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Journal articles on the topic 'Density fluctuation'

Author: Grafiati

Published: 21 April 2023

Last updated: 18 May 2024

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1

Artemenko, S. N. "Modification of charge density wave fluctuations by charge perturbations." Journal de Physique IV 12, no. 9 (November 2002): 77–78. http://dx.doi.org/10.1051/jp4:20020359.

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Spectral density of fluctuations of the CDW phase are calculated taking into account electric field induced by phase fluctuations. The approach based upon the fluctuation-dissipation theorem (FDT) combined with equations of linear response of the CDW conductor is used. Fluctuating electric field is found to suppress fluctuations of the phase, while fluctuations of the electric potential are sizeable. This suggests that transition from the CDW to the normal state (which is usually observed well below the mean-field transition temperature) may he provoked by fluctuations of the chemical potential, rather than by destruction of the CDW coherence between conducting chains due to phase fluctuations.

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2

Koga, Y. "Fluctuations in aqueous methanol, ethanol, and propan-1-ol: amplitude and wavelength of fluctuation." Canadian Journal of Chemistry 77, no. 12 (December 5, 1999): 2039–45. http://dx.doi.org/10.1139/v99-213.

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Density, heat capacity, and isentropic compressibility data for aqueous methanol, ethanol, and propan-1-ol by Benson's group were used to evaluate two kinds of fluctuations; mean-square fluctuation densities; and (mean-square) normalized fluctuations, respectively, in volume, entropy, and cross (entropy/volume) effect. The mean-square fluctuation densitiesprovide measures for the amplitude (intensity) of the fluctuation, while the normalized fluctuations contain information regarding the wavelength (extensity) of the fluctuation. Furthermore, their composition derivatives, the partial molar fluctuationsof alcohols were calculated. These quantities signify the effect of additional solute on the respective fluctuations. These data were interpreted in terms of mixing schemes learned earlier in this laboratory by using the data of excess partial molar enthalpy, entropy, and volume, and the respective alcohol-alcohol interaction functions, i.e., the composition derivatives of partial molar quantities. Key words: aqueous methanol, ethanol, and propan-1-ol;fluctuation density; normalized fluctuation; partial molar fluctuations of alcohol.

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3

Laberge, Gaetan J. H., and Rizwan U. Haq. ""Universality" of Gaussian orthogonal ensemble fluctuations: the two-body random ensemble and shell model spectra." Canadian Journal of Physics 68, no. 3 (March 1, 1990): 301–12. http://dx.doi.org/10.1139/p90-048.

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Starting from an appropriate decomposition of the level density into an average and fluctuating part, we studied the energy level fluctuations of an ensemble defined by two-body random Hamiltonians. A detailed analysis of several spectrally averaged fluctuation measures shows close agreement with the predictions of the Gaussian orthogonal ensemble (GOE). This confirms earlier indications that, except for noninteracting particles, fluctuation measures are insensitive to the rank of the interaction. Further, analysis of spectra obtained from realistic nuclear interactions agrees well with the GOE indicating that specific properties of the Hamiltonian have little or no influence on fluctuations. These results, therefore, strengthen our belief in the "universality" of GOE fluctuations.

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4

KOIKE, MASAFUMI, and JOE SATO. "EFFECTS OF MATTER DENSITY FLUCTUATION IN LONG BASELINE NEUTRINO OSCILLATION EXPERIMENTS." Modern Physics Letters A 14, no. 19 (June 21, 1999): 1297–302. http://dx.doi.org/10.1142/s0217732399001383.

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The effects of matter density fluctuation in long baseline neutrino oscillation experiments are studied. Effects of short wavelength fluctuations are irrelevant. Effects of long wavelength fluctuations must be checked on a case-by-case basis. As an example we checked the fluctuation effects and showed its irrelevance in a case of K2K experiments.

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5

Heidbrink, W. W. "Beam density fluctuation diagnostic." Review of Scientific Instruments 59, no. 9 (September 1988): 2008–11. http://dx.doi.org/10.1063/1.1140067.

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6

LAYEK, BISWANATH, SOMA SANYAL, and AJIT M. SRIVASTAVA. "BARYOGENESIS VIA DENSITY FLUCTUATIONS WITH A SECOND ORDER ELECTROWEAK PHASE TRANSITION." International Journal of Modern Physics A 18, no. 26 (October 20, 2003): 4851–68. http://dx.doi.org/10.1142/s0217751x03015799.

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We consider the presence of cosmic string induced density fluctuations in the universe at temperatures below the electroweak phase transition temperature. Resulting temperature fluctuations can restore the electroweak symmetry locally, depending on the amplitude of fluctuations and the background temperature. The symmetry will be spontaneously broken again in a given fluctuation region as the temperature drops there (for fluctuations with length scales smaller than the horizon), resulting in the production of baryon asymmetry. The time scale of the transition will be governed by the wavelength of fluctuation and, hence, can be much smaller than the Hubble time. This leads to strong enhancement in the production of baryon asymmetry for a second order electroweak phase transition as compared to the case when transition happens due to the cooling of the universe via expansion. For a two-Higgs extension of the Standard Model (with appropriate CP violation), we show that one can get the required baryon to entropy ratio if fluctuations propagate without getting significantly damped. If fluctuations are damped rapidly, then a volume factor suppresses the baryon production. Still, the short scale of the fluctuation leads to enhancement of the baryon to entropy ratio by at least 3–4 orders of magnitude compared to the conventional case of second order transition where the cooling happens due to expansion of the universe.

