What Are the Top Beginner Resources for Learning Loop Quantum Gravity Online?

In summary, Sundance Bilson-Thompson's "Introducing LQG" is a good introductory resource for Loop Quantum Gravity.
  • #1
craigi
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What are the best online introductory resources for Loop Quantum Gravity?

I've never felt more out of my depth than when listening to Rovelli speak on the subject.
 
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  • #2
LQG is a subject that is built off of general relativity and quantum field theory, so you should understand that a good introduction would still assume 2 years of graduate coursework...

Regardless, I found the following to be a pretty good intro: http://arxiv.org/abs/1102.3660

I also read Rovelli's book on the subject, which is a bit out of date compared to his Zakopane lectures but it goes into more detail with the derivations.

There is also this review: http://arxiv.org/abs/1303.4636
 
  • #3
craigi said:
What are the best online introductory resources for Loop Quantum Gravity?

There was a thread about LQG introductory resources started about one year ago
https://www.physicsforums.com/showthread.php?t=676720

This came up in that thread. It is recent, has 85 pages and 20 figures, is online
http://arxiv.org/abs/1402.3586
Sundance Bilson-Thompson, Deepak Vaid
School of Chemistry and Physics, University of Adelaide, Adelaide SA, Australia
Department of Physics, National Institute of Technology Karnataka (NITK), Surathkal, Karnataka, India

Abstract: We present a pedagogical introduction to the notions underlying the connec- tion formulation of General Relativity - Loop Quantum Gravity (LQG) - with an emphasis on the physical aspects of the framework. We begin by reviewing General Relativity and Quantum Field Theory, to emphasise the similarities between them which establish a foun- dation upon which to build a theory of quantum gravity. We then explain, in a concise and clear manner, the steps leading from the Einstein-Hilbert action for gravity to the construction of the quantum states of geometry, known as spin-networks, which provide the basis for the kinematical Hilbert space of quantum general relativity. Along the way we introduce the various associated concepts of tetrads, spin-connection and holonomies which are a pre-requisite for understanding the LQG formalism. Having provided a minimal introduction to the LQG framework, we discuss its applications to the problems of black hole entropy and of quantum cosmology. A list of the most common criticisms of LQG is presented, which are then tackled one by one in order to convince the reader of the physical viability of the theory.
An extensive set of appendices provide accessible introductions to several key notions such as the Peter-Weyl theorem, duality of differential forms and Regge calculus, among others. The presentation is aimed at graduate students and researchers who have some familiarity with the tools of quantum mechanics and field theory and/or General Relativity, but are intimidated by the seeming technical prowess required to browse through the existing LQG literature. Our hope is to make the formalism appear a little less bewildering to the un-initiated and to help lower the barrier for entry into the field.
sundance.bilson-thompson@adelaide.edu.au
deepak@nitk.edu.in

There are other introductory resources. I can't list them, but you could try this one and see if it is right for you. If not, say how this one does not fit your needs and ask again. We can try to suggest something else that is closer to what you want. So maybe by successive approximation we will get a good fit
 
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1. What is LQG and how is it different from other theories of quantum gravity?

LQG, or Loop Quantum Gravity, is a theory that attempts to reconcile the principles of general relativity and quantum mechanics in order to describe the fundamental nature of the universe. It differs from other theories of quantum gravity, such as string theory, in its approach to quantizing space and time. LQG proposes that space and time are made up of discrete, indivisible units, whereas string theory suggests that they are continuous and infinitely divisible.

2. What is the main goal of LQG research and what are its potential implications?

The main goal of LQG research is to develop a consistent, mathematically rigorous theory of quantum gravity that can explain the fundamental nature of the universe. If successful, LQG could provide a unified framework for understanding the laws of physics at both the macroscopic and microscopic levels. This could have implications for our understanding of the Big Bang, black holes, and other fundamental phenomena in the universe.

3. How is LQG tested and what are some current challenges facing its development?

LQG is primarily tested through mathematical calculations and simulations, as it is currently not possible to directly observe or experiment with the extremely small scales at which quantum gravity operates. Some current challenges facing the development of LQG include the difficulty of incorporating the principles of quantum mechanics into a theory of gravity, as well as the lack of experimental evidence to support or refute its predictions.

4. What are some key concepts and principles in LQG theory?

Some key concepts and principles in LQG theory include the discrete quantization of space and time, the use of mathematical tools such as spin networks and spin foam to represent the structure of space-time, and the concept of a "quantum geometry" that describes the fabric of the universe at a fundamental level. The theory also incorporates the principles of general relativity, such as the equivalence principle and the concept of space-time curvature.

5. What are some potential applications of LQG in other fields of science?

LQG has potential applications in a variety of fields, including cosmology, astrophysics, and high-energy physics. It may help to further our understanding of the early universe, the behavior of matter in extreme conditions such as black holes, and the fundamental nature of space and time. Additionally, LQG could have implications for the development of new technologies, such as quantum computers, that rely on our understanding of quantum mechanics and gravity.

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