1,369 research outputs found
Bethe Ansaetze for GKP strings
Studying the scattering of excitations around a dynamical background has a
long history in the context of integrable models. The Gubser-Klebanov-Polyakov
string solution provides such a background for the string/gauge correspondence.
Taking the conjectured all-loop asymptotic equations for the AdS_4/CFT_3
correspondence as the starting point, we derive the S-matrix and a set of
spectral equations for the lowest-lying excitations. We find that these
equations resemble closely the analogous equations for AdS_5/CFT_4, which are
also discussed in this paper. At large values of the coupling constant we show
that they reproduce the Bethe equations proposed to describe the spectrum of
the low-energy limit of the AdS_4xCP^3 sigma model.Comment: 60 pages, 5 figure
Nesting and Dressing
We compute the anomalous dimensions of field strength operators Tr F^L in N=4
SYM from an asymptotic nested Bethe ansatz to all-loop order. Starting from the
exact solution of the one-loop problem at arbitrary L, we derive a single
effective integral equation for the thermodynamic limit of these dimensions. We
also include the recently proposed phase factor for the S-matrix of the planar
AdS/CFT system. The terms in the effective equation corresponding to,
respectively, the nesting and the dressing are structurally very similar. This
hints at the physical origin of the dressing phase, which we conjecture to
arise from the hidden presence of infinitely many auxiliary Bethe roots
describing a non-trivial "filled" structure of the theory's BPS vacuum. We
finally show that the mechanism for creating effective nesting/dressing kernels
is quite generic by also deriving the integral equation for the all-loop
dimension of a certain one-loop so(6) singlet state.Comment: 38 pages, 2 figures. v2: References and appendix discussing the
emulation of the dressing phase adde
Unimodal bilingualism in the Deaf community: Language contact between two sign languages in Australia and the United Kingdom
Little is known about unimodal sign bilingualism: whether it resembles unimodal (spoken) bilingualism, or bimodal (spoken and signed) bilingualism, or whether it has unique qualities. This study is the first to examine this topic through a study of bilingualism in two Deaf communities in which dialects of unrelated languages: British Sign Language (BSL) and Irish Sign Language (ISL) are used. The research looks at previously unexplored aspects of code-blending and code-mixing, and compares the data with data on bimodal bilingualism (in a signed and a spoken language) and unimodal bilingualism (in two spoken languages) with a combination of experimental and naturalistic data. The experimental study used a picture naming task. Eleven participants were asked to name pictures as quickly as possible, and response latencies were analysed. It was found that there was indeed a switching cost, which did not appear to be asymmetrical. There was also a cognate facilitation effect. The second part of the study was based on interviews with bilinguals. As well as phenomena already described for unimodal spoken language bilingualism, including code-switching and code mixing, the study reports on mouthing, where spoken mouth patterns (in this case English) are produced simultaneously with manual signs. These are usually considered examples of code-blending, reflecting active mixing of two languages. This study provides an initial understanding of how modality interacts with bilingualism and suggests the need for further explorations
Review of AdS/CFT Integrability, Chapter I.3: Long-range spin chains
In this contribution we briefly review recent developments in the theory of
long-range integrable spin chains. These spin chains constitute a natural
generalisation of the well-studied integrable nearest-neighbour chains and are
of particular relevance to the integrability in the AdS/CFT correspondence
since the dilatation operator in the asymptotic region is conjectured to be a
Hamiltonian of an integrable long-range psu spin chain.Comment: 17 pages, see also overview article arXiv:1012.3982, v2: references
to other chapters updated, v3: minor typos corrected, references adde
The Yangian of sl(n|m) and the universal R-matrix
In this paper we study Yangians of sl(n|m) superalgebras. We derive the
universal R-matrix and evaluate it on the fundamental representation obtaining
the standard Yang R-matrix with unitary dressing factors. For m=0, we directly
recover up to a CDD factor the well-known S-matrices for relativistic
integrable models with su(N) symmetry. Hence, the universal R-matrix found
provides an abstract plug-in formula, which leads to results obeying
fundamental physical constraints: crossing symmetry, unitrarity and the
Yang-Baxter equation. This implies that the Yangian double unifies all desired
symmetries into one algebraic structure. In particular, our analysis is valid
in the case of sl(n|n), where one has to extend the algebra by an additional
generator leading to the algebra gl(n|n). We find two-parameter families of
scalar factors in this case and provide a detailed study for gl(1|1).Comment: 24 pages, 2 figure
Asymptotic Properties of Difference Equations for Isotropic Loop Quantum Cosmology
In loop quantum cosmology, a difference equation for the wave function
describes the evolution of a universe model. This is different from the
differential equations that arise in Wheeler-DeWitt quantizations, and some
aspects of general properties of solutions can appear differently. Properties
of particular interest are boundedness and the presence of small-scale
oscillations. Continued fraction techniques are used to show in different
matter models the presence of special initial conditions leading to bounded
solutions, and an explicit expression for these initial values is derived.Comment: 27 pages, 2 figure
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