@incollection{statphys23_1117, title = {Crackling noise in ferromagnetic materials: Barkhausen effect and asymmetry in the pulse shape}, address = {Genova, Italy}, author = {F. Colaiori and S. Zapperi and C. Castellano and G. Durin}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=1117}, abstract = {The Barkhausen effect is due to the jerky motion of domain walls in disordered magnetic materials, and is one example of {\it crackling noise} in condensed matter physics. The application of an external field acts as a pressure on domain walls, but because of the presence of defects, as inclusions and dislocations, the motion proceeds in avalanches. These avalanches show interesting statistical properties that encode important information on the magnetization reversal process on a microscopic scale. A microscopic theory based on a Langevin equation for the elastic domain walls describes with great accuracy most experimental results. However it does not account for the lack of symmetry in the average pulse shape. This can be explained by taking into account the contribution from Eddy currents, which results in a negative effective mass associated with the wall.}, biburl = {http://www.bibsonomy.org/bibtex/2ca5cb2bb6d3010fbadf31d8e7a6f81e7/statphys23}, keywords = {topic-3 statphys23 hysteresis effect noise crackling barkhausen} } @incollection{statphys23_1047, title = {Stochastic description of time delayed feedback oscillators}, address = {Genova, Italy}, author = {L.G. Morelli and F. Julicher}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=1047}, abstract = {Many cellular processes are regulated or driven by genetic oscillators, as in the case of circadian clocks, the cell cycle, and patterning developing vertebrate embryos. Due to the stochastic nature of gene expression, the period of such oscillations is subject to fluctuations. The precision of the oscillator can be characterized by the quality factor. We study the precision of genetic oscillators in a generic stochastic feedback system. We include the effects of amplification noise, arising for example from bursts of transcription and translation. We show that high quality is possible for certain parameter ranges even when the number of molecules is low and amplitude fluctuations are large.}, biburl = {http://www.bibsonomy.org/bibtex/2978e1bd3676212fef9a48fa258ab2f3a/statphys23}, keywords = {topic-10 oscillators feedback stochastic noise amplification phase amplitude delays genetic statphys23} } @incollection{statphys23_0870, title = {Low dimensional behavior in three-dimensional coupled map lattice}, address = {Genova, Italy}, author = {P. Muruganandam and G. Francisco and M. Menezes and F.F. Ferreira}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=870}, abstract = {The analysis of one-,two-,three-dimensional coupled map lattices is here developed under a statistical and a dynamical perspective. We show that the three-dimensional CML exhibts low dimensional behavior with long range correlation and the power spectrum follows a 1/f noise. This approach leads to an integrated understanding of the most important properties of these universal models of spatiotemporal chaos}, biburl = {http://www.bibsonomy.org/bibtex/2f74690e9ace187155da372eda86a7fc5/statphys23}, keywords = {timeseries chaos noise spatiotemporal topic-5 statphys23} } @incollection{statphys23_0817, title = {Intermittent fluctuations in a single cardiac cell}, address = {Genova, Italy}, author = {T. Harada and T. Yokogawa}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=817}, abstract = {It is now widely accepted that a variety of physiological functions, including generation of action potentials in nerves and contraction of muscle, are cooperative phenomena of many molecular machines. The size of each molecular machine, such as an ion channel and a molecular motor, is typically several nanometers, and their behavior is intrinsically stochastic. In the last couple of decades, the properties of single molecular machines have been intensively investigated by use of newly developed single-molecule-detection techniques. In addition, much theoretical effort has also been made in order to account for their properties. As a consequence, knowledge