1,452 research outputs found
A study of manganese dioxide-hydrogen insertion compounds produced by different chemical insertion methods
The reduction of an electrolytic manganese dioxide (EMD) by two different
chemical insertion methods (propan-2-o1 and hydrazinc .hydrate) has been studied by
XRD (X-Ray Diffraction), FTIR (Fourier Transfonn infrared) and Electrode Potential
Me:lsurements.
The level of H insertion may be represented by MnOOH" w'here r goes fi-om :::: 0,1
in the starting material (due to non-stoichiometry) up to 1.0 in the most reduced material.
H inseniol1 into EMD led to approximate isotropic lattice expansion up to r values close
to 0.7 - O.S for the propan-2-01 reduction method. This observation was consistent with a
homogeneous solid state reduction with formation of a solid solution in which II:'" and eare
mobile. In the region r = 0,7-0,8 to LO, new XRD non-moving lines emerged. while
the original lines continued to move, indicating anisotropic lattice expansion. This is due
to the appe:lrance of microdomains of the end product within the solid solution, implying
that H- and e' were no longer mobile in the crystal structure bur located in position, which
has been supported by FTIR measurements looking carefully at wavenumber regions
where 0-H vibration occurred.
For the hydrazine hydrate reduced samples, the O-H bond formation takes place at
a much earlier stage of reduction. Examination of the XRD patterns indicated
heterogeneous solid state reduction had occurred after r = 0,4. Heterogeneous reduction
was presumed to have occurred by H location in the outside layers of the particles.
A study of the potential of the compounds obtained under both reduction methods
has been carried out. together with the study of the stability of the H inserted compounds
in KOH electrolyte. Potential measurements confilmed development of a heterogeneous
potential coinciding to the appearance of new peaks on X-ray diffi:action and the
f0l111ation of O-H bonds as shown in FTIR. This behaviour appears at Cl. much earlier level
of reduction for the hydrazine hydrate reduced samples than for the propan-2-01 reduced
samples. The results confilm previous findings that H inserted compounds are unstable at
a !evel related to the fOlmation of micro domains in KOH at concentrations similar to
those used in alkaline manganese batteries, which limits the capacity of those batteries
Universal structure of subleading infrared poles at strong coupling
Recently a concise expression for the subleading infrared singularity of
dimensional-regularized gauge theories has been proposed. For conformal
theories, such relation involves a universal eikonal contribution plus a
non-eikonal contribution, related to the subleading term in the anomalous
dimension of twist two operators with large spin. In this note we make use of
the AdS/CFT correspondence in order to check such conjecture at strong coupling
for the case of N=4 SYM.Comment: 13 page
Correlation functions, null polygonal Wilson loops, and local operators
We consider the ratio of the correlation function of n+1 local operators over
the correlator of the first n of these operators in planar N=4 super-Yang-Mills
theory, and consider the limit where the first n operators become pairwise null
separated. By studying the problem in twistor space, we prove that this is
equivalent to the correlator of a n-cusp null polygonal Wilson loop with the
remaining operator in general position, normalized by the expectation value of
the Wilson loop itself, as recently conjectured by Alday, Buchbinder and
Tseytlin. Twistor methods also provide a BCFW-like recursion relation for such
correlators. Finally, we study the natural extension where n operators become
pairwise null separated with k operators in general position. As an example, we
perform an analysis of the resulting correlator for k=2 and discuss some of the
difficulties associated to fixing the correlator completely in the strong
coupling regime.Comment: 34 pages, 6 figures. v2: typos corrected and references added; v3:
published versio
Differential equations for multi-loop integrals and two-dimensional kinematics
In this paper we consider multi-loop integrals appearing in MHV scattering
amplitudes of planar N=4 SYM. Through particular differential operators which
reduce the loop order by one, we present explicit equations for the two-loop
eight-point finite diagrams which relate them to massive hexagons. After the
reduction to two-dimensional kinematics, we solve them using symbol technology.
