175 research outputs found
Knowledge Base Completion: Baselines Strike Back
Many papers have been published on the knowledge base completion task in the
past few years. Most of these introduce novel architectures for relation
learning that are evaluated on standard datasets such as FB15k and WN18. This
paper shows that the accuracy of almost all models published on the FB15k can
be outperformed by an appropriately tuned baseline - our reimplementation of
the DistMult model. Our findings cast doubt on the claim that the performance
improvements of recent models are due to architectural changes as opposed to
hyper-parameter tuning or different training objectives. This should prompt
future research to re-consider how the performance of models is evaluated and
reported
Augmentic Compositional Models for Knowledge Base Completion Using Gradient Representations
Neural models of Knowledge Base data have typically employed compositional representations of graph objects: entity and relation embeddings are systematically combined to evaluate the truth of a candidate Knowedge Base entry. Using a model inspired by Harmonic Grammar, we propose to tokenize triplet embeddings by subjecting them to a process of optimization with respect to learned well-formedness conditions on Knowledge Base triplets. The resulting model, known as Gradient Graphs, leads to sizable improvements when implemented as a companion to compositional models. Also, we show that the supracompositional triplet token embeddings it produces have interpretable properties that prove helpful in performing inference on the resulting triplet representations
A Survey on Knowledge Graphs: Representation, Acquisition and Applications
Human knowledge provides a formal understanding of the world. Knowledge
graphs that represent structural relations between entities have become an
increasingly popular research direction towards cognition and human-level
intelligence. In this survey, we provide a comprehensive review of knowledge
graph covering overall research topics about 1) knowledge graph representation
learning, 2) knowledge acquisition and completion, 3) temporal knowledge graph,
and 4) knowledge-aware applications, and summarize recent breakthroughs and
perspective directions to facilitate future research. We propose a full-view
categorization and new taxonomies on these topics. Knowledge graph embedding is
organized from four aspects of representation space, scoring function, encoding
models, and auxiliary information. For knowledge acquisition, especially
knowledge graph completion, embedding methods, path inference, and logical rule
reasoning, are reviewed. We further explore several emerging topics, including
meta relational learning, commonsense reasoning, and temporal knowledge graphs.
To facilitate future research on knowledge graphs, we also provide a curated
collection of datasets and open-source libraries on different tasks. In the
end, we have a thorough outlook on several promising research directions
Holographic flavor in theories with eight supercharges
We review the holographic duals of gauge theories with eight supercharges
obtained by adding very few flavors to pure supersymmetric Yang-Mills with
sixteen supercharges. Assuming a brane-probe limit, the gravity duals are
engineered in terms of probe branes (the so-called flavor brane) in the
background of the color branes. Both types of branes intersect on a given
subspace in which the matter is confined. The gauge theory dual is thus the
corresponding flavoring of the gauge theory with sixteen supercharges. Those
theories have in general a non-trivial phase structure; which is also captured
in a beautiful way by the gravity dual. Along the lines of the gauge/gravity
duality, we review also some of the results on the meson spectrum in the
different phases of the theories.Comment: Invited review submitted to IJMP
Infrared Dynamics of a Large N QCD Model, the Massless String Sector and Mesonic Spectra
A consistency check for any UV complete model for large N QCD should be,
among other things, the existence of a well-defined vector and scalar mesonic
spectra. In this paper, we use our UV complete model in type IIB string theory
to study the IR dynamics and use this to predict the mesonic spectra in the
dual type IIA side. The advantage of this approach is two-fold: not only will
this justify the consistency of the supergravity approach, but it will also
give us a way to compare the IR spectra and the model with the ones proposed
earlier by Sakai and Sugimoto. Interestingly, the spectra coming from the
massless stringy sector are independent of the UV physics, although the massive
string sector may pose certain subtleties regarding the UV contributions as
well as the mappings to actual QCD. Additionally, we find that a component of
the string landscape enters the picture: there are points in the landscape
where the spectra can be considerably improved over the existing results in the
literature. These points in the landscape in-turn also determine certain
background supergravity components and fix various pathologies that eventually
lead to a consistent low energy description of the theory.Comment: 47 pages, 7 pdf figures, 24 tables, JHEP format; Detailed mathematica
file of the computations is available on request; Version 2: Text elaborated,
typos corrected, a new appendix added to discuss the regimes of validity, and
a word in the abstract changed. Results unchanged. Final version to appear in
JHE
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