The Hundredth Anniversary of Einstein's Annus Mirabilis

The year 2005 marks the hundredth anniversary of the pioneering contribution of Einstein's to modern physics in 1905. The discussion of Einstein's five groundbreaking fundamental papers, which change our picture of the universe and ideas about the microworld and cosmos, is given.Comment: 7 page

Achieving the required mobility in the solar system through Direct Fusion Drive

To develop a spacefaring civilization, humankind must develop technologies which enable safe, affordable and repeatable mobility through the solar system. One such technology is nuclear fusion propulsion which is at present under study mostly as a breakthrough toward the first interstellar probes. The aim of the present paper is to show that fusion drive is even more important in human planetary exploration and constitutes the natural solution to the problem of exploring and colonizing the solar system.Comment: 11 pages, 5 figure

Superfluidity in asymmetric electron-hole systems

The pairing in a system of electrons and holes in two spatially separated parallel planes is studied in the case of electron-hole asymmetry caused by the difference in the carriers masses and their chemical potentials. It is found that the superfluid state is possible in a wide range of the asymmetry parameters, because the asymmetries can effectively compensate each other. It is predicted that the system may exhibit two critical temperatures for some asymmetry parameters. The lower critical temperature corresponds to the superfluid transition induced by thermal fluctuations. In the asymmetric system a coexistence of the normal and superfluid states is possible even at zero temperature

Light and Electromagnetic Waves Teaching in Engineering Education

Suggestion of physics laboratory exercises and discussion of the physics laboratory curricula for engineering majors where the properties of light and electromagnetic waves are studied in parallel. It is shown that one of the important educational advantages of an experimental study of the properties of microwaves as an example of electromagnetic waves simultaneously with the properties of light are, on one hand, visualization of the properties of microwaves, and on the other hand, provide evidences that light is an electromagnetic wave.Comment: 7 pages, 5 figure

Few-body systems in condensed matter physics

This review focuses on the studies and computations of few-body systems of electrons and holes in condensed matter physics. We analyze and illustrate the application of a variety of methods for description of two- three- and four-body excitonic complexes such as an exciton, trion and biexciton in three-, two- and one-dimensional configuration spaces in various types of materials. We discuss and analyze the contributions made over the years to understanding how the reduction of dimensionality affects the binding energy of excitons, trions and biexcitons in bulk and low dimensional semiconductors and address the challenges that still remain.Comment: 24 pages, 5 figure

Advanced Optics with Laser Pointer and Metersticks

We are using a laser pointer as a light source, and metersticks as an optical branch and the screen for wave optics experiments. It is shown the setup for measurements of wavelength of laser light and rating radial spacing of the CD, diffraction on a wire and a slit, observation of a polarization of light and observation of a hologram.Comment: 7 pages, 8 figures, National Summer 2005 Meeting of the American Association of Physics Teacher, Presented at the Apparatus Competition, Low Cost Contest Winne

Towards superfluidity of dipolar excitons in a TMDC double layer

We study formation and superfluidity of dipolar excitons in double layer heterostructures formed by two transition metal dichalcogenide (TMDC) atomically thin layers. Considering screening effects for an electron-hole interaction via the harmonic oscillator approximation for the Keldysh potential, the analytical expressions for the exciton energy spectrum and the mean field critical temperature $T_{c}$ for the superfluidity are obtained. It is shown that binding energies of A excitons are larger than for B excitons. The mean field critical temperature for a two-component dilute exciton system in a TMDC double layer is analyzed and shown that latter is an increasing function of the factor $Q$, determined by the effective masses of A and B excitons and their reduced mass. Comparison of the calculations for $T_{c}$ performed by employing the Coulomb and Keldysh interactions demonstrates the importance of screening effects in TMDC.Comment: 14 pages, 5 figure

High-temperature superfuidity of the two-component Bose gas in a TMDC bilayer

The high-temperature superfluidity of two-dimensional dipolar excitons in two parallel TMDC layers is predicted. We study Bose-Einstein condensation in the two-component system of dipolar A and B excitons. The effective mass, energy spectrum of the collective excitations, the sound velocity and critical temperature are obtained for different TMDC materials. It is shown that in the Bogolubov approximation the sound velocity in the two-component dilute exciton Bose gas is always larger than in any one-component. The difference between the sound velocities for two-component and one-component dilute gases is caused by the fact that the sound velocity for two-component system depends on the reduced mass of A and B excitons, which is always smaller than the individual mass of A or B exciton. Due to this fact, the critical temperature Tc for superfluidity for the two-component exciton system in TMDC bilayer is about one order of magnitude higher than Tc in any one-component exciton system. We propose to observe the superfluidity of two-dimensional dipolar excitons in two parallel TMDC layers, which causes two opposite superconducting currents in each TMDC layer.Comment: 18 pages, 4 figure

Influence of high-angle grain boundaries on the charge order formation in the YBa2Cu3O7−δ\mathrm{YBa_2Cu_3O_{7-\delta}}

We are examining the possibility of the formation of charge order in the high-temperature superconductor $\mathrm{YBa_2Cu_3O_{7-\delta}}$ (YBCO) due to interaction between the charged oxygen vacancies or di-vacancies. The molecular dynamics method is used to analyze the displacement fields around these defects. The distribution of displacements around a single charged oxygen vacancy and di-vacancy, determination of binding energy of oxygen vacancy in di-vacancy demonstrate that there is, in principle, the possibility of the charge order formation in YBCO by charged oxygen vacancies or di-vacancies. It is shown that the charge order formation first of all should be formed near crystal lattice defects and that the high-angle grain boundaries (GBs) regions are preferable places for this formation. The adsorption capability of high-angle GBs with respect to the stripe embryo formation is determined. It is shown that there is a proportional dependence between the repetition distance along the high-angle GBs and an energy advantage of the stripe embryo formation in GBs.Comment: 7 pages, 4 figure

Deviations from Keplerian Orbits for Solar Sails

It is shown that the curvature of spacetime, a possible net electric charge on the sun, a small positive cosmological constant and the oblateness of the sun, in conjunction with solar radiation pressure (SPR), affect the bound orbital motion of solar sails and lead to deviations from Kepler's third law for heliocentric and non-Keplerian orbits. With regards to the Lense-Thirring effect, the SRP increases the amount of precession per orbit for polar orbits. Non-Keplerian polar orbits exhibit an analog of the Lense-Thirring effect in which the orbital plane precesses around the sun.Comment: 6 pages, 2 figures. Proceedings of the Sixth IAA Symposium on Realistic Near-Term Advanced Scientific Space Missions. Missions to the Outer Solar System and Beyond, pp. 37- 42, Aosta, Italy, 6-9 July, 200