1,056 research outputs found
IceCube and HAWC constraints on very-high-energy emission from the Fermi bubbles
The nature of the -ray emission from the \emph{Fermi} bubbles is
unknown. Both hadronic and leptonic models have been formulated to explain the
peculiar -ray signal observed by the Fermi-LAT between 0.1-500~GeV. If
this emission continues above 30~TeV, hadronic models of the \emph{Fermi}
bubbles would provide a significant contribution to the high-energy neutrino
flux detected by the IceCube observatory. Even in models where leptonic
-rays produce the \emph{Fermi} bubbles flux at GeV energies, a hadronic
component may be observable at very high energies. The combination of IceCube
and HAWC measurements have the ability to distinguish these scenarios through a
comparison of the neutrino and -ray fluxes at a similar energy scale.
We examine the most recent four-year dataset produced by the IceCube
collaboration and find no evidence for neutrino emission originating from the
\emph{Fermi} bubbles. In particular, we find that previously suggested excesses
are consistent with the diffuse astrophysical background with a p-value of 0.22
(0.05 in an extreme scenario that all the IceCube events that overlap with the
bubbles come from them). Moreover, we show that existing and upcoming HAWC
observations provide independent constraints on any neutrino emission from the
\emph{Fermi} bubbles, due to the close correlation between the -ray and
neutrino fluxes in hadronic interactions. The combination of these results
disfavors a significant contribution from the \emph{Fermi} bubbles to the
IceCube neutrino flux.Comment: 9 pages, 4 figures, to appear in PR
Design of Block Transceivers with Decision Feedback Detection
This paper presents a method for jointly designing the transmitter-receiver
pair in a block-by-block communication system that employs (intra-block)
decision feedback detection. We provide closed-form expressions for
transmitter-receiver pairs that simultaneously minimize the arithmetic mean
squared error (MSE) at the decision point (assuming perfect feedback), the
geometric MSE, and the bit error rate of a uniformly bit-loaded system at
moderate-to-high signal-to-noise ratios. Separate expressions apply for the
``zero-forcing'' and ``minimum MSE'' (MMSE) decision feedback structures. In
the MMSE case, the proposed design also maximizes the Gaussian mutual
information and suggests that one can approach the capacity of the block
transmission system using (independent instances of) the same (Gaussian) code
for each element of the block. Our simulation studies indicate that the
proposed transceivers perform significantly better than standard transceivers,
and that they retain their performance advantages in the presence of error
propagation.Comment: 14 pages, 8 figures, to appear in the IEEE Transactions on Signal
Processin
2D-FFTLog: Efficient computation of real space covariance matrices for galaxy clustering and weak lensing
Accurate covariance matrices for two-point functions are critical for
inferring cosmological parameters in likelihood analyses of large-scale
structure surveys. Among various approaches to obtaining the covariance,
analytic computation is much faster and less noisy than estimation from data or
simulations. However, the transform of covariances from Fourier space to real
space involves integrals with two Bessel integrals, which are numerically slow
and easily affected by numerical uncertainties. Inaccurate covariances may lead
to significant errors in the inference of the cosmological parameters. In this
paper, we introduce a 2D-FFTLog algorithm for efficient, accurate and
numerically stable computation of non-Gaussian real space covariances for both
3D and projected statistics. The 2D-FFTLog algorithm is easily extended to
perform real space bin-averaging. We apply the algorithm to the covariances for
galaxy clustering and weak lensing for a Dark Energy Survey Year 3-like and a
Rubin Observatory's Legacy Survey of Space and Time Year 1-like survey, and
demonstrate that for both surveys, our algorithm can produce numerically stable
angular bin-averaged covariances with the flat sky approximation, which are
sufficiently accurate for inferring cosmological parameters. The code CosmoCov
for computing the real space covariances with or without the flat sky
approximation is released along with this paper.Comment: MNRAS accepted; 13 pages, 3 figures, 2 tables; fixed a typo in Eq.41;
2DFFTLog code available at https://github.com/xfangcosmo/2DFFTLog ; 3x2pt
covariance code CosmoCov at https://github.com/CosmoLike/CosmoCo
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