358 research outputs found
On All-loop Integrands of Scattering Amplitudes in Planar N=4 SYM
We study the relationship between the momentum twistor MHV vertex expansion
of planar amplitudes in N=4 super-Yang-Mills and the all-loop generalization of
the BCFW recursion relations. We demonstrate explicitly in several examples
that the MHV vertex expressions for tree-level amplitudes and loop integrands
satisfy the recursion relations. Furthermore, we introduce a rewriting of the
MHV expansion in terms of sums over non-crossing partitions and show that this
cyclically invariant formula satisfies the recursion relations for all numbers
of legs and all loop orders.Comment: 34 pages, 17 figures; v2: Minor improvements to exposition and
discussion, updated references, typos fixe
A Universal Model of Global Civil Unrest
Civil unrest is a powerful form of collective human dynamics, which has led
to major transitions of societies in modern history. The study of collective
human dynamics, including collective aggression, has been the focus of much
discussion in the context of modeling and identification of universal patterns
of behavior. In contrast, the possibility that civil unrest activities, across
countries and over long time periods, are governed by universal mechanisms has
not been explored. Here, we analyze records of civil unrest of 170 countries
during the period 1919-2008. We demonstrate that the distributions of the
number of unrest events per year are robustly reproduced by a nonlinear,
spatially extended dynamical model, which reflects the spread of civil disorder
between geographic regions connected through social and communication networks.
The results also expose the similarity between global social instability and
the dynamics of natural hazards and epidemics.Comment: 8 pages, 3 figure
First Results for Solar Soft X-ray Irradiance Measurements from the Third Generation Miniature X-Ray Solar Spectrometer
Three generations of the Miniature X-ray Solar Spectrometer (MinXSS) have
flown on small satellites with the goal "to explore the energy distribution of
soft X-ray (SXR) emissions from the quiescent Sun, active regions, and during
solar flares, and to model the impact on Earth's ionosphere and thermosphere".
The primary science instrument is the Amptek X123 X-ray spectrometer that has
improved with each generation of the MinXSS experiment. This third generation
MinXSS-3 has higher energy resolution and larger effective area than its
predecessors and is also known as the Dual-zone Aperture X-ray Solar
Spectrometer (DAXSS). It was launched on the INSPIRESat-1 satellite on 2022
February 14, and INSPIRESat-1 has successfully completed its 6-month prime
mission. The INSPIRESat-1 is in a dawn-dusk, Sun-Synchronous Orbit (SSO) and
therefore has 24-hour coverage of the Sun during most of its mission so far.
The rise of Solar Cycle 25 (SC-25) has been observed by DAXSS. This paper
introduces the INSPIRESat-1 DAXSS solar SXR observations, and we focus the
science results here on a solar occultation experiment and multiple flares on
2022 April 24. One key flare result is that the reduction of elemental
abundances is greatest during the flare impulsive phase and thus highlighting
the important role of chromospheric evaporation during flares to inject warmer
plasma into the coronal loops. Furthermore, these results are suggestive that
the amount of chromospheric evaporation is related to flare temperature and
intensity.Comment: 43 pages including 19-page Appendix A, 8 figures, 7 table
Experiencing stigma as sex work researchers in professional and personal lives
Researchers have demonstrated the challenges associated with sex work research; negotiating the stigma attached to its subject matter, the perceived dangerousness of participants, and the barriers faced in reaching hidden populations. By reflecting upon our separate research experiences and drawing upon a body of reflexive sex work research, this article explores how, as sex work researchers, we experienced stigma not only in our professional roles as researchers, but also in our personal lives. We apply Goffman's (1968) notion of stigma by association; and consider how stigma often associated with prostitution became transposed onto us. In particular, we compare and contrast our separate experiences of conducting sex work research to demonstrate our similar experiences of stigma by association
Solution to the Ward Identities for Superamplitudes
Supersymmetry and R-symmetry Ward identities relate on-shell amplitudes in a
supersymmetric field theory. We solve these Ward identities for (Next-to)^K MHV
amplitudes of the maximally supersymmetric N=4 and N=8 theories. The resulting
superamplitude is written in a new, manifestly supersymmetric and R-invariant
form: it is expressed as a sum of very simple SUSY and SU(N)_R-invariant
Grassmann polynomials, each multiplied by a "basis amplitude". For (Next-to)^K
MHV n-point superamplitudes the number of basis amplitudes is equal to the
dimension of the irreducible representation of SU(n-4) corresponding to the
rectangular Young diagram with N columns and K rows. The linearly independent
amplitudes in this algebraic basis may still be functionally related by
permutation of momenta. We show how cyclic and reflection symmetries can be
used to obtain a smaller functional basis of color-ordered single-trace
amplitudes in N=4 gauge theory. We also analyze the more significant reduction
that occurs in N=8 supergravity because gravity amplitudes are not ordered. All
results are valid at both tree and loop level.Comment: 29 pages, published versio
Prostate Cancer Susceptibility Loci Identified on Chromosome 12 in African Americans
Prostate cancer (PCa) is a complex disease that disproportionately affects African Americans and other individuals of African descent. A number of regions across the genome have been associated to PCa, most of them with moderate effects. A few studies have reported chromosomal changes on 12p and 12q that occur during the onset and development of PCa but to date no consistent association of the disease with chromosome 12 polymorphic variation has been identified. In order to unravel genetic risk factors that underlie PCa health disparities we investigated chromosome 12 using ancestry informative markers (AIMs), which allow us to distinguish genomic regions of European or West African origin, and tested them for association with PCa. Additional SNPs were genotyped in those areas where significant signals of association were detected. The strongest signal was discovered at the SNP rs12827748, located upstream of the PAWR gene, a tumor suppressor, which is amply expressed in the prostate. The most frequent allele in Europeans was the risk allele among African Americans. We also examined vitamin D related genes, VDR and CYP27B1, and found a significant association of PCa with the TaqI polymorphism (rs731236) in the former. Although our results warrant further investigation we have uncovered a genetic susceptibility factor for PCa in a likely candidate by means of an approach that takes advantage of the differential contribution of parental groups to an admixed population
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