43394178
Algorithmic derivation of Dyson-Schwinger equations
Abstract We present an algorithm for the derivation of Dyson–Schwinger equations of general theories that is suitable for an implementation within a symbolic programming language. Moreover, we introduce the Mathematica package DoDSE 1 which provides such an implementation. It derives the Dyson–Schwinger equations graphically once the interactions of the theory are specified. A few examples for the application of both the algorithm and the DoDSE package are provided. Program summary Program title: DoDSE Catalogue identifier: AECT_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AECT_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 105 874 No. of bytes in distributed program, including test data, etc.: 262 446 Distribution format: tar.gz Programming language: Mathematica 6 and higher Computer: all on which Mathematica is available Operating system: all on which Mathematica is available Classification: 11.1, 11.4, 11.5, 11.6 Nature of problem: Derivation of Dyson–Schwinger equations for a theory with given interactions. Solution method: Implementation of an algorithm for the derivation of Dyson–Schwinger equations. Unusual features: The results can be plotted as Feynman diagrams in Mathematica. Running time: Less than a second to minutes for Dyson–Schwinger equations of higher vertex functions.
119208185
Going beyond the propagators of Landau gauge Yang-Mills theory
We present results for the propagators and the ghost-gluon vertex of Landau gauge Yang-Mills theory obtained from Dyson-Schwinger equations. Solving these three quantities simultaneously constitutes a new step in truncating these equations. We also introduce a new model for the three-gluon vertex that is motivated by lattice results. It features a zero crossing which is confirmed a posteriori by a Dyson-Schwinger calculation. Within our setup we can reproduce lattice data very well. We establish that also for the ghost-gluon vertex a difference between decoupling and scaling solutions is present. For the scaling solution we discuss the possibility of modifying the infrared exponents via an angle dependence of the ghost-gluon vertex. However, no such dependence is found in our calculations. Finally, we calculate the Schwinger function for the gluon propagator.
118463320
Infrared analysis of Dyson-Schwinger equations taking into account the Gribov horizon in Landau gauge
The low momentum behavior of the Landau gauge Gribov-Zwanziger action is investigated using the respective Dyson-Schwinger equations. Because of the mixing of the gluon and the auxiliary fields four scenarios can be distinguished for the infrared behavior. Two of them lead to inconsistencies and can be discarded. Another one corresponds to the case where the auxiliary fields behave exactly like the Faddeev-Popov ghosts and the same scaling relation as in standard Landau gauge, {kappa}{sub A}+2{kappa}{sub c}=0, is valid. Even the parameter {kappa} is found to be the same, 0.595. The mixed propagators, which appear, are suppressed in all loops, and their anomalous infrared exponent can also be determined. A fourth case provides an even stricter scaling relation that includes also the mixed propagators, but possesses the same qualitative feature, i.e. the propagators of the Faddeev-Popov ghost and the auxiliary fields are infrared enhanced and the mixed and the gluon propagators are infrared suppressed. In this case the system of equations to obtain the parameter {kappa} is nonlinear in all variables.
86866691
Spurious divergences in Dyson-Schwinger equations
A bstractWe revisit the treatment of spurious ultraviolet divergences in the equation of motion of the gluon propagator caused by a momentum cutoff and the resulting violation of gauge invariance. With present continuum studies of the gluon propagator from its Dyson-Schwinger equation reaching the level of quantitatively accurate descriptions, it becomes increasingly important to understand how to subtract these spurious divergences in an unambiguous way. Here we propose such a method. It is based entirely on the asymptotic perturbative behavior of the QCD Green’s functions without affecting non-perturbative aspects such as mass terms or the asymptotic infrared behavior. As a particular example, this allows us to assess the possible influence of the tadpole diagram beyond perturbation theory. Finally, we test this method numerically by solving the system of Dyson-Schwinger equations of the gluon and ghost propagators.
118375544
On the influence of three-point functions on the propagators of Landau gauge Yang-Mills theory
A bstractWe solve the Dyson-Schwinger equations of the ghost and gluon propagators of Landau gauge Yang-Mills theory together with that of the ghost-gluon vertex. The latter plays a central role in many truncation schemes for functional equations. By including it dynamically we can determine its influence on the propagators. We also suggest a new model for the three-gluon vertex motivated by lattice data which plays a crucial role to obtain stable solutions when the ghost-gluon vertex is included. We find that both vertices have a sizable quantitative impact on the mid-momentum regime and contribute to the reduction of the gap between lattice and Dyson-Schwinger equation results. Furthermore, we establish that the three-gluon vertex dressing turns negative at low momenta as suggested by lattice results in three dimensions.
