Dynamical Spacetime: Time or Space Dependent?

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Discussion Overview

The discussion revolves around the concept of dynamical spacetime, specifically questioning whether dynamical characteristics arise from time dependence, spatial dependence, or both. Participants explore implications in the context of AdS/CFT correspondence and the nature of observations related to length and time.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions the definition of dynamical spacetime, asking if it is characterized by time dependence or spatial dependence.
  • Another participant asserts that dynamical characteristics are associated with time.
  • A subsequent reply challenges the assertion by referencing AdS geometry, noting its spatial dependence and questioning the relationship between fixed boundary theories and dynamical bulk gravity theories in AdS/CFT.
  • Another participant offers a perspective on the interdependence of length and time in direct observations, suggesting that length cannot be fully understood without considering time, and vice versa.
  • This participant also reflects on the traditional association of time with dynamical systems, expressing uncertainty about its applicability in the context of AdS/CFT theory.

Areas of Agreement / Disagreement

Participants express differing views on whether dynamical spacetime is defined by time, space, or both, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

Participants acknowledge the complexity of defining dynamical spacetime and the potential implications of their observations, but do not resolve the assumptions or definitions involved.

kau
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when do you call a spacetime dynamical...when metric is time dependent or it depends on space ??...
 
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bapowell said:
Time.
Ok...then AdS geometry has spatial dependence then why it is written that fixed boundary theory has a correspondence to bulk gravity theory which is dynamical..(in the context of AdS/CFT)...
 
One of the reasons the concept of spacetime eventually became a natural concept to me is due to some conclusions one can make regarding any direct observation of length and time.

Length only exists (observationally) in conjunction with time, that may not be intuitive but what differentiates lengths like a meter from a kilometer is time. We tend to think of those lengths as static but if time is 0 both lengths are infinite. Time > 0 is required to observe and differentiate length; however the same holds true for direct observations of time, such observations include a length > 0 too. Please remember I am referring to direct observations above.

Traditionally time is associated with dynamical systems whereas space is not. I’d only be guessing if that holds true in the context of AdS/CTF theory. Perhaps what I brought up above might give you a little better insight into it.
 

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