The terms invisible to the symbols are found through boundary conditions coming
from double soft limits. These equations are valid at all-loop order for double
pentaladders and allow to solve iteratively loop integrals given lower-loop
information. Comments are made about multi-leg and multi-loop integrals which
can appear in this special kinematics. The main motivation of this
investigation is to get a deeper understanding of these tools in this
configuration, as well as for their application in general four-dimensional
kinematics and to less supersymmetric theories.Comment: 25 pages, 7 figure
Note About Integrability and Gauge Fixing for Bosonic String on AdS(5)xS(5)
This short note is devoted to the study of the integrability of the bosonic
string on AdS(5)xS(5) in the uniform light-cone gauge. We construct Lax
connection for gauge fixed theory and we argue that it is flat.Comment: 17 page
Supersymmetric Wilson loops in diverse dimensions
archiveprefix: arXiv primaryclass: hep-th reportnumber: AEI-2009-036, HU-EP-09-15 slaccitation: %%CITATION = ARXIV:0904.0455;%%archiveprefix: arXiv primaryclass: hep-th reportnumber: AEI-2009-036, HU-EP-09-15 slaccitation: %%CITATION = ARXIV:0904.0455;%%archiveprefix: arXiv primaryclass: hep-th reportnumber: AEI-2009-036, HU-EP-09-15 slaccitation: %%CITATION = ARXIV:0904.0455;%
Non-commutative holography and scattering amplitudes in a large magnetic background
We study planar gluon scattering amplitudes and Wilson loops in
non-commutative gauge theory. Our main results are:
1. We find the map between observables in non-commutative gauge theory and
their holographic dual. In that map, the region near the boundary of the
gravitational dual describes the physics in terms of T-dual variables.
2. We show that in the presence of a large magnetic background and a UV
regulator, a planar gluon scattering amplitude reduces to a complex polygon
Wilson loop expectation value, dressed by a tractable polarization dependent
factor.Comment: 26 pages. v2: corrected section 4, reference adde
AGT on the S-duality Wall
Three-dimensional gauge theory T[G] arises on a domain wall between
four-dimensional N=4 SYM theories with the gauge groups G and its S-dual G^L.
We argue that the N=2^* mass deformation of the bulk theory induces a
mass-deformation of the theory T[G] on the wall. The partition functions of the
theory T[SU(2)] and its mass-deformation on the three-sphere are shown to
coincide with the transformation coefficient of Liouville one-point conformal
block on torus under the S-duality.Comment: 14 pages, 3 figures. v2: Revised the analysis in sections 3.3 and 4.
Notes and references added. Version to appear in JHE
On correlation functions of Wilson loops, local and non-local operators
We discuss and extend recent conjectures relating partial null limits of
correlation functions of local gauge invariant operators and the expectation
value of null polygonal Wilson loops and local gauge invariant operators. We
point out that a particular partial null limit provides a strategy for the
calculation of the anomalous dimension of short twist-two operators at weak and
strong coupling.Comment: 29 pages, 8 figure
A finite analog of the AGT relation I: finite W-algebras and quasimaps' spaces
Recently Alday, Gaiotto and Tachikawa proposed a conjecture relating
4-dimensional super-symmetric gauge theory for a gauge group G with certain
2-dimensional conformal field theory. This conjecture implies the existence of
certain structures on the (equivariant) intersection cohomology of the
Uhlenbeck partial compactification of the moduli space of framed G-bundles on
P^2. More precisely, it predicts the existence of an action of the
corresponding W-algebra on the above cohomology, satisfying certain properties.
We propose a "finite analog" of the (above corollary of the) AGT conjecture.
Namely, we replace the Uhlenbeck space with the space of based quasi-maps from
P^1 to any partial flag variety G/P of G and conjecture that its equivariant
intersection cohomology carries an action of the finite W-algebra U(g,e)
associated with the principal nilpotent element in the Lie algebra of the Levi
subgroup of P; this action is expected to satisfy some list of natural
properties. This conjecture generalizes the main result of arXiv:math/0401409
when P is the Borel subgroup. We prove our conjecture for G=GL(N), using the
works of Brundan and Kleshchev interpreting the algebra U(g,e) in terms of
certain shifted Yangians.Comment: minor change
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