4,990 research outputs found
-Poincar\'e supersymmetry in
We consider the exact S-matrix governing the planar spectral problem for
strings on and super Yang-Mills, and we show
that it is invariant under a novel "boost" symmetry, which acts as a
differentiation with respect to the particle momentum. This generator leads us
also to reinterpret the usual centrally extended
symmetry, and to conclude that the S-matrix is invariant under a -Poincar\'e
supersymmetry algebra, where the deformation parameter is related to the 't
Hooft coupling. We determine the two-particle action (coproduct) that turns out
to be non-local, and study the property of the new symmetry under crossing
transformations. We look at both the strong-coupling (large tension in the
string theory) and weak-coupling (spin-chain description of the gauge theory)
limits; in the former regime we calculate the cobracket utilising the universal
classical r-matrix of Beisert and Spill. In the eventuality that the boost has
higher partners, we also construct a quantum affine version of 2D Poincar\'e
symmetry, by contraction of the quantum affine algebra
in Drinfeld's second realisation.Comment: 35 pages. Added discussion on antipode in the presence of the phase.
Published versio
-Poincar\'e invariance of the -matrix
We consider the exact -matrix of , which is the building
block for describing the scattering of worldsheet excitations of the light-cone
gauge-fixed backgrounds and with pure Ramond-Ramond fluxes. We show that is
invariant under a "deformed boost" symmetry, for which we write an explicit
exact coproduct, i.e. its action on 2-particle states. When we include the
boost, the symmetries of the -matrix close into a -Poincar\'e
superalgebra. Our findings suggest that the recently discovered boost
invariance in may be a common feature of systems that
are treatable with the exact techniques of integrability. With the aim of going
towards a universal formulation of the underlying Hopf algebra, we also propose
a universal form of the classical -matrix.Comment: 26 pages. Minor improvements and references added. Published versio
Puzzles of eta-deformed AdS_5 x S^5
We derive the part of the Lagrangian for the sigma model on the eta-deformed
AdS_5 x S^5 space which is quadratic in fermions and has the full dependence on
bosons. We then show that there exists a field redefinition which brings the
corresponding Lagrangian to the standard form of type IIB Green-Schwarz
superstring. Reading off the corresponding RR couplings, we observe that they
fail to satisfy the supergravity equations of motion, despite the presence of
kappa-symmetry. However, in a special scaling limit our solution reproduces the
supergravity background found by Maldacena and Russo. Further, using the
fermionic Lagrangian, we compute a number of new matrix elements of the tree
level world-sheet scattering matrix. We then show that after a unitary
transformation on the basis of two-particle states which is not one-particle
factorisable, the corresponding T-matrix factorises into two equivalent parts.
Each part satisfies the classical Yang-Baxter equation and coincides with the
large tension limit of the q-deformed S-matrix.Comment: 59 pages, 1 figure, v2: minor correction
All-loop Bethe ansatz equations for AdS3/CFT2
Using the S-matrix for the d(2,1;alpha)^2 symmetric spin-chain of AdS3/CFT2,
we propose a new set of all-loop Bethe equations for the system. These
equations differ from the ones previously found in the literature by the choice
of relative grading between the two copies of the d(2,1;alpha) superalgebra,
and involve four undetermined scalar factors that play the role of dressing
phases. Imposing crossing symmetry and comparing with the near-BMN form of the
S-matrix found in the literature, we find several novel features. In
particular, the scalar factors must differ from the Beisert-Eden-Staudacher
phase, and should couple nodes of different masses to each other. In the
semiclassical limit the phases are given by a suitable generalization of
Arutyunov-Frolov-Staudacher phase.Comment: 26 pages, 2 figures. v2: references added. v3: changed notation for
the crossing equations, added references. Published versio
A dynamic su(1|1)^2 S-matrix for AdS3/CFT2
We derive the S-matrix for the d(2,1;alpha)^2 symmetric spin-chain of
AdS3/CFT2 by considering the centrally extended su(1|1)^2 algebra acting on the
spin-chain excitations. The S-matrix is determined uniquely up to four scalar
factors, which are further constrained by a set of crossing relations. The
resulting scattering includes non-trivial processes between magnons of
different masses that were previously overlooked.Comment: 41 pages, 4 figures. v2: corrected a misprint in appendix E, updated
references, corrected some typos. v3: added a new appendix F with comparison
to the literature, changed notation for the crossing equations, added
references. Published versio
Effect of in-mould inoculant composition on microstructure and fatigue behaviour of heavy section ductile iron castings
In this paper, the influence of the in-mould inoculant composition on microstructure and fatigue behaviour of heavy section ductile iron (EN GJS 700-2) castings has been investigated.
Axial fatigue tests under nominal load ratio R=0 have been performed on specimens taken from the core of large casting components. Metallographic analyses have been carried out by means of optical microscopy and important microstructural parameters that affect the mechanical properties of the alloy, such as nodule count, nodularity and graphite shape, were measured. Furthermore, Scanning Electron Microscopy was used to investigate the fracture surfaces of the samples in order to identify crack initiation and propagation zones.
Cracks initiation sites have been found to be microshrinkages close to specimens\u2019 surface in most cases. It was found that in-mould inoculant composition strongly influences the alloy microstructure, such as nodule count and shrinkage porosities size, as well as the fatigue resistance of heavy section ductile iron castings
Review of recent advances in local approaches applied to pre-stressed components under fatigue loading
Fatigue strength of mechanical components in the high cycle regime depends on both the applied loading and the intensity of any residual stress field induced by either non-homogeneous plastic deformation or the solidification of a local portion of material due to welding operations. In presence of geometric variations that are amenable to being modelled as a sharp V-notch, the residual stress distribution near the notch tip is singular and follows the same form as the solution obtained by Williams in 1952 where the intensity of the asymptotic stress field is quantified by the notch stress intensity factor (NSIF). However, the residual stress varies during fatigue loading and a stable value may be reached. Numerical models have been developed for the calculation of the residual NSIFs and their variation under fatigue loading. Taking advantage of these models, new local approaches have also been recently developed which are able to predict the fatigue strength of pre-stressed notched components. The present paper provides a brief review of such recent advances
Evaluation of the GreyWater Footprint Comparing the Indirect Effects of Different Agricultural Practices
Increasing global food demand and economic growth result in increasing competition over scarce freshwater resources, worsened by climate change and pollution. The agricultural sector has the largest share in the water footprint of humanity. While most studies focus on estimating water footprints (WFs) of crops through modeling, there are only few experimental field studies. The current work aims to understand the effect of supposedly better agricultural practices, particularly precision agriculture (variable rate application of fertilizers and pesticides) and conservation agriculture (minimum, strip, or no-tillage), on water deterioration and water pollution. We analyzed the results from an experimental field study in the northeast of Italy, in which four different crops are grown across three years of crops rotation. We compared minimum, strip, and no-tillage systems undergoing variable to uniform rate application. Grey WFs are assessed based on a field dataset using yield maps data, soil texture, and crop operations field. Leaching and associated grey WFs are assessed based on application rates and various environmental factors. Yields are measured in the field and recorded in a precision map. The results illustrate how precision agriculture combined with soil conservation tillage systems can reduce the grey water footprint by the 10%. We assessed the grey Water Footprint for all the field operation processes during the three-year crop rotation
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