A Circulating Hydrogen Ultra-High Purification System for the MuCap Experiment

The MuCap experiment is a high-precision measurement of the rate for the basic electroweak process of muon capture, mu- + p -> n + nu . The experimental approach is based on an active target consisting of a time projection chamber (TPC) operating with pure hydrogen gas. The hydrogen has to be kept extremely pure and at a stable pressure. A Circulating Hydrogen Ultrahigh Purification System was designed at the Petersburg Nuclear Physics Institute (PNPI) to continuously clean the hydrogen from impurities. The system is based on an adsorption cryopump to stimulate the hydrogen flow and on a cold adsorbent for the hydrogen cleaning. It was installed at the Paul Scherrer Institute (PSI) in 2004 and performed reliably during three experiment runs. During several months long operating periods the system maintained the hydrogen purity in the detector on the level of 20 ppb for moisture, which is the main contaminant, and of better than 7 ppb and 5 ppb for nitrogen and oxygen, respectively. The pressure inside the TPC was stabilized to within 0.024% of 10 bar at a hydrogen flow rate of 3 standard liters per minute.Comment: submitted to Nucl. Instr. Methods Phys. Res.

New polarimetric constraints on axion-like particles

We show that the parameter space of axion-like particles can be severly constrained using high-precision measurements of quasar polarisations. Robust limits are derived from the measured bounds on optical circular polarisation and from the distribution of linear polarisations of quasars. As an outlook, this technique can be improved by the observation of objects located behind clusters of galaxies, using upcoming space-borne X-ray polarimeters.Comment: Submitted to JCA

Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

On complex-valued 2D eikonals. Part four: continuation past a caustic

Theories of monochromatic high-frequency electromagnetic fields have been designed by Felsen, Kravtsov, Ludwig and others with a view to portraying features that are ignored by geometrical optics. These theories have recourse to eikonals that encode information on both phase and amplitude -- in other words, are complex-valued. The following mathematical principle is ultimately behind the scenes: any geometric optical eikonal, which conventional rays engender in some light region, can be consistently continued in the shadow region beyond the relevant caustic, provided an alternative eikonal, endowed with a non-zero imaginary part, comes on stage. In the present paper we explore such a principle in dimension $2.$ We investigate a partial differential system that governs the real and the imaginary parts of complex-valued two-dimensional eikonals, and an initial value problem germane to it. In physical terms, the problem in hand amounts to detecting waves that rise beside, but on the dark side of, a given caustic. In mathematical terms, such a problem shows two main peculiarities: on the one hand, degeneracy near the initial curve; on the other hand, ill-posedness in the sense of Hadamard. We benefit from using a number of technical devices: hodograph transforms, artificial viscosity, and a suitable discretization. Approximate differentiation and a parody of the quasi-reversibility method are also involved. We offer an algorithm that restrains instability and produces effective approximate solutions.Comment: 48 pages, 15 figure

The Psychological Content of Relationship between Sense and Meaning in Cultural-Historical Approach

The paper considers L.S. Vygotsky’s cultural-historical theory and its interpretation in modern psychology. It shows that psychological content of many concepts introduced by L.S. Vygotsky differs greatly from that of the ones used in theory and practice of modern psychological science. The authors state that L.S. Vygotsky’s main idea which shapes the specifics of cultural-historical psychology is the idea of sense primacy in relation to meaning. The analysis of subject content of the concept of «cultural development» allows us to affirm that L.S. Vygotsky understood the essence of learning process somewhat differently from what is now accepted. Learning in cultural-historical psychology promotes the development of will and self-regulation. Meanwhile, learning is seen not as a transformation of the external into the internal (process of interiorization), but as the ability to realize oneself in the outer world. At the same time, an important role in mental development and learning is played by another mental function, imagination

Imagination and Creativity: Cultural–Historical Approach

Consideration of the concept of imagination in the context of cultural-historical psychology led to the conclusion that there are two differently directed processes. One process involves making sense of things in the outside world and the present situation, that is, it means understanding and rethinking external objects and situations. Another process involves the construction of a new image that allows you to see and understand the surrounding reality in a new way. This allows the authors to say that, on the one hand, imagination is aimed at acting with external reality, and, on the other hand, the inner work of creating a new subject of imagination. Based on the analysis of empirical materials studying the development of imagination and creativity, the authors obtained experimental proof of the idea of L.S. Vygotsky that images of imagination are realized in creativity and come to the conclusion about the possibility of purposeful development of creativity in ontogenesis. Authors connect the purposeful development of creativity with theatrical pedagogy, in which training and education are realized with the help of theatrical methods. Theatrical methods, according to the authors, are methods by which you can set an imaginary situation and, at the same time, these are methods that allow the viewer to be included in theatrical action

From Joint Activity to the Construction of New SocialCommunities: Jointness. Creativity. Education. School (Roundtable of the methodological seminar supervisedby V.V. Rubtsov and B.D. Elkonin)

On July 10, 2018 a discussion seminar “From Joint Activity to the Construction of New Social Communities: Jointness. Creativity. Education. School” was held at the Moscow State University of Psychology and Education dedicated to the 70th birthday of professor Vitaly Rubtsov, Rector of MSUPE. Some of the discussed topics were: “Sociogenesis and the productive nature of joint action”, “From co-operation to co-creation: new forms of community in joint activity”, “Jointness in play, learning and design activity”, “School as the place for developing various forms of child-adult communities and activities”. Among the participants of the seminar were representatives of the leading research and educational organizations: Moscow State University of Psychology and Education, National Research University Higher School of Economics, Psychological Institute of the Russian Academy of Education, Institute of Philosophy of the Russian Academy of Sciences, and others. Here we present the full text of the discussion