Impurity-induced smearing of the spin resonance peak in Fe-based superconductors

The spin resonance peak in the iron-based superconductors is observed in inelastic neutron scattering experiments and agrees well with predicted results for the extended s-wave ($s_\pm$) gap symmetry. On the basis of four-band and three-orbital tight binding models we study the effect of nonmagnetic disorder on the resonance peak. Spin susceptibility is calculated in the random phase approximation with the renormalization of the quasiparticle self-energy due to the impurity scattering in the static Born approximation. We find that the spin resonance becomes broader with the increase of disorder and its energy shifts to higher frequencies. For the same amount of disorder the spin response in the $s_\pm$ state is still distinct from that of the $s_{++}$ state.Comment: 4 pages, 2 figure

Measurement of tensor analyzing powers in deuteron photodisintegration

New accurate measurement of tensor analyzing powers T20, T21 and T22 in deuteron photodisintegration has been performed. Wide-aperture non-magnetic detectors allowed to cover broad kinematic ranges in a single setup: photon energy = 25 to 600 MeV, proton emission angle in CM = 24 to 48 deg. and 70 to 102 deg. New data provide a significant improvement of a few existing measurements. The angular dependency of the tensor asymmetries in deuteron photodisintegration is extracted for the first time.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let

Explication of the Methodological Difficulties of Modern Axiology

The authors focus on the group of methodological difficulties of axiology, due to its specific multifaceted subject. One of the major difficulties in the study of values is that there is no unity in the understanding of the essence of value in science. Axiological theories that exist within different philosophical and cultural philosophy of teachings represent a diversity of opinions, conclusions, decisions and methodological approaches. There are several different approaches of consideration of the category of "value", covering different spheres of social life in axiology, in values the elements of the sub-categories and subcategories are distinguished. Methodological pluralism in interpretation and typology of values are analyzing. Theoretical foundations of axiology are formed as a response to two major challenges: existential status of values and their relationship to the facts of reality. The response to these challenges in axiology was pluralization of ways of philosophizing, which is expressed in the generation of a variety of axiologically oriented traditions, based on its own research methodology and leading to the existence of a number of methodological inconsistencies. According to the results of the analysis, the authors concluded that the difficulties of methodological nature, reflecting the diversity of its subject matter, are manifested in the increasing expansion of the research field of axiology, in the unresolved range of the fundamental problems in the axiology in the existing diversity of theories, values and definitions of the concept of "value" itself and etc., this methodological situation requires a rethinking of the methodology and axiology. DOI: 10.5901/mjss.2015.v6n3s1p47

Backward asymmetry of the Compton scattering by an isotropic distribution of relativistic electrons: astrophysical implications

The angular distribution of low-frequency radiation after single scattering by an isotropic distribution of relativistic electrons considerably differs from the Rayleigh angular function. In particular, the scattering by an ensemble of ultra-relativistic electrons obeys the law p=1-cos(alpha), where alpha is the scattering angle; hence photons are preferentially scattered backwards. We discuss some consequences of this fact for astrophysical problems. We show that a hot electron-scattering atmosphere is more reflective than a cold one: the fraction of incident photons which become reflected having suffered a single scattering event can be larger by up to 50 per cent in the former case. This should affect the photon exchange between cold accretion disks and hot coronae or ADAF flows in the vicinity of relativistic compact objects; as well as the rate of cooling (through multiple inverse-Compton scattering of seed photons supplied from outside) of optically thick clouds of relativistic electrons in compact radiosources. The forward-backward scattering asymmetry also causes spatial diffusion of photons to proceed slower in hot plasma than in cold one, which is important for the shapes of Comptonization spectra and the time delays between soft and hard radiations coming from variable X-ray sources.Comment: 20 pages, 3 figures, to appear in Astronomy Letters, added reference

When logic meets engineering: introduction to logical issues in the history and philosophy of computer science

Introduction to a Journal Special issue on Logical Issues in the History and Philosophy of Computer Scienc