22 research outputs found
Gauged extended supergravity without cosmological constant: no-scale structure and supersymmetry breaking
We consider the interplay of duality symmetries and gauged isometries of
supergravity models giving N-extended, spontaneously broken supergravity with a
no-scale structure. Some examples, motivated by superstring and M-theory
compactifications are described.Comment: AMS-LaTeX, 16 pages. Invited paper to appear in the review section of
the IJMP
Double Parton Scattering Singularity in One-Loop Integrals
We present a detailed study of the double parton scattering (DPS)
singularity, which is a specific type of Landau singularity that can occur in
certain one-loop graphs in theories with massless particles. A simple formula
for the DPS singular part of a four-point diagram with arbitrary
internal/external particles is derived in terms of the transverse momentum
integral of a product of light cone wavefunctions with tree-level matrix
elements. This is used to reproduce and explain some results for DPS
singularities in box integrals that have been obtained using traditional loop
integration techniques. The formula can be straightforwardly generalised to
calculate the DPS singularity in loops with an arbitrary number of external
particles. We use the generalised version to explain why the specific MHV and
NMHV six-photon amplitudes often studied by the NLO multileg community are not
divergent at the DPS singular point, and point out that whilst all NMHV
amplitudes are always finite, certain MHV amplitudes do contain a DPS
divergence. It is shown that our framework for calculating DPS divergences in
loop diagrams is entirely consistent with the `two-parton GPD' framework of
Diehl and Schafer for calculating proton-proton DPS cross sections, but is
inconsistent with the `double PDF' framework of Snigirev.Comment: 29 pages, 8 figures. Minor corrections and clarifications added.
Version accepted for publication in JHE
N=4 gauged supergravity and a IIB orientifold with fluxes
We analyze the properties of a spontaneously broken D=4, N=4 supergravity
without cosmological constant, obtained by gauging translational isometries of
its classical scalar manifold. This theory offers a suitable low energy
description of the super-Higgs phases of certain Type-IIB orientifold
compactifications with 3-form fluxes turned on. We study its N=3,2,1,0 phases
and their classical moduli spaces and we show that this theory is an example of
no-scale extended supergravity.Comment: Misprints corrected. Version appeared on NJP 4 (2002)7
Fabrication and tribological characterization of gradient carbon layer derived from SiC-TiC composites
Using Laser-Induced Acoustic Desorption/Electrospray Ionization Mass Spectrometry To Characterize Small Organic and Large Biological Compounds in the Solid State and in Solution Under Ambient Conditions
Identification of Surface Structures on 3C-SiC Nanocrystals with Hydrogen and Hydroxyl Bonding by Photoluminescence
Operando tribochemical formation of onion-like-carbon leads to macroscale superlubricity
Stress-induced tribochemical reactions that reduce friction at sliding interfaces typically require liquid lubricants. Here, the authors discover the nanoscale tribocatalytic formation of onion-like carbon from 2D MoS2 and nanodiamond under dry and oil-free conditions, providing superlubricity at the macroscale