Induced gravity for nonzero torsion

Quantum fluctuations of a spin one-half particle in a gravitational background field with nonvanishing torsion are shown to induce again the Einstein-Hilbert term as a long wavelength effective action so that torsion disappears at the classical tree level.     

S-duality in 3D gravity with torsion

The deformation of the connection in three spacetime dimensions by the kinematically equivalent coframe is shown to induce a duality between the (Lorentz-) rotational and translational field momenta, for which the coupling to the deformation parameter is inverted. This new kind of strong/weak duality, pertinent to 3D, is instrumental for studying exact solutions of the 3D Poincaré gauge field equations and the particle content of propagating modes on a background of constant curvature. For a topological Chern-Simons model of gravity, the propagating modes ‘living’ on an Anti-de Sitter (AdS) background correspond to real massive particles. Yang-Mills type generalizations and new cubic Lagrangians are found and completely classified in 3D. AdS or black hole type solutions with constant axial torsion emerge, also for these higher-order Lagrangians with new ‘exotic’ torsion-curvature couplings. Their pattern complies with our S-duality, with new repercussions for the field redefinition of the metric in 3D quantum gravity and the cosmological constant problem.     

A non-diagonal singularity-free model in torsion gravity

In the context of torsion (teleparallel) gravity, we focus on discussing the spin effects of Dirac particles associated with the non-diagonal singularity-free model (Mars space-time). We see that the vector part depends on the radial r and z directions and the axial-vector will be along the radial direction, that is, it will be symmetric about radial direction. Furthermore, the t = 0 case of the Mars metric is considered, thence it is seen that the axial-vector vanishes.     

One-loop divergences of linear gravity with torsion terms

We investigate the role of the torsion field at the quantum level. One-loop counterterms are calculated in the theory with terms quadratic in the torsion field. We have shown that the theory is finite at the one-loop level.     

Tetrad formulation of gravity with a torsion potential

A tetrad formulation of gravity with a torsion potential is presented. The torsion is derived from the exterior derivative of a second rank tensor potential. The geometrical Lagrangian is the curvature scalar and variations are taken with respect to the tetrad components. It is shown that the resulting field equations, and conservation laws, are identical to those obtained in a purely holonomic frame.     

A geometrical interpretation of parity violation in gravity with torsion

In a space-time with torsion, the action for the gravitational field can be extended with a parity-violating piece. We show how to obtain such a piece from geometry itself, by suitably modifying the affine connection so as to include a pseudo-tensorial part. The merit of such an approach is that it provides one with a consistent method for incorporating parity-violation in the Lagrangians for matter fields with arbitrary spin in a space-time background with torsion.     

Strong gravity with torsion and the Cabibbo angle

The classical field equations of the strong gravity theory are modified by introducing spin and torsion so as to resemble the field equations of the Einstein-Cartan theory. The effects of the hadronic spin upon the strong metric are evaluated using a semiclassical approximation, and it is pointed out that the torsion contributions are not negligible. A possible interpretation of the Cabibbo angle as a strong gravity correction of the weak semileptonic Lagrangian is suggested.     

Nonmetricity and torsion induced by dilaton gravity in two dimension

We develop a theory in which there are couplings amongst Dirac spinor, dilaton and non-Riemannian gravity and explore the nature of connection-induced dilaton couplings to gravity and Dirac spinor when the theory is reformulated in terms of the Levi-Civita connection. After presenting some exact solutions without spinors, we investigate the minimal spinor couplings to the model and in conclusion we cannot find any nontrivial dilaton couplings to spinor.     

Quantum gravity effect in torsion driven inflation and CP violation

Journal of High Energy Physics - In this paper we study the production of a heavy charged Higgs boson in association with heavy quarks at the LHC in the two-Higgs-doublet model. We present for the...     

Instanton and eigenmodes in a two-dimensional theory of gravity with torsion

Instanton-like solutions characterizing the geometric structure of the manifold are found to be in a two-dimensional theory of gravity with dynamical metric and torsion in the context of string theory. The eigenmodes for fluctuations of the solutions of the equations are also investigated and it has been shown that these solutions are stable.     

Cosmological solutions of a quadratic theory of gravity with torsion

Following the general approach of Hehl, and Hayashi and Shirafuji, we give the gravity equations for the lagrangian $\text{L}\text{=(}\text{e}\text{/2L}{}^2\text{)(F+}\text{1}\text{2}\text{×F}{}^2\text{) +}\text{L}{}_{\mathrm{M}}$. We have found the explicit Einstein-de Sitter solutions for a spinless dust. We have discussed in this case the singularity problem for the metric and for the torsion.     

Post-Newtonian generation of gravitational waves in a theory of gravity with torsion

We adapt the post-Newtonian gravitational-radiation methods developed within general relativity by Epstein and Wagoner to the gravitation theory with torsion, recently proposed by Hehl et al., and show that the two theories predict in this approximation the same gravitational radiation losses. Since they agree also on the first post-Newtonian level, they are at the present time-observationally-indistinguishable.     

Fermions in a two-dimensional theory of gravity with dynamical metric and torsion

We propose a new model which reduces a two-dimensional gravitational model with dynamical metric and torsion in a conformal gauge. We also find the instanton-like solutions and discuss their symmetry properties and eigenmodes.This work was partially supported by TBTAK, the Scientific and Technical Research Council of Turkey.     

Exact static vacuum solution of four-dimensional metric-affine gravity with nontrivial torsion

We present an exact spherically symmetric vacuum solution for a metric-affine quadratic Lagrangian. The metric part of the solution is of Reissner-Nordström type. The connection part includes nonmetricity depending on a dilatation charge and a shear charge. Furthermore, a nontrivial torsion depending on a certain torsion mass and with intrinsic contributions is present.     

Exact solution of Poincaré gauge field equations of gravity with torsion

Under empty, static, and spherically symmetric conditions we find an exact metric solution of the Poincaré gauge field equations. The Schwarzschild metric solution is contained in the solution and we also obtain new gauge correction termsr ^–1 andr ² lnr.