Twisted Space-times Research Articles

A simple characterization of doubly twisted spacetimes

In this note, we characterize [Formula: see text] doubly twisted spacetimes in terms of “doubly torqued” vector fields. They extend Bang–Yen Chen’s characterization of twisted and generalized Robertson–Walker spacetimes with torqued and concircular vector fields. The result is a simple classification of [Formula: see text] doubly-twisted, doubly-warped, twisted and generalized Robertson–Walker spacetimes.

Characterizations of twisted spacetime

The object of the present paper is to characterize pseudo Ricci symmetric twisted spacetimes. At first it is shown that a pseudo Ricci symmetric twisted spacetime is a GRW spacetime. Next, we obtain a necessary and sufficient condition for a pseudo Ricci symmetric twisted spacetime to be a perfect fluid spacetime. It is also proved that a pseudo Ricci symmetric twisted spacetime is perfect fluid, provided the conformal curvature tensor is divergence free. Moreover, we investigate shear and vorticity vector fields of such type of spacetimes and pointed out its implications towards the evolution of the Early Universe. Finally, we study conformally flat (PRS)n spacetimes.

Some characterizations of Lorentzian manifolds

Generalized Robertson–Walker (GRW) spacetime is the generalization of the Robertson–Walker (RW) spacetime and a further generalization of GRW spacetime is the twisted spacetime. In this paper, we generalize the results of the paper [C. A. Mantica, Y. J. Suh and U. C. De, A note on generalized Robertson–Walker spacetimes, Int. J. Geom. Methods Mod. Phys. 13 (2016), Article Id: 1650079, 9 pp., doi: 101142/s0219887816500791 ]. We prove that a Ricci simple Lorentzian manifold with vanishing quasi-conformal curvature tensor is a RW spacetime. Further, we prove that a Ricci simple Lorentzian manifold with harmonic quasi-conformal curvature tensor is a GRW spacetime. As a consequence, we obtain several corollaries. Finally, we have cited some examples of the obtained results.

Spacetime manipulation of quantum information around rotating black holes

The X-ray photons emitted by the accretion disks around rotating black holes are polarized and acquire orbital angular momentum, two degrees of freedom that can encode quantum information. Nevertheless, escaping the accretion disk, photons are passing throughout the extreme warped and twisted spacetime near spinning black holes suffering rotations of polarization angle and changes in the orbital angular moment. We conjecture that these changes in the angle of polarization and orbital angular momentum can implement elementary quantum gates and simple quantum circuits. Consequently, when detected by an asymptotic observer, the photons emitted near rotating black holes encode quantum information that can be measured by actual quantum information technology.

Twisted space-time reduced model of largeNQCD with two adjoint Wilson fermions

The space-time reduced model of large N QCD with two adjoint Wilson fermions is constructed by applying the symmetric twist boundary conditions with non-vanishing flux $k$. For large but finite $N=L^2$, the model should behave as the large N version of the ordinary lattice gauge model on a $V=L^4$ space-time volume. We perform a comparison of the $N$ dependence of several quantities in this model and in the $k$=0 model (corresponding to periodic boundary conditions). Although the Z$^4$(N) symmetry seems unbroken in all cases, the N-dependence analysis favours the use of the same values of $k$ and $L$ for which the symmetry is also unbroken in the pure gauge case. In particular, the $k=0$ model, studied recently by several authors, shows a large and irregular dependence on $N$ within our region of parameters. This makes this reduced model very impractical for extracting physical information about the large N lattice theory. On the contrary, the model for $N=289=17^2$ and large enough $k$ gives consistent results, even for extended observables as Wilson loops $W(R,T)$ up to $R,T$=8, matching the expected behaviour for the lattice model with a $17^4$ space-time volume.

Twist deformation of l-conformal Galilei Hopf algebra

The six Abelian twist-deformations of l-conformal Galilei Hopf algebra are considered. The corresponding twisted space-times are derived as well.

N-ENLARGED GALILEI HOPF ALGEBRA AND ITS TWIST DEFORMATIONS

The N-enlarged Galilei Hopf algebra is constructed. Its twist deformations are considered and the corresponding twisted spacetimes are derived.