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Dynamics of Screening in Modified Gravity
General Relativity and Quantum Cosmology · Submitted 7 Sep 2020
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim This casts doubts on whether the dynamical evolution of screened stars may be predicted in these effective field theories.
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The abstract, sentence by sentence
Gravitational theories differing from General Relativity may explain the accelerated expansion of the Universe without a cosmological constant. However, to pass local gravitational tests, a "screening mechanism" is needed to suppress, on small scales, the fifth force driving the cosmological acceleration. We consider the simplest of these theories, i.e. a scalar-tensor theory with first-order derivative self-interactions, and study isolated (static and spherically symmetric) non-relativistic and relativistic stars. We produce screened solutions and use them as initial data for non-linear numerical evolutions in spherical symmetry. We find that these solutions are stable under large initial perturbations, as long as they do not cause gravitational collapse. When gravitational collapse is triggered, the characteristic speeds of the scalar evolution equation diverge, even before apparent black-hole or sound horizons form. This casts doubts on whether the dynamical evolution of screened stars may be predicted in these effective field theories.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Gravitational theories differing from General Relativity may explain the accelerated expansion of the Universe without a cosmological constant. | background 1.00 | 0.05 | 0.03 | hedged possibility 1.00 |
| s1 | However, to pass local gravitational tests, a "screening mechanism" is needed to suppress, on small scales, the fifth force driving the cosmological acceleration. | background 1.00 | 0.04 | 0.03 | asserted 0.99 |
| s2 | We consider the simplest of these theories, i.e. a scalar-tensor theory with first-order derivative self-interactions, and study isolated (static and spherically symmetric) non-relativistic and relativistic stars. | contribution 0.74 | 0.86 | 0.03 | asserted 0.89 |
| s3 | We produce screened solutions and use them as initial data for non-linear numerical evolutions in spherical symmetry. | method 0.97 | 0.96 | 0.03 | asserted 0.98 |
| s4 | We find that these solutions are stable under large initial perturbations, as long as they do not cause gravitational collapse. | result 1.00 | 0.96 | 0.21 | asserted 1.00 |
| s5 | When gravitational collapse is triggered, the characteristic speeds of the scalar evolution equation diverge, even before apparent black-hole or sound horizons form. | result 1.00 | 0.90 | 0.25 | asserted 1.00 |
| s6 | This casts doubts on whether the dynamical evolution of screened stars may be predicted in these effective field theories. | interpretation 1.00 | 0.61 | 0.77 | hedged possibility 0.97 |
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The paper
Original abstract
Gravitational theories differing from General Relativity may explain the accelerated expansion of the Universe without a cosmological constant. However, to pass local gravitational tests, a "screening mechanism" is needed to suppress, on small scales, the fifth force driving the cosmological acceleration. We consider the simplest of these theories, i.e. a scalar-tensor theory with first-order derivative self-interactions, and study isolated (static and spherically symmetric) non-relativistic and relativistic stars. We produce screened solutions and use them as initial data for non-linear numerical evolutions in spherical symmetry. We find that these solutions are stable under large initial perturbations, as long as they do not cause gravitational collapse. When gravitational collapse is triggered, the characteristic speeds of the scalar evolution equation diverge, even before apparent black-hole or sound horizons form. This casts doubts on whether the dynamical evolution of screened stars may be predicted in these effective field theories.
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References
How the literature uses it
23 arXiv papers cite this in 77 sentences
Papers citing it · 54 sentences without a confident label
Uses its method or tool 2 papers
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To apply the method of Refs. [ref] , let us first recall that Ref. [ref] found that in order to deal with shocks appearing in $k$-mouflage stars, the scalar field equation needs to be written as a conservation law [cf. Eq. [ref]].
Kinetic screening in nonlinear stellar oscillations and gravitational collapse · Gravitational collapse · 0.97
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For the fluid and the scalar, we use High-Resolution Shock-Capturing (HRSC) methods to deal with shocks, as discussed in [ref] .
No evidence of kinetic screening in simulations of merging binary neutron stars beyond general relativity · Introduction · 0.95
Compares with it 3 papers
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We also show, as a reference, the standard screened solution of $k$-essence [ref] , where only the linear coupling is present (red solid line).
Robustness of kinetic screening against matter coupling · Couplings to matter dependent on \(φ\) · 0.97
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We also compared with simulations of perturbed stars, which were performed with an independent 1+1 code in spherical symmetry [ref] .
No evidence of kinetic screening in simulations of merging binary neutron stars beyond general relativity · Appendix B: Code validation · 0.95
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In Ref. [ref] , a similar result was reported for the kinetic screening mechanism (the K-Mouflage model): the fifth force does not affect the dynamics of the matter unless the gravitational collapse happens.
Dynamical Analysis of Screening in Scalar-Tensor Theory · Conclusion · 0.97
Cites it as support 4 papers
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In $k$-essence, because local kinetic screening is efficient at suppressing scalar effects near compact stars [ref] , it is reasonable to assume $s_i≈0$ also for neutron stars.
