What Are N-Dimensional Objects in Superstring Theories?

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Discussion Overview

The discussion revolves around the nature of N-dimensional objects in superstring theories, specifically focusing on the concept of N-branes and their relationship to strings and other types of branes. Participants explore theoretical implications, definitions, and distinctions among various brane types.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that N-dimensional objects, referred to as N-branes, extend the concept of one-dimensional strings in superstring theories.
  • Others question the differences between N-branes and d-branes, seeking clarification on the types and characteristics of branes.
  • One participant mentions that d-branes, discovered by Joe Polchinski, are a specific type of p-brane, which was initially studied in supergravity contexts.
  • Another participant explains that p-branes are described by specific spacetime metrics and background fields, while d-branes are adapted to string theory frameworks.
  • There is a discussion about the relationship between fundamental strings and branes, with one participant noting that strings can be viewed as one-dimensional versions of p-branes.
  • One participant references the Lagrangian of Dp-branes as a generalization of the Nambu-Goto action for strings, suggesting a deeper connection between these concepts.

Areas of Agreement / Disagreement

Participants express various viewpoints on the definitions and relationships among different types of branes, indicating that multiple competing views remain without a clear consensus.

Contextual Notes

Some claims depend on specific definitions and theoretical frameworks, and there are unresolved questions regarding the implications of different types of branes in the context of superstring theories.

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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?
 
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N dimensional objects are called N-branes.
 
How does it differ from d-branes, and how many types of branes are there?
 
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...
 
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.
 
MathematicalPhysicist said:
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?

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.
 

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