String Theory: Gravitons, Warping Spacetime & Supergravity

In summary, gravitons are a special oscillation of the fundamental string and do not interact with spacetime in the perturbative picture. SUSY is a unification of spacetime and internal symmetries and introduces a new symmetry that acts as a "ladder operator" between particles. Local SUSY leads to the introduction of the graviton field and its fermionic partner, the gravitino field, as the gauge bosons of Poincare symmetry.
  • #1
cosmolojosh
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How do gravitons interact with the warping of spacetime in string theory? I know gravitons have not been proved to exist. Plus how is it effected by SUSY and what is supergravity?thanks ?
 
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  • #2
what do you expect - three questions and three short answers?

What dou you mean by "warping of spacetime in string theory"? The (oversimplified) perturbative treatment of string theory says that gravitons are nothing else but a special (spin-2) oscillation of the fundamental string. In the perturbative picture gravitons do not interact with spacetime (spacetime influences gravitons, but there is no back reaction of gravitons to spacetime, just like weak gravitational waves on flat Minkowski spacetime).

SUSY is an approach to unify spacetime symmetry and "internal" symmetries like isospin or gauge symmetries. This unification is known to be impossible w/o an enlargement of our concept of symmetries. This what SUSY does: it introduces a new symmetry which has conserved charges that behave like fermionic objects and that interchanges bosons with fermions, i.e. acts as a kind of "ladder operator" between particles with different.

(global) SUSY is intertwined nontrivially with Poincare invariance. That means that one can construct spacetime transformations from SUSY. If one tries to construct a local SUSY ("local" in the sense of ordinary gauge theories) than one is forced to introduce a spin-2 degree of freedom, the graviton field; loosly speaking the graviton is the gauge boson of the Poincare symmetry; in addition due to SUSY one must introduce a fermionic partner, the spin 3/2 gravitino field.
 

Related to String Theory: Gravitons, Warping Spacetime & Supergravity

1. What is string theory?

String theory is a theoretical framework in physics that attempts to reconcile the differences between quantum mechanics and general relativity. It proposes that the fundamental building blocks of the universe are not particles, but tiny, vibrating strings that make up all matter and energy.

2. How does string theory explain gravitons?

Gravitons are hypothetical particles that mediate the force of gravity. In string theory, they are described as closed strings that interact with other particles through their vibrations. These vibrations determine the strength and direction of the gravitational force between objects.

3. What is the concept of warping spacetime in string theory?

In general relativity, gravity is described as the curvature of spacetime caused by massive objects. In string theory, this concept is extended to the idea that spacetime itself can be warped and distorted by the vibrations of strings, leading to the force of gravity.

4. How does supergravity fit into string theory?

Supergravity is a theory that combines the principles of general relativity with supersymmetry, a theoretical concept that proposes the existence of particles with properties that are related to each other. In string theory, supergravity is used as a tool to describe the behavior of strings in a curved spacetime.

5. What are the implications of string theory for our understanding of the universe?

String theory is still a highly speculative and controversial theory, but if proven to be true, it would greatly expand our understanding of the universe. It could potentially explain the fundamental nature of matter and energy, the origin of the universe, and the unification of all the forces of nature.

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