Scientific Rivals

Over at cosmicvariance they have a post about a topic we have discussed in the group before, scientific enemies/nemesis, those people that work in your sub-field and for whatever reason you don't get on.

The cosmic variance article gives some handy hints on how to choose your own personal scientific nemesis, I myself already have one, it only took one chance meeting for me to decide on them, I'm sure that in all probability they are a decent person, just something about them rubbed me up the wrong way. I'm looking forward to many years of run-ins at conferences to come, in all probability without them ever realising I dislike them.

Does anyone else have any professional enemies?