Jennifer Connelly was married to Russell Crowe for only four months, but the experience was so stressful it made her take up smoking. Sitting in a West Village boîte, one leg folded beneath her, she guiltily hides her cigarette behind the banquette.

"I don't want to be a smoker," the 31-year-old black-Irish beauty says, sighing into an iced tea that happens to be the entirety of her lunch. "It's so completely antithetical to so many things about me."

Don't worry if you haven't heard of the Connelly-Crowe nuptials—they exist only in A Beautiful Mind, director Ron Howard's troubled-people-are-loveable-too biopic coming to the nation's popcorn plazas this December. Connelly plays better half to Crowe's John Forbes Nash, Jr., the Nobel Prize–winning mathematician whose battles with schizophrenia nearly buried him.

The Oscar-winning Crowe may get to play the titular egghead (a Rain Man–flavored role that many have whispered is sure to win the surly Australian another statue), but Mrs. Nash was certainly no Stepford slouch. Female theoretical physicists at MIT weren't exactly a dime a dozen in the fifties, and Connelly coveted the role from the minute the script shook up her in-box. "It was a no-brainer," she says of her decision to try for the part, pun completely unintentional.

According to Howard, Connelly beat out a number of A-list stars. Her own academic achievements may have helped:She studied at Yale and Stanford. All that homework, she says, made her extra simpatico with her character, right down to the rant-and-rave ugly stuff. "She's not like this impossible martyr that none of us can relate to," says Connelly. "She's real."

Many critics have reached a similar conclusion about Connelly—her talent is bona fide. Although her filmography includes such fluff as Italian horror flicks, The Rocketeer, and Jim Henson's Labyrinth, of late she's become far pickier in her hunt for high-protein roles, like the hopeless heroin addict she played in last year's Requiem for a Dream. This may be why Tinseltown talking heads have declared A Beautiful Mind Connelly's break-out vehicle, the movie that will do for her what Shakespeare in Love did for Gwyneth.

Ask Connelly about all the prognosticators busily handicapping her for Access Hollywood's most-wanted list, and she turns blasé. All she's looking for, she insists, are a few more meaty roles.

"To me it's not about ..." she says, incapable, it seems, of dreaming. "I don't know," she finally adds, 'I lead a pretty simple life."

Of course, all that Hollywood-stardom stuff may be humdrum because Connelly's current life includes playing parent to a demanding 4-year-old co-star. (Kai, her son by former boyfriend David Dugan, a photographer, lives with her in New York.) Motherhood, she explains, has a way of making you want to take your next career move more seriously—and to have more than "downloadably sexy" on your bio.

"Maybe her looks have gotten in the way a bit," concedes Howard, "but she's earning those opportunities now. I think her ambition has been awakened."