Difference Between String Theory and Loop Quantum Gravity

Among the attempts to unify quantum theory and gravity, string theory has attracted the most attention. Its premise is simple: Everything is made of tiny strings. ... Loop quantum gravity, by contrast, is concerned less with the matter that inhabits space-time than with the quantum properties of space-time itself.

1. What is string theory and quantum gravity?
2. What is the loop quantum gravity theory?
3. Is loop quantum gravity wrong?
4. What is quantum string theory?
5. How many dimensions are proven?
6. How many dimensions do we live in?
7. How many dimensions are there?
8. What's the M-theory?
9. Can gravity be quantized?
10. Why does string theory require 11 dimensions?
11. Is the universe a loop?
12. Who invented loop quantum gravity?

What is string theory and quantum gravity?

String theory is a framework to build models of quantum gravity. ... This correspondence relates quantum gravity in a spacetime that asymptotes to anti-de Sitter space with an ordinary quantum field theory that lives in one lower dimension, and has a symmetry under angle-preserving (conformal) transformations.

What is the loop quantum gravity theory?

Loop quantum gravity (LQG) is a theory of quantum gravity, which aims to merge quantum mechanics and general relativity, incorporating matter of the Standard Model into the framework established for the pure quantum gravity case. As a candidate for quantum gravity, LQG competes with string theory.

Is loop quantum gravity wrong?

The biggest flaw in loop quantum gravity is that it has yet to successfully show that you can take a quantized space and extract a smooth space-time out of it.

What is quantum string theory?

String theory describes how strings propagate through space and interact with each other. ... In string theory, one of the vibrational states of the string gives rise to the graviton, a quantum mechanical particle that carries gravitational force. Thus string theory is a theory of quantum gravity.

How many dimensions are proven?

In fact, the theoretical framework of Superstring Theory posits that the universe exists in ten different dimensions. These different aspects are what govern the universe, the fundamental forces of nature, and all the elementary particles contained within.

How many dimensions do we live in?

In everyday life, we inhabit a space of three dimensions – a vast 'cupboard' with height, width and depth, well known for centuries. Less obviously, we can consider time as an additional, fourth dimension, as Einstein famously revealed.

How many dimensions are there?

The world as we know it has three dimensions of space—length, width and depth—and one dimension of time. But there's the mind-bending possibility that many more dimensions exist out there. According to string theory, one of the leading physics model of the last half century, the universe operates with 10 dimensions.

What's the M-theory?

M-theory is a theory in physics that unifies all consistent versions of superstring theory. ... According to Witten, M should stand for "magic", "mystery" or "membrane" according to taste, and the true meaning of the title should be decided when a more fundamental formulation of the theory is known.

Can gravity be quantized?

In 2+1 dimensions, however, gravity is a topological field theory, and it has been successfully quantized in several different ways, including spin networks.

Why does string theory require 11 dimensions?

Why does string theory require 10 or 11 spacetime dimensions? The answer at a technical level is well-known, but it's hard to bring it down to earth. ... Because there is no preferred direction in empty space, rotations in three dimensions are symmetric. Suppose the universe had a few extra dimensions.

Is the universe a loop?

Instead of being flat like a bedsheet, our universe may be curved, like a massive, inflated balloon, according to a new study. ... So it's been largely rejected in favor of a “flat universe” that extends without boundary in every direction and doesn't loop around on itself.

Who invented loop quantum gravity?

Martin Bojowald: physicist who developed the application of loop quantum gravity to cosmology. Steve Carlip: expert on 3-dimensional quantum gravity.