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We identify a canonical transformation which maps the chiral Gross-Neveu model onto a recently proposed Cooper pair model. Baryon number and axial charge are interchanged. The same physics can be described either as chiral symmetry breaking (quark-antiquark pairing) or as superconductivity (quark-quark pairing)., 3 pages, no figures, Revtex; v2: one reference added

It is shown that an effective theory with meron degrees of freedom produces confinement in SU(2) Yang Mills theory. This effective theory is compatible with center symmetry. When the scale is set by the string tension, the action density and topological susceptibility are similar to those arising in lattice QCD., Comment: 4 pages, 2 figures

Chiral condensates in the trivial light-cone vacuum emerge if defined as short-time limits of fermion propagators. In gauge theories, the necessary inclusion of a gauge string in combination with the characteristic light-cone infrared singularities contain the relevant nonperturbative ingredients responsible for the formation of the condensate, as demonstrated for the 't Hooft model.

In this paper, we present an efficient exploration algorithm for architecture/compiler co-designs of application-specific instruction-set processors. The huge design space is spanned by processor architecture parameters as well as different compiler optimization strategies. The objective space is multi-dimensional including conflicting objectives such as hardware cost, execution time and code size. The goal of the presented exploration algorithm is to determine the set of Pareto-optimal designs and compiler settings for a given benchmark program.In a case study, while exploring Pareto-optimal designs for a given DSP benchmark program, we show that for a realistic architecture family, the huge search space may be reduced dramatically using proper techniques to prune search spaces that may not contain Pareto-optimal solutions. Finally, we analyse and present solutions on what is the best architecture for a mixture of benchmark programs, i.e., what are the best architecture/compiler co-designs to execute the DSPstone benchmark.

Within a variational calculation we investigate the role of baryons for the structure of dense matter in the Gross-Neveu model. We construct a trial ground state at finite baryon density which breaks translational invariance. Its scalar potential interpolates between widely spaced kinks and antikinks at low density and the value zero at infinite density. Its energy is lower than the one of the standard Fermi gas at all densities considered. This suggests that the discrete gamma_5 symmetry of the Gross-Neveu model does not get restored in a first order phase transition at finite density, at variance with common wisdom., 16 pages, 7 figures, LaTeX

In certain 1+1 dimensional field theoretic toy models, one can go all the way from microscopic quarks via the hadron spectrum to the properties of hot and dense baryonic matter in an essentially analytic way. This "miracle" is illustrated through case studies of two popular large N models, the Gross-Neveu and the 't Hooft model - caricatures of the Nambu-Jona-Lasinio model and real QCD, respectively. The main emphasis will be on aspects related to spontaneous symmetry breaking (discrete or continuous chiral symmetry, translational invariance) and confinement.

In light-cone quantization, the standard procedure to characterize the phases of a system by appropriate ground state expectation values fails. The light-cone vacuum is determined kinematically. We show that meaningful quantities which can serve as order parameters are obtained as expectation values of Heisenberg operators in the equal (light-cone) time limit. These quantities differ from the purely kinematical expectation values of the corresponding Schroedinger operators. For the Nambu--Jona-Lasinio and the Gross-Neveu model, we describe the spontaneous breakdown of chiral symmetry; we derive within light-cone quantization the corresponding gap equations and the values of the chiral condensate., Latex, 9 pages, no figure

In the design of application-specific instruction set processors (ASIPs) a tight interplay between architecture and compiler is of utmost importance. Here, we try to characterize the design space of both compiler frontend (intermediate code optimization) and backend (architecture-specific code generation) that is used in order to do Architecture/Compiler Co-Exploration for the search of optimal architecture/compiler combinations. The described results present the state of development of such a framework called BUILDABONG [3].

After elimination of the redundant variables, gauge theories may still exhibit symmetries associated with the gauge fields. The role of these residual gauge symmetries is discussed within the Abelian Higgs model and the Georgi-Glashow model. In the different phases of these models, these symmetries are realized differently. The characteristics of emergence and disappearance of the symmetries are studied in detail and the implications for the dynamics in Coulomb, Higgs, and confining phases are discussed., 30 pages, LaTeX with amsmath macros; updated to include minor corrections in proof; email correspondence to J.W. Negele, negele@mitlns.mit.edu

We study two-dimensional, large $N$ field theoretic models (Gross-Neveu model, 't Hooft model) at finite baryon density near the chiral limit. The same mechanism which leads to massless baryons in these models induces a breakdown of translational invariance at any finite density. In the chiral limit baryonic matter is characterized by a spatially varying chiral angle with a wave number depending only on the density. For small bare quark masses a sine-Gordon kink chain is obtained which may be regarded as simplest realization of the Skyrme crystal for nuclear matter. Characteristic differences between confining and non-confining models are pointed out., 27 pages, 11 figures, added reference, corrected sign

