Here, I will outline spin networks, focusing on Loop Quantum Gravity and Carlo Rovelli’s writing on the fields of spacetime, then, examine Sean Carroll’s decoherence, explaining the interactions in quantum systems and classical properties in a fixed location in space, and finally, analyze limitations and benefits of the relational system.
In the relational system, Carlo Rovelli, Italian physicist and writer, discusses spin networks, graphs showing the quantum state of a gravitational field. These spin networks act like blocks of space in Loop Quantum Gravity (LQG). LQG is the idea that space is granular, but made from the blocks of quanta that are the spin networks.
Rovelli’s description of spin networks in LQG shows a perspective in which spacetime geometry is defined by relations, not points. Spin networks are defined by relationships and interactions, the emergence of spacetime and LQG and not isolated points.
To better understand spin network graphs and quantum gravity, we can look at another example of relationships and interactions. Sean Carroll’s discussion of decoherence explains that determinate values arise through the extensive interactions between a quantum system and its environment. Carroll emphasizes that this constant interaction with the environment selects a basis for the quantum system.
This process of decoherence suppresses quantum superpositions for macroscopic objects, making it look like they have definite, classical properties like a fixed location in space. Carroll expands, stating that an object’s apparent ‘existence’ is the interactions and events that microscopically occur. Without those events, that object would lose its mass, solidity and charge, even if that object is simply standing at a point in time and seemingly not interacting with any other objects.
Classical reality and the location in space was set and non-relational. In quantum theory, spacetime is defined by relational interaction. the concept of isolated objects is an approximation for specific relational contexts, centering on structure and how the object interacts with the surroundings in a relational matter.
The relationalist argument, based on Loop Quantum Gravity (LQG) and decoherence, is the cohesion and strength. It explains the challenge of quantum gravity by using relational explanations instead of absolute, non-interacting ideas of classical spacetime. This provides a theoretical reason to use relational systems. However, the relational system’s weakness is a lack of empirical truth, as the granular structure of spacetime explained by LQG is farther than human observations.
While the relational approach has a complexity of the isolated object, it explains the emergence of classical properties through interaction and decoherence. Relationality thus scientifically focuses from the isolated abstract spacetime point for the interactive field’s geometry.
I argue that relations are more important in accurately and scientifically understanding spacetime for a useful perspective than if centered on isolated objects. Spin networks define spacetime geometry through relationships and interactions, not isolated objects.
Decoherence describes the values in a quantum system emerging from interaction with the environment, discussing that spacetime is made from relational interactions rather than properties. Ultimately, relationality plays a significant part in all of spacetime, contrasting to isolated objects.
