On combustion noise related to chemical reactions

An inhomogeneous pressure wave equation has been derived for chemically reacting multicomponent gas mixtures to predict the acoustic field associated with combustion. Out of three source terms for the generation of combustion noise—namely, fluctuations in the heat release rate, in the momentum flow rate and in the viscous and diffusive working—the first is examined to relate this acoustic source strength to the concentration and temperature fluctuations through the chemical kinetics of reaction processes. The relationships between the spectral features of combustion noise and the statistical aspects of these fluctuations are obtained. The essential feature that combustion noise has substantial low-frequency components is explained by the dependence of the contribution of reaction fluctuations on the integral of the time correlation with respect to the correlation time.     

Anomalous saggins of Mössbauer effect probability at phase transitions

Anomalous saggings of the Mössbauer effect probability observed in various materials near phase transition points, as a function of temperature, are discussed. We show that in all the cases the saggings can be explained by a common reason — the appearance of the so-called heterophase fluctuations near the phase transitions.     

Temperature dependence of bound state spectra in field theory

We analyze the behaviour of kinks and semiclassical bound states at finite temperatures by applying quantum statistics to the fluctuations which determine the quantum dynamics of these states. We consider two theories in one space dimension — the ?⁴ theory with a dynamical symmetry breaking and the Gross-Neveu model. For the ?⁴ theory, the one-loop temperature corrections are obtained by using temperature-dependent Green function techniques. We show that the same result can be obtained by applying quantum statistics to the fluctuations around the kink. For the Gross-Neveu model, the temperature dependence of the bound states, which correspond to time-independent field configurations, is obtained. We show that for every bound state there exists a critical temperature at which this state breaks up into its constituents. This critical temperature increases with the number of constituents of the bound state.     

Semiclassical description of multipair transfer processes in heavy ion collisions with superfluid systems

Pair transfer processes involving a superfluid system are studied in terms of phase space distributions constructed in a product representation which blends both ordinary- and gauge-space degrees of freedom. The time evolution of these distributions is followed by solving a collection of classical equations of motion, the quantal fluctuations being accounted for by the sampling of all possible initial orientations of the (undetermined) intrinsic system in gauge space. The excitation of the pairing rotational degree of freedom — corresponding to a variation in the number of particles — is induced by a gauge-deformed ion-ion potential, as befits the superfluid character of the target. Different orientations leading to the same final mass transfer may produce (in the case of large pairing deformation) interference effects in the final population of the members of the pairing rotational band. We also discuss how this approach can be used to describe the effect of pair transfer modes on sub-barrier fusion processes.     

Large-Scale Two-Dimensional Quantum Fluctuations of Five-Dimensional and Four-Dimensional Space-Time Metrics

Large-scale two-dimensional quantum fluctuations of five-dimensional space-time metric are constructed and the effect of the fluctuations on the nested four-dimensional worlds is studied. In doing so, the fluctuations affect not all four-dimensional worlds but only a part of them. The energy-momentum tensor of four-dimensional space-time has a physical form both in the absence and in the presence of fluctuations; it means that the fluctuations can be realized by real matter. A spatial region occupied by the fluctuations constructed in this work can be infinitely large and the fluctuations can occur during a long period of time. Therefore, we refer to these fluctuations as large-scale fluctuations.     

Methods for investigating nuclear matter under the conditions characteristic of its transition to quark-gluon plasma

We briefly consider the properties of deep inelastic nuclear reactions on dense fluctuations of nuclear matter (fluctons). We discuss the properties of the fluctons, which can be many-quark bags or “drops” of quark-gluon plasma: the characteristic parameters of nuclear matter in a flucton— temperature and density close to the critical values for a phase transition. These values can be reached or exceeded if the flucton-flucton collision events are separated out. The separation method is discussed.     

On the feasibility of a neutron Hanbury Brown—Twiss experiment with gravitationally-induced phase shift

It is shown that a gravitational potential difference between the two components of a split fermion beam in a Mach—Zehnder type interferometer can influence the fermion second-order, one-point correlation function and hence the conditional probability of fermion arrivals at one output port. Manifestation of the effect requires use of two statistically-inequivalent input beams. The configuration is a particle analogue of the optical Hanbury Brown—Twiss experiments. Contrary to previous report of a signal-to-noise performance orders of magnitude higher than that characterising the cross-correlation of particle fluctuations in two beams, it is shown that both types of measurements are characterised by comparable signal-to-noise expressions. The implications for observation of neutron antibunching are discussed.     