on single molecular machines is being rapidly accumulated. On the basis of the achievements in single-molecule statistical physics, we believe that to understand the properties of complexes of molecular machines is now in scope. There remains a large vacancy to be explored between single molecules and macroscopic tissue. In particular, the behavior of a single cell has to be studied from a viewpoint of statistical physics, because cooperative phenomena of large but finite number of molecular machines may play important roles in the scale of a single cell. In this perspective, we are interested in the long-term behavior of a single cardiomyocyte (a heart muscle cell). Cardiomyocytes are the main constituent of a heart. It has been known that these cells exhibit periodic contraction when they are cultivated in vitro. The erlier studies on the culture of cardiomyocytes have concentrated on the dynamics of a cellular network, where many cells are tightly coupled to each other. However, the properties of a single cell, in particular its long-term behaviors, have not been paid much attention. We thus constructed an experimental system to monitor spontaneous contractions of a single isolated cardiomyocyte derived from newborn rats in a wide range of time scale. As a consequence, complex activities of a single isolated cardiomyocyte were observed. The timings of spontaneous contractions (beats) are found to fluctuate with a large magnitude. For a relatively short time scale (below several minites), the series of inter-beat intervals (IBIs) were found to be Poissonian. However, for larger time scales, on/off switching of activity was frequently observed. Off periods, where no spontaneous contraction is observed, sometimes range to several hours. The distribution of IBIs exhibits a power-law tail of a Lorentz type for large intervals. Furthermore, it was found that the time series of IBIs possess a scale-invariant correlation that is characterized as 1/f noise. These experimental findings imply that a single cardiomyocyte cannot be regarded as a simple limit cycle oscillator. We hope that further investigation of the long-term behavior of a single cell leads to understanding of cooperative phenomena of molecular machines inside a cell.}, biburl = {http://www.bibsonomy.org/bibtex/262ccbfae5b0485c6e8fa0ac20ae17afe/statphys23}, keywords = {topic-10 statphys23 oscillation noise cardiac single cell power-law experiment distributions} } @incollection{statphys23_0777, title = {Robustness of adiabatic passage through a quantum critical point}, address = {Genova, Italy}, author = {A. Fubini and G. Falci and A. Osterloh}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=777}, abstract = {We analyze the crossing of a quantum critical point based on exact results for the transverse XY model. In dependence of the change rate of the driving field, the evolution of the ground state is studied while the transverse magnetic field is tuned through the critical point with a linear ramping. The excitation probability is obtained exactly and is compared to previous studies and to the Landau-Zener formula, a long time solution for non-adiabatic transitions in two-level systems. The exact time dependence of the excitations density in the system allows to identify the adiabatic and diabatic regions during the sweep and to study the m esoscopic fluctuations of the excitations. The effect of white noise is investigated, where the critical point transmutes into a non-hermitian ``degenerate region''. Besides an overall increase of the excitations during and at the end of the sweep, the most destructive effect of the noise is the decay of the state purity that is enhanced by the passage through the degenerate region.}, biburl = {http://www.bibsonomy.org/bibtex/203d506efc28e5d8a5c4f1a3ecc9e0145/statphys23}, keywords = {dynamics adiabatic topic-8 noise statphys23 transitions spin quantum phase passage models} } @incollection{statphys23_0734, title = {Anomalous Diffusion and Current Inversion Induced by Colored non-Gaussian Noise}, address = {Genova, Italy}, author = {C.K. Hu and B.C.B. Bag}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=734}, abstract = {We study stochastic process driven by colored non-Gaussian noises [B.C. Bag and C.