I am a math PhD student in North America about to enter my second year. Last week I attended a conference and was interested in a research presentation by a professor at another school. The presentation was about some of his current (unpublished) methods and results to attack a problem in combinatorics. I am thinking of writing an expository post about his talk in my personal blog.
Question: Should I contact the professor to ask for permission to write about his research? My concern is that he hasn't published the results and so might not want to put them in public yet. I have seen people writing expository posts about talks or papers that they read or hear about (for example here), but I'm not sure if they need permission from the original author(s) to do so.