8,408 research outputs found
Asymptotic Bethe Ansatz on the GKP vacuum as a defect spin chain: scattering, particles and minimal area Wilson loops
Moving from Beisert-Staudacher equations, the complete set of Asymptotic
Bethe Ansatz equations and -matrix for the excitations over the GKP vacuum
is found. The resulting model on this new vacuum is an integrable spin chain of
length ( spin) with particle rapidities as inhomogeneities, two
(purely transmitting) defects and (residual R-)symmetry. The
non-trivial dynamics of SYM appears in elaborated dressing factors
of the 2D two-particle scattering factors, all depending on the 'fundamental'
one between two scalar excitations. From scattering factors we determine bound
states. In particular, we study the strong coupling limit, in the
non-perturbative, perturbative and giant hole regimes. Eventually, from these
scattering data we construct the pentagon transition amplitudes
(perturbative regime). In this manner, we detail the multi-particle
contributions (flux tube) to the MHV gluon scattering amplitudes/Wilson loops
(OPE or BSV series) and re-sum them to the Thermodynamic Bubble Ansatz.Comment: 103 pages; typos corrected, references added: journal versio
On the scattering over the GKP vacuum
By converting the Asymptotic Bethe Ansatz (ABA) of SYM into
non-linear integral equations, we find 2D scattering amplitudes of excitations
on top of the GKP vacuum. We prove that this is a suitable and powerful set-up
for the understanding and computation of the whole S-matrix. We show that all
the amplitudes depend on the fundamental scalar-scalar one.Comment: final version, 14 pages, to appear in Physics Letters
Topology of Scrapbooking : Browsing Through a Space in Constant Transformation
The essay sheds light on the practice of scrapbooking promoting a spatial reflection. Topology is used as a tool for exploration and stimulates an investigation in terms of movement and morphological deformations. The topological references, along with three examples of artist scrapbooking, enable tangent reflections that depict a multifaceted contemporary scrapscape with profound design, cultural, and media value. Scrapbooking emerges as a metamorphic threshold practice between the private and the public, capable of empowering the ephemeral and questioning ever-moving constructions such as culture and identity, both visually and materially
Understanding the underlying mechanisms and the role that pre-harvest horticultural maturity, agronomic factors and growing conditions have on postharvest discolouration in celery
Celery is a foliage crop which is commonly consumed for its fresh stalks, which are
sold on the market in various retail formats. Celery is appreciated by consumers for its
freshness, bright green colour, crisp texture, low calorific content and health promoting
properties. An important problem affecting this crop after harvest is browning at cut
ends, which is a physiological “disorder” manifesting with brown/black stains on cut or
damaged surfaces. It manifests during handling and processing of vegetables, which is
the phase where most of the postharvest damage occurs. Cut-end browning is believed
to be due to the activity of two enzymes; polyphenol-oxidase (PPO) and phenylalanine
ammonia-lyase (PAL). These two enzymes synergistically act to produce melanins,
which are the pigments responsible for the black/brown appearance. This is a relevant
economic issue as discoloured celery tends to be rejected by retailers, with negative
implications for the growers and the UK fresh produce industry. Postharvest browning
is not thought to be due to the activity of fungi or bacteria, yet the blackening of
surfaces suggests to customers that the product is decaying.
Research has been conducted to understand which postharvest factors can influence
browning in celery. It has been shown that the use of controlled atmosphere (Gomez
and Artes, 2004), heat shock treatments (Loaiza-Velarde et al., 2003) and postharvest
application of high intensity light (Zhan et al., 2013) were effective in reducing
incidence of the problem. On the other hand, research on pre-harvest factors is still
scarce. The aim of the present work was to: 1-) investigate which agronomic factors can
affect the severity of postharvest browning in celery; 2-) provide a better understanding
of the underlying physiological and biochemical mechanisms involved in this
“disorder”.
Results showed that agronomic practices can affect postharvest browning in celery.
Harvesting at late maturity stages and irrigating below the normal requirements
increased postharvest discolouration in this crop. Additionally, the browning
mechanism does not seem to be mediated by ethylene in celery. Further biochemical
analysis on phenolic compounds and enzymatic activity (PPO and PAL) need to be
performed to provide a better elucidation of the browning reaction in this crop
Spherical clustering of users navigating 360{\deg} content
In Virtual Reality (VR) applications, understanding how users explore the
omnidirectional content is important to optimize content creation, to develop
user-centric services, or even to detect disorders in medical applications.
Clustering users based on their common navigation patterns is a first direction
to understand users behaviour. However, classical clustering techniques fail in
identifying these common paths, since they are usually focused on minimizing a
simple distance metric. In this paper, we argue that minimizing the distance
metric does not necessarily guarantee to identify users that experience similar
navigation path in the VR domain. Therefore, we propose a graph-based method to
identify clusters of users who are attending the same portion of the spherical
content over time. The proposed solution takes into account the spherical
geometry of the content and aims at clustering users based on the actual
overlap of displayed content among users. Our method is tested on real VR user
navigation patterns. Results show that our solution leads to clusters in which
at least 85% of the content displayed by one user is shared among the other
users belonging to the same cluster.Comment: 5 pages, conference (Published in: ICASSP 2019 - 2019 IEEE
International Conference on Acoustics, Speech and Signal Processing (ICASSP)
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