Chapter 7

Ji Zhixing had already finished reading two volumes of "Mathematical Methods in Physics" during the summer vacation. Although there were many difficult points he didn't understand when he was reading them, as his learning ability improved, he was able to understand some of these points on his own when he recalled them.

Therefore, Ji Zhixing was one of only two students in the classroom who could understand the problem that Professor Yan had written down.

Over the past month, Ji Zhixing has become quite accustomed to tackling tricky problems under the system's task assignments, and he can't help but enter a state of thinking as soon as he sees this problem.

As usual, he copied the question onto a piece of scrap paper and then began to examine it.

Φ(x) is a scalar field, λμv(x) is a symmetric auxiliary second-order tensor...

The Fourier transform form is also given...

So……

Gradually, he entered a very mysterious state of thought, as if the whole world consisted only of him and this problem.

So when Fan Yongjie looked at Ji Zhixing smugly, Ji Zhixing was immersed in his own world and had no time to admire his academic prowess.

Fan Yongjie was displeased. Ha! He's putting on an act as if he could actually do it.

Yan Anjin, who has been teaching on the front lines for over twenty years, noticed something amiss when Fan Yongjie was only halfway through writing on the blackboard. He had no interest in commenting on this reasoning process of simply copying the answer.

He briefly explained the underlying logic of the problem, and was about to open his textbook when he noticed out of the corner of his eye that a student in the first row seemed to have grasped the concept, so he went over to take a look.

Xu Dongyang and Lin Lang, who were sitting next to Ji Zhixing, saw Professor Yan walking over and quickly nudged Ji Zhixing under the table. However, Ji Zhixing was completely absorbed in the deduction process and had almost transcended the three realms and five elements, so he was unmoved.

Yan Anjin waved her hand, indicating that he didn't need to be disturbed, and leaned over to look at the draft paper on the table.

On the draft paper, under the title copied down, were the words: covariant derivative and contravariant derivative.

Hmm? This idea is interesting.

Ji Zhixing was completely unaware that there was another person in front of him. He had just sorted out his thoughts, scribbled down two lines of equations on the paper for substitution, and then used two different variables to substitute into the first term of the action of S.

Hmm... Ji Zhixing continued to think. Since he wanted to get the expression in the momentum representation, he had to find a way to remove d2x. He wrote down an equation.

In order for the action of this part to be non-zero, k + k1 must be 0, so we get the final result of the first part.

We will now substitute the derivative to calculate the second part of the action.

But how do I remove the d2x from this part? Ji Zhixing started pulling out his hair.

Because Professor Yan was watching so intently, no one in the class dared to make a sound. But people's gossipy nature is hard to suppress, and everyone started exchanging messages by writing, typing, and even telepathically.

"What happened?"

"Could it be that Ji Zhixing also made it?"

"That can't be right. Didn't Professor Gang say that this was a question that would only appear on the final exam?"

"Didn't Ji Zhixing start reading books during the summer vacation? Maybe he really did make it."

"Oh, that's interesting. It seems like the outcome of the final exams is still uncertain."

"Fan Yongjie is definitely better. He solved this problem in just over ten minutes. How long did it take Ji Zhixing? It's almost the end of get out of class by now!"

"No, no, look at the professor's attitude and micro-expressions; there's a lot to it."

Everyone silently chatted while watching Ji Zhixing pull out his hair.

As the seventh innocent hair drifted through Ji Zhixing's fingers, Yan Anjin couldn't help but suggest using Fourier transform, when she saw Ji Zhixing suddenly sit up abruptly from his deathbed and begin writing furiously:

The inverse transform of λμv can be obtained from its Fourier transform, therefore...

The final expression for the second part is...

In summary, the action S in the momentum representation is S = ...

"It's done!" Ji Zhixing suppressed his excitement and was about to check for any flaws when a hand snatched away his draft paper.

He looked up and saw Professor Yan looking at him kindly: "Your idea is very interesting. How did you come up with it?"

Ji Zhixing quickly stood up and explained his thought process.

Yan Anjin nodded: "Okay, very good."

If Professor Yan's previous students were to see this scene, they would probably be utterly astonished.

Professor Yan rarely praises anyone, and those who receive a single compliment from him are few and far between. The most recent one was a senior from two years ago, who is now pursuing her PhD at Harvard. Going back further, one would have to go back ten years, which shows how difficult it is to catch Professor Yan's eye.

Yan Anjin looked at the draft paper in her hand again and couldn't help but exclaim, "Wonderful!"

This question was the final exam question for the second-year math physics methods course last year, and 99% of the students failed it.

The original answer was incredibly long; for example, Fan Yongjie's solution filled two blackboards. However, Ji Zhixing's solution took a different approach, using covariant derivatives, contravariant derivatives, and Fourier transforms to simplify the process to just 12 lines. His thinking was undeniably ingenious.

Yan Anjin walked up to the podium, placed the draft paper on the display stand, and projected it onto the electronic whiteboard.

Those who had only seen Ji Zhixing pulling his hair earlier quickly opened their eyes wide to take a closer look. Hmm, well written! Although they still couldn't understand the content, they could read between the lines.

After Fan Yongjie finished writing, Professor Yan remained expressionless, which they initially assumed was due to his usual seriousness. Now, however, they noticed that the deep nasolabial folds on Professor Yan's face were subtly lifted at the corners of his mouth, making the difference obvious.

Yan Anjin pointed out Ji Zhixing's reasoning process and analyzed the logic in detail. She then repeatedly emphasized the importance of creative thinking and independent thinking, and praised Ji Zhixing once again.

