4,228 research outputs found
Light-Front Holography and Hadronization at the Amplitude Level
The correspondence between theories in anti-de Sitter space and conformal
field theories in physical space-time leads to an analytic, semiclassical model
for strongly-coupled QCD which has scale invariance at short distances and
color confinement at large distances. Light-front holography is a remarkable
feature of AdS/CFT: it allows hadronic amplitudes in the AdS fifth dimension to
be mapped to frame-independent light-front wavefunctions of hadrons in physical
space-time, thus providing a relativistic description of hadrons at the
amplitude level. Some novel features of QCD are discussed, including the
consequences of confinement for quark and gluon condensates and the behavior of
the QCD coupling in the infrared. We suggest that the spatial support of QCD
condensates is restricted to the interior of hadrons, since they arise due to
the interactions of confined quarks and gluons. Chiral symmetry is thus broken
in a limited domain of size of the inverse pion mass in analogy to the limited
physical extent of superconductor phases. A new method for computing the
hadronization of quark and gluon jets at the amplitude level, an event
amplitude generator, is outlined.Comment: Presented by SJB at the Sixth International Conference on
Perspectives in Hadronic Physics, 12 - 16 May 2008, Miramare - Trieste, Ital
Services within a busy period of an M/M/1 queue and Dyck paths
We analyze the service times of customers in a stable M/M/1 queue in
equilibrium depending on their position in a busy period. We give the law of
the service of a customer at the beginning, at the end, or in the middle of the
busy period. It enables as a by-product to prove that the process of instants
of beginning of services is not Poisson. We then proceed to a more precise
analysis. We consider a family of polynomial generating series associated with
Dyck paths of length 2n and we show that they provide the correlation function
of the successive services in a busy period with (n+1) customers
Microwave Components with MEMS Switches
RF MEMS switches with metal-metal contacts are being developed for microwave applications where broadband, high linearity performance is required. These switches provide less than 0.2 dB insertion loss through 40 GHz. This paper describes the integration of these switches into selected microwave components such as reconfigurable antenna elements, tunable filters, switched delay lines, and SPDT switches. Microwave and millimeter wave measured results from these circuits are presented
Approximating Long-Term Statistics Early in the Global Precipitation Measurement Era
Long-term precipitation records are vital to many applications, especially the study of extreme events. The Tropical Rainfall Measuring Mission (TRMM) has served this need, but TRMMs successor mission, Global Precipitation Measurement (GPM), does not yet provide a long-term record. Quantile mapping, the conversion of values across paired empirical distributions, offers a simple, established means to approximate such long-term statistics, but only within appropriately defined domains. This method was applied to a case study in Central America, demonstrating that quantile mapping between TRMM and GPM data maintains the performance of a real-time landslide model. Use of quantile mapping could bring the benefits of the latest satellite-based precipitation dataset to existing user communities such as those for hazard assessment, crop forecasting, numerical weather prediction, and disease tracking
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