46,736 research outputs found
Topology protection-unprotection transition: an example from multi-terminal superconducting nanostructures
We show theoretically that in the superconducting nanostructures the gapped
states of different topology are not always protected by separating gapped
states. Depending on the structure design parameters, they can be either
protected or not, with a protection-unprotection transition separating these
two distinct situations. We build up a general theoretical description of the
transition vicinity in the spirit of Landau theory. We speculate that similar
protection-unprotection transitions may also occur for other realizations of
topological protection in condensed matter systems
A Discrepancy-Based Design for A/B Testing Experiments
The aim of this paper is to introduce a new design of experiment method for
A/B tests in order to balance the covariate information in all treatment
groups. A/B tests (or "A/B/n tests") refer to the experiments and the
corresponding inference on the treatment effect(s) of a two-level or
multi-level controllable experimental factor. The common practice is to use a
randomized design and perform hypothesis tests on the estimates. However, such
estimation and inference are not always accurate when covariate imbalance
exists among the treatment groups. To overcome this issue, we propose a
discrepancy-based criterion and show that the design minimizing this criterion
significantly improves the accuracy of the treatment effect(s) estimates. The
discrepancy-based criterion is model-free and thus makes the estimation of the
treatment effect(s) robust to the model assumptions. More importantly, the
proposed design is applicable to both continuous and categorical response
measurements. We develop two efficient algorithms to construct the designs by
optimizing the criterion for both offline and online A/B tests. Through
simulation study and a real example, we show that the proposed design approach
achieves good covariate balance and accurate estimation.Comment: 42 Pages 10 Figure
Supercurrents in chiral channels originate from upstream information transfer: a theoretical prediction
It has been thought that the long chiral edge channels cannot support any
supercurrent between the superconducting electrodes. We show theoretically that
the supercurrent can be mediated by a non-local interaction that facilitates a
long-distance information transfer in the direction opposite to electron flow.
We compute the supercurrent for several interaction models, including that of
an external circuit
Non-embeddability into a fixed sphere for a family of compact real algebraic hypersurfaces
We study the holomorphic embedding problem from a compact strongly
pseudoconvex real algebraic hypersurface into a sphere of higher dimension. We
construct a family of compact strongly pseudoconvex hypersurfaces
in and prove that for any integer , there is
a number with such that for any with
, can not be locally holomorphically
embedded into the unit sphere in Comment: 13 page
Interaction-induced supercurrent in quantum Hall setups
Recently we have proposed an unusual mechanism of superconducting current
that is specific for Quantum Hall Edge channels connected to superconducting
electrodes. We have shown that the supercurrent can be mediated by a nonlocal
electon-electon interaction that provide an opportunity for a long-distance
information transfer in the direction opposite to the electron flow. A
convenient model for such interaction is that of an external circuit. The
consideration has been done for the case of a single channel.
In this work, we extend these results to more sophisticated setups that
include the scattering between Quantum Hall channels of opposite direction and
multiple superconducting contacts. For a single Quantum Hall constriction, we
derive a general and comprehensive relation for the interaction- induced
supercurrent in terms of scattering amplitudes and demonstrate the non-local
nature of the current by considering its sensitivity to scattering. We
understand the phase dependences of the supercurrents in multi-terminal setups
in terms of interference of Andreev reflection processes. For more complex
setups encompassing at least two constrictions we find an interplay between
non-interacting and interaction-induced currents and contibutions of complex
interference processes
Expansion of EYM Amplitudes in Gauge Invariant Vector Space
Motivated by the problem of expanding single-trace tree-level amplitude of
Einstein-Yang-Mills theory to the BCJ basis of Yang-Mills amplitudes, we
present an alternative expansion formula in the gauge invariant vector space.
Starting from a generic vector space consisting of polynomials of momenta and
polarization vectors, we define a new sub-space as gauge invariant vector space
by imposing constraints of gauge invariant conditions. To characterize this
sub-space, we compute its dimension and construct an explicit gauge invariant
basis from it. We propose an expansion formula in the gauge invariant basis
with expansion coefficients being linear combinations of Yang-Mills amplitude,
manifesting the gauge invariance of both expansion basis and coefficients. With
help of quivers, we compute the expansion coefficients via differential
operators and demonstrate the general expansion algorithm by several examples.Comment: 54 pages, references added, references added. Version published in
Chinese Physics
Joint Learning of Neural Networks via Iterative Reweighted Least Squares
In this paper, we introduce the problem of jointly learning feed-forward
neural networks across a set of relevant but diverse datasets. Compared to
learning a separate network from each dataset in isolation, joint learning
enables us to extract correlated information across multiple datasets to
significantly improve the quality of learned networks. We formulate this
problem as joint learning of multiple copies of the same network architecture
and enforce the network weights to be shared across these networks. Instead of
hand-encoding the shared network layers, we solve an optimization problem to
automatically determine how layers should be shared between each pair of
datasets. Experimental results show that our approach outperforms baselines
without joint learning and those using pretraining-and-fine-tuning. We show the
effectiveness of our approach on three tasks: image classification, learning
auto-encoders, and image generation
Distinguishing the right-handed up/charm quarks from top quark via discrete symmetries in the standard model extensions
We propose a class of the two Higgs doublet Standard models (SMs) with a SM
singlet and a class of supersymmetric SMs with two pairs of Higgs doublets,
where the right-handed up/charm quarks and the right-handed top quark have
different quantum numbers under extra discrete symmetries. Thus, the
right-handed up and charm quarks couple to one Higgs doublet field, while the
right-handed top quark couples to another Higgs doublet. The quark CKM mixings
can be generated from the down-type quark sector. As one of phenomenological
consequences in our models, we explore whether one can accommodate the observed
direct CP asymmetry difference in singly Cabibbo-suppressed D decays. We show
that it is possible to explain the measured values of CP violation under
relevant experimental constraints.Comment: 20 pages; matches published versio
Feed-down effect on spin polarization
We develop a theoretical framework to study the feed-down effect of
higher-lying strange baryons on the spin polarization of the hyperon.
In this framework, we consider two-body decays through strong, electromagnetic,
and weak processes and derive general formulas for the angular distribution and
spin polarization of the daughter particle by adopting the helicity formalism.
Using the realistic experimental data as input, we explore the feed-down
contribution to the global and the local polarizations and find that
such a contribution suppresses the primordial polarization, which is
not strong enough to resolve the discrepancy between the current theoretical
and the experimental results on the azimuthal-angle dependence of
polarization. Our paper may also be useful for the measurement of spin
polarization of baryons heavier than (e.g., ) in future
experiments.Comment: 12 pages, 9 figure
E6 GUT through Effects of Dimension-5 Operators
In the effective field theory framework, quantum gravity can induce effective
dimension-5 operators, which have important impacts on grand unified theories.
Interestingly, one of main effects is the modification of the usual gauge
coupling unification condition. We investigate the gauge coupling unification
in under modified gauge coupling unification condition at scales
in the presence of one or more dimension-5 operators. It is shown that
nonsupersymmetric models of unification can be obtained and can easily
satisfy the constraints from the proton lifetime. For constructing these
models, we consider several maximal subgroups , and of and the
usual breaking chains for a specific maximal subgroup, and derive all of the
Clebsch-Gordan coefficients associated with breaking
to the Standard Model, which are given in Appendix A.Comment: 20 pages, 10 tables, 8 figures, journal accepted versio
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