I'm in a bit of a specific situation and wanted to hear everyone's thoughts. I worked on a personal project in my undergraduate with no collaborators. This was just a one-off thing I decided to try for fun and worked on it on my senior year and the summer after my senior year. However, it ended up giving really good results. If nothing else, I would like to put it up on ArXiv. I have published papers during my undergrad but this project was different as I did not have an advisor or work with anyone. Now I am at a new institution doing my PhD.
My question is should I list my affiliation as independent research, as my undergrad institution or my new PhD institution. I don't want to accidentally commit an academic faux pas!
While this question: What to list as affiliation when work spans multiple institutions? is similar. I feel it doesn't quite answer my question as I'm not sure if it's fair to list either institution as technically I wasn't supervised for this project.