Vol 80, No 3 (2017)

The possibility of studying photonuclear reactions near the threshold by means of powerful femtosecond lasers is explored by considering the example of deuteron photodisintegration. The respective experiment was performed by employing the terawatt femtosecond laser facility of the International Laser Center at Moscow State University. The radiation from this facility is characterized by a pulse energy of up to 50 mJ, a duration of 50 fs, a repetition rate of 10 Hz, and a wavelength of 805 nm. This provides a power above 10¹⁸ W/cm². Intense relativistic-electron and photon beams of energy up to 10 MeV were obtained after the optimization of relevant experimental parameters, including the focus of the laser beam, its time structure, and the choice of target. The use of these beams made it possible to study neutron generation in heavy water, to measure the time of neutron moderation, and to determine the detection efficiency. The experimental data obtained in this way are in qualitative agreement with the results of simulations based on the GEANT-4 and LOENТ code packages and indicate that it is possible to create a neutron source on the basis of the aforementioned laser. The cross section measured for deuteron photodisintegration complies with theoretical estimates available in the literature.

Cross section and S factor of the proton- and alpha-induced reactions have been studied for the Ruthenium and tin isotopes in the effective energy range, i.e. Gamow window. These reactions are important for developing the understanding for nucleosynthesis, particularly for the synthesis of p nuclei (p process). In this work, cross sections and S factor have been calculated through TALYS in Hauser–Feshbach formalism using nuclear densities calculated in relativistic mean field (RMF) formalism. Calculated results of cross sections, S factor and nuclear structure have been compared with existing theoretical as well as experimental results available and are found to be in good agreement.

Occupation numbers and energies of proton and neutron orbits in the isotopes ¹⁰⁷Ag and ¹⁰⁹Ag were obtained on the basis of data on nucleon-stripping and nucleon-pickup reactions. A special data-analysis method reducing systematic and statistical uncertainties was applied in relevant calculations. It is shown that, in this region, the spin–parity of nuclei is determined by shells, pairing, and polarization. The schemes of proton and neutron (sub)orbits were constructed. These schemes explain the ground-state spin–parities of N, Z = 39–49 nuclei.

An experimental laboratory setup combining various gamma spectrometers and neutron generators that is intended for operating at the experimental nuclear-planetology facility deployed at the Joint Institute for Nuclear Research (Dubna, Russia) in order to perform physical calibrations of active gamma and neutron spectrometers is described.

Relative yields of high-x_F charged hadrons (π^±, К^±, р, \(\overline p \), and d) in proton–nucleus interactions at incident-proton momenta of 25 and 50 GeV/c were measured at an angle of 0° in the momentum range between 15 and 40 GeV/c. An upper limit on the forward production of two protons in proton–nucleus interactions at 50 GeV/c was estimated. The properties of a carbon beam with an energy of 25 GeV per nucleon and fragment yields in its interaction with nuclear targets were measured within a short exposure.

About 0.85 × 10⁵ events involving stopped μ⁺ and muonium decay were observed in a nuclear photoemulsion with the aim of searches for a light dark photon (DPh) in the decay process DPh → e⁺e⁻. With a probability of about 10⁻⁵, no event of the decay μ⁺ → е⁺ν_μν_е accompanied by an electron–positron pair was observed. In the interval of 1.1 MeV ≤ m_DPh ≤ 60 MeV, the mixing parameter ε² was estimated at about 10⁻⁵ to 10⁻⁴.

Heavy quarks of mass much greater than the Higgs boson (H) mass have virtually no effect on the cross section for Higgs boson production at the Large Hadron Collider (LHC). A mechanism that is responsible for the appearance of the respective small factors is presented, and their meaning is clarified. It appears that they precisely correspond to a simple quantum-mechanical picture of the H-production process.

