86 research outputs found
REL: An Entity Linker Standing on the Shoulders of Giants
Entity linking is a standard component in modern retrieval system that is
often performed by third-party toolkits. Despite the plethora of open source
options, it is difficult to find a single system that has a modular
architecture where certain components may be replaced, does not depend on
external sources, can easily be updated to newer Wikipedia versions, and, most
important of all, has state-of-the-art performance. The REL system presented in
this paper aims to fill that gap. Building on state-of-the-art neural
components from natural language processing research, it is provided as a
Python package as well as a web API. We also report on an experimental
comparison against both well-established systems and the current
state-of-the-art on standard entity linking benchmarks
Lattice artefacts and the running of the coupling constant
We study the running of the L\"uscher-Weisz-Wolff (LWW) coupling constant in
the two dimensional O(3) nonlinear model. To investigate the continuum
limit we refine the lattice spacing from the value used by LWW up
to . We find that the lattice artefacts are much larger than
estimated by LWW and that most likely the coupling constant runs slower than
predicted by perturbation theory. A precise determination of the running in the
continuum limit would require a controlled ansatz of extrapolation, which, we
argue, is not presently available.Comment: 4 pages, 4 figures. To address the criticism that we are studying a
different quantitiy than Luscher, Weisz and Wolff originally did, we
introduced a new equation (2), a new paragraph discussing this issue and a
new figure comparing the results obtained with our prescription to that
obtained with the original one of Luscher, Weisz and Wolf
On the Classification of Real Forms of Non-Abelian Toda Theories and W-algebras
We consider conformal non-Abelian Toda theories obtained by hamiltonian
reduction from Wess-Zumino-Witten models based on general real Lie groups. We
study in detail the possible choices of reality conditions which can be imposed
on the WZW or Toda fields and prove correspondences with sl(2,R) embeddings
into real Lie algebras and with the possible real forms of the associated
W-algebras. We devise a a method for finding all real embeddings which can be
obtained from a given embedding of sl(2,C) into a complex Lie algebra. We then
apply this to give a complete classification of real embeddings which are
principal in some simple regular subalgebra of a classical Lie algebra.Comment: 42 pages, LaTeX; Minor corrections to ensure consistent conventions;
some references adde
Strings on type IIB pp-wave backgrounds with interacting massive theories on the worldsheet
We consider superstring theories on pp-wave backgrounds which result in an
integrable supersymmetric Landau-Ginzburg theory on the
worldsheet. We obtain exact eigenvalues of the light-cone gauge superstring
hamiltonian in the massive and interacting world-sheet theory with
superpotential . We find the modes of the supergravity part of the
string spectrum, and their space-time interpretation. Because the system is
effectively at strong coupling on the worldsheet, these modes are not in
one-to-one correspondence with the usual type IIB supergravity modes in the
limit. However, the above correspondence holds in the limit.Comment: 20 pages, 1 figure; minor changes, comments adde
The BRST quantization and the no-ghost theorem for AdS_3
In our previous papers, we prove the no-ghost theorem without light-cone
directions (hep-th/0005002, hep-th/0303051). We point out that our results are
valid for more general backgrounds. In particular, we prove the no-ghost
theorem for AdS_3 in the context of the BRST quantization (with the standard
restriction on the spin). We compare our BRST proof with the OCQ proof and
establish the BRST-OCQ equivalence for AdS_3. The key in both approaches lies
in the certain structure of the matter Hilbert space as a product of two Verma
modules. We also present the no-ghost theorem in the most general form.Comment: 22 pages, JHEP and AMS-LaTeX; v2 & 3: minor improvement
Local conserved charges in principal chiral models
Local conserved charges in principal chiral models in 1+1 dimensions are
investigated. There is a classically conserved local charge for each totally
symmetric invariant tensor of the underlying group. These local charges are
shown to be in involution with the non-local Yangian charges. The Poisson
bracket algebra of the local charges is then studied. For each classical
algebra, an infinite set of local charges with spins equal to the exponents
modulo the Coxeter number is constructed, and it is shown that these commute
with one another. Brief comments are made on the evidence for, and implications
of, survival of these charges in the quantum theory.Comment: 36 pages, LaTeX; v2: minor correction
Conserved charges and supersymmetry in principal chiral and WZW models
Conserved and commuting charges are investigated in both bosonic and
supersymmetric classical chiral models, with and without Wess-Zumino terms. In
the bosonic theories, there are conserved currents based on symmetric invariant
tensors of the underlying algebra, and the construction of infinitely many
commuting charges, with spins equal to the exponents of the algebra modulo its
Coxeter number, can be carried out irrespective of the coefficient of the
Wess-Zumino term. In the supersymmetric models, a different pattern of
conserved quantities emerges, based on antisymmetric invariant tensors. The
current algebra is much more complicated than in the bosonic case, and it is
analysed in some detail. Two families of commuting charges can be constructed,
each with finitely many members whose spins are exactly the exponents of the
algebra (with no repetition modulo the Coxeter number). The conserved
quantities in the bosonic and supersymmetric theories are only indirectly
related, except for the special case of the WZW model and its supersymmetric
extension.Comment: LaTeX; 49 pages; v2: minor changes and additions to text and ref
BRST Quantization of String Theory in AdS(3)
We study the BRST quantization of bosonic and NSR strings propagating in
AdS(3) x N backgrounds. The no-ghost theorem is proved using the
Frenkel-Garland-Zuckerman method. Regular and spectrally-flowed representations
of affine SL(2,R) appear on an equal footing. Possible generalizations to
related curved backgrounds are discussed.Comment: JHEP style, 23 pages; v2:minor changes and references added; v3:
typos corrected, version to appear in JHEP; v4: one reference adde
Thermodynamic Bethe Ansatz for the AdS_5 x S^5 Mirror Model
We use the string hypothesis for the mirror theory to derive the
Thermodynamic Bethe Ansatz equations for the AdS_5 x S^5 mirror model. We
further demonstrate how these equations can be used to construct the associated
Y-system recently discussed in the literature, putting particular emphasis on
the assumptions and the range of validity of the corresponding construction.Comment: 31 pages, LaTex, v2: references added, v3: published versio
Superstrings on NS5 backgrounds, deformed AdS3 and holography
We study a non-standard decoupling limit of the D1/D5-brane system, which
interpolates between the near-horizon geometry of the D1/D5 background and the
near-horizon limit of the pure D5-brane geometry. The S-dual description of
this background is actually an exactly solvable two-dimensional (worldsheet)
conformal field theory: {null-deformed SL(2,R)} x SU(2) x T^4 or K3. This model
is free of strong-coupling singularities. By a careful treatment of the
SL(2,R), based on the better-understood SL(2,R) / U(1) coset, we obtain the
full partition function for superstrings on SL(2,R) x SU(2) x K3. This allows
us to compute the partition functions for the J^3 and J^2 current-current
deformations, as well as the full line of supersymmetric null deformations,
which links the SL(2,R) conformal field theory with linear dilaton theory. The
holographic interpretation of this setup is a renormalization-group flow
between the decoupled NS5-brane world-volume theory in the ultraviolet (Little
String Theory), and the low-energy dynamics of super Yang--Mills string-like
instantons in six dimensions.Comment: JHEP style, 59 pages, 1 figure; v2: minor changes, to appear in JHE
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