breathe me right
In relativity, movement is continuous, causally determinate and well defined, while in quantum mechanics it is discontinuous, not causally determinate and not well defined. -—David Bohm

He thinks he'd probably define her by quantum theory. She is not continuous and she behaves like all different things at once and if he knows how fast she's going somewhere then he'll never know where she's going. She is random and complicated and utterly completely different from everything else he knows.

He likes to talk a lot about physics but he doesn't really understand it.

"Stop me," she whispers against the skin of his neck one night, "Make me stop."

He doesn't so she doesn't and it's okay because relatively there's a large chance they don't even exist at all so what does a sin or two matter in the grand scheme of things?

The next morning he wakes up next to her and he's a little bit surprised because he didn't have her pegged as the sort of girl who stays over afterwards. But her hair is a rumpled golden storm on the pillow and her face is pressed into his bare shoulder and she's there. Bright and breathing and there.

"Dominique," he murmurs, moving his shoulder away and taking her elbow, giving her the tenderest of shakes, "Dominique, you have to wake up. We're late."

Her eyes blink open, green in the sunlight falling through the window, and they just look at each other for a few moments. Quantumly this moment is probably definable but not any other way.

"No offence," she says indistinctly, her voice thick with sleep, "But I'm skipping your class today. Atmospheric charms bore me to tears."

Before he can reply she has rolled over and presented him with her back and he just leaves her there because in the morning reality feels a bit more solid and sins matter more when you're sure that you exist.

He feels guilty and tired and her cousin James glares at him accusingly all through seventh year Charms and he doesn't make eye contact—if James Potter was physics he'd be the Hadron Collider because his capacity for destruction is terrifying and as a probably-existing human being the odds for his survival are not good. So he teaches and James glares and that's how lessons will be from now on, he reckons.

At break time, she is still in his bed. She's barely moved, apart from an arm tossed aside. He kneels by the bed and shakes her awake again, more roughly this time. His guilt is eating away at him even if it probably doesn't really exist.

"Fuck off," she mumbles, trying to turn over, and he guesses he really didn't get it when she told him all that time ago how much she loves to sleep, "I'm asleep."

"You have Herbology in ten minutes," he tells her, and she blinks her eyes open, grey now without the light on them, and fixes him with a very scary scowl.

"I said I'm asleep."

"Dominique," he says, and why is he even doing this, he's not her minder, "Get to Herbology."

She stares at him for another few seconds and then, very distinctly, says, "Fuck you," and throws back the duvet and storms past him. She disappears out of the door wearing his shirt and nothing else and he stares at her school uniform scattered all over the floor of his chambers and thinks that it's okay because there's probably a million other universes where she stayed and he wasn't an idiot and maybe in a couple of them they're married already.

She's back in his bed that night and the night after and the night after that and he wonders if they're infinitely bound together or infinitely non-existent or maybe they're both just dreaming from separate sides of a tank and really when it boils down to it he reckons that physics overlap with philosophy quite a bit.

He spends the early hours of Monday morning with her head pillowed on his arm thinking about being dead and alive at the same time and if cats are allowed to date their students.

She wakes up earlier than normal and kisses him languorously and with her mouth on his and her skin dragging against his he doesn't have the capacity to think of anything except the certainty of existing, the certainty of her and her lips and the heat of her body.

Six months later he still doesn't know where it began or where it's going to end but Dominique keeps telling him that they all came from the stars and stars don't mind about being teachers or students and that doesn't make sense because stars can't think but he kisses her on the platform at the end of term anyway.

She smiles when they part and tells him he is a star to her and the cliché makes him gag and she laughs and hits him and being close to her makes the horrified stares all around them worth it.

She is grounded for a year and he is fired but he probably doesn't exist anyway so it's not that big a deal. He tells the headmistress that sinning is relative when he is summoned to her and that he and she and everybody else are just stardust when it comes down to it so what he and Dominique have is just life and it's natural and he reckons Schrodinger's cat would be rooting for them.

The headmistress says she thinks he could do with a few months in a mental asylum and he doesn't know how to tell her that actually his brain works fine, it's just that the fact of it is that it's Dominique and she's a bit blinding and he can't define her physically but he might able to quantumly.

"You're giving everything up for her," the headmistress says wonderingly, and he smiles and stands and wonders if his thoughts are made of stars since his bones and flesh and blood are.

Probably, he reckons—if anything's going to be stardust it'll be his thoughts because they exist even less properly than the rest of him, maybe, or not, whatever, and, "No," he replies firmly, "No, I'm not giving up anything. I'm gaining everything."

They have a baby called Adrian two years later and he sings him songs about cats and existence and Dominique laughs and philosophises about what babies think and somewhere in the middle of it all there's a moment where he feels like he might be able to define his wife physically, now, like she is ebbing less quantumly.

That night he maps the ridges of her ribs and pictures the way they web around her heart and taps simple melodies against her bones; one two three, one two three, one two three, one.

"I love you," she murmurs, fingers drawing soft circles on his scalp, "Dead or alive or both, I love you."

He lifts his head and meets her gaze, blue in the darkness, and he just smiles. "Let's get a cat."