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7

Singh, Rajeev. "Quantum fluctuations of baryon number density." Journal of Physics: Conference Series 2105, no. 1 (November 1, 2021): 012006. http://dx.doi.org/10.1088/1742-6596/2105/1/012006.

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Abstract Quantum fluctuation expression of the baryon number for a subsystem consisting of hot relativistic spin− 1 2 particles are derived. These fluctuations seems to diverge in the limit where system size goes to zero. For a broad range of thermodynamic parameters numerical solutions are obtained which might be helpful to interpret the heavy-ion experimental data.

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8

Bai, Yujoung, Chang-Mo Ryu, Chul Koo Kim, Sang Koo You, and Kyun Nahm. "Spin-density fluctuation in paramagnets." Physical Review B 54, no. 1 (July 1, 1996): 33–36. http://dx.doi.org/10.1103/physrevb.54.33.

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9

Azzazy, M., D. Modarress, and T. Hoeft. "High-sensitivity density fluctuation detector." Journal of Physics E: Scientific Instruments 20, no. 4 (April 1987): 428–31. http://dx.doi.org/10.1088/0022-3735/20/4/017.

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10

MOSTOVOY, MAXIM, and JASPER KNOESTER. "INSTANTON CALCULATION OF THE DENSITY OF STATES OF DISORDERED PEIERLS CHAINS." International Journal of Modern Physics B 13, no. 13 (May 30, 1999): 1601–18. http://dx.doi.org/10.1142/s0217979299001594.

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We use the optimal fluctuation method to find the density of electron states inside the pseudogap in disordered Peierls chains. The electrons are described by the one-dimensional Dirac Hamiltonian with randomly varying mass (the Fluctuating Gap Model). We establish a relation between the disorder average in this model and the quantum-mechanical average for a certain double-well problem. We show that the optimal disorder fluctuation, which has the form of a soliton–antisoliton pair, corresponds to the instanton trajectory in the double-well problem. We use the instanton method developed for the double-well problem to find the contribution to the density of states from disorder realizations close to the optimal fluctuation.

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11

Gan, Cai Zhao, and Hong Bin Huang. "Relative Density Clustering Algorithm Based on Density Fluctuation." Journal of Physics: Conference Series 1087 (September 2018): 022010. http://dx.doi.org/10.1088/1742-6596/1087/2/022010.

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12

Luo, Hongmei, Yi Zhou, Lijie Pei, Hao Xu, Dongqi Fan, Yida Tang, Jianing Gao, and Jiachen Liu. "Method for analysing of wind power wave nature based on kernel density estimation." Journal of Physics: Conference Series 2728, no. 1 (March 1, 2024): 012031. http://dx.doi.org/10.1088/1742-6596/2728/1/012031.

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Abstract It is beneficial for improving the accuracy of wind power output prediction by analysing and mastering the inherent laws of the fluctuation characteristics of wind power output, guiding the power grid dispatching department to reasonably arrange power generation plans, and improving the economic efficiency of system operation. In order to characterize the probability density distribution of wind power output fluctuation, two adaptive bandwidth kernel density estimation models are established by correcting the fixed bandwidth obtained from the empirical method and unbiased cross-validation method respectively, and then the two models are combined and optimized, and ultimately, the probability density distribution model of wind power output fluctuation based on Hybrid Adaptive Kernel Density Estimation (HAKDE) is established. A variety of probability density distribution models are used to fit the wind power output fluctuations at different spatial and temporal scales in a province in North China, and the example results show that the hybrid adaptive kernel density estimation model has the best fitting effect, thus verifying the effectiveness of the hybrid adaptive kernel density estimation model.

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13

Mehay, T. P., R. Warmbier, and A. Quandt. "Investigation of density fluctuations in graphene using the fluctuation-dissipation relations." Computational Condensed Matter 13 (December 2017): 1–5. http://dx.doi.org/10.1016/j.cocom.2017.08.008.

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14

Mingesz, R., G. Vadai, and Z. Gingl. "Power Spectral Density Estimation for Wireless Fluctuation Enhanced Gas Sensor Nodes." Fluctuation and Noise Letters 13, no. 02 (June 2014): 1450011. http://dx.doi.org/10.1142/s0219477514500114.

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Fluctuation enhanced sensing (FES) is a promising method to improve the selectivity and sensitivity of semiconductor and nanotechnology gas sensors. Most measurement setups include high cost signal conditioning and data acquisition units as well as intensive data processing. However, there are attempts to reduce the cost and energy consumption of the hardware and to find efficient processing methods for low cost wireless solutions. In this paper, we propose highly efficient signal processing methods to analyze the power spectral density of fluctuations. These support the development of ultra-low-power intelligent fluctuation enhanced wireless sensor nodes while several further applications are also possible.

