35,427 research outputs found
Symmetric complex-valued RBF receiver for multiple-antenna aided wireless systems
A nonlinear beamforming assisted detector is proposed for multiple-antenna-aided wireless systems employing complex-valued quadrature phase shift-keying modulation. By exploiting the inherent symmetry of the optimal Bayesian detection solution, a novel complex-valued symmetric radial basis function (SRBF)-network-based detector is developed, which is capable of approaching the optimal Bayesian performance using channel-impaired training data. In the uplink case, adaptive nonlinear beamforming can be efficiently implemented by estimating the system’s channel matrix based on the least squares channel estimate. Adaptive implementation of nonlinear beamforming in the downlink case by contrast is much more challenging, and we adopt a cluster-variationenhanced clustering algorithm to directly identify the SRBF center vectors required for realizing the optimal Bayesian detector. A simulation example is included to demonstrate the achievable performance improvement by the proposed adaptive nonlinear beamforming solution over the theoretical linear minimum bit error rate beamforming benchmark
A feasibility study of the measurement of Higgs pair creation at a Photon Linear Collider
We studied the feasibility of the measurement of Higgs pair creation at a
Photon Linear Collider (PLC). From the sensitivity to the anomalous
self-coupling of the Higgs boson, the optimum collision energy
was found to be around 270 GeV for a Higgs mass of 120 GeV/. We found that
large backgrounds such as and
, can be suppressed if correct assignment of tracks to parent
partons is achieved and Higgs pair events can be observed with a statistical
significance of by operating the PLC for 5 years.Comment: 7 pages, 8 figures, 5 table
Community Detection in Quantum Complex Networks
Determining community structure is a central topic in the study of complex
networks, be it technological, social, biological or chemical, in static or
interacting systems. In this paper, we extend the concept of community
detection from classical to quantum systems---a crucial missing component of a
theory of complex networks based on quantum mechanics. We demonstrate that
certain quantum mechanical effects cannot be captured using current classical
complex network tools and provide new methods that overcome these problems. Our
approaches are based on defining closeness measures between nodes, and then
maximizing modularity with hierarchical clustering. Our closeness functions are
based on quantum transport probability and state fidelity, two important
quantities in quantum information theory. To illustrate the effectiveness of
our approach in detecting community structure in quantum systems, we provide
several examples, including a naturally occurring light-harvesting complex,
LHCII. The prediction of our simplest algorithm, semiclassical in nature,
mostly agrees with a proposed partitioning for the LHCII found in quantum
chemistry literature, whereas our fully quantum treatment of the problem
uncovers a new, consistent, and appropriately quantum community structure.Comment: 16 pages, 4 figures, 1 tabl
Artificial intelligence in the cyber domain: Offense and defense
Artificial intelligence techniques have grown rapidly in recent years, and their applications in practice can be seen in many fields, ranging from facial recognition to image analysis. In the cybersecurity domain, AI-based techniques can provide better cyber defense tools and help adversaries improve methods of attack. However, malicious actors are aware of the new prospects too and will probably attempt to use them for nefarious purposes. This survey paper aims at providing an overview of how artificial intelligence can be used in the context of cybersecurity in both offense and defense.Web of Science123art. no. 41
Self-interacting asymmetric dark matter coupled to a light massive dark photon
Dark matter (DM) with sizeable self-interactions mediated by a light species
offers a compelling explanation of the observed galactic substructure;
furthermore, the direct coupling between DM and a light particle contributes to
the DM annihilation in the early universe. If the DM abundance is due to a dark
particle-antiparticle asymmetry, the DM annihilation cross-section can be
arbitrarily large, and the coupling of DM to the light species can be
significant. We consider the case of asymmetric DM interacting via a light (but
not necessarily massless) Abelian gauge vector boson, a dark photon. In the
massless dark photon limit, gauge invariance mandates that DM be
multicomponent, consisting of positive and negative dark ions of different
species which partially bind in neutral dark atoms. We argue that a similar
conclusion holds for light dark photons; in particular, we establish that the
multi-component and atomic character of DM persists in much of the parameter
space where the dark photon is sufficiently light to mediate sizeable DM
self-interactions. We discuss the cosmological sequence of events in this
scenario, including the dark asymmetry generation, the freeze-out of
annihilations, the dark recombination and the phase transition which gives mass
to the dark photon. We estimate the effect of self-interactions in DM haloes,
taking into account this cosmological history. We place constraints based on
the observed ellipticity of large haloes, and identify the regimes where DM
self-scattering can affect the dynamics of smaller haloes, bringing theory in
better agreement with observations. Moreover, we estimate the cosmological
abundance of dark photons in various regimes, and derive pertinent bounds.Comment: v3: published versio
- …