1,527 research outputs found
Charge modulation as fingerprints of phase-string triggered interference
Charge order appears to be an ubiquitous phenomenon in doped Mott insulators,
which is currently under intense experimental and theoretical investigations
particularly in the high cuprates. This phenomenon is conventionally
understood in terms of Hartree-Fock type mean field theory. Here we demonstrate
a mechanism for charge modulation which is rooted in the many-particle quantum
physics arising in the strong coupling limit. Specifically, we consider the
problem of a single hole in a bipartite ladder. As a remnant of the
fermion signs, the hopping hole picks up subtle phases pending the fluctuating
spins, the so-called phase string effect. We demonstrate the presence of charge
modulations in the density matrix renormalization group solutions which
disappear when the phase strings are switched off. This form of charge
modulation can be understood analytically in a path-integral language, showing
that the phase strings give rise to constructive interferences leading to
self-localization. When the latter occurs, left- and right-moving propagating
modes emerge inside the localization volume and their interference is
responsible for the real space charge modulation.Comment: 14 pages, 10 figures. Comments on a followup paper by S. R. White, D.
J. Scalapino, and S. A. Kivelson (arXiv:1502.04403) adde
One-bit Supervision for Image Classification: Problem, Solution, and Beyond
This paper presents one-bit supervision, a novel setting of learning with
fewer labels, for image classification. Instead of training model using the
accurate label of each sample, our setting requires the model to interact with
the system by predicting the class label of each sample and learn from the
answer whether the guess is correct, which provides one bit (yes or no) of
information. An intriguing property of the setting is that the burden of
annotation largely alleviates in comparison to offering the accurate label.
There are two keys to one-bit supervision, which are (i) improving the guess
accuracy and (ii) making good use of the incorrect guesses. To achieve these
goals, we propose a multi-stage training paradigm and incorporate negative
label suppression into an off-the-shelf semi-supervised learning algorithm.
Theoretical analysis shows that one-bit annotation is more efficient than
full-bit annotation in most cases and gives the conditions of combining our
approach with active learning. Inspired by this, we further integrate the
one-bit supervision framework into the self-supervised learning algorithm which
yields an even more efficient training schedule. Different from training from
scratch, when self-supervised learning is used for initialization, both hard
example mining and class balance are verified effective in boosting the
learning performance. However, these two frameworks still need full-bit labels
in the initial stage. To cast off this burden, we utilize unsupervised domain
adaptation to train the initial model and conduct pure one-bit annotations on
the target dataset. In multiple benchmarks, the learning efficiency of the
proposed approach surpasses that using full-bit, semi-supervised supervision.Comment: ACM TOMM. arXiv admin note: text overlap with arXiv:2009.0616
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