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The Morris–Thorne wormhole and vacuum equations in the conformal Poincaré-gauge theory of gravitation are considered. It is shown that wormholes cannot be realized as configurations of a “usual” matter. It is obtained also that dynamic vacuum solutions for spherical symmetric case coincide with the corresponding GR solutions.

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We investigate the behaviour of a non-commutative radiating Reissner–Nordstrom(Re–No)black hole. We find some interesting results: (a) the existence of a minimal non-zero mass to which the black hole can shrink, (b) a finite maximum temperature that the black hole can reach before cooling down to absolute zero, (c) compared to the neutral black holes the effect of charge is to increase the minimal non-zero mass and lower the maximum temperature, (d) the absence of any curvature singularity. We also derive some essential thermodynamic quantities from which we study the stability of the black hole. Finally we find an upper bound for the non-commutativity parameter \(\theta \).

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Euclidean and Lorentzian quantum-cosmological methods for setting the cosmological constant to zero are discussed, with particular reference to the superstring theory.

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A new class of solutions in the signum-Klein–Gordon model is presented. Our solutions merge properties of shock waves and compactons that appear in scalar field models with V-shaped potentials.

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The problem of the particle with variable mass is considered by the approach of path integral. The Green’s function related to this problem is reduced to that of a particle with a constant mass. As examples, simple cases are considered.

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The twisted Lie-algebraically deformed relativistic and nonrelativistic phase spaces are constructed with the use of Heisenberg double procedure. The corresponding Heisenberg uncertainty principles are discussed as well.

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Making use of a general formula for the RG improved effective (Coleman–Weinberg) potential for classically conformal models and applying it to several examples of physical interest, and in particular a model of QCD coupled via quarks to a colorless scalar field, we discuss the range of validity of the effective potential as well as the issue of ‘large logarithms’ in a way different from previous such analyses. In all examples considered, convexity of the effective potential is restored by the RG improvement, or otherwise the potential becomes unstable. In the former case, symmetry breaking becomes unavoidable due to the appearance of an infrared barrier \({{{\mit \Lambda }_{\rm IR}}}\), which hints at a so far unsuspected link between \({\mit \Lambda }_{\rm QCD}\) and the scale of electroweak symmetry breaking.

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We investigate the effect of an additional generation of ordinary quarks and vector quarks on longitudinal and transverse amplitudes associated with the exclusive \(B^{\,0}\to {\mit \Phi } K^*\) decays. We perform \(\chi ^{\,2}\) fits to the experimental data with respect to these two model parameters. Even though distinct minima (\(\chi ^2_0\)) are observed but \(\chi ^2_0 /\)d.o.f. values much larger than one indicates that such a constrained extension of the standard model cannot resolve the polarization puzzle in the \(B^{\,0}\to {\mit \Phi } K^*\) decay mode.

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A weak photon interaction with the hidden sector of the Universe, introduced recently to realize a “photonic portal” (to such a hypothetic sector responsible for cold dark matter), is conjectured to be embedded in a more extended weak interaction displaying electroweak symmetry spontaneously broken by the Standard-Model Higgs mechanism. This is a hypothetic new weak interaction between hidden and Standard-Model sectors of the Universe, appearing in our model in addition to the conventional electroweak interaction acting in the Standard-Model sector.

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Charmless two-body decays of \(B_{\rm s}\) mesons to \(PP\), \(PV\) and \(VV\) final states are investigated within an extension of the standard model with an additional vector quark. Besides the CP averaged branching ratio, we look into the direct CP violation associated with each mode to search for those decays which are most sensitive to this new physics scenario. Our results indicate that the branching ratio of \(B_{\rm s}\rightarrow \pi ^0 \eta ,\pi ^0 \eta ', \pi ^0 \phi \) receive the most significant shifts from the presence of a singlet quark. On the other hand, the direct CP violations in \(B_{\rm s}\rightarrow \phi \eta ', \phi \phi \) are the most affected by the vector quark model.

