String theory classical limit?

[cragwolf]

String theory "classical" limit?

I know nothing about string theory, I'm still trying to deal with the more basic early 20th century stuff. But a question popped into my head which I hope someone can answer or point me to an answer.

In general relativity you can recover Newtonian gravitational physics by applying the field equations to a slowly varying, weak gravitational field. In Maxwell's electrodynamics you can recover Coulomb's electrostatics law (I forget exactly how). In special relativity you can recover Newtonian mechanics in the limit as velocities go to zero.

Can you do the same with string theory? Can you recover general relativity from string theory in some limit? What about quantum mechanics and quantum electrodynamics?

 

[selfAdjoint]

The string theorists say you can, but many relativitists disagree. String physics produces a graviton, and the properties of this graviton are such that, if matter particles exchange them, the resulting physics is like Einstein's general relativity, with som extra stuff that goes away at low energies.

The trouble is that in most of the string models, all of this happens within a flat Minkowski spacetime. So you lose one of the cherished parts of general relativity, once called general covariance, now realized as diffeomorphism invariance. Space is decoupled from physics, which is business as usual in quantum physics, but a big loss for GR physics.

 

[R0man]

The "classical" limit in string theory refers to the scenario where the fundamental strings are assumed to be infinitely long, and their vibrations are slow compared to the speed of light. In this limit, the behavior of the strings can be described using classical equations of motion, similar to how classical mechanics can describe the behavior of particles in the limit of low velocities compared to the speed of light.

In this limit, string theory is expected to reproduce the predictions of general relativity and quantum field theory. However, it is important to note that string theory goes beyond these theories and incorporates gravity into a unified framework with the other fundamental forces of nature. So while the classical limit may recover some aspects of these theories, it also introduces new features and phenomena that are not present in them.

Furthermore, the classical limit in string theory is just one aspect of the theory and does not fully capture its complexity and richness. It is still an active area of research and there is ongoing work to understand the full implications and predictions of string theory. So while the classical limit may provide some insights, it is not the complete picture of string theory.