Scalar emission from neutron star-black hole binaries in scalar-tensor theories with kinetic screening · Theoretical setup · 0.96
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This screening mechanism is radiatively stable against quantum corrections from light degrees of freedom [ref] , allows for novel cosmologies [ref] and has also been observed in the strong gravity regime in numerical simulations [ref] .
Scalar Fields Near Compact Objects: Resummation versus UV Completion · Resummation and $K$-mouflage Screening · 0.97
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For this reason, and because efficient local kinetic screening around compact stars suggests that neutron-star sensitivities in $K$-essence are small to begin with [ref] , in the numerical simulations presented below we set $s_1=s_2=0$ (so that $α_1=α_2=α$) without loss of generality: our results apply to arbitrary pairs of neutron-star sensitivities through the rescaling above.
Scalar emission from binary neutron stars in scalar-tensor theories with kinetic screening · Theoretical setup · 0.97
Cites it as background 8 papers
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\(logΦ\) depends only linearly on $φ$, a screening mechanism referred to as \(k\)-mouflage (or kinetic screening) [ref] suppresses the scalar force in the vicinity of a massive body, allowing for passing Solar System tests without imposing any bound on $α_1$ [ref] .
Robustness of kinetic screening against matter coupling · Introduction · 0.86
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Let us start by reviewing the solution to the field equations when the point-particle representing the neutron star is at rest [ref] .
Scalar emission from neutron star-black hole binaries in scalar-tensor theories with kinetic screening · Static one-body problem and near-zone solution · 0.84
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Recently, significant effort has been directed at producing numerical simulations of the full non-linear dynamics in both $k$-essence [ref] and in theories with Vainshtein screening [ref] (in the flat spacetime limit)[Simulations have also been performed in other scalar-tensor theories in the Hordenski class that do not exhibit screening [ref] .].
Two-body problem in theories with kinetic screening · Introduction · 0.81
What it cites · 28 sentences without a confident label
Builds on 1 paper
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By studying static and spherically symmetric solutions, we confirm the presence of “kinetic” screening ($k$-mouflage [ref] ) in non-relativistic stars, and extend it to fully relativistic, compact stars.
k-Mouflage gravity · Introduction · 0.87
Uses the method or tool of 8 papers
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We then consider spherically symmetric time evolutions of these screened solutions, using the fully non-linear code of [ref] .
K-dynamics: well-posed 1+1 evolutions in K-essence · Introduction · 1.00
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We employ the 1+1 (i.e. spherically symmetric but time-dependent) fully non-linear evolution code used in [ref] for the vacuum case, supplementing it with matter as described in [ref] .
Dynamical evolution of fermion-boson stars · Introduction · 0.98
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A possible practical solution to evolve the dynamics of $k$-mouflage may consist of using implicit methods [ref] .
Beyond ideal MHD: towards a more realistic modeling of relativistic astrophysical plasmas · Introduction · 0.94
Compares with 2 papers
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This is markedly different than in GR [ref] or FJBD [ref] , where spherical dynamical simulations of compact objects present no such problems.
Evolution of Binary Black Hole Spacetimes · Introduction · 0.97
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This is markedly different than in GR [ref] or FJBD [ref] , where spherical dynamical simulations of compact objects present no such problems.
Neutron-star mergers in scalar-tensor theories of gravity · Introduction · 0.97
Cites as support 6 papers
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Even for these initial data, numerical evolutions break with standard finite-difference or even soft shock-capturing methods, presumably as a result of strong micro-shocks in the scalar field [ref] , which form even from smooth initial data.
Formation of caustics in k-essence and Horndeski theory · Introduction · 0.96
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Even for these initial data, numerical evolutions break with standard finite-difference or even soft shock-capturing methods, presumably as a result of strong micro-shocks in the scalar field [ref] , which form even from smooth initial data.
Shock Formation in Lovelock Theories · Introduction · 0.96
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Even for these initial data, numerical evolutions break with standard finite-difference or even soft shock-capturing methods, presumably as a result of strong micro-shocks in the scalar field [ref] , which form even from smooth initial data.
Challenges to global solutions in Horndeski's theory · Introduction · 0.96
Cites as background 10 papers
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However, some theories possess “screening mechanisms” (Vainshtein screening [ref] , $k$-mouflage [ref] , chameleon/symmetron screening [ref] , etc.) that locally produce a GR-like phenomenology, potentially passing existing constraints.
An introduction to the Vainshtein mechanism · Introduction · 0.82
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However, some theories possess “screening mechanisms” (Vainshtein screening [ref] , $k$-mouflage [ref] , chameleon/symmetron screening [ref] , etc.) that locally produce a GR-like phenomenology, potentially passing existing constraints.
Symmetron Fields: Screening Long-Range Forces Through Local Symmetry Restoration · Introduction · 0.82
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However, some theories possess “screening mechanisms” (Vainshtein screening [ref] , $k$-mouflage [ref] , chameleon/symmetron screening [ref] , etc.) that locally produce a GR-like phenomenology, potentially passing existing constraints.
k-Mouflage gravity · Introduction · 0.82
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