International Journal of Modern Physics A

It is discussed how the ideas of entropy and the second law of thermodynamics, conceived long ago during the nineteenth century, underly why cosmological dark matter exists and originated in the first three years of the universe in the form of primordial black holes, a very large number of which have many solar masses including up to the supermassive black holes at the centres of galaxies. Certain upper bounds on dark astrophysical objects with many solar masses based on analysis of the CMB spectrum and published in the literature are criticised. For completeness we discuss WIMPs and axions which are leading particle theory candidates for the constituents of dark matter. The PIMBHs (Primordial Intermediate Mass Black Holes) with many solar masses should be readily detectable in microlensing experiments which search the Magallenic Clouds and measure light curves with durations of from one year up to several years.

This work summarizes the current status of the measured semileptonic branching fractions ${\bar{B}}^{0,-}\to X_c\mu \nu$. The sum of exclusive measurements is compared with the inclusive determination, accounting for isospin extrapolation. Further derived quantities are computed, taking into account different explanations for the unmeasured components of the total branching fraction. These quantities focus on the charge breakdown of the final states, and are designed for use as inputs or comparisons in future experimental measurements.

In this paper, we consider the metric of a (2+1)-dimensional rotating acoustic black hole in the neo-Newtonian theory to compute the Hawking temperature, and applying the quantum statistical method, we calculate the statistical entropy using a corrected state density due to the generalized uncertainty principle (GUP). In our calculations, we have shown that the obtained entropy is finite and correction terms are generated. Moreover, the computation of the entropy for this method does not present logarithmic corrections.

We have studied the effect of energy-dependent potentials for the relativistic spinning particle using the formalism for supersymmetric path integrals. That leaves behind a new normalization of wave function, which is examined via the Dirac equation and can be confirmed by Feynman’s path integral method. Based on two important examples, Coulomb and Harmonic oscillator potentials, we find that the frequency and the Coulomb’s constant are dependent on spectral parameters. The propagator is calculated and the energy eigenvalues with their corresponding eigenfunctions are deduced.

Using the general properties that have emerged from $E$ theory we sketch the generic features of the dynamics of branes in seven and eight dimensions. The dynamical equations are a set of duality equations involving the coordinates of the vector representation of $E_{11}$.

In the present paper, we investigated the gravitational black-hole-hedgehog’s solution with magnetic field contribution in the framework of the $f(R)$-gravity described by the Gravi-weak unification (GWU) model. Assuming the Multiple Point Principle (MPP), we considered the existence of the two degenerate vacua of the Universe: the first Electroweak (EW)-vacuum with $v_1\approx 246$ GeV (“true vacuum”), and the second Planck scale (“false vacuum”) with $v_2\sim 10^{18}$ GeV. In these vacua, we investigated different topological defects. The main aim of this paper is an investigation of the black-hole-hedgehog configurations as defects of the “false vacuum.” We have obtained the solution which corresponds to a global monopole, that has been “swallowed” by the black-hole with core mass $M_{\mathrm{\text{BH}}}\approx 3.65\times 10^{18}$ GeV and radius $\delta \approx 6\cdot 10^{-21}$ GeV${}^{-1}$. We investigated the metric in the vicinity of the black-hole-hedgehog and estimated its horizon radius: $r_h\approx 1.14\delta$. We have considered the phase transition from the “false vacuum” to the “true vacuum” and confirmed the stability of the EW-vacuum.

Einstein gravity supplemented by a scalar field nonminimally coupled to a Gauss–Bonnet term provides an example of model of scalar-tensor gravity where hairy black holes do exist. We consider the classical equations within a metric endowed with a NUT-charge and obtain a two-parameter family of nutty-hairy black holes. The pattern of these solutions in the exterior and the interior of their horizon is studied in some details. The influence of both — the hairs and the NUT-charge — on the lightlike and timelike geodesics is emphasized.

