cosmocore.spectrum_key module

Canonical key types for spectra and Fisher blocks. Defines SpectrumKey, the structural SpectrumKind enum (ordered slot pairs), and the SymmetryMode flag controlling how cross-component E/B spectra are emitted. CMB-friendly aliases (TT/EE/BB/EB/BE/TE/ET/TB/BT) live in cosmocore.conventions.cmb.

class cosmocore.spectrum_key.SymmetryMode(*values)

Bases: Enum

How cross-component spin-2 × spin-2 EB-like spectra are treated.

SYMMETRIC (default) — emits one combined GC spectrum per cross-pair; the Lambda model uses a single C_EB in both off-diagonal blocks. Standard cosmology (C_EB = 0) makes this numerically identical to DIRECTIONAL.

DIRECTIONAL — emits both GC (E_i × B_j) and CG (B_i × E_j) as separate spectra. Lambda uses C_GC and C_CG independently. Opt-in for polarisation angle calibration diagnostics and parity-violation searches. See ADR-0011.

SYMMETRIC = 'symmetric'

DIRECTIONAL = 'directional'

class cosmocore.spectrum_key.Slot(label, spin)

Bases: Enum

Sub-mode within a spin-s component.

S = scalar (spin-0 field’s only slot; CMB alias: T). G = gradient (parity-even slot of a spin-2 field; CMB alias: E). C = curl (parity-odd slot of a spin-2 field; CMB alias: B).

S = ('S', 0)

G = ('G', 2)

C = ('C', 2)

__init__(label, spin)

class cosmocore.spectrum_key.SpectrumKind(slot_i, slot_j)

Bases: Enum

Directional spectrum kind: an ordered slot pair (slot_i, slot_j).

Nine values cover every (slot_i, slot_j) reachable from spin-0 and spin-2 components. Asymmetry is preserved (SG != GS, GC != CG); whether to collapse to a symmetric average is a separate decision driven by the SymmetryMode flag on Spectra/Fisher.

SS = (Slot.S, Slot.S)

GG = (Slot.G, Slot.G)

CC = (Slot.C, Slot.C)

GC = (Slot.G, Slot.C)

CG = (Slot.C, Slot.G)

SG = (Slot.S, Slot.G)

GS = (Slot.G, Slot.S)

SC = (Slot.S, Slot.C)

CS = (Slot.C, Slot.S)

__init__(slot_i, slot_j)

property required_spins: tuple[int, int]

class cosmocore.spectrum_key.SpectrumKey(comp_i, comp_j, kind, *, spins=None)

Bases: object

Identifier for one cross/auto power spectrum.

Passive identifier — does not symmetrise, canonicalise, or perform algebra. Constructor validates that kind’s required spins match the actual spins at comp_i and comp_j.

comp_i: int

comp_j: int

kind: SpectrumKind

__init__(comp_i, comp_j, kind, *, spins=None)

cosmocore.spectrum_key.kind_to_legacy_mode(kind, *, is_cross=False)

Bridge for migration: map SpectrumKind to the legacy int mode.

For spin-2 × spin-2 the mode→kind mapping is context-dependent and must match _spin_pair_mode_to_kind (above) in this module:

• Auto-pair (is_cross=False, default): [GG=0, CC=1, GC=2]. CG has no slot here — auto-pair derivative builders emit the symmetrised GC matrix and never distinguish E_i B_j from B_i E_j.

• Cross-pair (is_cross=True): [GG=0, GC=1, CG=2, CC=3] — the 4-entry ordering used by PolarizationField.get_cross_spectrum_labels and DIRECTIONAL-mode derivative construction.

All other spin pairs have a single ordering independent of is_cross.

Return type:

int