Fan Yongjie gritted his teeth silently, deeply resenting Professor Yan for disrespecting him. His own father was Professor Yan's colleague! Humph! So lacking in social skills, no wonder he hasn't been elected an academician for decades.

Someone quickly took a picture of the podium and uploaded it to the betting thread on the school forum. Soon, students who were slacking off or had no classes started to chime in.

Who is this?

"King Yama, can't you tell? You've been given Meng Po's soup by him!"

"No way, who's so bored as to Photoshop a smiley face onto the King of Hell? It gave me quite a fright."

"It's not photoshopped, he's really laughing, it's live!"

"This thread has gone off-topic, hasn't it? Go start a new thread, and I guarantee a whole bunch of wronged souls, the underworld's minions, will come in to vent their grievances. Don't try to ride this wave of popularity."

"There's no misdirection here. The two derivation processes on the blackboard and screen belong to the two parties involved in this post. Can you guess who Professor Yan is smiling for?"

"Since you've said that, there's no need to guess. It must be Ji Zhixing, whom everyone doesn't think highly of."

"If the document on the screen was written by Ji Zhixing, then he is indeed quite capable."

A chorus of agreement erupted from below. Not all of them actually understood it, but they could count. Ji Zhixing wrote 12 lines, while Fan Yongjie wrote 20 or 30. The simplest solutions are often the best; Ji Zhixing's was definitely superior. Combined with that knowing smile, Ji Zhixing's solution was arguably exceptionally good.

Gradually, the 1:9 betting ratio in the posts began to change.

The bell rang in the classroom, and Professor Yan left with the draft paper.

The students didn't leave, because they knew the next class would be in the same classroom. They subtly glanced back and forth between Ji Zhixing and Fan Yongjie, hoping for some further interaction between them. Those still waiting for what happened on the forum were even more unscrupulous, practically wishing they would fight on the spot.

At this moment, Lin Lang walked up to the podium and said loudly, "Everyone, please be quiet. The sports meet is next month. Anyone who wants to register, please come and register with me!"

Lin Lang is the class's sports representative. Because of his outgoing personality, he gets along well with everyone. But this time, no one was willing to sign up even after he called out several times from the podium.

In their freshman year, everyone was full of enthusiasm for university life and participated in various activities quite actively. By their sophomore year, everyone had been struggling to climb the ladder of knowledge for a year, and their mentality was generally aged. University life had long lost its novelty, so they simply couldn't muster any interest in these thankless activities.

Ji Zhixing and Xu Dongyang exchanged a glance and then stood up and walked onto the podium.

Ji Zhixing picked up his pen and marked the 3000-meter race. This was the event that no one signed up for last year, and Lin Lang ended up doing it himself. He vomited after finishing the race, and Ji Zhixing had to carry him back to the dormitory. This year, he preferred to have Lin Lang carry him. However, it was only 3000 meters. After jogging slowly for more than a month, Ji Zhixing felt that he might not end up needing someone to carry him.

Lin Lang was so moved that he wanted to hug Ji Zhixing and call him "Dad" on the spot, but Ji Zhixing disdainfully pulled away.

Xu Dongyang had been out of exercise for a long time, so asking him to run was like taking his life, so he opted for a fixed-point shot.

Lin Lang proudly displayed the registration form: "Two people have already registered! Someone has signed up for the 3000-meter race! There aren't many opportunities left, so don't miss out!"

With someone taking the lead in signing up and even securing the most challenging project, things became much easier for Lin Lang. He used a combination of coercion and enticement, relentlessly pursuing the project until he finally sold all of them.

After Lin Lang put away the registration form, Fan Yongjie walked up to him and said, "It's a pity I have to participate in the CUPT competition this semester, otherwise I would have registered."

Lin Lang looked at him, puzzled. "Then why are you talking nonsense?"

Fan Yongjie didn't look at him; he looked at Ji Zhixing instead: "I think the results of the sports meet shouldn't be considered part of our competition, right?" Although a first prize would add points.

"I know that," Ji Zhixing said, looking at him with a puzzled expression.

Fan Yongjie felt a little embarrassed by the two pairs of inexplicable eyes staring at him, but he still returned to his seat as if nothing had happened. Mainly, after the math and physics methods lesson just now, his confidence in his victory suddenly wavered.

Although one question doesn't prove anything, what if...?

Fan Yongjie couldn't let go of that Patek Philippe. If he missed this opportunity, when would he ever be able to get a million-dollar watch for free?

Before he could finish his random thoughts, the phone rang.

The second lesson is a physics experiment; the beginning of the semester often focuses more on theoretical learning.

Fan Yongjie felt relieved when he thought about the course. This semester, in addition to the physics experiments, there was an additional simulated electronics technology experiment, which tested practical skills and couldn't be mastered by simply studying and doing practice problems.

Does Ji Zhixing have the conditions to practice like him? Ha!

Professor Yu Minzhong, who was teaching the physics experiments, waved familiarly to Fan Yongjie as soon as he entered the room.

"Xiao Fan, come over here and help me distribute the materials."

While counting the materials, Fan Yongjie chatted with Professor Yu for a few moments with a smile. When the materials were handed out to the first row, he gave Ji Zhixing a meaningful look.

Ji Zhixing knew what he meant. Ha! Fan Yongjie relied on his father's connections, but he relied on his grandson's connections. Who's afraid of who!

A note from the author:

The problem and solution are from the internet.

Um, since most of the symbols typed in the document are in image format and cannot be copied over, please type the characters if possible, and use ellipses to represent those that cannot. Sorry for the inconvenience.