-K. Hu, Phys. Rev. E 75, April (2007)] and find that the latter can induce ballistic diffusion in noise driven free particle process. The possible connection of the ballistic diffusion with diffusion of ions through ion channels is discussed. For the flashing ratchet model we find that there is a current inversion in the variation of the current with half cycle period which accounts potential on-off operation. The current inversion disappears if one switches from non-Gaussian to Gaussian noise. The phenomena of current inversion is also found to occur as the asymmetric character of the ratchet potential grows. On increasing noise correlation time ($\tau$) mean velocity of a particle first increases and then decreases after passing through a maximum if the noise is non-Gaussian. For Gaussian noise current monotonically decreases. The current is enhanced if the noise is more departure from Gaussian behavior.}, biburl = {http://www.bibsonomy.org/bibtex/2f783f360629b347f48b7db3a27b0d1ec/statphys23}, keywords = {ratchet statphys23 inversion diffusion model non-gaussian colored topic-3 current anomalous noise} } @incollection{statphys23_0708, title = {Dynamics in an anisotropic XY spin system driven by dichotomous Markov noise}, address = {Genova, Italy}, author = {K. Ouchi and N. Tsukamoto and N. Fujiwara and T. Horita and H. Fujisaka}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=708}, abstract = {The dynamics of ferromagnetic systems below their critical temperatures driven by a periodically oscillating magnetic field $F(t)$ have been extensively studied both theoretically and experimentally. It is well known that the systems exhibit two qualitatively different behaviors depending on the amplitude $h$ and the frequency $\Omega$ of $F(t)$. The transition between the two phases are often referred to as the dynamical phase transition (DPT). \par It is quite interesting to ask whether DPT is observed under another kind of applied field, especially random field with bounded amplitude. The fundamental aim of this presentation is to study the dynamics of the magnetization with a dichotomous Markov noise (DMN) $F(t)$ instead of periodically oscillating external field. The DMN is a random noise taking two values $\pm H_0$ and the probability $p(\tau)$ that $F(t)$ continues to take the identical value $+H_0$ of $-H_0$ longer than time $\tau$ is given by \begin{equation} p(\tau) = e^{-\tau / \tau_f}, \end{equation} where the correlation time of $F(t)$ is equal to $\tau_f /2$. \par We consider the anisotropic XY spin system driven by $F(t)$, i.e., \begin{equation} \dot{s} = s - |s|^2 s + \gamma s^* + F(t), \end{equation} where the order parameter $s(t)$ is a complex number and $\gamma$ is a control parameter to characterize the anisotropy of the system. We focus on the motion from $\Re s(t) > 0$ to $ \Re s(t) < 0$ and vice versa, which is called the ``switching process''. There are two regions in the ($\gamma$, $H_0$) plane with a fixed $\tau_f$ according to whether the switching process occurs. Furthermore, the switching process region is divided into several parts in terms of the switching time distribution $\rho(t)$. In the ``Ising type switching'' region, $\rho(t)$ is given by \begin{equation} \rho(t) \simeq e^{-t/\bar{\tau}} / \bar{\tau}, \end{equation} where $\bar{\tau}$ denotes an average time of switching processes. In the ``Bloch type switching'' region, on the other hand, $\rho(t)$ is characterized as \begin{equation} \rho(t) \simeq t^{-3/2}. \end{equation} There is also a region where two types of switching process coexist. We will investigate how such the distributions are formed. Furthermore, the power spectrum of $\Re s(t)$ and $\Im s(t)$ will be discussed.