Sequence Of Physical Processes Research Articles

On the gravitational redshift

The study of the gravitational redshift—a relative wavelength increase of ≈2×10-6 was predicted for solar radiation by Einstein in 1908—is still an important subject in modern physics. In a dispute whether or not atom interferometry experiments can be employed for gravitational redshift measurements, two research teams have recently disagreed on the physical cause of the shift. Regardless of any discussion on the interferometer aspect—we find that both groups of authors miss the important point that the ratio of gravitational to the electrostatic forces is generally very small. For instance, the ratio of the gravitational force acting on an electron in a hydrogen atom situated in the Sun’s photosphere to the electrostatic force between the proton and the electron in such an atom is approximately 3×10-21. A comparison of this ratio with the predicted and observed solar redshift indicates a discrepancy of many orders of magnitude. With Einstein’s early assumption that the frequencies of spectral lines depend only on the generating ions themselves as starting point, we show that a solution can be formulated based on a two-step process in analogy with Fermi’s treatment of the Doppler effect. It provides a sequence of physical processes in line with the conservation of energy and momentum resulting in the observed shift and does not employ a geometric description. The gravitational field affects the release of the photon and not the atomic transition. The control parameter is the speed of light. The atomic emission is then contrasted with the gravitational redshift of matter–antimatter annihilation events.

A sequence of physical processes determined and quantified in LAOS: An instantaneous local 2D/3D approach

An entirely new way of analyzing linear and nonlinear oscillatory material responses is presented. The new quantitative sequence of physical processes (SPP) method views generic oscillatory responses within the Frenet-Serret frame as sequences of planar 2D curves embedded in the 3D space defined by the strain, strain rate, and stress axes. Associated with the curve within each so-called “osculating” plane is a binormal vector that wholly determines the orientation of the plane. Physically meaningful information is obtained by calculating the angles between a modified form of the binormal vector and two reference vectors from local information at any point in a cycle. Information from a full period of oscillation is not a requirement of this technique, so that moduli can be calculated from partial or incomplete oscillations. Time-dependent phase and complex modulus information, or dynamic moduli information are obtainable throughout a period for arbitrary oscillatory responses. The SPP method is applied to the Bingham plastic model, power-law fluids, the Herschel–Bulkley model, and the nonlinear Giesekus model to accustom readers to its function. Application of the SPP method to these nonlinear models necessitates the refinement of some common language, as well as changes to the way results from strain amplitude sweeps are displayed and discussed.

Oscillatory yielding of a colloidal star glass

We investigate the response of a well-characterized colloidal star glass to large-amplitude oscillatory stress and strain fields. By combining these measurements with dynamic time sweeps we demonstrate the importance of probing both strain- and stress-induced nonlinear rheology of such complex fluids in order to elucidate the yielding and fluidization behavior. We also show that, due to the strong time dependence, it is essential to perform dynamic time sweeps at different strain and stress amplitudes, which result in different departures of the glass cage from its quiescent quasiequilibrium structure. This allows for steady-state responses to be reached and for nonlinear oscillatory responses to be treated properly while also suggesting that yielding is a gradual process. Further, we use a recently published framework for analyzing nonlinear responses to large-amplitude oscillatory shear [Rogers et al., J. Rheol. 55, 435 (2011)], based on the analysis of the whole stress waveforms as a sequence of physical processes, in order to measure the points of static and dynamic yielding. By doing so, we show that the stress-amplitude dependence of the dynamic yield stress can be linked to the strain-rate-amplitude dependence via the form of the steady-state flow curve.

Supersonic plasma jet interaction with gases and plasmas

The interaction of supersonic plasma jets with dense gases and plasmas has been studied experimentally and theoretically. Collimated plasma jets were generated from the laser pulse interaction with solid targets. The jet propagates with the velocity exceeding 400 km/s and transports the energy of a few kJ/cm2. The interaction of such a jet with an Ar and He gases at various pressures has been studied by using optical and X-ray diagnostics. Qualitative estimates and numerical simulations with a radiative hydrodynamic code explain a sequence of physical processes during the interaction. Experimental and numerical results show that, by changing ambient material, the working surface structure changes from an adiabatic outflow to a radiative cooling jet. The applications of this phenomenon to astrophysical conditions and the inertial confinement fusion are discussed.

