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Fate of Large-Scale Structure in Modified Gravity After GW170817 and GRB170817A
Luca Amendola1, Martin Kunz2, Ippocratis D Saltas3
1InstiQuai Ernest Ansermettut für Theoretische Physik, Ruprecht-Karls-Universität Heidelberg, Philosophenweg 16, 69120 Heidelberg, Germany.
Physical Review Letters
|April 26, 2018
Summary
Gravitational wave speed constraints eliminate vector-tensor theories for gravitational slip. Conformal coupling in scalar-tensor theories remains viable, with dark matter growth matching general relativity (GR) or exceeding it.
Area of Science:
- Cosmology
- Gravitational Wave Astronomy
- Theoretical Physics
Background:
- The coincident detection of gravitational waves (GW) and gamma-ray bursts provides stringent constraints on GW speed.
- Gravitational slip (η) is linked to modifications in GW propagation.
Purpose of the Study:
- To investigate the implications of GW speed constraints on theories with gravitational slip.
- To identify viable cosmological models that allow for gravitational slip.
- To analyze structure formation within these viable models.
Main Methods:
- Constraining GW speed using multi-messenger observations.
- Analyzing theoretical frameworks for gravitational slip, including scalar-tensor and vector-tensor theories.
- Studying dark matter structure formation and the scale dependence of the slip parameter.
Main Results:
- New GW speed constraints rule out viable vector-tensor theories for generating gravitational slip.
- Conformal coupling to gravity in scalar-tensor theories is the only remaining viable source of gravitational slip.
- Dark matter growth rate must be at least as fast as in general relativity (GR), except possibly beyond the Horndeski model.
- If scale-dependent, the slip parameter approaches the GR value at large scales.
Conclusions:
- The GW speed constraint significantly narrows down viable modified gravity theories.
- Scalar-tensor theories with conformal coupling remain a focus for modified gravity research.
- Structure formation predictions are refined, with implications for dark matter behavior in modified gravity scenarios.
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