}, biburl = {http://www.bibsonomy.org/bibtex/24cd77ee030c002755686181729a10ce9/statphys23}, keywords = {markov phase dynamical xy system noise transition spin topic-3 statphys23 dichotomous} } @incollection{statphys23_0705, title = {External Noise Effects on the Dynamics of an Extended Chaotic System}, address = {Genova, Italy}, author = {J.A. Revelli and M.A. Rodriguez and H.S. Wio}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=705}, abstract = {The study of the behavior of nonlinear dynamical systems when submitted to different kind of perturbations has been the subject of a very large number of analysis. However, studies on the effect of noise on spatially extended chaotic systems are scarce. In this work we investigate the effects of a time-correlated noise on an extended chaotic system. The chosen model, the so called Lorenz '96, a kind of {\it toy model} described by $$\dot{x}_{i}(t) = x_{i-1} [x_{i-2} - x_{i+1}] - x_{i} + F_{i}(t),\,\,\,\,\,\, i=1, ..,N$$ is of interest for the analysis of climate behavior. We have assumed that $F_{i}(t) = F_{med} + \psi_{i} (t)$, with $F_{med}$ a (constant) deterministic, and $\psi_{i} (t)$ a stochastic contribution. Through the analysis of the system's temporal evolution and its time and space correlations, we have obtained numerical evidence of two stochastic resonance-like behavior. Such a behavior is seen when both, the usual and a generalized signal-to-noise ratio (SNR) function, called {\it global} SNR, are depicted as a function of the external noise intensity or the system size. The resonances typically occur at frequencies corresponding to system's quasi-periodic orbits. The possible relevance of these and other findings for an optimal climate prediction are discussed.}, biburl = {http://www.bibsonomy.org/bibtex/2695a37c34b9745e2d47241661c108e23/statphys23}, keywords = {dynamical chaos extended behavior nonlinear systems topic-3 statphys23 noise climate effects} } @incollection{statphys23_0702, title = {Fluctuation theorem for the Langevin system having a memory kernel}, address = {Genova, Italy}, author = {T. Ohkuma and T. Ohta}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=702}, abstract = {The previous fluctuation theorem obtained in a stochastic Markov process is generalized to a non-Markovian system. To be specific, we consider a system governed by the generalized Langevin equation that has a memory kernel; \begin{equation} \ddot{x} + \int_{t_{0}}^{t} ds \gamma (t-s) \dot{x} (s) = F(x(t), \lambda (t)) + \xi (t) \end{equation} where $\gamma (t)$ is the memory kernel, $F(x, \lambda (t))$ denotes the external force, and $\lambda (t)$ represents the external parameter that we can control deterministically. The initial time has been set to $t_{0}$. The noise $\xi (t)$ is assumed to have the Gaussian property and satisfies the fluctuation dissipation relation of the 2nd kind, $\langle \xi (t) \xi (t') \rangle = \beta^{-1} \gamma (|t-t'|)$ where $\beta$ is the inverse thermal energy. \vspace{0.2cm} We derive the expression of the non-Markovian version of the Crooks fluctuation theorem [1] that relates the statistical average of the two different dynamics characterized by the forward process and the reversed process where the time dependence of both $x(t) $ and $ \lambda (t) $ is reversed. It is emphasized that, since this fluctuation theorem deals with a trajectory of the gross variables during a finite time interval, the dependence of the initial condition and the transient property can be investigated explicitly. A similar study has been carried out without assuming the fluctuation dissipation relation of the second kind but with restricting to the stationary state asymptotically in time [2]. \vspace{0.2cm} In order to calculate the probability of the realization for a trajectory, $x(t), t \in [t_{0} , T]$, we apply the path integral formalism of the occurrence probability for a noise sequence. The fluctuation theorem is derived by comparing the probability of the forward process with that of the reversed process. It is found that the exponential part of the probability ratio corresponding to the entropy production is not affected by the time delay caused by the memory kernel. \vspace{0.2cm} As a special case of the theorem, we find that the entropy monotonically increase. This can be concluded without deriving the time evolution for the probability destribution function of the gross variable such as the solution of the Fokker-Planck equation. The Jarzynski equality which requires that the initial state should be in thermal equilibrium is also verified. We confirm the fluctuation theorem by numerical simulations of a simple system. \vspace{0.2cm} 1) G. E. Crooks, Phys. Rev. E. \textbf{61}, 2361 (2000).