ALOOF
in a world of one's own
own aloof; detached; self-centered.John lives in a world of his own. He has very few friends.Mary walks around in a world of her own, but she's very intelligent.When she's thinking, she drifts into a world of her own.
live in an ivory tower
to be aloof from the realities of living. (Live can be replaced by a number of expressions meaning "to dwell or spend time," as in the first example.)If you didn't spend so much time in your ivory tower, you'd know what people really think!Many professors are said to live in ivory towers. They don't know what the real world is like.