Warpax toolkit demonstrates that observer-robust optimization finds more extensive and severe energy-condition violations in warp drive metrics than single-frame Eulerian analysis.
xPerm: fast index canonicalization for tensor computer algebra
9 Pith papers cite this work. Polarity classification is still indexing.
9
Pith papers citing it
abstract
We present a very fast implementation of the Butler-Portugal algorithm for index canonicalization with respect to permutation symmetries. It is called xPerm, and has been written as a combination of a Mathematica package and a C subroutine. The latter performs the most demanding parts of the computations and can be linked from any other program or computer algebra system. We demonstrate with tests and timings the effectively polynomial performance of the Butler-Portugal algorithm with respect to the number of indices, though we also show a case in which it is exponential. Our implementation handles generic tensorial expressions with several dozen indices in hundredths of a second, or one hundred indices in a few seconds, clearly outperforming all other current canonicalizers. The code has been already under intensive testing for several years and has been essential in recent investigations in large-scale tensor computer algebra.
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representative citing papers
In a beyond-GR cubic-curvature model, loss of isospectrality makes it generally difficult to identify the two fundamental quasinormal modes from black hole ringdown time series, though evidence for a non-GR mode is sometimes possible.
Spectral functions for graviton and scalar graviton modes are derived in Lorentzian asymptotically safe quantum gravity via adapted FRG flow equations, yielding normalisable results consistent with infrared effective theory.
A conformally invariant weight-six correction to the anomaly-induced effective action leaves a free parameter in the semiclassical stress tensor near a Schwarzschild black hole, producing quantum hair.
Specific choices of form factors in ghost-free infinite derivative gravity cancel all one-loop logarithmic UV divergences except the Gauss-Bonnet term and a surface term.
Develops a Lagrangian path integral formulation for non-projectable Hořava gravity and computes one-loop divergences in (2+1) dimensions, verifying cancellation of linear-in-frequency terms to extract beta functions for Newton constant and λ.
Semiclassical black hole evaporation in four dimensions produces a thunderbolt singularity signaling breakdown of the effective theory at large distances.
Proper-time flow yields positive gravitational corrections to gauge beta functions and negative leading corrections to Yukawa beta functions at the Einstein-Hilbert fixed point, with quantified scheme dependence and limited room for interactive matter fixed points.
Causality from Shapiro delay and UV species/perturbativity bounds force the dynamical Chern-Simons coupling to be tiny for macroscopic gravitational systems.
citing papers explorer
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Observer-robust energy condition verification for warp drive spacetimes
Warpax toolkit demonstrates that observer-robust optimization finds more extensive and severe energy-condition violations in warp drive metrics than single-frame Eulerian analysis.
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Quasinormal modes and their excitation beyond general relativity. II: isospectrality loss in gravitational waveforms
In a beyond-GR cubic-curvature model, loss of isospectrality makes it generally difficult to identify the two fundamental quasinormal modes from black hole ringdown time series, though evidence for a non-GR mode is sometimes possible.
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Spectral Functions of Lorentzian Quantum Gravity
Spectral functions for graviton and scalar graviton modes are derived in Lorentzian asymptotically safe quantum gravity via adapted FRG flow equations, yielding normalisable results consistent with infrared effective theory.
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Conformally Invariant Corrections to the Anomaly-Induced Effective Action and Black Hole Evaporation in Four Dimensions
A conformally invariant weight-six correction to the anomaly-induced effective action leaves a free parameter in the semiclassical stress tensor near a Schwarzschild black hole, producing quantum hair.
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Cancellation of UV divergences in ghost-free infinite derivative gravity
Specific choices of form factors in ghost-free infinite derivative gravity cancel all one-loop logarithmic UV divergences except the Gauss-Bonnet term and a surface term.
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Quantizing non-projectable Ho\v{r}ava gravity with Lagrangian path integral
Develops a Lagrangian path integral formulation for non-projectable Hořava gravity and computes one-loop divergences in (2+1) dimensions, verifying cancellation of linear-in-frequency terms to extract beta functions for Newton constant and λ.
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Breakdown of Semiclassical Gravity in Four-Dimensional Black Hole Evaporation
Semiclassical black hole evaporation in four dimensions produces a thunderbolt singularity signaling breakdown of the effective theory at large distances.
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Quantum gravity contributions to the gauge and Yukawa couplings in proper time flow
Proper-time flow yields positive gravitational corrections to gauge beta functions and negative leading corrections to Yukawa beta functions at the Einstein-Hilbert fixed point, with quantified scheme dependence and limited room for interactive matter fixed points.
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Theoretical and Observational Bounds on Dynamical Chern-Simons Gravity as an Effective Field Theory
Causality from Shapiro delay and UV species/perturbativity bounds force the dynamical Chern-Simons coupling to be tiny for macroscopic gravitational systems.