\\ 2) F. Zamponi, F. Bonetto, L. F. Cugliandolo and J. Kurchan, J. Stat. Mech. Theory and Experiment, P09013 (2005).}, biburl = {http://www.bibsonomy.org/bibtex/279c55484ca0492c2ad2e72b232d1e368/statphys23}, keywords = {statphys23 noise topic-1 colored fluctuation} } @incollection{statphys23_0639, title = {Microscopic study of extensions of the Langevin equation to nonlinear transport}, address = {Genova, Italy}, author = {T. Yuge and A. Shimizu}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=639}, abstract = {The Langevin model is used in many studies of nonequilibrium phenomena. The foundation of the model, however, is unclear, particularly for systems which have particle flow, many-body interactions and nonlinear response. Since the simplest Langevin equation, $Mdv(t)/dt=F-\gamma v(t)+\xi(t)$, cannot reproduce the nonlinear transport and is equivalent to an equilibrium system in a moving frame, one often adds a slowly-varying potential term to treat nonlinear response. When we consider macroscopically uniform systems, however, such a potential is absent. In this work, we extend the Langevin equation into various forms so that they can describe nonlinear transport in macroscopically uniform systems, by replacing $\gamma$, $F$ and $\xi$ by the $F$-dependent friction coefficient $\gamma (F)$, the effective external force $F_{\rm eff}$ and the $F$-dependent noise $\xi (t;F)$ respectively. We investigate the validity of each form using the molecular dynamics (MD) simulation of a microscopic model, by which we can evaluate all quantities of interest, including the electric current, kinetic temperature, Langevin noise, and so on. As the microscopic model, we employ the standard model of nonlinear electrical conduction, which was recently proposed by us [1]. The model has been shown to have very good properties: For example, the nonequilibrium steady states are realized both in the linear and nonlinear response regimes, the electric conductivity is independent of sample size, and the first fluctuation-dissipation theorem (FDT) holds near equilibrium. We choose the velocity of the center of mass of electrons as $v$ and compute the Langevin noise acting on it to study the validity of the extended Langevin equations. We adjust the effective external force as $F_{\rm eff}=M\gamma (F)\langle v \rangle _F^{\rm MD}$ to agree with the nonlinear response of $v$ ( $\langle \cdots\rangle _F^{\rm MD}$ implies the average in the MD simulation), and consider three modifications of $\gamma$, that is (1)the linear response coefficient: $\gamma ^{(1)}(F) = \lim_{F\to 0} F/M\langle v \rangle _F^{\rm MD}$ (independent of $F$), (2)the ratio of $F$ and steady velocity: $\gamma ^{(2)}(F) = F/M\langle v \rangle _F^{\rm MD}$ (this leads to $F_{\rm eff}^{(2)}=F$) and (3)the differential coefficient: $\gamma ^{(3)}(F) = (M{\rm d}\langle v \rangle _F^{\rm MD}/{\rm d}F)^{-1}$. Then, defining the noise as $\xi _{\rm MD}(F) \equiv M{\rm d}v/{\rm d}t - F_{\rm eff} + M\gamma (F) v$, we study whether the noise satisfies the ``generalized second FDT'', $g_{\xi_{\rm MD}}(\omega ;F) = 2M^2 \gamma (F)\langle (v - \langle v\rangle _F^{\rm MD})^2\rangle _F^{\rm MD}$, which is a sufficient condition to reproduce the $F$-dependence of the variance of $v$. Here, $g_{\xi_{\rm MD}}(\omega ;F)$ is the spectral intensity of the noise. In Fig. 1, we show $g_{\xi_{\rm MD}}(\omega ;F)$ and compare it with the right-hand side of the ``generalized 2nd FDT''. At the equilibrium state and in the linear response regime the ``generalized 2nd FDT'' holds within the errorbars. In the nonlinear response regime, the ``generalized 2nd FDT'' are valid within the errorbars for lower frequencies if we use $\gamma ^{(3)}(F)$ (the differential response coefficient). 1) T. Yuge, N. Ito and A. Shimizu: J. Phys. Soc. Jpn. {\bf 74}, 1895 (2005).