3,237 research outputs found

### Magnetoconductivity of Dirac fermions in graphene under charged impurity scatterings

On the basis of self-consistent Born approximation, we solve the
Bethe-Salpeter matrix equations for Cooperon propagator of the Dirac fermions
in graphene under the charged impurity scatterings and a weak external magnetic
field. In the absence of the magnetic field, the quantum interference effect in
the electric conductivity from the contribution of Cooperon propagator will be
studied and possible weak localization in the system is discussed in terms of
the sample length and temperature. The magnetoconductivity stemming from the
quantum interference effect is calculated, and the obtained results are in good
agreement with experimental measurements.Comment: 13 pages, 9 figure

### CSNL: A cost-sensitive non-linear decision tree algorithm

This article presents a new decision tree learning algorithm called CSNL that induces Cost-Sensitive Non-Linear decision trees. The algorithm is based on the hypothesis that nonlinear decision nodes provide a better basis than axis-parallel decision nodes and utilizes discriminant analysis to construct nonlinear decision trees that take account of costs of misclassification.
The performance of the algorithm is evaluated by applying it to seventeen datasets and the results are compared with those obtained by two well known cost-sensitive algorithms, ICET and MetaCost, which generate multiple trees to obtain some of the best results to date. The results show that CSNL performs at least as well, if not better than these algorithms, in more than twelve of the datasets and is considerably faster. The use of bagging with CSNL further enhances its performance showing the significant benefits of using nonlinear decision nodes.
The performance of the algorithm is evaluated by applying it to seventeen data sets and the results are
compared with those obtained by two well known cost-sensitive algorithms, ICET and MetaCost, which generate multiple trees to obtain some of the best results to date.
The results show that CSNL performs at least as well, if not better than these algorithms, in more than twelve of the data sets and is considerably faster.
The use of bagging with CSNL further enhances its performance showing the significant benefits of using non-linear decision nodes

### Single vortex structure in two models of iron pnictide $s^\pm$ superconductivity

The structure of a single vortex in a FeAs superconductor is studied in the
framework of two formulations of superconductivity for the recently proposed
sign-reversed $s$ wave ($s^\pm$) scenario: {\it (i)} a continuum model taking
into account the existence of an electron and a hole band with a repulsive
local interaction between the two; {\it (ii)} a lattice tight-binding model
with two orbitals per unit cell and a next-nearest-neighbour attractive
interaction. In the first model, the local density of states (LDOS) at the
vortex centre, as a function of energy, exhibits a peak at the Fermi level,
while in the second model such LDOS peak is deviated from the Fermi level and
its energy depends on band filling. An impurity located outside the vortex core
has little effect on the LDOS peak, but an impurity close to the vortex core
can almost suppress it and modify its position.Comment: 17 pages, 15 figures. Accepted for publication in New Journal of
Physic

### Higher order contributions to Rashba and Dresselhaus effects

We have developed a method to systematically compute the form of Rashba- and
Dresselhaus-like contributions to the spin Hamiltonian of heterostructures to
an arbitrary order in the wavevector k. This is achieved by using the double
group representations to construct general symmetry-allowed Hamiltonians with
full spin-orbit effects within the tight-binding formalism. We have computed
full-zone spin Hamiltonians for [001]-, [110]- and [111]-grown zinc blende
heterostructures (D_{2d},C_{4v},C_{2v},C_{3v} point group symmetries), which
are commonly used in spintronics. After an expansion of the Hamiltonian up to
third order in k, we are able to obtain additional terms not found previously.
The present method also provides the matrix elements for bulk zinc blendes
(T_d) in the anion/cation and effective bond orbital model (EBOM) basis sets
with full spin-orbit effects.Comment: v1: 11 pages, 3 figures, 8 table

