10 papers found.

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. Living Rev. Relativ. 6, 5 (2003)ADSzbMATHGoogle Scholar
35.
Shaoqi Hou, **Yungui** **Gong**, Constraints on Horndeski theory using the observations of Nordtvedt effect, Shapiro time delay and binary pulsars. Eur ... , Scalar–tensor theories and modified gravity in the wake of GW170817. Phys. Rev. D 97(6), 061501 (2018)ADSGoogle Scholar
56.
**Yungui** **Gong**, Eleftherios Papantonopoulos, Zhu Yi, Constraints on scalar–tensor

The speed of gravitational waves provides us a new tool to test alternative theories of gravity. The constraint on the speed of gravitational waves from GW170817 and GRB170817A is used to test some classes of Horndeski theory. In particular, we consider the coupling of a scalar field to Einstein tensor and the coupling of the Gauss–Bonnet term to a scalar field. The coupling...

Alternative theories of gravity not only modify the polarization contents of the gravitational wave, but also affect the motions of the stars and the energy radiated away via the gravitational radiation. These aspects leave imprints in the observational data, which enables the test of general relativity and its alternatives. In this work, the Nordtvedt effect and the Shapiro time...

Abstract We study the non-equilibrium condensation process in a holographic superconductor with nonlinear corrections to the U (1) gauge field. We start with an asymptotic Anti-de-Sitter (AdS) black hole against a complex scalar perturbation at the initial time, and solve the dynamics of the gravitational systems in the bulk. When the black hole temperature T is smaller than a...

We perform a dynamical analysis for the exponential scalar field with non-minimally derivative coupling. For the quintessence case, the stable fixed points are the same with and without the non-minimally derivative coupling. For the phantom case, the attractor with dark energy domination exists for the minimal coupling only. For the non-minimally derivative coupling without the...

With the usual definitions for the entropy and the temperature associated with the apparent horizon, we show that the unified first law on the apparent horizon is equivalent to the Friedmann equation for the scalar–tensor theory with non-minimally derivative coupling. The second law of thermodynamics on the apparent horizon is also satisfied. The results support a deep and...

The dynamics of scalar fields as dark energy is well approximated by some general relations between the equation of state parameter \(w(z)\) and the fractional energy density \(\varOmega _\phi \). Based on the approximation, for slowly rolling scalar fields, we derived the analytical expressions of \(w(z)\) which reduce to the popular Chevallier–Polarski–Linder parametrization...

The constraints on the Λ cold dark matter (ΛCDM) model from Type Ia supernova (SNe Ia) data alone and baryon acoustic oscillation (BAO) data alone are similar, so it is worthwhile to compare their constraints on the property of dark energy. We apply the three-year Supernova Legacy Survey (SNLS3) compilation of 472 SNe Ia data, the BAO measurement of distance, the cosmic microwave...

We apply the Union2 compilation of 557 supernova Ia data, the baryon acoustic oscillation measurement of distance, the cosmic microwave background radiation data from the 7-year Wilkinson Microwave Anisotropy Probe, and the Hubble parameter data to study the geometry of the Universe and the property of dark energy by using models and parametrizations with different high-redshift...

The recent observations of Type Ia supernovae suggest that the Universe is accelerating now and decelerated in the recent past. This may be the evidence of the breakdown of the standard Friedmann equation. The Friedmann equation H2∼ρ is modified to be a general form H2=g(ρ). Three models with particular form of g(ρ) are considered in detail. The supernova data published by Tonry...