Galaxy rotation curves in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>f</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mi>R</mml:mi><mml:mo>,</mml:mo><mml:mi>ϕ</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math>gravity

We consider models of Extended Gravity and in particular, generic models containing scalartensor and higher-order curvature terms, as well as a model derived from noncommutative spectral geometry. Studying, in the weak-field approximation, the geodesic and Lense-Thirring processions, we impose constraints on the free parameters of such models by using the recent experimental results of the Gravity Probe B and LARES satellites.

show abstract

“…while all other possible contributions in f are negligible [34][35][36]. The field equations (2), (3) and (4) hence read…”

Section: The Weak-field Limitmentioning

confidence: 99%

Constraining models of extended gravity using Gravity Probe B and LARES experiments

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…This theory can give the correct amount of inflation in agreement with the cosmological data while provides at the same time a graceful exit from the inflationary epoch [18,19]. Also the problem of rotation curves of spiral galaxies can be addressed in f (R, φ) gravity [20]. Many studies of primordial perturbations in this theory was firstly formulated by Hwang and his collaborators [21][22][23][24] and then discussed in [25].…”

Section: Introductionmentioning

confidence: 97%

“…(19) and (20), are two constraints imposed on the fluctuations. This is similar to general relativity in which there are two dynamical equations for the metric and scalar fluctuations together with a constraint equation in the Newtonian gauge.…”

Section: Scalar Perturbations In Generalized Scalar-tensor Gravitymentioning

confidence: 99%

On the initial conditions of scalar and tensor fluctuations in $$f(R,\phi )$$ f ( R , ϕ ) gravity

Cheraghchi

Shojai

2018

Eur. Phys. J. C

View full text Add to dashboard Cite

We have considered the perturbation equations governing the growth of fluctuations during inflation in generalized scalar tensor theory f (R, φ). We have found that the scalar metric perturbations at very early times are negligible compared to the scalar field perturbation, just like general relativity. At sufficiently early times, when the physical momentum of perturbation mode, q/a is much larger than the Hubble parameter H , i.e. q/a H , we have obtained the metric and scalar field perturbation in the form of WKB solutions up to an undetermined coefficient. Then we have quantized the scalar fluctuations and expanded the metric and the scalar field perturbations with the help of annihilation and creation operators of the scalar field perturbation. The standard commutation relations of annihilation and creation operators fix the unknown coefficient. Going over to the gauge invariant quantities which are conserved beyond the horizon, we have obtained the initial condition of the generalized Mukhanov-Sasaki equation. Then a similar procedure is performed for the case of tensor metric perturbation. As an example of the generalized Mukhanov-Sasaki equation and its initial condition, we have proposed a power-law functional form as f (R, φ) = f 0 R m φ n and obtained an exact inflationary solution. In this background, then we have discussed how the scalar and tensor fluctuations grow.

show abstract

“…while all other possible contributions in f are negligible [45,72,73]. By introducing the quantities…”

Section: The Scalar Tensor Fourth Order Gravitymentioning

confidence: 99%

“…where [73]. The solutions of the gravitational potential Φ and Ψ, derived from the first two equations of set (8) are…”

Section: The Scalar Tensor Fourth Order Gravitymentioning

confidence: 99%

Casimir effect in extended theories of gravity

Lambiase

Stabile

2017

Phys. Rev. D

Self Cite

View full text Add to dashboard Cite

We study the Casimir vacuum energy density and the Casimir pressure for a massless scalar field confined between two nearby parallel plates in a slightly curved, static spacetime background, employing the weak field approximation in the framework of Extended Theories of Gravity (ETG). Following a perturbative approach upto second order, we find the gravity correction in the ETG to Casimir vacuum energy density and pressure. The corrections to the vacuum energy density in presence of curved spacetime in the framework of General Relativity (GR) are small and today they are still undetected with the current technology. However, future sensitivity improvement in gravitational interferometer experiments will give an useful tool to detect such effect induced by gravity. For these reason we retain interesting from a theoretical point of view generalize the outcomes of GR in the context of ETG. Finally, we find the general relation to constraining the free parameters of the ETG.

show abstract

Galaxy rotation curves inf(R,ϕ)gravity

Cited by 58 publications

References 44 publications

Constraining models of extended gravity using Gravity Probe B and LARES experiments

Constraining models of extended gravity using Gravity Probe B and LARES experiments

On the initial conditions of scalar and tensor fluctuations in $$f(R,\phi )$$ f ( R , ϕ ) gravity

Casimir effect in extended theories of gravity

Contact Info

Product

Resources

About