Nearly Optimal Impulsive Controls for Reflected Wideband Width Process

Near optimal control problem for a wideband noise process with impulsive controls and constrained to a bounded region is considered. The method developed here will show that sequence of physical processes converges (weakly) to a reflected controlled diffusion process with impulses as the “approximating parameter” goes to zero. The cost functional of the wideband system will also converge to the corresponding cost functional of the limit problem. Due to the reflection at the boundary, pseudo path topology will be used in the weak convergence analysis.

The origin of the magnetic fields of the universe: The plasma astrophysics of the free energy of the universe

The interpretation of Faraday rotation measure maps of active galactic nuclei (AGNs) within galaxy clusters has revealed ordered or coherent regions, Lmag∼50−100 kpc (∼3×1023 cm), that are populated with large, ∼30 μG magnetic fields. The magnetic energy of these coherent regions is Lmag3(B2/8π)∼1059−60 ergs, and the total magnetic energy over the whole cluster (∼1 Mpc across) is expected to be even larger. Understanding the origin and role of these magnetic fields is a major challenge to plasma astrophysics. A sequence of physical processes that are responsible for the production, redistribution, and dissipation of these magnetic fields is proposed. These fields are associated with single AGNs within the cluster and therefore with all galaxies during their AGN (active galactic nucleus or quasar) phase, simply because only the central supermassive black holes (∼108M⊙) formed during the AGN phase have an accessible energy of formation, ∼1061 ergs, that can account for the magnetic field energy budget. An α–Ω dynamo process has been proposed that operates in an accretion disk around a black hole. The disk rotation naturally provides a large winding number, ∼1011 turns, sufficient to make both large gain and large flux. The helicity of the dynamo can be generated by the differential plume rotation derived from star-disk collisions. This helicity generation process has been demonstrated in the laboratory and the dynamo gain was simulated numerically. A liquid sodium analog of the dynamo is being built. Speculations are that the back reaction of the saturated dynamo will lead to the formation of a force-free magnetic helix, which will carry the energy and flux of the dynamo away from the accretion disk and redistribute the field within the clusters and galaxy walls. The magnetic reconnection of a small fraction of this energy logically is the source of the AGN (active galactic nucleus or quasar) luminosity, and the remainder of the field energy should then dominate the free energy of the present-day universe. The reconnection of this intergalactic field during a Hubble time is the only sufficient source of energy necessary to produce an extragalactic cosmic ray energy spectrum as observed in this galaxy, and at the same time allow this spectrum to escape to the galaxy voids faster than the GZK (blackbody radiation) loss.

Neutron detection with imaging plates Part I. Image storage and readout

The detection of neutrons with imaging plates is based on a sequence of physical processes, which are happening during the neutron exposure and the readout of the image information. These processes are investigated in detail starting with the neutron absorption and conversion to secondary radiation by various neutron converter materials and ending with the detection of the photostimulated luminescence, which is emitted during the readout. It is shown that these processes can be quantified by several key parameters, such as i.e. the neutron absorption cross section, the emitted secondary energy and the conversion efficiency of released secondary energy to storage centers in the storage phosphor. The resulting detector characteristics are described in the second part, namely, Neutron detection with imaging plates – part II: detector characteristics [Nucl. Instr. and Meth. A 424 (1999) 34–39].

A computer code modelling phenomenological uncertainties in a PSA

Abstract Three classes of expert opinion were introduced earlier. In this work, the so called Expert Judgement approach will be presented and applied. Probabilistic modelling of an event refers to the propagation of uncertainties through the sequence of physical processes that make up the event. It is an important concept of the Expert Judgement approach. A computer program has been developed in order to facilitate modelling and calculations. The program will be presented. An an example of the probabilistic modelling approach and the use of the program, a study of external cooling of the reactor pressure vessel will be presented.