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15

Lee, J. S., and L. P. Lee. "Ventilatory changes of pulmonary capillary blood volume assessed by arterial density." Journal of Applied Physiology 61, no. 5 (November 1, 1986): 1724–31. http://dx.doi.org/10.1152/jappl.1986.61.5.1724.

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By use of an improved density measuring system, we found that the gravimetric density of arterial blood of dogs fluctuates at the same frequency as the spontaneous or mechanical ventilation. Similar density fluctuations were observed in the blood leaving isolated, perfused lobes of dogs that were ventilated cyclicly. Employing an analysis that balanced the erythrocyte and plasma flows through distensible capillaries containing blood with a tube hematocrit lower than the hematocrit in large blood vessels, we derived a relationship to estimate from the density fluctuation the change in pulmonary capillary blood volume (Vc). For mechanical ventilation, the maximum change in density over one ventilation cycle increased from 0.084 +/- 0.01 to 0.47 +/- 0.05 (SE) g/l as the frequency decreased from 29 to 6 cycles/min. These density changes were estimated to be the result of an 1–16% change in Vc. A larger tidal volume for the mechanical ventilation led to a larger density fluctuation. The maximum density change of spontaneous respiration of 6 cycles/min was one-sixth of the mechanical case, indicating a much smaller change in Vc during spontaneous respiration. When the airway flow resistance was increased for spontaneous respiration, larger density fluctuations were observed.

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16

SURESH, P. K. "THERMAL SQUEEZING AND DENSITY FLUCTUATIONS IN SEMICLASSICAL THEORY OF GRAVITY." Modern Physics Letters A 16, no. 11 (April 10, 2001): 707–17. http://dx.doi.org/10.1142/s0217732301003802.

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A thermal squeezed state representation is constructed for each mode of a quantized scalar field in a spatially homogeneous and flat Robertson–Walker metric and the validity of semiclassical Einstein equation by analyzing the density fluctuation is examined. The density fluctuation in thermal squeezed state is very large and therefore the semiclassical theory may not be valid for squeezing parameter more than unity, however the theory holds when the associated squeezing parameter is much less than the unity. Further noted that the semiclassical theory is consistent in thermal coherent state formalism. The present study can account for the density fluctuations due to the thermal and quantum effects in semiclassical theory of gravity.

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17

Romero, Charles E., Massimo Gaspari, Gerrit Schellenberger, Tanay Bhandarkar, Mark Devlin, Simon R. Dicker, William Forman, et al. "Inferences from Surface Brightness Fluctuations of Zwicky 3146 via the Sunyaev–Zel’dovich Effect and X-Ray Observations." Astrophysical Journal 951, no. 1 (July 1, 2023): 41. http://dx.doi.org/10.3847/1538-4357/acd3f0.

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Abstract The galaxy cluster Zwicky 3146 is a sloshing cool-core cluster at z = 0.291 that in Sunyaev–Zel’dovich (SZ) imaging does not appear to exhibit significant pressure substructure in the intracluster medium. We perform a surface brightness fluctuation analysis via Fourier amplitude spectra on SZ (MUSTANG-2) and X-ray (XMM-Newton) images of this cluster. These surface brightness fluctuations can be deprojected to infer pressure and density fluctuations from the SZ and X-ray data, respectively. In the central region (Ring 1, r < 100″ = 440 kpc, in our analysis), we find fluctuation spectra that suggest injection scales around 200 kpc (∼140 kpc from pressure fluctuations and ∼250 kpc from density fluctuations). When comparing the pressure and density fluctuations in the central region, we observe a change in the effective thermodynamic state from large to small scales, from isobaric (likely due to the slow sloshing) to adiabatic (due to more vigorous motions). By leveraging scalings from hydrodynamical simulations, we find an average 3D Mach number ≈0.5. We further compare our results to other studies of Zwicky 3146 and, more broadly, to other studies of fluctuations in other clusters.

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18

Sobry, Roger, and Salvino Ciccariello. "Background subtraction and moments of the microscopic density fluctuation." Journal of Applied Crystallography 35, no. 2 (March 22, 2002): 220–27. http://dx.doi.org/10.1107/s0021889802000584.

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Some models of microscopic density fluctuations are numerically analysed in order to study the behaviour of the related background contribution. The results suggest that this contribution can be described by an algebraic expression depending on only the moments of the microscopic density fluctuation. In this way, the parameter values, determined by a best-fit procedure to account for background contributions in the case of real samples, acquire a definite physical meaning. The procedure is applied to the small-angle X-ray intensities of a polymer sample analysed at different temperatures and yields satisfactory results.

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19

Shebalin, John V., and David Montgomery. "Turbulent magnetohydrodynamic density fluctuations." Journal of Plasma Physics 39, no. 2 (April 1988): 339–67. http://dx.doi.org/10.1017/s0022377800013076.

