A/N: This is technically part of the If & Only If series of stories now. Please see my profile to see read order and all that jazz.

x sub n-plus-one equals x sub n + c is the Mandelbrot set, which is a type of fractal. There's a bit more to the definition than just that, but that's our main equation (the other thing to note is that it must remain bounded as it goes to infinity). I think fractals are very cool, as is chaos theory in general; I'd really recommend you go looking for fractal art to see why I'm so very fond of them.

This runs vaguely AU. Tony will still become Iron Man, one day. I have vague ideas for doing a much larger story that would pair with this one, detailing all sorts of interesting ideas, but for now that's some vague thing.

Enjoy the show. :)

Fractals

Tony's 17 and feeling reckless (surprise) when classes end. He's got nothing to do, tells his parents he's going to Chicago ("That's nice, dear" and a grunt from dear old dad), and he couldn't have ever told you why he picked Chicago of all places except it's one place he knows that dad isn't and won't go, because New York might be Stark territory but Chicago is entirely not. The opposite, really, they don't even have a house there, but he figures he's a Stark and the name might as well be worth fucking something.

He's right (of course). Everyone wants a Stark, wants Tony, even if technically Chicago is the empire of Odin and Sons. So he smiles, and the Friday he gets into town he's already at one of the rich and famous society events (not got anything on New York's theatrics, he can tell, everything here is old feuds and subterfuge, under the table deals, and the rich here don't know what to make of Tony and his wildness), drinking and laughing and debating if he wants a guy or a girl tonight, which is going to be the better place to wake up. Everything here is tame, it's almost refined, even if he knows it's all a fucking act (because isn't it always?). He's just about made up his mind, is angling and impressing and has this woman dangling on his every word when his eyes slip past her and towards the bar and sees:

Eyes staring back and everything fire and ice, birth and death, creation and destruction churning in one bottomless gaze. Infinity.

Gets his feet back underneath him, looks, and sees a young man, his height but thin thin thin, dressed in a suit and looking at someone tall and broad and blond, the tiniest bit of a smirk on lips to mirror the scowl that blondie is giving him.

Suddenly knows where he wants to be tonight.

He doesn't get there that night (though he is told, with a sly grin, that there are forty-three people not wearing underwear at the event).

Or the night after (when it is mentioned, in passing, that Tony has drank nearly one liter of alcohol and would he like to make that one point two?).

He ends up getting a penthouse apartment in the city because his stay in Chicago is not going like he planned at all.

They see each other all the time, every party, every event, every night (everyone wants a Stark, but all this Stark wants is him). The tension is killing him. Elder Stark calls, tells him to stay away from the kid (the paparazzi are all over this, because if they haven't ended up in bed (yet), they are inseparable as soon as one spots the other at any event), and Tony grunts in reply, whatever, because all he sees are poison green eyes and all he hears is laughter as wild and broken and wanting as his own. He knows the only reason Howard cares is because 'the kid' is Loki (one of the sons of Odin) and it doesn't look good but whatever.

"Loks," he says, drunk and them staggering in the rain slicked streets (and they haven't fucked, but they'll watch when the other fucks someone, and do, watch each other break beneath someone else's hands (or watch them make someone else break), wage war across other people's bodies, and unspoken in every gasp and moan when their eyes meet across someone else's flesh is this is for you). "Loks," he repeats, because Loki hasn't answered, is leaned into Tony as much as Tony is leaned into him and Tony knows they are hopelessly lost in Chicago and has no idea how to get back to the penthouse suite he wasn't going to need.

"Tones," Loki finally says, voice rough and burned by cigarettes and alcohol, and turns his face—right there, poison green eyes that Tony could stare at all day. And right then (and it's only been two weeks, two weeks of finding each other every night and pretending it's an accident, two weeks of bending other people over and fucking them with the promises of what Tony will do to Loki and Loki will do to Tony), Tony knows that he will never find someone who fits to him so well, who gets what he wants in bed, who fucks like Loki does. Knows he'll spend the rest of his life coming to Chicago or wherever Loki ends up, just so they can watch each other fuck other people if he has to, because there is nothingon God's green Earth like Loki's vicious smile when someone breaks under him—even if Tony never actually gets to be the one Loki's smiling over.

"We're lost."

Those eyes swing away, look around, then back to Tony.

"No. M equals two over seven." Loki's words are slurring, but he seems so sure. They go where Loki says (two blocks east, seven north) and they're back at the suite Tony wasn't going to need. They haven't brought anyone else back with them for the first time and Tony almost doesn't know what to make of that, except he doesand the gleam in Loki's eyes and the way Loki's licking his lips as he looks at Tony says Loki does too.

