19,597 research outputs found
Noise In Nonohmic Regimes Of Disordered Systems
We present here a short review of mainly experimental properties of noise as
disordered systems are driven into non-ohmic regimes by applying voltages of
few volts only. It is found that the noise does not simply follow the
resistance in that the direction of change of noise could be opposite to that
of resistance. It is discussed how this and other properties make the noise a
complementary and incisive tool for studying complex systems, particularly its
dynamic properties. Study of noise in non-ohmic regimes in physical systems is
rather in a nascent stage. Some of the open issues are highlighted.Comment: 9 Pages, 7 figures. Reported in Unsolved Problems of Noise and
Fluctuations: UPoN 2005, Gallipoli, Italy, June 6-10, 200
Variations in the Cyclotron Resonant Scattering Features during 2011 outburst of 4U 0115+63
We study the variations in the Cyclotron Resonant Scattering Feature (CRSF)
during 2011 outburst of the high mass X-ray binary 4U 0115+63 using
observations performed with Suzaku, RXTE, Swift and INTEGRAL satellites. The
wide-band spectral data with low energy coverage allowed us to characterize the
broadband continuum and detect the CRSFs. We find that the broadband continuum
is adequately described by a combination of a low temperature (kT ~ 0.8 keV)
blackbody and a power-law with high energy cutoff (Ecut ~ 5.4 keV) without the
need for a broad Gaussian at ~ 10 keV as used in some earlier studies. Though
winds from the companion can affect the emission from the neutron star at low
energies (< 3 keV), the blackbody component shows a significant presence in our
continuum model. We report evidence for the possible presence of two
independent sets of CRSFs with fundamentals at ~ 11 keV and ~ 15 keV. These two
sets of CRSFs could arise from spatially distinct emitting regions. We also
find evidence for variations in the line equivalent widths, with the 11 keV
CRSF weakening and the 15 keV line strengthening with decreasing luminosity.
Finally, we propose that the reason for the earlier observed anti-correlation
of line energy with luminosity could be due to modelling of these two
independent line sets (~ 11 keV and ~ 15 keV) as a single CRSF.Comment: 12 pages, 8 figures (4 in colour), 6 tables. Accepted for publication
in MNRAS. Typos corrected, Figure 8 changed and some changes to draf
Kinematical Analogy for Marginal Dyon Decay
We describe a kinematical analogy for the marginal decay of 1/4-BPS dyons in
4-dimensional N=4 string compactifications. In this analogy, the electric and
magnetic charges play the role of spatial momenta, the BPS mass plays the role
of energy, and 1/2-BPS dyons correspond to massless particles. Using SO(12,1)
"Lorentz" invariance and standard kinematical formulae in particle physics, we
provide simple derivations of the curves of marginal stability. We also show
how these curves map into the momentum ellipsoid, and propose some applications
of this analogy.Comment: 10 pages, minor revision
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