How well do cosmological models explain the observed µ vs. z data?

In summary: This is data that was obtained from Type Ia supernovae and γ-ray bursts. The model needs to account for all three of these data sets in order to be consistent.Only out to . The graph shown for the model has data out to . A hypothesis has to account for all of the data, not just a subset that happens to match.The model based on the non-expanding universe does not seem to be able to account for the all three data sets.
  • #1
JimJCW
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The following figure shows observed distance modulus (µ) vs. redshift (z) data (references of data sources are available):

1632056753350.png


How well do cosmological models, such as ΛCDM and models based on non-expanding universe, explain these observed data?

For explanation of terms, please see,

 
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  • #2
JimJCW said:
(references of data sources are available)
On PF, please provide links to the references in the first post.
 
  • #3
anorlunda said:
On PF, please provide links to the references in the first post.
My supernova data are from,

Supernova Cosmology Project Union2.1
MLCS2k2 Full Sample

My γ-ray burst data are from,

Bradley E. Schaefer, 2007, The Astrophysical Journal, 660:16-46, 2007
Hao Wei, Journal of Cosmology and Astroparticle Physics, Issue 08, id. 020 (2010)
 
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  • #4
JimJCW said:
How well do cosmological models, such as ΛCDM and models based on non-expanding universe, explain these observed data?
Lambda-CDM fits quite well. See, for example, Figure 2 from this paper:

https://arxiv.org/pdf/1811.02590.pdf
 
  • #5
phyzguy said:
Lambda-CDM fits quite well. See, for example, Figure 2 from this paper:

https://arxiv.org/pdf/1811.02590.pdf

The authors of the paper are saying that according to their analysis, the µ vs. z relation of quasars at z<1.4 is qualitatively in agreement with that of supernovae and with the LCDM model. The data, however, suggest a dark energy density increasing with time. As we know, the dark energy density remains constant in the LCDM model.

The data points in our figure are from Type Ia supernovae and γ-ray bursts. It covers a greater range, up to z=8.1.
 
  • #6
JimJCW said:
The authors of the paper are saying that according to their analysis, the µ vs. z relation of quasars at z<1.4 is qualitatively in agreement with that of supernovae and with the LCDM model. The data, however, suggest a dark energy density increasing with time. As we know, the dark energy density remains constant in the LCDM model.

The data points in our figure are from Type Ia supernovae and γ-ray bursts. It covers a greater range, up to z=8.1.
The data points in the paper I linked go up to z=5, and still seem to fit quite well. Whether or not the observational data is consistent with Lanmbda-CDM , or a model with a varying dark energy is needed is an question which is still being studied. There is no compelling data that supports a dark energy varying with time, but there might be in the future. It is still an open question.
 
  • #7
phyzguy said:
The data points in the paper I linked go up to z=5, and still seem to fit quite well. Whether or not the observational data is consistent with Lambda-CDM , or a model with a varying dark energy is needed is an question which is still being studied. There is no compelling data that supports a dark energy varying with time, but there might be in the future. It is still an open question.

I think we can summarize this part of the discussion as follows,

The µ vs. z data points of quasars presented in the paper for 0.5<z<5.5 are not inconsistent with those plotted in our (supernova)+(gamma-ray burst) figure. They are additional data points.

There may be some open questions associated with the quasar data. For now, we might want to limit ourselves to the data plotted in our figure to discuss the question of how well some cosmological models do. Note that if there is a time-dependence of dark energy density with time, it probably would show up in the µ vs. z data we use also.

An interesting point to note about dark energy in the universe is that, according the LCDM model, its value continues to increase with space expansion (as indicated by the figure obtained from Jorrie’s calculator), but its density remains constant.

1632396419438.png
 
  • #8
JimJCW said:
How well do cosmological models, such as ΛCDM and models based on non-expanding universe, explain these observed data?

The following figure shows µ vs. z plot calculated with the ΛCDM model. It was obtained using Jorrie’s calculator and Planck data (2015), with the help of Eqs. (21) and (25) in Hogg’s article, Distance measures in cosmology. The calculation result suggests that the ΛCDM model can explain the observed µ vs. z data quite well.

1633183463796.png
 
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  • #9
JimJCW said:
How well do cosmological models, such as ΛCDM and models based on non-expanding universe, explain these observed data?

Fig. 2 of Sorrell’s 2009 paper, Misconceptions about the Hubble recession law, shows the result of a model based on non-expanding universe:

1633866081381.png
 
  • #10
JimJCW said:
Fig. 2 of Sorrell’s 2009 paper, Misconceptions about the Hubble recession law, shows the result of a model based on non-expanding universe:
Only out to . The graph shown for the model has data out to . A hypothesis has to account for all of the data, not just a subset that happens to match.

Also, the vs. data is not the only data that needs to be accounted for.
 
  • #11

FAQ: How well do cosmological models explain the observed µ vs. z data?

What is the µ vs. z data and why is it important in cosmology?

The µ vs. z data refers to the relationship between the observed brightness of a distant object (µ) and its redshift (z). This data is crucial in cosmology because it allows us to measure the expansion rate of the universe and understand its evolution over time.

How do cosmological models explain the observed µ vs. z data?

Cosmological models, such as the Lambda-CDM model, use a combination of theoretical equations and observational data to explain the relationship between µ and z. These models take into account factors such as the expansion of space, the density of matter and energy in the universe, and the effects of dark energy.

What evidence supports the accuracy of cosmological models in explaining the µ vs. z data?

There is a significant amount of evidence that supports the accuracy of cosmological models in explaining the µ vs. z data. This includes observations of the cosmic microwave background radiation, the large-scale structure of the universe, and the distribution of galaxies at different redshifts.

Are there any discrepancies between cosmological models and the observed µ vs. z data?

While cosmological models have been successful in explaining the majority of the observed µ vs. z data, there are still some discrepancies that have yet to be fully understood. For example, the measurements of the expansion rate of the universe from different methods have shown slight variations, known as the Hubble tension, which is still being investigated by scientists.

How do scientists continue to improve and refine cosmological models based on the µ vs. z data?

Scientists are constantly working to improve and refine cosmological models based on the µ vs. z data by incorporating new observations and data. This includes using more precise measurements of the expansion rate, studying the effects of dark energy and dark matter, and exploring alternative theories such as modified gravity. The goal is to create a more comprehensive and accurate model that can explain all aspects of the observed universe.

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