148,523 research outputs found
First-Principles Study of Integer Quantum Hall Transitions in Mesoscopic Samples
We perform first principles numerical simulations to investigate resistance
fluctuations in mesoscopic samples, near the transition between consecutive
Quantum Hall plateaus. We use six-terminal geometry and sample sizes similar to
those of real devices. The Hall and longitudinal resistances extracted from the
generalized Landauer formula reproduce all the experimental features uncovered
recently. We then use a simple generalization of the Landauer-B\"uttiker model,
based on the interplay between tunneling and chiral currents -- the co-existing
mechanisms for transport -- to explain the three distinct types of fluctuations
observed, and identify the central region as the critical region.Comment: changes to acknowledgements onl
Statistical significance of rich-club phenomena in complex networks
We propose that the rich-club phenomena in complex networks should be defined
in the spirit of bootstrapping, in which a null model is adopted to assess the
statistical significance of the rich-club detected. Our method can be served as
a definition of rich-club phenomenon and is applied to analyzing three real
networks and three model networks. The results improve significantly compared
with previously reported results. We report a dilemma with an exceptional
example, showing that there does not exist an omnipotent definition for the
rich-club phenomenon.Comment: 3 Revtex pages + 5 figure
Large Momenta Fluctuations Of Charm Quarks In The Quark-Gluon Plasma
We show that large fluctuations of D mesons kinetic energy (or momentum)
distributions might be a signature of a phase transition to the quark gluon
plasma (QGP). In particular, a jump in the variance of the momenta or kinetic
energy, as a function of a control parameter (temperature or Fermi energy at
finite baryon densities) might be a signature for a first order phase
transition to the QGP. This behaviour is completely consistent with the order
parameter defined for a system of interacting quarks at zero temperature and
finite baryon densities which shows a jump in correspondance to a first order
phase transition to the QGP. The shows exactly the same behavior of
the order parameter and of the variance of the D mesons. We discuss
implications for relativistic heavy ion collisions within the framework of a
transport model and possible hints for experimental data.Comment: 4 pages 3 figure
Conditions for Nondistortion Interrogation of Quantum System
Under some physical considerations, we present a universal formulation to
study the possibility of localizing a quantum object in a given region without
disturbing its unknown internal state. When the interaction between the object
and probe wave function takes place only once, we prove the necessary and
sufficient condition that the object's presence can be detected in an initial
state preserving way. Meanwhile, a conditioned optimal interrogation
probability is obtained.Comment: 5 pages, Revtex, 1 figures, Presentation improved, corollary 1 added.
To appear in Europhysics Letter
- …