64,093 research outputs found
Universality and correlations in individuals wandering through an online extremist space
The 'out of the blue' nature of recent terror attacks and the diversity of
apparent motives, highlight the importance of understanding the online
trajectories that individuals follow prior to developing high levels of
extremist support. Here we show that the physics of stochastic walks, with and
without temporal correlation, provides a unifying description of these online
trajectories. Our unique dataset comprising all users of a global social media
site, reveals universal characteristics in individuals' online lifetimes. Our
accompanying theory generates analytical and numerical solutions that describe
the characteristics shown by individuals that go on to develop high levels of
extremist support, and those that do not. The existence of these temporal and
also many-body correlations suggests that existing physics machinery can be
used to quantify and perhaps mitigate the risk of future events
The correlations between the twin kHz QPO frequencies of LMXBs
We analyzed the recently published kHz QPO data in the neutron star low-mass
X-ray binaries (LMXBs), in order to investigate the different correlations of
the twin peak kilohertz quasi-eriodic oscillations (kHz QPOs) in bright Z
sources and in the less luminous Atoll sources. We find that a power-law
relation \no\sim\nt^{b} between the upper and the lower kHz QPOs with
different indices: 1.5 for the Atoll source 4U 1728-34 and
1.9 for the Z source Sco X-1. The implications of our results for
the theoretical models for kHz QPOs are discussed.Comment: 6 pages, accepted by MNRA
Investigations of the g factors and local structure for orthorhombic Cu^{2+}(1) site in fresh PrBa_{2}Cu_{3}O_{6+x} powders
The electron paramagnetic resonance (EPR) g factors g_x, g_y and g_z of the
orthorhombic Cu^{2+}(1) site in fresh PrBa_{2}Cu_{3}O_{6+x} powders are
theoretically investigated using the perturbation formulas of the g factors for
a 3d^9 ion under orthorhombically elongated octahedra. The local orthorhombic
distortion around the Cu^{2+}(1) site due to the Jahn-Teller effect is
described by the orthorhombic field parameters from the superposition model.
The [CuO6]^{10-} complex is found to experience an axial elongation of about
0.04 {\AA} along c axis and the relative bond length variation of about 0.09
{\AA} along a and b axes of the Jahn-Teller nature. The theoretical results of
the g factors based on the above local structure are in reasonable agreement
with the experimental data.Comment: 6 pages, 1 figur
Logarithmic correction in the deformed model to produce the heavy quark potential and QCD beta function
We stude the \textit{holographic} QCD model which contains a quadratic term and a logarithmic term with an
explicit infrared cut-off in the deformed warp factor.
We investigate the heavy quark potential for three cases, i.e, with only
quadratic correction, with both quadratic and logarithmic corrections and with
only logarithmic correction. We solve the dilaton field and dilation potential
from the Einstein equation, and investigate the corresponding beta function in
the G{\"u}rsoy -Kiritsis-Nitti (GKN) framework. Our studies show that in the
case with only quadratic correction, a negative or the
Andreev-Zakharov model is favored to fit the heavy quark potential and to
produce the QCD beta-function at 2-loop level, however, the dilaton potential
is unbounded in infrared regime. One interesting observing for the case of
positive , or the soft-wall model is that the
corresponding beta-function exists an infrared fixed point. In the case with
only logarithmic correction, the heavy quark Cornell potential can be fitted
very well, the corresponding beta-function agrees with the QCD beta-function at
2-loop level reasonably well, and the dilaton potential is bounded from below
in infrared. At the end, we propose a more compact model which has only
logarithmic correction in the deformed warp factor and has less free
parameters.Comment: 24 pages, 16 figure
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