8,231 research outputs found
The Fractional Quantum Hall effect in an array of quantum wires
We demonstrate the emergence of the quantum Hall (QH) hierarchy in a 2D model
of coupled quantum wires in a perpendicular magnetic field. At commensurate
values of the magnetic field, the system can develop instabilities to
appropriate inter-wire electron hopping processes that drive the system into a
variety of QH states. Some of the QH states are not included in the
Haldane-Halperin hierarchy. In addition, we find operators allowed at any field
that lead to novel crystals of Laughlin quasiparticles. We demonstrate that any
QH state is the groundstate of a Hamiltonian that we explicitly construct.Comment: Revtex, 4 pages, 2 figure
Compressed SUSY search at the 13 TeV LHC using kinematic correlations and structure of ISR jets
The LHC search for nearly degenerate gluinos and neutralinos, which can
occur, for example, in SUSY axion models, is limited by the reduced missing
transverse momentum and effective mass in the events. We propose the use of
kinematic correlations between jets coming from initial state radiation (ISR)
in gluino pair production events at the 13 TeV LHC. A significant improvement
in the signal to background ratio is obtained for the highly compressed
gluino-neutralino search, by using cuts on the rapidity and azimuthal angle
separation between the pair of tagged jets with the highest transverse momenta.
Furthermore, the distribution of the azimuthal angle difference between the
tagged jets in the gluino-pair+jets process is found to be distinctly different
from the dominant background process of Z+jets. We also find quark and gluon
jet tagging methods to be useful in separating the signal, which contains a
higher fraction of gluon initiated jets compared to the dominant backgrounds.Comment: 19 pages, 3 figures; v2: Standard model background estimates
improved, comments and references adde
Density dependence of nuclear symmetry energy constrained by mean-field calculations
We establish a correlation for the symmetry energy at saturation density
, slope parameter and curvature parameter based on
widely different mean field interactions. With the help of this correlation and
available empirical and theoretical information, the density dependent behavior
around the saturation density is determined. We compare the results obtained
with the present approach with those by other analyses. With this obtained
density dependent behavior of the symmetry energy, the neutron skin thickness
of Pb and some properties of neutron stars are investigated. In
addition, it is found that the expression or does not reproduce the density dependence of the symmetry
energy as predicted by the mean-field approach around nuclear saturation
density.Comment: 6 pages, 4 figure
Holography of Gravitational Action Functionals
Einstein-Hilbert (EH) action can be separated into a bulk and a surface term,
with a specific ("holographic") relationship between the two, so that either
can be used to extract information about the other. The surface term can also
be interpreted as the entropy of the horizon in a wide class of spacetimes.
Since EH action is likely to just the first term in the derivative expansion of
an effective theory, it is interesting to ask whether these features continue
to hold for more general gravitational actions. We provide a comprehensive
analysis of lagrangians of the form L=Q_a^{bcd}R^a_{bcd}, in which Q_a^{bcd} is
a tensor with the symmetries of the curvature tensor, made from metric and
curvature tensor and satisfies the condition \nabla_cQ^{abcd}=0, and show that
they share these features. The Lanczos-Lovelock lagrangians are a subset of
these in which Q^{abcd} is a homogeneous function of the curvature tensor. They
are all holographic, in a specific sense of the term, and -- in all these cases
-- the surface term can be interpreted as the horizon entropy. The
thermodynamics route to gravity, in which the field equations are interpreted
as TdS=dE+pdV, seems to have greater degree of validity than the field
equations of Einstein gravity itself. The results suggest that the holographic
feature of EH action could also serve as a new symmetry principle in
constraining the semiclassical corrections to Einstein gravity. The
implications are discussed.Comment: revtex 4; 17 pages; no figure
Scalar and Spinor Perturbation to the Kerr-NUT Spacetime
We study the scalar and spinor perturbation, namely the Klein-Gordan and
Dirac equations, in the Kerr-NUT space-time. The metric is invariant under the
duality transformation involving the exchange of mass and NUT parameters on one
hand and radial and angle coordinates on the other. We show that this
invariance is also shared by the scalar and spinor perturbation equations.
Further, by the duality transformation, one can go from the Kerr to the dual
Kerr solution, and vice versa, and the same applies to the perturbation
equations. In particular, it turns out that the potential barriers felt by the
incoming scalar and spinor fields are higher for the dual Kerr than that for
the Kerr. We also comment on existence of horizon and singularity.Comment: 31 pages including 20 figures, RevTeX style: Final version to appear
in Classical and Quantum Gravit
Identifying Attrition Phases in Survey Data: Applicability and Assessment Study
Background: Although Web-based questionnaires are an efficient, increasingly popular mode of data collection, their utility is often challenged by high participant dropout. Researchers can gain insight into potential causes of high participant dropout by analyzing the dropout patterns.
Objective: This study proposed the application of and assessed the use of user-specified and existing hypothesis testing methods in a novel setting—survey dropout data—to identify phases of higher or lower survey dropout.
Methods: First, we proposed the application of user-specified thresholds to identify abrupt differences in the dropout rate. Second, we proposed the application of 2 existing hypothesis testing methods to detect significant differences in participant dropout. We assessed these methods through a simulation study and through application to a case study, featuring a questionnaire addressing decision-making surrounding cancer screening.
Results: The user-specified method set to a low threshold performed best at accurately detecting phases of high attrition in both the simulation study and test case application, although all proposed methods were too sensitive.
Conclusions: The user-specified method set to a low threshold correctly identified the attrition phases. Hypothesis testing methods, although sensitive at times, were unable to accurately identify the attrition phases. These results strengthen the case for further development of and research surrounding the science of attrition
Automated tuning of inter-dot tunnel couplings in quantum dot arrays
Semiconductor quantum dot arrays defined electrostatically in a 2D electron
gas provide a scalable platform for quantum information processing and quantum
simulations. For the operation of quantum dot arrays, appropriate voltages need
to be applied to the gate electrodes that define the quantum dot potential
landscape. Tuning the gate voltages has proven to be a time-consuming task,
because of initial electrostatic disorder and capacitive cross-talk effects.
Here, we report on the automated tuning of the inter-dot tunnel coupling in a
linear array of gate-defined semiconductor quantum dots. The automation of the
tuning of the inter-dot tunnel coupling is the next step forward in scalable
and efficient control of larger quantum dot arrays. This work greatly reduces
the effort of tuning semiconductor quantum dots for quantum information
processing and quantum simulation
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