Paper

{
  "raw_xml": "<entry>\n    <id>http://arxiv.org/abs/2602.18023v1</id>\n    <title>Observer-robust energy condition verification for warp drive spacetimes</title>\n    <updated>2026-02-20T06:37:44Z</updated>\n    <link href='https://arxiv.org/abs/2602.18023v1' rel='alternate' type='text/html'/>\n    <link href='https://arxiv.org/pdf/2602.18023v1' rel='related' title='pdf' type='application/pdf'/>\n    <summary>We present \\textbf{warpax}, an open-source, GPU-accelerated Python toolkit for observer-robust energy condition analysis of warp drive spacetimes. Existing tools evaluate energy conditions for a finite sample of observer directions; \\textbf{warpax} replaces discrete sampling with continuous, gradient-based optimization over the timelike observer manifold (rapidity and boost direction), backed by Hawking--Ellis algebraic classification. At Type~I stress-energy points, which comprise ${&gt;}\\,96$\\% of all grid points across the tested metrics, an algebraic eigenvalue check determines energy-condition satisfaction \\emph{exactly}, independent of any observer search or rapidity cap. At non-Type~I points the optimizer provides rapidity-capped diagnostics. Stress-energy tensors are computed from the ADM metric via forward-mode automatic differentiation, eliminating finite-difference truncation error. Geodesic integration with tidal-force and blueshift analysis is also included.\n  We analyze five warp drive metrics (Alcubierre, Lentz, Van~Den~Broeck, Natário, Rodal) and one warp shell metric (used primarily as a numerical stress test). For the Rodal metric, the standard Eulerian-frame analysis misses violations at over $28\\%$ of grid points (dominant energy condition) and over $15\\%$ (weak energy condition). Even where the Eulerian frame identifies the correct violation set, observer optimization reveals that violation severity can be orders of magnitude larger (e.g.\\ Alcubierre weak energy condition: ${\\sim}\\,90{,}000\\times$ at rapidity cap $ζ_{\\max} = 5$, scaling as $e^{2ζ_{\\max}}$). These results demonstrate that single-frame evaluation can systematically underestimate both the spatial extent and the magnitude of energy condition violations in warp drive spacetimes. \\textbf{warpax} is freely available at https://github.com/anindex/warpax.</summary>\n    <category scheme='http://arxiv.org/schemas/atom' term='gr-qc'/>\n    <category scheme='http://arxiv.org/schemas/atom' term='cs.MS'/>\n    <category scheme='http://arxiv.org/schemas/atom' term='physics.comp-ph'/>\n    <published>2026-02-20T06:37:44Z</published>\n    <arxiv:comment>30 pages, 15 figures, 12 tables, submitted to Classical and Quantum Gravity</arxiv:comment>\n    <arxiv:primary_category term='gr-qc'/>\n    <author>\n      <name>An T. Le</name>\n    </author>\n  </entry>"
}