371 research outputs found
Divergences in maximal supersymmetric Yang-Mills theories in diverse dimensions
The main aim of this paper is to study the scattering amplitudes in gauge
field theories with maximal supersymmetry in dimensions D=6,8 and 10. We
perform a systematic study of the leading ultraviolet divergences using the
spinor helicity and on-shell momentum superspace framework. In D=6 the first
divergences start at 3 loops and we calculate them up to 5 loops, in D=8,10 the
first divergences start at 1 loop and we calculate them up to 4 loops. The
leading divergences in a given order are the polynomials of Mandelstam
variables. To be on the safe side, we check our analytical calculations by
numerical ones applying the alpha-representation and the dedicated routines.
Then we derive an analog of the RG equations for the leading pole that allows
us to get the recursive relations and construct the generating procedure to
obtain the polynomials at any order of (perturbation theory) PT. At last, we
make an attempt to sum the PT series and derive the differential equation for
the infinite sum. This equation possesses a fixed point which might be stable
or unstable depending on the kinematics. Some consequences of these fixed
points are discussed.Comment: 43 pages, 13 figures, pdf LaTex, v2 minor changes and references
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Summation of all-loop UV divergences in maximally supersymmetric gauge theories
We consider the leading and subleading UV divergences for the four-point
on-shell scattering amplitudes in D=6,8,10 supersymmetric Yang-Mills theories
in the planar limit. These theories belong to the class of maximally
supersymmetric gauge theories and presumably possess distinguished properties
beyond perturbation theory. In the previous works, we obtained the recursive
relations that allow one to get the leading and subleading divergences in all
loops in a pure algebraic way. The all loop summation of the leading
divergences is performed with the help of the differential equations which are
the generalization of the RG equations for non-renormalizable theories. Here we
mainly focus on solving and analyzing these equations. We discuss the
properties of the obtained solutions and interpretation of the results.Comment: PdfLatex, 18 pages, 9 Figure
Formaldehyde measurements by Proton transfer reaction – Mass Spectrometry (PTR-MS): correction for humidity effects
Formaldehyde measurements can provide useful information about photochemical activity in ambient air, given that HCHO is formed via numerous oxidation processes. Proton transfer reaction mass spectrometry (PTR-MS) is an online technique that allows measurement of VOCs at the sub-ppbv level with good time resolution. PTR-MS quantification of HCHO is hampered by the humidity dependence of the instrument sensitivity, with higher humidity leading to loss of PTR-MS signal. In this study we present an analytical, first principles approach to correct the PTR-MS HCHO signal according to the concentration of water vapor in sampled air. The results of the correction are validated by comparison of the PTR-MS results to those from a Hantzsch fluorescence monitor which does not have the same humidity dependence. Results are presented for an intercomparison made during a field campaign in rural Ontario at Environment Canada's Centre for Atmospheric Research Experiments
Optical and dynamic nuclear polarization of 29Si nuclei via photoexcited triplet states of oxygen-vacancy complexes in isotopically controlled silicon
Optical and dynamic nuclear polarization o
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