Euclidean quantum gravity on a lattice

We construct a number of related euclidean lattice formulations of quantum gravity. The first version incorporates a path integral over discrete manifolds built out of four-cubes embedded in a higher dimensional flat hypercubic lattice. We show this expression is equal to a corresponding path integral in a local lattice field theory. The field theoretic path integral diverges and lacks a satisfactory vacuum state. This divergence can be interpreted as a consequence of a divergent phase space available for topological fluctuations in the four-manifolds of the original path integral. A modified version of the path integral over manifolds converges. We construct a Schrödinger equation and hamiltonian for the modified theory. The hamiltonian is self-adjoint, but as a result of the large phase space available for topological fluctuations, the hamiltonian's spectrum is probably not bounded from below. We show briefly how the flat enveloping space—time can be removed from most of the theories we present and how matter fields can be included.     

Sound fluctuations caused by internal waves in a shallow sea

Estimates are presented for the fluctuations of the parameters of low-frequency sound fields in shallow-water regions of the Barents Sea, in the presence of seasonal internal gravity waves. The objective of the experiments is to reveal the main mechanisms that govern the sound fluctuations and their statistical parameters on paths of moderate lengths (50–60 to 100–120 km). Another objective is to determine the features of the sound interaction with internal waves for the sound speed profile of the summer—autumn type for which the water stratification is most pronounced. As the probing signals, continuous tonal ones produced by bottommoored sources at the frequencies about 100 and 300 Hz are used along with the 1/3-octave noise signals with the central frequency 1000 Hz, which are generated by a source deployed from a vessel. For the signal reception, both fixed bottom-moored hydrophones and a vertical chain of hydrophones are used, the chain also being deployed from the vessel. The water temperature, the salinity, and the thermocline displacements are monitored with standard hydrographic sensors. The following main results are presented: the estimate of the degree of correlation between the sound fluctuations and the parameters of the water layer, the comparison of the fluctuations in the signal amplitude envelope with the data obtained in other regions, and the estimate of the statistical parameters of the signal amplitude fluctuations, including their dependence on the path length. One more result consists in the proof of the wave nature of the interaction of sound and internal waves, which manifests itself in a strong dependence of the sound interaction with internal waves of discrete frequencies on the frequency of the probing signal and on the angle at which these wave beams intersect. An attempt is made to explain the observed phenomena by the synchronism in the interacting sound and gravity waves. The data obtained can be used to analyze and compare the fluctuations of the sound fields in the ocean, especially in shallow-water regions.     

Stochastic Spacetime and Brownian Motion of Test Particles

The operational meaning of spacetime fluctuations is discussed. Classical spacetime geometry can be viewed as encoding the relations between the motions of test particles in the geometry. By analogy, quantum fluctuations of spacetime geometry can be interpreted in terms of the fluctuations of these motions. Thus, one can give meaning to spacetime fluctuations in terms of observables which describe the Brownian motion of test particles. We will first discuss some electromagnetic analogies, where quantum fluctuations of the electromagnetic field induce Brownian motion of test particles. We next discuss several explicit examples of Brownian motion caused by a fluctuating gravitational field. These examples include lightcone fluctuations, variations in the flight times of photons through the fluctuating geometry, and fluctuations in the expansion parameter given by a Langevin version of the Raychaudhuri equation. The fluctuations in this parameter lead to variations in the luminosity of sources. Other phenomena that can be linked to spacetime fluctuations are spectral line broadening and angular blurring of distant sources.     

Catalytic precursors: (Fe,Mn)3O4 and γ-(Fe,Mn)2O3

Iron-manganese oxide catalysts are known to influence the production of short chain hydrocarbons in the Fischer-Tropsch-synthesis process. XRD, XRF, gravity measurements and Mössbauer-effect spectroscopy has been used to study a catalytic precursor made by coprecipitation of iron and manganese oxides. The sample is characterized as a mixture of two compounds with the same iron to manganese ratio. The two compounds are cubic spinels with the same crystallographic parameters, however, one compound is a defect spinel while the other is not. In the Mössbauer studies the defect spinel shows superparamagnetic relaxation behavior—fluctuations of the magnetization vector along two opposite easy directions, while the non-defect spinel shows evidence of collective excitations—fluctuations of the magnetization vector in directions close to the easy direction. These properties are related to the particle sizes.     

