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Table B.1.
Key quantities and definitions used in this paper.
| Symbol | Name | Definition/formula | See Eq. # | Major properties |
|---|---|---|---|---|
| X(x) | Random field | Random variable | ||
| X(i)(x) | ith realization of X(x) | Single divergence map | ||
| σ2 | Variance of X | σ2 = 𝔼[X(x)2] | Eq. (10) | 𝔼[X(x)] = 0 |
| γ1 | Skewness of X |
 |
Eq. (9) | |
| γ(i) | Skewness of map i |
 |
Eq. (10) | ⟨X(i)(x)⟩ = 0 |
 |
Skewness of dataset |
 |
||
| B | Bispectrum (a) |  |
Eq. (7) |  |
| P | Power spectrum (a) |  |
Eq. (11) |  |
| b | Bicoherence (b) |
 |
Eq. (12) |
 significant if  |
| N | # of realizations of X | N = 365 × 11 = 4015 | ||
| NB | # of realiz. used in  |
 |
NB > N due to azim. average | |
| Ak, l | Coupling coefficient |
 |
Eq. (17) | |
| XNL | NL (c) model component | XNL(m) = ∑kAk, m − kXG(k)XG(m − k) | Eqs. (14)–(16) | X(m) = XG(m)+XNL(m) |
| fNL(k) | NL (c) fraction of P(k) |
 |
Eqs. (D.1),(D.2) | |
| bP | Bicoherence (P-norm.) |
 |
Eqs. (D.3),(D.2) |
 |
| fNL | NL (c) fraction of σ2 |
 |
Eq. (D.5) |
Notes. Estimators for these quantities are given by averaging realizations for estimating the expectation values in the above formulas; see Appendix B. ⟨f(x)⟩ denotes a spatial average of f. The data have zero spatial mean by construction.
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