Comment on "Light deflection with torsion effects caused by a spinning cosmic string"

TL;DR

This comment critiques a previous study's use of a line element for a spinning cosmic string with torsion, arguing that it is physically inconsistent due to the dimensional constraints of torsion in (2+1)-dimensions.

Contribution

It clarifies that a (2+1)-dimensional cosmic string cannot possess torsion, challenging the validity of prior work that assumed such a property.

Findings

The line element used in the previous study is physically incorrect.

Torsion cannot exist in (2+1)-dimensional cosmic strings.

The previous model is incompatible with the physics of cosmic dislocations.

Abstract

In this comment, we showed that the line element ("metric'') worked by Jusufi (Eur. Phys. J. C 76: 332, 2016) is incorrect since he worked with a spinning cosmic string with torsion in $(2+1)$-dimensions (and in polar coordinates), which cannot happen. Indeed, as in $(2+1)$-dimensions there are no screw dislocations or screw torsion (a consequence of the absence of the third spatial dimension, i.e., of the $z$-axis), and being a cosmic string with torsion a type of screw dislocation, but of cosmic origin (i.e., are cosmic dislocations), implies that a $(2+1)$-dimensional cosmic string does not have/carry torsion (since $dz=0$). Therefore, the line element worked by Jusufi is physically incoherent/unacceptable and inappropriate for the research/study.