}, biburl = {http://www.bibsonomy.org/bibtex/2a3fd3cfd2dff6f20aac926eec193d7ed/statphys23}, keywords = {transport noise md topic-3 langevin statphys23 simulation nonlinear} } @incollection{statphys23_0593, title = {Creep rupture in thermally activated fiber-bundle model}, address = {Genova, Italy}, author = {N. Yoshioka and F. Kun and N. Ito}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=593}, abstract = {The creep rupture of fiber composites under a uniaxial constant tensile stress is studied in the framework of the fiber-bundle model with thermal noise. In the case of global load sharing rule, the nonmonotonic behavior for the time evolution of the average burst size, $\langle \Delta(t) \rangle$, is numerically observed in some parameter regimes. Assuming homogeneous fibers, the nonmonotonicity is described by the explicit solution of the average burst size as a function of load per fiber after the burst. In the case of local load sharing rule, it is numerically observed that the failure time has a power-law divergence of system size $L$, $t_\mathrm{f} \sim L^{-k}$, where $k$ depends on parameters like temperature and stress. It is also shown that the failure time is scalable in the similar, but somewhat different, way known in the case of global load sharing rule [1-3]. Furthermore, burst size distributions are studied for both of load sharing rules. It is observed that the burst size distributions follow power-law, $D(\Delta) \sim \Delta^{-\xi}$, where $\xi$'s are different from that of the conventional fiber-bundle model without thermal noise. Especially, in the case of global load sharing rule and homogeneous fibers, $\xi$ tends to 2 as temperature goes to zero. The effect of the nonmonotonicity of the burst size is found as the discontinuity in some burst size distributions. ----------------- [1] S. Roux, Phys. Rev. E \textbf{62}, 6164 (2000). [2] R. Scorretti, S. Ciliberto, and A. Guarino, Europhys. Lett. \textbf{55}, 626 (2001). [3] S. Ciliberto, A. Guarino, and R. Scorretti, Physica D \textbf{158}, 83 (2001).}, biburl = {http://www.bibsonomy.org/bibtex/26744983f62013a5c4e8cedd33a7704d0/statphys23}, keywords = {noise creep topic-4 fiber-bundle thermal fiber model composites statphys23 rupture} } @incollection{statphys23_0542, title = {Localization in disordered media, anomalous roughening and coarsening dynamics of faceted surfaces}, address = {Genova, Italy}, author = {I.G. Szendro and J.M. L\'opez and M.A. Rodr{\'\i}guez}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=542}, abstract = {We study a surface growth model related to the Kardar-Parisi-Zhang equation for nonequilibrium kinetic roughening, but where the thermal noise is replaced by a static columnar disorder $\eta(\mathbf{x})$, \begin{equation} \partial_t h = \nu \nabla^2 h + \lambda (\nabla h)^2 + \eta({\bf x}). \label{kpz_eq} \end{equation} This model is one of the many representations of the problem of particle diffusion in trapping/amplifying disordered media, \begin{equation} \partial_t \phi = \gamma \nabla^2 \phi + \eta(\mathbf{x}) \phi(\mathbf{x},t), \label{mult_eq} \end{equation} where the random field $\eta(\mathbf{x})$ is Gaussian with zero mean and delta correlated \begin{equation} \langle \eta(\mathbf{x}) \eta(\mathbf{x}') \rangle = 2D \delta^{d}(\mathbf{x}-\mathbf{x}'). \end{equation} after the the nonlinear Hopf-Cole transformation $\phi(\mathbf{x},t) = \exp[\lambda \, h(\mathbf{x},t)/\nu]$. We find that probability localization in the diffusion problem translates into facet formation in the equivalent surface growth problem. Coarsening of the pattern can therefore be identified with the diffusion of the localization center. The faceted pattern leads to nontrivial scaling properties, including anomalous scaling. This is in excellent agreement with and earlier conjecture of Ramasco {\it et. al.} for kinetic roughening of faceted surfaces. Moreover, we have found that the surface can be decomposed in two different contributions. The global pattern, which dominates the surface scaling at long wavelengths, and a local fluctuation component, which spatial properties are characterized by a roughness exponent $\alpha = \alpha_\mathrm{KPZ}$. An adiabatic approximation allowed us to relate the spatial scaling of the local noisy component to KPZ critical behavior. However, the dynamic exponent is dominated by the global pattern and we found $z=1.35 \pm 0.05$ and $z = 1.10 \pm 0.05$ in $d=1$ and $d=2$, respectively In a wider context, our study sheds light onto the scaling properties in other systems displaying this kind of patterned surfaces. We believe that similar mechanisms might be at work in other growth systems that produce kinetically rough faceted surfaces. In particular, our study suggests that the spectral roughness exponent that was conjectured by Ramasco {\it et. al.