9,489 research outputs found
Comments on Correlation Functions of Large Spin Operators and Null Polygonal Wilson Loops
We discuss the relation between correlation functions of twist-two large spin
operators and expectation values of Wilson loops along light-like trajectories.
After presenting some heuristic field theoretical arguments suggesting this
relation, we compute the divergent part of the correlator in the limit of large
't Hooft coupling and large spins, using a semi-classical worldsheet which
asymptotically looks like a GKP rotating string. We show this diverges as
expected from the expectation value of a null Wilson loop, namely, as
, being a cut-off of the theory.Comment: 16+3 pages, 3 figures. Computation in section 4.1 has been clarified.
Some comments on the vertex contributions has been added in section 4.2. Some
other minor corrections. Version to appear in Nucl. Phys.
Worldsheet four-point functions in AdS(3)/CFT(2)
We calculate some extremal and non-extremal four-point functions on the
sphere of certain chiral primary operators for strings on AdS_3 x S^3 x T^4.
The computation is done for small values of the spacetime cross-ratio where
global SL(2) and SU(2) descendants may be neglected in the intermediate
channel. Ignoring also current algebra descendants, we find that in the
non-extremal case the integrated worldsheet correlators factorize into
spacetime three-point functions, which is non-trivial due to the integration
over the moduli space. We then restrict to the extremal case and compare our
results with the four-point correlators recently computed in the dual boundary
theory. We also discuss a particular non-extremal correlator involving two
chiral and two anti-chiral operators.Comment: 34 pages, subsection on crossing symmetry adde
A review of current development in natural fiber composites for structural and infrastructure applications
Natural fiber composites (NFC) as the name implies is
made of natural resources thus possesses environmentally
beneficial properties such as biodegradability. With its natural characteristics, NFC is obtaining more attention in recent years in various application including automotive, merchandise, structural and infrastructure. Several studies have shown that NFC can be developed into a load-bearing structural member for applications in structural and infrastructure application. As an engineered material, similar with synthetic fiber composites, the properties of NFC can be tailored to meet certain requirements. The challenge in working with NFC is the large variation in properties and characteristics. The properties of NFC to a large extent influenced by the type of fibers, environmental condition where the plant fibers are sourced and the type of fiber treatments. However, with their unique and wide range of variability, natural fiber composites could emerge as a new alternative engineering material which can substitute the use of synthetic fiber composites
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