17,838 research outputs found
MIMO capacity for deterministic channel models: sublinear growth
This is the second paper of the authors in a series concerned with the
development of a deterministic model for the transfer matrix of a MIMO system.
Starting from the Maxwell equations, we have described in \cite{BCFM} the
generic structure of such a deterministic transfer matrix. In the current paper
we apply the results of \cite{BCFM} in order to study the (Shannon-Foschini)
capacity behavior of a MIMO system as a function of the deterministic spread
function of the environment, and the number of transmitting and receiving
antennas. The antennas are assumed to fill in a given, fixed volume. Under some
generic assumptions, we prove that the capacity grows much more slowly than
linearly with the number of antennas. These results reinforce previous
heuristic results obtained from statistical models of the transfer matrix,
which also predict a sublinear behavior.Comment: 12 pages, to appear in Math. Meth. Appl. Sc
Disentangle the nature of resonances in coupled-channel models
We present several possible hadronic states found in coupled-channel models
within the on-shell approximation. The interaction potential is constructed as
a sum of the tree-level Feynman diagrams calculated with the effective
Lagrangians. Based on the recent empirical data, we illustrate the possible
existence of several baryonic and mesonic states with definite quantum numbers
in the model. We give their properties for the purpose of further study and
discuss the potential of finding them in future experiments.Comment: values in table update
Nucleon Resonances with Hidden Charm in Coupled-Channel Models
The model dependence of the predictions of nucleon resonances with hidden
charm is investigated. We consider several coupled-channel models which are
derived from relativistic quantum field theory by using (1) a unitary
transformation method, and (2) the three-dimensional reductions of
Bethe-Salpeter Equation. With the same vector meson exchange mechanism, we find
that all models give very narrow molecular-like nucleon resonances with hidden
charm in the mass range of 4.3 GeV 4.5 GeV, in consistent with the
previous predictions.Comment: 17 pages, 3 figure
RFI channels
A class of channel models is presented which exhibit varying burst error severity much like channels encountered in practice. An information-theoretic analysis of these channel models is made, and conclusions are drawn that may aid in the design of coded communication systems for realistic noisy channels
Finite-State Channel Models for Signal Transduction in Neural Systems
Information theory provides powerful tools for understanding communication
systems. This analysis can be applied to intercellular signal transduction,
which is a means of chemical communication among cells and microbes. We discuss
how to apply information-theoretic analysis to ligand-receptor systems, which
form the signal carrier and receiver in intercellular signal transduction
channels. We also discuss the applications of these results to neuroscience.Comment: Accepted for publication in 2016 IEEE International Conference on
Acoustics, Speech, and Signal Processing, Shanghai, Chin
Monojet versus rest of the world I: t-channel Models
Monojet searches using Effective Field Theory (EFT) operators are usually
interpreted as a robust and model independent constraint on direct detection
(DD) scattering cross-sections. At the same time, a mediator particle must be
present to produce the dark matter (DM) at the LHC. This mediator particle may
be produced on shell, so that direct searches for the mediating particle can
constrain the effective operator being applied to monojet constraints. In this
first paper, we do a case study on t-channel models in monojet searches, where
the (Standard Model singlet) DM is pair produced via a t-channel mediating
particle, whose supersymmetric analogue is the squark. We compare monojet
constraints to direct constraints on single or pair production of the mediator
from multi-jets plus missing energy searches and we identify the regions where
the latter dominate over the former. We show that computing bounds using
supersymmetric simplified models and in the narrow width approximation, as done
in previous work in the literature, misses important quantitative effects. We
perform a full event simulation and statistical analysis, and we compute the
effects of both on- and off-shell production of the mediating particle, showing
that for both the monojet and multi-jets plus missing energy searches,
previously derived bounds provided more conservative bounds than what can be
extracted by including all relevant processes in the simulation. Monojets and
searches for supersymmetry (SUSY) provide comparable bounds on a wide range of
the parameter space, with SUSY searches usually providing stronger bounds,
except in the regions where the DM particle and the mediator are very mass
degenerate. The EFT approximation rarely is able to reproduce the actual
limits. In a second paper to follow, we consider the case of s-channel
mediators.Comment: 22 pages + appendices, 10 figure
Channels with block interference
A new class of channel models with memory is presented in order to study various kinds of interference phenomena. It is shown, among other things, that when all other parameters are held fixed, channel capacity C is an increasing function of the memory length, while the cutoff rate R0 generally is a decreasing function. Calculations with various explicit coding schemes indicate that C is better than R0 as a performance measure for these channel models. As a partial resolution of this C versus R0 paradox, the conjecture is offered that R0 is more properly a measure of coding delay rather than of coding complexity
- …