Can authoritative name servers have the same domain name for which they are authoritative of?

Yes.  In fact, many web hosts offer what is called "private name servers" which allow you to use your own domain for your name servers.

For example, if your website is example.com, you can setup name servers with the domains ns1.example.com and ns2.example.com

When you register them, each are associated with a particular IP address, which sometimes is the same as your web hosts's name server IP addresses.

For example, your web host's name servers ns1.yourwebhost.com and ns2.yourwebhost.com may be associated with IP addresses 198.51.100.1 and 198.51.100.2 respectively.  When you register your name servers ns1.example.com and ns2.example.com, your web host may tell you to associate them with the same IP addresses 198.51.100.1 and 198.51.100.2, which in a sense, makes them an alias of your web host's name servers.

If you have your own dedicated server or a different setup, your private name servers ns1.example.com and ns2.example.com might have their own unique IP addresses instead.

So it is possible, and widely used.

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