That, This... Green's Function?

That, This... Green's Function?

The beautiful teacher, Wang Lili, took a moment to collect herself before speaking. "Well... Today, I'll teach you some material on mathematical physics equations. Of course, not the homogeneous equations you've studied in class, but..."

"Today, the main topic is the Green's function method for the two-dimensional Laplace equation..."

The moment she said that, the room filled with groans.

Ye Kaifu finally understood why nobody had taken a seat in the first three rows.

Was this class really that brutal?

The kinds of questions that usually appeared at the end of math exams—Fourier transforms, orthogonal expansions, ordinary differential equations, and so on—were all standard tools here. Of course it was hard.

Without wasting any more time, the teacher began the lesson.

"Everyone, I'm sure you've already studied homogeneous and inhomogeneous partial differential equations. Since time is limited, we won't review them here..."

Ye Kaifu habitually glanced at Zhang Yuan, only to find the genius still lost in his own world, who knew what he was thinking about.

Wait a second.

He looked like he was asleep!

He was asleep. Actually asleep!

Haha!

Ye Kaifu almost burst out laughing. Seeing that he had taken the lead in "effort points" made him feel fantastic. He nearly exploded in his seat.

"Focus, focus. He's sleeping, but I can't slack off!"

"I've got to take this chance to learn more."

"Most textbooks introduce the Green's function method in the context of the three-dimensional Laplace equation. Its core content is the spatial form of Green's identity, along with an analytic representation of three-dimensional harmonic functions. The Green's function method for two-dimensional problems has some similarities to the three-dimensional case...%@@!"

The material was obviously difficult. Even a beautiful face couldn't directly boost the male students' intelligence. The atmosphere in the classroom stayed awkward throughout, as though a pretty girl were talking to herself at the front of the room.

The Green's function method was based on double and triple integrals. Ye Kaifu racked his brains, only to realize he'd forgotten most of the material. Every so often, he had to skip something.

But the more he skipped, the less he understood what the teacher was saying.

He gave up trying to keep up. He didn't dare play on his phone in the front row, so he might as well enjoy the teacher's looks.

"Oh my goodness... Now I finally understand why the boss couldn't be bothered to teach this class and sent me here instead."

"This is torture!"

Seeing the bewildered faces, the students dozing with their heads down, and the few little punks playing on their phones, Wang Lili stood at the blackboard and vented silently.

"This is like teaching a bunch of pigs..."

She seemed to have forgotten that she'd once been just like them. Her own teacher must have thought she was a pig, too.

"Hold it in, hold it in!"

"I can't take it anymore. This is so frustrating!"

Wang Lili didn't have the same broad-mindedness as the old professors, who could lecture on without a care while a whole roomful of students played on their phones or dozed off.

She was frustrated, too. I worked so hard to prepare this lesson, and you're all messing around down there?

Why should I stand up here chanting like a nun? I can't do it...

Well, she could call on a few people to liven things up. Maybe wake up some of the sleepers, too!

That's it!

The young man in the front row looked pretty attentive, and he'd sat in the front from the start. There was a good chance he was a top student.

He should be able to answer. She'd call on him. That way, no one would lose face, and she might wake up the others, too.

"Could you come up and solve this problem, please?" Wang Lili asked with a bright smile.

The atmosphere in the room turned serious in an instant. Being called on really was a classroom nuclear weapon: nearly every sleeping student plummeted from paradise back to reality.

Even the students on their phones tucked them away in their laps...

"What? Me?" Ye Kaifu stood up, his face flushing red.

He'd only been pretending to study attentively, and now he'd been called on to answer a question.

How awful.

Really.

"First, you need to consider..." Wang Lili offered a few hints.

"Well, um... Green's function... the two-dimensional Green's function..." Ye Kaifu said weakly.

Those were the only words he seemed to know.

He kept scratching his head and ears as his brain churned furiously.

Unfortunately, even if his head exploded, he still wouldn't be able to solve the problem.

"Ah, sit down, sit down..." Wang Lili hadn't expected even the good students in the front row to be unable to answer. She could only wave him back to his seat in disappointment.

Maybe she hadn't explained it well enough, or maybe the material was just too difficult...

Still, the atmosphere in the room had improved quite a bit.

After that, everyone else sat up properly. Only a few stubborn ones were still fast asleep—actually asleep.

Especially the student at the far left of the front row. How could he sleep so comfortably? Sleeping in the front row was a terrible look!

"Can anyone solve this problem? Use the method I just described, with harmonic functions..." Wang Lili repeated.

The atmosphere in the room turned awkward again.

"What about you... the student at the far left?"

Ye Kaifu quickly tapped Zhang Yuan, who was fast asleep, making him leap out of his seat with a startled "Ah!"

What was going on?

Zhang Yuan opened his eyes in confusion.

A quiet burst of laughter rippled through the classroom.

"The teacher wants you to solve the problem!" Ye Kaifu nudged him, raising his eyebrows. He was practically bursting with delight.

Zhang Yuan blushed and scratched his head sheepishly.

He'd been pulling all-nighters and was exhausted, so he'd accidentally fallen asleep.

"Can you solve it?"

Although she was a little unhappy, Wang Lili had only meant to get him to sit down. Waking him up was enough.

They were all adults. Everyone was responsible for their own life, and there was no need to criticize or lecture him.

Besides, this class had only been arranged to prepare students for various competitions. There wouldn't be an exam, and it didn't carry much weight...

Zhang Yuan glanced at the PowerPoint. His foggy mind began to clear, and he said quietly, "I think we use Green's function..."

Everyone burst out laughing. They'd spent the whole class talking about Green's functions. Even a pig would have remembered those four words by now. Apparently, the guy had slept through the whole lesson and could only repeat them.

Zhang Yuan paused for two seconds, then continued. "Let v be another known harmonic function on the plane D. By Green's identity, we have 0 = ∬(v∂u/∂n − u∂v/∂n)dδ. Subtracting the two equations gives us... Considering the boundary conditions..."

"￥@...%￥"

A few top students pricked up their ears, vaguely understanding what he was saying.

The more they thought about it, the more it seemed right—not nonsense at all.

If someone could spout nonsense at that level, they'd be incredibly impressive...

Whispers spread through the classroom.

What was going on?

A guy who'd been sleeping had just crushed every one of them!