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Cats Climb Entails Mammals Move: Preserving Hyponymy in Compositional Distributional Semantics
( Gemma De Las Cuevas ),( Andreas Klingler ),( Martha Lewis ),( Tim Netzer ) 서울대학교 인지과학연구소 2021 Journal of Cognitive Science Vol.22 No.3
To give vector-based representations of meaning more structure, an approach proposed in Piedeleu et al. (2015); Sadrzadeh et al. (2018); Bankova et al. (2018) is to use positive semidefinite (psd) matrices. These allow us to model similarity of words as well as the hyponymy or is-a relationship. To compose words to form phrases and sentences, we may represent adjectives, verbs, and other functional words as multilinear, positivity preserving maps, following the compositional distributional approach introduced in Coecke et al. (2010) and extended to the realm of psd matrices in Piedeleu et al. (2015), but it is not clear how to learn representations of functional words when working with psd matrices. In this paper, we introduce a generic way of composing the psd matrices corresponding to words. We propose that psd matrices for verbs, adjectives, and other functional words be lifted to completely positive (CP) maps that match their grammatical type. This lifting is carried out by our composition rule called Compression, Compr. In contrast to previous composition rules like Fuzz and Phaser (Coecke and Meichanetzidis, 2020) (a.k.a. KMult and BMult (Lewis, 2019a)), Compr preserves hyponymy. Mathematically, Compr is itself a CP map, and is therefore linear and generally non-commutative. We give a number of proposals for the structure of Compr, based on spiders, cups, and caps, and generate a range of composition rules. We test these rules on sentence entailment datasets from Kartsaklis and Sadrzadeh (2016), and see some improvements over the performance of Fuzz and Phaser. We go on to estimate the parameters of a simplified form of Compr based on entailment information from the aforementioned datasets, and find that whilst this learnt operator does not consistently outperform previously proposed mechanisms, it is competitive and has the potential to improve with the use of a less simplified version.
Goad, M. R.,Korista, K. T.,Rosa, G. De,Kriss, G. A.,Edelson, R.,Barth, A. J.,Ferland, G. J.,Kochanek, C. S.,Netzer, H.,Peterson, B. M.,Bentz, M. C.,Bisogni, S.,Crenshaw, D. M.,Denney, K. D.,Ely, J.,Fa American Astronomical Society 2016 The Astrophysical journal Vol.824 No.1
<P>During an intensive Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS) UV monitoring campaign of the Seyfert 1 galaxy NGC 5548 performed from 2014 February to July, the normally highly correlated far UV continuum and broad emission line variations decorrelated for similar to 60-70 days, starting similar to 75 days after the first HST/COS observation. Following this anomalous state, the flux and variability of the broad emission lines returned to a more normal state. This transient behavior, characterized by significant deficits in flux and equivalent width of the strong broad UV emission lines, is the first of its kind to be unambiguously identified in an active galactic nucleus reverberation mapping campaign. The largest corresponding emission line flux deficits occurred for the high ionization, collisionally excited lines C IV and Si IV(+O IV]), and also He II(+O III]), while the anomaly in Ly alpha was substantially smaller. This pattern of behavior indicates a depletion in the flux of photons with E-ph > 54 eV relative to those near 13.6 eV. We suggest two plausible mechanisms for the observed behavior: (i) temporary obscuration of the ionizing continuum incident upon broad line region (BLR) clouds by a moving veil of material lying between the inner accretion disk and inner (BLR), perhaps resulting from an episodic ejection of material from the disk, or (ii) a temporary change in the intrinsic ionizing continuum spectral energy distribution resulting in a deficit of ionizing photons with energies > 54 eV, possibly due to a transient restructuring of the Comptonizing atmosphere above the disk. Current evidence appears to favor the latter explanation.</P>