Quantitative sum rule analysis of low-temperature spectral functions

We analyze QCD and Weinberg-type sum rules in a low-temperature pion gas using vector and axial-vector spectral functions following from the model-independent chiral-mixing scheme. Toward this end we employ recently constructed vacuum spectral functions with ground and first-excited states in both channels and a universal perturbative continuum; they quantitatively describe hadronic tau-decay data and satisfy vacuum sum rules. These features facilitate the implementation of chiral mixing without further assumptions, and lead to in-medium spectral functions which exhibit a mutual tendency of compensating resonance and dip structures, suggestive for an approach toward structureless distributions. In the sum rule analysis, we account for pion mass corrections, which turn out to be significant. While the Weinberg sum rules remain satisfied even at high temperatures, the numerical evaluation of the QCD sum rules for vector and axial-vector channels reveals significant deviations setting in for temperatures beyond ~140 MeV, suggestive of additional physics beyond low-energy chiral pion dynamics.Comment: 8 pages, 3 figure

SCR Blocking Pulse Gate Amplifier-Patent

Silicon controlled rectifier pulse gate amplifier for blocking false gating caused by negative transient voltage

Enhancing the cosmic-ray mass sensitivity of air-shower arrays by combining radio and muon detectors

The muonic and electromagnetic components of air showers are sensitive to the mass of the primary cosmic particle. The sizes of the components can be measured with particle detectors on ground, and the electromagnetic component in addition indirectly via its radio emission in the atmosphere. The electromagnetic particles do not reach the ground for very inclined showers. On the contrary, the atmosphere is transparent for the radio emission and its footprint on ground increases with the zenith angle. Therefore, the radio technique offers a reliable detection over the full range of zenith angles, and in particular for inclined showers. In this work, the mass sensitivity of a combination of the radio emission with the muons is investigated in a case study for the site of the Pierre Auger Observatory using CORSIKA Monte Carlo simulations of showers in the EeV energy range. It is shown, that the radio-muon combination features superior mass separation power in particular for inclined showers, when compared to established mass observables such as a combination of muons and electrons or the shower maximum Xmax. Accurate measurements of the energy-dependent mass composition of ultra-high energy cosmic rays are essential to understand their still unknown origin. Thus, the combination of muon and radio detectors can enhance the scientific performance of future air-shower arrays and offers a promising upgrade option for existing arrays

Semiotics and design: Towards an aesthetics of the artificial

Semiotics is the theory par excellence of the artificial and therefore should have a substantial role in understanding designed phenomena. By tracing the relation between design and semiotics at the level of the distinction between the analytic and the synthetic (or artificial), this paper argues that semiotics struggles to explain the environmental element of design so central to post-artefactual accounts of design. The analytic method of semiology is suitable for understanding existent semiotic structures but less so at modeling alternate signifying systems—or systems that alter, transform and self-interpret, that is, environments. The paper argues that to understand such milieus a turn to the aesthetic is necessary. By aesthetics it is meant the simultaneous mapping of the environment, the articulation of the environment and the counterfactual element of any design process. More particularly the paper will focus on recent developments within social semiotics to argue that such a framework must move beyond the constraints of analytical spatial and visual grammar to take into account not only multimodal texts but planning, systems and services. It will conclude by arguing that ultimately design and aesthetics are the same phenomenon, not in the sense that design is the study and application of aesthetic principles to useful objects or experiences, but in the sense that it is the organization of the counterfactual elements of artificial—designed—environments

Groups and semigroups with a one-counter word problem

We prove that a finitely generated semigroup whose word problem is a one-counter language has a linear growth function. This provides us with a very strong restriction on the structure of such a semigroup, which, in particular, yields an elementary proof of a result of Herbst, that a group with a one-counter word problem is virtually cyclic. We prove also that the word problem of a group is an intersection of finitely many one-counter languages if and only if the group is virtually abelian

Nucleon spin structure at very high-x

Dyson-Schwinger equation treatments of the strong interaction show that the presence and importance of nonpointlike diquark correlations within the nucleon are a natural consequence of dynamical chiral symmetry breaking. Using this foundation, we deduce a collection of simple formulae, expressed in terms of diquark appearance and mixing probabilities, from which one may compute ratios of longitudinal-spin-dependent u- and d-quark parton distribution functions on the domain x =1. A comparison with predictions from other approaches plus a consideration of extant and planned experiments shows that the measurement of nucleon longitudinal spin asymmetries on x =1 can add considerably to our capacity for discriminating between contemporary pictures of nucleon structure.Comment: 6 pages, 1 table, 3 figures. To appear in Phys. Lett.