Future null infinity confusion

Click For Summary
SUMMARY

The discussion centers on the distinction between event horizons and Killing horizons, particularly in the context of Schwarzschild spacetime. It is established that the event horizon is the last Killing horizon that escapes to future null infinity, which is defined as the set of all events in spacetime at the end of a null geodesic as the affine parameter approaches infinity. Key points include that the photon sphere does not extend to future null infinity, as it is not located on the conformal boundaries of the conformally completed spacetime. The conversation also highlights the importance of understanding conformal compactification and its limitations in non-asymptotically flat spacetimes.

PREREQUISITES
  • Understanding of event horizons and Killing horizons in general relativity.
  • Familiarity with Schwarzschild spacetime and its properties.
  • Knowledge of null geodesics and their behavior in spacetime.
  • Basic comprehension of Penrose diagrams and conformal compactification.
NEXT STEPS
  • Study the definitions and properties of event horizons and Killing horizons in detail.
  • Explore the concept of conformal compactification in asymptotically flat spacetimes.
  • Investigate the implications of null geodesics in Schwarzschild and Rindler coordinates.
  • Read Hawking & Ellis and Wald for comprehensive insights into the behavior of geodesics and horizons.
USEFUL FOR

Researchers, physicists, and students in the field of general relativity, particularly those interested in black hole physics and the geometric structure of spacetime.

  • #31
Ok, thanks Peter. I am a follower of the frozen star heresy, and thought you might be coming out of the closet!
 

Similar threads

Undergrad What are the many null-infinities in Minkowskian space?
  • · Replies 4 ·
Replies
4
Views
1K
Undergrad Confusion about Cauchy surfaces
  • · Replies 8 ·
Replies
8
Views
1K
Graduate Connectedness of Boundary Points in Schwarzschild Penrose Chart
  • · Replies 7 ·
Replies
7
Views
2K
Undergrad Physical meaning of null spacetime interval
  • · Replies 35 ·
2
Replies
35
Views
6K
High School Detection of red-shifted photons near an event horizon
  • · Replies 7 ·
Replies
7
Views
1K
High School Theories about light and time near a black hole
  • · Replies 20 ·
Replies
20
Views
2K
Undergrad Coordinate and proper time, null geodesic
  • · Replies 42 ·
2
Replies
42
Views
5K
Undergrad Does potential energy curve spacetime?
  • · Replies 28 ·
Replies
28
Views
2K
Undergrad Observing Black Holes in Finite Time
  • · Replies 10 ·
Replies
10
Views
2K
Undergrad Geodesic Maximality: Answers to Relativists' Questions
  • · Replies 2 ·
Replies
2
Views
1K