When Tony wakes up the next morning he's aching and sore, covered in bruises, bites, and scratch marks, his head pounding a muffled drum beat. The bed is empty (surprise surprise, all the sheets are on the floor, he's on the floor), Loki's pants are still by the bedroom door and the only confirmation that yes last night did actually happen. Loki's in the kitchen, staring at the display Tony had left up before going out, fingers playing with it and moving things around, cup of coffee in hand. He's got a pair of boxers on, hair a wild mess, and it's the very first time Tony has ever seen him sober, the first time he's ever wondered what Loki does when he's not drinking and partying (he is fairly confident that Loki is not stupid by this point, that he's probably passable at math (and Tony always assumes no one is as good as him at it, Loki's only 17, 17 year olds are not smart like Tony) but it's not like they ever actually talk when they're out). Tony staples it in his mind right next to all Loki's other firsts. He doesn't acknowledge Loki and Loki doesn't acknowledge him. Tony just pours himself a cup of coffee, sits down, and looks at what Loki is examining. Plans and code and prototypes of an AI, equations that are half-finished in some sort of an attempt to describe emotions. Loki's eyes are half-lidded, face smooth with the mask he wears whenever his older brother appears at a party to try and drag him home before he self-destructs (Tony knows that mask, wears it every time Pepper or Rhodey try to do the same to him).

Tony hates this. He's waiting on Loki to ask something stupid, to ask a question that Tony won't be able to explain properly because he doesn't fucking think like these other people, or worse try to comment and talk like he actually understands what he's seeing even though he doesn't. This was a mistake, bringing just Loki back, because the magic of Loki is he's not like other people—and now he's going to be with a question or comment. This is Tony's most hated part of his one night stands who see his work and feel like they need to connect with him (why can't people just leave it at fucking?). He's preparing himself for it—Loki's either going to try and impress him and fuck up his work so Tony spends all morning undoing it, or he's going to ask a stupid question, and Tony doesn't want either. Loki's mouth opens and Tony braces.

"Fractals."

Loki pushes aside everything except for one equation Tony hasn't even really started on—love—while setting his coffee mug on the counter. He picks up the stylus for the display; then, using the scrap of equation Tony had written, begins to discard variables. Tony is about to tell him to stop but his tongue catches as he watches Loki write long-hand (neat, precise, the edges of his letters jagged, lines leaned hard to the left) in the remaining space. It takes him less than a minute to write an equation, and for the next twenty minutes Tony watches as Loki writes out all the variables, writes a proof, writes the theorems that go with his proof so Tony can examine at his leisure later (and the entire time, the blank mask on Loki's face is easing into a half-lidded smile, as if there is nothing more satisfying for him in the entire world, just Loki and the math in front of him; even three sheets to the wind Tony's never seen Loki look so open, never seen him look so beautiful).

It takes Tony nearly five minutes to realize that Loki has stopped writing and has started drinking his coffee again, to tear his eyes away from the absolutely perfect thing in front of him, a thing he can actually use that is somehow a mathematical function of love, which Tony had left barely started after three sleepless nights. Loki is sitting there, watching him, face blank again. Tony looks back at the equation, then at Loki.

"JARVIS," Tony tells him.

And suddenly Chicago is wondering where its two largest party animals have gone. Oh, they do reappear, sometimes, sneak around, fuck back stage and giggle with their hands under the table, answer phones breathless and panting, but they don't bring anyone else back to Tony's place anymore, it's just them, tearing and devouring, drowning in each other. They sleep together, facing each other and limbs tangled, breathe in each others air and try to press closer (closer)-sleep and dream the same dreams; so much so it's a miracle they don't ache and hurt like old men, blood cut off and new kinks in their muscles when they first wake up. They drive out of town, out of the suburbs, and find a lake, wade in the water for a while, lay on the shore where Tony shows Loki where he's at next on JARVIS, and Loki watches, nods, and alters Tony's math (always for the better, because while Tony gets math, Loki lives it), and once they're done, Loki whispers in Tony's ear how many trees there are on this side of the shore, the ratio of ducks to geese that have flown overhead, the exact angle of the light hitting the lake, and Tony makes drafts of what Loki sees (because Tony, he gets it now, why Loki waited so long before he eliminated the other people (variables), because math is all Loki sees, because Loki's entire world is equations and numbers and angles, everything else is speaking a foreign language that twists and changes constantly, that's why Odin struggles so much with his second son even as he still loves him, why Loki buries himself in sex and booze and shallow relationships, why Thor can't bring himself to stop his little brother from imploding). It only makes Tony love Loki more, if that's even possible, like zooming up close and finding the pattern of his emotions is thesame, no matter how small the detail or quirk.

"Mmm... Tones." Loki hums one night, summer drawing ever closer to end, laying on the roof of the building.

"Hmm?"

"What does ' JARVIS' equal?"

