American Physical Society

About: American Physical Society is a nonprofit organization based out in College Park, Maryland, United States. It is known for research contribution in the topics: Quantum chromodynamics & Quark. The organization has 107 authors who have published 391 publications receiving 14126 citations. The organization is also known as: APS.

Infrared and ultraviolet properties of the Landau gauge quark propagator

Abstract: We present a current summary of a program to study the quark propagator using lattice QCD. We use the Overlap and ``Asqtad'' quark actions on a number of lattice ensembles to assess systematic errors. We comment on the place of this work amongst studies of QCD Green's functions in other formulations. A preliminary calculation of the running quark mass is presented.

Signature of a polyamorphic transition in the THz spectrum of vitreous GeO2

Abstract: The THz spectrum of density fluctuations, $S(Q, \omega)$, of vitreous GeO$_2$ at ambient temperature was measured by inelastic x-ray scattering from ambient pressure up to pressures well beyond that of the known $\alpha$-quartz to rutile polyamorphic (PA) transition. We observe significant differences in the spectral shape measured below and above the PA transition, in particular, in the 30-80 meV range. Guided by first-principle lattice dynamics calculations, we interpret the changes in the phonon dispersion as the evolution from a quartz-like to a rutile-like coordination. Notably, such a crossover is accompanied by a cusp-like behavior in the pressure dependence of the elastic response of the system. Overall, the presented results highlight the complex fingerprint of PA phenomena on the high-frequency phonon dispersion.

Finite-volume scaling of the quenched chiral condensate

Abstract: In the large-volume limit V → ∞ with V ⪡ 1mπ4 the mass-dependent chiral condensate is predicted to satisfy exact finite-volume scaling laws that fall into three major universality classes. We test these analytical predictions with staggered fermions and overlap fermions in gauge field sectors of fixed topological charge ν.

Kaon semileptonic decays with $N_f=2+1+1$ HISQ fermions and physical light-quark masses

Abstract: We discuss the reduction of errors in the calculation of the form factor $$f_+^{K \pi}(0)$$ with HISQ fermions on the $$N_f=2+1+1$$ MILC configurations from increased statistics on some key ensembles, new data on ensembles with lattice spacings down to 0.042 fm and the study of finite-volume effects within staggered ChPT. We also study the implications for the unitarity of the CKM matrix in the first row and for current tensions with leptonic determinations of $$\vert V_{us}\vert$$.

Sunyaev-Zel'dovich effect or not ? detecting the main foreground effect of most galaxy clusters.

Abstract: Galaxy clusters are the most massive objects in the Universe and comprise a high-temperature intracluster medium of about 10 7 K, believed to offer a main foreground effect for cosmic microwave background (CMB) data in the form of the thermal Sunyaev–Zel’dovich (SZ) effect. This assumption has been confirmed by SZ signal detection in hundreds of clusters but, in comparison with the huge numbers of clusters within optically selected samples from Sloan Digital Sky Survey (SDSS) data, this only accounts for a few per cent of clusters. Here we introduce a model-independent new method to confirm the assumption that most galaxy clusters can offer the thermal SZ signal as their main foreground effect. For the Wilkinson Microwave Anisotropy Probe (WMAP) seven-year data (and a given galaxy cluster sample), we introduced a parameter d1 as the nearest-neighbour cluster angular distance of each pixel, then we classified data pixels as ‘to be’ (d1 → 0 case) or ‘not to be’ (d1 large enough) affected by the sample clusters. By comparing the statistical results of these two kinds of pixels, we can see how the sample clusters affect the CMB data directly. We find that the Planck Early Sunyaev–Zel’dovich (ESZ) sample and X-ray samples (∼10 2 clusters) can lead to obvious temperature depression in theWMAP seven-year data, which confirms the SZ effect prediction. However, each optically selected sample (>10 4 clusters) shows an opposite result: the mean temperature rises to about 10 µK. This unexpected qualitative scenario implies that the main foreground effect of most clusters is not always the expected SZ effect. This may be the reason why the SZ signal detection result is lower than expected from the model.