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Unified description of screened modified gravity (2012)
Journal Article
Brax, P., Davis, A., Li, B., & Winther, H. (2012). Unified description of screened modified gravity. Physical Review D, 86(4), Article 044015. https://doi.org/10.1103/physrevd.86.044015

We consider modified gravity models driven by a scalar field whose effects are screened in high density regions due to the presence of nonlinearities in its interaction potential and/or its coupling to matter. Our approach covers chameleon, f(R) grav... Read More about Unified description of screened modified gravity.

Chameleon f(R) gravity in the virialized cluster (2012)
Journal Article
Lombriser, L., Koyama, K., Zhao, G., & Li, B. (2012). Chameleon f(R) gravity in the virialized cluster. Physical Review D, 85(12), Article 124054. https://doi.org/10.1103/physrevd.85.124054

Current constraints on f(R) gravity from the large-scale structure are at the verge of penetrating into a region where the modified forces become nonlinearly suppressed. For a consistent treatment of observables at these scales, we study cluster quan... Read More about Chameleon f(R) gravity in the virialized cluster.

Halos and Voids in f(R) Gravity (2012)
Journal Article
Li, B., Zhao, G., & Koyama, K. (2012). Halos and Voids in f(R) Gravity. Monthly Notices of the Royal Astronomical Society, 421(4), 3481-3487. https://doi.org/10.1111/j.1365-2966.2012.20573.x

In this paper, we study the distribution of dark matter haloes and voids using high‐resolution simulations in f(R) gravity models with the chameleon mechanism to screen the fifth force in a dense environment. For dark matter haloes, we show that the... Read More about Halos and Voids in f(R) Gravity.

An extended excursion set approach to structure formation in chameleon models (2012)
Journal Article
Li, B., & Efstathiou, G. (2012). An extended excursion set approach to structure formation in chameleon models. Monthly Notices of the Royal Astronomical Society, 421(2), 1431-1442. https://doi.org/10.1111/j.1365-2966.2011.20404.x

In attempts to explain dark energy, a number of models have been proposed in which the formation of a large-scale structure depends on the local environment. These models are highly non-linear and difficult to analyse analytically. N-body simulations... Read More about An extended excursion set approach to structure formation in chameleon models.

Structure formation in the symmetron model (2012)
Journal Article
Davis, A., Li, B., Mota, D., & Winther, H. (2012). Structure formation in the symmetron model. Astrophysical Journal, 748(1), Article 61. https://doi.org/10.1088/0004-637x/748/1/61

Scalar fields, strongly coupled to matter, can be present in nature and still be invisible to local experiments if they are subject to a screening mechanism. The symmetron is one such mechanism that relies on restoration of a spontaneously broken sym... Read More about Structure formation in the symmetron model.

ECOSMOG: an Efficient COde for Simulating MOdified Gravity (2012)
Journal Article
Li, B., Zhao, G., Teyssier, R., & Koyama, K. (2012). ECOSMOG: an Efficient COde for Simulating MOdified Gravity. Journal of Cosmology and Astroparticle Physics, 2012(01), Article 051. https://doi.org/10.1088/1475-7516/2012/01/051

We introduce a new code, ECOSMOG, to run N-body simulations for a wide class of modified gravity and dynamical dark energy theories. These theories generally have one or more new dynamical degrees of freedom, the dynamics of which are governed by the... Read More about ECOSMOG: an Efficient COde for Simulating MOdified Gravity.

Linear growth of structure in the symmetron model (2011)
Journal Article
Brax, P., van de Bruck, C., Davis, A., Li, B., Schmauch, B., & Shaw, D. (2011). Linear growth of structure in the symmetron model. Physical Review D, 84, Article 123524. https://doi.org/10.1103/physrevd.84.123524

In the symmetron mechanism, the fifth force mediated by a coupled scalar field (the symmetron) is suppressed in high-density regions due to the restoration of symmetry in the symmetron potential. In this paper we study the background cosmology and la... Read More about Linear growth of structure in the symmetron model.

Testing gravity using the environmental dependence of dark matter halos (2011)
Journal Article
Zhao, G., Li, B., & Koyama, K. (2011). Testing gravity using the environmental dependence of dark matter halos. Physical Review Letters, 107(7), Article 071303. https://doi.org/10.1103/physrevlett.107.071303

In this Letter, we investigate the environmental dependence of dark matter halos in theories which attempt to explain the accelerated expansion of the Universe by modifying general relativity (GR). Using high-resolution N-body simulations in f(R) gra... Read More about Testing gravity using the environmental dependence of dark matter halos.

An analytic ray-tracing algorithm for weak lensing (2011)
Journal Article
Li, B., King, L., Zhao, G., & Zhao, H. (2011). An analytic ray-tracing algorithm for weak lensing. Monthly Notices of the Royal Astronomical Society, 415(1), 881-892. https://doi.org/10.1111/j.1365-2966.2011.18754.x

We propose a new ray-tracing algorithm to measure the weak-lensing shear and convergence fields directly from N-body simulations. We calculate the deflection of the light rays lensed by the 3D mass density field or gravitational potential along the l... Read More about An analytic ray-tracing algorithm for weak lensing.

