5,977 research outputs found
Two- and three-point Green's functions in two-dimensional Landau-gauge Yang-Mills theory
The ghost and gluon propagator and the ghost-gluon and three-gluon vertex of
two-dimensional SU(2) Yang-Mills theory in (minimal) Landau gauge are studied
using lattice gauge theory. It is found that the results are qualitatively
similar to the ones in three and four dimensions. The propagators and the
Faddeev-Popov operator behave as expected from the Gribov-Zwanziger scenario.
In addition, finite volume effects affecting these Green's functions are
investigated systematically. The critical infrared exponents of the
propagators, as proposed in calculations using stochastic quantization and
Dyson-Schwinger equations, are confirmed quantitatively. For this purpose
lattices of volume up to (42.7 fm)^2 have been used.Comment: 14 pages, 14 figures, 4 tables, references adde
Describing gluons at zero and finite temperature
Any description of gluons requires a well-defined gauge. This is complicated
non-perturbatively by Gribov copies. A possible method-independent gauge
definition to resolve this problem is presented and afterwards used to study
the properties of gluons at any temperature. It is found that only
chromo-electric properties reflect the phase transition. From these the
gauge-invariant phase transition temperature is determined for SU(2) and SU(3)
Yang-Mills theory independently.Comment: 3 pages, 1 figure. Talk given at "The 5-th International Conference
on Quarks and Nuclear Physics", Beijing, China, and at "Quarks, Hadrons, and
the Phase Diagram of QCD", St. Goar, Germany, both September 2009. Submitted
to the QNP proceeding
Bound-state/elementary-particle duality in the Higgs sector and the case for an excited 'Higgs' within the standard model
Though being weakly interacting, QED can support bound states. In principle,
this can be expected for the weak interactions in the Higgs sector as well. In
fact, it has been argued long ago that there should be a duality between bound
states and the elementary particles in this sector, at least in leading order
in an expansion in the Higgs condensate. Whether this remains true beyond the
leading order is investigated using lattice simulations, and support is found.
This provides a natural interpretation of peaks in cross sections as bound
states. Unambiguously, this would imply the existence of (possibly very broad)
resonances of Higgs and W and Z bound states within the standard model.Comment: 15 pages, 3 figures v2: added appendix with technical details, some
minor improvement
A luminosity monitor for the A4 parity violation experiment at MAMI
A water Cherenkov luminosity monitor system with associated electronics has
been developed for the A4 parity violation experiment at MAMI. The detector
system measures the luminosity of the hydrogen target hit by the MAMI electron
beam and monitors the stability of the liquid hydrogen target. Both is required
for the precise study of the count rate asymmetries in the scattering of
longitudinally polarized electrons on unpolarized protons. Any helicity
correlated fluctuation of the target density leads to false asymmetries. The
performance of the luminosity monitor, investigated in about 2000 hours with
electron beam, and the results of its application in the A4 experiment are
presented.Comment: 22 pages, 12 figures, submitted to NIM
Efficiently connecting textual and visual information in operating instructions
Most technical documents rely on a combination of text and visuals to communicate their messages. To achieve the desired effect of improved processing and comprehension of operating instructions, the text must guide readers in a clear way to the relevant visual information in order to avoid ambiguity and misinterpretation, and to ensure that the reader optimally benefits from the available informatio
Keplerian discs around post-AGB stars: a common phenomenon?
Aims: We aim at showing that the broad-band SED characteristics of our sample
of post-AGB stars are best interpreted, assuming the circumstellar dust is
stored in Keplerian rotating passive discs.
Methods: We present a homogeneous and systematic study of the Spectral Energy
Distributions (SEDs) of a sample of 51 post-AGB objects. The selection criteria
to define the whole sample were tuned to cover the broad-band characteristics
of known binary post-AGB stars. The whole sample includes 20 dusty RV Tauri
stars from the General Catalogue of Variable Stars (GCVS). We supplemented our
own Geneva optical photometry with literature data to cover a broad range of
fluxes from the UV to the far-IR.
Results: All the SEDs display very similar characteristics: a large IR excess
with a dust excess starting near the sublimation temperature, irrespective of
the effective temperature of the central star. Moreover, when available, the
long wavelength fluxes show a black-body slope indicative of the presence of a
component of large mm sized grains.
Conclusions: We argue that in all systems, gravitationally bound dusty discs
are present. The discs must be puffed-up to cover a large opening angle for the
central star and we argue that the discs have some similarity with the passive
discs detected around young stellar objects. We interpret the presence of a
disc to be a signature for binarity of the central object, but this will need
confirmation by long-term monitoring of the radial velocities. We argue that
dusty RV Tauri stars are those binaries which happen to be in the Population II
instability strip.Comment: 29 pages, 5 figures, accepted for publication in A&
The Effects of Drying and Wetting on the Soil Chemical Properties of Acid Sulphate Soils of Kalimantan
This research aimed to study the effects of land reclamation (drying, wetting, flushing, and leaching) on the change of soil chemical properties of acid sulphate soils from Kalimantan. Randomized Complete Design (RCD) by two factors treatments with two replications is used in this research. Factor I was soil reactiveness that is define as (a) low reactive= R1; (b)moderate reactive =R2; (c) strong reactive= R3, and (d) very strong reactive= R4 respectively. Factor II was drying, wetting, and diluting that is define as (1) drying continuously after wetting = W1, (2) wetting continuously = W2; (3) drying after weeting and diluting =W3; and (4) wetting and diluting. The result of experiments show that continuous drying after wetting (W1) and drying after wetting and diluting (W3) or continuous weeting (W2) gave soils pH lower than the weeting and diluting (W4).Dried on the strong reactive soils (R4) not decrease soil pH significantly. The continouos drying after wetting (W1) can increase EC (electrical conductivity) higher than the continous wetting (W2) and wetting that followed diluting (W4) or drying after wetting and diluting (W3). The continouos wetting (W2) and the continouos drying after wetting (W1) has given the total soluble acidity of 63,30 dan 61,71 cmolc kg-1 respectively, higher than drying after wetting and diluting (W3) and wetting thatfollowed diluting (W4) that given total soluble acidity of 54,03 and 51,95 cmolc kg-1 respectively. The effects of drying, wetting, flushing, and leaching on the total soluble acidity, Soluble Al and soluble H, especially on the strong reactive soils are very significant. All of the exchangeble bases (Ca, Mg, K, Na) on the continouos drying after wetting (W1) are lower than the continous wetting (W2) and wetting that followed diluting (W4)or drying after wetting and diluting (W3) respectively. The continouos drying after wetting (W1), the continous wetting (W2) and wetting that follow diluting (W4) or drying after wetting and diluting (W3) decrease exchangable Mg, especially on strong reactive soils (R4), but contradictive to low reactive soils (R1). The continouos drying after wetting (W1) increase exchangable Na, especially on low reactive soils (R1), but the wetting that followed diluting (W3, W4) decreases exchangable Na
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