String loops oscillating in the field of Kerr black holes as a possible explanation of twin highfrequency quasiperiodic oscillations observed in microquasars
Abstract
Small oscillations of currentcarrying string loops around stable equilibrium positions corresponding to minima of the effective potential in the equatorial plane of the Kerr black holes are studied using the perturbation method. In the lowest approximation, two uncoupled harmonic oscillators are obtained that govern the radial and vertical oscillations; the higherorder terms determine nonlinear phenomena and transition to chaotic motion through quasiperiodic stages of the oscillatory motion. The radial profiles of frequencies of the radial and vertical harmonic oscillations that are also relevant in the quasiperiodic stages of the oscillatory motion are given, and their properties, independent of the spin of the black holes and the angular momentum and tension of the string loops, are determined. It is shown that the radial profiles differ substantially from those corresponding to the radial and vertical frequencies of the geodetical epicyclic motion; however, they have the same mass scaling and their magnitude is of the same order. Therefore, we are able to demonstrate that, assuming the relevance of resonant phenomena of radial and vertical stringloop oscillations at their frequency ratio 3∶2, the oscillatory frequencies of string loops can be related to the frequencies of the twin highfrequency quasiperiodic oscillations (HF QPOs) observed in the microquasars GRS 1915+105, XTE 1550564, GRO 165540. We can conclude that oscillating currentcarrying string loops have to be considered as one of the possible explanations of the HF QPOs occurring in the field of compact objects.
 Publication:

Physical Review D
 Pub Date:
 March 2014
 DOI:
 10.1103/PhysRevD.89.065007
 arXiv:
 arXiv:1403.2748
 Bibcode:
 2014PhRvD..89f5007S
 Keywords:

 11.27.+d;
 04.70.s;
 Extended classical solutions;
 cosmic strings domain walls texture;
 Physics of black holes;
 Astrophysics  High Energy Astrophysical Phenomena;
 General Relativity and Quantum Cosmology
 EPrint:
 19 pages, 13 figures, published in PRD. arXiv admin note: text overlap with arXiv:1309.7357