Semi-Supervised Learning for Neural Keyphrase Generation

We study the problem of generating keyphrases that summarize the key points for a given document. While sequence-to-sequence (seq2seq) models have achieved remarkable performance on this task (Meng et al., 2017), model training often relies on large amounts of labeled data, which is only applicable to resource-rich domains. In this paper, we propose semi-supervised keyphrase generation methods by leveraging both labeled data and large-scale unlabeled samples for learning. Two strategies are proposed. First, unlabeled documents are first tagged with synthetic keyphrases obtained from unsupervised keyphrase extraction methods or a selflearning algorithm, and then combined with labeled samples for training. Furthermore, we investigate a multi-task learning framework to jointly learn to generate keyphrases as well as the titles of the articles. Experimental results show that our semi-supervised learning-based methods outperform a state-of-the-art model trained with labeled data only.Comment: To appear in EMNLP 2018 (12 pages, 7 figures, 6 tables

Stabilizing Non-Hermitian Systems by Periodic Driving

The time evolution of a system with a time-dependent non-Hermitian Hamiltonian is in general unstable with exponential growth or decay. A periodic driving field may stabilize the dynamics because the eigenphases of the associated Floquet operator may become all real. This possibility can emerge for a continuous range of system parameters with subtle domain boundaries. It is further shown that the issue of stability of a driven non-Hermitian Rabi model can be mapped onto the band structure problem of a class of lattice Hamiltonians. As an application, we show how to use the stability of driven non-Hermitian two-level systems (0-dimension in space) to simulate a spectrum analogous to Hofstadter's butterfly that has played a paradigmatic role in quantum Hall physics. The simulation of the band structure of non-Hermitian superlattice potentials with parity-time reversal symmetry is also briefly discussed

Next-to-next-to-leading order NN-jettiness soft function for tWtW production

We calculate the $N$-jettiness soft function for $tW$ production up to next-to-next-to-leading order in QCD, which is an important ingredient of the $N$-jettiness subtraction method for predicting the differential cross sections of massive coloured particle productions. The divergent parts of the results have been checked using the renormalization group equations controlled by the soft anomalous dimension.Comment: 14 pages, 3 figures, published version in PL

Doping dependence of the upper critical field in La_{2-x}Sr_xCuO_4 from specific heat

The low-temperature specific heat of La_{2-x}Sr_xCuO_4 (LSCO) single crystals in magnetic field H up to 12 T has been examined over a wide range of doping (0.063=< p =<0.238). From this we have mapped the upper critical field H_{c2} of LSCO across the entire superconducting diagram. It is found that the H_{c2} shows a doping dependence similar to that of the critical temperature T_c. We have discussed the implications of the result and proposed that there may be an effective superconducting energy scale responsible for the H_{c2} behavior in the underdoped region.Comment: 6 pages,3 figures,1 tabl

Characterization and properties of weakly optimal entanglement witnesses

We present an analysis of the properties and characteristics of weakly optimal entanglement witnesses, that is witnesses whose expectation value vanishes on at least one product vector. Any weakly optimal entanglement witness can be written as the form of $W^{wopt}=\sigma-c_{\sigma}^{max} I$, where $c_{\sigma}^{max}$ is a non-negative number and $I$ is the identity matrix. We show the relation between the weakly optimal witness $W^{wopt}$ and the eigenvalues of the separable states $\sigma$. Further we give an application of weakly optimal witnesses for constructing entanglement witnesses in a larger Hilbert space by extending the result of [P. Badzi\c{a}g {\it et al}, Phys. Rev. A {\bf 88}, 010301(R) (2013)], and we examine their geometric properties.Comment: 13 pages, 2 figures, has been extensively redrafted and restructure