Discussion Overview
The discussion revolves around the concept of luminosity distance in cosmology, particularly at redshift z=0. Participants are examining the implications of equations from a specific paper regarding the relationship between luminosity distance and comoving distance, as well as the potential for mathematical errors arising from these definitions.
Discussion Character
- Technical explanation
- Debate/contested
- Mathematical reasoning
Main Points Raised
- One participant notes a divide by zero error in a formula from a paper when applying the luminosity distance at z=0, questioning the treatment of comoving distance in this context.
- Another participant asserts that at z=0, the comoving distance is not zero but equal to the luminosity distance, relating it to the inverse square law.
- A similar viewpoint is reiterated, emphasizing that the only scenario where comoving distance is zero is when one is at the source.
- Concerns are raised about the paper's assertion that luminosity distance is purely a function of redshift, prompting questions about how to relate it to Hogg's equations, which involve luminosity and flux.
- One participant expresses difficulty in following the paper and suggests that the relation d_L=(1+z)d_c is what the authors intended.
- Another participant notes the lack of discussion regarding the influence of matter/radiation density evolution at different redshifts, referencing Hogg's work on cosmological distance measures.
Areas of Agreement / Disagreement
Participants express differing interpretations of the equations and concepts related to luminosity and comoving distances, indicating that multiple competing views remain without a consensus on the correct interpretation.
Contextual Notes
There are unresolved assumptions regarding the definitions of luminosity and comoving distances, as well as the implications of redshift on these measures. The discussion also highlights potential gaps in the paper's treatment of density evolution.