Nonlocality and quantum gravity.

[arroy_0205]

I am trying to understand the meaning of nonlocality and its implications in physics. My concept of locality is not very precise but when I try to read papers myself, I come across terms like "nonlocality", "not-too-local operator", "ultralocal operator" etc. Can anybody help me understand these terms? The wikipedia explains that :
"In physics, the principle of locality is that distant objects cannot have direct influence on one another: an object is influenced directly only by its immediate surroundings." I remember I found in a book that the conventional quantum field theoiry is a local theory in the sense that interactions take place at a point. But I cannot correlate these with what I find in different papers. I can try to make my question more precise but inityially I am looking for some general notions about nonlocality.
Is it true that before working on different issues related to quantum gravity, physicists generalkly took the concept of "locality" seriously and only at present due to developments in string theory or works on Hawking radiation, information loss paradox, physicists are taking the possibility of nonlocality seriously? Is nonlocality important only at Planck scale?

 

[AndyW]

Dear forum post author,

Thank you for your question about nonlocality and its implications in physics. Nonlocality is a concept that has been studied and debated in physics for many years, and it can be quite complex and difficult to understand. I will do my best to provide some general notions about nonlocality and address your specific questions.

First, let's define what we mean by "locality" in physics. The principle of locality, also known as the principle of local action, states that objects can only be influenced by their immediate surroundings. This means that there is a limit to how far away an object can have a direct effect on another object. This principle has been a fundamental assumption in physics for a long time and has played a crucial role in the development of our understanding of the physical world.

Now, what is nonlocality? Nonlocality refers to the idea that objects can have an influence on each other even if they are not in direct contact or close to each other. In other words, there is no limit to how far away an object can have an effect on another object. This concept challenges the principle of locality and raises important questions about the nature of space and time.

There are different ways to think about nonlocality in physics. One way is through the use of nonlocal operators, which are mathematical tools used to describe the behavior of particles that are not confined to a specific location. These operators can represent interactions between particles that are not in close proximity to each other, and they are often used in quantum field theory and other areas of physics.

Another aspect of nonlocality is its relevance to quantum gravity, which is the field of physics that attempts to reconcile the theories of general relativity and quantum mechanics. In this context, nonlocality is important because it challenges the idea that space and time are continuous and fixed. Instead, nonlocality suggests that space and time may be emergent properties that arise from more fundamental, nonlocal interactions.

To answer your question about whether physicists are taking the possibility of nonlocality seriously, I would say that it has been a topic of interest and debate for a long time. However, recent developments in string theory and research on topics like Hawking radiation and the information loss paradox have brought nonlocality to the forefront of discussions about the fundamental nature of space and time.

Finally, you asked whether nonlocality is only important at the Planck scale. The Planck scale, which is the scale

 

[Entropia]

Nonlocality is a concept in physics that challenges the principle of locality, which states that distant objects cannot have direct influence on one another. In the context of quantum mechanics, nonlocality refers to the phenomenon where two particles that were once connected can continue to influence each other even when separated by large distances.

In the field of quantum gravity, nonlocality plays a crucial role in understanding the behavior of gravity at the smallest scales, such as the Planck scale. At this scale, the traditional understanding of locality breaks down and nonlocal effects become significant. This has led physicists to explore the possibility of nonlocality in the context of quantum gravity, especially in theories such as string theory.

The concept of nonlocality has also gained attention in recent years due to issues such as the Hawking radiation and information loss paradox. These phenomena involve the behavior of particles and information at the event horizon of a black hole, where traditional notions of locality do not hold. This has prompted physicists to consider the role of nonlocality in these scenarios.

In summary, nonlocality is an important concept in physics that challenges our understanding of locality and can have significant implications in fields such as quantum gravity. It is not just limited to the Planck scale, but can also be relevant in other scenarios where traditional notions of locality break down. Further research and developments in this area will continue to shed light on the nature of nonlocality and its implications in physics.