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A spectral-method numerical code is used to compute mass-density fluctuation spectra in turbulent magnetofluids. The computations are used to test and extend a recent analytical theory of density variations in slightly compressible magnetofluids given by Montgomery, Brown and Matthaeus, and used by them to infer inertial-range density-fluctuation spectra for the nearby interstellar medium and solar wind. A local equation of state is assumed, relating density to pressure. Constant, scalar resistivities and viscosities are used. In the limit of low Mach numbers and high mechanical-to-magnetic pressure ratios, the fit of the computations to the analytical theory is seen to be close.

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20

SCHMID, FRIEDERIKE. "FLUCTUATIONS IN LIPID BILAYERS: ARE THEY UNDERSTOOD?" Biophysical Reviews and Letters 08, no. 01n02 (June 2013): 1–20. http://dx.doi.org/10.1142/s1793048012300113.

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We review recent computer simulation studies of undulating lipid bilayers. Theoretical interpretations of such fluctuating membranes are most commonly based on generalized Helfrich-type elastic models, with additional contributions of local "protrusions" and/or density fluctuations. Such models provide an excellent basis for describing the fluctuations of tensionless bilayers in the fluid Lαphase at a quantitative level.However, this description is found to fail for membranes in the gel phase and for membranes subject to high tensions. The fluctuations of tilted gel membranes (Lβ′phase) show a signature of the modulated ripple structure Pβ′, which is a nearby phase observed in the pretransition regime between the Lαand Lβ′state. This complicates a quantitative analysis on mesoscopic length scales. In the case of fluid membranes under tension, the large-wavelength fluctuation modes are found to be significantly softer than predicted by theory.In the latter context, we also address the general problem of the relation between frame tension and the fluctuation tension, which has been discussed somewhat controversially in recent years. Simulations of very simple model membranes with fixed area show that the fluctuations should be controlled by the frame tension, and not by the internal tension.

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21

Lacombe, C., J. L. Steinberg, C. C. Harvey, D. Hubert, A. Mangeney, and M. Moncuquet. "Density fluctuations measured by ISEE 1-2 in the Earth's magnetosheath and the resultant scattering of radio waves." Annales Geophysicae 15, no. 4 (April 30, 1997): 387–96. http://dx.doi.org/10.1007/s00585-997-0387-5.

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Abstract. Radio waves undergo angular scattering when they propagate through a plasma with fluctuating density. We show how the angular scattering coefficient can be calculated as a function of the frequency spectrum of the local density fluctuations. In the Earth's magnetosheath, the ISEE 1-2 propagation experiment measured the spectral power of the density fluctuations for periods in the range 300 to 1 s, which produce most of the scattering. The resultant local angular scattering coefficient can then be calculated for the first time with realistic density fluctuation spectra, which are neither Gaussian nor power laws. We present results on the variation of the local angular scattering coefficient during two crossings of the dayside magnetosheath, from the quasi-perpendicular bow shock to the magnetopause. For a radio wave at twice the local electron plasma frequency, the scattering coefficient in the major part of the magnetosheath is b(2fp) ≃ 0.5 – 4 × 10–9 rad2/m. The scattering coefficient is about ten times stronger in a thin sheet (0.1 to1RE) just downstream of the shock ramp, and close to the magnetopause.

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22

Nakamura, S. i., and A. Hosoya. "Density Fluctuation in Extended Inflationary Universe." Progress of Theoretical Physics 87, no. 2 (February 1, 1992): 401–7. http://dx.doi.org/10.1143/ptp/87.2.401.

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23

Montgomery, D., M. R. Brown, and W. H. Matthaeus. "Density fluctuation spectra in magnetohydrodynamic turbulence." Journal of Geophysical Research 92, A1 (1987): 282. http://dx.doi.org/10.1029/ja092ia01p00282.

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24

Shaikh, Dastgeer. "Density fluctuation spectrum in whistler turbulence." Physics Letters A 374, no. 25 (May 2010): 2551–54. http://dx.doi.org/10.1016/j.physleta.2010.04.024.

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25

Salopek, D. S., J. R. Bond, and J. M. Bardeen. "Designing density fluctuation spectra in inflation." Physical Review D 40, no. 6 (September 15, 1989): 1753–88. http://dx.doi.org/10.1103/physrevd.40.1753.

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26

Furche, Filipp, and Troy Van Voorhis. "Fluctuation-dissipation theorem density-functional theory." Journal of Chemical Physics 122, no. 16 (April 22, 2005): 164106. http://dx.doi.org/10.1063/1.1884112.

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27

PANDA, J., and R. G. SEASHOLTZ. "Experimental investigation of density fluctuations in high-speed jets and correlation with generated noise." Journal of Fluid Mechanics 450 (January 9, 2002): 97–130. http://dx.doi.org/10.1017/s002211200100622x.

