Related Experiment Video
Updated: Jun 11, 2026
11:34
Scattering And Absorption of Light in Planetary Regoliths
Published on: July 1, 2019
Stochastic analysis of compact stars under composite polytropes
Mohamed I Nouh1, Samah H El-Essawy1, Mona M Foda2
1Astronomy Department, National Research Institute of Astronomy and Geophysics, Helwan, Cairo, 11421, Egypt.
Scientific Reports
|June 9, 2026
Summary
We introduce a composite relativistic polytropic model to accurately describe neutron star interiors. This new model successfully reproduces observed neutron star masses and radii, offering a flexible framework for dense matter studies.
Area of Science:
- Astrophysics and nuclear physics
- Study of dense matter and compact stars
- Gravitational physics
Background:
- Neutron stars are crucial for understanding extreme density and gravity.
- Single polytropic models fail to capture the complex internal structure of compact stars.
- Realistic compact-star interiors exhibit stratified, layered matter.
Purpose of the Study:
- To develop a more accurate model for compact-star interiors.
- To investigate the impact of a radially varying polytropic index.
- To constrain the equation of state for dense matter.
Main Methods:
- Developed a composite relativistic polytropic model.
- Coupled Einstein field equations with a generalized composite polytropic equation of state.
- Solved the composite Tolman-Oppenheimer-Volkoff (CTOV) system using Monte Carlo integration.
- Quantified parameter space uncertainty.
Main Results:
- Composite models accurately reproduce neutron star mass-radius relations, including diverse observed systems.
- Increasing relativistic parameters leads to more compact stellar configurations.
- Sharper core-envelope transitions result in higher compactness.
- Maximum mass estimations align with observational constraints.
Conclusions:
- Composite polytropes offer a flexible and physically motivated framework for modeling stratified compact stars.
- This approach enhances our ability to constrain the dense-matter equation of state.
- The model provides a robust tool for astrophysical simulations and observations.
Related Concept Videos
01:12Reduced Mass Coordinates: Isolated Two-body Problem
In classical mechanics, the two-body problem is one of the fundamental problems describing the motion of two interacting bodies under gravity or any other central force. When considering the motion of two bodies, one of the most important concepts is the reduced mass coordinates, a quantity that allows the two-body problem to be solved like a single-body problem. In these circumstances, it is assumed that a single body with reduced mass revolves around another body fixed in a position with an...
01:06Divergence and Stokes' Theorems
The divergence and Stokes' theorems are a variation of Green's theorem in a higher dimension. They are also a generalization of the fundamental theorem of calculus. The divergence theorem and Stokes' theorem are in a way similar to each other; The divergence theorem relates to the dot product of a vector, while Stokes' theorem relates to the curl of a vector. Many applications in physics and engineering make use of the divergence and Stokes' theorems, enabling us to write numerous physical laws...
01:24Pole and System Stability
The transfer function is a fundamental concept representing the ratio of two polynomials. The numerator and denominator encapsulate the system's dynamics. The zeros and poles of this transfer function are critical in determining the system's behavior and stability.
Simple poles are unique roots of the denominator polynomial. Each simple pole corresponds to a distinct solution to the system's characteristic equation, typically resulting in exponential decay terms in the system's response.
Simple poles are unique roots of the denominator polynomial. Each simple pole corresponds to a distinct solution to the system's characteristic equation, typically resulting in exponential decay terms in the system's response.
01:18Second Order systems II
In an underdamped second-order system, where the damping ratio ζ is between 0 and 1, a unit-step input results in a transfer function that, when transformed using the inverse Laplace method, reveals the output response. The output exhibits a damped sinusoidal oscillation, and the difference between the input and output is termed the error signal. This error signal also demonstrates damped oscillatory behavior. Eventually, as the system reaches a steady state, the error diminishes to zero.
If ζ...
If ζ...
01:22Compacting Factor test
The compacting factor test is a method used to assess the workability of concrete. It is especially suitable for concrete mixes containing aggregates up to one and a half inches in size. This test involves specialized equipment consisting of two truncated cone-shaped hoppers and a cylinder, all with polished interior surfaces to minimize friction.
The procedure begins by placing concrete into the upper hopper without any compaction. Once filled, the bottom door of this hopper is opened,...
The procedure begins by placing concrete into the upper hopper without any compaction. Once filled, the bottom door of this hopper is opened,...
01:25Poisson's And Laplace's Equation
The electric potential of the system can be calculated by relating it to the electric charge densities that give rise to the electric potential. The differential form of Gauss's law expresses the electric field's divergence in terms of the electric charge density.