arXiv subjects

Malcolm Anderson

Publications and source records attributed to Malcolm Anderson.

13 recordsLinked to original sources

arXiv2018

Non-Twisting and Twisting Solutions of the Einstein Field Equations of a Skyrmionic String

We construct non-linear sigma model plus Skyrme term (Skyrme model) with a twist in the gravitational field. We try to solve the Einstein field equations for small and large values of $r$, with and without twist. We prove that no non-twisting or twisting solutions extending from $r=0$ to $r=\infty$ exist. At last, we try to solve non-twisting and twisting solutions of the Einstein field equations with a finite radius. We find that there are no solutions with a finite radius that can satisfy the junction conditions at the boundary radius $r=r_b$, where $r_b$ is a finite radius.

gr-qc↗

arXiv2018

Vortex Solution of the Gravitational Field Equation of a Twisted Skyrme Strings

We construct non-linear sigma model plus Skyrme term (Skyrme model) with a twist in the gravitational field. To simplify the solution, first we examine non-linear sigma model without Skyrme term, in particular with a twist, which comprises a vortex solution with an added dependence on a twist term $mkz$, where $z$ is the vertical coordinate. We find that vortex solution for non-linear sigma model with a twist is similar with vortex solution without a twist. The work is still progress.

gr-qc↗

arXiv2018

Vortex Solution of a Twisted Baby Skyrme Equation

We examine non-linear sigma (plus Skyrme term) model in flat space, in particular with a twist, which comprises a twisted baby Skyrmion vortex solution with an added dependence on a twist term $mkz$, where $z$ is the vertical coordinate. We find that the solutions should have asymptotic form. We also find that mass per unit length of string, $\mu$, increases roughly linearly with $\zeta$, where $\zeta=4\lambda^2K_s(mk)^2$, $\lambda$ is scaling constant, $K_s$ is Skyrme term, $m$ is integer and $k$ is wave number.

hep-th↗

arXiv2017

Topological and Hopf charges of a twisted Skyrmion string

We examine nonlinear sigma models, in particular the Skyrme model with a twist (the twisted Skyrmion string), which comprises a vortex solution with an added dependence on a twist term $mkz$, where $z$ is the vertical coordinate. The topological and Hopf charges of a twisted Skyrmion string are calculated and are shown to be equivalent to the winding number $n$ of the vortex and proportional to $nmk$, respectively. The principle of conservation of the Hopf charge, which is a standard property of the baby Skyrmion model, is generalised to cover the non-compact twisting solutions studied here.

hep-th↗

arXiv2016

The Gravitational Field Equations of a Twisted Skyrmion String: Numerical Solution

We study nonlinear sigma model, especially Skyrme model with twist: twisted Skyrmion string where twist term, $mkz$, is indicated in vortex solution. To add gravity, we replace $\eta^{\mu\nu}$ in Lagrangian system with a space-time metric tensor, $g^{\mu\nu}$, which in view of the time-independence and cylindrical symmetry of the assumed vortex solution is taken to be a function of $r$ alone. We use ode45 for numerical calculation, i.e. a tool box in Matlab to solve coupled Einstein field equations which have ordinary differential equations (ODE) form.

gr-qc↗

arXiv2015

Topological and Hopf charges of a twisted Skyrmion string

We study nonlinear sigma model, especially Skyrme model with twist (twisted Skyrmion string) where twist term $mkz$ is indicated in vortex solution. We study topological and Hopf charges of a twisted Skyrmion string. We show that the Hopf charge is exist in our twisting solutions like the twisted Skyrmion string.

math-ph↗

arXiv2015

The Gravitational Field of a Twisted Skyrmion String

In this paper we study the gravitational field of a straight string generated from a class of nonlinear sigma models, specifically the Skyrme model with a twist (the twisted Skyrmion string). The twist term, mkz, is included to stabilize the vortex solution. To model the effects of gravity, we replace the Minkowski tensor, $η^{μν}$, in the standard Skyrme Lagrangian density with a space-time metric tensor, $g^{μν}$, assumed to be static and cylindrically symmetric. The Einstein equations for the metric and field components are then derived. This work is still in progress.

gr-qc↗

arXiv2015

Mathematical modeling of the gravitational field of a twisted Skyrmion string

In this paper we study the gravitational field of a straight string generated from a class of nonlinear sigma models, specifically the Skyrme model without a twist and the Skyrme model with a twist (the twisted Skyrmion string). The twist term, $mkz$, is included to stabilize the vortex solution. To model the effects of gravity, we replace the Minkowski tensor, $η^{μν}$, in the standard Skyrme Lagrangian density with a space-time metric tensor, $g^{μν}$, assumed to be static and cylindrically symmetric. The Einstein equations for the metric and field components are then derived. This work is still in progress.

gr-qc↗

arXiv2014

Twisted Skyrmion String

We study nonlinear sigma model, especially Skyrme model without twist and Skyrme model with twist: twisted Skyrmion string. Twist term, $mkz$, is indicated in vortex solution. Necessary condition for stability of vortex solution has consequence that energy of vortex is minimum and scale-free (vortex solution is neutrally stable to changes in scale). We find numerically that the value of vortex minimum energy per unit length for twisted Skyrmion string is $20.37\times 10^{60}~\text{eV/m}$.

gr-qc↗

arXiv2009

Gravitational waveforms from the evaporating ACO cosmic string loop

The linearly polarized gravitational waveforms from a certain type of rotating, evaporating cosmic string - the Allen-Casper-Ottewill loop - are constructed and plotted over the lifetime of the loop. The formulas for the waveforms are simple and exact, and describe waves which attenuate self-similarly, with the amplitude and period of the waves falling off linearly with time.

gr-qc↗

arXiv2008

Continuous self-similar evaporation of a rotating cosmic string loop

A solution of the linearized Einstein and Nambu-Goto equations is constructed which describes the evaporation of a certain type of rotating cosmic string - the Allen-Casper-Ottewill loop - under the action of its own self-gravity. The solution evaporates self-similarly, and radiates away all its mass-energy and momentum in a finite time. Furthermore, the corresponding weak-field metric can be matched to a remnant Minkowski spacetime at all points on the future light cone of the final evaporation point of the loop.

gr-qc↗

arXiv2005

Self-Similar Evaporation of a Rigidly-Rotating Cosmic String Loop

The gravitational back-reaction on a certain type of rigidly-rotating cosmic string loop, first discovered by Allen, Casper and Ottewill, is studied at the level of the weak-field approximation. The near-field metric perturbations are calculated and used to construct the self-acceleration vector of the loop. Although the acceleration vector is divergent at the two kink points on the loop, its net effect on the trajectory over a single oscillation period turns out to be finite. The net back-reaction on the loop over a single period is calculated using a method due to Quashnock and Spergel, and is shown to induce a uniform shrinkage of the loop while preserving its original shape. The loop therefore evolves by self-similar evaporation.

gr-qc↗

arXiv1997

Effective action and motion of a cosmic string

We examine the leading order corrections to the Nambu effective action for the motion of a cosmic string, which appear at fourth order in the ratio of the width to radius of curvature of the string. We determine the numerical coefficients of these extrinsic curvature corrections, and derive the equations of motion of the worldsheet. Using these equations, we calculate the corrections to the motion of a collapsing loop, a travelling wave, and a helical breather. From the numerical coefficients we have calculated, we discuss whether the string motion can be labelled as `rigid' or `antirigid,' and hence whether cusp or kink formation might be suppressed or enhanced.

hep-ph↗