A Turbo-Detection Aided Serially Concatenated MPEG-4/TCM Videophone Transceiver

A Turbo-detection aided serially concatenated inner Trellis Coded Modulation (TCM) scheme is combined with four different outer codes, namely with a Reversible Variable Length Code (RVLC), a Non-Systematic Convolutional (NSC) code a Recursive Systematic Convolutional (RSC) code or a Low Density Parity Check (LDPC) code. These four outer constituent codes are comparatively studied in the context of an MPEG4 videophone transceiver. These serially concatenated schemes are also compared to a stand-alone LDPC coded MPEG4 videophone system at the same effective overall coding rate. The performance of the proposed schemes is evaluated when communicating over uncorrelated Rayleigh fading channels. It was found that the serially concatenated TCM-NSC scheme was the most attractive one in terms of coding gain and decoding complexity among all the schemes considered in the context of the MPEG4 videophone transceiver. By contrast, the serially concatenated TCM-RSC scheme was found to attain the highest iteration gain among the schemes considered

Strain-stress study of AlxGa1-xN/AlN heterostructures on c-plane sapphire and related optical properties

This work presents a systematic study of stress and strain of AlxGa1-xN/AlN with composition ranging from GaN to AlN, grown on a c-plane sapphire by metal-organic chemical vapor deposition, using synchrotron radiation high-resolution X-ray diffraction and reciprocal space mapping. The c-plane of the AlxGa1-xN epitaxial layers exhibits compressive strain, while the a-plane exhibits tensile strain. The biaxial stress and strain are found to increase with increasing Al composition, although the lattice mismatch between the AlxGa1-xN and the buffer layer AlN gets smaller. A reduction in the lateral coherence lengths and an increase in the edge and screw dislocations are seen as the AlxGa1-xN composition is varied from GaN to AlN, exhibiting a clear dependence of the crystal properties of AlxGa1-xN on the Al content. The bandgap of the epitaxial layers is slightly lower than predicted value due to a larger tensile strain effect on the a-axis compared to the compressive strain on the c-axis. Raman characteristics of the AlxGa1-xN samples exhibit a shift in the phonon peaks with the Al composition. The effect of strain is also discussed on the optical phonon energies of the epitaxial layers. The techniques discussed here can be used to study other similar materials.Comment: 14 pages, 5 figures, 2 table

The Hierarchy Problem and the Top Yukawa: An Alternative to Top Partner Solutions

We discuss the role of the top-quark Yukawa coupling $y_t$ concerning thehierarchy problem and construct an alternative scheme to the conventionalsolutions with top partners. In traditional models, like SUSY or compositeHiggs, top partners cancel the top loop contribution to the Higgs quadraticterm. The lack of evidence for such colored partners however drives thesemodels into more and more fine-tuned regions. Here, an alternative means tomitigate the top loop, allowing for natural electroweak symmetry breaking, ispresented. Emphasizing that we have not measured the top-Higgs interactions athigh scales yet, we envisage scenarios where this interaction is onlyapproaching its sizable strength in the infra-red, but gets strongly suppressedat high scales. We first discuss possible effects via a modification of therunning of the top Yukawa coupling. Then, we turn to models where the topYukawa is generated at one-loop level. Originated from a dimension-sixoperator, it drops when crossing the mass threshold of new degrees of freedom.In either case, the top partners are replaced by some new top-philic particleswith strong interaction. Thus, a very different phenomenology, such as largetop mass running and signals in four top final states, is introduced, whichwill be discussed in detail. With the assistance of this mechanism, thesolution to the hierarchy problem can be pushed to a (well-defined) higherscale, and a final test of naturalness might be deferred to a 100 TeV Collider,like the FCC.<br

The Hierarchy Problem and the Top Yukawa: An Alternative to Top Partner Solutions

We discuss the role of the top-quark Yukawa coupling $y_t$ concerning thehierarchy problem and construct an alternative scheme to the conventionalsolutions with top partners. In traditional models, like SUSY or compositeHiggs, top partners cancel the top loop contribution to the Higgs quadraticterm. The lack of evidence for such colored partners however drives thesemodels into more and more fine-tuned regions. Here, an alternative means tomitigate the top loop, allowing for natural electroweak symmetry breaking, ispresented. Emphasizing that we have not measured the top-Higgs interactions athigh scales yet, we envisage scenarios where this interaction is onlyapproaching its sizable strength in the infra-red, but gets strongly suppressedat high scales. We first discuss possible effects via a modification of therunning of the top Yukawa coupling. Then, we turn to models where the topYukawa is generated at one-loop level. Originated from a dimension-sixoperator, it drops when crossing the mass threshold of new degrees of freedom.In either case, the top partners are replaced by some new top-philic particleswith strong interaction. Thus, a very different phenomenology, such as largetop mass running and signals in four top final states, is introduced, whichwill be discussed in detail. With the assistance of this mechanism, thesolution to the hierarchy problem can be pushed to a (well-defined) higherscale, and a final test of naturalness might be deferred to a 100 TeV Collider,like the FCC.<br

Network Structure, Topology and Dynamics in Generalized Models of Synchronization

We explore the interplay of network structure, topology, and dynamic interactions between nodes using the paradigm of distributed synchronization in a network of coupled oscillators. As the network evolves to a global steady state, interconnected oscillators synchronize in stages, revealing network's underlying community structure. Traditional models of synchronization assume that interactions between nodes are mediated by a conservative process, such as diffusion. However, social and biological processes are often non-conservative. We propose a new model of synchronization in a network of oscillators coupled via non-conservative processes. We study dynamics of synchronization of a synthetic and real-world networks and show that different synchronization models reveal different structures within the same network

Z3-graded Grassmann Variables, Parafermions and their Coherent States

A relation between the $Z_3$-graded Grassmann variables and parafermions is established. Coherent states are constructed as a direct consequence of such a relationship. We also give the analog of the Bargmann-Fock representation in terms of these Grassmann variables.Comment: 8 page