Fluctuation and Noise Letters

We hypothesize possible new types of forces that would be the result of new types of interactions, static and a slow transient, between objects with related information contents (pattern). Such mechanism could make material composition dependence claimed by Fishbach, et al. in Eotvos type experiments plausible. We carried out experiments by using a high-resolution scale with the following memories: USB-2 flash drives (1-16GB), DVD and CD disks to determine if such an interaction exist/detectable with a scale resolution of 10 microgram with these test objects. We applied zero information, white noise and 1/f noise type data. Due to the non-reproducible changes of static weight of these memories after changing the information in them, we have not been able to clarify the existence of a reproducible static force between the memory and its environment even though the variations of static weight could possibly be the manifestation of the new type of interaction with changing environment. Interaction between two memories containing the same information was not detected at the given weight resolution. The hypothesis of slow transient interaction is more in line with the observations provided the observed effects are not artifacts. Writing or deleting the information in any of these devices causes peculiar negative weight transients, up to milligrams (mass fraction around 10⁻⁵), which is followed by various types of relaxation processes. These relaxations have significantly different dynamics compared to transients observed during cooling after stationary external heating. Interestingly, a USB-1 MP3 player has also developed comparable transient mass loss during playing music, even though its information content was not changed, and its power dissipation and warming-up was much less than that of the USB-2 flash drives. A classical interpretation of the negative weight transients could be absorbed water in hygroscopic components, though comparison of relaxation time constants with air humidity data does not support an obvious explanation. Another classical interpretation with certain contribution is the lifting Bernoulli force caused by the circulation due to convection of the warm air. However, in this case all observed time constants with a device should have been the same unless some hidden parameter causes the observed variations. Thus further studies are warranted to clarify if there is indeed a new force, which is showing up as negative mass at weight measurement when high-density structural information is changed or read out (measured). We estimate that, if the information-based interaction is real, the weight of bodies could be reduced and floating engines could be achieved with several orders of magnitude greater data handling capacities than today's values at the same mass.

The low frequency phase and amplitude or average collector current noises are studied in a bipolar transistor. The transit time fluctuation is calculated from the diffusion coefficient fluctuation in the base. The phase noise is proportional to the base transit time fluctuation of the carriers. We discuss the relation between the phase and amplitude fluctuations and find both fluctuations correlate each other in low frequency. An experimental study is carried out in a bipolar transistor.

This is a review paper on the study of the randomly scattered signals in a random multilayer based upon a stochastic and asymptotic formulation under strong mixing condition. This formulation generalizes the dominant Ito's formulation. The existence of a turning point of the random wave requires several type stochastic differential equations and the relevant limit theorems. The probability distributions of the randomly scattered signals have been obtained in the form of the Kolmogorov PDEs along the line of Khasminskii's limit theorem. This article demonstrates the step-by-step development of the relevant generators which contain the ultimate information for the probability distributions of the random signals.

Noise cannot be distinguished from information by simply measuring entropy. Nevertheless, the Rényi entropy can be used to calculate the entropy in a pixel-wise basis. Consequently, entropy histograms of images can be obtained. Hence, histograms of entropy can be used to quantify differences in the information contents of images. In this paper, entropy histograms of noisy images has been analyzed and results have been applied to define an index that measures the noise contents of natural images. The pixel-wise entropy of digital images has been calculated through the use of a spatial/spatial-frequency distribution. Therefore generalized Rényi entropy and a normalized windowed pseudo-Wigner distribution (PWD) have been selected to define a particular pixel-wise entropy. In this way, the shape of such a distribution of entropy indicates the amount of noise present in the image. Some examples are presented and discussed.

The possibilities of beam intensity noise rejection offered by a narrow-band closed opto-electronic loop system are studied. The noise added to the beam by the acousto-optic modulator used as the actuator is computed. The intensity noise of the in-loop beam can be found below the standard quantum limit but the extracted beam noise is always above this limit. For an input beam with a small excess noise, an increase of the noise can be observed. A simple model of the loop based on the noise transfer functions approach is used for the calculation of the noise power of beam intensities and photocurrents. The behavior of the system and the limitations of noise rejection are analyzed.

In Biology, all motor enzymes operate on the same principle: they trap favourable brownian fluctuations in order to generate directed forces and to move. Whether it is possible or not to copy one such strategy to play the market was the starting point of our investigations. We found the answer is yes! In this paper we describe one such strategy and appraise its performance with historical data from the European Monetary System (EMS), the US Dow Jones, the german Dax and the french Cac40.

Hot-electron stressing on GaN-based light emitting diodes (LEDs) has been performed using a dc stressing current. Detailed characterizations on the degradations in the optoelectronic and low-frequency noise properties of the devices have been conducted. Experimental results on I-V, electroluminescence (EL) and the integrated light output of the devices exhibit significant degradations with the stress time. Investigations on the low-frequency excess noise of the devices show that the degradations of the device properties arise from the generation of interface states at the InGaN/GaN heterointerface due to hot-electron stressing. Over two orders of magnitude increase in the current noise power spectral density, S_I(f), is typically observed prior to the failure of the devices. Furthermore, it is shown that the initial rate of increase in S_I(f) resulting from a dc current stress time of 48 hours is strongly correlated to the lifetimes of the devices demonstrating that flicker noise measurement can be used as a diagnostic tool for hot-electron hardness of the device.

Characteristics of the collective behavior of groups have been studied in diverse disciplines; in this work, we present an approach grounded in robotics. We first specify a model for collective behavior based on a formulation of a multi-agent robotic system. In contrast to some models found in the literature, we do not use stochastic mechanisms to introduce fluctuations. Rather, we present a fully deterministic model where fluctuations emerge due to the complex dynamics of a high-dimensional coupling of dynamical systems. We investigate the emergence of fluctuations in the trajectories of individual agents about the group average trajectory, and present an illustration of the onset of these fluctuations as inter-agent coupling is increased. A selection of behavioral modes are also provided, illustrating the nature of these fluctuations.