Von Neumann’s procedure is applied to quantizing general relativity. Initial data for dynamical variables in the Planck epoch, where the Hubble parameter value coincided with the Planck mass are quantized. These initial data are defined in terms of the Fock orthogonal simplex in the tangent Minkowski spacetime and the Dirac conformal interval. The Einstein cosmological principle is used to average the logarithm of the determinant of the spatial metric over the spatial volume of the visible Universe. The splitting of general coordinate transformations into diffeomorphisms and transformations of the initial data is introduced. In accordance with von Neumann’s procedure, the vacuum state is treated is a quantum ensemble that is degenerate in quantum numbers of nonvacuum states. The distribution of the vacuum state leads to the Casimir effect in gravidynamics in just the same way as in electrodynamics. The generating functional for perturbation theory in gravidynamics is found by solving the quantum energy constraint. The applicability range of gravidynamics is discussed along with the possibility of employing this theory to interpret modern observational data.

We summarize some previous work on SU(4) describing hadron representations and transformations as well as its noncompact “counterpart” SU*(4) being the complex embedding of SL(2,H). So after having related the 16-dim Dirac algebra to SU*(4), on the one hand we have access to real, complex, and quaternionic Lie group chains and their respective algebras, on the other hand it is of course possible to relate physical descriptions to the respective representations. With emphasis on the common maximal compact subgroup USp(4), we are led to projective geometry of the real 3-space and various transfer principles which we use to extend the previous work on the rank 3-algebras above. On real spaces, such considerations are governed by the groups SO(n,m) with n + m = 6. The central thread, however, focuses here on line and Complex geometry which finds its well-known counterparts in descriptions of electromagnetism and special relativity as well as—using transfer principles—in Dirac, gauge, and quantum field theory. We discuss a simple picture where Complexe of second grade play the major and dominant rôle to unify (real) projective geometry, complex representation theory and line/Complex representations in order to proceed to dynamics.

We show how the discrete symmetries Z₂ and Z₃ combined with the superposition principle result in the SL(2,C) symmetry of quantum states. The role of Pauli’s exclusion principle in the derivation of the SL(2,C) symmetry is put forward as the source of the macroscopically observed Lorentz symmetry; then it is generalized for the case of the Z₃ grading replacing the usual Z₂ grading, leading to ternary commutation relations. We discuss the cubic and ternary generalizations of Grassmann algebra. Invariant cubic forms on such algebras are introduced, and it is shown how the SL(2,C) group arises naturally in the case of two generators only, as the symmetry group preserving these forms. The wave equation generalizing the Dirac operator to the Z₃-graded case is introduced, whose diagonalization leads to a sixthorder equation. The solutions of this equation cannot propagate because their exponents always contain non-oscillating real damping factor. We show how certain cubic products can propagate nevertheless. The model suggests the origin of the color SU(3) symmetry.

We formulate the construction of cyclic and non-cyclic complete sets of mutually unbiased bases, corresponding to the underlyining field and semifield structures, in the framework of the symplectic approach.

The magnetoemission of crusts of magnetars (ultramagnetized neutron stars) is considered as an origin of repeated soft gamma-ray bursts. It is shown that all observations of such bursts can be described and systematized on the basis of amodel of randomly jumping interacting moments that includes quantum fluctuations and internuclear magnetic interaction in inhomogeneous crusty nuclear matter.

We present a set of formulas to extract the gluon distribution function from the Berger–Block–Tan form of the deep inelastic structure function F₂ and its derivative dF₂/d ln Q² at small x in the leading order of perturbation theory.

The superconformal index on ℝℙ² × S¹ can be derived exactly by the localization technique and applied to the direct proof of Abelianmirror symmetry. We find two sets of parity conditions compatible with the unorientable property of ℝℙ² and then rigorously show two kinds of Abelian mirror symmetry via the index on ℝℙ² × S¹.

We review the classical properties of Tremblay–Turbiner–Winternitz and Post–Wintenitz systems and their relation with N-dimensional rational Calogero model with oscillator and Coulomb potentials, paying special attention to their hidden symmetries. Then we show that combining the radial coordinate and momentum in a single complex coordinate in a proper way, we get an elegant description for the hidden and dynamical symmetries in these systems related with action–angle variables.