Radiattonal capture of neutrons by deuterons n + d →3H + λ and P-odd nuclear forces

P-odd polarizational phenomena are considered in the radiative capture of neutrons by deuterons: n + d ³H + . It is shown that, in the general case, 18 different P-odd asymmetries of the angular distribution of quanta arise in the collision of arbitrarily polarized neutrons with a deuteron target characterized by vector and tensor polarizations. The P-odd contribution to the density matrix of the quanta formed in the capture of polarized neutrons by unpolarized deuterons is determined by eight real structural functions, while the P-odd dependence of the Stokes parameters of the photons on the tensor polarization of the deuterons is characterized, in the general case, by ten structural functions. In slow-neutron capture, the number of P-odd correlations is reduced.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 23–26, March, 1987.     

Estimating gas temperature in the channel of a high-temperature jet discharge in air

Consideration is made of determining gas temperature in the channel of a high-frequency jet discharge in air over the intensity distribution of lines for the rotational spectrum band for the transition A² X²II (0-0) in the radiation of hydroxyl. It is shown that the branches R₂ and Q₁ of this band are the most useful for temperature measurements at atmospheric pressure. Within error limits, the temperature in the discharge channel as determined from the lines of the R₂-branch is T_gas = (3120 ± 70) and (3380 ± 90) K in the cross sections of the discharge at a distance of 3 and 30 mm, respectively.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 3–7, February, 1987.     

Selecting the duration of excitation pulses for an electroluminescent thin-film matrix

The factors influencing the optimum selection of the excitation pulse width of thin-film electroluminescent devices is examined. It is shown that to excite an individual cell, a pulse width of 5–7 sec is sufficient, but to excite the matrix, the pulse width is determined by the independence of the conducting layer and the dimensions of the matrix. Formulas are cited for engineering calculations of the required pulse width.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 59–62, December, 1987.     

Self-activated luminescence of zinc sulfide

The nature of the luminescence of zinc sulfide in the spectral range (360), 380–420 nm (SAL) at 80K is analyzed. It is shown that the appearance of SAL radiation is accompanied by additional absorption in the region (350) 365–370 nm at 80K. The low-temperature spectra of sphalerite, exposed to different radiation and subjected to different treatment, are studied. The multiband luminescence of the isoelectronic sulfur impurity in ZnO deposits in the region 383–640 nm is discussed. It is concluded that SAL luminescence is attributable to the localization of excitons in ZnS on clusters, whose formation precedes the precipitation of the ZnO·S phase. The formation of oxygen clusters and deposits on dislocations in ZnS is studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 60–66, February, 1987.     

Wirkungsgrade in der Welt des Lebens und der Technik

Zusammenfassung Um der oft gehörten Meinung entgegenzutreten, die energetischen Wirkungsgrade lebender Organismen seien wesentlich höher als die technischer Verfahren, werden entsprechende Werte miteinander verglichen. Der sehr niedrige Wirkungsgrad der Photosynthese zusammen mit der kleinen Energiedichte der Sonnenstrahlung erzwang ab einer kritischen Größe die Aufspaltung in Energiesammler, die Pflanzen, und Verbraucher chemischer Energie, den Tieren. Dank den 10 mal höheren Wirkungsgraden in der Technik, lassen sich Solarmobile bauen, die von der auf sie fallenden Sonnenstrahlung angetrieben werden. Wegen des Multiplikationsgesetzes der Teilwirkungsgrade ergeben sich sowohl für die Speicherung der Sonnenenergie in den fossilen Brennstoffen wie in der Nahrungskette extrem niedrige Wirkungsgrade.

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Efficiencies in the world of life and in engineering

One often hears the opinion, that the efficiencies in the world of life are higher than in engineering. To disprove this, many values of efficiency of corresponding processes are compared. The very low efficiency of photosynthesis in living plants together with the low density of solar radiation has led the world of life to split into collectors of energy, the plants, and consumers of chemical energy, the animals. Thanks to the ten times higher efficiencies of solar cells, it is possible, to produce solar mobiles, vehicles that move driven by solar radiation.

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Herrn Prof. Dr.-Ing. U. Grigull zum 75. Geburtstag gewidmet     

Asymptotic expansions for dynamic programming recursions with general nonnegative matrices

This paper is concerned with the study of the asymptotic behavior of dynamic programming recursions of the form $$x(n + 1) = \mathop {\max }\limits_{P \in \mathcal{K}} Px(n), n = 0,1,2,...,$$ where ? denotes a set of matrices, generated by all possible interchanges of corresponding rows, taken from a fixed finite set of nonnegative square matrices. These recursions arise in a number of well-known and frequently studied problems, e.g. in the theory of controlled Markov chains, Leontief substitution systems, controlled branching processes, etc. Results concerning the asymptotic behavior ofx(n), forn→∞, are established in terms of the maximal spectral radius, the maximal index, and a set of generalized eigenvectors. A key role in the analysis is played by a geometric convergence result for value iteration in undiscounted multichain Markov decision processes. A new proof of this result is also presented.     

Two-photon absorption and energy band structure of orthorhombic Hg2Cl2 crystals

Dependence of two-photon absorption (TPA) rate on the state of polarization of a laser beam is investigated in the low-temperature orthorhombic modification of Hg₂Cl₂ crystals. Theoretical calculations of the dependence of TPA rate on the direction of polarization vector of the beam are performed for centrosymmetric points, Y, Z, T, R andS of the Brillouin zone. The domain structure of real crystals is taken into consideration and it is shown that periodicity of the polarization dependence may indicate whether TPA is due to transitions either at, Y, Z, T orR, S points. The polarization dependence of TPA cannot, however, distinguish between points inside these two groups. Comparison of theory with a low-temperature (T 8·5 K) experimental curve of polarization dependence is discussed. It is shown that the experiment can be explained in main features by a model of noninteracting oriented linear dipoles. Further, on the basis of TPA measurements, a simple energy band structure of Hg₂Cl₂ is proposed regarding Hg₂Cl₂ crystal as a linear chain of molecules.The authors express thanks to Dr. . Barta for supplying the Hg₂Cl₂ crystals, Dr. Z. Bryknar for critical comments and Dr. B. Velický for stimulating discussion. We thank also Dr. V. Kohlová for assistance during measurement.     

Using “quasiphotons” to compute wave fields in an elastic medium

Quasiphoton solutions are constructed for longitudinal and transversal waves in an elastic medium. The quasiphotons are then applied to determine the fields of nonstationary high-frequency point sources in a medium with parameters dependent on two Euclidean coordinates.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 148, pp. 89–103, 1985.     

Dual pairs and representations of scattering amplitudes

A procedure for constructing scattering amplitudes for production processes that is exactly unitary, preserves the bosonic character of the many-particle states, and is invariant with respect to an underlying symmetry group is given. Two simple models, dealing with isospin internal symmetry and the two-dimensional Euclidean space group are presented which illustrate how scattering amplitudes can be represented as matrix elements of groups whose action commutes with the action of the invariance group on the relevant Fock space.Invited talk presented at the International Conference Selected Topics in Quantum Field Theory and Mathematical Physics, Bechyn, Czechoslovakia, June 23–27, 1986.Work supported in part by the Department of Energy.     

Meson spectrum

Using the Klein-Gordon equation with a box potential, a mass formula describing the family of nonflavored meson states withI=1 is derived. The energy levels calculated agree with those observed within an accuracy of 5%. In the model discussed quarks behave like tachyons.