121,799 research outputs found
Probing the X-ray Variability of X-ray Binaries
Kilohertz quasi-periodic oscillations (kHz QPOs) has been regarded as
representing the Keplerian frequency at the inner disk edge in the neutron star
X-ray binaries. The so-called ``parallel tracks'' on the plot of the kHz QPO
frequency vs. X-ray flux in neutron star X-ray binaries, on the other hand,
show the correlation between the kHz QPO frequency and the X-ray flux on time
scales from hours to days. This is suspected as caused by the variations of the
mass accretion rate through the accretion disk surrounding the neutron star. We
show here that by comparing the correlation between the kHz QPO frequency and
the X-ray count rate on a certain QPO time scale observed approximately
simultaneous in the Fourier power spectra of the X-ray light curve, we have
found evidences that the X-ray flux of millihertz QPOs in neutron star X-ray
binaries is generated inside the inner disk edge if adopting that the kilohertz
QPO frequency is an orbital frequency at the inner disk edge. This approach
could be applied to other variability components in X-ray binaries.Comment: 4 pages including 1 figure, To appear in "High Energy Processes and
Phenomena in Astrophysics, IAU Symposium 214", X. Li, Z. Wang, V. Trimble
(eds
Fingerprint of dynamical charge/spin correlations in the tunneling spectra of colossal magnetoresistive manganites
We present temperature-dependent scanning tunneling spectroscopy measurements
on () films with different degrees of biaxial
strain. A depletion in normalized conductance around the Fermi level is
observed both above and below the insulator-to-metal transition temperature
, for weakly as well as highly-strained films. This pseudogap-like
depletion globally narrows on cooling. The zero-bias conductance decreases on
cooling in the insulating phase, reaches a minimum close to and
increases on cooling in the metallic phase, following the trend of macroscopic
conductivity. These results support a recently proposed scenario in which
dynamical short-range antiferromagnetic/charge order correlations play a
preeminent role in the transport properties of colossal magnetoresistive
manganites [R. Yu \textit{et al}., Phys. Rev. B \textbf{77}, 214434 (2008)].Comment: 9 pages, 4 figure
On generalized trigonometric functions and series of rational functions
Here we introduce a way to construct generalized trigonometric functions
associated with any complex polynomials, and the well known trigonometric
functions can be seen to associate with polynomial . We will show that
those generalized trigonometric functions have algebraic identities which
generalizes the well known . One application of the
generalized trigonometric functions is evaluating infinite series of rational
functions.Comment: 14 page
On hyperbolic systems with time dependent H\"older characteristics
In this paper we study the well-posedness of weakly hyperbolic systems with
time dependent coefficients. We assume that the eigenvalues are low regular, in
the sense that they are H\"older with respect to . In the past these kind of
systems have been investigated by Yuzawa \cite{Yu:05} and Kajitani \cite{KY:06}
by employing semigroup techniques (Tanabe-Sobolevski method). Here, under a
certain uniform property of the eigenvalues, we improve the Gevrey
well-posedness result of \cite{Yu:05} and we obtain well-posedness in spaces of
ultradistributions as well. Our main idea is a reduction of the system to block
Sylvester form and then the formulation of suitable energy estimates inspired
by the treatment of scalar equations in \cite{GR:11
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