Scalaron production in contracting astrophysical objects
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calaron Production in Contracting Astrophysical Objects1 D. Gorbunova,b,* and A. Tokarevaa,c a
b
Institute for Nuclear Research, Russian Academy of Sciences, Moscow, 117312 Russia Moscow Institute of Physics and Technology, Dolgoprudny, Moscow oblast, 141700 Russia c Faculty of Physics, Moscow State University, Moscow, 119991 Russia *email: [email protected] Received October 24, 2014
Abstract—We study the creation of highenergy SM particles in the Starobinsky model of dark energy (a vari ant of F(R)gravity) inside the regions contracting due to the Jeans instability. In this modification of gravity, the additional degree of freedom—a scalaron—behaves as a particle with the mass depending on matter den sity. Therefore, when the mass changes, light scalarons could be created at a nonadiabatic stage. Later, the scalaron mass grows and can reach large values, even the value 1013 GeV, favored by early time inflation. Heavy scalarons decay contributing to the cosmic ray flux. We analytically calculate the number density of created particles for the exponential (Jeans) contraction and find it negligibly small for the phenomenologi cally viable and cosmologically interesting range of model parameters. We expect similar results for a generic model of F(R)gravity mimicking the cosmological constant. Contribution for the JETP special issue in honor of V.A.Rubakov’s 60th birthday DOI: 10.1134/S1063776115030085 1
1. INTRODUCTION Numerous observational data require a new com ponent in the righthand side of the Einstein equa tions, which is called dark energy and which causes the accelerated expansion of the Universe. The simplest and still viable candidate for dark energy is obviously a cosmological constant. But its unnaturally small value engenders investigation of other ways to explain the observational data. F(R)gravity provides a framework for constructing models of dark energy with the time dependent equa tion of state p/ρ ≡ w = w(t); moreover, at some stage we have w < –1 (see [1] for a review). Such models of modified gravity may also explain the inflationary stage of the early Universe, providing a unified mech anism to describe both stages of accelerated expan sion. The choice of the function F(R) is still phenome nological to a large extent. It must be selfconsistent from the theoretical standpoint, explain the cosmo logical data, and pass all Solar System and astrophysi cal tests. The natural question is: How to distinguish F(R)gravity from other models of dark energy? The most straightforward way is to improve the sensitivity of the overall cosmological analysis to the dark energy equation of state. However, besides serious systematic uncertainties, there are physically motivated degener acies in the cosmological observables with respect to 1 The article is published in the original.
physical parameters. In particular, specific effects of F(R)gravity at small spatial scales can be canceled by massive (sterile) neutrinos, whose dynamics works against modified gravity [2]. An attractive idea
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