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The air density fluctuations in the plumes of fully expanded, unheated free jets were investigated experimentally using a Rayleigh-scattering-based technique. The point measuring technique used a continuous-wave laser, fibre-optic transmission and photon counting electronics. The radial and centreline profiles of time-averaged density and root-mean-square density fluctuation provided a comparative description of jet growth. To measure density fluctuation spectra a two-photomultiplier-tube (PMT) technique was used. Cross-correlation between the two PMT signals significantly reduced the electronic shot noise contribution. The density fluctuation spectra were found to be remarkably similar for all Mach number jets. A detailed survey in fully expanded Mach 0.95, 1.4 and 1.8 jets further confirmed that the distribution of various Strouhal frequency fluctuations remained similar, except for a spatial stretching with increased Mach number. In spite of this similarity in flow fluctuations the noise sources in these three jets were found to be significantly different. Spark schlieren photographs and near-field microphone measurements confirmed that Mach wave radiation was present in the Mach 1.8 jet, and was absent in the Mach 0.95 jet. Direct correlation measurement between the flow density fluctuation (cause) and far-field sound pressure fluctuation (effect) shed further light on the sound generation process. For this purpose a microphone was kept fixed at a far-field point, mostly at a distance of 50 diameters and 30° to the flow direction, and the laser probe volume was moved from point to point in the flow. In the Mach 1.8 jet, where the convective velocity of Kelvin–Helmholtz instability waves exceeded the ambient sound speed, significant correlation was measured from the peripheral shear layer, while in the Mach 0.95 jet, where the instability waves had subsonic convective speed, no correlation could be measured. Although the same instability waves were present in both Mach 1.8 and 0.95 jets, the peripheral shear layer of the former was found to be an obvious noise source, while that of the latter was not. Further correlation studies along the jet centreline showed that behaviour in the region downstream of the potential core was similar in all Mach number jets tested, 0:6[les ]M[les ]1:8. Good correlation at low Strouhal frequencies was measured from this region, which started from downstream of the potential core and extended many diameters from there.

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28

Lin, L., W. X. Ding, D. L. Brower, W. F. Bergerson, and T. F. Yates. "Differential interferometry for measurement of density fluctuations and fluctuation-induced transport (invited)." Review of Scientific Instruments 81, no. 10 (October 2010): 10D509. http://dx.doi.org/10.1063/1.3464480.

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29

Hugon, Christophe, and Vladimir Kulikovskiy. "Zero-Point Energy Density at the Origin of the Vacuum Permittivity and Photon Propagation Time Fluctuation." Physics 6, no. 1 (January 10, 2024): 94–107. http://dx.doi.org/10.3390/physics6010007.

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We give a vacuum description with zero-point density for virtual fluctuations. One of the goals is to explain the origin of the vacuum permittivity and permeability and to calculate their values. In particular, we improve on existing calculations by avoiding assumptions on the volume occupied by virtual fluctuations. We propose testing of the models that assume a finite lifetime of virtual fluctuation. If during its propagation, the photon is stochastically trapped and released by virtual pairs, the propagation velocity may fluctuate. The propagation time fluctuation is estimated for several existing models. The obtained values are measurable with available technologies involving ultra-short laser pulses, and some of the models are already in conflict with the existing astronomical observations. The phase velocity is not affected significantly, which is consistent with the interferometric measurements.

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30

Gruenwald, Ruth, and Sueli M. Viegas. "Temperature Fluctuations in PN." Symposium - International Astronomical Union 155 (1993): 188. http://dx.doi.org/10.1017/s0074180900170500.

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For planetary nebulae, empirical abundances can be obtained from the observed emission-lines as long as the electron density, the electron temperature, and the ionization corrections factor are determined. However, due to temperature fluctuations in the emitting gas, the evaluation of the temperature from the observational data is strongly dependent on the method used. The temperature fluctuation is usually characterized by the mean square temperature fluctuation, t2 (Peimbert and Costero, 1969 — PC).

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31

Miyashita, A., S. Ohshima, R. Matoike, F. Kin, S. Kobayashi, S. Kado, T. Minami, et al. "Non-uniformity of fluctuation characteristics inside an edge magnetic island in Heliotron J." Plasma Physics and Controlled Fusion 66, no. 7 (May 17, 2024): 075008. http://dx.doi.org/10.1088/1361-6587/ad49d5.

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Abstract Non-uniform fluctuation characteristics are observed within an edge magnetic island in Heliotron J. The island possesses a long connection length comparable to the confined region. These fluctuations are measured using a Langmuir probe. The island’s presence is confirmed through the plasma response, observed in the modulation amplitude of electron temperature and its phase delay relative to the heat source in a heat modulation experiment. Within the island, the electron density is notably high, accompanied by distinct profiles of electron temperature and electric field, likely attributable to the magnetic island. Contrary to expectations, density fluctuations within the edge magnetic island are not locally minimized, despite the reduced gradient of the profile within the island. Statistical analysis shows a suppression of intermittent transport inside the island, while intermittent fluctuations increase towards the exterior. A further analysis to segregate turbulence-driving and spreading factors reveals that both turbulence-driven and spreading contributions are comparably significant inside the island. Additionally, the non-uniform turbulence results in a spatially structured fluctuation-driven particle flux. Overall, the experimental findings indicate that fluctuation characteristics exhibit notable non-uniformity both inside and near the island. This non-uniformity potentially complicates heat transport and may lead to three-dimensional, asymmetric transport within and at the periphery of the islands.

