7,320 research outputs found
Phase transitions of the q-state Potts model on multiply-laced Sierpinski gaskets
We present an exact solution of the q-state Potts model on a class of
generalized Sierpinski fractal lattices. The model is shown to possess an
ordered phase at low temperatures and a continuous transition to the high
temperature disordered phase at any q>=1. Multicriticality is observed in the
presence of a symmetry-breaking field. Exact renormalization group analysis
yields the phase diagram of the model and a complete set of critical exponents
at various transitions.Comment: 6 pages, 6 figures; figures correcte
Snyder's Model -- de Sitter Special Relativity Duality and de Sitter Gravity
Between Snyder's quantized space-time model in de Sitter space of momenta and
the \dS special relativity on \dS-spacetime of radius with Beltrami
coordinates, there is a one-to-one dual correspondence supported by a minimum
uncertainty-like argument. Together with Planck length , should be a fundamental constant. They lead to a
dimensionless constant . These indicate that physics at these two scales should be dual to
each other and there is in-between gravity of local \dS-invariance
characterized by . A simple model of \dS-gravity with a gauge-like action on
umbilical manifolds may show these characters. It can pass the observation
tests and support the duality.Comment: 32 page
Newton-Hooke Limit of Beltrami-de Sitter Spacetime, Principles of Galilei-Hooke's Relativity and Postulate on Newton-Hooke Universal Time
Based on the Beltrami-de Sitter spacetime, we present the Newton-Hooke model
under the Newton-Hooke contraction of the spacetime with respect to the
transformation group, algebra and geometry. It is shown that in Newton-Hooke
space-time, there are inertial-type coordinate systems and inertial-type
observers, which move along straight lines with uniform velocity. And they are
invariant under the Newton-Hooke group. In order to determine uniquely the
Newton-Hooke limit, we propose the Galilei-Hooke's relativity principle as well
as the postulate on Newton-Hooke universal time. All results are readily
extended to the Newton-Hooke model as a contraction of Beltrami-anti-de Sitter
spacetime with negative cosmological constant.Comment: 25 pages, 3 figures; some misprints correcte
What determines pension insurance participation in China?: triangulation and the intertwined relationship among employers, employees and the government
The current study draws on the Advocacy Coalition Framework to examine what determines employees’ pension participation in China. For the purpose of exploring which employees actually receive pension coverage and why, econometric analysis was conducted with China’s Employer–Employee Matched Survey data (N = 3412). A variety of both individual factors, ranging from age and Hukou status to job characteristics, and macro factors, including interprovincial migration and level of economic development, are all found to predict insurance coverage. Qualitative research results contextualize these findings by discussing the often ambivalent and triangulated relations among employers, employees and government. These three groups primarily use shared core policy beliefs to structure their interactions in the form of advocacy coalitions. Various types of cross-coalition interaction, including negotiation, cooperation and conflict, are examined. These findings carry both theoretical and policy implications
Knowledge-driven Meta-learning for CSI Feedback
Accurate and effective channel state information (CSI) feedback is a key
technology for massive multiple-input and multiple-output systems. Recently,
deep learning (DL) has been introduced for CSI feedback enhancement through
massive collected training data and lengthy training time, which is quite
costly and impractical for realistic deployment. In this article, a
knowledge-driven meta-learning approach is proposed, where the DL model
initialized by the meta model obtained from meta training phase is able to
achieve rapid convergence when facing a new scenario during target retraining
phase. Specifically, instead of training with massive data collected from
various scenarios, the meta task environment is constructed based on the
intrinsic knowledge of spatial-frequency characteristics of CSI for meta
training. Moreover, the target task dataset is also augmented by exploiting the
knowledge of statistical characteristics of wireless channel, so that the DL
model can achieve higher performance with small actually collected dataset and
short training time. In addition, we provide analyses of rationale for the
improvement yielded by the knowledge in both phases. Simulation results
demonstrate the superiority of the proposed approach from the perspective of
feedback performance and convergence speed.Comment: arXiv admin note: text overlap with arXiv:2301.1347
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