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Solving the initial conditions problem for modified gravity theories

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arxiv 2308.16791 v2 pith:J4HTDKVY submitted 2023-08-31 gr-qc

classification gr-qc
keywords constraintstheoriesinitialtheoryadditionalclasscurvaturedata
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Modified gravity theories such as Einstein scalar Gauss Bonnet (EsGB) contain higher derivative terms in the spacetime curvature in their action, which results in modifications to the Hamiltonian and momentum constraints of the theory. In principle, such modifications may affect the principal part of the operator in the resulting elliptic equations, and so further complicate the already highly non-linear, coupled constraints that apply to the initial data in numerical relativity simulations of curved spacetimes. However, since these are effective field theories, we expect the additional curvature terms to be small, which motivates treating them simply as an additional source in the constraints, and iterating to find a solution to the full problem. In this work we implement and test a modification to the CTT/CTTK methods of solving the constraints for the case of the most general four derivative, parity invariant scalar-tensor theory, and show that solutions can be found in both asymptotically flat/black hole and periodic/cosmological spacetimes, even up to couplings of order unity in the theory. Such methods will allow for numerical investigations of a much broader class of initial data than has previously been possible in these theories, and should be straightforward to extend to similar models in the Horndeski class.

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Cited by 6 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Signatures from metastable oppositely-charged black hole binaries in scalar Gauss-Bonnet gravity

    gr-qc 2025-05 conditional novelty 7.0 of 10

    In scalar Gauss-Bonnet gravity, inspiraling black holes with opposite scalar charges can undergo a sudden charge-flip, changing scalar radiation from dipolar to quadrupolar and inducing orbital eccentricity.

  2. Towards long and accurate numerical relativity waveforms of binary black holes beyond general relativity

    gr-qc 2026-07 conditional novelty 6.5 of 10

    Spectral methods plus comoving fixing-the-equations drivers yield 40+ cycle equal-mass sGB binary waveforms with phase error ≲1 rad, distinguishable from GR and merging earlier.

  3. High-accuracy drivers to simulate black hole binaries beyond general relativity with the fixing-the-equations approach

    gr-qc 2026-07 conditional novelty 6.0 of 10

    Comoving tensor-aware driver equations in SpECTRE yield ~40-cycle sGB binary waveforms with O(1) rad phase error and eccentricity ≲10^{-3}, free of spurious spin growth.

  4. Challenges in the nonlinear evolution of unequal mass binaries in sGB gravity

    gr-qc 2025-07 conditional novelty 6.0 of 10

    First full merger simulations of 2:1 and 3:1 black hole binaries in scalar-Gauss-Bonnet gravity, with weak-coupling dephasing matching PN predictions but strong-coupling results limited by initial-data transients.

  5. Inflaton Dynamics in Higher-Derivative Scalar-Tensor Theories of Gravity

    gr-qc 2025-05 conditional novelty 6.0 of 10

    In the weakly coupled regime of a four-derivative scalar-tensor theory, large inflationary inhomogeneities decay just as in general relativity, and only finely tuned initial data can escape the effective field theory'...

  6. The initial data of effective field theories of relativistic viscous fluids and gravity

    gr-qc 2026-02 conditional novelty 5.0 of 10

    Initial data for the unphysical modes in well-posed EFTs should be fixed by order reduction, which suppresses fast modes without altering the equations of motion.

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