"No idea, Loks" Tony says next to him. He's sitting, staring up at the sky, knows there are stars there but Chicago is too bright to ever see them. Passes Loki the bottle of whiskey they've been drinking, just enough to get a low buzz going in their systems. He thinks that's all Loki is going to say and nearly forgets (as much as he forgets anything he does with Loki, which is to say: nothing). They are walking down the street and heading to some opera thing that Loki insists on about an hour later (Tony's racing on adrenaline, because what's actually going on is the thrill of something they shouldn't do in public but are planning to anyway). Tony is thinking ( how Chicago is his favourite place, how he doesn't want to leave, how he has never met and will likely never meet someone else quite so perfectfor him) when Loki hums to indicate he's about to talk (which Tony adores, this quiet little thing that is so easy to miss, and which, according to Loki, currently 98% of people don't notice).

"Just a rather very intelligent system."

"What?"

"JARVIS."

Tony blinks for a few (because Loki's not one for coming up with acronyms, actively hates them because they confuse Loki more, because they aren't the variables he thinks they should be), then starts to laugh. Tony can't help it. It's perfect and utterly Loki, and Loki has probably spent the past hour trying to come up with something to fit since he asked Tony. It's a gift. That acronym, it's the best gift that Tony's ever gotten, ever, from anyone.

They end up missing the opera.

He's going to put JARVIS in his workshop at the end of summer, and he's got Loki coming back with him because JARVIS is as much (maybe more) Loki's now as he is Tony's and he wants Loki to get to hear JARVIS when he first speaks, before they have to part and go back to classes (and he's not surprised to find that Loki's working on a masters in mathematics (Berkeley, not MIT, and Tony mourns that and debates the wisdom of transferring in the middle of three degrees)). He's by himself waiting on Loki to arrive, Loki at dinner with his mother for her birthday, and he's looking through all the work they've put into JARVIS, and he stops to look at the very first equation, where he found out that Loki is a lotmore than just a good fuck. Fractals. As soon as Loki gets in, they go right back out, Tony dragging him off to a tattoo parlour, Loki laughing and curious.

They get matching tattoos (x sub n-plus-one equals x sub n + c), on the their left shoulders, above their hearts—Tony in Loki's handwriting and Loki in Tony's, and Loki is examining Tony's later that night, after sex, smiling, that same relaxed and easy smile he has when they're working on JARVIS. That smile that Tony uses to reaffirm to himself that, yes, Loki is all he will ever need, no matter what, because there is literally nothing more perfect that this math god who is tangled in his arms in bed, no one else who slips into his mind and heart and fills the spaces so perfectly (makes the equation that is Tony equal one). It's not the thing that's part of JARVIS—too long—but it's twined in the word (fractals) that Loki spoke before he showed Tony what he meant.

They're about to head out a few days later. He's waiting on Loki at the airport when he gets a phone call, but it's not Loki's voice on the other end.

"Stark, come to the hospital. Accident. Loki, he's-Stark."

It's like the bottom falls out, or up, the opposite of what happened that night he first met Loki's eyes, whatever, it doesn't matter, what does matter is Loki in the emergency ward, bleeding out, the doctors already knowing, Loki's eyes wild and Loki counting, Loki's hands moving, his eyes slipping and sliding over everything and clearly not understanding a word anyone else is saying. That's how Tony knows—because Loki is never so obvious about his need to count, because even when he's drunk Loki can still (usually) grasp English and right now Loki can't—right now he's visibly counting because nothing else makes sense. He's too pale and those poison green eyes are wide in terror and confused, tears spilling down his face, bleeding and heart stuttering on the monitor. The doctors know, everyone here knows, and that's why they called Tony, that's why Odin doesn't glare at him, that's why even with Loki bleeding to death the doctors let them in the room, and Loki, Loki is the only one who doesn't know what's going on, eyes wild, shaking, in pain, crying, lips stuttering and stumbling over numbers.

Loki's eyes calm a little when they see Tony, and he starts to spill numbers and variables. No one else understands, but Tony does, understands the half-formed equations are Loki asking what is going onand Tony, Tony can't help but cry as he tells him, in Loki's math, the missing variables, what Loki doesn't have, and Loki's face kind of stills, but it's not the same blank mask like when he's hiding; it just says 'oh.' He's gripping Tony's hand, starting to look so much sleepier, and shivering (Tony will never again be able to stand the cold, will always remember how Loki shivered in those last few minutes), and his finger tips are counting the lines in Tony's hand. They rest their foreheads together and Loki whispers (shivering, skin too too cold):

"X sub n-plus-one equals x sub n squared plus c."

Tony keeps himself from closing his eyes (because after this he won't ever see Loki's again), chokes back a sob, and gently runs his hand through Loki's hair, whispers the equation back to Loki, the equation tattooed on their shoulders, the equation that is in their hearts and blood and minds, the equation that says I love you infinitely and more completely and complexly than I can ever express.

Loki smiles at that, gratified, ecstatic, just before he closes his eyes.

Tony never talks about the tattoo on his left shoulder, never talks about fractals, never talks about angles of light hitting the surface of water. He never talks about how he came up with what JARVIS stands for or how he got the AI so human, never talks about how JARVIS is the only thing he has left next to memories of poison green eyes and a laugh, high and wild and free.