9,996 research outputs found
Equilibrium magnetization in the vicinity of the first order phase transition in the mixed state of high-Tc superconductors
We present the results of a scaling analysis of isothermal magnetization M(H)
curves measured in the mixed state of high-Tc superconductors in the vicinity
of the established first order phase transition. The most surprising result of
our analysis is that the difference between the magnetization above and below
the transition may have either sign, depending on the particular chosen sample.
We argue that this observation, based on M(H) data available in the literature,
is inconsistent with the interpretation that the well known first order phase
transition in the mixed state of high-Tc superconductors always represents the
melting transition in the vortex system.Comment: 4 pages, 5 figure
Universality Class of the Reversible-Irreversible Transition in Sheared Suspensions
Collections of non-Brownian particles suspended in a viscous fluid and
subjected to oscillatory shear at very low Reynolds number have recently been
shown to exhibit a remarkable dynamical phase transition separating reversible
from irreversible behaviour as the strain amplitude or volume fraction are
increased. We present a simple model for this phenomenon, based on which we
argue that this transition lies in the universality class of the conserved DP
models or, equivalently, the Manna model. This leads to predictions for the
scaling behaviour of a large number of experimental observables. Non-Brownian
suspensions under oscillatory shear may thus constitute the first experimental
realization of an inactive-active phase transition which is not in the
universality class of conventional directed percolation.Comment: 4 pages, 2 figures, final versio
Quantifying Spatiotemporal Chaos in Rayleigh-B\'enard Convection
Using large-scale parallel numerical simulations we explore spatiotemporal
chaos in Rayleigh-B\'enard convection in a cylindrical domain with
experimentally relevant boundary conditions. We use the variation of the
spectrum of Lyapunov exponents and the leading order Lyapunov vector with
system parameters to quantify states of high-dimensional chaos in fluid
convection. We explore the relationship between the time dynamics of the
spectrum of Lyapunov exponents and the pattern dynamics. For chaotic dynamics
we find that all of the Lyapunov exponents are positively correlated with the
leading order Lyapunov exponent and we quantify the details of their response
to the dynamics of defects. The leading order Lyapunov vector is used to
identify topological features of the fluid patterns that contribute
significantly to the chaotic dynamics. Our results show a transition from
boundary dominated dynamics to bulk dominated dynamics as the system size is
increased. The spectrum of Lyapunov exponents is used to compute the variation
of the fractal dimension with system parameters to quantify how the underlying
high-dimensional strange attractor accommodates a range of different chaotic
dynamics
Magnetic substructure in the northern Fermi Bubble revealed by polarized WMAP emission
We report a correspondence between giant, polarized microwave structures
emerging north from the Galactic plane near the Galactic center and a number of
GeV gamma-ray features, including the eastern edge of the recently-discovered
northern Fermi Bubble. The polarized microwave features also correspond to
structures seen in the all-sky 408 MHz total intensity data, including the
Galactic center spur. The magnetic field structure revealed by the polarization
data at 23 GHz suggests that neither the emission coincident with the Bubble
edge nor the Galactic center spur are likely to be features of the local ISM.
On the basis of the observed morphological correspondences, similar inferred
spectra, and the similar energetics of all sources, we suggest a direct
connection between the Galactic center spur and the northern Fermi Bubble.Comment: Accepted for publication in The Astrophysical Journal Letters after
minor change
Itinerant-electron Ferromagnetism in W(Nb)O3-d
The crystal structure and the magnetic properties of the W1-xNbxO3-d,
(x<0.03) system have been investigated. In contrast to the orthorhombic
diamagnetic WO3, the material with x=0.01 is paramagnetic down to 5 K.
Introducing of 2.5 at. % of Nb into WO3 leads to a tetragonal structure and to
a weak itinerant ferromagnetic ordering below TC= 225 K. The saturation
magnetic moment at 5 K is 1.07*10-3 mB, whereas the paramagnetic effective
moment is 0.06 mB per mole. This high ratio indicates itinerant ferromagnetism
in W0.975Nb0.025O3-d.Comment: accepted to Physica
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