QCD_2 with fundamental quarks on a cylinder is solved to leading order in the 1/N expansion, including the zero mode gluons. As a result of the non-perturbative dynamics of these gauge degrees of freedom, the compact space-time direction gets effectively decompactified. In a thermodynamic interpretation, this implies that there is no pressure of order N and that the chiral condensate of order N is temperature independent. These findings are consistent with confinement of quarks, rule out both chiral and deconfining phase transitions in the finite temperature 't Hooft model, and help to resolve some controversial issues in the literature, Comment: Latex2e, 8 pages, no figure

Dieser Beitrag schlagt einen neuartigen Ansatz zur optimierten Ausfuhrung von Java-Bytecode vor, der die dynamische Optimierung eines Java-Programms durch statische Programmanalyse vorbereitet. Die Analyseinformation wird unabhangig von der Programmausfuhrung bezogen auf alle Klassendateien einer Softwarebibliothek ermittelt und gespeichert. Zur Laufzeit unterstutzt die an den Bibliotheksschnittstellen komponierte Information insbesondere Optimierungen, die zusatzlich dynamische Programmeigenschaften ausnutzen.

A study of the center symmetric phase of SU(2) Yang Mills theory is presented. Realization of the center symmetry is shown to result from non-perturbative gauge fixing. Dictated by the center symmetry, this phase exhibits already at the perturbative level confinement like properties. The analysis is performed by investigating the dynamics of the Polyakov loops. The ultralocality of these degrees of freedom implies significant changes in the vacuum structure of the theory. General properties of the confined phase and of the transition to the deconfined phase are discussed. Perturbation theory built upon the vacuum of ultralocal Polyakov loops is presented and used to calculate, via the Polyakov loop correlator, the static quark-antiquark potential., 45 pages, LaTeX, 8 figures

A study of two-dimensional QCD on a spatial circle with Majorana fermions in the adjoint representation of the gauge groups SU(2) and SU(3) has been performed. The main emphasis is put on the symmetry properties related to the homotopically non-trivial gauge transformations and the discrete axial symmetry of this model. Within a gauge fixed canonical framework, the delicate interplay of topology on the one hand and Jacobians and boundary conditions arising in the course of resolving Gauss's law on the other hand is exhibited. As a result, a consistent description of the residual $Z_N$ gauge symmetry (for SU(N)) and the ``axial anomaly" emerges. For illustrative purposes, the vacuum of the model is determined analytically in the limit of a small circle. There, the Born-Oppenheimer approximation is justified and reduces the vacuum problem to simple quantum mechanics. The issue of fermion condensates is addressed and residual discrepancies with other approaches are pointed out., Comment: 44 pages; for hardcopies of figures, contact thies@theorie3.physik.uni-erlangen.de

Guided by a study of kink-antikink scattering in the Gross-Neveu model and other known solutions of the Hartree-Fock approach of a particularly simple type, we demonstrate a quantitative relationship between three different problems: Quantized 1+1-dimensional fermions in the large N limit, solitons of the classical sinh-Gordon equation and classical strings moving in 3-dimensional anti de Sitter space. Aside from throwing light on the relationship between quantum field theory and classical physics, this points to the full solvability of the dynamical N-kink-antikink problem in the Gross-Neveu model., Comment: 13 pages, 7 figures

The biodegradation of dialkyldimethylammonium compounds in aqueous solutions indicates that part of the degradation pathway includes the Cope elimination reaction, which does not occur under mild conditions in the absence of microorganisms.

We present calculations of quasi-elastic pion scattering on 16 O in both the Δ- hole model and a standard first-order theory. The basic approach is a modified “DWIA”, where the same in-medium πN t -operator is used for the transition and the optical potential generating the distorted pion wave functions. In order to allow a meaningful comparison with the recent SIN data, all technical complications such as background interactions, non-static vertex-corrections, 1/ A effects, are taken into account, and the DWIA amplitude is evaluated without further numerical simplification like, e.g., factorization. In contrast to the closure approximation, the Δ-hole model predicts correctly the doubly differential cross sections for (π, π') on 16 O over a wide range of angles and energy-losses.

We propose a general framework in which inclusive inelastic scattering of medium- or high-energy hadrons on nuclei can be discussed, without resorting either to the fixed scatterer approximation, or to a frankly classical description. A combination of Watson's multiple scattering theory and the Wigner representation—which had to be extended for this purpose—enables us to visualize the reaction in phase space as a series of inelastic two-body collisions, separated by propagations in an optical potential. The inclusive multiple scattering series can be summed up in principle by solving a one-body integral equation in phase space. This “cascade equation” is derived in a simple nuclear model, and shown to be equivalent to a transport equation for the Wigner density matrix of the projectile. Quantum-mechanical interference and wave effects can be treated systematically within this scheme. In the static, eikonal approximation, we recover the results of Glauber theory, and in the classical limit a particular form of the Boltzmann equation.

