A Multi-Kernel Multi-Code Polar Decoder Architecture

Polar codes have received increasing attention in the past decade, and have been selected for the next generation of wireless communication standard. Most research on polar codes has focused on codes constructed from a $2\times2$ polarization matrix, called binary kernel: codes constructed from binary kernels have code lengths that are bound to powers of $2$. A few recent works have proposed construction methods based on multiple kernels of different dimensions, not only binary ones, allowing code lengths different from powers of $2$. In this work, we design and implement the first multi-kernel successive cancellation polar code decoder in literature. It can decode any code constructed with binary and ternary kernels: the architecture, sized for a maximum code length $N_{max}$, is fully flexible in terms of code length, code rate and kernel sequence. The decoder can achieve frequency of more than $1$ GHz in $65$ nm CMOS technology, and a throughput of $615$ Mb/s. The area occupation ranges between $0.11$ mm$^2$ for $N_{max}=256$ and $2.01$ mm$^2$ for $N_{max}=4096$. Implementation results show an unprecedented degree of flexibility: with $N_{max}=4096$, up to $55$ code lengths can be decoded with the same hardware, along with any kernel sequence and code rate

ρ\rho-mass Modification in He3He^3 - a Signal of Restoration of Chiral Symmetry or Test for Nuclear Matter Models ?

Two recent experiments have demonstrated that the effective $\rho$-mass in nuclear medium, as extracted from the $^3He(\gamma, \pi^+ \pi^-)$ reaction, is substantially reduced. This has been advocated as an indication of partial restoration of chiral symmetry in nuclear matter. We show that even in the absence of chiral symmetry, effective mean field nuclear matter models can explain these findings quantitatively.Comment: ReVTeX file with 2 postscript figures include

Quark Dispersion Relation and Dilepton Production in the Quark-Gluon Plasma

Under very general assumptions we show that the quark dispersion relation in the quark-gluon plasma is given by two collective branches, of which one has a minimum at a non-vanishing momentum. This general feature of the quark dispersion relation leads to structures (van Hove singularities, gaps) in the low mass dilepton production rate, which might provide a unique signature for the quark-gluon plasma formation in relativistic heavy ion collisions.Comment: 6 pages, Revtex, 2 PostScript figures, revised version to be published in Phys. Rev. Let

Medium effect on photon production in ultrarelativistic nuclear collisions

The effect of in-medium vector and axial-vector meson masses on photon production is studied. We assume that the effective mass of a vector meson in hot nuclear matter decreases according to a universal scaling law, while that of an axial-vector meson is given by Weinberg's mass formula. We find that the thermal production rate of photons increases with reduced masses, and is enhanced by an order of magnitude at T=160 MeV with $m_\rho=300$ MeV. Assuming a hydrodynamic evolution, we estimate the effect of the reduced masses on photon production in nucleus-nucleus collisions. The result is compared to experimental data from the WA80/WA98 collaboration.Comment: 21 pages, REVTEX + 9 figures (ps file

Theoretical Interpretation of Low-Mass Dileptons

An overview is given of chiral symmetry restoration at finite temperature and baryochemical potential. Within hadronic models of the vector correlator its implications for low-mass dilepton spectra in ultrarelativistic heavy-ion collisions are discussed.Comment: 12 pages LaTeX, incl. 12 ps-/eps-figures and espcrc1.st

Dilepton and Photon Emission Rates from a Hadronic Gas

We analyze the dilepton and photon emission rates from a hadronic gas using chiral reduction formulas and a virial expansion. The emission rates are reduced to pertinent vacuum correlation functions, most of which can be assessed from experiment. Our results indicate that in the low mass region, the dilepton and photon rates are enhanced compared to most of the calculations using chiral Lagrangians. The enhancement is further increased through a finite pion chemical potential. An estimate of the emission rates is also made using Haag's expansion for the electromagnetic current. The relevance of these results to dilepton and photon emission rates in heavy-ion collisions is discussed.Comment: 7 pages, LaTeX using revTeX, 6 figures imbedded in text. Figures slightly changed, text left unchange

Lepton-pair production in nuclear collisions - past, present, future

The key results on lepton-pair production in ultra-relativistic nuclear collisions are shortly reviewed, starting at the roots of pp collisions in the seventies, and ending at the perspectives of the colliders RHIC and LHC. The presence is dominated by the recent precision results from NA60 at the CERN SPS, culminating in the first measurement of the in-medium rho spectral function and the transverse flow of the associated thermal radiation. The seeming cut-off of the flow above the rho may well be the first direct hint for thermal radiation of partonic origin in nuclear collisions. The major milestones in the theoretical developments are also covered.Comment: Invited talk at INPC07, Tokyo, June 3-8, 200

Dilepton and Photon Emission Rates from a Hadronic Gas III

We extend our early analyses of the dilepton and photon emission rates from a hadronic gas to account for strange mesons using a density expansion. The emission rates are reduced to vacuum correlation functions using three-flavor chiral reduction formulas, and the latters are assessed in terms of empirical data. Using a fire-ball, we compare our results to the low and intermediate mass dilepton data available from CERN. Our results suggest that a baryon free hadronic gas does not account for the excess of low mass dielectrons observed at CERES but do well in accounting for the intermediate dimuons at HELIOS. The same observations apply to the recent low and high $p_t$ dielectron rates from CERES.Comment: 12 pages LaTeX, 11 eps figure