1,771 research outputs found
Mandelstam cuts and light-like Wilson loops in N=4 SUSY
We perform an analytic continuation of the two-loop remainder function for
the six-point planar MHV amplitude in N=4 SUSY, found by Goncharov, Spradlin,
Vergu and Volovich from the light-like Wilson loop representation. The
remainder function is continued into a physical region, where all but two
energy invariants are negative. It turns out to be pure imaginary in the
multi-Regge kinematics, which is in an agreement with the predictions based on
the Steinmann relations for the Regge poles and Mandelstam cut contributions.
The leading term reproduces correctly the expression calculated by one of the
authors in the BFKL approach, while the subleading term presents a result, that
was not yet found with the use of the unitarity techniques. This supports the
applicability of the Wilson loop approach to the planar MHV amplitudes in N=4
SUSY.Comment: 11 pages, 4 figure
BFKL approach and 2->5 MHV amplitude
We study MHV amplitude for the 2 -> 5 scattering in the multi-Regge
kinematics. The Mandelstam cut correction to the BDS amplitude is calculated in
the leading logarithmic approximation (LLA) and the corresponding remainder
function is given to any loop order in a closed integral form. We show that the
LLA remainder function at two loops for 2 -> 5 amplitude can be written as a
sum of two 2 -> 4 remainder functions due to recursive properties of the
leading order impact factors. We also make some generalizations for the MHV
amplitudes with more external particles. The results of the present study are
in agreement with all leg two loop symbol derived by Caron-Huot as shown in a
parallel paper of one of the authors with collaborators.Comment: 24 pages, 17 figure
Spatio-temporal analysis of leprosy risks in a municipality in the state of Mato Grosso-Brazilian Amazon: results from the leprosy post-exposure prophylaxis program in Brazil
BACKGROUND: Leprosy post-exposure prophylaxis (LPEP) with single dose rifampicin (SDR) can be integrated into different leprosy control program set-ups once contact tracing has been established. We analyzed the spatio-temporal changes in the distribution of index cases (IC) and co-prevalent cases among contacts of leprosy patients (CP) over the course of the LPEP program in one of the four study areas in Brazil, namely the municipality of Alta Floresta, state of Mato Grosso, in the Brazilian Amazon basin. METHODS: Leprosy cases were mapped, and socioeconomic indicators were evaluated to explain the leprosy distribution of all leprosy cases diagnosed in the period 2016-2018. Data were obtained on new leprosy cases [Notifiable diseases information system (Sinan)], contacts traced by the LPEP program, and socioeconomic variables [Brazilian Institute of Geography and Statistics (IBGE)]. Kernel, SCAN, factor analysis and spatial regression were applied to analyze changes. RESULTS: Overall, the new case detection rate (NCDR) was 20/10 000 inhabitants or 304 new cases, of which 55 were CP cases among the 2076 examined contacts. Changes over time were observed in the geographic distribution of cases. The highest concentration of cases was observed in the northeast of the study area, including one significant cluster (Relative risk = 2.24; population 27 427, P-value < 0.001) in an area characterized by different indicators associated with poverty as identified through spatial regression (Coefficient 3.34, P-value = 0.01). CONCLUSIONS: The disease distribution was partly explained by poverty indicators. LPEP influences the spatial dynamic of the disease and results highlighted the relevance of systematic contact surveillance for leprosy elimination
Towards Direct Detection of the Shape of CSR Pulses with Fast THz Detectors
Coherent synchrotron radiation (CSR) is emitted when the emitting structure is equal to or smaller than the observed wavelength. Consequently, these pulses are very short and most detectors respond with their impulse response, regardless of the pulse length and shape. Here we present single-shot measurements performed at the Karlsruhe Research Accelerator (KARA) using a fast real-time oscilloscope and Schottky barrier detectors sensitive in the sub-THz range. The time response of this setup to CSR pulses emitted by electron bunches during the microbunching instability is shown to be sensitive to the shape of the electron bunch. Our results show how, in the future, the shape of electron bunches can be directly measured using a straightforward setup
Are the clinical features of leprosy and American tegumentary leishmaniasis worse in patients with both diseases?
This cross-sectional population-based study compared clinical features of leprosy and American tegumentary leishmaniasis (ATL) in patients diagnosed with both diseases (n=414) and in those diagnosed with only leprosy (n=27,790) or only ATL (n=24,357) in Mato Grosso State, which is a hyperendemic area for both diseases in Midwest Brazil. All new cases of leprosy and ATL reported in the area from 2008 to 2017 were included. Patients diagnosed with both diseases were identified by a probabilistic linkage procedure applied to leprosy and ATL databases of the national reporting system. The distribution of the frequency of clinical features between groups was compared by the chi-square test, followed by a multivariate logistic regression. Patients diagnosed with both leprosy and ATL presented higher odds of having nerve damage (OR: 1.34; 95% CI: 1.09-1.66) and leprosy reactions (OR: 1.35; 95% CI: 1.04-1.76) compared to patients diagnosed only with leprosy. Mucocutaneous leishmaniasis (OR: 2.29; 95% CI: 1.74-3.00) was more frequent among patients with both diagnoses when compared to patients who only had ATL. In conclusion, patients diagnosed with both leprosy and ATL present more severe clinical features of such diseases. Our data can be useful for designing health policies aimed at timely and integrated management of leprosy and ATL in co-endemic areas
Are spurred cyathia a key innovation? Molecular systematics and trait evolution in the slipper spurges (Pedilanthus clade: Euphorbia, Euphorbiaceae)
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141662/1/ajb20493.pd
BFKL Pomeron, Reggeized gluons and Bern-Dixon-Smirnov amplitudes
After a brief review of the BFKL approach to Regge processes in QCD and in
supersymmetric (SUSY) gauge theories we propose a strategy for calculating the
next-to-next-to-leading order corrections to the BFKL kernel. They can be
obtained in terms of various cross-sections for Reggeized gluon interactions.
The corresponding amplitudes can be calculated in the framework of the
effective action for high energy scattering. In the case of N=4 SUSY it is also
possible to use the Bern-Dixon-Smirnov (BDS) ansatz. For this purpose the
analytic properties of the BDS amplitudes at high energies are investigated, in
order to verify their self-consistency. It is found that, for the number of
external particles being larger than five, these amplitudes, beyond one loop,
are not in agreement with the BFKL approach which predicts the existence of
Regge cuts in some physical channels.Comment: 41 pages, expanded version with many clarifications and new
references, conclusions unchanged. Note adde
Infra-Red Asymptotic Dynamics of Gauge Invariant Charged Fields: QED versus QCD
The freedom one has in constructing locally gauge invariant charged fields in
gauge theories is analyzed in full detail and exploited to construct, in QED,
an electron field whose two-point function W(p), up to the fourth order in the
coupling constant, is normalized with on-shell normalization conditions and is,
nonetheless, infra-red finite; as a consequence the radiative corrections
vanish on the mass shell and the free field singularity is
dominant, although, in contrast to quantum field theories with mass gap, the
eigenvalue of the mass operator is not isolated. The same construction,
carried out for the quark in QCD, is not sufficient for cancellation of
infra-red divergences to take place in the fourth order. The latter
divergences, however, satisfy a simple factorization equation. We speculate on
the scenario that could be drawn about infra-red asymptotic dynamics of QCD,
should this factorization equation be true in any order of perturbation theory.Comment: 30 pages, RevTex, 8 figures included using graphic
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