Physics

One of the greatest mysteries in astrophysics and cosmology is the nature and the origin of cold dark matter, which represents more than 84% of the mass in the universe. Dark matter reacts on and produces gravitational forces and governs the dynamics of stars around galactic centres, however, does not absorb or emit any kind of electromagnetic radiation. So far, any relation to known types of matter has not been conclusive, and proposed new particles have not been found. Here, I propose and discuss how dark matter evolved from ultra-light fermionic particles that decoupled from the rest of the universe shortly after the Big Bang. My description explicitly considers their interference, and reveals the emergence of entanglement between two such particles, as well as their transformation to massive dark-matter quantum fields of cosmic sizes. Furthermore, I argue that dark matter and supermassive black holes have the same origin and evolved simultaneously. If the particles' decoupling time was about half a second after the Big Bang, my hypothesis predicts a minimum mass for supermassive black holes that fits well to the smallest known such object of 50,000 solar masses. It seems very much likely that the ultra-light fermionic particle was the neutrino.

Under the spirit of J. Polchinsky's introduction of D-brane in the string target spacetime (or 'bulk', for short), we consider the presence of both closed and open superstrings and coupling of their low-lying modes in the bulk. As a probe to explore the astrophysical and cosmological implications of the superstring theory at larger length scale or in low-energy dynamics, we construct the Yang-Mills monopole black hole solution and investigate its features. Our results exhibit that as a result of intimate interactions among low-lying modes, some cherished features of classical gravitation and cosmology break down. They are the violation of black hole no-hair theorem and the break down of cosmic censorship hypothesis. We learn from this lesson that these implications of fully developed superstring theory in classical gravitation and cosmology largely depart from our conventional wisdom signaling that the most current version of superstring theory is indeed the best candidate for quantum theory of gravitation.

We study in detail the electromagnetic fields and the Poynting flux in the case of a uniformly accelerated charge, in order to examine whether such a charge does `emit' radiation, especially in view of the widely accepted fact that there is no radiation reaction on the charge. Our concern, in particular, is with the Poynting flow computed at large distances (approaching infinity!) from the time-retarded positions of uniformly accelerated charge, and taken as an evidence of radiation emitted by the charge, which we shall demonstrate to be not true. As the charge picks up speed due to a constant acceleration, the energy in its self-fields accordingly increases and the Poynting flow, usually inferred as radiation, actually forms part of the requisite energy being fed into fields, at a rate just sufficient to match the increasing energy in its self-fields at various distances from the uniformly accelerated charge, including that in the far-off regions. In fact, for the decelerating charge, the energy in its self-fields decreases, at all distances from the charge, till it comes to momentary rest with no energy in its transverse fields, and this decrease in energy is shown {\em everywhere} by an inward radial flow of the Poynting vector, toward the `present' position of the decelerating charge. Moreover, there is a convective flow of self-fields of the charge, seen as a Poynting flow component always along the `present' direction of motion of the charge. Further, we shall show that effectively the electromagnetic fields, including the acceleration fields, even when they are at large distances from the time-retarded position of the charge, they continue to be all around the `present' position of the charge which itself is moving toward infinity due to the uniform acceleration.

In this paper, the authors aim to find out the origin of the corona and the duration of the present pandemic caused by it. Besides, they aim to find out the reason for such outbreaks occurring often in China. They make a hypothesis that the origin of the virus is embedded in the solar cycle. Next, they have proved the hypothesis by investigating the sunspot number, the cosmic ray flux data, the concentration of 10 Be in the ice core in Greenland and based on the occurrence of past pandemics and endemics. The study shows that whenever the Sun is in the magnetically quiescent state, the world witnesses viral diseases. The study shows that the outbreak of the Corona is because of the minimum sunspot number during 2019-2020 and the Corona is likely to stay in the whole of 2020. The study indicates the occurrence of viral diseases in every 11-13 years. It also reveals that as the stratospheric thickness is the minimum at Wuhan, the virus had chosen this place as the first entry point to the Earth.

In the present article we investigate the spin-1/2 and spin-1 cases in different bases. Next, we look for relations with the Majorana-like field operator. We show explicitly incompatibility of the Majorana anzatzen with the Dirac-like field operators in both the original Majorana theory and its generalizations. Several explicit examples are presented for higher spins too. It seems that the calculations in the helicity basis only give mathematically and physically reasonable results.

