No Arabic abstract
The ideal Bose gas has two major shortcomings: at zero temperature, all the particles condense at zero energy or momentum, thus violating the Heisenberg principle; the second is that the pressure below the critical point is independent of density resulting in zero incompressibility (or infinite isothermal compressibility) which is unphysical. We propose a modification of the ideal Bose gas to take into account the Heisenberg principle. This modification results in a finite (in)compressibility at all temperatures and densities. The main properties of the ideal Bose gas are preserved, i.e. the relation between the critical temperature and density, but the specific heat has a maximum at the critical temperature instead of a discontinuity. Of course interactions are crucial for both cases in order to describe actual physical systems.
Oscillators and rotators are among the most important physical systems. For centuries the only known rotating systems that actually reached the limits of the ideal situation of undamped periodical motion were the planets in their orbits. Physics had to develop quantum mechanics to discover new systems that actually behaved like ideal, undamped, oscillators or rotators. However, all examples of this latter systems occur in atomic or molecular scale. The objective of the present letter is to show how the limit of ideal oscillating motion can be challenged by a man-made system. We demonstrate how a simple model electromechanical system consisting of a superconducting coil and a magnet can be made to display both mechanical and electrical undamped oscillations for certain experimental conditions. The effect might readily be attainable with the existing materials technologies and we discuss the conditions to circumvent energy losses. The result is a lossless system that might generate hundreds of Ampere of rectified electrical current by means of the periodical conversion between gravitational potential, kinetic, and magnetic energies.
A general cosmological principle -- Aleph -- is proposed as a substitute to the Anthropic principle. Furthermore, the universe, conceived as a world ensemble, is characterized by many (possibly infinite) X-Life world principles. The only known X-Life world principle recovers much of the Anthropic conjecture. The inescapable final conclusion is the formulation of the Strong Copernicus principle.
In current experiments with cold quantum gases in periodic potentials, interference fringe contrast is typically the easiest signal in which to look for effects of non-trivial many-body dynamics. In order better to calibrate such measurements, we analyse the background effect of thermal decoherence as it occurs in the absence of dynamical interparticle interactions. We study the effect of optical lattice potentials, as experimentally applied, on the condensed fraction of a non-interacting Bose gas in local thermal equilibrium at finite temperatures. We show that the experimentally observed decrease of the condensate fraction in the presence of the lattice can be attributed, up to a threshold lattice height, purely to ideal gas thermodynamics; conversely we confirm that sharper decreases in first-order coherence observed in stronger lattices are indeed attributable to many-body physics. Our results also suggest that the fringe visibility kinks observed in F.Gerbier et al., Phys. Rev. Lett. 95, 050404 (2005) may be explained in terms of the competition between increasing lattice strength and increasing mean gas density, as the gaussian profile of the red-detuned lattice lasers also increases the effective strength of the harmonic trap.
We show how the remotest sites of a finite lattice can be entangled, with the amount of entanglement exceeding that of a singlet, solely through the dynamics of an ideal Bose gas in a special initial state in the lattice. When additional occupation number measurements are made on the intermediate lattice sites, then the amount of entanglement and the length of the lattice separating the entangled sites can be significantly enhanced. The entanglement generated by this dynamical procedure is found to be higher than that for the ground state of an ideal Bose gas in the same lattice. A second dynamical evolution is shown to verify the existence of these entangled states, as well entangle qubits belonging to well separated quantum registers.
The traditional celestial navigation system (CNS) is used the moon, stars, and planets as celestial guides. Then the star tracker (i.e. track one star or planet or angle between it) and star sensor (i.e. sense many star simultaneous) be used to determine the attitude of the spacecraft. Pulsar navigation also be introduced to CNS. Maser is another interested celestial in radio astronomy which has strong flux density as spectral line. Now we analysis the principle of maser navigation which base on measuring Doppler shift frequency spectra and the feasibility that use the exist instrument. We give the navigation equations of maser-based navigation system and discuss the integrated navigation use maser, then give the perspective in the Milky Way and the intergalatic. Our analysis show that use one meter antenna can achieve tens of meters position accuracy which better than todays star sensor. After integrated with maser navigation, pulsar navigation and star sensor in CNS and inertial navigation system, is it not only increase the reliability and redundancy of navigation or guiding system but also can less or abolish the depend of Global Navigation Satellite System (GNSS) which include GPS, GRONSS, Galileo and BeiDou et al. Maser navigation can give the continuous position in deep space, that means we can freedom fly successfully in the Milky Way which use celestial navigation that include maser, pulsar and traditional star sensor. Maser as nature beacon in the universe will make human freely fly in the space of the Milky Way, even outer of it. That is extraordinary in the human evolution to type III of Kardashev civilizations.