Warped brane worlds in critical gravity

Abstract

We investigate the brane models in arbitrary dimensional critical gravity presented in Lu and Pope (Phys Rev Lett 106:181302, 2011). For the models of the thin branes with codimension one, the Gibbons-Hawking surface term and the junction conditions are derived, with which the analytical solutions for the flat, AdS, and dS branes are obtained at the critical point of the critical gravity. It is found that all these branes are embedded in an AdS n spacetime, but, in general, the effective cosmological constant Λ of the AdS n spacetime is not equal to the naked one Λ 0 in the critical gravity, which can be positive, zero, and negative. Another interesting result is that the brane tension can also be positive, zero, or negative, depending on the symmetry of the thin brane and the values of the parameters of the theory, which is very different from the case in general relativity. It is shown that the mass hierarchy problem can be solved in the braneworld model in the higher-derivative critical gravity. We also study the thick brane model and find analytical and numerical solutions of the flat, AdS, and dS branes. It is found that some branes will have inner structure when some parameters of the theory are larger than their critical values, which may result in resonant KK modes for some bulk matter fields. The flat branes with positive energy density and AdS branes with negative energy density are embedded in an n-dimensional AdS spacetime, while the dS branes with positive energy density are embedded in an n-dimensional Minkowski one.

Hypervelocity Stars

“…There are a wide variety of other candidate HVSs identified primarily by tangential velocity. These tangential velocity outliers include a 2.5-M A star (Tillich et al 2009), a 5-M B star (Irrgang et al 2010), an evolved sdB star (Tillich et al 2011), some metal-poor F stars (Li et al 2012), a metal-poor CH giant star (Pereira et al 2012), two red horizontal branch stars (Pereira et al 2013), nearby G and K stars (Palladino et al 2014), and a mix of nearby stars from LAMOST (Zhong et al 2014).…”

“…False-positives are problematic because proper motions cannot be easily checked given the required time baseline for their measurement. If one takes published error bars at face value, those HVS candidates unbound at >1-σ confidence are the sdB star J1211+1437 (Tillich et al 2011), the metal-poor F star J2218−0040 (Li et al 2012), the A/F stars J085819.9+150352 and J092707.0+242753 (Zhong et al 2014), and perhaps a dozen of the G and K dwarfs (Palladino et al 2014). All these objects are near the Galactic disk.…”

Introduction to Extra Dimensions and Thick Braneworlds

“…It is easy to show that the zero mode of the graviton can be localized on the brane for the above mentioned solutions. Furthermore, there were some related work in other gravity theories, such as Weyl (pure geometrical) gravity [134][135][136][137][138][139] and critical gravity [140,141].…”

Frame-invariant approach to higher-dimensional scalar-tensor gravity

“…This scheme has been dubbed the braneworld scenario. A number of models have been proposed [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65] realizing the idea of modeling the brane with a scalar field configuration and the gravitational part of the action is non-minimally coupled to a fundamental or an auxiliary scalar field, as in the case of f (R) gravity. In the present article, we examine 5D models of scalars coupled non-minimally to gravity, in the framework of a frame-invariant formulation and focus on the study of thick braneworld solutions.…”