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32

Allen, Micheal S., and Leandro E. Miranda. "Quasi-cycles in crappie populations are forced by interactions among population characteristics and environment." Canadian Journal of Fisheries and Aquatic Sciences 58, no. 3 (March 1, 2001): 594–601. http://dx.doi.org/10.1139/f01-020.

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Crappie (Pomoxis spp.) populations have been characterized as cyclic, with strong year-classes recurring at 2- to 4-year intervals. We evaluated the potential for cyclic trends in crappie populations using a population model that included a density-dependent stock recruitment function and random environmental variation. Slow, medium, and fast growth were simulated over 100 years. The model predicted highly variable recruitment that was strongly influenced by environmental fluctuation at low and intermediate stock densities. At high stock density, recruitment was low, even if environmental conditions were favorable. Significant quasi-cycles occurred, but they were not sustained throughout the time series due to random environmental fluctuation. Quasi-cycles occurred because intermediate stock density and favorable environmental conditions occasionally combined to produce a very strong year-class that greatly increased stock density in the following 13 years and produced low recruitment, even if environmental conditions were favorable. Empirical data from 32 years of sampling age-0 crappies at Ross Barnett Reservoir showed trends similar to the simulated fluctuations. We conclude that crappie populations likely do not exhibit true cycles but may show quasi-cycles as a result of the interaction between random fluctuations in environment and density-dependent mechanisms. The frequency of such quasi-cycles may be enhanced by rapid growth and high exploitation.

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33

Padmaja, S., M. Ramakrishna Nanchara Rao, P. V. Datta Prasad, and V. G. K. M. Pisipati. "Studies of the Orientational Disorder at the Isotropic to Smectic-F Interface." Zeitschrift für Naturforschung A 60, no. 4 (April 1, 2005): 296–300. http://dx.doi.org/10.1515/zna-2005-0414.

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Abstract Density studies on the isotropic to smectic-F transition in higher homologues of N-(p-nalkoxybenzylidene)- p-n-decylanilines (nO.10) mesomorphic compounds with n = 13, 14 and 15 and corresponding studies on thermal expansion coefficient maxima confirm the first order nature of this transition. The density shows strong pretransitional fluctuations, which are estimated by αeff in the vicinity of the mesomorphic fluctuation dominated non-linear region (FDNLR) of this phase transition. The growth of the density fluctuations across this transition is discussed in the light of data on the same transition in other compounds.

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34

Mali, P., S. Sarkar, S. Ghosh, A. Mukhopadhyay, and G. Singh. "Multifractal detrended fluctuation analysis of particle density fluctuations in high-energy nuclear collisions." Physica A: Statistical Mechanics and its Applications 424 (April 2015): 25–33. http://dx.doi.org/10.1016/j.physa.2014.12.037.

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35

WU, Donggui, Guanghai HU, S. ZOLETNIK, Guosheng XU, Siye DING, Jianbin LIU, Linming SHAO, et al. "Plasma edge density fluctuation measurements via lithium beam emission spectroscopy on EAST." Plasma Science and Technology 24, no. 5 (April 19, 2022): 055102. http://dx.doi.org/10.1088/2058-6272/ac4d1e.

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Abstract Accurate and stable measurements of edge density fluctuation with high spatio-temporal resolution have been achieved by the lithium beam emission spectroscopy (Li-BES) diagnostic on experimental and advanced superconducting tokamak (EAST). The new narrower band interference filter exhibits good ability to suppress background emission signal even under strong lithium coating of the tokamak. The raw data measured by channels at different spatial locations in avalanche photo diode camera with high chopping frequency show good consistency. Based on the detected experimental data, detailed information of density profile and fluctuation structures is obtained. A clear edge coherent mode in the auto-power spectrum is observed in pedestal region, which is regarded as the dominant factor for the strong pedestal density fluctuation amplitude. The cross-power spectrum analysis further excludes the additional effects of common-mode noises and non-local perturbation, demonstrating that the detected fluctuation is only caused by local density fluctuation. The normalized radial and poloidal wave-number spectra can specify the quantitative changes of radial wavenumber (k r) and poloidal wavenumber (k θ) during the pedestal density fluctuation phase. This new Li-BES system, which can provide more accurate experimental data, allows further studies of edge density fluctuation and complex transport process on EAST.

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36

Seo, Min-Seok. "Black hole production, eternal inflation, and information in quasi-de Sitter space." Journal of Cosmology and Astroparticle Physics 2022, no. 11 (November 1, 2022): 005. http://dx.doi.org/10.1088/1475-7516/2022/11/005.

