Can I bring my DSLR into a concert?

I'm going to see Justin Bieber in less then a month.
I have a Nikon D3100 and I really want to bring it in (to take pictures!)

I saw him back in 09 and I brought a little point and shoot, but it's really small and doesn't take good pictures.
I'm bringing a purse too.

Photography is generally forbidden in concert venues. Take a look at your ticket, and at the website for the venue.
For example, I looked at the info for the Joe Louis Arena in Detroit on Ticketmaster. It clearly states "Cameras and recording devices are typically not permitted. " http://www.ticketmaster.com/Joe-Louis-Arena-tickets-Detroit/venue/65554
Newark's Prudential Center is slightly different: "Small, non-professional still cameras may be brought into Prudential Center. Please note that for certain events cameras may not be allowed into the arena."
http://www.ticketmaster.com/Prudential-Center-tickets-Newark/venue/16847

It depends on where you go. You should go to the website for your concert venue and check their policies or FAQ. In most cases, from my own experience, photography is allowed as long as you don't bring a large flash attachment with you. However, there are a few venues where they strictly forbid photography. Look it up!