44,193 research outputs found
Glassy Dynamics in a Frustrated Spin System: Role of Defects
In an effort to understand the glass transition, the kinetics of a spin model
with frustration but no quenched randomness has been analyzed. The
phenomenology of the spin model is remarkably similiar to that of structural
glasses. Analysis of the model suggests that defects play a major role in
dictating the dynamics as the glass transition is approached.Comment: 9 pages, 5 figures, accepted in J. Phys.: Condensed Matter,
proceedings of the Trieste workshop on "Unifying Concepts in Glass Physics
Enhanced charge stripe order of superconducting La(2-x)Ba(x)CuO(4) in a magnetic field
The effect of a magnetic field on the charge stripe order in
La(2-x)Ba(x)CuO(4) has been studied by means of high energy (100 keV) x-ray
diffraction for charge carrier concentrations ranging from strongly underdoped
to optimally doped. We find that charge stripe order can be significantly
enhanced by a magnetic field applied along the c-axis, but only at temperatures
and dopings where it coexists with bulk superconductivity at zero field. The
field also increases stripe correlations between the planes, which can result
in an enhanced frustration of the interlayer Josephson coupling. Close to the
famous x=1/8 compound, where zero field stripe order is pronounced and bulk
superconductivity is suppressed, charge stripe order is independent of a
magnetic field. The results imply that static stripe order and
three-dimensionally coherent superconductivity are competing ground states.Comment: 6 pages, 4 figure
Neutrino masses, leptogenesis and dark matter in hybrid seesaw
We suggest a hybrid seesaw model where relatively ``light''right-handed
neutrinos give no contribution to the neutrino mass matrix due to a special
symmetry. This allows their Yukawa couplings to the standard model particles to
be relatively strong, so that the standard model Higgs boson can decay
dominantly to a left and a right-handed neutrino, leaving another stable
right-handed neutrino as cold dark matter. In our model neutrino masses arise
via the type-II seesaw mechanism, the Higgs triplet scalars being also
responsible for the generation of the matter-antimatter asymmetry via the
leptogenesis mechanism.Comment: 4 page
A spatio-temporal entropy-based approach for the analysis of cyber attacks (demo paper)
Computer networks are ubiquitous systems growing exponentially with a predicted 50 billion devices connected by 2050. This dramatically increases the potential attack surface of Internet networks. A key issue in cyber defense is to detect, categorize and identify these attacks, the way they are propagated and their potential impacts on the systems affected. The research presented in this paper models cyber attacks at large by considering the Internet as a complex system in which attacks are propagated over a network. We model an attack as a path from a source to a target, and where each attack is categorized according to its intention. We setup an experimental testbed with the concept of honeypot that evaluates the spatiotemporal distribution of these Internet attacks. The preliminary results show a series of patterns in space and time that illustrate the potential of the approach, and how cyber attacks can be categorized according to the concept and measure of entropy
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