The framed standard model (FSM), constructed initially for explaining the existence of three fermion generations and the hierarchical mass and mixing patterns of quarks and leptons,${}^{1,2}$ suggests also a “hidden sector” of particles³ including some dark matter candidates. It predicts in addition a new vector boson $G$, with mass of order TeV, which mixes with the $\gamma$ and $Z$ of the standard model yielding deviations from the standard mixing scheme, all calculable in terms of a single unknown parameter $m_G$. Given that standard mixing has been tested already to great accuracy by experiment, this could lead to contradictions, but it is shown here that for the three crucial and testable cases so far studied (i) $m_Z-m_W$, (ii) $\mathrm{\Gamma }(Z\to {\ell }^{+}{\ell }^{-})$, (iii) $\mathrm{\Gamma }(Z\to \mathrm{\text{hadrons}}$), the deviations are all within the present stringent experimental bounds provided $m_G>1$ TeV, but should soon be detectable if experimental accuracy improves. This comes about because of some subtle cancellations, which might have a deeper reason that is not yet understood. By virtue of mixing, $G$ can be produced at the LHC and appear as a ${\ell }^{+}{\ell }^{-}$ anomaly. If found, it will be of interest not only for its own sake but serve also as a window on to the “hidden sector” into which it will mostly decay, with dark matter candidates as most likely products.

The angular asymmetry in decays of polarized muons and tau leptons is discussed. Both the standard $V\text{–}A$ Fermi model and the general parametrization via Michel parameters are considered. Numerical importance of contributions suppressed by charged lepton mass ratio is underlined. Contribution of the second order QED correction is estimated in the leading logarithm approximation.

We show that for a heavy vector-like quark model with a down type isosinglet, branching ratio for $c\to u\gamma$ decay is enhanced by more than ${𝒪}(10^2)$ as compared to that in the Standard model when QCD corrections to next-to-leading order are incorporated. In a left–right symmetric model (LRSM) along with a heavy vector-like fermion, enhancement of this order can be achieved at the bare (QCD uncorrected) level itself. We propose that a measurement of the photon polarization could be used to signal the presence of such new physics in spite of the large long distance effects. We find that there is a large region within the allowed parameter space of the model with a vector-like quark and an additional left–right symmetry, where, the photon polarization can be dominantly right-handed.

For more than 40 years virtually all work on the theory of type Ia Supernovae (SN Ia) has assumed that these explosions were due to the transfer of mass to a degenerate star from a partner in a binary system. In these binary models, when the mass of one partner closely approaches the Chandrasekhar maximum for a stable degenerate system, fusion can be initiated and the star explodes. However, a number of long-standing nagging problems and the inability of any specific binary model to fit any significant fraction of SN Ia events suggest that fusion could instead be triggered by a phase transition in a sub-Chandrasekhar white dwarf star. It is possible that remarkable host galaxy effects not considered in previous work on phase transition models could point to a specific source of the supernova trigger. Performing a least ${\chi }^2$ fit to the delay time distribution to fix parameters, we give predictions from the SUSY phase transition model for the host galaxy effects. In addition we discuss a SUSY insight into the Phillips relation which is basic to the cosmological importance of the type Ia supernovae.

Within the left–right symmetric model (LRM) the $Z$ boson decay into the channel $Z\to \tau \mu$ are investigated. The branching ratios of this decay is found in the third order of the perturbation theory. The obtained expression does not equal to zero only at the existence of the neutrino mixings. This means that from the point of view of the LRM, the nonconservations of the neutral and the charged lepton flavors have the same nature. As a result, the elucidation of the decays $Z\to l_i{\bar{l}}_k$ $(i\ne k)$ could provide data concerned the neutrino sector structure of the LRM. The neutrino sector parameters which could be measured in that case are as follows: (i) difference of the heavy neutrino masses; (ii) heavy–heavy neutrino mixing; (iii) heavy–light neutrino mixing.