Even though he had solved all the Smale problems, Seoha could not fall asleep.
A sticky sensation that he was missing something lingered in his head, tormenting him. But he could not figure out what it was.
“What could it be? It’s so unsettling.”
Scrub, scrub.
When he came to his senses, he had been brushing his teeth for over ten minutes.
Whether eating at the cafeteria or walking down the street, Seoha could scarcely free himself from that thought.
As night fell, the sensation grew even clearer.
When he closed his eyes, the formulas written on the blackboard squirmed. And like snakes, they slithered up and coiled around his body.
Seoha felt as though his chest would burst from the frustration.
“What the hell is the problem?”
He got out of bed and opened the window.
The cold night wind assaulted him. The biting chill seemed to cool his feverish head. As his mind cleared, he was able to find the part that troubled him.
‘No doubt about it. This sinister feeling.’
Seoha stayed up all night with unblinking eyes.
And the moment dawn broke, he dashed out to the laboratory.
* * *
*Buzz—*
A cheap motel in Cambridge.
Teo, who was checking his master’s thesis, picked up his phone.
—Hello. This is Seoha’s mother. It’s dinnertime, but I can’t reach Seoha, so I sent a message. I made galbijjim for the first time in a while... Are you two together? If so, please come too, Teo.
“What is this guy doing?”
Teo frowned and replied as politely as possible.
—I’ll go look for him.
He threw on a thick jumper bought during the Christmas sales and stepped outside the motel.
Because he had often come and gone from their house while writing his thesis, Teo had grown close to his family. It was now a relationship where sharing a meal wasn’t awkward.
Winter nights fell unusually early in Cambridge.
With exams over and the year-end approaching, the campus had grown quiet. Most of the laboratory lights were off, and Christmas decorations hung in the hallways.
Many students had returned to their home countries or left for their hometowns. More than half of MIT’s buildings were already empty.
“I’m not even a student at this school...”
He fiddled with the temporary pass issued by the math department. Until the colloquium ended, he could freely come and go from the school.
Had he already grown accustomed to this school?
It was dark, but finding his way wasn’t difficult.
As soon as he entered the math building, the distinctive smell of chalk hit him.
It was quiet. The labs, the lecture halls, even the library were closed with hardly any human presence to be felt. But after walking a bit, a faint light leaked from the end of the second-floor hallway.
*Creak.*
Teo confirmed the light escaping through the door crack and opened it.
Symbols, sequences, graphs, and the Smale problem filled the blackboard.
Seoha stood under the window light. His sleeves were coated in chalk dust, perhaps from writing and erasing extensively.
“Your mother is looking for you.”
Teo sighed as he approached.
Instead of answering, Seoha pointed to one side of the blackboard with his fingertip.
‘Hm?’
Incomprehensible formulas were written there.
Teo stood there for a long while, reading them.
‘What is this?’
The equations refused to register.
All Teo could make out was that it was related to the Riemann zeta function.
Seoha licked his dry lips, then picked up the chalk again and began writing symbols from the corner of the blackboard.
The rhythmic sound of chalk echoed through the room.
Scratch, scratch.
“While solving the Smale problem, I realized something.”
Seoha filled the remaining corner of the blackboard.
“Smale’s conjecture is premised on the idea that ‘even if the form of space changes, its essence is preserved.’ But in reality, that’s not the case.”
“Because continuity breaks at the boundary.”
Seoha nodded.
“If you transplant Smale’s stability condition into the space of the zeta function, something interesting happens. The zeros of the Riemann zeta function are revealed only under analytically stable conditions.”
Teo was greatly surprised.
The two spaces had fundamentally different structures. Direct application should be impossible...
“Is that possible?”
“If you extract just the conditions, you can apply it roughly.”
Teo sincerely marveled.
The power to knead space-time at will.
Where on earth was the end of this boy’s mathematical ability?
“Even so, it’s an incredible discovery.”
Since it couldn’t be proven, it would remain merely a persuasive conjecture, but—
“You could write a paper or so. But unfortunately, there is currently no way to travel between the two worlds without error. To do that, you would need a common language that ties together topology and analysis, space and sequences...”
What on earth did this guy want to do?
Teo let out a hollow laugh.
“That’s truly at the level of creating an entirely new field of mathematics.”
Seoha smiled as if amused, then stretched both arms up high.
“I’ll be able to do it someday. Ah! That’s refreshing. It feels like a thorn stuck in my head has been pulled out. Now I can be a little more comfortable.”
“You’re a severe case too.”
Looking at Seoha, Teo recalled an anecdote about Euler.
‘V − E + F = 2’
Euler had revised this formula for over 30 years. Because it didn’t hold for some complex polyhedrons.
Everyone around him had said it was sufficient, but the standard of sufficiency differs from person to person. He must have needed to know the reason.
Seoha was fundamentally the same.
Until he dissected the hidden order within the Riemann zeta function, he would never stop.
“Teo, you know a lot about difficult problems, right?”
Caught off guard by the sudden question, Teo stammered.
“Huh? Y-yeah. I suppose so.”
As if lost in thought, Seoha was silent for a moment.
Then he opened his mouth with difficulty.
“I... I’m planning to challenge as many difficult problems as possible from now on.”
His eyes were resolute, as if his mind was already made up.
“Suddenly?”
“I’ve felt something while tackling difficult problems so far. They all had different appearances, but they might essentially share the same root.”
The difficult problems Seoha had solved were the Four Color Theorem and the Smale problem. And he was also deeply involved with the Riemann Hypothesis.
