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