A coupled channel formalism is used to study the role of the Λ(1405) for kaonic 12 C in a non-static way. Medium corrections are calculated in a microscopic fashion, closely related to a Brueckner type of “independent pair approximation”. Nucleon and kaon binding effects (the latter in a rudimentary self-consistent way) and the Pauli blocking effect are examined and some of the widely used approximations (Fermi gas and local density, closure approximation) are put to trial. Fair agreement with experiment can be obtained without a free parameter, but it is shown to depend sensitively on the input elementary (sub-threshold) scattering amplitude.

In the present study lectin-binding sites were investigated for the lectins Ricinus communis agglutinin (RCA I), wheat germ agglutinin (WGA), soya bean agglutinin (SBA), concanavalin A (Con A), Lotus tetragonolobus-(LTA) and Limulus polyphemus agglutinin (LPA) during the initial stages of vasculogenesis of the CNS-anlage in 10 to 12-day-old NMRI mouse embryos. Specific binding sites for the lectins RCA I (sugar specificity: beta-D-galactose, N-acetylgalactosamine), WGA (sugar specificity: N-acetylglucosamine, sialic acid), and SBA (sugar specificity: N-acetylgalactosamine, beta-D-galactose) were detected in the newly formed capillaries within the neuroepithelial cell layer. In contrast, binding sites for Con A, LTA and LPA could not be observed at the start of the vascularization of the CNS-anlage. From these results, the conclusion can be drawn that glycoconjugates containing D-galactose, N-acetylgalactosamine and N-acetyl-glucosamine moieties are involved in the early vasculogenesis of the embryonic CNS-anlage of the mouse.

The nucleon-nucleon interaction becomes inelastic at ~ 300 MeV lab energy, signalling the onset of pi-meson production. Heavy ion collisions at energies of several 100 MeV per nncleon will therefore inevitably be accompanied by the appearance of pions. The issue of pion absorption in nuclei[l] is relevant for these processes in two ways: First, the pion production mechanism is closely related to that of the inverse reaction, pion absorption. Secondly, some of the produced pions will be re-absorbed by the nuclei involved, an effect which has to be accounted for when analyzing the data.

This paper describes a framework for the design space exploration of resource-efficient software-defined radio architectures. This design space exploration is based on a dual design flow, using a central processor specification as reference for the hardware development and the automatic generation of a C-compiler based tool chain. Using our modular rapid prototyping environment RAPTOR and the RF-frontend DB-SDR, functional verification of SDR applications can be performed. An 802.11b transmitter SDR implementation is mapped on our CoreVA a VLIW architecture and evaluated in terms of execution time and energy consumption. By introducing application specific instruction set extensions and a dedicated hardware accelerator, execution time and energy consumption could be reduced by about 90%.

We have developed an application-driven methodology for implementing parallel and heterogeneous programmable platforms. We deploy our flow for network access platforms where we have to trade off flexibility against costs and performance. Our methodology therefore focuses on characterizing the application domain as early as possible. With this input, we can narrow the design space to one major design trajectory that starts with the most flexible solution and refines the platform architecture systematically to meet performance and costs constraints. Our flow includes an efficient path to implementation in hardware and software. The software implementation framework takes a modular application description and generates code for embedded processors that can easily be ported to different platforms and used for profiling. Different communication architectures, co-processors, and specializations of programmable processing elements can be derived from profiling results to affect the platform hardware. A DSL Access Multiplexer (DSLAM) is used as an example throughout the paper to depict the different phases of our design process.

With more and more neuromorphic hardware systems for the accel- eration of spiking neural networks available in science and industry, there is a demand for platform comparison and performance esti- mation of such systems. This work describes selected benchmarks implemented in a framework with exactly this target: independent black-box benchmarking and comparison of platforms suitable for the simulation/emulation of spiking neural networks.

During a typical development process of an embedded application specific processor (ASIP), the architecture is implemented multiple times on different levels of abstractions. As a result of this redundant specification, certain inconsistencies may show up. For example, the implementation of an instruction in the simulator may differ from the HDL implementation. To detect such inconsistencies, we use register trace comparison. Our key contribution is a generic method for systematic trace synchronization. Therefore, we convert a micro-architectural trace into an architectural trace. This method considers pipeline hazards and non-uniform write latencies. To simplify the validation of a processor, we further have implemented an automatic validation environment that includes a tool which points the developer directly to erroneous instructions. The flow has been validated during the development of our CoreVA architecture for mobile applications.

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