} can play a role in the description of the scaling properties in other systems displaying this kind of patterned surfaces.}, biburl = {http://www.bibsonomy.org/bibtex/25701298b8ae39a92b7c3f81e165d6050/statphys23}, keywords = {theory fluctuation growth film noise phenomena models dynamic patterns critical topic-3 statphys23 random processes} } @incollection{statphys23_0503, title = {Emergent Dynamic Phenomena on Networks}, address = {Genova, Italy}, author = {B. Tadic}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=503}, abstract = {As complex environments, networks may affect dynamic processes on them in various ways. Recent study of transport (diffusive) processes on different networks suggests that larger network complexity leaves more room for the process improvement and optimization. On the other hand, the structure--dynamics interdependence reveals that the emergent dynamic phenomena on networks can be effectively used for network diagnostics or as a guide for network re-construction from the empirical data. Here we review certain universal dynamic features (scaling, noise and flow correlations, return-time statistics etc.), which are characteristic for the diffusive processes on scale-free trees and cyclic correlated scale-free graphs. Results of numerical simulations on large networks will be presented. We also discuss robustness/limits of these findings and point out some open theoretical problems in the field.}, biburl = {http://www.bibsonomy.org/bibtex/25e48d4ab20a8ad3f0106ae664941d2cc/statphys23}, keywords = {topic-11 flow processes numerical simulations networks statphys23 return-time transport noise} } @incollection{statphys23_0455, title = {Zigzag domain-wall dynamics in ferromagnetic thin films}, address = {Genova, Italy}, author = {B. Cerruti and S. Zapperi and E. Vives}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=455}, abstract = {One of the still open questions in the physics of magnetic systems is the comprehension of the hysteretic behavior of ferromagnetic thin films. Experiments on two dimensional specimens highlight different features from bulk systems, due to the greater complexity of domain structure in two dimensions. In this contribution we analyze the effects of the long range dipolar interactions on the domain walls dynamics. We present a model for the study of a single zigzag domain wall motion in a ferromagnetic system with in-plane magnetization, driven by an external magnetic field, and find that such a model is suitable for the interpretation of the dynamic hysteresis (1) and Barkhausen noise (2) experiments on two dimensional specimens. Moreover, the magnetization-driven regime is analyzed, in order to investigate the influence of the driving mechanism on the hysteretic response of the system. (1) B. Cerruti and S. Zapperi, Phys. Rev. B 75, 064416 (2007) (2) B. Cerruti and S. Zapperi, J. Stat. Mech. (2006) P08020}, biburl = {http://www.bibsonomy.org/bibtex/2db300601b0681df2b239482317d59c06/statphys23}, keywords = {topic-3 noise magnetism statphys23 barkhausen hysteresis} } @incollection{statphys23_0289, title = {Non-Markovian Dynamics in the Theory of Full Counting Statistics}, address = {Genova, Italy}, author = {C. Flindt and A. Braggio and T. Novotn\'{y} and M. Sassetti and A.P. Jauho}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=289}, abstract = {Full counting statistics (FCS) of charge transfer through mesoscopic devices has become a significant field of research, no longer only being of theoretical interest, but recently also encompassing a number of experimental studies probing the distribution of electrons transported through nanoscopic structures [1]. In recent years, the question of how decoherence in coherently coupled quantum dot systems affects the FCS has been of particular interest [2]. Conventionally, the FCS of transport through Coulomb-blockade devices is explained using Markovian equations of motion [3]. This approach relies on finding the analytic