Teleparallel Minkowski Spacetime with Perturbative Approach for Teleparallel Gravity on Proper Frame

In this paper, we first develop a complete perturbation theory requiring only the perturbation of the fundamental quantities describing Teleparallel Gravity. We first obtain the physical quantities by perturbing the coframes taking into account the gauge metric and spin-connection conditions. We obtain the perturbed field equations involving these perturbed quantities. We will study some specific cases of perturbations of coframes and finally discuss the stability of the Minkowski background. Our perturbation framework is based on using a proper orthonormal frame throughout, which is possible since we remain with a theory of Teleparallel Gravity.Comment: 33 pages, submitted to a journa

Bianchi type cosmological models in f(T) tele-parallel gravity

Symmetry assumptions on the geometrical framework have provided successful mechanisms to develop physically meaningful solutions to many problems. In tele-parallel gravity, invariance of the frame and spin-connection under a group of motions defines an affine symmetry group. Here, we assume there exists a three-dimensional group of affine symmetries acting simply transitively on a spatial hypersurface and that this group of symmetry actions defines our affine frame symmetry group. We determine the general form of the co-frame and spin connection for each spatially homogeneous Bianchi type. We then construct the corresponding field equations for f(T) tele-parallel gravity. We show that if the symmetry group is of Bianchi type A (I, II, VI0, VII0, VIII or IX) then there exists a co-frame/spin connection pair that is consistent with the antisymmetric part of the field equations of f(T) tele-parallel gravity. For those geometries having a Bianchi type B symmetry group (IV, V, VIh, VIIh), we find that in general these geometries are inconsistent with the antisymmetric part of the f(T) tele-parallel gravity field equations unless the theory reduces to an analog of General Relativity with a cosmological constant

Symmetric teleparallel geometries

In teleparallel gravity and, in particular, in F(T) teleparallel gravity, there is a challenge in determining an appropriate (co-)frame and its corresponding spin connection to describe the geometry. Very often, the ‘proper’ frame, the frame in which all inertial effects are absent, is not the simplest (e.g, diagonal) (co-)frame. The determination of the frame and its corresponding spin connection for F(T) teleparallel gravity theories when there exist affine symmetries is of much interest. In this paper we present the general form of the coframe and its corresponding spin connection for teleparallel geometries which are invariant under a G6 group of affine symmetries. The proper coframe and the corresponding F(T) field equations are also shown for these teleparallel Robertson–Walker geometries. Further, with the addition of an additional affine symmetry, it is possible to define a teleparallel de Sitter geometry.publishedVersio

Observational Cosmology in Macroscopic Gravity

We discuss the construction of cosmological models within the framework of Macroscopic Gravity (MG), which is a theory that models the effects of averaging the geometry of space-time on large scales. We find new exact spatially homogeneous and isotropic FLRW solutions to the MG field equations, and investigate large-scale perturbations around them. We find that any inhomogeneous perturbations to the averaged geometry are severely restricted, but that possible anisotropies in the correlation tensor can have dramatic consequences for the measurement of distances. These calculations are a first step within the MG approach toward developing averaged cosmological models to a point where they can be used to interpret real cosmological data, and hence to provide a working alternative to the "concordance" LCDM model.Comment: 22 page

Generalized Teleparallel de Sitter geometries

Theories of gravity based on teleparallel geometries are characterized by the torsion, which is a function of the coframe, derivatives of the coframe, and a zero curvature and metric compatible spin connection. The appropriate notion of a symmetry in a teleparallel geometry is that of an affine symmetry. Due to the importance of the de Sitter geometry and Einstein spaces within general relativity, we shall describe teleparallel de Sitter geometries and discuss their possible generalizations. In particular, we shall analyse a class of Einstein teleparallel geometries which have a 4-dimensional Lie algebra of affine symmetries, and display two one-parameter families of explicit exact solutions.Comment: 25 pages, no figure, Submitted to EPJ

The shape of the iceberg: quantification of submicroscopic Plasmodium falciparum and Plasmodium vivax parasitaemia and gametocytaemia in five low endemic settings in Ethiopia.

BACKGROUND: The widespread presence of low-density asymptomatic infections with concurrent gametocytes may be a stumbling block for malaria elimination. This study investigated the asymptomatic reservoir of Plasmodium falciparum and Plasmodium vivax infections in schoolchildren from five settings in northwest Ethiopia. METHODS: Two cross-sectional surveys were conducted in June and November 2015, enrolling 551 students from five schools and 294 students from three schools, respectively. Finger prick whole blood and plasma samples were collected. The prevalence and density of P. falciparum and P. vivax parasitaemia and gametocytaemia were determined by 18S rRNA quantitative PCR (qPCR) and pfs25 and pvs25 reverse transcriptase qPCR. Antibodies against blood stage antigens apical membrane antigen-1 (AMA-1) and merozoite surface protein-1 (MSP-119) were measured for both species. RESULTS: Whilst only 6 infections were detected by microscopy in 881 slides (0.7%), 107 of 845 blood samples (12.7%) were parasite positive by (DNA-based) qPCR. qPCR parasite prevalence between sites and surveys ranged from 3.8 to 19.0% for P. falciparum and 0.0 to 9.0% for P. vivax. The median density of P. falciparum infections (n = 85) was 24.4 parasites/µL (IQR 18.0-34.0) and the median density of P. vivax infections (n = 28) was 16.4 parasites/µL (IQR 8.8-55.1). Gametocyte densities by (mRNA-based) qRT-PCR were strongly associated with total parasite densities for both P. falciparum (correlation coefficient = 0.83, p = 0.010) and P. vivax (correlation coefficient = 0.58, p = 0.010). Antibody titers against P. falciparum AMA-1 and MSP-119 were higher in individuals who were P. falciparum parasite positive in both surveys (p < 0.001 for both comparisons). DISCUSSION: This study adds to the available evidence on the wide-scale presence of submicroscopic parasitaemia by quantifying submicroscopic parasite densities and concurrent gametocyte densities. There was considerable heterogeneity in the occurrence of P. falciparum and P. vivax infections and serological markers of parasite exposure between the examined low endemic settings in Ethiopia