On factorizing FF-matrices in Y(sln)Y(sl_n) and Uq(sln^)U_q(\hat{sl_n}) spin chains

We consider quantum spin chains arising from $N$-fold tensor products of the fundamental evaluation representations of $Y(sl_n)$ and $U_q(\hat{sl_n})$. Using the partial $F$-matrix formalism from the seminal work of Maillet and Sanchez de Santos, we derive a completely factorized expression for the $F$-matrix of such models and prove its equivalence to the expression obtained by Albert, Boos, Flume and Ruhlig. A new relation between the $F$-matrices and the Bethe eigenvectors of these spin chains is given.Comment: 30 page

The colours of food: final layer in the Palimpsest of Santa Caterina Market in Barcelona

The colours and shapes of food in the decoration of a building were common in traditional architecture, particularly in the Spanish regions of Catalonia and Valencia in the nineteenth century. During the modernist period, we can distinguish both an abstract and a mimetic tendency in these colour transfers. Coloured glazed tiles were often used to cover modernist public buildings in the Spanish Mediterranean coast. The roof of Santa Caterina market in Barcelona follows this abstract modernist tradition and starts from the picture of a food stall as an inspiration. In the same way as some other contemporary architects, Enric Miralles and Benedetta Tagliabue used a computer-aided process of pixilation to design a shiny coloured composition that reminds us of traditional colour transfer techniques from nature and traditional building materials. The result is a market conceived as a palimpsest in which various historical layers from the past can be read. Moreover, it represents in a virtual manner the chromatic experiences that take place in the spaces inside. The building features a type of transparency that is consistent with contemporary perception and which blurs the boundaries between reality and fiction. Food has been a prominent inspiration throughout history for many artistic disciplines and was used as an argument to experiment with colour. The presence of food as a decorative element in architecture goes beyond a simple functional relationship with the use of rooms, and becomes a useful motive for organising a chromatic composition. Examples include coloured cornucopias of classical architecture, biblical food goods in the frescoes of medieval architecture (grapes, bread, fish, etc.), still life paintings in bourgeois housing, or the glazed ceramics used in modernist market buildings.Postprint (published version

Non compact continuum limit of two coupled Potts models

We study two $Q$-state Potts models coupled by the product of their energy operators, in the regime $2 < Q \le 4$ where the coupling is relevant. A particular choice of weights on the square lattice is shown to be equivalent to the integrable $a_3^{(2)}$ vertex model. It corresponds to a selfdual system of two antiferromagnetic Potts models, coupled ferromagnetically. We derive the Bethe Ansatz equations and study them numerically for two arbitrary twist angles. The continuum limit is shown to involve two compact bosons and one non compact boson, with discrete states emerging from the continuum at appropriate twists. The non compact boson entails strong logarithmic corrections to the finite-size behaviour of the scaling levels, the understanding of which allows us to correct an earlier proposal for some of the critical exponents. In particular, we infer the full set of magnetic scaling dimensions (watermelon operators) of the Potts model.Comment: 33 pages, 10 figures v2: reference added, minor typo corrected v3: revised version for publication in JSTAT: section 3.1 added, some technical content moved to appendi

Target recognitions in multiple camera CCTV using colour constancy

People tracking using colour feature in crowded scene through CCTV network have been a popular and at the same time a very difficult topic in computer vision. It is mainly because of the difficulty for the acquisition of intrinsic signatures of targets from a single view of the scene. Many factors, such as variable illumination conditions and viewing angles, will induce illusive modification of intrinsic signatures of targets. The objective of this paper is to verify if colour constancy (CC) approach really helps people tracking in CCTV network system. We have testified a number of CC algorithms together with various colour descriptors, to assess the efficiencies of people recognitions from real multi-camera i-LIDS data set via Receiver Operating Characteristics (ROC). It is found that when CC is applied together with some form of colour restoration mechanisms such as colour transfer, the recognition performance can be improved by at least a factor of two. An elementary luminance based CC coupled with a pixel based colour transfer algorithm, together with experimental results are reported in the present paper

Four-Quark Effective Operators at Hadron Colliders

The robustness of translating effective operator constraints to BSM theories crucially depends on the mass and coupling of BSM particles. This is especially relevant for hadron colliders where the partonic centre of mass energy is around the typical energy scales of natural BSM theories. The caveats in applying the limits are discussed using Z' and G' models, illustrating the effects for a large class of models. This analysis shows that the applicability of effective operators mainly depends on the ratio of the transfer energy in the events and the mass scale of the full theory. Moreover, based on these results a method is developed to recast existing experimental limits on four-quark effective operators to the full theory parameter space.Comment: 28 pages, 10 figures, version 2 updated to JHEP 03 (2015) 09