529 research outputs found
New and old N=8 superconformal field theories in three dimensions
We show that an infinite family of N=6 d=3 superconformal Chern-Simons-matter
theories has hidden N=8 superconformal symmetry and hidden parity on the
quantum level. This family of theories is different from the one found by
Aharony, Bergman, Jafferis and Maldacena, as well as from the theories
constructed by Bagger and Lambert, and Gustavsson. We also test several
conjectural dualities between BLG theories and ABJ theories by comparing
superconformal indices of these theories.Comment: 16 pages, late
Tests of Seiberg-like Duality in Three Dimensions
We use localization techniques to study several duality proposals for
supersymmetric gauge theories in three dimensions reminiscent of Seiberg
duality. We compare the partition functions of dual theories deformed by real
mass terms and FI parameters. We find that Seiberg-like duality for N=3
Chern-Simons gauge theories proposed by Giveon and Kutasov holds on the level
of partition functions and is closely related to level-rank duality in pure
Chern-Simons theory. We also clarify the relationship between the
Giveon-Kutasov duality and a duality in theories of fractional M2 branes and
propose a generalization of the latter. Our analysis also confirms previously
known results concerning decoupled free sectors in N=4 gauge theories realized
by monopole operators.Comment: 36 pages, 5 figure
Mössbauer study of some perovskite-related oxides
Complex perovskite-related oxides with various structure types: orthoferrites, 4-1-5, 8-8-20, and 1-2-3 were studied using Mössbauer spectroscopy. Correlations between magnetic ordering of iron atoms and their structural coordination, as well as between oxygen deficiency and iron ion valence, were found. © 2006 by Allerton Press, Inc
Investigation of the cation distribution in perovskite-like oxides with mössbauer spectroscopy
Complex perovskite-like oxides, such as LnFe(2/3)Mo(1/3)O"3 orthoferrites, Ln(8 -) ySryCu(8 -) xFexO"2"0 (8-8-20), Pr"4BaCu"4FeO(13 - δ) (4-1-5), YBa(2 -) yLayCu(3 -) xFexO(7 - δ), and Y(1 -) yCayBa(2 -) yLayCu(3 -) xFexO(7 - δ) (1-2-3), are studied by means of Mössbauer spectroscopy. At room temperature, the spectra of the orthoferrites contain only magnetic components. The spectra of the 1-2-3 compounds contain only magnetically disordered components: iron atoms substitute for copper at Cu(1) sites, taking various configurations: planar squares, quadratic pyramids, and octahedra. Cuprates 8-8-20 and 4-1-5 have a wide diversity of spectra. In the 8-8-20 oxides, a phase related to the pyramidal environment of the iron cations is present at any iron concentration. In all the perovskites, iron cations become magnetically ordered only at octahedral sites of the structure. © 2005 Pleiades Publishing, Inc
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Gas-Phase Synthesis of Triphenylene (C18 H12 ).
For the last decades, the hydrogen-abstraction-acetylene-addition (HACA) mechanism has been widely invoked to rationalize the high-temperature synthesis of PAHs as detected in carbonaceous meteorites (CM) and proposed to exist in the interstellar medium (ISM). By unravelling the chemistry of the 9-phenanthrenyl radical ([C14 H9 ]. ) with vinylacetylene (C4 H4 ), we present the first compelling evidence of a barrier-less pathway leading to a prototype tetracyclic PAH - triphenylene (C18 H12 ) - via an unconventional hydrogen abstraction-vinylacetylene addition (HAVA) mechanism operational at temperatures as low as 10 K. The barrier-less, exoergic nature of the reaction reveals HAVA as a versatile reaction mechanism that may drive molecular mass growth processes to PAHs and even two-dimensional, graphene-type nanostructures in cold environments in deep space thus leading to a better understanding of the carbon chemistry in our universe through the untangling of elementary reactions on the most fundamental level
Mössbauer investigations of magnetic system stratification in europium and thulium ferromanganites
Strontium-substituted ferromanganites of europium and thulium were investigated. Samples of Eu0.65Sr0.35Mn 1-xFexO3 and Tm0.65Sr 0.35Mn1-xFexO3 were prepared using ceramic processing. Based on the data from X-ray analysis, the samples with europium had a perovskite lattice, whereas the thulium samples were crystallized in an ilmenite lattice. Stratification of the magnetic subsystem was observed in the Mössbauer spectra of certain samples at T ≈ 300 K. © Allerton Press, Inc., 2010
Superconformal indices of three-dimensional theories related by mirror symmetry
Recently, Kim and Imamura and Yokoyama derived an exact formula for
superconformal indices in three-dimensional field theories. Using their
results, we prove analytically the equality of superconformal indices in some
U(1)-gauge group theories related by the mirror symmetry. The proofs are based
on the well known identities of the theory of -special functions. We also
suggest the general index formula taking into account the global
symmetry present for abelian theories.Comment: 17 pages; minor change
Sensory properties of solid solutions based on cobaltites of rare earth elements and bismuth ferrite
Results from a Prototype Proton-CT Head Scanner
We are exploring low-dose proton radiography and computed tomography (pCT) as
techniques to improve the accuracy of proton treatment planning and to provide
artifact-free images for verification and adaptive therapy at the time of
treatment. Here we report on comprehensive beam test results with our prototype
pCT head scanner. The detector system and data acquisition attain a sustained
rate of more than a million protons individually measured per second, allowing
a full CT scan to be completed in six minutes or less of beam time. In order to
assess the performance of the scanner for proton radiography as well as
computed tomography, we have performed numerous scans of phantoms at the
Northwestern Medicine Chicago Proton Center including a custom phantom designed
to assess the spatial resolution, a phantom to assess the measurement of
relative stopping power, and a dosimetry phantom. Some images, performance, and
dosimetry results from those phantom scans are presented together with a
description of the instrument, the data acquisition system, and the calibration
methods.Comment: Conference on the Application of Accelerators in Research and
Industry, CAARI 2016, 30 October to 4 November 2016, Ft. Worth, TX, US
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