9,095 research outputs found
Exotic orbits due to spin-spin coupling around Kerr black holes
We report exotic orbital phenomena of spinning test particles orbiting around
a Kerr black hole, i.e., some orbits of spinning particles are asymmetrical
about the equatorial plane. When a nonspinning test particle orbits around a
Kerr black hole in a strong field region, due to relativistic orbital
precessions, the pattern of trajectories is symmetrical about the equatorial
plane of the Kerr black hole. However, the patterns of the spinning particles'
orbit are no longer symmetrical about the equatorial plane for some orbital
configurations and large spins. We argue that these asymmetrical patterns come
from the spin-spin interactions between spinning particles and Kerr black
holes, because the directions of spin-spin forces can be arbitrary, and
distribute asymmetrically about the equatorial plane.Comment: 15 pages, 20 figure
Transition of stoichiometricSr2VO3FeAs to a superconducting state at 37.2 K
The superconductor Sr4V2O6Fe2As2 with transition temperature at 37.2 K has
been fabricated. It has a layered structure with the space group of p4/nmm, and
with the lattice constants a = 3.9296Aand c = 15.6732A. The observed large
diamagnetization signal and zero-resistance demonstrated the bulk
superconductivity. The broadening of resistive transition was measured under
different magnetic fields leading to the discovery of a rather high upper
critical field. The results also suggest a large vortex liquid region which
reflects high anisotropy of the system. The Hall effect measurements revealed
dominantly electron-like charge carriers in this material. The
superconductivity in the present system may be induced by oxygen deficiency or
the multiple valence states of vanadium.Comment: 5 pages, 4 figure
Superconductivity at 15.6 K in Calcium-doped Tb_{1-x}Ca_xFeAsO: the structure requirement for achieving superconductivity in the hole-doped 1111 phase
Superconductivity at about 15.6 K was achieved in Tb_{1-x}Ca_xFeAsO by
partially substituting Tb^{3+} with Ca^{2+} in the nominal doping region x =
0.40 \sim 0.50. A detailed investigation was carried out in a typical sample
with doping level of x = 0.44. The upper critical field of this sample was
estimated to be 77 Tesla from the magnetic field dependent resistivity data.
The domination of hole-like charge carriers in the low-temperature region was
confirmed by Hall effect measurements. The comparison between the calcium-doped
sample Pr_{1-x}Ca_xFeAsO (non-superconductive) and the Strontium-doped sample
Pr_{1-x}Sr_xFeAsO (superconductive) suggests that a lager ion radius of the
doped alkaline-earth element compared with that of the rare-earth element may
be a necessary requirement for achieving superconductivity in the hole-doped
1111 phase.Comment: 7 pages, 7 figure
Tests of no-hair theorem with binary black-hole coalescences
Test of the no-hair theorem is the primary target with gravitational waves
from binary black holes. In this Letter, we analyze gravitational-wave data
from the LIGO-Virgo-KAGRA detection of binary black-hole mergers using the
PSI_FD model, which is a non-general relativity full waveform template for
arbitrary axisymmetric black holes. By analyzing two high signal-noise-ratio
events, GW150914 and GW200129, the no-hair theorem is tested at a significance
level of 95%, which is the best constraint until now. Especially, we find a
significant deviation from the Kerr black hole in GW200129. More events and
further analysis are needed to validate this deviation.Comment: 5 pages, 4 figures and 1 tabl
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