Rotational evolution of a symmetric gyrostat with visco-elastic bars around the center of mass in a circular orbit

1987 ◽  
Vol 40 (3-4) ◽  
pp. 225-231 ◽  
Author(s):  
Samy Ahmed ◽  
El-Hafiez Aly
2017 ◽  
Vol 14 (07) ◽  
pp. 1750101
Author(s):  
Parthapratim Pradhan

In this work, we study the equatorial causal geodesics of the Taub–NUT (TN) spacetime in comparison with massless TN spacetime. We emphasized both on the null circular geodesics and time-like circular geodesics. From the effective potential diagram of null and time-like geodesics, we differentiate the geodesics structure between TN spacetime and massless TN spacetime. It has been shown that there is a key role of the NUT parameter to changes the shape of pattern of the potential well in the NUT spacetime in comparison with massless NUT spacetime. We compared the innermost stable circular orbit (ISCO), marginally bound circular orbit (MBCO) and circular photon orbit (CPO) of the said spacetime with graphically in comparison with massless cases. Moreover, we compute the radius of ISCO, MBCO and CPO for extreme TN black hole (BH). Interestingly, we show that these three radii coincides with the Killing horizon, i.e. the null geodesic generators of the horizon. Finally in Appendix A, we compute the center-of-mass (CM) energy for TN BH and massless TN BH. We show that in both cases, the CM energy is finite. For extreme NUT BH, we found that the diverging nature of CM energy. First, we have observed that a non-asymptotic flat, spherically symmetric and stationary extreme BH showing such feature.


2020 ◽  
Vol 3 (1) ◽  

A particle of mass nm, carrying the electronic charge -e, revolves in an orbit through angle ψ at distances nr from a center of force of attraction, with angular momenta nL perpendicular to the orbital plane, where n is an integer greater than 0, m the electronic mass and r1 is the radius of the first circular orbit. The equation of motion of the nth orbit of revolution is derived, revealing that an excited particle revolves in an unclosed elliptic orbit, with emission of radiation at the frequency of revolution, before settling down, after many cycles of ψ, in a stable circular orbit. In unipolar revolution, a radiating particle settles in a circular orbit of radius nr1 round a positively charged nucleus. In bipolar revolution, two radiating particles of the same mass nm and charges e and –e, settle in a circular stable orbit of radius ns1 round a common center of mass, where s1 is the radius of the first orbit. Discrete masses nm and angular momenta nL lead to quantization of the orbits outside Bohr’s quantum mechanics. The frequency of radiation in the bipolar revolution is found to be in conformity with the Balmer-Rydberg formula for the spectral lines of radiation from the atom hydrogen gas. There is a spread in frequency of emitted radiation, the frequency in the final circle being the highest, which might explain hydrogen fine structure, as observed with a diffraction grating of high resolution. The unipolar revolution is identified with the solid or liquid state of hydrogen and bipolar revolution with the gas state.


2019 ◽  
Vol 35 (07) ◽  
pp. 2050033 ◽  
Author(s):  
Ujjal Debnath

Here, we consider axially symmetric, stationary, rotating and charged Kerr–Sen Dilaton-Axion black hole as particle accelerator. We find the effective potential and discuss the circular orbit of a particle. We investigate the center of mass energy of two colliding neutral particles with different rest masses falling from rest at infinity to near the non-extremal horizons (event horizon and Cauchy horizon) and extremal horizon of the Kerr–Sen Dilaton-Axion black hole. Analogous to the Compton process, we discuss the collision of a particle and a massless photon. Finally, we find the center of mass energy due to the collision of two photons in the background of Kerr–Sen Dilaton-Axion black hole.


2017 ◽  
Vol 26 (09) ◽  
pp. 1750091 ◽  
Author(s):  
M. Sharif ◽  
Sehrish Iftikhar

This paper explores dynamics of particles in the combined gravitational and electromagnetic fields of the dyonic Reissner–Nordström background. We discuss possibilities for the particle escape to infinity at inner most stable circular orbit. We study the stability of orbit through Lyapunov exponent and the effective force on particle. The collision of particles is investigated through the center of mass energy near the horizon of black hole. Finally, we compare our results with the motion of particles around Schwarzschild and Reissner–Nordström black hole. We conclude that charge of the black hole has a strong effect on the motion of particles.


2016 ◽  
Vol 25 (02) ◽  
pp. 1650024 ◽  
Author(s):  
Gulmina Zaman Babar ◽  
Mubasher Jamil ◽  
Yen-Kheng Lim

We examine the motion of a charged particle in the vicinity of a weakly magnetized naked singularity. The escape velocity and energy of the particle moving around the naked singularity after being kicked by another particle or photon are investigated. Also at innermost stable circular orbit (ISCO) escape velocity and energy are examined. Effective potential and angular momentum of the particle are also discussed. We discuss the center-of-mass energy after collision between two particles having same mass and opposite charges moving along the same circular orbit in the opposite direction. It is investigated that under what conditions maximum energy can be produced as a result of collision.


2017 ◽  
Vol 15 (01) ◽  
pp. 1850011
Author(s):  
Parthapratim Pradhan

We study the existence and stability criteria for circular geodesics of spherically symmetric tidal-charged black hole (BH). We investigate in details the equatorial causal geodesics of the tidal-charged BH in comparison with spherically symmetric Reissner–Nordström BH spacetime. We particularly focused on both the null circular geodesics and time-like circular geodesics. Using the effective potential diagram, we have compared the geodesic structure between two spacetimes. We have derived the ISCO (innermost stable circular orbit), MBCO (marginally bound circular orbit) and CPO (circular photon orbit) for both the spacetimes. Moreover, we have derived the quasi-normal modes[Formula: see text]QNMs[Formula: see text] frequency in the eikonal limit for both the spacetimes via Lyapunov exponent. In the appendix section, we have shown that a spherically symmetric tidal-charged BH can act as particle accelerators with ultra-high center-of-mass (CM) energy in the limiting case of maximal BH tidal-charge[Formula: see text] and it is possible when two neutral particles are colliding near the horizon.


Sign in / Sign up

Export Citation Format

Share Document