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Generalizations of teleparallel gravity and local Lorentz symmetry
Thomas P. Sotiriou, Baojiu Li, John D. Barrow
We analyze the relation between teleparallelism and local Lorentz invariance. We show that generic modifications of the teleparallel equivalent to general relativity will not respe…
On the Effects of Coupled Scalar Fields on Structure Formation
Baojiu Li, John D. Barrow
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…
A Testable Solution of the Cosmological Constant and Coincidence Problems
Douglas J. Shaw, John D. Barrow
We present a new solution to the cosmological constant (CC) and coincidence problems in which the observed value of the CC, , is linked to other observable properties of the uni…
f(T) Gravity and local Lorentz invariance
Baojiu Li, Thomas P. Sotiriou, John D. Barrow
We show that in theories of generalised teleparallel gravity, whose Lagrangians are algebraic functions of the usual teleparallel Lagrangian, the action and the field equations are…
N-body Simulations for Extended Quintessence Models
Baojiu Li, David F. Mota, John D. Barrow
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…
Varying alpha from N-body Simulations
Baojiu Li, David F. Mota, John D. Barrow
We have studied the Bekenstein-Sandvik-Barrow-Magueijo (BSBM) model for the spatial and temporal variations of the fine structure constant, alpha, with the aid of full N-body simul…
A New Solution of The Cosmological Constant Problems
John D. Barrow, Douglas J. Shaw
We extend the usual gravitational action principle by promoting the bare cosmological constant (CC) from a parameter to a field which can take many possible values. Variation leads…
N-Body Simulations for Coupled Scalar Field Cosmology
Baojiu Li, John D. Barrow
We describe in detail the general methodology and numerical implementation of consistent N-body simulations for coupled scalar field cosmological models, including the background c…
Anisotropic Pressures at Ultra-stiff Singularities and the Stability of Cyclic Universes
John D Barrow, Kei Yamamoto
We show that the inclusion of simple anisotropic pressures stops the isotropic Friedmann universe being a stable attractor as an initial or final singularity is approached when pre…
A General Sudden Cosmological Singularity
J. D. Barrow, S. Cotsakis, A. Tsokaros
We construct an asymptotic series for a general solution of the Einstein equations near a sudden singularity. The solution is quasi isotropic and contains nine independent arbitrar…
The Construction of Sudden Cosmological Singularities
John D. Barrow, S. Cotsakis, A. Tsokaros
Solutions of the Friedmann-Lemaitre cosmological equations of general relativity have been found with finite-time singularities that are everywhere regular, have regular Hubble exp…
Varying Constants: Constraints from Seasonal Variations
Douglas J. Shaw, John D. Barrow
We analyse the constraints obtained from new atomic clock data on the possible time variation of the fine structure `constant' and the electron-proton mass ratio and show how they…
Observational Constraints on the Completeness of Space near Astrophysical Objects
Timothy Clifton, John D. Barrow
We consider the observational effects of a deficit angle, w, in the topology of the solar system and in the 'double pulsar' system PSR J0737-3039A/B. Using observations of the peri…