### Understanding Face and Shame: A Servant-Leadership and Face Management Model

Clergy can have a negative impact on churches and other individuals when they knowingly or unknowingly attempt to save face, that is, try to protect their standing or reputation. The desire to gain face and the fear of losing face and feeling ashamed will likely permeate clergyâs decision-making processes without even being noticed. This study explores the essence of face and face management and the relationship between face management and two characteristics of servant-leadershipâawareness and healingâin both Chinese and American churches through the methodology of hermeneutic phenomenology. Prior to this study, to my knowledge, no hermeneutic phenomenological research of face management has been conducted in a church setting. Through a review of the literature, four areas are explored: face and shame, face management, servant-leadership, and face, shame, and face management within the church. This study obtained approval from the Institutional Review Board and informed consent from the participants. Three Chinese and three American Christian ministers were chosen to complete a question sheet and participate in two semi-structured interview sessions. A first cycle of open coding and second cycle of pattern coding were used during data analysis. Face experiences are discussed in light of eight major themes: body, triggers, becoming, face concepts, strategies, emotions, servant-leadership, and the church. Findings from the study help build a servant-leadership and face management model, which can offer an anchored approach for clergy and pastoral counselors to address face and shame and to develop therapeutic interventions

### Optimal Controlled teleportation via several kinds of three-qubit states

The probability of successfully controlled teleportating an unknown qubit
using a general three-particle state is investigated. We give the analytic
expressions of maximal probabilities of successfully controlled teleportating
an unknown qubit via several kinds of tripartite states including a tripartite
GHZ state and a tripartite W-state.Comment: 15 page

### Schr\"{o}dinger Fields on the Plane with $[U(1)]^N$ Chern-Simons Interactions and Generalized Self-dual Solitons

A general non-relativistic field theory on the plane with couplings to an
arbitrary number of abelian Chern-Simons gauge fields is considered. Elementary
excitations of the system are shown to exhibit fractional and mutual
statistics. We identify the self-dual systems for which certain classical and
quantal aspects of the theory can be studied in a much simplified mathematical
setting. Then, specializing to the general self-dual system with two
Chern-Simons gauge fields (and non-vanishing mutual statistics parameter), we
present a systematic analysis for the static vortexlike classical solutions,
with or without uniform background magnetic field. Relativistic generalizations
are also discussed briefly.Comment: 49 pages including 4 figures, LATEX ( three LATEX figures and one
PICTEX figure), SNUTP 93-14, UMN-TH-113

### Spin relaxation in (110) and (001) InAs/GaSb superlattices

We report an enhancement of the electron spin relaxation time (T1) in a (110)
InAs/GaSb superlattice by more than an order of magnitude (25 times) relative
to the corresponding (001) structure. The spin dynamics were measured using
polarization sensitive pump probe techniques and a mid-infrared, subpicosecond
PPLN OPO. Longer T1 times in (110) superlattices are attributed to the
suppression of the native interface asymmetry and bulk inversion asymmetry
contributions to the precessional D'yakonov Perel spin relaxation process.
Calculations using a nonperturbative 14-band nanostructure model give good
agreement with experiment and indicate that possible structural inversion
asymmetry contributions to T1 associated with compositional mixing at the
superlattice interfaces may limit the observed spin lifetime in (110)
superlattices. Our findings have implications for potential spintronics
applications using InAs/GaSb heterostructures.Comment: 4 pages, 2 figure

### Mean-Field Description of Phase String Effect in the $t-J$ Model

A mean-field treatment of the phase string effect in the $t-J$ model is
presented. Such a theory is able to unite the antiferromagnetic (AF) phase at
half-filling and metallic phase at finite doping within a single theoretical
framework. We find that the low-temperature occurrence of the AF long range
ordering (AFLRO) at half-filling and superconducting condensation in metallic
phase are all due to Bose condensations of spinons and holons, respectively, on
the top of a spin background described by bosonic resonating-valence-bond (RVB)
pairing. The fact that both spinon and holon here are bosonic objects, as the
result of the phase string effect, represents a crucial difference from the
conventional slave-boson and slave-fermion approaches. This theory also allows
an underdoped metallic regime where the Bose condensation of spinons can still
exist. Even though the AFLRO is gone here, such a regime corresponds to a
microscopic charge inhomogeneity with short-ranged spin ordering. We discuss
some characteristic experimental consequences for those different metallic
regimes. A perspective on broader issues based on the phase string theory is
also discussed.Comment: 18 pages, five figure

- âŠ