19,436 research outputs found
Particle-Hole Symmetry Breaking and the 5/2 Fractional Quantum Hall Effect
We report on the study of the fractional quantum Hall effect at the filling
factor 5/2 using exact diagonalization method with torus geometry. The
particle-hole symmetry breaking effect is considered using an additional
three-body interaction. Both Pfaffian and anti-Pfaffian states can be the
ground state depending on the sign of the three-body interaction. The results
of the low-energy spectrum, the wave function overlap, and the particle-hole
parity evolution, have shown the clear evidence of a direct sharp transition
(possibly first-order) from the Pfaffian to the anti-Pfaffian state at the
Coulomb point. A quantum phase diagram is established, where one finds further
transitions from the Pfaffian or anti-Pfaffian state to the nearby compressible
phases induced by a change of the pseudopotential.Comment: 4 pages, 4 figure
The Effects on , , and from Higher-Dimensional Fermion Representations
Inspired by a new class of walking technicolor models recently proposed using
higher-dimensional technifermions, we consider the oblique corrections from
heavy non-degenerate fermions with two classes of higher-dimensional
representations of the electroweak gauge group itself. One is chiral SM-like,
and the other is vector-like. In both cases, we obtain explicit expressions for
, , in terms of the fermion masses. We find that to keep the
parameter ultraviolet-finite there must be a stringent constraint on the mass
non-degeneracy of a heavy fermion multiplet.Comment: 4 page
Dynamical Computation on Coefficients of Electroweak Chiral Lagrangian from One-doublet and Topcolor-assisted Technicolor Models
Based on previous studies deriving the chiral Lagrangian for pseudo scalar
mesons from the first principle of QCD, we derive the electroweak chiral
Lagrangian and build up a formulation for computing its coefficients from
one-doublet technicolor model and a schematic topcolor-assisted technicolor
model. We find that the coefficients of the electroweak chiral Lagrangian for
the topcolor-assisted technicolor model are divided into three parts: direct
TC2 interaction part, TC1 and TC2 induced effective Z' particle contribution
part, and ordinary quarks contribution part. The first two parts are computed
in this paper and we show that the direct TC2 interaction part is the same as
that in the one-doublet technicolor model, while effective Z' contributions are
at least proportional to the p^2 order parameter \beta_1 in the electroweak
chiral Lagrangian and typical features of topcolor-assisted technicolor model
are that it only allows positive T and U parameters and the T parameter varies
in the range 0\sim 1/(25\alpha), the upper bound of T parameter will decrease
as long as Z' mass become large. The S parameter can be either positive or
negative depending on whether the Z' mass is large or small. The Z' mass is
also bounded above and the upper bound depend on value of T parameter. We
obtain the values for all the coefficients of the electroweak chiral Lagrangian
up to order of p^4.Comment: 52 pages, 15 figure
Broken-Symmetry States of Dirac Fermions in Graphene with A Partially Filled High Landau Level
We report on numerical study of the Dirac fermions in partially filled N=3
Landau level (LL) in graphene. At half-filling, the equal-time density-density
correlation function displays sharp peaks at nonzero wavevectors . Finite-size scaling shows that the peak value grows with electron
number and diverges in the thermodynamic limit, which suggests an instability
toward a charge density wave. A symmetry broken stripe phase is formed at large
system size limit, which is robust against purturbation from disorder
scattering. Such a quantum phase is experimentally observable through transport
measurements. Associated with the special wavefunctions of the Dirac LL, both
stripe and bubble phases become possible candidates for the ground state of the
Dirac fermions in graphene with lower filling factors in the N=3 LL.Comment: Contains are slightly changed. Journal reference and DOI are adde
Functional Genomics Profiling of Bladder Urothelial Carcinoma MicroRNAome as a Potential Biomarker.
