The taxi stopped in front of the campus.
Theodore paid the fare by card and got out. The cold wind burrowed into his clothes in an instant.
Whoooosh—
“Damn, it’s cold.”
Massive columns that called the Parthenon to mind stood before him.
“They really built something like this right on the boulevard?”
Pulling his coat collar closed, he tugged open the heavy door.
Inside the long corridor, there was the distinctive wax smell of the Infinite Corridor, mixed with the aroma of coffee. The walls were packed with posters and seminar notices.
[Geometry Seminar Tonight - Other Departments Welcome]
[P-Set Night, Everyone Behind on Assignments, Come One, Come All]
[“You Can Do It Too.” - Linear Algebra Study Group]
[Blackboard Cleaning Volunteers Wanted - Please note that all blackboards will be erased at 6 p.m.]
Theodore scanned the notices on the wall as he quickened his pace. When he reached the end of the corridor, he saw a blue sign.
[Department of Mathematics]
“Looks like this is the place.”
He pushed the door open and stepped inside, and a familiar atmosphere greeted him.
A printer ran without pause, spitting out papers.
On the shared table, half-finished cups of coffee, several math journals, and calculation notebooks lay in a chaotic jumble.
“I guess math people look the same wherever you go.”
Theodore let out a soft laugh at the smell of chalk tickling his nose.
The tension drained from him on its own.
After walking a little farther, he saw the reception desk.
“Excuse me. Would it be possible to meet a student in the math department named Yu Seoha?”
“Who are you?”
The staff member narrowed her eyes and looked up at Theodore.
Theo decided to understand her with a generous heart. Even back when he had been at his peak, there had been no shortage of suspicious people coming to the school looking for him.
“I sent an email yesterday... I’m Theodore Lanford from Stanford.”
When he presented his student ID, the staff member’s tone softened slightly.
“I can’t give you a student’s personal information. But I can tell you the places Seoha often goes.”
Theo nodded.
“That’s enough.”
The staff member put on a professional smile and said,
“He seems to be studying alone these days. I heard he’s been stuck on the same problem for several days...
He’s often by the windows at Hayden Library or at Barker Café. If not there, try the classrooms or his private research room.”
Theo was startled.
An undergraduate had a private research room...?
“Thank you.”
He headed straight for the cafeteria.
He made two rounds, from the entrance all the way to the deepest corner, but he couldn’t find the face he had seen in the newspaper.
‘Not here.’
He was about to leave when the savory smell of bread tempted him.
Grrrr.
For the past twelve hours, the only thing he had eaten was the miserable in-flight meal the airline had served him.
Hard, stale crackers, cheap orange juice in a plastic cup, and a dreadful sandwich whose vegetables had all gone limp.
He had forced it down because he was hungry, but it was a taste he never wanted in his mouth again.
‘Surely they won’t refuse to feed me just because I’m an outsider.’
Muttering to himself, Theo took a card from his wallet.
Conveniently, there was a shop nearby with a sign that read “Open to the Public.”
He ordered a hot coffee and a bagel.
The freshly baked bagel was clearly different from the ones he had eaten at Stanford.
It was not the sweet West Coast style, but a New England-style bagel with a chewy texture and a deep wheat aroma.
After lightly toasting it, they slathered it with plenty of cream cheese. Sesame, garlic, and onion were mixed into it, giving it a plain yet rich East Coast flavor.
“It goes well with coffee.”
Beyond the window, snow flurries drifted through the gray sky.
He gazed outside for a moment, then rose from his seat.
It was time to move again.
“Where the hell is he?”
As the staff member had said, he had searched both the library and the cafeteria, but he couldn’t find even a trace of him.
‘Is he not at school?’
He started to think he had flown over far too recklessly. As a last resort, he decided to stop by the office and leave a note.
Entering the math department building from outside, he saw a blackboard wall stretching long along the corridor.
“Wow!”
Both walls were entirely blackboards.
Before the endlessly unfolding wall of numbers, Theo shivered for a moment.
