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We discuss the collapsing and expanding solutions of anisotropic charged cylinder in the context of

Gravitational force is amenable for governing many astrophysical phenomena like formation of stars, keeping stars together in galaxies, gravitational collapse, and restricting the heavenly bodies in their respective orbits. A star is in equilibrium state under the balance of pressure (directed outward) and gravity (directed inward). It undergoes collapse if gravity exceeds pressure and experiences expansion when pressure overcomes gravity. During the life, a star experiences both of these phenomena. Oppenheimer and Snyder [

After that, many researchers studied the process of collapse for different configurations. Stark and Piran [

The

Harko

Recent detection of gravitational waves has brought motivation to study the collapse phenomenon with the existence of gravitational waves in the exterior. It is well known by Bhirkoff’s theorem that a spherical symmetric vacuum spacetime cannot have gravitational radiation. In this context, the next assumption is cylindrical system, because Einstein and Rosen found exact solution of the field equations which models the propagation of cylindrical gravitational waves. Sharif and Bhatti [

Rosseland and Eddington [

Glass [

In this section, we first discuss physical goals of the research work presented in this paper and then elaborate the technique to achieve these objectives. Here, we would like to explore physical characteristics of a cylindrical star during the phases of collapse and expansion in the dark energy dominated era. When a star starts to loose the hydrostatic equilibrium, firstly, its outer layers expand and it becomes a red-giant. However, after some time, the star suffers a supernova explosion and experiences a collapse. In order to discuss the whole scenario in an expanding universe, we consider

For this purpose, we generate collapsing and expanding solutions for our cylindrically symmetric model. We then analyze the physical parameters graphically such that the density and mass remain positive. Also, the obtained values of density and pressures must satisfy the energy conditions for the viability of the solution; otherwise there is a possibility of existence of exotic fluid that is an unrealistic situation. The value of curvature-matter coupling constant is taken such that our model

The

The Maxwell equations are given by

A simultaneous solution of the field equations gives the following explicit expressions of density and pressure components:

For collapsing solution, we find the unknown metric function

For the sake of simplicity, we consider

For the collapsing case, the graphical representation of different parameters is given in Figures

Change in parameters with respect to

| | | | | | |
---|---|---|---|---|---|---|

| decreases | decreases | increases | decreases | decreases | increases |

Effects of

| | | | | | |
---|---|---|---|---|---|---|

| increases | increases | decreases | decreases | increases | increases |

| ||||||

| increases | increases | increases | increases | increases | no change |

Plot of

Plots of

Plots of

Plots of

Plots of

Plots of

Plot of

To observe physical viability of our solution, we plot the null (NEC), weak (WEC), strong (SEC), and dominant (DEC) energy conditions for the curvature-matter coupled gravity [

NEC:

WEC:

SEC:

DEC:

The term

Plots for NEC for

Plot for WEC for

Plot for SEC for

Plots for DEC for

In this case, we require an expression of the metric coefficient

Change in parameters with respect to

| | | | | | |
---|---|---|---|---|---|---|

| decreases | decreases | increases | increases | decreases | increases |

| ||||||

| decreases | decreases | increases | increases | decreases | increases |

Effects of

| | | | | | |
---|---|---|---|---|---|---|

| increases | increases | decreases | decreases | increases | increases |

| ||||||

| increases | increases | decreases | decreases | increases | no change |

Plot of

Plots of

Plots of

Plots of

Plots of

Plots of

Plot of

The acceleration term

Plots for NEC for

Plot for WEC for

Plot for SEC for

Plots for DEC for

Accelerated expansion of the universe is an observed phenomenon which can affect astrophysical processes. To study the consequences of the expanding universe on collapsing and expanding scenarios of a stellar object, we consider charged anisotropic cylindrical source in

In case of collapse solution, the expansion scalar, density, pressures (

Finally, we compare our results with those found in GR or

No data were used to support this study.

The authors declare that they have no conflicts of interest.

We would like to thank the Higher Education Commission, Islamabad, Pakistan, for its financial support through the