Description
Label a simulation snapshot's supplied scale factor and corresponding redshift.
Cosmological quantities depend on scale factor, redshift, distance definition and the dimensionless Hubble parameter h. Proper and comoving distances differ at a specified epoch, and h-scaled units differ from the dimensional Hubble constant. A scalar rescaling or model contribution preserves supplied conventions without fitting a cosmology or inferring an observed distance.
Label a simulation snapshot's supplied scale factor and corresponding redshift.
When to use this tool
Use Cosmological Simulation Snapshot Scale Tag when you already have snapshotId, scaleFactor and need to label a simulation snapshot's supplied scale factor and corresponding redshift.
How to use the tool and how it works
- Enter snapshotId, scaleFactor. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read tag, redshift. Use the output convention below.
Require snapshotId nonempty and scaleFactor>0; return its label and z=1/a-1.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| snapshotId | Snapshot Id | Required. Text; minimum UTF-16 length 1; maximum UTF-16 length 8192. |
| scaleFactor | Scale Factor | Required. Finite number; strictly above 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| tag | Tag | Required. Text; maximum UTF-16 length 8192. |
| redshift | 1/scaleFactor-1 under a present-day scale-factor normalization of one. | Required. Finite number. |
{
"input": {
"snapshotId": "S17",
"scaleFactor": 0.5
},
"output": {
"tag": "S17 [a=0.5]",
"redshift": 1
}
}Limitations and assumptions
- Assumes a=1 at the chosen reference present. Future scale factors yield negative z; no simulation, epoch or expansion history is verified.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use the complete cosmological model and its parameter, epoch and unit definitions for a physical inference. Review redshift, distance, lensing and spectrum conventions before combining these local terms; they do not perform line-of-sight integration, parameter estimation or uncertainty analysis.
References
Similar or alternative tools
- Cosmological Time Dilation Interval Pair
Apply a supplied cosmological redshift time-dilation factor.
- Cosmology Distance Physical Comoving Label
Crosswalk supplied same-epoch physical and comoving lengths using a scale factor.