Here, we consider the Bell experiment for a system described by multipartite states in the case where n-dichotomic observables are measured per site. If n is two, we consider a two-setting Bell experiment. If n is three, we consider a three-setting Bell experiment. Twosetting model is an explicit local realistic model for the values of a correlation function, given in a two-setting Bell experiment. Three-setting model is an explicit local realistic model for the values of a correlation function, given in a three-setting Bell experiment. In the non-contextual scenario, there is not the difference between three-setting model and two-setting model. And we cannot classify local realistic theories in this case. This says that we can construct three-setting model from two-setting model. Surprisingly we can discuss incompleteness in the Bell theorem using non-contextual model. On the other hand, in the contextual scenario, there is the difference between three-setting model and two-setting model. This says that we must distinguish three-setting model from two-setting model. And we can classify local realistic theories in this case.

An important methodological problem of theoretical mechanics related to inertia is discussed. Analysis Inertia is performed in four-dimensional Minkowski space-time based on the law of conservation of energy-momentum. This approach allows us to combine the laws of conservation of momentum and angular momentum into a single law and separate the forces of inertia that actually exist in nature from the imaginary forces introduced to simplify calculations or arising from the transition from one frame of reference to another. From the energy-momentum tensor, in a non-relativistic approximation, the equation of balance of inertia forces existing in nature for a moving continuous medium and a material point in an inertial frame of reference is obtained. It follows from this equation that the pseudo-Euclidean geometry of our world plays an important role in the manifestation of inertia forces. The tensor and the balance equations of all inertia forces in a continuous medium a moving with angular acceleration are obtained. This allows uniform formulation and presentation of the original categories and concepts of classical and relativistic mechanics in educational and scientific literature within the framework of the current paradigm.

In this article the reduction of a n -dimensional space to a k -dimensional space is considered as a reduction of N n states to N k states, where N stands for the number of single-particle states per unit of spatial length. It turns out, this space reduction could be understood as another definition of inflation. It is shown that the introduction of the non-associativity of the algebra of physical fields in a homogeneous space leads to a nonlinear equation, the solutions of which can be considered as two-stage inflation. Using the example of reduction T× R 7 to T× R 3 , it is shown that there is a continuous cross-linking of the Friedmann and inflationary stages of algebraic inflation at times 10 −15 with the number of baryons 10 80 in the Universe. In this paper, we construct a new gravitational constant based on a nonassociative octonion algebra.

The paper explores the interacting Tsallis holographic dark energy (THDE) model in a non-flat universe following an infrared cutoff as the apparent horizon. The equation of state (EoS) and the deceleration parameter of THDE model are determined to understand the cosmological evolution for interacting THDE model in the nonflat universe. By applying the statefinder (r,s) parameter-pairs diagnostic and ω D − ω ′ D pair dynamical analysis for the derived THDE model, we plot the evolutionary trajectories for different cases of Tsallis parameter δ and interaction term b 2 and also, for spatial curvature Ω k0 =0,−0.0012 and 0.0026 corresponding to flat, open and closed universes, respectively, in the framework of Planck 2018 base cosmology results VI-LCDM observational data.

The interactions between the spin of fermionic matter and torsion in the Einstein-Cartan-Sciama-Kibble (ECSK) theory of gravity provides a repulsive gravitational potential at the very dense states of fermionic matter, which prevents the formation of black hole singularities inside the deeper horizon. While the fermionic matter in the black hole is attracted by the black hole at the beginning, after a critical point it is repelled to bounce at a critical high density and then expand into other side of the horizon as a newly created space, which may be considered as a nonsingular, closed universe. We constructed the action of these fermions in a black hole with torsion in the framework of ECSK theory of gravity from which the free Dirac action is inferred to obtain the interaction potential. The creation of a bouncing universe with the extremely repulsive potential may be related to the running vacuum and the modified Friedmann equations yield the consistent cosmological parameters with present FRW universe. Finally, this scenario naturally solves the flatness and horizon problems of cosmology without introducing finely tuned scalar fields, or more complicated functions of the Ricci Scalar R in the gravitational action.