Can configuration space be observer independent?

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Discussion Overview

The discussion revolves around the concept of configuration space and whether it can be formulated in an observer-independent manner. Participants explore the implications of observer dependence in the context of Lagrangian mechanics and the representation of physical systems in spacetime.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant suggests that while spacetime can be formulated in an observer-independent way, configuration space may inherently depend on the observer and their chosen coordinates.
  • Another participant questions the premise that configuration space could be observer dependent, seeking clarification on the reasoning behind this idea.
  • A third participant provides an example of a pendulum's configuration space, suggesting that it remains the same regardless of the observer, thus questioning the necessity of observer dependence.
  • Some participants express confusion about the lack of coordinate-independent formulations of configuration space, indicating a desire for more clarity on this topic.
  • A later reply reiterates the definition of a Lagrangian system, emphasizing the role of the configuration space as a smooth manifold, and raises the question of how to define this space in an observer-independent way based on the properties of spacetime and particle interactions.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on whether configuration space can be observer independent. Multiple competing views remain, with some questioning the observer dependence while others seek to clarify the definitions involved.

Contextual Notes

There are unresolved assumptions regarding the definitions of configuration space and the implications of observer independence. The discussion highlights a potential gap in existing literature on the topic.

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We can formulate the spacetime in an observer/coordinate independent way, i.e. a particle becomes a worldline in the 4d space. Then relative to each observer, the worldline can be casted to a function in R^3. However, I haven't found any reference on formulating configuration space in a coordinate independent way. It seems that the configuration space is formed in a way with a particular observer and some particular coordinates for the state of the system. Just want to ask if there's such a concept as observer independent configuration space?
 
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I don’t understand. Why would configuration space be observer dependent?
 
An example could clarify the question I guess.
Say, the configuration space of the pendulum is ##S^1##. Which observer does see anything else?
 
Dale said:
I don’t understand. Why would configuration space be observer dependent?
I just don't usually see coordinate independent formulation of the configuration space.
 
By definition a Lagrangian system is a pair (L,M), where M is a smooth manifold called the configuration space and ##L: TM\to \mathbb{R}## is a smooth function
ok?
 
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wrobel said:
By definition a Lagrangian system is a pair (L,M), where M is a smooth manifold called the configuration space and ##L: TM\to \mathbb{R}## is a smooth function
ok?
Sorry, the question may sound a bit weird. I will try to give a more detailed explanation on what structure I have in mind before rasing the question.

So first, we have a 4d spacetime, there are n worldlines in the spacetime representing n particles forming a system with certain interation. There might be constraints at each spatial slice, such as the distance between two particles maintain the same.

These definitions are observer independent that fully describe the system, so if the configuration space is also observer independent, we should be able to derive the configuration space structure purely from the above. My question is how to craft such a definition?
 

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