Generalizations of teleparallel gravity and local Lorentz symmetry (2011)
Journal Article
Sotiriou, T., Li, B., & Barrow, J. (2011). Generalizations of teleparallel gravity and local Lorentz symmetry. Physical Review D, 83, Article 104030. https://doi.org/10.1103/physrevd.83.104030

We analyze the relation between teleparallelism and local Lorentz invariance. We show that generic modifications of the teleparallel equivalent to general relativity will not respect local Lorentz symmetry. We clarify the reasons for this and explain... Read More about Generalizations of teleparallel gravity and local Lorentz symmetry.

Nonlinear structure formation with the environmentally dependent dilaton (2011)
Journal Article
Brax, P., van de Bruck, C., Davis, A., Li, B., & Shaw, D. (2011). Nonlinear structure formation with the environmentally dependent dilaton. Physical Review D, 83, Article 104026. https://doi.org/10.1103/physrevd.83.104026

We have studied the nonlinear structure formation of the environmentally dependent dilaton model using N-body simulations. We find that the mechanism of suppressing the scalar fifth force in high-density regions works very well. Within the parameter... Read More about Nonlinear structure formation with the environmentally dependent dilaton.

Large-scale structure in f(T) gravity (2011)
Journal Article
Li, B., Sotiriou, T., & Barrow, J. (2011). Large-scale structure in f(T) gravity. Physical Review D, 83, Article 104017. https://doi.org/10.1103/physrevd.83.104017

In this work we study the cosmology of the general f(T) gravity theory. We express the modified Einstein equations using covariant quantities, and derive the gauge-invariant perturbation equations in covariant form. We consider a specific choice of f... Read More about Large-scale structure in f(T) gravity.

On the effects of coupled scalar fields on structure formation (2011)
Journal Article
Li, B., & Barrow, J. (2011). On the effects of coupled scalar fields on structure formation. Monthly Notices of the Royal Astronomical Society, 413(1), 262-270. https://doi.org/10.1111/j.1365-2966.2010.18130.x

A coupling between a scalar field (representing the dark energy) and dark matter could produce rich phenomena in cosmology. It affects cosmic structure formation mainly through the fifth force, a velocity-dependent force that acts parallel to particl... Read More about On the effects of coupled scalar fields on structure formation.

f(T) Gravity and local Lorentz invariance (2011)
Journal Article
Li, B., Sotiriou, T., & Barrow, J. (2011). f(T) Gravity and local Lorentz invariance. Physical Review D, 83(6), Article 064035. https://doi.org/10.1103/physrevd.83.064035

We show that in theories of generalized teleparallel gravity, whose Lagrangians are algebraic functions of the usual teleparallel Lagrangian, the action and the field equations are not invariant under local Lorentz transformations. We also argue that... Read More about f(T) Gravity and local Lorentz invariance.

Voids in coupled scalar field cosmology (2011)
Journal Article
Li, B. (2011). Voids in coupled scalar field cosmology. Monthly Notices of the Royal Astronomical Society, 411(4), 2615-2627. https://doi.org/10.1111/j.1365-2966.2010.17867.x

We study the properties of voids in two different types of coupled scalar field theories. Due to the fifth force produced by the scalar field coupling, the matter particles feel stronger attraction amongst each other and cluster more quickly than the... Read More about Voids in coupled scalar field cosmology.

Varying alpha from N-body simulations (2011)
Journal Article
Li, B., Mota, D., & Barrow, J. (2011). Varying alpha from N-body simulations. Astrophysical Journal, 728(2), Article 108. https://doi.org/10.1088/0004-637x/728/2/108

We have studied the Bekenstein-Sandvik-Barrow-Magueijo (BSBM) model for the spatial and temporal variations of the fine structure constant, α, with the aid of full N-body simulations that explicitly and self-consistently solve for the scalar field dr... Read More about Varying alpha from N-body simulations.

N-body simulations for extended quintessence models (2011)
Journal Article
Li, B., Mota, D., & Barrow, J. (2011). N-body simulations for extended quintessence models. Astrophysical Journal, 728(2), Article 109. https://doi.org/10.1088/0004-637x/728/2/109

We introduce the N-body simulation technique to follow structure formation in linear and nonlinear regimes for the extended quintessence models (scalar-tensor theories in which the scalar field has a self-interaction potential and behaves as dark ene... Read More about N-body simulations for extended quintessence models.

N-body simulations for f(R) gravity using a self-adaptive particle-mesh code (2011)
Journal Article
Zhao, G., Li, B., & Koyama, K. (2011). N-body simulations for f(R) gravity using a self-adaptive particle-mesh code. Physical Review D, 83(4), Article 044007. https://doi.org/10.1103/physrevd.83.044007

We perform high-resolution N-body simulations for f(R) gravity based on a self-adaptive particle-mesh code MLAPM. The chameleon mechanism that recovers general relativity on small scales is fully taken into account by self-consistently solving the no... Read More about N-body simulations for f(R) gravity using a self-adaptive particle-mesh code.

N-body simulations for coupled scalar field cosmology (2011)
Journal Article
Li, B., & Barrow, J. (2011). N-body simulations for coupled scalar field cosmology. Physical Review D, 83(2), Article 024007. https://doi.org/10.1103/physrevd.83.024007

We describe in detail the general methodology and numerical implementation of consistent N-body simulations for coupled-scalar-field models, including background cosmology and the generation of initial conditions (with the different couplings to diff... Read More about N-body simulations for coupled scalar field cosmology.