5,307 research outputs found
The Impact of User Effects on the Performance of Dual Receive Antenna Diversity Systems in Flat Rayleigh Fading Channels
In this paper we study the impact of user effects on the performance of receive antenna diversity systems in flat Rayleigh fading channels. Three diversity combining techniques are compared: maximal ratio combining (MRC), equal gain combining (EGC), and selection combining (SC). User effects are considered in two scenarios: 1) body loss (the reduction of effective antenna gain due to user effects) on a single antenna, and 2) equal body loss on both antennas. The system performance is assessed in terms of mean SNR, link reliability, bit error rate of BPSK, diversity order and ergodic capacity. Our results show that body loss on a single antenna has limited (bounded) impact on system performance. In comparison, body loss on both antennas has unlimited (unbounded) impact and can severely degrade system performance. Our results also show that with increasing body loss on a single antenna the performance of EGC drops faster than that of MRC and SC. When body loss on a single antenna is larger than a certain level, EGC is not a “sub-optimal” method anymore and has worse performance than SC
The non-existence of stable Schottky forms
Let be the Satake compactification of the moduli space of
principally polarized abelian -folds and the closure of the image of
the moduli space of genus curves in under the Jacobian
morphism. Then lies in the boundary of for any . We
prove that and do not meet transversely in , but
rather that their intersection contains the th order infinitesimal
neighbourhood of in . We deduce that there is no non-trivial
stable Siegel modular form that vanishes on for every . In particular,
given two inequivalent positive even unimodular quadratic forms and ,
there is a curve whose period matrix distinguishes between the theta series of
and .Comment: Corrected version, using Yamada's correct version of Fay's formula
for the period matrix of a certain degenerating family of curves. To appear
in Compositio Mathematic
Probing Hadronic Structure with The Decay
We compute the branching ratio for and
in chiral perturbation theory and find that
both decays should be observable at CEBAF. With sufficiently low thresholds on
the invariant mass a branching ratio of may be observed
for . For the decay
mode we predict a branching ratio of . The dependence of the
M1 and E2 amplitudes on the momentum transfer will provide a useful test of
chiral perturbation theory which predicts variation over the
allowed kinematic range.Comment: 6 pages, 3 figures, UCSD/PTH 93-06, QUSTH-93-02, Duke-TH-93-4
Noiseless Quantum Circuits for the Peres Separability Criterion
In this Letter we give a method for constructing sets of simple circuits that
can determine the spectrum of a partially transposed density matrix, without
requiring either a tomographically complete POVM or the addition of noise to
make the spectrum non-negative. These circuits depend only on the dimension of
the Hilbert space and are otherwise independent of the state.Comment: 4 pages RevTeX, 7 figures encapsulated postscript. v5: title changed
slightly, more-or-less equivalent to the published versio
Radiative Decays X(3872) -> psi(2S)+gamma and psi(4040) -> X(3872)+gamma in Effective Field Theory
Heavy hadron chiral perturbation theory (HHchiPT) and XEFT are applied to the
decays X(3872) -> psi(2S) + gamma and psi(4040) -> X(3872) + gamma under the
assumption that the X(3872) is a molecular bound state of neutral charm mesons.
In these decays the emitted photon energies are 181 MeV and 165 MeV,
respectively, so HHchiPT can be used to calculate the underlying D^0
bar{D}^{0*}+ bar{D}^0 D^{0*} -> psi(2S) + gamma or psi(4040) -> (D^0
bar{D}^{0*}+ bar{D}^0 D^{0*}) + gamma transition. These amplitudes are matched
onto XEFT to obtain decay rates. The decays receive contributions from both
long distance and short distance processes. We study the polarization of the
psi(2S) in the decay X(3872) -> psi(2S) + gamma and the angular distribution of
X(3872) in the decay psi(4040) -> X(3872) + gamma and find they can be used to
differentiate between different decay mechanisms as well as discriminate
between 2^{-+} and 1^{++} quantum number assignments of the X(3872).Comment: 13 pages, 4 figure
Cohomology of the minimal nilpotent orbit
We compute the integral cohomology of the minimal non-trivial nilpotent orbit
in a complex simple (or quasi-simple) Lie algebra. We find by a uniform
approach that the middle cohomology group is isomorphic to the fundamental
group of the sub-root system generated by the long simple roots. The modulo
reduction of the Springer correspondent representation involves the sign
representation exactly when divides the order of this cohomology group.
The primes dividing the torsion of the rest of the cohomology are bad primes.Comment: 29 pages, v2 : Leray-Serre spectral sequence replaced by Gysin
sequence only, corrected typo
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Dynamic Patterns of Transcript Abundance of Transposable Element Families in Maize.
Transposable Elements (TEs) are mobile elements that contribute the majority of DNA sequences in the maize genome. Due to their repetitive nature, genomic studies of TEs are complicated by the difficulty of properly attributing multi-mapped short reads to specific genomic loci. Here, we utilize a method to attribute RNA-seq reads to TE families rather than particular loci in order to characterize transcript abundance for TE families in the maize genome. We applied this method to assess per-family expression of transposable elements in >800 published RNA-seq libraries representing a range of maize development, genotypes, and hybrids. While a relatively small proportion of TE families are transcribed, expression is highly dynamic with most families exhibiting tissue-specific expression. A large number of TE families were specifically detected in pollen and endosperm, consistent with reproductive dynamics that maintain silencing of TEs in the germ line. We find that B73 transcript abundance is a poor predictor of TE expression in other genotypes and that transcript levels can differ even for shared TEs. Finally, by assessing recombinant inbred line and hybrid transcriptomes, complex patterns of TE transcript abundance across genotypes emerged. Taken together, this study reveals a dynamic contribution of TEs to maize transcriptomes
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