Retrieving the loops on spinfoams

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In summary, Rovelli discusses a way to obtain the loop states from a simple spin network. He also mentions that the orientation of the loops is unknown.
  • #1
Heidi
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I am looking for a paper i read several yeais ago.
is was on a graphical way to see all the closed loops associated to an oriented spinfoam. there was a set of lines on each edge.
do you see what i mean?
thanks
 
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  • #3
It was more simple that this paper. more like a trick than a theory...
with an author like smolin or rovelli (maybe).
 
  • #4
You really should try to find the paper and post the link. Others might be interested.
 
  • #5
what i remember is that in finite connected spinfoam if you are on an edge and follow a random outgoing edge when you meet a node you will follow a closed path ending on the startind edge. this is a loop that you can draw near the edges. other choices would give over loopq and over drawings.
so you get for each edge parrallel different loop lines.
Draw the Mercedes cirle with 3 segments , choose orientations for the edges (at less one ingoing and one outgoing one each nodes) and see the loops ...
 
  • #6
I found this interesting paper
SPIN NETWORKS AND THE BRACKET POLYNOMIAL
https://homepages.math.uic.edu/~kauffman/spinnet.pdf
it gives the identities of the binor calcus based on the properties of the epsilon tensor. this epsilon tensor appears in the LQG intertwiners.
 
  • #7
Louis H. Kauffman wrote a book ”Knots and Physics” which might be of interest as it provides a more in depth introduction to the mathematic. I go through phases on things like this. Never quite clear on how much of it is really physics.
 
  • #8
Hi Paul,
there is something that bothers me.
Links in LQG have orientations so a node can have only ingoing links.
But consider the loops in the recoupling theory. we have strands associated with links
ie if a link has a j spin we find 2j lines in the strand. if they correspond to loops they should
have an orientation. How to manage these orientations? what if such a loop goes thru the node with only ingoing links?
 
  • #9
Sorry, I haven’t looked at LQG closely enough to even guess. Several years ago I did attempt a reading of a paper that approached QED from a loop approach similar to LQG. My hope was to gain insight by looking at how a theory I partially understand is handled.

BTW I took another swing at “Knots and Physics”. It’s quite readable.
 
  • #10
  • #11
Haven’t looked at it. I’m probably ripe for another LQG attempt. Thanks for the link.
 
  • #12
When i opened this thread , i had in mind what Rovelli wrote in in the 6.3.2 paragraph.(details on the spin networks)
see how from a simple spin network he obtains the corresponding loop states
the remainig problem for me is the orientation of the loops.
 

Related to Retrieving the loops on spinfoams

1. What is the purpose of retrieving the loops on spinfoams?

The purpose of retrieving the loops on spinfoams is to understand the structure and dynamics of spacetime at a quantum level. Spinfoams are a mathematical model used in loop quantum gravity, a theory that aims to reconcile general relativity and quantum mechanics. By retrieving the loops on spinfoams, scientists hope to gain insights into the fundamental nature of the universe.

2. How are loops retrieved on spinfoams?

Loops are retrieved on spinfoams through a process called spin-network refinement. This involves breaking down the spinfoam into smaller and smaller pieces, until the individual loops can be analyzed and studied. This process is essential for understanding the properties and behavior of the loops on spinfoams.

3. What are the challenges of retrieving loops on spinfoams?

One of the main challenges of retrieving loops on spinfoams is the complex mathematical calculations involved. Spinfoams are described using abstract algebra and differential geometry, making it a difficult task for scientists to analyze and manipulate them. Additionally, the nature of quantum gravity itself poses many theoretical and conceptual challenges in understanding and retrieving the loops on spinfoams.

4. How do the retrieved loops on spinfoams relate to real-world observations?

The relationship between the retrieved loops on spinfoams and real-world observations is still an area of active research. However, it is believed that the loops on spinfoams could provide a more accurate and complete understanding of spacetime at a quantum level, which could potentially lead to new predictions and explanations for phenomena observed in the universe.

5. What are the potential applications of retrieving loops on spinfoams?

The potential applications of retrieving loops on spinfoams are vast and far-reaching. Understanding the structure and dynamics of spacetime at a quantum level could have implications for various fields, such as cosmology, particle physics, and quantum computing. It could also potentially lead to the development of new technologies and advancements in our understanding of the universe.

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