scholarly journals Spontaneous and gravitational baryogenesis

2018 ◽  
Vol 33 (31) ◽  
pp. 1844023 ◽  
Author(s):  
E. V. Arbuzova
Keyword(s):  
Equations Of Motion ◽  
Curvature Scalar ◽  
Strong Instability ◽  
Standard Cosmology ◽  
Dependent Term ◽  
Gravitational Equations

Some problems of spontaneous and gravitational baryogenesis are discussed. Gravity modification due to the curvature-dependent term in gravitational baryogenesis scenario is considered. It is shown that the interaction of baryonic fields with the curvature scalar leads to strong instability of the gravitational equations of motion and as a result to noticeable distortion of the standard cosmology.

A Comparison of the Effects of Nonlinear Damping on the Free Vibration of a Single-Degree-of-Freedom System

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Bin Tang ◽  
M. J. Brennan
Keyword(s):  
Free Vibration ◽  
Equations Of Motion ◽  
Nonlinear Damping ◽  
Degree Of Freedom ◽  
Damping Force ◽  
Single Degree Of Freedom ◽  
Sdof System ◽  
Single Degree ◽  
Dependent Term ◽  
Quadratic Damping

This article concerns the free vibration of a single-degree-of-freedom (SDOF) system with three types of nonlinear damping. One system considered is where the spring and the damper are connected to the mass so that they are orthogonal, and the vibration is in the direction of the spring. It is shown that, provided the displacement is small, this system behaves in a similar way to the conventional SDOF system with cubic damping, in which the spring and the damper are connected so they act in the same direction. For completeness, these systems are compared with a conventional SDOF system with quadratic damping. By transforming all the equations of motion of the systems so that the damping force is proportional to the product of a displacement dependent term and velocity, then all the systems can be directly compared. It is seen that the system with cubic damping is worse than that with quadratic damping for the attenuation of free vibration.

Galileon inflation field with three dark eras of the universe

2020 ◽  
Vol 29 (10) ◽  
pp. 2050071
Author(s):  
A. I. Keskin
Keyword(s):  
Equations Of Motion ◽  
Vacuum State ◽  
Kinetic Term ◽  
Second Phase ◽  
De Sitter ◽  
Third Phase ◽  
Standard Cosmology ◽  
Slow Roll ◽  
Friction Term ◽  
The Universe

In this paper, we discuss possible three early eras of the universe in the theoretical context of the Galilean cosmology. The first phase is a slow-roll inflation phase in which the friction term in the equations of motion dominates over the kinetic term. This is the initial vacuum state leading to quasi-de Sitter expansion. The second phase is where the cosmological perturbations are supposed to be generated. In this phase, the friction term is supposed to be negligible which leads to the appearance of the Galileon inflation field. The third phase is the reheating phase in the standard cosmology, where the oscillations of a canonical scalar field in the model lead to this phase. These three eras for the early universe are shown by a single master equation of the theory. However, we compute observational indices (the scalar spectral index parameter and the tensor-to-scalar ratio) for the era where the era that the perturbations are produced. Finally, we compare viability of the theoretical findings with the latest Planck observational data.

Gravitational equations of motion at the string scale

1988 ◽  
Vol 215 (2) ◽  
pp. 265-272 ◽  
Author(s):  
Sunil Kalara ◽  
Costas Kounnas ◽  
Keith A. Olive
Keyword(s):  
Equations Of Motion ◽  
Gravitational Equations

Particle production in modified gravity in the early and present day universe

2020 ◽  
Vol 35 (36) ◽  
pp. 2044027
Author(s):  
E. V. Arbuzova
Keyword(s):  
Dark Matter ◽  
Energy Spectrum ◽  
Cosmic Rays ◽  
Modified Gravity ◽  
Particle Production ◽  
Equations Of Motion ◽  
Modified Theories Of Gravity ◽  
Oscillating Solutions ◽  
Theories Of Gravity ◽  
Gravitational Equations

Gravitational equations of motion in modified theories of gravity have oscillating solutions, both in the early and in the present day universe. Particle production by such oscillations is analyzed and possible observational consequences are considered. This phenomenon has impact on energy spectrum of cosmic rays and abundance of dark matter particles.

scholarly journals Testing alternate gravitational theories

2009 ◽  
Vol 5 (S261) ◽  
pp. 179-182 ◽  
Author(s):  
E. M. Standish
Keyword(s):  
Equations Of Motion ◽  
The Sun ◽  
Constant Acceleration ◽  
Gravitational Theories ◽  
Pioneer Anomaly ◽  
The Future ◽  
Gravitational Equations

AbstractThe planetary ephemerides are used to examine different suggested forms of the gravitational equations of motion which could possibly cause the observed Pioneer Anomaly. It is shown that most of the forms would be unacceptable, including that generally assumed – a constant acceleration directed toward the Sun. The tests show that three other forms could not exist within 10 au's of the Sun. Only one suggested form would be compatible with the Pioneer Anomaly affecting Saturn or any other more inward planet. Additional planetary observations in the future may possibly eliminate this form also.

scholarly journals On the cosmological solutions in Weyl geometry

2021 ◽  
Vol 2021 (11) ◽  
pp. 053
Author(s):  
V.A. Berezin ◽  
V.I. Dokuchaev ◽  
Yu. N. Eroshenko ◽  
A.L. Smirnov
Keyword(s):  
Equations Of Motion ◽  
Consistency Condition ◽  
Conformal Factor ◽  
Cosmological Term ◽  
The Self ◽  
Curvature Scalar ◽  
Weyl Geometry ◽  
Cosmological Solutions ◽  
Complete Set ◽  
Self Consistency

Abstract We investigated the possibility of construction the homogeneous and isotropic cosmological solutions in Weyl geometry. We derived the self-consistency condition which ensures the conformal invariance of the complete set of equations of motion. There is the special gauge in choosing the conformal factor when the Weyl vector equals zero. In this gauge we found new vacuum cosmological solutions absent in General Relativity. Also, we found new solution in Weyl geometry for the radiation dominated universe with the cosmological term, corresponding to the constant curvature scalar in our special gauge. Possible relation of our results to the understanding both dark matter and dark energy is discussed.

scholarly journals Cosmological viscous fluid models describing infinite time singularities in f(T) gravity

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
R. D. Boko ◽  
M. J. S. Houndjo
Keyword(s):  
Dark Energy ◽  
Equations Of Motion ◽  
State Parameter ◽  
Infinite Time ◽  
Constant Deceleration Parameter ◽  
Two Fluids ◽  
Viscosity Models ◽  
Time Singularities ◽  
Analytic Expressions ◽  
Gravitational Equations

AbstractIn this paper we explore the state parameter behaviour of the interacting viscous dark energy in f(T) gravity. Using constant deceleration parameter we investigate the cosmological implications of the viscosity and interaction between the dark components (energy and matter) in terms of Redshift. So doing, the viscosity and the interaction between the two fluids are parameterized by constants $$\delta $$ δ and $$\xi $$ ξ respectively. In the later part of the paper, we explore some bulk viscosity models describing Little Rip and Pseudo Rip future singularities within f(T) modified gravity. We obtain gravitational equations of motion for viscous dark energy coupled with dark matter. Solving these equations, we found analytic expressions for characteristic properties of these cosmological models.

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