20 research outputs found
The SAGEX Review on Scattering Amplitudes
This is an introduction to, and invitation to read, a series of review
articles on scattering amplitudes in gauge theory, gravity, and superstring
theory. Our aim is to provide an overview of the field, from basic aspects to a
selection of current (2022) research and developments.Comment: 15 pages, overview articl
Two-loop scattering amplitudes from ambitwistor strings: from genus two to the nodal Riemann sphere
We derive from ambitwistor strings new formulae for two-loop scattering
amplitudes in supergravity and super-Yang-Mills theory, with any number of
particles. We start by constructing a formula for the type II ambitwistor
string amplitudes on a genus-two Riemann surface, and then study the
localisation of the moduli space integration on a degenerate limit, where the
genus-two surface turns into a Riemann sphere with two nodes. This leads to
scattering amplitudes in supergravity, expressed in the formalism of the
two-loop scattering equations. For super-Yang-Mills theory, we import `half' of
the supergravity result, and determine the colour dependence by considering a
current algebra on the nodal Riemann sphere, thereby completely specifying the
two-loop analogue of the Parke-Taylor factor, including non-planar
contributions. We also present in appendices explicit expressions for the Szego
kernels and the partition functions for even spin structures, up to the
relevant orders in the degeneration parameters, which may be useful for related
investigations in conventional superstring theory.Comment: 66 pages plus appendices, 14 figures. v2: small changes, published
version. v3: typos fixed in appendix
Incorrect data sustain the claim of forestâbased bioenergy being more effective in climate change mitigation than forest conservation
Dual Vulnerability of Being Both a Teen and an Immigrant Parent: Illustrations from an Italian Context
Nutritional and Possible Pharmaceutical Aspects of Tree Exudates Eaten by Lemurs of Madagascarâs Dry Forests
Gums produced by trees after injuries are valuable food resources for several primate species. Yet, information on the chemical characteristics of gum is scant and inconsistent. We use gums consumed by lemurs (strepsirrhine primates of Madagascar) as an example to illustrate their possible nutritive and pharmaceutical properties. Exudates from 45 tree species of the dry forests of Madagascar contained 0.38â23.29% protein, 0.46â65.62% sugar, and 0.39â11.86 kJ/g of energy in dry matter. Exemplified by the lemur species Microcebus griseorufus, gum consumption increased with increasing sugar and energy content but was unrelated to protein. But lemurs also fed on gum with very low protein and energy content, suggesting that these exudates were consumed for other reasons. Disk diffusion tests with exudates from five out of 22 tree species consumed by lemurs showed antibacterial activity against Micrococcus spp. and/or Staphylococcus aureus. Exudates with antibacterial activity had lower protein, sugar, and energy contents than samples without antibacterial properties. GC-MS analyses revealed several components with antimicrobial effects that would have the potential for self-medication. This might explain the consumption of gum with very low nutritive value. Possible medicinal effects of tree exudates deserve further attention in view of their pharmaceutical applicability for animals and humans alike
The SAGEX review on scattering amplitudes
This is an introduction to, and invitation to read, a series of review articles on scattering amplitudes in gauge theory, gravity, and superstring theory. Our aim is to provide an overview of the field, from basic aspects to a selection of current (2022) research and developments.ISSN:1751-8113ISSN:1361-644