This time, Gellert did look up. His gaze met that of the man who stood just next to him, and for a moment it was as if some part of Gellert's consciousness had intended to delve into his mind, peeling into his brain through his eyes, using Legilimency to suss out the man's motives. But of course, he realised belatedly, without magic a glare was just a glare. There was nothing to be seen behind the barman's eyes except for cool, impenetrable blue.
"Of course I have," he said after a moment. His tone was a little bit snippy, he knew, but what else could one expect when Gellert had just been interrupted by a man who clearly thought he knew enough about magical theory to have any worthwhile input into Gellert's work? "However, Agrippa's calculations only work if one accepts that magic exists in eight universal dimensions. I do not. I would postulate that there are twelve."
Gellert turned his gaze back to his paper and did a quick mental calculation, writing out another line of equation below all the ones preceding it. His handwriting was, as ever, too quickly scrawled to ever be appropriately termed 'neat.'