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Abstract When the slow-roll parameter ϵ H is smaller than H 2/M Pl 2, the quantum fluctuations of the inflaton after the horizon crossing are large enough to realize eternal inflation. Whereas they do not generate a sufficient amount of density fluctuation of the inflaton to produce the black hole in quasi-de Sitter space, they can also generate the sizeable density fluctuation of the radiation when the number of degrees of freedom increases rapidly in time, as predicted by the distance conjecture. We argue that the condition that the density fluctuation of the radiation is not large enough to produce the black hole until the end of inflation is equivalent to the no eternal inflation condition. When the radiation emitted by the horizon does not produce the black hole, even if the number of degrees of freedom increases in time, the information paradox does not arise for ϵ H larger than 10-7 (H 2/M Pl 2) and time scale shorter than 104 (M Pl/H 2). Regardless of the presence of the information paradox, a static observer cannot retrieve a sufficient amount of information, which is consistent with the complementarity.

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37

Koshy, R., T. Desai, P. Keblinski, J. Hooper, and K. S. Schweizer. "Density fluctuation correlation length in polymer fluids." Journal of Chemical Physics 119, no. 14 (October 8, 2003): 7599–603. http://dx.doi.org/10.1063/1.1606673.

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38

Basse, N. P. "A Study of Multiscale Density Fluctuation Measurements." IEEE Transactions on Plasma Science 36, no. 2 (April 2008): 458–61. http://dx.doi.org/10.1109/tps.2008.917519.

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39

Beben, Janusz, and Yuri Suchorski. "Surface diffusion by adsorbate density fluctuation measurements." Progress in Surface Science 74, no. 1-8 (December 2003): 3–24. http://dx.doi.org/10.1016/j.progsurf.2003.08.002.

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40

Banerjee, N., and S. Mallik. "Density fluctuation in the de Sitter universe." Annals of Physics 205, no. 1 (January 1991): 29–48. http://dx.doi.org/10.1016/0003-4916(91)90236-2.

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41

Doyle, E. J., T. Lehecka, N. C. Luhmann, W. A. Peebles, R. Philipona, K. H. Burrell, R. J. Groebner, H. Matsumoto, and T. H. Osborne. "Reflectometer density fluctuation measurements on DIII‐D." Review of Scientific Instruments 61, no. 10 (October 1990): 3016–18. http://dx.doi.org/10.1063/1.1141973.

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42

McKee, G. R., R. J. Fonck, D. K. Gupta, D. J. Schlossberg, M. W. Shafer, C. Holland, and G. Tynan. "Turbulence velocimetry of density fluctuation imaging data." Review of Scientific Instruments 75, no. 10 (October 2004): 3490–92. http://dx.doi.org/10.1063/1.1790043.

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43

Fang, Li. "Electron Density Fluctuation in a Dusty Plasma." Chinese Physics Letters 19, no. 2 (February 2002): 214–16. http://dx.doi.org/10.1088/0256-307x/19/2/323.

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44

Klimin, Serghei, Jacques Tempere, and Hadrien Kurkjian. "Low-Lying Collective Excitations of Superconductors and Charged Superfluids." Condensed Matter 8, no. 2 (May 3, 2023): 42. http://dx.doi.org/10.3390/condmat8020042.

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We investigate theoretically the momentum-dependent frequency and damping of low-lying collective excitations of superconductors and charged superfluids in the BCS–BEC crossover regime. The study is based on the Gaussian pair-and-density fluctuation method for the propagator of Gaussian fluctuations of the pair and density fields. Eigenfrequencies and damping rates are determined in a mutually consistent nonperturbative way as complex poles of the fluctuation propagator. Particular attention is paid to new features with respect to preceding theoretical studies, which were devoted to collective excitations of superconductors in the far BCS regime. We find that at a sufficiently strong coupling, new branches of collective excitations appear, which manifest different behavior as functions of the momentum and the temperature.

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45

Spangler, S. R. "The small amplitude of density turbulence in the inner solar wind." Nonlinear Processes in Geophysics 10, no. 1/2 (April 30, 2003): 113–20. http://dx.doi.org/10.5194/npg-10-113-2003.

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Abstract. Very Long Baseline Interferometer (VLBI) observations were made of radio sources close to the Sun, whose lines of sight pass through the inner solar wind (impact parameters 16-26 RE). Power spectra were analyzed of the interferometer phase fluctuations due to the solar wind plasma. These power spectra provide information on the level of plasma density fluctuations on spatial scales of roughly one hundred to several thousand kilometers. By specifying an outer scale to the turbulence spectrum, we can estimate the root-mean-square (rms) amplitude of the density fluctuations. The data indicate that the rms fluctuation in density is only about 10% of the mean density. This value is low, and consistent with extrapolated estimates from more distant parts of the solar wind. Physical speculations based on this result are presented.

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46

Wijesinghe, H. S., C. S. Tan, and E. E. Covert. "Aerodynamic Response of Turbomachinery Blade Rows to Convecting Density Wakes." Journal of Turbomachinery 124, no. 2 (April 1, 2002): 269–74. http://dx.doi.org/10.1115/1.1311287.

