In the dormitory, Xu Chuan rubbed his eyes and put down the "Linear Algebra" in his hand.

Although he found some ideas when he was studying Weyl_Berry conjecture before, he got stuck in the process of checking the proof, how to expand the domain and how to convert the function into subgroups and establish connections with the intermediate domain and the collection.

He is seriously lacking in this part of the mathematical knowledge, and he knows some about functions, but he is not familiar with the expansion of domains.

But if you want to read books, you have to start with algebra and number theory.

Because the domain is related to algebraic number theory, and the expansion of the domain evolved from the domain theory of abstract algebra.

To put it simply, everyone knows that 'addition, subtraction, multiplication, and division' are the four most basic operations, but these are all for a single number.

For example, 4396-3619=777.

And on this basis, if there is a group of numbers, what should be done if they can add, subtract, multiply, and divide? Count them one by one? That's too much trouble.

Therefore, mathematicians have defined a 'field', which is a group of numbers that can be arbitrarily added, subtracted, multiplied, and divided, and a domain is an algebraic structure on which there is "addition", "subtraction", "multiplication", and "division".

So if you want to understand the 'field' thing thoroughly, you have to start learning algebra.

As for algebra, Xu Chuan must have been in contact with it, but in order to have a more comprehensive understanding of mathematics, he read all the basic textbooks and algebra textbooks borrowed from the library from beginning to end.

In the past two days, he has been nested in the dormitory, and he basically doesn't go out except for three meals a day, which can be regarded as reading one-fifth of the university's textbooks about line generation? Probably not, after all, algebra is quite a huge field, and there are many textbooks.

However, this has already accumulated some questions and doubts, these things are recorded in a notebook, Xu Chuan is going to go to Professor Zhou Hai this afternoon, or ask him to recommend a personal exchange to solve them, and then continue.

......

With his notebook, Xu Chuan came to Zhou Hai's office.

For him, solving a math problem or learning something new brings him the same joy as a game fan who learns the handsome touch of the blind man's handsome roundhouse kick and R five at a time in the ranking when playing CF with a headshot or lol, and an orphan Suo next to him to take advantage of the situation to destroy the other party.

When he stood in front of the office door and knocked on the door twice, Xu Chuan suddenly remembered what he had forgotten in the past two days.

Professor Zhou Hai's student, the hot water bottle of the girl who gave him medicine, seems to be still in his dormitory, and the money to buy cold medicine has not been given to anyone.

"Khan, why did I forget about this?"

Xu Chuan patted his head in annoyance, he said that he would return other people's things the next day, but it turned out that it had been three days, and this spread out, so people must not misunderstand that he was occupying other people's girls' things?

"Please come in."

In the office, a voice woke up the distracted Xu Chuan, who pushed open the door and walked in.

"Huh? Xu Chuan is here, the cold should be completely cured, right? ”

In the office, Professor Zhou Hai glanced at the figure who walked in, and when he saw the person coming, his face was immediately full of smiles.

"It's all right, thank you for your concern."

Xu Chuan gently closed the door and kept the heating in the office, where there were not only Professor Zhou Hai, but also Cai Peng, who was accidentally annihilated in his graduate thesis.

"The big guy is here, what is the big guy going to study next? First of all, let me be a little mentally prepared, at least the graduation thesis must avoid your research direction. ”

Cai Peng got up, poured a glass of water for Xu Chuan, and asked with a smile.

"Weyl_Berry guess, I'd like to try and see if I can expand something new."

Xu Chuan smiled embarrassedly, although it was not his fault, he was still a little embarrassed when facing the wrongdoer.

"Whew, that's good, come on, I'm optimistic about you!"

Cai Peng breathed a long sigh of relief, fortunately he changed his graduation thesis in time, and did not continue to Weyl_Berry conjecture, otherwise he might not have graduated from his doctorate, and his research goal would be gone.

Xu Chuan turned his head to look at Professor Zhou Hai and said, "Teacher, I have encountered some problems watching "Linear Algebra" and "Linear Algebra to the Right" in the past two days, can you help me take a look?" ”

"Huh? Aren't you studying Weyl_Berry conjecture? Why did you suddenly switch to the line generation? Zhou Hai asked curiously.

"I want to take advantage of the time I have recently to read more books to enrich my brain." Xu Chuan said shyly, and did not tell the real reason.

Zhou Hai was stunned, and then said: "It's good, young people should read more books, what about the problem?" Let me see. ”

As he spoke, he also glanced at Cai Peng next to him, it would be nice if this lazy goods were so worry-free, no, one-fifth of the effort would not be so hard that the graduation thesis was written for three months without writing a word.

Feeling the teacher's gaze, the graduate student stood aside and trembled, only feeling that it was not suitable to go out today.

Xu Chuan took out the notebook from his schoolbag and handed it over, Zhou Hai took it and flipped through it, and said, "It's okay, these questions are quite difficult, but I can teach you a little, you move a chair over, and I'll tell you about it." ”

Before Xu Chuan could leave, Cai Peng moved the chair under his feet and looked at him expectantly:

"Big guy, please take a seat."

"Big guy, can I sit in on it?"

Xu Chuan couldn't cry or laugh a little, but he sat down after a while, and on the other side, Cai Peng leaned aside to listen, and the three of them formed a small class.

......

"This problem is related to linear functionals, I haven't started this course in my freshman year, but I should have learned it, it has to use the Fourier transform to deal with it, look at the convolution theorem in the Fourier change, start from it, then turn to the function, and then converge on this line of formulas, and converge the exponential of L² to the f-norm......"

“.......”

"This last problem is quite difficult, mixing the knowledge of number theory domain value calculations and Hilbert spaces, and it needs to be used to use domain expansion to turn it to the commutative ring aspect......"

......

In the small office, Xu Chuan eagerly absorbed new mathematical knowledge from Zhou Hai, asking some questions from time to time and using a pen to perform some formulas on manuscript paper.

Whenever this time, Zhou Hai would stop explaining, and Xu Chuan, who was quietly waiting, finished the calculation, and after the calculation, he would add some knowledge points to these calculations and answers.

This is a scene that will not appear in a university classroom, in a university classroom, the teacher explains the knowledge points, and it is generally faster to turn the book than to turn the face, and basically will not stop and wait for you to digest, absorb and understand.

So in the process of learning, it is really important to have a good teacher who can take you forward and expand the boundaries of your knowledge.

......