Do Lucene Deletes delete the physical file? If yes, is there a way not to?

Is it possible to delete a document from the index, but not the physical
file. And also I'm wondering what the functions are that will alter the
physical files being indexed.

a side note: what is the best way to look up information like this so I
don't have to bug the java-user mailing list for simple questions like this?
I tried googling, but didn't seem to get the information I wanted. Thanks!

David Lee