233 research outputs found
Evolution of cusped light-like Wilson loops and geometry of the loop space
We discuss the possible relation between certain geometrical properties of
the loop space and energy evolution of the cusped Wilson exponentials defined
on the light-cone. Analysis of the area differential equations for this special
class of the Wilson loops calls for careful treatment of the ultraviolet and
rapidity divergences which make those loops
non-multiplicatively-renormalizable. We propose to consider the renormalization
properties of the light-cone cusped Wilson loops from the point of view of the
universal quantum dynamical approach introduced by Schwinger. We conjecture and
discuss the relevance of the Makeenko-Migdal loop equations supplied with the
modified Schwinger principle to the energy evolution of some phenomenologically
significant objects, such as transverse-momentum dependent distribution
functions, collinear parton densities at large-, etc.Comment: 6 pages, 3 eps figures; v2: misprints corrected, minor changes in the
conclusions, references updated; v3: extended to 8 pages, important updates
in Sect. 3, matches the version published in Phys. Rev.
Marginally Trapped Surfaces in the Nonsymmetric Gravitational Theory
We consider a simple, physical approach to the problem of marginally trapped
surfaces in the Nonsymmetric Gravitational Theory (NGT). We apply this approach
to a particular spherically symmetric, Wyman sector gravitational field,
consisting of a pulse in the antisymmetric field variable. We demonstrate that
marginally trapped surfaces do exist for this choice of initial data.Comment: REVTeX 3.0 with epsf macros and AMS symbols, 3 pages, 1 figur
Optimizing Dynamic Aperture Studies with Active Learning
Dynamic aperture is an important concept for the study of non-linear beam
dynamics in circular accelerators. It describes the extent of the phase-space
region where a particle's motion remains bounded over a given number of turns.
Understanding the features of dynamic aperture is crucial for the design and
operation of such accelerators, as it provides insights into nonlinear effects
and the possibility of optimising beam lifetime. The standard approach to
calculate the dynamic aperture requires numerical simulations of several
initial conditions densely distributed in phase space for a sufficient number
of turns to probe the time scale corresponding to machine operations. This
process is very computationally intensive and practically outside the range of
today's computers. In our study, we introduced a novel method to estimate
dynamic aperture rapidly and accurately by utilising a Deep Neural Network
model. This model was trained with simulated tracking data from the CERN Large
Hadron Collider and takes into account variations in accelerator parameters
such as betatron tune, chromaticity, and the strength of the Landau octupoles.
To enhance its performance, we integrate the model into an innovative Active
Learning framework. This framework not only enables retraining and updating of
the computed model, but also facilitates efficient data generation through
smart sampling. Since chaotic motion cannot be predicted, traditional tracking
simulations are incorporated into the Active Learning framework to deal with
the chaotic nature of some initial conditions. The results demonstrate that the
use of the Active Learning framework allows faster scanning of the
configuration parameters without compromising the accuracy of the dynamic
aperture estimates
ERAP2 increases the abundance of a peptide submotif highly selective for the Birdshot Uveitis-associated HLA-A29
Birdshot Uveitis (BU) is a blinding inflammatory eye condition that only affects HLA-A29-positive individuals. Genetic association studies linked ERAP2 with BU, an aminopeptidase which trims peptides before their presentation by HLA class I at the cell surface, which suggests that ERAP2-dependent peptide presentation by HLA-A29 drives the pathogenesis of BU. However, it remains poorly understood whether the effects of ERAP2 on the HLA-A29 peptidome are distinct from its effect on other HLA allotypes. To address this, we focused on the effects of ERAP2 on the immunopeptidome in patient-derived antigen presenting cells. Using complementary HLA-A29-based and pan-class I immunopurifications, isotope-labeled naturally processed and presented HLA-bound peptides were sequenced by mass spectrometry. We show that the effects of ERAP2 on the N-terminus of ligands of HLA-A29 are shared across endogenous HLA allotypes, but discover and replicate that one peptide motif generated in the presence of ERAP2 is specifically bound by HLA-A29. This motif can be found in the amino acid sequence of putative autoantigens. We further show evidence for internal sequence specificity for ERAP2 imprinted in the immunopeptidome. These results reveal that ERAP2 can generate an HLA-A29-specific antigen repertoire, which supports that antigen presentation is a key disease pathway in BU.Proteomic
Randweg Baarle-Nassau (NL) - Baarle-Hertog (B) Een inventariserend Veldonderzoek in de vorm van proefsleuven
Dit rapport werd ingediend bij het agentschap samen met een aantal afzonderlijke digitale bijlagen. Een aantal van deze bijlagen zijn niet inbegrepen in dit pdf document en zijn niet online beschikbaar. Sommige bijlagen (grondplannen, fotos, spoorbeschrijvingen, enz.) kunnen van belang zijn voor een betere lezing en interpretatie van dit rapport. Indien u deze bijlagen wenst te raadplegen kan u daarvoor contact opnemen met: [email protected]
Tree migration-rates : narrowing the gap between inferred post-glacial rates and projected rates
Faster-than-expected post-glacial migration rates of trees have puzzled ecologists for a long time. In Europe, post-glacial migration is assumed to have started from the three southern European peninsulas (southern refugia), where large areas remained free of permafrost and ice at the peak of the last glaciation. However, increasing palaeobotanical evidence for the presence of isolated tree populations in more northerly microrefugia has started to change this perception. Here we use the Northern Eurasian Plant Macrofossil Database and palaeoecological literature to show that post-glacial migration rates for trees may have been substantially lower (60–260 m yr–1) than those estimated by assuming migration from southern refugia only (115–550 m yr–1), and that early-successional trees migrated faster than mid- and late-successional trees. Post-glacial migration rates are in good agreement with those recently projected for the future with a population dynamical forest succession and dispersal model, mainly for early-successional trees and under optimal conditions. Although migration estimates presented here may be conservative because of our assumption of uniform dispersal, tree migration-rates clearly need reconsideration. We suggest that small outlier populations may be a key factor in understanding past migration rates and in predicting potential future range-shifts. The importance of outlier populations in the past may have an analogy in the future, as many tree species have been planted beyond their natural ranges, with a more beneficial microclimate than their regional surroundings. Therefore, climate-change-induced range-shifts in the future might well be influenced by such microrefugia
Transverse Momentum Dependent (TMD) Parton Distribution Functions: Status and Prospects
We review transverse momentum dependent (TMD) parton distribution functions, their application to topical issues in high-energy physics phenomenology, and their theoretical connections with QCD resummation, evolution and factorization theorems. We illustrate the use of TMDs via examples of multi-scale problems in hadronic collisions. These include transverse momentum qT spectra of Higgs and vector bosons for low qT, and azimuthal correlations in the production of multiple jets associated with heavy bosons at large jet masses. We discuss computational tools for TMDs, and present the application of a new tool, TMDLIB, to parton density fits and parameterizations
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