Identification of earthquake precursors in the hydrogeochemical and geoacoustic data for the Kamchatka peninsula by flicker-noise spectroscopy

A phenomenological systems approach for identifying potential precursors in multiple signals of different types for the same local seismically active region is proposed based on the assumption that a large earthquake may be preceded by a system reconfiguration (preparation) at different time and space scales. A nonstationarity factor introduced within the framework of flicker-noise spectroscopy, a statistical physics approach to the analysis of time series, is used as the dimensionless criterion for detecting qualitative (precursory) changes within relatively short time intervals in arbitrary signals. Nonstationarity factors for chlorine-ion concentration variations in the underground water of two boreholes on the Kamchatka peninsula and geacoustic emissions in a deep borehole within the same seismic zone are studied together in the time frame around a large earthquake on October 8, 2001. It is shown that nonstationarity factor spikes (potential precursors) take place in the interval from 70 to 50 days before the earthquake for the hydrogeochemical data and at 29 and 6 days in advance for the geoacoustic data.Comment: 8 pages, 4 figures; to be published in Nat. Hazards Earth Syst. Sc

Quantum Phase Transition in Pr2CuO4 to Collinear Spin State in Inclined Magnetic Field: A Neutron Diffraction Observation

In the external field slightly inclined to the $x$- or y-axis of the frustrated tetragonal atiferromagnet Pr2CuO4, a transition is discovered from the phase with orthogonal antiferromagnetic spin subsystems along [1,0,0] and [0,1,0] to the phase with the collinear spins. This phase is shown to be due to the pseudodipolar interaction, and transforms into the spin-flop phase S perp H asymptotically at very high field. The discovered phase transition holds at T=0 and is a quantum one, with the transition field being the critical point and the angle between two subsystems being the order parameter

Search for f1(1285)→π+π−π0f_1(1285) \to \pi^+\pi^-\pi^0 decay with VES detector

The isospin violating decay $f_1(1285)\to\pi^+\pi^-\pi^0$ has been studied at VES facility. This study is based at the statistics acquired in $\pi^- Be$ interactions at 27, 36.6 and 41 GeV/c in diffractive reaction $\pi^- N \to (f_1 \pi^-) N$. The $f_1(1285) \to \pi^+\pi^-\pi^0$ decay is observed. The ratio of decay probabilities $BR(f_1(1285) \to \pi^+\pi^-\pi^0)$ to $BR(f_1(1285) \to \eta \pi^+\pi^-) \cdot BR(\eta \to \gamma\gamma)$ is $\sim\:1.4$.Comment: 10 pages, 8 figures, presented at XII Conference on Hadron Spectroscop

On the multiplicity of the hyperelliptic integrals

Let $I(t)= \oint_{\delta(t)} \omega$ be an Abelian integral, where $H=y^2-x^{n+1}+P(x)$ is a hyperelliptic polynomial of Morse type, $\delta(t)$ a horizontal family of cycles in the curves $\{H=t\}$, and $\omega$ a polynomial 1-form in the variables $x$ and $y$. We provide an upper bound on the multiplicity of $I(t)$, away from the critical values of $H$. Namely: $ord\ I(t) \leq n-1+\frac{n(n-1)}{2}$if$\deg \omega <\deg H=n+1$. The reasoning goes as follows: we consider the analytic curve parameterized by the integrals along$\delta(t)$of the$n$``Petrov'' forms of$H$(polynomial 1-forms that freely generate the module of relative cohomology of$H$), and interpret the multiplicity of$I(t)$as the order of contact of$\gamma(t)$and a linear hyperplane of$\textbf C^ n$. Using the Picard-Fuchs system satisfied by$\gamma(t)$, we establish an algebraic identity involving the wronskian determinant of the integrals of the original form$\omega$along a basis of the homology of the generic fiber of$H$. The latter wronskian is analyzed through this identity, which yields the estimate on the multiplicity of$I(t)$. Still, in some cases, related to the geometry at infinity of the curves$\{H=t\} \subseteq \textbf C^2$, the wronskian occurs to be zero identically. In this alternative we show how to adapt the argument to a system of smaller rank, and get a nontrivial wronskian. For a form$\omega$of arbitrary degree, we are led to estimating the order of contact between$\gamma(t)$and a suitable algebraic hypersurface in$\textbf C^{n+1}$. We observe that$ord I(t)$grows like an affine function with respect to$\deg \omega$.Comment: 18 page

Искажение спектра сигнала протяженной цели в радаре с непрерывным частотно-модулированным сигналом

The problem of spectrum distortion in radar with a continuous frequency modulated signal (FMCW radar) is considered in the case of locating extended targets containing a large number of closely spaced reflection points. An extended target model is introduced for which a beat signal is analyzed based on its representation in the form of an amplitude-modulated oscillation. It is shown that the distortion of the spectrum occurs due to a certain relationship between the distances of the target points, the values of the carrier frequency and the deviation of the probe signal frequency. The results of numerical calculations for various values of the signal parameters and the long target model are given.En el presente artículo se aborda el problema de la distorsión del espectro en radares con señal continua de frecuencia modulada (radar FMCW) al producir objetivos prolongados que contienen un gran número de puntos de reflexión cercanos. El documento introduce un modelo de objetivo extendido para el cual se realiza un análisis de la señal de los latidos en función de su presentación en forma de oscilación de amplitud modulada. Este estudio muestra que la distorsión del espectro se produce como resultado de ciertas relaciones entre las distancias de los puntos de destino, los valores de frecuencia portadora y la frecuencia de desviación de la señal de sondeo. El artículo presenta los resultados de los cálculos numéricos para los diferentes valores de los parámetros de la señal y el modelo de objetivo extendido.No presente artigo, o problema da distorção do espectro em radares com sinal de frequência modulada contínua (radar FMCW) é abordado ao produzir objetivos prolongados que contêm um grande número de pontos de reflexão próximos. O documento introduz um modelo objetivo estendido para o qual uma análise do sinal de batimentos cardíacos é realizada de acordo com sua apresentação na forma de uma oscilação de amplitude modulada. Este estudo mostra que a distorção do espectro ocorre como resultado de certas relações entre as distâncias dos pontos de destino, os valores da freqüência da portadora e a freqüência do desvio do sinal sonoro. O artigo apresenta os resultados dos cálculos numéricos para os diferentes valores dos parâmetros do sinal e do modelo objetivo estendido.Рассмотрена проблема искажения спектра в радаре с непрерывным частотно-модулированным сигналом (FMCW радаре) при лоцировании протяженных целей, содержащих большое число близкорасположенных точек отражения. Введена модель протяженной цели, для которой проведен анализ сигнала биений на основе представления его в виде амплитудно-модулированного колебания. Показано, что искажение спектра возникает в результате определенных соотношений между расстояниями точек цели, значениями несущей частоты и частоты девиации зондирующего сигнала. Приведены результаты численных расчетов для различных значений параметров сигнала и модели протяженной цели