A reverse auction can be likened to a tendering process where a contract is awarded to the lowest bidder. This is in contrast to a conventional forward auction where the highest bidder wins. In this paper we analyze a minority game version of the reverse auction where an extra condition is imposed that, namely, the bid must be unique. In other words, the bidder with the lowest positive unique integer (LUPI) wins. We examine and compare two extrema, namely, the case when all players are rational and the case when all players make random selections.

This paper discusses noise-improved signal correlation through an array of autoregressive models of order one [AR (1)]. In a single model, when the input is a square wave or a cosine with a higher frequency, stochastic resonance (SR) exists. When the input is a cosine with a lower frequency, SR and suprathreshold stochastic resonance (SSR) both exist. SSR can also exist for a cosine with a higher frequency or a square wave through an array of AR (1) models. The efficacy of SR and SSR increases as the number of AR (1) models is raised or as the threshold is lowered in the array. There is a range of values of noise standard deviation where the correlation coefficient between the input and output signals is greater than that of the input signal and the noisy signal.

Atomic clocks are the core of a navigation system. Since an error in time results in an error in the user localization, it is fundamental that the stability is very high and constant with time. In this paper we discuss the dynamic Allan variance, or DAVAR, a representation of the time-varying stability of an atomic clock. We show by simulation its effectiveness in tracking common nonstationary behaviors of a clock.

Soil bulk density is a physical property of soils that affects water storage, water and nutrient movement, and plant root activity in the soil profile. The ability to quantify soil bulk density using vibration-induced conductivity fluctuation was investigated with possible field applications in the future. The AC electrical conductance of soil was measured using a pair of blade-like electrodes while exposing to periodic vibration. The blades were positioned longitudinally and transversally to the direction of the induced vibration to enable the calculation of a normalized index. This normalized index was expected to provide data independent from the vibration strength, and to reduce the effect of soil salinity and water content. Simulations on a simplified resistor lattice indicate that the ratio of transversal and longitudinal fluctuation decreases as soil bulk density increases. The experiment was conducted on natural and salinized fine sand at two moisture conditions and four compaction levels. The blade-shaped electrodes improved electrode-soil contact compared to cylindrical electrodes, and thereby, reduced measurement noise. Dry sand measurements showed an inverse correlation between the normalized conductivity fluctuation and soil bulk density for both longitudinal and transversal fluctuation. The wet natural and salinized soils performed very similarly as hypothesized, but their normalized VICOF response was not associated with bulk density changes. This lack of sensitivity might be attributed to the heavy electrodes and/or the specific vibration method used. The effects of electrode material, vibration method and soil properties on the experiment need further study.

The radiation field can be regarded as a collection of independent harmonic oscillators and, as such, constitutes a heat bath. Moreover, the known form of its interaction with charged particles provides a "rosetta stone" for deciding on and interpreting the correct interaction for the more general case of a quantum particle in an external potential and coupled to an arbitrary heat bath. In particular, combining QED with the machinery of stochastic physics, enables the usual scope of applications to be widened. We discuss blackbody radiation effects on: the equation of motion of a radiating electron (obtaining an equation of motion which is free from runaway solutions), anomalous diffusion, the spreading of a Gaussian wave packet, and decoherence effects due to zero-point oscillations. In addition, utilizing a formula we obtained for the free energy of an oscillator in a heat bath, enables us to determine all the quantum thermodynamic functions of interest (particularly in the areas of quantum information and nanophysics where small systems are involved) and from which we obtain temperature dependent Lamb shifts, quantum effects on the entropy at low temperature and implications for Nernst's law.

We address the problem of efficient detection and estimation of multiple weak signals in severe noise. To address this problem, we propose a concentrated peak representation (CPR) in which the spectral energy is concentrated in spectral peaks, and only the magnitudes and locations of the peaks are retained. We base our process on the cross spectral representation we have previously applied to other problems. The advantage of this representation is that it preserves the energy in signal components while significantly reducing the data volume. We demonstrate the method on a composite signal consisting of one billion samples, reducing the data volume by a factor of 1000 or more, and we demonstrate the detection of weak signals in the reduced representation.

Series of coding sequence lengths extracted from the chromosome of Bacillus subtilis were subjected to detrended fluctuation analysis (DFA). The non-linear characteristic of the DFA plot was interpreted in terms of short-range correlation. The analysis was performed on series consisting of the whole chromosome coding sequences, as well as on the leading and lagging strands. These were compared to the same series subjected to a randomization procedure. The series were divided into two halves, which also revealed different short-range characteristics. Similar results were noticed for seven strains of Escherichia coli. Therefore, the short-range correlation characteristics are sensitive to species and strains and could be used for comparative investigations of microbial genome organization.

A novel graded band gap channel Si-SiGe MOSFET structure has been suggested and its characteristics have been investigated. The investigations indicated that the suggested structure reduces the short-channel effects, increases the cut-off frequency, and hence makes its usage at high frequency and Low noise applications possible. To show the superior performance of the suggested structure at GHz frequencies, and as an example, the noise behavior of the structure is determined. First the device noise model parameters are calculated from D.C. and A.C. characteristics. The extracted noise model parameters are then used to determine the minimum noise figure at GHz frequencies. The effects of the different device parameters on the noise performance are determined. Finally, the results are compared with those of conventional MOSFET structure to show the superior performance of graded band gap Si-SiGe MOSFETs at high frequency ranges.