Though bladder urothelial carcinoma is the most common form of bladder cancer, advances in its diagnosis and treatment have been modest in the past few decades. To evaluate miRNAs as putative disease markers for bladder urothelial carcinoma, this study develops a process to identify dysregulated miRNAs in cancer patients and potentially stratify patients based on the association of their microRNAome phenotype to genomic alterations. Using RNA sequencing data for 409 patients from the Cancer Genome Atlas, we examined miRNA differential expression between cancer and normal tissues and associated differentially expressed miRNAs with patient survival and clinical variables. We then correlated miRNA expressions with genomic alterations using the Wilcoxon test and REVEALER. We found a panel of six miRNAs dysregulated in bladder cancer and exhibited correlations to patient survival. We also performed differential expression analysis and clinical variable correlations to identify miRNAs associated with tobacco smoking, the most important risk factor for bladder cancer. Two miRNAs, miR-323a and miR-431, were differentially expressed in smoking patients compared to nonsmoking patients and were associated with primary tumor size. Functional studies of these miRNAs and the genomic features we identified for potential stratification may reveal underlying mechanisms of bladder cancer carcinogenesis and further diagnosis and treatment methods for urothelial bladder carcinoma
Dark Light Higgs
We study a limit of the nearly-Peccei-Quinn-symmetric Next-to-Minimal
Supersymmetric Standard Model possessing novel Higgs and dark matter (DM)
properties. In this scenario, there naturally co-exist three light singlet-like
particles: a scalar, a pseudoscalar, and a singlino-like DM candidate, all with
masses of order 0.1-10 GeV. The decay of a Standard Model-like Higgs boson to
pairs of the light scalars or pseudoscalars is generically suppressed, avoiding
constraints from collider searches for these channels. For a certain parameter
window annihilation into the light pseudoscalar and exchange of the light
scalar with nucleons allow the singlino to achieve the correct relic density
and a large direct detection cross section consistent with the CoGeNT and
DAMA/LIBRA preferred region simultaneously. This parameter space is consistent
with experimental constraints from LEP, the Tevatron, and Upsilon- and flavor
physics.Comment: 4 pages, 4 figures, final version for Phys. Rev. Let
Modified Sequential Kriging Optimization for Multidisciplinary Complex Product Simulation
Directing to the high cost of computer simulation optimization problem, Kriging surrogate model is widely used to decrease the computation time. Since the sequential Kriging optimization is time consuming, this article extends the expected improvement and put forwards a modified sequential Kriging optimization (MSKO). This method changes the twice optimization problem into once by adding more than one point at the same time. Before re-fitting the Kriging model, the new sample points are verified to ensure that they do not overlap the previous one and the distance between two sample points is not too small. This article presents the double stopping criterion to keep the root mean square error (RMSE) of the final surrogate model at an acceptable level. The example shows that MSKO can approach the global optimization quickly and accurately. MSKO can ensure global optimization no matter where the initial point is. Application of active suspension indicates that the proposed method is effective. © 2010 Chinese Journal of Aeronautics
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Operando STM study of the interaction of imidazolium-based ionic liquid with graphite
Understanding interactions at the interfaces of carbon with ionic liquids (ILs) is crucially beneficial for the diagnostics and performance improvement of electrochemical devices containing carbon as active materials or conductive additives in electrodes and ILs as solvents or additives in electrolytes. The interfacial interactions of three typical imidazolium-based ILs, 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (AMImTFSI) ILs having ethyl (C2), butyl (C4) and octyl (C8) chains in their cations, with highly oriented pyrolytic graphite (HOPG) were studied in-situ by electrochemical scanning tunneling microscopy (EC-STM). The etching of HOPG surface and the exfoliation of graphite/graphene flakes as well as cation intercalation were observed at the HOPG/C2MImTFSI interface. The etching also takes place in C4MImTFSI at −1.5 V vs Pt but only at step edges with a much slower rate, whereas C8MIm+ cations adsorbs strongly on the HOPG surface under similar conditions with no observable etching or intercalation. The EC-STM observations can be explained by the increase in van der Waals interaction between the cations and the graphite surface with increasing length of alkyl chains
Origin of the Scaling Law in Human Mobility: Hierarchical Organization of Traffic Systems
Uncovering the mechanism leading to the scaling law in human trajectories is
of fundamental importance in understanding many spatiotemporal phenomena. We
propose a hierarchical geographical model to mimic the real traffic system,
upon which a random walker will generate a power-law travel displacement
distribution with exponent -2. When considering the inhomogeneities of cities'
locations and attractions, this model reproduces a power-law displacement
distribution with an exponential cutoff, as well as a scaling behavior in the
probability density of having traveled a certain distance at a certain time.
Our results agree very well with the empirical observations reported in [D.
Brockmann et al., Nature 439, 462 (2006)].Comment: 6 figures, 4 page
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