240,249 research outputs found
Informality and the Development and Demolition of Urban Villages in the Chinese Peri-urban Area
The fate of Chinese urban villages (chengzhongcun) has recently attracted both research and policy attention. Two important unaddressed questions are: what are the sources of informality in otherwise orderly Chinese cities; and, will village redevelopment policy eliminate informality in the Chinese city? Reflecting on the long-established study of informal settlements and recent research on informality, it is argued that the informality in China has been created by the dual urban-rural land market and land management system and by an underprovision of migrant housing. The redevelopment of chengzhongcun is an attempt to eliminate this informality and to create more governable spaces through formal land development; but since it fails to tackle the root demand for unregulated living and working space, village redevelopment only leads to the replication of informality in more remote rural villages, in other urban neighbourhoods and, to some extent, in the redeveloped neighbourhoods. © 2012 Urban Studies Journal Limited
Renormalization of transition matrix elements of particle number operators due to strong electron correlation
Renormalization of non-magnetic and magnetic impurities due to electron
double occupancy prohibition is derived analytically by an improved Gutzwiller
approximation. Non-magnetic impurities are effectively weakened by the same
renormalization factor as that for the hopping amplitude, whereas magnetic
impurities are strengthened by the square root of the spin-exchange
renormalization factor, in contrast to results by the conventional Gutzwiller
approximation. We demonstrate it by showing that transition matrix elements of
number operators between assumed excited states and between an assumed ground
state and excited states are renormalized differently than diagonal matrix
elements. Deviation from such simple renormalization with a factor is also
discussed. In addition, as related calculation, we correct an error in
treatment of renormalization of charge interaction in the literature. Namely,
terms from the second order of the transition matrix elements are strongly
suppressed. Since all these results do not depend on the signs of impurity
potential or charge interaction parameter, they are valid both in attractive
and repulsive cases.Comment: 12 page
Possible Weyl fermions in the magnetic Kondo system CeSb
Materials where the electronic bands have unusual topologies allow for the
realization of novel physics and have a wide range of potential applications.
When two electronic bands with linear dispersions intersect at a point, the
excitations could be described as Weyl fermions which are massless particles
with a particular chirality. Here we report evidence for the presence of Weyl
fermions in the ferromagnetic state of the low-carrier density, strongly
correlated Kondo lattice system CeSb, from electronic structure calculations
and angle-dependent magnetoresistance measurements. When the applied magnetic
field is parallel to the electric current, a pronounced negative
magnetoresistance is observed within the ferromagnetic state, which is
destroyed upon slightly rotating the field away. These results give evidence
for CeSb belonging to a new class of Kondo lattice materials with Weyl fermions
in the ferromagnetic state.Comment: 18 pages, 4 figures, Supplementary Information available from journal
link (open access
Orbital-resolved vortex core states in FeSe Superconductors: calculation based on a three-orbital model
We study electronic structure of vortex core states of FeSe superconductors
based on a t three-orbital model by solving the Bogoliubov-de
Gennes(BdG) equation self-consistently. The orbital-resolved vortex core states
of different pairing symmetries manifest themselves as distinguishable
structures due to different quasi-particle wavefunctions. The obtained vortices
are classified in terms of the invariant subgroups of the symmetry group of the
mean-field Hamiltonian in the presence of magnetic field. Isotropic and
anisotropic wave vortices have symmetry for each orbital, whereas
wave vortices show symmetry for orbitals
and symmetry for orbital. In the case of
wave vortices, hybridized-pairing between and orbitals gives
rise to a relative phase difference in terms of gauge transformed pairing order
parameters between and orbitals, which is essentially
caused by a transformation of co-representation of and
subgroup. The calculated local density of states(LDOS) of wave
vortices show qualitatively similar pattern with experiment results. The phase
difference of between and orbital-resolved
wave vortices can be verified by further experiment observation
Sustainability in design: now! Challenges and opportunities for design research, education and practice in the XXI century
Copyright @ 2010 Greenleaf PublicationsLeNS project funded by the Asia Link Programme, EuropeAid, European Commission
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