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At least 19 recordsLinked to original sources
arXiv2009

Comment on "Language Trees and Zipping" arXiv:cond-mat/0108530

Every encoding has priori information if the encoding represents any semantic information of the unverse or object. Encoding means mapping from the unverse to the string or strings of digits. The semantic here is used in the model-theoretic sense or denotation of the object. If encoding or strings of symbols is the adequate and true mapping of model or object, and the mapping is recursive or computable, the distance between two strings (text) is mapping the distance between models. We then are able to measure the distance by computing the distance between the two strings. Otherwise, we may take a misleading course. "Language tree" may not be a family tree in the sense of historical linguistics. Rather it just means the similarity.

cs.AI↗
arXiv2007

Nonlinear Dynamics of the Phonon Stimulated Emission in Microwave Solid-State Resonator of the Nonautonomous Phaser Generator

The microwave phonon stimulated emission (SE) has been experimentally and numerically investigated in a nonautonomous microwave acoustic quantum generator, called also microwave phonon laser or phaser (see previous works arXiv:cond-mat/0303188 ; arXiv:cond-mat/0402640 ; arXiv:nlin.CG/0703050) Phenomena of branching and long-time refractority (absence of the reaction on the external pulses) for deterministic chaotic and regular processes of SE were observed in experiments with various levels of electromagnetic pumping. At the pumping level growth, the clearly depined increasing of the number of coexisting SE states has been observed both in real physical experiments and in computer simulations. This confirms the analytical estimations of the branching density in the phase space. The nature of the refractority of SE pulses is closely connected with the pointed branching and reflects the crises of strange attractors, i.e. their collisions with unstable periodic components of the higher branches of SE states in the nonautonomous microwave phonon laser.

nlin.CD↗
arXiv2009

Self-Organized Bottleneck and Coexistence of Incongruous States in a Microwave Phonon Laser (Phaser)

Phenomena of emergence of regular and chaotic fine structure (FS) in stimulated emission (SE) power spectra of an autonomous microwave phonon laser (phaser) have been revealed and investigated experimentally in pink ruby at liquid helium temperatures. The phenomenon of a self-organized bottleneck in evolution of the microwave acoustic FS lines has been observed by means of narrow-range phonon SE spectral analysis. The large-scale phenomenon of coexistence of incongruous (stationary, periodic and chaotic) states in the whole spin-phonon phaser system has been revealed in experiments with panoramic power spectra of phonon SE. We propose a possible direction for modeling of both the observed phenomena on the basis of three-level cellular automata (S.D.Makovetskiy and D.N.Makovetskii, arXiv:cond-mat/0410460v2; S.D.Makovetskiy, arXiv:cond-mat/0602345v1) which emulate evolution of a bounded phaser-like excitable system.

nlin.AO↗
arXiv2009

Some Remarks on Nonlinear Properties of Pumping System of an Optical-Wavelength Acoustic Laser (Phaser)

New critical surfaces have been analytically found for a 3D vectorial model of bistable pumping system of an optical-wavelength acoustic laser (phaser). The Lyapunov instability is possible for this pumping system at the upper branch for a high quality factor Qc of a pump resonator: Qc/Qm >> 1, where Qm is the magnetic quality factor. This instability is of great interest for interpretaion of some experimental data on the optical-wavelength ruby phaser (see our previous papers arXiv:cond-mat/0303188, arXiv:cond-mat/0402640, arXiv:0704.0123, arXiv:0901.0449).

cond-mat.other↗
arXiv2007

The Tasaki-Crooks quantum fluctuation theorem

Starting out from the recently established quantum correlation function expression of the characteristic function for the work performed by a force protocol on the system [cond-mat/0703213] the quantum version of the Crooks fluctuation theorem is shown to emerge almost immediately by the mere application of an inverse Fourier transformation.

cond-mat.stat-mech↗
arXiv2008

Using self-similarity and renormalization group to analyze time series

An algorithm based on Renormalization Group (RG) to analyze time series forecasting was proposed in cond-mat/0110285. In this paper we explicitly code and test it. We choose in particular some financial time series (stocks, indexes and commodities) with daily data and compute one step ahead forecasts. We then construct some indicators to evaluate performances. The algorithm is supposed to prescribe the future development of the time series by using the self-similarity property intrinsically present in RG approach. This property could be potentially very attractive for the purpose of building winning trading systems. We discuss some relevant points along this direction. Although current performances have to be improved the algorithm seems quite reactive to various combinations of input parameters and different past values sequences. This makes it a potentially good candidate to detect sharp market movements. We finally mention current drawbacks and sketch how to improve them.