He walked slowly, scanning the blackboards.
Calculus of variations, topology, geometry, Ricci flow...
‘This derivation method is...’
Theo stopped walking for a moment.
It was the very formula that had once made his name stir up the world.
A smile formed on his face of its own accord, filled with pride.
True to its nickname, the “Infinite Corridor,” the hallway continued on and on.
[Who solved an electromagnetism problem here?]
└You guys solve math problems everywhere too.
└Huh? You’re right. Sorry.
Each blackboard had notes left in different handwriting.
Among the playful scribbles were traces of serious inquiry. Finding the undergraduates’ passion endearing, he let out a small laugh.
As he kept walking, one blackboard caught his eye, standing out from the others. Written on it was content he could not understand.
Theo stopped in front of it.
“Huh?”
Equations written in neat handwriting covered the blackboard.
He stared at them with wide eyes, but the writer’s intent did not come to him at a glance.
He decided to look for the starting point.
“Is this the beginning?”
This part was probably where it started.
The theorem concerning mean value. But the farther down it went, the more strangely the structure twisted.
Theo narrowed his eyes.
The equations were chaotic, making it difficult to grasp the content properly. Even so, after staring at them for a long while, he began to glimpse the flow of the formulas.
‘Is this an attempt to extend the mean value theorem to a non-uniform space?’
Integral signs and probability density functions tangled dizzyingly together, creating a new meaning.
The writer had been making various attempts, testing the possibilities of his own theory.
“Ah!”
Theo let out a short cry.
Step, step.
He retreated as far back as he could and looked at the entire blackboard from a distance.
Then he drew in a deep breath.
“No way... Smale’s mean value problem?”
It was a conjecture proposed decades ago by the American mathematician Stephen Smale.
A difficult problem asking whether a differentiable function in a non-uniform measure space still satisfies the mean value theorem.
Theo’s heart began to pound rapidly.
‘That can’t be. There’s no way an undergraduate would touch something like this!’
It was an old problem passed around quietly among analysts.
It had been an attempt to extend the mean value theorem to spaces where curvature and density were not constant, but at the time, it had failed to hold. The definition of measure had been affected by the function’s geometric structure, creating a self-contradiction.
Mathematicians back then had all said the same thing.
“It’s a problem of searching for a mean value that does not exist.”
And so no one—not even Smale himself—had ever completed the paper.
Most likely, young mathematicians today did not even know this problem existed.
‘Not me, though...’
He had always been interested in unsolved problems.
It had been for the sake of getting ideas for his master’s thesis, but at times like this, it helped him in unexpected places.
Theo moved along, following the clues left on the blackboards.
“He set the weights nonlinearly.”
The writer’s handwriting continued at regular intervals.
As it did, the abstract idea gradually took concrete shape, one piece at a time.
“Here, he set the function as a probability density. Don’t tell me he tried to replace the concept of mean value with a probability space?”
He thought the person was truly fearless.
It was a method that could become enormously complicated, but the writer did not fear expanding the concept.
He moved again.
At the end of the corridor was a window, and beneath it was a small blackboard as well.
The equations written there were in an extremely rough hand, as though written in haste. The chalk color had faded, as if several days had passed.
A theorem that had advanced the approach using probability theory and geometry much further.
The writer had finally succeeded in formulating this bewildering concept into equations.
Only now did the whole picture become visible.
The traces of intense thought left behind by some mathematician.
Formulas had been erased and rewritten several times. And countless newly added annotations were scattered messily here and there throughout the corridor.
“Does he have no intention of publishing a paper?”
This proof had no system.
It simply left behind the ideas that occurred to him as they came.
The development of an equation would break off midway and then suddenly continue on the blackboard beside it. There were no arrows or connecting lines between symbols or sentences.
Only the writer himself would be able to fully recognize it.
‘Was he on his way to class? Or mealtime? It looks like he scribbled it down so he wouldn’t forget...’
The writer must have picked up a piece of chalk and left traces during brief moments while moving to the library or a lecture hall.
