156 research outputs found
Canonical explicit B\"{a}cklund transformations with spectrality for constrained flows of soliton hierarchies
It is shown that explicit B\"{a}cklund transformations (BTs) for the
high-order constrained flows of soliton hierarchy can be constructed via their
Darboux transformations and Lax representation, and these BTs are canonical
transformations including B\"{a}cklund parameter and possess a
spectrality property with respect to and the 'conjugated' variable
for which the pair lies on the spectral curve. As model we
present the canonical explicit BTs with the spectrality for high-order
constrained flows of the Kaup-Newell hierarchy and the KdV hierarchy.Comment: 21 pages, Latex, to be published in "PHYSICA A
Deriving N-soliton solutions via constrained flows
The soliton equations can be factorized by two commuting x- and t-constrained
flows. We propose a method to derive N-soliton solutions of soliton equations
directly from the x- and t-constrained flows.Comment: 8 pages, AmsTex, no figures, to be published in Journal of Physics
Constructing N-soliton solution for the mKdV equation through constrained flows
Based on the factorization of soliton equations into two commuting integrable
x- and t-constrained flows, we derive N-soliton solutions for mKdV equation via
its x- and t-constrained flows. It shows that soliton solution for soliton
equations can be constructed directly from the constrained flows.Comment: 10 pages, Latex, to be published in "J. Phys. A: Math. Gen.
The relation between the Toda hierarchy and the KdV hierarchy
Under three relations connecting the field variables of Toda flows and that
of KdV flows, we present three new sequences of combination of the equations in
the Toda hierarchy which have the KdV hierarchy as a continuous limit. The
relation between the Poisson structures of the KdV hierarchy and the Toda
hierarchy in continuous limit is also studied.Comment: 11 pages, Tex, no figures, to be published in Physics Letters
Contrastive Learning with Prompt-derived Virtual Semantic Prototypes for Unsupervised Sentence Embedding
Contrastive learning has become a new paradigm for unsupervised sentence
embeddings. Previous studies focus on instance-wise contrastive learning,
attempting to construct positive pairs with textual data augmentation. In this
paper, we propose a novel Contrastive learning method with Prompt-derived
Virtual semantic Prototypes (ConPVP). Specifically, with the help of prompts,
we construct virtual semantic prototypes to each instance, and derive negative
prototypes by using the negative form of the prompts. Using a prototypical
contrastive loss, we enforce the anchor sentence embedding to be close to its
corresponding semantic prototypes, and far apart from the negative prototypes
as well as the prototypes of other sentences. Extensive experimental results on
semantic textual similarity, transfer, and clustering tasks demonstrate the
effectiveness of our proposed model compared to strong baselines. Code is
available at https://github.com/lemon0830/promptCSE.Comment: Findings of EMNLP 202
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