# What Are Branes?

I just finished reading a book, and there was a section in it about string theory (Fabric of the Cosmos, by Brian Greene) And it talked a bit about branes, but I never really figured out what exactly they were (i thought I did when I read about it.) So, when someone asked me today what string theory was, I just told them it basically states that matter is made of tiny vibrating bands of energy, and when he asked me what branes were, I told him I was completely sure.

Simon Bridge
Homework Helper
They are the favorite food of 12D zombies xD

If you're comfortable with what strings are - branes are the generalization of strings to more than one strand. It's like the strings are the thread and the brane is the cloth.

There are many types of Branes p-branes , D-branes , M-branes . D-branes are extended objects where the boundry of open strings end

Thanks!

Check in the book Index:

for example, From FABRIC OF THE COSMOS: p385
I found:

The M framework...does contain ingredient besides (one dimensional) strings.....there are objects with p spacial dimensions....where p can be any whole number less than 10...p branes a are significantly heavier than strings

Also, try reading the book again...maybe taking some key notes.....I've been through most of it three times or so and gain a new perspective every time.

You can get other perspectives here:

http://en.wikipedia.org/wiki/Branes

Also check out Brane cosmology.....
http://en.wikipedia.org/wiki/Brane_cosmology

In aggregate, you'll find forces and particles live as strings, most strings live between branes, and branes live within the higher dimensional "bulk".

And for a step way beyond see here:
http://en.wikipedia.org/wiki/Cyclic_Universe#The_Steinhardt.E2.80.93Turok_model

These guys have a fascinating book: THE ENDLESS UNIVERSE that describes their model for laymen without heavy math...From what I recall, there seems to be some inaccuracies in the Wikipedia article...I can't find my copy of their book to compare.

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Very likely the best possible answer to the question that doesn't require detailed string theory knowledge can be found here.

Long story short, D-branes are just an emergent phenomena that are shown to arise from the interaction of open strings. Open strings end on them, with Dirichlet boundary conditions, hence the name. (Dont worry about what that means if you dont know)

(I took the liberty of answering the question for D-branes which are what "branes" most often refers to, but as others were saying there are other meanings of the word too)