He stopped before one formula that looked as though it had been written casually.
‘This idea is far more profound than it looks. If expanded just a little, it could produce a paper worthy of a major journal.’
Dazzling insights that seemed impossible to come from an undergraduate were scattered all over the corridor.
“Tch!”
Theo clicked his tongue.
Because he felt like he knew the writer’s identity.
Turning the corner and walking a little farther, he saw a student in a gray hoodie standing by the window.
The student stood motionless for a long while, as though pondering something, then twirled a piece of chalk with his left hand and began writing equations with fierce intensity.
At some point, the snow had stopped, and sunlight peeked out from between the cloudy skies.
When the light filtering in by the window illuminated his face, Theo’s eyes widened. He had grown quite a bit, but it was the very face he had seen in the newspaper.
‘Yu Seoha!’
For a moment, Theo tried to open his mouth, then hesitated.
He was too absorbed. On top of that, the fact that Theo did not know what Seoha was currently doing strangely wounded his pride.
Theo moved around the nearby blackboards, tracing Seoha’s thought process.
He followed the equation being written now with his eyes, tracking where it had begun and in what direction it was flowing.
He felt as though he were walking through an enormous maze.
Seoha’s thoughts moved by intuition rather than logic, and from time to time, they sharply changed direction.
Even so, there was a consistent axis within them.
When all the scattered ideas were gathered together, they were headed precisely toward the same conclusion.
‘Was I too focused?’
Before he knew it, the sun was setting.
Startled, he turned his head and saw Seoha looking at him.
“You’re the first person to properly recognize this.”
At Seoha’s words, Theo bared his teeth in a grin.
“Of course. If it hadn’t been me, no one would even have noticed. But why are you solving a minor hard problem like Smale’s problem?”
Seoha tilted his head.
“Smale’s problem? What’s that?”
“What you’re doing right now. This is a problem Stephen Smale proposed in the seventies.
You were the one who said it to me first in the first place. That I’d managed to recognize this.”
Seoha blinked as if he didn’t understand.
“I meant, did you know how interesting this problem was? I thought Rojia had made it...”
Theo pressed a hand to his forehead.
He had forgotten about Rojia’s existence all day today.
He could guess what had happened.
Rojia, having failed to create a problem Seoha could not solve, had shoved an unsolved problem onto him. And Yu Seoha was solving it without knowing that.
“That goddamn tin can... So, have you made any progress?”
Seoha nodded innocently.
“Yes! I think I can probably solve it in a few days.
I had a hard time because I’ve never studied analysis in depth, but over the past few days, I’ve definitely gotten the feel for it.”
‘Solve it in a few days? Smale’s problem? And he hasn’t even studied analysis?’
While Theo was reeling in shock, Seoha asked him,
“By the way, who are you?”
‘I thought he recognized me.’
“I’m...”
He could not finish introducing himself. Because the clock hanging at the end of the corridor caught his eye.
‘5:50.’
Something tickled at the back of his mind.
The feeling that he was forgetting something important. Whenever this happened, something big always broke out.
Theo desperately set his mind turning.
And at last, he remembered the notice he had seen while passing by that morning.
[Blackboard Cleaning Volunteers Wanted - Please note that all blackboards will be erased at 6 p.m.]
Theo shouted urgently.
“Damn it! All the blackboards are going to be erased at six. We have to go stop them, now!”
“What? Why?”
Seoha looked as though he had no idea what Theo meant.
“All the ideas you wrote on the blackboards are going to disappear!”
“I don’t mind? I remember the overall flow, and...”
“Don’t say something ridiculous! How could you remember all that?
There might be clues among them that could provide important inspiration to mathematicians!”
Theo’s voice rang thunderously through the corridor.
As a mathematician, he could not stand by and watch valuable ideas disappear.
“Huh?”
Seeing Seoha standing there blankly made his blood boil.
“Damn it! Why do I have to!”
Theo clenched his teeth. Then he began running toward the department office with all his might.