We show that a geometric techniques can be elaborated and applied for constructing generic off-diagonal exact solutions in f (R, T )-modified gravity for systems of gravitational-Yang-Mills-Higgs equations. The corresponding classes of metrics and generalized connections are determined by generating and integration functions which depend, in general, on all space and time coordinates and may possess, or not, Killing symmetries. For nonholonomic constraints resulting in Levi-Civita configurations, we can extract solutions of the Einstein-Yang-Mills-Higgs equations. We show that the constructions simplify substantially for metrics with at least one Killing vector. There are provided and analyzed some examples of exact solutions describing generic off-diagonal modifications to black hole/ellipsoid and solitonic configurations.MSC 2010: 83T13, 83C15 (primary); 53C07, 70S15 (secondary)

The strong form factor of the B c B c J/ vertex is calculated in the framework of the QCD sum rules method at finite temperature. Taking into account additional operators appearing at finite temperature, a thermal Wilson expansion is obtained and QCD sum rules are derived. While increasing the temperature, the strong form factor remains unchanged up to T 100 MeV but slightly increases after this point. After T 160 MeV, the form factor suddenly decreases up to T 170 MeV. The obtained result of the coupling constant by fitting the form factor at Q 2 = −m 2 offshell at T = 0 is in a very good agreement with the QCD sum rules calculations in the case of vacuum. Our prediction can be checked in future experiments.

The strong coupling constants among mesons are very important quantities as they can provide useful information on the nature of strong interaction among hadrons as well as the QCD vacuum. In this article, we investigate the strong vertices of the

Abstract:In this paper, we deal with the temperature dependence of the leptonic decay constant and mass of Bs meson in the framework of the Hilbert moment QCD sum rule. In our calculations, we improve the thermal QCD sum rules, taking into account the thermal spectral density and the perturbative 2-loop order corrections to the correlation function. Moreover, we investigate the stability of the results with respect to the Hilbert moment parameter. Our numerical calculations demonstrate that the mass and decay constant are insensitive to the variation of temperature up to T ∼ = 100 MeV ; however, after this value, they start to decrease with increasing temperature. We observe that the results are stable for different values of the Hilbert moment parameter, n . At deconfinement or critical temperature, the decay constant and mass approach to roughly 16% and 78% of their values at zero temperature, respectively. The obtained results at zero temperature are in good agreement with the existing experimental data as well as predictions of the other nonperturbative models.

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