<p>We derive two model-independent results for spacetimes with globally bounded tidal fields. These are operational resolution scales of the local-inertial approximation and tidal dynamics; no spacetime discreteness is implied. Given an invariant bound <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\lambda _{\max }\le \lambda _\textrm{bound}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>λ</mi> <mo movablelimits="true">max</mo> </msub> <mo>≤</mo> <msub> <mi>λ</mi> <mtext>bound</mtext> </msub> </mrow> </math></EquationSource> </InlineEquation> on the electric Riemann eigenvalues <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(E_{ij}\equiv R_{\hat{0}i\hat{0}j}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>E</mi> <mrow> <mi mathvariant="italic">ij</mi> </mrow> </msub> <mo>≡</mo> <msub> <mi>R</mi> <mrow> <mover accent="true"> <mn>0</mn> <mo stretchy="false">^</mo> </mover> <mi>i</mi> <mover accent="true"> <mn>0</mn> <mo stretchy="false">^</mo> </mover> <mi>j</mi> </mrow> </msub> </mrow> </math></EquationSource> </InlineEquation> along freely falling worldlines, we prove (i)&#xa0;a rigorous upper bound on accumulated geodesic deviation through any bounded curvature interior, controlled by <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\tau _*\equiv \lambda _{\max }^{-1/2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mmultiscripts> <mi>τ</mi> <mrow> <mrow /> <mo>∗</mo> </mrow> <mrow /> </mmultiscripts> <mo>≡</mo> <msubsup> <mi>λ</mi> <mrow> <mo movablelimits="true">max</mo> </mrow> <mrow> <mo>-</mo> <mn>1</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> </msubsup> </mrow> </math></EquationSource> </InlineEquation>, and (ii)&#xa0;the existence of a critical wavenumber <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(k_*\sim \tau _*^{-1}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mmultiscripts> <mi>k</mi> <mrow> <mrow /> <mo>∗</mo> </mrow> <mrow /> </mmultiscripts> <mo>∼</mo> <mmultiscripts> <mi>τ</mi> <mrow> <mrow /> <mo>∗</mo> </mrow> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </mmultiscripts> </mrow> </math></EquationSource> </InlineEquation> separating adiabatic from non-adiabatic perturbation transfer through high-curvature epochs, with Bogoliubov coefficients exponentially suppressed for <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(k\,\tau _*\gg 1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>k</mi> <mspace width="0.166667em" /> <mmultiscripts> <mi>τ</mi> <mrow> <mrow /> <mo>∗</mo> </mrow> <mrow /> </mmultiscripts> <mo>≫</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation>. Both results depend only on the tidal bound (and, for mode transfer, on a mild timescale assumption for the curvature-driven effective potential) and are otherwise insensitive to metric details. For preparation, we collect the standard operational consequences of bounded curvature, including the accuracy-dependent local-inertial domain <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(L_\textrm{LI}(\varepsilon )\sim \sqrt{\varepsilon }\, \lambda _{\max }^{-1/2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>L</mi> <mtext>LI</mtext> </msub> <mrow> <mo stretchy="false">(</mo> <mi>ε</mi> <mo stretchy="false">)</mo> </mrow> <mo>∼</mo> <msqrt> <mi>ε</mi> </msqrt> <mspace width="0.166667em" /> <msubsup> <mi>λ</mi> <mrow> <mo movablelimits="true">max</mo> </mrow> <mrow> <mo>-</mo> <mn>1</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> </msubsup> </mrow> </math></EquationSource> </InlineEquation> and, for conformally flat cores in four dimensions, the benchmark ratio <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\tau _*/L_*=24^{1/4}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mmultiscripts> <mi>τ</mi> <mrow> <mrow /> <mo>∗</mo> </mrow> <mrow /> </mmultiscripts> <mo stretchy="false">/</mo> <mmultiscripts> <mi>L</mi> <mrow> <mrow /> <mo>∗</mo> </mrow> <mrow /> </mmultiscripts> <mo>=</mo> <msup> <mn>24</mn> <mrow> <mn>1</mn> <mo stretchy="false">/</mo> <mn>4</mn> </mrow> </msup> </mrow> </math></EquationSource> </InlineEquation> with <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(L_*\equiv K_{\max }^{-1/4}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mmultiscripts> <mi>L</mi> <mrow> <mrow /> <mo>∗</mo> </mrow> <mrow /> </mmultiscripts> <mo>≡</mo> <msubsup> <mi>K</mi> <mrow> <mo movablelimits="true">max</mo> </mrow> <mrow> <mo>-</mo> <mn>1</mn> <mo stretchy="false">/</mo> <mn>4</mn> </mrow> </msubsup> </mrow> </math></EquationSource> </InlineEquation>. We quantify the robustness of this coefficient under departures from maximal symmetry via the Weyl-to-Kretschmann ratio <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(\epsilon _C\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>ϵ</mi> <mi>C</mi> </msub> </math></EquationSource> </InlineEquation>. The general framework is validated numerically in the extremal Hayward geometry.</p>

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Tidal deformation bounds and perturbation transfer in bounded curvature spacetimes

  • Martin Drobczyk

摘要

We derive two model-independent results for spacetimes with globally bounded tidal fields. These are operational resolution scales of the local-inertial approximation and tidal dynamics; no spacetime discreteness is implied. Given an invariant bound \(\lambda _{\max }\le \lambda _\textrm{bound}\) λ max λ bound on the electric Riemann eigenvalues \(E_{ij}\equiv R_{\hat{0}i\hat{0}j}\) E ij R 0 ^ i 0 ^ j along freely falling worldlines, we prove (i) a rigorous upper bound on accumulated geodesic deviation through any bounded curvature interior, controlled by \(\tau _*\equiv \lambda _{\max }^{-1/2}\) τ λ max - 1 / 2 , and (ii) the existence of a critical wavenumber \(k_*\sim \tau _*^{-1}\) k τ - 1 separating adiabatic from non-adiabatic perturbation transfer through high-curvature epochs, with Bogoliubov coefficients exponentially suppressed for \(k\,\tau _*\gg 1\) k τ 1 . Both results depend only on the tidal bound (and, for mode transfer, on a mild timescale assumption for the curvature-driven effective potential) and are otherwise insensitive to metric details. For preparation, we collect the standard operational consequences of bounded curvature, including the accuracy-dependent local-inertial domain \(L_\textrm{LI}(\varepsilon )\sim \sqrt{\varepsilon }\, \lambda _{\max }^{-1/2}\) L LI ( ε ) ε λ max - 1 / 2 and, for conformally flat cores in four dimensions, the benchmark ratio \(\tau _*/L_*=24^{1/4}\) τ / L = 24 1 / 4 with \(L_*\equiv K_{\max }^{-1/4}\) L K max - 1 / 4 . We quantify the robustness of this coefficient under departures from maximal symmetry via the Weyl-to-Kretschmann ratio \(\epsilon _C\) ϵ C . The general framework is validated numerically in the extremal Hayward geometry.