1,726 research outputs found
Quantum Dynamics of Mesoscopic Driven Duffing Oscillators
We investigate the nonlinear dynamics of a mesoscopic driven Duffing
oscillator in a quantum regime. In terms of Wigner function, we identify the
nature of state near the bifurcation point, and analyze the transient process
which reveals two distinct stages of quenching and escape. The rate process in
the escape stage allows us to extract the transition rate, which displays
perfect scaling behavior with the driving distance to the bifurcation point. We
numerically determine the scaling exponent, compare it with existing result,
and propose open questions to be resolved.Comment: 4 pages, 4 figures; revised version accepted for publication in EP
Complex phase diagram and supercritical matter
Supercritical region is often described as uniform with no definite
transitions. The distinct behaviors of the matter therein, e.g., as liquid-like
and gas-like, however, indicate their should-be different belongings. Here, we
provide a mathematical description of these phenomena by revisiting the
Lee-Yang (LY) theory and using a complex phase diagram, e.g. a 4-D one with
complex and . Beyond the critical point, the 2-D phase diagram with real
and , i.e. the physical plane, is free of LY zeros and hence no
criticality emerges. But off-plane zeros in this 4-D scenario still come into
play by inducing critical anomalies for different physical properties. This is
evidenced by the correlation between the Widom lines and LY edges in van der
Waals model and water. The present distinct criteria to distinguish the
supercritical matter manifest the high-dimensional feature of the phase
diagram: e.g. when the LY zeros of complex or are projected onto the
physical plane, a boundary defined by isobaric heat capacity or adiabatic
compression coefficient emanates. These results demonstrate the incipient
phase transition nature of the supercritical matter
The Value of Backers’ Word-of-Mouth in Screening Crowdfunding Projects: An Empirical Investigation
Reward-based crowdfunding is an emerging financing channel for entrepreneurs to raise money for their innovative projects. How to screen the crowdfunding projects is critical for crowdfunding platform, project founder, and potential backers. This study aims to investigate whether backers’ word-of-mouth (WOM) is a valuable input to generate collective intelligence for project screening. Specially, we answer three questions. First, is backers’ WOM an effective signal for implementation performance of crowdfunding projects? Second, how do the WOM help screen projects during the fund-raising process? Third, which kind of comments (positive or negative) is more effective in screening crowdfunding projects? Research hypotheses were developed based on theories of collective intelligence and WOM communication. Using a cross section dataset and a panel dataset, we get the following findings. First, backers’ negative WOM can effectively predict project implementation performance, however positive WOM does not have that prediction power. The prediction power of positive and negative WOM differs significantly. One possible reason is that negative WOM does contain more information of project quality. Second, project with more accumulative negative WOM tend to attract fewer subsequent backers. However, accumulative positive WOM is not helpful for attracting more potential backers. We conclude that negative WOM is useful for project screening project, because it is a signal of project quality, and meanwhile it could prevent backers make subsequent investments
Self-Supervised Visual Representation Learning with Semantic Grouping
In this paper, we tackle the problem of learning visual representations from
unlabeled scene-centric data. Existing works have demonstrated the potential of
utilizing the underlying complex structure within scene-centric data; still,
they commonly rely on hand-crafted objectness priors or specialized pretext
tasks to build a learning framework, which may harm generalizability. Instead,
we propose contrastive learning from data-driven semantic slots, namely
SlotCon, for joint semantic grouping and representation learning. The semantic
grouping is performed by assigning pixels to a set of learnable prototypes,
which can adapt to each sample by attentive pooling over the feature and form
new slots. Based on the learned data-dependent slots, a contrastive objective
is employed for representation learning, which enhances the discriminability of
features, and conversely facilitates grouping semantically coherent pixels
together. Compared with previous efforts, by simultaneously optimizing the two
coupled objectives of semantic grouping and contrastive learning, our approach
bypasses the disadvantages of hand-crafted priors and is able to learn
object/group-level representations from scene-centric images. Experiments show
our approach effectively decomposes complex scenes into semantic groups for
feature learning and significantly benefits downstream tasks, including object
detection, instance segmentation, and semantic segmentation. Code is available
at: https://github.com/CVMI-Lab/SlotCon.Comment: Accepted at NeurIPS 202
On Crystal-Structure Matches in Solid-Solid Phase Transitions
The exploration of solid-solid phase transition (SSPT) suffers from the
uncertainty of how two crystal structures match. We devised a theoretical
framework to describe and classify crystal-structure matches (CSM). Such
description fully exploits the translational and rotational symmetries and is
independent of the choice of supercells. This is enabled by the use of the
Hermite normal form, an analog of reduced echelon form for integer matrices.
With its help, exhausting all CSMs is made possible, which goes beyond the
conventional optimization schemes. As a demonstration, our enumeration
algorithm unveils the long-sought concerted mechanisms in the martensitic
transformation of steel accounting for the most commonly observed
Kurdjumov-Sachs (KS) orientation relationship (OR) and the Nishiyama-Wassermann
OR. Especially, the predominance of KS OR is explained. Given the unprecedented
comprehensiveness and efficiency, our enumeration scheme provide a promising
strategy for SSPT mechanism research.Comment: main text: 6 pages, 4 figures; supplemental materials: 14 pages, 6
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