59 research outputs found
On RR couplings on D-branes at order
Recently, it has been found that there are couplings of the RR field strength
and the B-field strength on the world volume of D-branes at
order . These couplings which have both world-volume and
transverse indices, are invariant under the linear T-duality transformations.
Consistency with the nonlinear T-duality indicates that the RR field strength
in these couplings should be replaced by where . This replacement, however, reproduces some
non-gauge invariant terms. On the other hand, the nonlinear terms are invariant
under the linear T-duality transformations at the level of two B-fields. This
allows one to remove some of the nonlinear terms in . We fix
this by comparing the nonlinear couplings with the S-matrix element of one RR
and two NSNS vertex operators. Our results indicate that in the expansion of
one should keep only the B-field gauge invariant terms, e.g.
where both indices of B-field lie along the brane.
Moreover, in this case one should replace with to have the
-field gauge invariance.Comment: 23 pages, Latex file, 1 figure; v2:typos corrected, to appear in JHE
Global patient outcomes after elective surgery: prospective cohort study in 27 low-, middle- and high-income countries.
BACKGROUND: As global initiatives increase patient access to surgical treatments, there remains a need to understand the adverse effects of surgery and define appropriate levels of perioperative care. METHODS: We designed a prospective international 7-day cohort study of outcomes following elective adult inpatient surgery in 27 countries. The primary outcome was in-hospital complications. Secondary outcomes were death following a complication (failure to rescue) and death in hospital. Process measures were admission to critical care immediately after surgery or to treat a complication and duration of hospital stay. A single definition of critical care was used for all countries. RESULTS: A total of 474 hospitals in 19 high-, 7 middle- and 1 low-income country were included in the primary analysis. Data included 44 814 patients with a median hospital stay of 4 (range 2-7) days. A total of 7508 patients (16.8%) developed one or more postoperative complication and 207 died (0.5%). The overall mortality among patients who developed complications was 2.8%. Mortality following complications ranged from 2.4% for pulmonary embolism to 43.9% for cardiac arrest. A total of 4360 (9.7%) patients were admitted to a critical care unit as routine immediately after surgery, of whom 2198 (50.4%) developed a complication, with 105 (2.4%) deaths. A total of 1233 patients (16.4%) were admitted to a critical care unit to treat complications, with 119 (9.7%) deaths. Despite lower baseline risk, outcomes were similar in low- and middle-income compared with high-income countries. CONCLUSIONS: Poor patient outcomes are common after inpatient surgery. Global initiatives to increase access to surgical treatments should also address the need for safe perioperative care. STUDY REGISTRATION: ISRCTN5181700
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
Wellbeing, activity and housing satisfaction – comparing residents with psychiatric disabilities in supported housing and ordinary housing with support
Super-Yang–Mills, Chern–Simons couplings and their all order α ′ corrections in IIB superstring theory
Synergistic impacts by an invasive amphipod and an invasive fish explain native gammarid extinction
Application of small fragment restriction endonuclease analysis (SF-REA) to the epidemiological fingerprinting of Staphylococcus aureus
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