L = 0 in the equation for effective potential energy?

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Discussion Overview

The discussion revolves around the implications of setting angular momentum (L) to zero in the context of effective potential energy equations, with a focus on both general relativity (GR) and Newtonian physics. Participants explore the consequences of zero angular momentum, particularly in relation to radial infall.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • Some participants propose that setting L to zero indicates zero angular momentum, leading to a scenario of radial infall.
  • Others suggest that the context of the equation is important, noting that the discussion may pertain to either general relativity or Newtonian physics.
  • A later reply emphasizes the importance of understanding the Kepler problem in Newtonian physics as a precursor to grasping the general-relativistic treatment.

Areas of Agreement / Disagreement

Participants generally agree that L can be set to zero, but there is no consensus on the specific implications or the context of the equation being referenced.

Contextual Notes

There is a lack of clarity regarding which specific equation is being discussed, and the implications of setting L to zero may depend on the theoretical framework (GR vs. Newtonian) being considered.

sqljunkey
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Hi,

What would happen if I set L in this equation to zero? I can have an L that is zero right?
 
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Sure. That would be zero angular momentum. What do you expect to happen?

(EDIT: Which equation, exactly? There are many on that page.)
 
L can be zero. From context, L is just the angular momentum, and L=0 corresponds to a radial infall. This is the GR forum, so I'd guess you are most likely interested in the GR case, though it's possible you are interested in the Newtonian case as well.
 
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Start with a thorough study of the Kepler problem in Newtonian physics. There (almost) everything can be solved in analytical form with standard elementary functions. After that it's easier to understand the general-relativsitic treatment (test particle in a Schwarzschild spacetime).
 

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