1,699 research outputs found
New tests and applications of the worldline path integral in the first order formalism
We present different non-perturbative calculations within the context of
Migdal's representation for the propagator and effective action of quantum
particles. We first calculate the exact propagators and effective actions for
Dirac, scalar and Proca fields in the presence of constant electromagnetic
fields, for an even-dimensional spacetime. Then we derive the propagator for a
charged scalar field in a spacelike vortex (i.e., instanton) background, in a
long-distance expansion, and the exact propagator for a massless Dirac field in
1+1 dimensions in an arbitrary background. Finally, we present an
interpretation of the chiral anomaly in the present context, finding a
condition that the paths must fulfil in order to have a non-vanishing anomaly.Comment: 26 page
A Tight Lower Bound to the Outage Probability of Discrete-Input Block-Fading Channels
In this correspondence, we propose a tight lower bound to the outage
probability of discrete-input Nakagami-m block-fading channels. The approach
permits an efficient method for numerical evaluation of the bound, providing an
additional tool for system design. The optimal rate-diversity trade-off for the
Nakagami-m block-fading channel is also derived and a tight upper bound is
obtained for the optimal coding gain constant.Comment: 22 pages, 4 figures. This work has been accepted for IEEE
Transactions on Information Theory and has been presented in part at the 2007
IEEE International Symposium on Information Theory, Nice, France, June 200
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Changes in aroma and sensory profile of food ingredients smoked in the presence of a zeolite filter
During smoking, formation of desirable smoky compounds and carcinogenic polycyclic aromatic hydrocarbons (PAH) are inextricably linked. We have previously developed a zeolite filter technology (PureSmoke Technology or PST) that reduces the PAH content of a smoke stream, particularly reducing the concentration of benzo[a]pyrene, a known carcinogen, by up to 93%. The aim of this work was to determine whether there were changes in the volatile and sensory profiles of ingredients smoked using PST compared to the traditional smoking process (Trad). Smoked tomato flakes (either PST or Trad) were added to either low-fat or full-fat cream cheese for sensory profiling and consumer preference tests, and volatile analysis was carried out using solid phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS). The sensory analysis showed a significant decrease (p < 0.01) in bitterness when the PST was employed and a significant decrease in overall smoky aroma and flavor (p < 0.001), which resulted in an increase in the perception of cheesy aroma and flavor. This was consistent with a decrease in many of the smoky aroma compounds, particularly the guaiacols. However, consumer preference tests showed that there was no adverse effect on the flavor of the products, and there was even a tendency for the PST product to be preferred to the Trad product (p = 0.096). The smoke compounds were quantitated and compared in smoked tomato paste. Odor activity values (OAVs) calculated from the literature thresholds suggested that guaiacol and 4-alk(en)yl-substituted guaiacols are likely to be among the most highly odor-active compounds in these smoked ingredients
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