1)If you're running a one author blog, the author archive will be exactly the same as your homepage. This is what's called a duplicate content problem. If this is the case on your site, you can choose to either disable it (which makes it redirect to the homepage), or to add noindex,follow to it so it doesn't show up in the search results.
what is this ?
2) what is the default setting in archives?
Author archives> where to mark enable or disable
Meta Robots> where to mark enable or disable