31,193 research outputs found
Multichannel charge Kondo effect and non-Fermi liquid fixed points in conventional and topological superconductor islands
We study multiterminal Majorana and conventional superconducting islands in
the vicinity of the charge degeneracy point using bosonization and numerical
renormalization group. Both models map to the multichannel charge Kondo
problem, but for noninteracting normal leads they flow to different non-Fermi
liquid fixed points at low temperatures. We compare and contrast both cases by
numerically obtaining the full crossover to the low temperature regime and
predict distinctive transport signatures. We attribute the differences between
both types of islands to a crucial distinction of charge- and charge-
transfer in the conventional and topological case, respectively. In the
conventional case, our results establish s-wave islands as a new platform to
study the intermediate multichannel Kondo fixed point. In the topological setup
the crossover temperature to non-Fermi liquid behavior is relatively high as it
is proportional to level broadening and the transport results are not sensitive
to channel coupling anisotropy, moving away from the charge degeneracy point or
including a small Majorana hybridization, which makes our proposal
experimentally feasible.Comment: 14 pages, 10 figure
Numerical Study of Quantum Hall Bilayers at Total Filling : A New Phase at Intermediate Layer Distances
We study the phase diagram of quantum Hall bilayer systems with total filing
of the lowest Landau level as a function of layer distances
. Based on numerical exact diagonalization calculations, we obtain three
distinct phases, including an exciton superfluid phase with spontaneous
interlayer coherence at small , a composite Fermi liquid at large , and
an intermediate phase for ( is the magnetic length). The
transition from the exciton superfluid to the intermediate phase is identified
by (i) a dramatic change in the Berry curvature of the ground state under
twisted boundary conditions on the two layers; (ii) an energy level crossing of
the first excited state. The transition from the intermediate phase to the
composite Fermi liquid is identified by the vanishing of the exciton superfluid
stiffness. Furthermore, from our finite-size study, the energy cost of
transferring one electron between the layers shows an even-odd effect and
possibly extrapolates to a finite value in the thermodynamic limit, indicating
the enhanced intralayer correlation. Our identification of an intermediate
phase and its distinctive features shed new light on the theoretical
understanding of the quantum Hall bilayer system at total filling .Comment: 5 pages, 3 figures (main text); 5 pages, 4 figures (supplementary
material); to be published in PR
Keeping Context In Mind: Automating Mobile App Access Control with User Interface Inspection
Recent studies observe that app foreground is the most striking component
that influences the access control decisions in mobile platform, as users tend
to deny permission requests lacking visible evidence. However, none of the
existing permission models provides a systematic approach that can
automatically answer the question: Is the resource access indicated by app
foreground? In this work, we present the design, implementation, and evaluation
of COSMOS, a context-aware mediation system that bridges the semantic gap
between foreground interaction and background access, in order to protect
system integrity and user privacy. Specifically, COSMOS learns from a large set
of apps with similar functionalities and user interfaces to construct generic
models that detect the outliers at runtime. It can be further customized to
satisfy specific user privacy preference by continuously evolving with user
decisions. Experiments show that COSMOS achieves both high precision and high
recall in detecting malicious requests. We also demonstrate the effectiveness
of COSMOS in capturing specific user preferences using the decisions collected
from 24 users and illustrate that COSMOS can be easily deployed on smartphones
as a real-time guard with a very low performance overhead.Comment: Accepted for publication in IEEE INFOCOM'201
Crossing by a single scalar field coupling with matter and the observational constraints
Motivated by Yang-Mills dark energy model, we propose a new model by
introducing a logarithmic correction. we find that this model can avoid the
coincidence problem naturally and gives an equation of state smoothly
crossing -1 if an interaction between dark energy and dark matter exists. It
has a stable tracker solution as well. To confront with observations based on
the combined data of SNIa, BAO, CMB and Hubble parameter, we obtain the best
fit values of the parameters with errors for the
noncoupled model: ,
, and for the coupled model with a decaying
rate : ,
. In particular, it is found that the
non-coupled model has a dynamic evolution almost undistinguishable to
CDM at the late-time Universe.Comment: 12 pages, 3 figures, the published versio
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