v0.3.0

v0.3.0 - Peierls gauge coupling + calibration boundary

dcl_core v0.3.0 is a MINOR release that lands the core3d gauge-channel
infrastructure and the extensional calibration boundary needed for the next
Paper IV phase.

Highlights

• Added U(1) Peierls gauge coupling in core3d (vector_potential / spatial A).
• Added electric-sector threading via external_potential (A_0) in the same hop path.
• Added uniform_B_potential(shape, B_vec) helper for uniform-background magnetic fields.
• Added fused CuPy RawKernel hop-average path for large-lattice throughput.
• Added dcl_core.calibration as the single physical-unit conversion boundary.
• Added/landed exact induced-action Q-tensor cross-check reproducing Paper I's
  {4,4,16} eigenstructure and optical axis (1,1,-1).

Semver

MINOR (additive API): top-level export now includes dcl_core.calibration, and
core3d gained additive gauge-coupling surfaces. No public removals.

Notes on open work

The magnetic induced-action Q verdict is now exact and landed. The remaining
open load-bearing physics item is the full E+B photon-dispersion birefringence-order
classification (design-doc acceptance test #5).

Calibration caveat

Calibration.length_metres currently assumes a = c * tick_seconds.
That assumption is now part of the v0.3.0 contract; changing it later is a
breaking semantic change (MAJOR).

Installing

pip install "git+https://github.com/JackDMenendez/dcl-core@v0.3.0"

Citation

DOI: 10.5281/zenodo.21272238