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Symmetry 2019, 11(2), 189; https://doi.org/10.3390/sym11020189

Relativistic Neutron Stars: Rheological Type Extensions of the Equations of State

1
Department of General Relativity and Gravitation, Institute of Physics, Kazan Federal University, Kremlevskaya str. 18, 420008 Kazan, Russia
2
Laboratory of Theoretical Physics of Scientific Research Institute of Physics: Faculty of Physics, Yerevan State University, 1 Alex Manoogian, Yerevan 0025, Armenia
3
Institute of Applied Problems in Physics NAS RA, 25 Nersessian Street, Yerevan 0014, Armenia
*
Author to whom correspondence should be addressed.
Received: 3 December 2018 / Revised: 30 January 2019 / Accepted: 1 February 2019 / Published: 8 February 2019
(This article belongs to the Special Issue Symmetry: Anniversary Feature Papers 2018)
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Abstract

Based on the Rheological Paradigm, we extend the equations of state for relativistic spherically symmetric static neutron stars, taking into consideration the derivative of the matter pressure along the so-called director four-vector. The modified equations of state are applied to the model of a zero-temperature neutron condensate. This model includes one new parameter with the dimensionality of length, which describes the rheological type screening inside the neutron star. As an illustration of the new approach, we consider the rheological type generalization of the non-relativistic Lane–Emden theory and find numerically the profiles of the pressure for a number of values of the new guiding parameter. We have found that the rheological type self-interaction makes the neutron star more compact, since the radius of the star, related to the first null of the pressure profile, decreases when the modulus of the rheological type guiding parameter grows. View Full-Text
Keywords: modified gravity; neutron star; equation of state modified gravity; neutron star; equation of state
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Balakin, A.; Ilin, A.; Kotanjyan, A.; Grigoryan, L. Relativistic Neutron Stars: Rheological Type Extensions of the Equations of State. Symmetry 2019, 11, 189.

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