Description
Calculate one scalar reduced-shear component from supplied shear and convergence.
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.
Calculate one scalar reduced-shear component from supplied shear and convergence.
When to use this tool
Use Weak Lensing Reduced Shear Scalar when you already have shearComponent, convergence and need to calculate one scalar reduced-shear component from supplied shear and convergence.
How to use the tool and how it works
- Enter shearComponent, convergence. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read reducedShear. Use the output convention below.
Require convergence!=1; return shearComponent/(1-convergence).1
Reduced shear divides shear by one minus convergence. This scalar operation alone does not reconstruct a lens or establish the approximation appropriate to an observed image.2
| Input field | Meaning and units | Accepted input |
|---|---|---|
| shearComponent | Shear Component | Required. Finite number. |
| convergence | Dimensionless finite κ other than one; values above one are accepted without establishing a weak-lensing regime. | Required. Finite number. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| reducedShear | shearComponent/(1-convergence); signed scalar, not full complex shear. | Required. Finite number. |
{
"input": {
"shearComponent": 0.1,
"convergence": 0.5
},
"output": {
"reducedShear": 0.2
}
}Limitations and assumptions
- Signed and supercritical convergence values are accepted. No lens model, full two-component shear, magnification, weak-regime validity or observation is inferred; near-one inputs amplify errors.
- 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
-
Calculation and input contract: cosmology/weak-lensing-reduced-shear-scalar — tool.io
-
Weak gravitational lensing (2016) — Matthias Bartelmann and Matteo Maturi
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