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A two-dimensional computational study was conducted to characterize the density wake induced force and moment fluctuations on a compressor blade row. The flow simulations indicate unsteady blade excitation generated by: (1) density wake fluid directed to the blade suction surface, (2) axial deflection of the blade passage shock wave position and (3) formation of a separation bubble on the blade suction surface. The blade force and moment fluctuation amplitudes are found to scale with the nondimensional density wake width w/c and a nondimensional density parameter ρ*.

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47

Ota, Atsuhisa. "Fluctuation-dissipation relation in cosmic microwave background." Journal of Cosmology and Astroparticle Physics 2024, no. 05 (May 1, 2024): 062. http://dx.doi.org/10.1088/1475-7516/2024/05/062.

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Abstract We study the fluctuation-dissipation relation for sound waves in the cosmic microwave background (CMB), employing effective field theory (EFT) for fluctuating hydrodynamics. Treating sound waves as the linear response to thermal radiation, we establish the fluctuation-dissipation relation within a cosmological framework. While dissipation is elucidated in established linear cosmological perturbation theory, the standard Boltzmann theory overlooks the associated noise, possibly contributing to inconsistencies in Lambda Cold Dark Matter (ΛCDM) cosmology. This paper employs EFT for fluctuating hydrodynamics in cosmological perturbation theory, deriving sound wave noise. Notably, the long-time limit of the noise spectrum is independent of viscosity details, resembling a Brownian motion bounded in a harmonic potential. The net energy transfer between the sound wave system and the radiation environment reaches a balance within Hubble time, suggesting the thermal equilibrium of the sound waves themselves. The induced density power spectrum is characterized as white noise dependent on the inverse of the entropy density, which is negligibly small on the CMB scale. The energy density of the entire sound wave system scales as a -4, akin to radiation. While the numerical factor is not determined in the present calculation, the back reaction of the sound wave system to the background radiation may not be negligible, serving as a potential source for various fitting issues in ΛCDM cosmology.

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48

Taye, Jyotismita, Jyotirmoy Barman, Bimlesh Kumar, and Giuseppe Oliveto. "Deciphering Morphological Changes in a Sinuous River System by Higher-Order Velocity Moments." Water 12, no. 3 (March 11, 2020): 772. http://dx.doi.org/10.3390/w12030772.

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Bank erosion in a sinuous alluvial channel is a continuous phenomenon resulting in bank instability and migration of sediment. In this study, flume experiments were conducted in a sinuous channel to investigate its morphological changes and hydrodynamics. High-order velocity fluctuation moments are analyzed at outer and inner banks to explain the morphological variation in a sinuous river channel. The variance of streamwise velocity fluctuations on both banks of the sinuous channel follows a logarithmic law from a particular depth. In the outer bend region, the magnitude of velocity fluctuation moment is significant, indicating erosion. The trend of velocity fluctuation at higher even-order moments is similar to the variance of streamwise velocity fluctuations where the outer bend magnitude is greater than the inner bend. The premultiplied probability density functions (PDFs) and the flatness factor show greater magnitude in the outer bend of the channel as compared to the inner bend.

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Buser, Othmar, and Perry Bartelt. "Dispersive pressure and density variations in snow avalanches." Journal of Glaciology 57, no. 205 (2011): 857–60. http://dx.doi.org/10.3189/002214311798043870.

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AbstractSnow avalanches possess two types of kinetic energy: the kinetic energy associated with the mean velocity in the downhill direction and the kinetic energy associated with individual particle velocities that vary from the mean. The mean kinetic energy is directional; the kinetic energy associated with the velocity fluctuations is non-directional in the sense that it is connected to random particle movements. However, the rigid, basal boundary directs the random fluctuation energy into the avalanche. Thus, the random energy flux is converted to free mechanical energy which lifts and dilates the avalanche flow mass, changing the flow density and increasing the normal (dispersive) pressure and, as a consequence, changing the flow resistance. In this paper we derive macroscopic relations that link the production of the random kinetic energy to the perpendicular acceleration of the avalanche’s center of mass. We show that a single burst of fluctuation energy will produce pressures that oscillate around the hydrostatic pressure. Because we do not include a damping process, the oscillations of the center of mass remain, even if the production of random kinetic energy stops. We formulate relationships that can be used within the framework of depth-averaged mass and momentum equations that are often used to simulate snow avalanches in realistic terrain.

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50

Li, Hongxun, Yudong Li, Li Chen, and Xianghong Yao. "Tunable Spatial Resolution Focused Laser Differential Interferometer for Density Fluctuation Measurement." Applied Sciences 13, no. 5 (March 3, 2023): 3253. http://dx.doi.org/10.3390/app13053253.

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We first propose and demonstrate a novel approach for achieving a focused laser differential interferometer (FLDI) system with tunable spatial resolution. The spatial resolution of the FLDI can be adjusted continuously between 83 μm and 382 μm. The density fluctuation of a supersonic shear flow is measured using the FLDI system with a spatial resolution of 182 μm, and the density fluctuations at different locations of the supersonic shear flow are measured and analyzed. The ability to adjust the spatial resolution in this work is of great significance for enhancing the spatial resolution and flexibility of the FLDI system.

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