abstract

The growth of small linear gravitational instabilities in the Hoyle–Narlikar and the Brans–Dicke theories of gravitation is discussed. It is shown that small linear adiabatic density fluctuations can grow faster (or protogalaxies could form earlier) in the \(G\)-variable cosmologies than in the general theory of relativity.

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It is shown that pure Yang–Mills mechanics is exponentially unstable even if an arbitrary, stable \(A^a_0\) component of the potential is included. However, stabilization of the theory is possible for the generalized Matinyan–Savvidi Ansatz on potentials when Higgs fields with sufficiently large vacuum expectation value are present.

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Corrections to cross sections for the Drell–Yan process on a nuclear target due to the change of quark distributions inside the nucleus are estimated. It is shown that these corrections should in principle be observable, especially for pion beams.

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The contribution of multiple soft quark collisions to the spectra of lepton pairs produced in high energy interactions is investigated as a function of their effective mass m. It is found that if this contribution is presented in the form \(A^{\alpha }\), where \(A\) is the atomic number of the nucleus, then \(\alpha \) increases slowly to \(\alpha \approx 1\), as \(m\) increases. Comparison of theoretical and experimental data is presented.

abstract

The contribution of soft multiple constituent quark collisions to the inclusive spectrum of large transverse momentum \(P_{\rm T}\) particles generating in hadron-nucleus reactions at high energies is studied. By analysing the reaction pA \(\to \pi \)X it is shown that this contribution is considerable and determines basically the \(\pi \) meson spectra at \(P_{\rm T} \lesssim 3\) GeV/\(c\), but it decreases at \(P_{\rm T} \gt 3\) GeV/\(c\). The inclusion of both soft and hard quark collisions inside the nucleus allows one to describe quite satisfactorily the \(A\) dependence of these \(\pi \) meson spectra within a wide region of \(P_{\rm T}\), \(P_{\rm T} = 1\div 6\) GeV/\(c\). The quark confinement effect on the results of \(\pi \) meson spectrum calculations is studied.

abstract

The energy density distribution in the central region (mean value and dispersion) is calculated for heavy ion collisions in the constituent quark model. The mean energy density increases slowly with the atomic number \(A\) for nucleus–nucleus collisions and even for uranium is around 1 GeV/fm\(^3\), below estimations of the critical energy of the transition to quark–gluon plasma. However, the fluctuations are large, so plasma may be formed in tubes of hadronic rather than nuclear size.

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The fit to charmonium and bottomium mass spectra by the same Coulomb-linear potential of quark–antiquark interactions is presented. The predictions of mass spectrum and leptonic half-widths of the hypothetical toponium system are given for a wide range of the top quark mass.

abstract

A review of strong CP problem, with the emphasis on the axion solution, is presented. The possibility that \(N=1\) supergravity governs weak interactions is discussed. I then argue that supergravity can provide a simple solution to the strong CP problem, which is free from a domain wall problem.

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The scale dependence of large \(p_{\rm T}\) hadron production is investigated and analyzed in terms of double moments for qq \(\to \) qX and qq \(\to \) gX partonic subprocesses in the next-to-leading order. Calculated here qq \(\to \) gX cross-section turns out to be small in comparison with quark fragmentation contribution and is shown not to influence the interaction scale extracted according to the fastest apparent convergence criterion.

abstract

The method of solving of classical Yang–Mills equations with external charges by means of the perturbative expansion in powers of the external charge \(\hat \varrho (\vec x)\) is considered in \(\hat A_0=0\) gauge. The gauge potentials are calculated in the first three orders for generic \(\hat \varrho \). It is observed that in general the external color charge generates color magnetic field of the monopole type (i.e., behaving like \(r^2\) for \(r \to \infty \)) in the second order, and that in the third order the color electric field behaves like \(r^{-1}\) for \(r \to \infty \). This gives infinite energy of such a color charge and motivates an argument that nonvanishing total color charge density (resultant for all kinds of colored quarks) can not be produced in any real experiment.

abstract

We review an idea that fragmentation of highly virtual quarks with four-momentum squared \(q^2 \gg {\mit \Lambda }^2 \sim O(1/r_h^2\)) but \(q^2 \ll s\) (semi-hard processes) is the main source of the secondary hadrons in very high energy hadron–hadron collisions.

abstract

A semi-empirical formula for calculating quadrupole deformation parameters of charge distributions in the nuclei with \(Z\), \(N \geq 6\) is presented. The formula is applied for calculating the reduced E2 transition probabilities — \(B\)(E2\(\uparrow \)) between ground- and first 2\(^+\) excited states in even–even nuclei. An attempt is made to explain this formula in a two–liquid-drop and a microscopic model.

abstract

The \(^{12}\)C(p,\(\gamma )^{13}\)reaction data are analyzed in terms of a modified direct-semidirect capture model, which accounts for the presence of broad resonances. The resonance at \(E_p=457\) keV is found to have to a good approximation pure single particle nature. Spectroscopic factor for the ground state of the \(^{13}\)N nucleus is found to be equal 0.88 \(\pm \) 0.11 and the astrophysical \(S\)-factor at 25 keV is found to be 1.74 \(\pm \) 0.18 keV \(\times \) barn.

abstract

The \(^{27}\)Al(\(\alpha \), t)\(^{28}\)Si reaction has been studied at three bombarding energies: 26.2, 26.45 and 26.7 MeV. The energy-averaged distributions for two states populated in \(^{28}\)Si have been compared with the finite-range DWBA calculations and Hauser–Feshbach theory. Spectroscopic amplitudes were calculated using the available shell-model wave functions.