q-fin.ST↗
arXiv2010

Comment on "Essential discreteness in generalized thermostatistics with non-logarithmic entropy" by S. Abe

Recently Abe (arXiv:cond-mat/1005.5110v1) claimed that the q-entropy of nonextensive statistical mechanics cannot be generalized for the continuous variables and therefore can be used only in the discrete case. In this letter, we show that the discrete q-entropy can be generalized to continuous variables exactly in the same manner as Boltzmann-Gibbs entropy, contrary to the claim by Abe, so that q-entropy can be used with discrete as well as continuous variables.

cond-mat.stat-mech↗
arXiv2013

Comment on Phys. Rev. Lett. 110, 168702 (2013): Causal Entropic Forces

The recent Letter by Wissner-Gross and Freer [1] proposes a relationship between intelligence and entropy maximization based on a causal generalization of entropic forces over configuration space paths, which may beautifully induce sophisticated behaviors associated with competitive adaptation on time scales faster than natural evolution. These authors suggest a potentially general thermodynamic model of adaptive behavior as a non-equilibrium process in open systems. On the basis of the force-entropy correlations published by us a decade ago [2], we point out that their main relations have been previously reported within a simpler statistical thermodynamic model where non-interacting moving particles are assumed to form an elastic body. [1] A.D. Wissner-Gross and C.E. Free, Phys. Rev. Lett. 110 (2013) 168702 [2] E. Canessa, Physica A 341 (2004) 165 -also at arXiv:cond-mat/0403724

cond-mat.dis-nn↗
arXiv2018

Numerical study of the chiral $\mathbb{Z}_3$ quantum phase transition in one spatial dimension

Recent experiments on a one-dimensional chain of trapped alkali atoms [arXiv:1707.04344] have observed a quantum transition associated with the onset of period-3 ordering of pumped Rydberg states. This spontaneous $\mathbb{Z}_3$ symmetry breaking is described by a constrained model of hard-core bosons proposed by Fendley $et\, \,al.$ [arXiv:cond-mat/0309438]. By symmetry arguments, the transition is expected to be in the universality class of the $\mathbb{Z}_3$ chiral clock model with parameters preserving both time-reversal and spatial-inversion symmetries. We study the nature of the order-disorder transition in these models, and numerically calculate its critical exponents with exact diagonalization and density-matrix renormalization group techniques. We use finite-size scaling to determine the dynamical critical exponent $z$ and the correlation length exponent $ν$. Our analysis presents the only known instance of a strongly-coupled transition between gapped states with $z \ne 1$, implying an underlying nonconformal critical field theory.

cond-mat.str-el↗
arXiv2003

Flavor altering excitations of composite fermions

Past theoretical studies have considered excitations of a given flavor of composite fermions across composite-fermion quasi-Landau levels. We show that in general there exists a ladder of flavor changing excitations in which composite fermions shed none, some, or all of their vortices. The lowest energy excitations are obtained when the composite fermions do not change their flavor, whereas in the highest energy excitations they are stripped of all of their vortices, emerging as electrons in the final state. The results are relevant to the intriguing experimental discovery of Hirjibehedin {\em et al.} (cond-mat/0306152) of coexisting excitation modes of composite fermions of different flavor in the filling factor range $1/3>ν\geq 1/5$.

cond-mat.mes-hall↗
arXiv1995

Fermi Liquid - Non-Fermi Liquid Transition in the Double Exchange Model

Motivated by recent discovery of colossal magnetoresistance in La$_(1-x)$Ca$x$MnO$_3$ and other manganites, we have studied the double exchange model. We argue that the forced alignment of conduction-electron spin with the core spins that causes ferromagnetism also projects out a large part of the Hilbert space needed for coherent propagation of electrons carrying spin and charge. As a result, the electron becomes a composite object and its Green's function exhibits a two-fluid character: a coherent Fermi-liquid component associated with the ferromagnetically ordered core spins, and a non-Fermi liquid component associated with the disordered spins. With increasing temperature, there is continuous transfer of spectral weight from the Fermi liquid to the non-Fermi liquid component, until the former disappears above $T_c$. In an applied field spectral weight is transferred from the non-Fermi liquid to the component. Implications for the manganites are discussed.

cond-mat↗
arXiv2021

Electronic Structure, Correlation Effects and Physical Properties of d- and f-Metals and Their Compounds