dependence of an extremal eigenvalue on the counting field – a task that might be highly non-trivial for systems with several states involved in the transport. We circumvented this technical problem by developing an abstract perturbation theory using super-operators which enables the calculation of the current cumulants for systems exhibiting Markovian dynamics with, in principle, any number of states [4]. Interactions with additional degrees of freedom, e.g. a heat bath, may, however, lead to non-Markovian dynamics with clear signatures in the higher-order moments of the FCS as was recently demonstrated in Ref. 5. We combine our perturbative method from Ref. 4 with the approach developed in Ref. 5 and present a general theory for the FCS of systems governed by non-Markovian equations of motion [6]. The theory is again applicable to systems with any number of states, and we calculate the current cumulants of transport through coherently coupled quantum dots, where interactions with a heat bath introduce memory effects. We extend our discussions to quantum dot systems with coupling to a nanomechanical resonator or a nearby charge detector [7] and show how the experimental and/or theoretical results for the FCS of these very different systems can all be understood in terms of a new unified interpretation based on non-Markovian dynamics [6]. References: 1) S. Gustavsson et al., Counting Statistics of Single-Electron Transport in a Quantum Dot, Phys. Rev. Lett. 96, 076605 (2006). T. Fujisawa et al., Bidirectional Counting of Single Electrons, Science 312, 1634 (2006).\\ 2) G. Kiesslich et al., Counting statistics and decoherence in coupled quantum dots, Phys. Rev. B 73, 033312 (2006). R. Aguado and T. Brandes, Shot Noise Spectrum of Open Dissipative Quantum Two-Level Systems, Phys. Rev. Lett. 92, 206601 (2004). \\ 3) D. A. Bagrets and Yu. V. Nazarov, Full counting statistics of charge transfer in Coulomb blockade structures, Phys. Rev. B 67, 085316 (2003). \\ 4) C. Flindt, T. Novotn\'{y}, and A.-P. Jauho, Full counting statistics of nano-electromechanical systems, Europhys. Lett. 69, 475 (2005).\\ 5) A. Braggio, J. Koenig, and R. Fazio, Full Counting Statistics in Strongly Interacting Systems: Non-markovian Effects, Phys. Rev. Lett. 96, 026805 (2006).\\ 6) C. Flindt, A. Braggio, T. Novotn\'{y}, M. Sassetti, and A.-P. Jauho, Full counting statistics of non-Markovian systems, in preparation (2007).\\ 7) F. Haupt et al., Anomalous suppression of the shot noise in a nanoelectromechanical system, Phys. Rev. B 74, 205328 (2006). S. Gustavsson et al., Measurements of higher order noise correlations in a quantum dot with a finite bandwidth detector, cond-mat/0607192 (2006).}, biburl = {http://www.bibsonomy.org/bibtex/20649741342d7c856a5fb28d8b0aac6cc/statphys23}, keywords = {statistics quantum mesoscopic full fluctuations conductors transport counting topic-3 statphys23 noise electronic} } @incollection{statphys23_0268, title = {$1/f$ noise and avalanche scaling: Theory and applications in non-equilibrium systems}, address = {Genova, Italy}, author = {L. Laurson and M.J. Alava}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Luciano Pietronero and Vittorio Loreto and Stefano Zapperi}, month = {9-13 July}, year = 2007, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=268}, abstract = {Recent developments have made it possible to understand the origin of $1/f$ -noise in several non-equilibrium systems exhibiting avalanches. For Barkhausen noise, it has been shown [1] that the power spectrum exponent $\alpha$ is related to the scaling of average avalanche sizes with their duration. Our work shows that the equality of $\alpha$ to $\gamma_{st}$, from the size-duration scaling $\langle s(T) \rangle \sim T^{\gamma_{st}}$, is applicable to a wide class of systems from sandpile models of self-organized criticality (SOC) [2], to dislocation avalanches in plastically deforming crystals [3] to fluid invasion into disordered media [4]. In the case of SOC, our observation is that the noise exponent of the activity time series $V(t)$ follows from the avalanche scaling and therefore from the underlying universality class of the model and spatial dimension at hand. This implies that for $d