His experience with difficult problems was already far deeper than that of ordinary mathematicians.
“In what way?”
“That the answers lie in regions beyond human consciousness? Or should I say, they pierce the gaps in the way we understand the world.”
It was a convincing explanation.
“An interesting idea. But it makes sense. Difficult problems are often solved by changing the approach. So you’re going to fill that gap?”
Seoha nodded.
“I have a feeling that would bring me a little closer to proving the Riemann Hypothesis.”
Teo was at a loss for words.
Anyone hearing it would think it the delusion of a genius. Nevertheless, Teo couldn’t dismiss his words. Because the moment he heard them, he couldn’t help but think they were persuasive.
‘No, do I just want to believe that?’
Seoha had a strange power.
A subtle magnetism that transcended logic or evidence.
There was a mystique that made everything he said feel as though it would become reality.
“I also finished my master’s thesis thanks to you. I had held onto it for two years without results, but in just a few weeks.”
Teo gave a bitter smile.
“Really?”
Seoha rejoiced as if it were his own achievement.
Teo looked at Seoha with a complex gaze.
How many difficult problems would this boy solve in the future?
‘I want to see.’
He wanted to see with his own eyes what path he would walk and what lay at its end.
He wanted to witness the entire process right beside him, just as when he solved the Smale problem. And if possible, it was his honest wish to be of help to him.
“Ah! Mom!”
Seoha startled, as if only now remembering.
The two hurriedly tidied the laboratory and came out.
On the way home, Seoha glanced at Teo.
“Are you coming with me?”
“The dinner menu is galbijjim.”
Teo could never forget the first day he tasted Miyeong’s galbijjim.
He had thought it would be a stew like Beef Bourguignon, but galbijjim was a dish of a different texture.
An inexplicable taste somewhere between barbecue and stew.
A slowly simmered sauce seeped between the tender meat fibers, creating a fantastic flavor.
Teo was already deeply captivated by the charm of Korean food.
* * *
When the year-end arrived, everything in America stopped.
Companies went on vacation from Christmas week, and schools closed their doors.
Once-crowded roads became quiet, and even cafes and restaurants operated on shortened hours.
But the quiet city changed its appearance in the afternoons. Trees with lights turned on, shops playing carols, people with shopping bags in both hands.
For the retail industry, this season was the biggest sales period of the year.
Department store and outlet parking lots were always full, and the shopping districts were packed with people eyeing Christmas and year-end sales.
Discounts were a whopping 50 percent or more.
It was easy to find people who came out at dawn and lined up in front of stores.
Seoha too had come downtown Boston with his family to enjoy the year-end.
“Oppa! Look over there! It’s a huge tree.”
A giant Christmas tree standing in the middle of Boston Common (a large park in the center of downtown Boston) boasted a majestic presence.
Countless light bulbs wrapped around the tree sparkled like jewels.
Seoeun had a shocked face, as if she had come to a world of stars.
The difference between the Christmas scenery of Okcheon downtown and Boston was that great.
“It’s pretty, right? Let’s play around here for a bit.”
Miyeong said.
Seoha held Seoeun’s hand tightly so as not to lose his sister among the crowd.
Seoeun’s eyes were wide as she looked around in every direction.
Carols could be heard from somewhere.
—Jingle bells, jingle bells, jingle all the way!
Seoeun sang along in an excited voice.
The couple successfully pushed through the crowd and snagged children’s clothes from a luxury brand they usually only eyed.
“Hurry and try them on!”
“Seoha, take off your outerwear quickly too.”
A bright yellow padded jacket; Seoeun’s was a vivid red.
As the two changed clothes, the couple smiled with satisfaction.
“We won’t lose them anywhere now.”
“Right. They stand out perfectly.”
Seoha made an embarrassed expression.
He usually wore whatever was given to him without complaint, but the primary colors of this padded jacket were overwhelming. He imagined himself walking around MIT in this outfit.
A glaring yellow standing out conspicuously among the achromatic nerds.
‘Ah...’
He felt so ashamed he thought he wouldn’t be able to raise his face.
“It’s the same as oppa’s?”
Seoeun flapped her hands and ran around, delighted about something.
Seeing that, a laugh naturally came out.
‘Maybe it’s not so bad.’
Seoha smiled and zipped the padded jacket all the way up.
The family returned home, lit candles on a small cake, and celebrated their first Christmas in America.
A year passed and the new year dawned.
Miyeong went all the way to Allston to find a rice cake shop in Koreatown. Because she wanted to feed her family freshly made rice cakes.
“The tteokguk is delicious, Mom!”
Seoeun blew on the steaming tteokguk and ate.
*Munch.*
With every bite, a happy smile spread across her face.
“Hehe, of course. I made the broth with brisket myself.”
She smiled brightly, as if just watching them was enough to make her happy.
“Thank you, Mom. It’s really delicious.”
Seoha also gave a thumbs-up.
On New Year’s morning, eating tteokguk in a foreign land felt unfamiliar, yet it warmed a corner of his heart.
After a few days, the stopped city began to move again.
The excited year-end air settled, and the campus returned to its original appearance.
And the MIT math department had to move more busily than anywhere else.
“Can attend” messages flooded in like tidal waves from universities and research institutes around the world.
*Click.*
*Click.*
Wearing a rented suit, Seoha struck the pose the cameraman ordered.
Holding chalk, standing in front of the blackboard, handsomely raising his hand...
“Yes, that’s perfect right now! Smile!”
*Click.*
Seoha had the face of someone whose soul had left his body.
He had never imagined it.
That he would become the model for the colloquium poster.