17,894 research outputs found
Colour Fields Computed in SU(3) Lattice QCD for the Static Tetraquark System
The colour fields created by the static tetraquark system are computed in
quenched SU(3) lattice QCD, in a 24^3 x 48 lattice at beta=6.2 corresponding to
a lattice spacing a=0.07261(85) fm. We find that the tetraquark colour fields
are well described by a double-Y, or butterfly, shaped flux tube. The two flux
tube junction points are compatible with Fermat points minimizing the total
flux tube length. We also compare the diquark-diantiquark central flux tube
profile in the tetraquark with the quark-antiquark fundamental flux tube
profile in the meson, and they match, thus showing that the tetraquark flux
tubes are composed of fundamental flux tubes.Comment: 5 pages, 7 figures, 0 tables, one reference added, work done partly
under the PT-LQCD Collaboratio
Cooperative Spectrum Sensing Using Random Matrix Theory
In this paper, using tools from asymptotic random matrix theory, a new
cooperative scheme for frequency band sensing is introduced for both AWGN and
fading channels. Unlike previous works in the field, the new scheme does not
require the knowledge of the noise statistics or its variance and is related to
the behavior of the largest and smallest eigenvalue of random matrices.
Remarkably, simulations show that the asymptotic claims hold even for a small
number of observations (which makes it convenient for time-varying topologies),
outperforming classical energy detection techniques.Comment: Submitted to International Symposium on Wireless Pervasive Computing
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Automatic speaker segmentation using multiple features and distance measures: a comparison of three approaches
This paper addresses the problem of unsupervised speaker change detection. Three systems based on the Bayesian Information Criterion (BIC) are tested. The first system investigates the AudioSpectrumCentroid and the AudioWaveformEnvelope features, implements a dynamic thresholding followed by a fusion scheme, and finally applies BIC. The second method is a real-time one that uses a metric-based approach employing the line spectral pairs and the BIC to validate a potential speaker change point. The third method consists of three modules. In the first module, a measure based on second-order statistics is used; in the second module, the Euclidean distance and T2 Hotelling statistic are applied; and in the third module, the BIC is utilized. The experiments are carried out on a dataset created by concatenating speakers from the TIMIT database, that is referred to as the TIMIT data set. A comparison between the performance of the three systems is made based on t-statistics
Probing the infrared quark mass from highly excited baryons
We argue that three-quark excited states naturally group into quartets, split
into two parity doublets, and that the mass splittings between these parity
partners decrease higher up in the baryon spectrum. This decreasing mass
difference can be used to probe the running quark mass in the mid-infrared
power-law regime. A measurement of masses of high-partial wave Delta*
resonances should be sufficient to unambiguously establish the approximate
degeneracy. We test this concept with the first computation of excited high-j
baryon masses in a chirally invariant quark model.Comment: 4 pages, 4 figures. submitted to Phys Rev Letter
Using highly excited baryons to catch the quark mass
Chiral symmetry in QCD can be simultaneously in Wigner and Goldstone modes,
depending on the part of the spectrum examined. The transition regime between
both, exploiting for example the onset of parity doubling in the high baryon
spectrum, can be used to probe the running quark mass in the mid-IR power-law
regime. In passing we also argue that three-quark states naturally group into
same-flavor quartets, split into two parity doublets, all splittings decreasing
high in the spectrum. We propose that a measurement of masses of high-partial
wave Delta* resonances should be sufficient to unambiguously establish the
approximate degeneracy and see the quark mass running. We test these concepts
with the first computation of the spectrum of high-J excited baryons in a
chiral-invariant quark model.Comment: 6 pages, 9 figures, To appear in the proceedings of the 19th
International IUPAP Conference on Few-Body Problems in Physics; added
acknowledgment, hyphenized author nam
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