Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

N dimensional objects.

  1. Oct 8, 2009 #1


    User Avatar
    Gold Member

    Superstring theories attest that the building block is a one dimensional object, a string, now I wonder why stop there, why not two dimensional objects?
  2. jcsd
  3. Oct 8, 2009 #2
    N dimensional objects are called N-branes.
  4. Oct 8, 2009 #3
  5. Oct 9, 2009 #4


    User Avatar
    Gold Member

    How does it differ from d-branes, and how many types of branes are there?
  6. Oct 11, 2009 #5
    I've read of p branes and d branes.

    d branes are the ones discovered by Joe Polchinsky in the mid 1990's. I think I've read these are called Dirichlet branes

    p branes are the type discovered by Ed Witten and strings I think are one dimensional versions of these....

    Try this for an overview: http://en.wikipedia.org/wiki/P-branes

    got to go....
  7. Oct 11, 2009 #6
    P-branes are objects in supergravity and were studied first. They are described by a specific form of the spacetime metric and other background fields in the theory. You can consider them in string theories that have the supergravity theory as a low energy limit. D-branes are p-branes further adapted to the string framework. The "D" stands for "Dirichlet boundary conditions" for the string endpoints on the branes. The fluctuations of the D-branes are considered to be stringy excitations on the brane in contrast to sugra p-branes with (quantum) field fluctuations.

    Bergshoeff, Sezgin and Townsend (Phys. Lett. 189B, 1986) first considered p-branes based on observations of Hughes, Liu and Polchinski (Phys Lett B180 1986).

    Fundamental strings of string theory are a specific type of 1-brane, "electric", while magnetic 1-branes are solitonic solutions to a given theory. (This is a general thing: An electric 0,1,2,...-brane is not a true solution to a set of equations of motion; rather, they are objects coupling to a singular "solution" of the theory. On the other hand, magnetic branes are true solutions to the equations of motion.
  8. Oct 14, 2009 #7


    User Avatar

    Those are the branes... Isn't it?

    Look at the Lagrangian of Dp-branes, those are just the generalization of the Nambu-Goto action of the strings.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook