Quantcast
  • Register
PhysicsOverflow is a next-generation academic platform for physicists and astronomers, including a community peer review system and a postgraduate-level discussion forum analogous to MathOverflow.

Welcome to PhysicsOverflow! PhysicsOverflow is an open platform for community peer review and graduate-level Physics discussion.

Please help promote PhysicsOverflow ads elsewhere if you like it.

News

New printer friendly PO pages!

Migration to Bielefeld University was successful!

Please vote for this year's PhysicsOverflow ads!

Please do help out in categorising submissions. Submit a paper to PhysicsOverflow!

... see more

Tools for paper authors

Submit paper
Claim Paper Authorship

Tools for SE users

Search User
Reclaim SE Account
Request Account Merger
Nativise imported posts
Claim post (deleted users)
Import SE post

Users whose questions have been imported from Physics Stack Exchange, Theoretical Physics Stack Exchange, or any other Stack Exchange site are kindly requested to reclaim their account and not to register as a new user.

Public \(\beta\) tools

Report a bug with a feature
Request a new functionality
404 page design
Send feedback

Attributions

(propose a free ad)

Site Statistics

145 submissions , 122 unreviewed
3,930 questions , 1,398 unanswered
4,853 answers , 20,624 comments
1,470 users with positive rep
501 active unimported users
More ...

Existence of objects arising in physics

+ 0 like - 0 dislike
36 views

If you look at the configuration space of a robot arm, its a manifold, does this manifold exist in the same sense as strings in string theory? Or do the strings in string theory exist in another sense? What objects actually exist? What are the different levels physical objects can exist? Spacetime and particles, is that all that exist? If you accept holographic principle everything can exist on a boundary? So which description is right? Or are both right, that this is a duality that violates our intuition like the wave particle duality?

asked May 13 in Chat by kalle44 (0 points) [ no revision ]
recategorized May 13 by Dilaton

1 Answer

+ 2 like - 0 dislike

Existence of the manifolds is existence in the mathematical (platonic) sense. Existence of a physical object usually means (on the level of theoretical physics) that the object can be modeled as a mathematical object having a (classical or quantum) state. A property of an object exists (on the same level) if it can be expressed in terms of expectation values of observables defined on the state space and determined by the state. For example, an electron has mass, charge, position, and spin in any direction, although the latter two have sharp values only under special circumstances. 

A string in string theory has a state, and a robot arm has one (in the cotangent space of the configuration manifold) , so they are physical objects (on the level of theoretical physics). But the manifold of robot arm configurations has no state hence it cannot be said to be physically existent, though it is used to describe physical objects, namely robot arms. 

Of course, existence in nature is a much more restricted matter, as in this case the model is required to match Nature suffciiently well. 

answered May 14 by Arnold Neumaier (12,385 points) [ revision history ]
edited May 16 by Arnold Neumaier

Your answer

Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead.
To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL.
Please consult the FAQ for as to how to format your post.
This is the answer box; if you want to write a comment instead, please use the 'add comment' button.
Live preview (may slow down editor)   Preview
Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
Anti-spam verification:
If you are a human please identify the position of the character covered by the symbol $\varnothing$ in the following word:
p$\varnothing$ysicsOverflow
Then drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds).
To avoid this verification in future, please log in or register.




user contributions licensed under cc by-sa 3.0 with attribution required

Your rights
...