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We consider the scalar sector of the most general renormalizable two-Higgs-doublet model at non-zero temperature. We calculate the largest finite temperature corrections to the free-energy density and study thermal evolution of the ground state. Within the approximation chosen, we establish all possible sequences of thermal phase transitions and study their relation with the symmetries of the model. We show, in particular, that a charge-breaking or a CP-violating vacuum can arise at intermediate stages of thermal evolution, and that the first-order phase transition is associated with a discrete symmetry of the potential, but not of the entire scalar Lagrangian.

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Solving the Dirac equation with equal five-parameter exponent-type scalar and vector potentials in terms of the supersymmetric quantum mechanics method and shape invariance approach, we obtain the exact energy equation for the \(s\)-wave bound states. This work is performed under the conditions of the spin symmetry and pseudospin symmetry.

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An alternative, to the commonly used blast-wave, model describing the freeze-out hypersurface is applied to fit the \(p_{\rm T}\)-spectra of identified hadrons measured at relativistic heavy-ion collisions at \(\sqrt {s_{\rm NN}}=62.4, 130\) and 200 GeV. Decays of resonances are taken into account completely. It has turned out that the fitted freeze-out temperature and baryon number chemical potential depend weakly on the centrality of the collision and their values are close to the chemical freeze-out values determined from fits to particle yield ratios.

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We discuss the evolution of anisotropic boost-invariant quark–gluon plasma possibly created at the early stages of relativistic heavy-ion collisions. Our considerations are based on the recently proposed formalism that is an extension of the relativistic perfect-fluid hydrodynamics. We analyze (i) the pure partonic system described by the anisotropic phase-space distribution function and (ii) the system of partons interacting with the local magnetic fields. The second analysis is a simplified attempt to include the effects of color fields on the particle dynamics. Our model results are discussed in the context of early thermalization and isotropization. Under general assumptions of the particle, energy, and momentum conservations we show that for large evolution times the ratio of the longitudinal and transverse pressures of the pure partonic system tends to zero. Hence, the system with the initial momentum distribution elongated along the beam axis always passes through the isotropic stage where the transverse and longitudinal pressures are equal. The inclusion of the magnetic field in this case gives negative contribution to the longitudinal pressure, hence the transient stage when the total longitudinal and transverse pressures become equal may be reached earlier, depending on the strength of the field.

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A tachyon field having a negative squared-mass \(-m_{\rm t}^2\) can be described in terms of massless fields degenerated infinitely with respect to the helicity. The degeneracy leads symmetry breakings of space-time. This picture for the tachyon does not contradict causality. The tachyon vector-field is quenched from the interactions with matter fields, and the effects can be represented by a phase factor. The accelerated expansion of the universe and the dark energies are interpreted in terms of the phase factor. An asymmetry between the distribution of particles and that of anti-particles in the universe is also derived from the phase. Membranes can be described by the tachyon wave packet.

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The properties of the quantum universe on extremely small spacetime scales are studied in the semi-classical approach to the well-defined quantum model. It is shown that near the initial cosmological singularity point quantum gravity effects \(\sim \hbar \) exhibit themselves in the form of additional matter source with the negative pressure and the equation of state as for ultrastiff matter. The analytical solution of the equations of theory of gravity, in which matter is represented by the radiation and additional matter source of quantum nature, is found. It is shown that in the stage of the evolution of the universe, when quantum corrections \(\sim \hbar \) dominate over the radiation, the geometry of the universe is described by the metric which is conformal to a metric of a unit four-sphere in a five-dimensional Euclidean flat space. In the radiation dominated era the metric is found to be conformal to a unit hyperboloid embedded in a five-dimensional Lorentz-signatured flat space. The origin of the universe can be interpreted as a quantum transition of the system from the region in a phase space with a trajectory in imaginary time into the region, where the equations of motion have the solution in real time. Near the boundary between two regions the universe undergoes almost an exponential expansion which passes smoothly into the expansion under the action of radiation dominating over matter. As a result of such a quantum transition the geometry of the universe changes. This agrees with the hypothesis about the possible change of geometry after the nucleation of expanding universe from ‘nothing’.