The book includes all main physical properties of d- and f-transition-metal systems and corresponding theoretical concepts. Especial attention is paid to the theory of magnetism and transport phenomena. Some examples of non-traditional questions which are treated in detail in the book: the influence of density of states singularities on electron properties; many-electron description of strong itinerant magnetism; mechanisms of magnetic anisotropy; microscopic theory of anomalous transport phenomena in ferromagnets. Besides considering classical problems of solid state physics as applied to transition metals, modern developments in the theory of correlation effects in d- and f-compounds are considered within many-electron models. The book contains, where possible, a simple physical discussion. More difficult questions are considered in Appendices.

cond-mat↗
arXiv2001

Magnetic Susceptibility of the Balian-Werthamer Phase of 3He in Aerogel

The equilibrium superfluid phase of 3He impregnated into high-porosity silica aerogels appears to be a non-equal-spin-pairing state in zero field at all pressures, which is generally assumed to be the Balian-Werthamer (BW) phase modified by the depairing effects of the aerogel structure. The nuclear magnetic susceptibility played a key role in identifying the B-phase of pure 3He with the BW state. We report theoretical calculations of the nuclear magnetic susceptibility for the BW model of superfluid 3He in aerogel within the framework of the Fermi-liquid theory of superfluid 3He. Scattering of quasiparticles by the aerogel, in addition to Fermi-liquid exchange corrections, leads to substantial changes in the susceptibility of the BW phase. The increase in the magnetic susceptibility of 3He-aerogel compared to pure 3He-B is related to the polarizability of the gapless excitations and the impurity-induced local field. The limited data that is available is in rough agreement with theoretical predictions. Future measurements could prove important for a more definitive identification of the ordered phase, as well as for refining the theoretical model for the effects of disorder and scattering on the properties of superfluid 3He.

cond-mat↗
arXiv1996

Critical Behaviour of the Two Dimensional Step Model

We use finite--size scaling of Lee--Yang partition function zeroes to study the critical behaviour of the two dimensional step or sgn $O(2)$ model. We present evidence that, like the closely related $XY$--model, this has a phase transition from a disordered high temperature phase to a low temperature massless phase where the model remains critical. The critical parameters (including logarithmic corrections) are compatible with those of the $XY$--model indicating that both models belong to the same universality class.

hep-lat↗
arXiv1995

Polymer-Chain Adsorption Transition at a Cylindrical Boundary

In a recent letter, a simple method was proposed to generate solvable models that predict the critical properties of statistical systems in hyperspherical geometries. To that end, it was shown how to reduce a random walk in $D$ dimensions to an anisotropic one-dimensional random walk on concentric hyperspheres. Here, I construct such a random walk to model the adsorption-desorption transition of polymer chains growing near an attractive cylindrical boundary such as that of a cell membrane. I find that the fraction of adsorbed monomers on the boundary vanishes exponentially when the adsorption energy decreases towards its critical value. When the adsorption energy rises beyond a certain value above the critical point whose scale is set by the radius of the cell, the adsorption fraction exhibits a crossover to a linear increase characteristic to polymers growing near planar boundaries.

hep-lat↗
arXiv1992

Exact Solution of a Phase Separation Model with Conserved Order Parameter Dynamics

Pairwise particle-exchange model on a linear lattice is solved exactly by a new rate-equation method. Lattice sites are occupied by particles A and B which can exchange irreversibly provided the local energy in reduced. Thus, the model corresponds to a zero-temperature Kawasaki-type phase separation process. Due to local order-parameter conservation, the dynamics reaches a frozen state at large times, the structure of which depends on the initial conditions.

cond-mat↗
arXiv2001

New phasing method based on the principle of minimum charge

A new method of the phase determination in X-ray crystallography is proposed. The method is based on the so-called "minimum charge" principle, recently suggested by Elser. The electron density function $ρ$ is sought in the form $ρ({\bf x})=|ψ({\bf x})|^2$, where $ψ$ is an $n{-component}$ real function. The norm $\int|ψ({\bf x})|^2 d{\bf x}$ is minimized under the constraint imposed by the measured data on the amplitudes of Fourier harmonics of $ρ$. Compared to the straightforward implementation of the "minimum charge" scheme, the method attenuates the Gibbs phenomenon and is also capable of extrapolation of the diffraction data beyond the set of measured amplitudes. The method is applicable to quasicrystals under the condition that the number of components $n$ of the function $ψ$ is bigger than the dimensionality of the ``atomic surface''. It is successfully tested on synthetic data for Fibonacci chain and the octagonal tiling. In the latter case the reconstructed density map shows the shape of the atomic surface, despite relatively low data resolution.

cond-mat↗