself excitedly.

Although the content of the theorem proved by Chang Haonan is exactly the same as what he sent before, the process is much simpler.

"In this case, I don't seem to have to worry about those guys not being able to understand my proof process..."

Perelman muttered as he took off his coat and scarf and returned to his desk.

Obviously, the plan to get off work was definitely ruined.

"Perhaps I should go to China myself?"

He looked at the signature of CHANG Haonan at the bottom of the email on the computer screen, and had long since forgotten all about his earlier thought of "not planning to go abroad in the near future."