15541387
Lower dimensional Yang-Mills theory as a laboratory to study the infrared regime
Lattice studies of the infrared regime of gauge theories are complicated by the required extensive limits, the performed gauge fixing and the demand for high statistics. Using a general power counting scheme for the infrared limit of Landau gauge SU(N) Yang-Mills theory in arbitrary dimensions we show that the infrared behavior of Greens functions is both qualitatively and quantitatively similar in two, three and four spacetime dimensions. Therefore, lower dimensional lattice simulations can serve as a simplified laboratory to analyze the presently applied approximations and to obtain first results for higher correlation functions.
121918725
Meson-nucleus interaction - on the use of intensive meson beams for subnuclear research -
Abstract The use of intensive pion and kaon beams for subnuclear research is discussed. The goals of such investigations are briefly sketched and illustrated for some typical examples of specific flavour transfer reactions. It turns out that the meson beams which will be available at the proposed EHF will open up a new aera of subnuclear research. Such investigation touch upon quite fundamental questions of hadronic physics.
119739868
Limits on WIMP–nucleon interactions from the Cryogenic Dark Matter Search at the Soudan Underground Laboratory
Abstract We present the results of the first two data runs of the Cryogenic Dark Matter Search at Soudan Underground Laboratory. These data exclude substantial new parameter space for both spin-independent and spin-dependent WIMP–nucleon interactions within the standard halo model.
123329950
Exclusion Limits on the WIMP Nucleon Cross-Section from the Cryogenic Dark Matter Search
The Cryogenic Dark Matter Search (CDMS) employs low-temperature Ge and Si detectors to search for weakly interacting massive particles (WIMPs) via their elastic-scattering interactions with nuclei while discriminating against interactions of background particles. For recoil energies above 10 keV, events due to background photons are rejected with >99.9% efficiency, and surface events are rejected with >95% efficiency. The estimate of the background due to neutrons is based primarily on the observation of multiple-scatter events that should all be neutrons. Data selection is determined primarily by examining calibration data and vetoed events. Resulting efficiencies should be accurate to ∼10%. Results of CDMS data from 1998 and 1999 with a relaxed fiducial-volume cut (resulting in 15.8 kg days exposure on Ge) are consistent with an earlier analysis with a more restrictive fiducial-volume cut. Twenty-three WIMP candidate events are observed, but these events are consistent with a background from neutrons in all ways tested. Resulting limits on the spin-independent WIMP-nucleon elastic-scattering cross section exclude unexplored parameter space for WIMPs with masses between 10–70 GeV/c2. These limits border, but do not exclude, parameter space allowed by supersymmetry models and accelerator constraints. Results are compatible with some regions reported as allowed at 3σ by the annual-modulation measurement of the DAMA Collaboration. However, under the assumptions of standard WIMP interactions and a standard halo, the results are incompatible with the DAMA most likely value at >99.9% confidence level (C.L.), and are incompatible with the model-independent annual-modulation signal of DAMA at 99.99% C.L. in the asymptotic limit.
88507576
PS1-10bzj: A fast, hydrogen-poor superluminous supernova in a metal-poor host galaxy
We present observations and analysis of PS1-10bzj, a superluminous supernova (SLSN) discovered in the Pan-STARRS Medium Deep Survey at a redshift z = 0.650. Spectroscopically, PS1-10bzj is similar to the hydrogen-poor SLSNe 2005ap and SCP 06F6, though with a steeper rise and lower peak luminosity (M bol –21.4 mag) than previous events. We construct a bolometric light curve, and show that while PS1-10bzj's energetics were less extreme than previous events, its luminosity still cannot be explained by radioactive nickel decay alone. We explore both a magnetar spin-down and circumstellar interaction scenario and find that either can fit the data. PS1-10bzj is located in the Extended Chandra Deep Field South and the host galaxy is imaged in a number of surveys, including with the Hubble Space Telescope. The host is a compact dwarf galaxy (MB –18 mag, diameter 800 pc), with a low stellar mass (M * 2.4 × 107 M ☉), young stellar population (τ* 5 Myr), and a star formation rate of ~2-3 M ☉ yr–1. The specific star formation rate is the highest seen in an SLSN host so far (~100 Gyr–1). We detect the [O III] λ4363 line, and find a low metallicity: 12 + (O/H) = 7.8 ± 0.2 ( 0.1 Z ☉). Together, this indicates that at least some of the progenitors of SLSNe come from young, low-metallicity populations.
122196168
Analysis of the (p, π+) reaction at a momentum transfer below 600 MeV/c☆
Abstract The nuclear production of positive pions in proton-induced reactions on light nuclei is calculated in a Two-Nucleon-Model including π and ϱ single rescattering terms. As a main feature of this model the strong sensitivity of the predictions on the initial and final state interactions observed in the One-Nucleon-Model is considerably reduced. The results reproduce satisfactorily the characteristic trends in the experimental data.