介观物理系统中的噪声

描述了介观物理系统中噪声的研究现况. 对热噪声和散粒噪声的物理起源做了详细介绍，热噪声是系统的能态占据数发生涨落引起的，而散粒噪声源于载流子传输的微粒特性. 还介绍了研究噪声的主要理论——散射理论，并给出了其在马鞍形半导体量子线和铁磁/绝缘体/半导体双异质结两种介观系统中的应用，指出了噪声研究的实际物理意义. 关键词： 介观物理 热噪声 散粒噪声 散射理论     

Atmospheric IR propagation

The state-of-the-art of IR atmospheric propagation modelling — important to both scientific and practical applications of IR radiation—is reviewed, based mainly on experimental work performed at the FfO. The main improvements of transmission models rely on the results of measurements, analysis and modelling of aerosol and other atmospheric particle size distributions (0.15 μm ⪷ dia ⪷ 12 mm) over land and sea, performed in the context of long-range transmission experiments and lidar probings. Remaining problem areas will be identified and discussed, e.g. continuum absorption and fog window. The modelling of turbulence-induced fluctuations of amplitude and phase is of increasing interest as related to IR atmospheric windows and relevant laser lines. Recent experimental results on phase fluctuations are discussed, especially in relation to attempts to derive a better modelling of atmospheric microturbulence (C_n).     

Auto-and cross-correlation functions of a one-atom laser in a regime of strong coupling

The spectral properties of an incoherently pumped one-atom laser operating in a regime of strong coupling are studied. The spectrum of the field outgoing from the cavity, the spectrum of resonance fluorescence of an atom, and the spectrum of the atom—field cross-correlation function are numerically calculated. Relations between the parameters of the system for which spectral lines corresponding to eigenstates of the Jaynes—Cummings Hamiltonian are resolved are found. A method for determining the widths of resonances from the spectrum of the atom—field cross-correlation function is proposed, and a procedure for measuring this function using spectroscopy of intensity fluctuations is described.     

Fluctuating arrivals of short-range acoustic data

Geoacoustic inversion using fluctuating signal observations can be challenging. The origin of these fluctuations needs to be understood so the signals can be used appropriately. A set of experiments [Tang et al., Oceanogr. 20(4), 156-167 (2007)] was carried out in shallow water near the New Jersey shelf break in summer 2006. Significant fluctuations in the direct path and surface-reflected arrivals of short-range chirp transmissions (1.1-2.9 kHz) were observed on a vertical line array. This paper explains the origin of these signal fluctuations through analysis of the arrival amplitudes. It is shown that the strong thermocline combined with an oscillating source motion due to ocean surface waves results in the signal fluctuations.     

Switching Phenomena in a System with No Switches

It is widely believed that switching phenomena require switches, but this is actually not true. For an intriguing variety of switching phenomena in nature, the underlying complex system abruptly changes from one state to another in a highly discontinuous fashion. For example, financial market fluctuations are characterized by many abrupt switchings creating increasing trends (“bubble formation”) and decreasing trends (“financial collapse”). Such switching occurs on time scales ranging from macroscopic bubbles persisting for hundreds of days to microscopic bubbles persisting only for a few seconds. We analyze a database containing 13,991,275 German DAX Future transactions recorded with a time resolution of 10 msec. For comparison, a database providing 2,592,531 of all S&P500 daily closing prices is used. We ask whether these ubiquitous switching phenomena have quantifiable features independent of the time horizon studied. We find striking scale-free behavior of the volatility after each switching occurs. We interpret our findings as being consistent with time-dependent collective behavior of financial market participants. We test the possible universality of our result by performing a parallel analysis of fluctuations in transaction volume and time intervals between trades. We show that these financial market switching processes have properties similar to those of phase transitions. We suggest that the well-known catastrophic bubbles that occur on large time scales—such as the most recent financial crisis—are no outliers but single dramatic representatives caused by the switching between upward and downward trends on time scales varying over nine orders of magnitude from very large (≈10² days) down to very small (≈10 ms).     

The Height Fluctuations of an Off-Critical Dimer Model on the Square Grid

The dimer model on a planar bipartite graph can be viewed as a random surface measure. We study these fluctuations for a dimer model on the square grid with two different classes of weights and provide a condition for their equivalence. In the thermodynamic limit and scaling window, these height fluctuations are shown to be non-Gaussian.     

Self-turbulence in the motion of a free particle

A deterministic equation of the Hamilton-Jacobi type is proposed for a single particle:S _t+(1/2m)(?S)²+U{S}=0, whereU{S} is a certain operator onS, which has the sense of the potential of the self-generated field of a free particle. Examples are given of potentials that imply instability of uniform rectilinear motion of a free particle and yieldrandom fluctuations of its trajectory. Galilei-invariant turbulence-producing potentials can be constructed using a single universal parameter—Planck's constant. Despite the fact that the classical trajectory concept is retained, the mechanics of the particle then admits quantum-type effects: an uncertainty relation, de Broglie-type waves and their interference, discrete energy levels, and zero-point fluctuations.