Journal for Foundations and Applications of Physics
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Ab initio study of effect of pressure on structural and elastic properties of CaX, X = {O, S, Se}
Get PDFWe present density function theory study of effect of pressure on structural, elastic and electronics properties of compounds CaX (X=O, S and Se) within the generalized gradient approximation. The results presented for transition pressure, elastic parameters and band structures are in good agreement with the available literature. We also present the effect of pressure on these parameters. The generalized stability criteria show that CaSe is not stable above pressure of 29GPa and all the material CaX are not stable at B2 phase. The materials are brittle at equilibrium but this changes with pressure change. They are also generally anisotropic; CaO(B1) was found to be Isotropic at pressure of 12.5GPa. Finally, the band-gap of all the material around (Γ - X) decreased with pressure, all the material became indirect band-gap semiconductor at high pressure and CaSe undergoes a semiconductor-metal transition at pressure of 68 GPa
Isochronous and Unexpected Behavior for Complex-Valued Non-linear Oscillators with Parametric Excitation
Get PDFUsually oscillators with periodic excitations show a periodic motion with frequency equal to the forcing one. A complex-valued nonlinear oscillator under parametric excitation is investigated by an asymptotic perturbation method based on Fourier expansion and time rescaling. Four differential equations for two nonlinearly coupled oscillators are derived. Approximate solutions are obtained and their stability is discussed. We found that the resulting motion is periodic with a frequency equal to the forcing one, if appropriate inequalities are satisfied and then for a large parameter range. The system is isochronous because periodic solutions are possible in a well-defined phase region and not only for certain discrete values. Moreover, we demonstrate that if we insert a gyroscopic term the motion can be always periodic for a well-defined parameter range but with a frequency different from the forcing frequency. Analytic approximate solutions are checked by numerical integration
Effect of Pressure on Structural, Elastic and Electronic Properties of Perovskite PbTiO3
Get PDFWe study the effect of pressure on Structural, elastic and electronic properties of Cubic and Tetragonal Perovskite using density function theory. The equilibrium parameters obtained are in good agreement with the available literature both experimental and theoretical. We found out that there is transition from tetragonal to cubic at a pressure of around 30GPa. Both crystals are stable in the pressure range of this study (0 – 50 GPa), and the stability increases with increasing pressure. The bulk modulus (B), Young modulus (E) and Shear modulus (G) all increase with increasing pressure. The band-gap increases and decrease around (X-Gamma) and (M-Gamma) for the case of Cubic and decrease for the case of Tetragonal Crystal around (X-Gamma), (Z-Gamma) and (Z-X) which converges at pressure of around 30GPa
A new look at the quantum Liouville theorem
Get PDFWe clarify certain confusions in the literature of the density operator in quantum mechanics, and demonstrate that the quantum Liouville theorem has the same form in both the Schrodinger and the Heisenberg pictures. Our starting point is to treat the density operator as an observable which has its specific time dependence in each of the two pictures. It is further shown that such a formulation will provide the exact correspondence between classical and quantum statistical mechanics with the Liouville theorem being interpreted as a conservation law, which is derivable from the equation of motion only in the quantum case.
 
Observation of photon movement near Young’s double-slit
Get PDFThe quantum interference phenomenon was observed in Young’s double-slit experiment using a single photon, and then, the validity of quantum mechanics was demonstrated. However, the reason these fringes appear has not been completely explained yet because photon motion has not been investigated in detail. We found a method to observe the motion of photons using the properties of optical fibers and showed vector diagrams of the photon motion near the double-slit. The photons gradually changed their direction while intersecting and formed interference fringes. In addition, utilizing the mode property of the fiber, we observed fringes at its output end, even when one of the two interfering waves could not transmit through the fiber
Student Challenges in Understanding Quantum Mechanics: Effect of the “Logic paradigm shift”
Get PDFFor three centuries Newtonian mechanics had been firmly established as a valid theory for the understanding of physical reality; if one understands the laws of physics, then one understands the whole universe. Classical physicists had contented themselves with the search for regularities in measurements and in the physical world. Irregularities were regarded as noises that interfered with the deterministic picture of physical reality. However, from 1900s onwards with the quantum hypothesis, physicists had begun to recognize that the physics of Newton and Maxwell were inadequate for the understanding of all of the physical reality. For example, the interaction of radiation with matter could not be explained from classical physics. This dilemma led to the discovery of quantum mechanics. In this article we explore the challenges that students face in understanding quantum mechanics that arises from paradigm shift in the mode of reasoning about the physical world. The description of physical reality in general and quantum reality in particular requires that we shift our mode of reasoning from classical Boolean logic to quantum non Boolean logic
Bending motion of photons in Young\u27s double-slit
No full textThe investigation of the interference phenomenon of Young\u27s double-slit using a single photon is an epoch-making experiment demonstrating the mystery of quantum mechanics, but the details have not yet been clarified. We have developed a method for observing the behavior of photons near the double-slit using a multimode optical fiber to obtain a two-dimensional map of photon motion. Quantitative analysis of the directional motion revealed that the directional change was related to the derivative of the electric field and was uniquely determined by the direction of photon motion
Soil radioactivity and radiotoxic risks of uranium in drinking water. A case study of Jos Plateau, Nigeria
Get PDFProtection and assessment of any radiation pollution resulting from the use and disposal of radioactive materials to the large extent depend on the knowledge of natural radioactivity level of an environment. This work determined the activity concentration of terrestrial radionuclides 226Ra, 232Th and 40K in top soil samples of Jos Plateau using high resolution HPGe detector. Inductive Coupled Plasma (ICP) Mass Spectrometer was used to determine the chemical concentrations of uranium (238U) in drinking water samples collected from the area. The activity concentration of 226Ra varied between 34±1 and 1006±18 Bq/kg, 67±2 and 1695±37 Bq kg−1 for 232Th and between 67±4 and 2465±45 Bq/kg for 40K. Chemical concentration of 238U in water samples was found to vary from 1.4 to 35 μg/ L. The values of radiological risks due to radioactivity and chemical risks of mortality and morbidity due concentration of 238U in drinking water were estimated. The risk values for some samples are found to be within safe limits provided by health and environmental protection agencies (ICRP, WHO and USEPA). The radiometric data could be useful for geochemical exploration and diagnosis and prognosis of uranium persuaded diseases for the local inhabitants in the study area
A Nonlinear Approach for Quantum Mechanics
Get PDFThis work represents a possible way to achieve the Einstein-de Broglie soliton-particle concept. The weakly nonlinear Klein-Gordon equation (nonlinear quantum mechanics) is investigated by the asymptotic perturbation (AP) method for a particle confined in a box. The quantization of the energy with a slight difference with respect to the standard (linear) quantum mechanics is obtained. Both relativistic and non-relativistic cases are considered and the transition frequencies are slightly different for the linear and nonlinear quantum mechanics. Experimental verification is needed to choose between the two theories
The Gauge Principle from the Schrodinger-Born Wave Mechanics
Get PDFWe propose an elementary way of introducing the gauge principle to beginners with a background in only mechanics, electromagnetism, and quantum mechanics. This evolves from an apparent conflict in the Schrodinger-Born formulation of wave mechanics, and does not have to resort to advanced concepts like covariant derivative and minimal coupling. With such an approach, one would have appreciated how interactions can be dictated from consideration of internal symmetry of a physical system, which serves as a principle underlying the foundation of almost all modern physics. In addition, the gauge principle also serves as a resource providing consistency between the Born rule and Schrodinger’s wave mechanics