Showing papers in "EPL in 1986"
TL;DR: In this article, the authors report on two experiments using an atomic cascade as a light source, and a triggered detection scheme for the second photon of the cascade, which is in contradiction with any classical wave model of light but in agreement with a quantum description involving single-photon states.
Abstract: We report on two experiments using an atomic cascade as a light source, and a triggered detection scheme for the second photon of the cascade. The first experiment shows a strong anticorrelation between the triggered detections on both sides of a beam splitter. This result is in contradiction with any classical wave model of light, but in agreement with a quantum description involving single-photon states. The same source and detection scheme were used in a second experiment, where we have observed interferences with a visibility over 98%. During the past fifteen years, nonclassical effects in the statistical properties of light have been extensively studied from a theoretical point of view (l), and some have been experimentally demonstrated (2-71. All are related to second-order coherence properties, via measurements of intensity correlation functions or of statistical moments. However, there has still been no test of the conceptually very simple situation dealing with single- photon states of the light impinging on a beam splitter. In this case, quantum mechanics predicts a perfect anticorrelation for photodetections on both sides of the beam splitter (a single-photon can only be detected once!), while any description involving classical fields would predict some amount of coincidences. In the first part of this letter, we report on an experiment close to this ideal situation, since we have found a coincidence rate, on both sides of a beam splitter, five times smaller than the classical lower limit. When it comes to single-photon states of light, it is tempting to revisit the famous historical .single-photon interference experiments. (8). One then finds that, in spite of their
840 citations
TL;DR: This work gives a simple annealed approximation which predicts K = 2 as the critical value of K and gives also quantitative predictions for distances between iterated configurations.
Abstract: Kauffman's model is a random complex automata where nodes are randomly assembled. Each node σi receives K inputs from K randomly chosen nodes and the values of σi at time t + 1 is a random Boolean function of the K inputs at time t. Numerical simulations have shown that the behaviour of this model is very different for K > 2 and K ≤ 2. It is the purpose of this work to give a simple annealed approximation which predicts K = 2 as the critical value of K. This approximation gives also quantitative predictions for distances between iterated configurations. These predictions agree rather well with the numerical simulations. A possible way of improving this annealed approximation is proposed.
662 citations
TL;DR: The dual string theories of everything, being purely geometrical, contain only two fundamental constants: c, for relativistic invariance, and a length λ, for quantization as discussed by the authors.
Abstract: Dual string theories of everything, being purely geometrical, contain only two fundamental constants: c, for relativistic invariance, and a length λ, for quantization. Planck's and Newton's constants appear only through Planck's length, a "calculable" fraction of λ. Only the existence of a light sector breaks a "reciprocity" principle and unification at λ, which is also the theory's cut-off.
561 citations
TL;DR: The 3D Navier-Stokes equations were obtained from two different lattice gas models as mentioned in this paper, one having its sites on a cubic lattice and particle speeds zero, one and √ 2.
Abstract: The 3D Navier-Stokes equations are obtained from two different lattice gas models The first one has its sites on a cubic lattice and has particle speeds zero, one and √2 The second one is a 3D projection of a lattice gas implementation of the 4D Navier-Stokes equations, residing on a face-centred hypercubic lattice
309 citations
TL;DR: In this article, it was shown that the effective active transmission channels are associated with the eigenvalues of a large random matrix which are closest to unity, and that a decreasing number of those survives when the system's length increases.
Abstract: The transport through a segment of a disordered system is determined by the eigenvalues of a large random matrix. The effectively independent active transmission channels are associated with these eigenvalues which are closest to unity. A decreasing number of those survives when the system's length increases. They determine the conductance and its fluctuations, which are found to be independent, within broad limits, of the size, disorder and nature of the system. This universality is due to the strong correlations in the spectra of large random matrices, providing a new insight on and generalizing the extremely interesting recent results of Altschuler, Lee and Stone.
277 citations
TL;DR: In this article, the authors describe homogeneous, isotropic, three-dimensional turbulence in a dilute solution of neutral, flexible chains, and define a critical concentration, which depends on both polymer and flow parameters.
Abstract: We describe homogeneous, isotropic, three-dimensional turbulence in a dilute solution of neutral, flexible chains. Energy flows by the usual cascade down to a scale r* such that the shear rates U(r*)/r* (U being the velocity) become equal to the relaxation rate of one coil. At small scales r, the molecules follow affinely the deformation of a local volume element. At a certain smaller scale r** the elastic stresses in the coils become comparable to the Reynolds stresses. The polymer truncates the cascade when r** becomes larger than the usual Kolmogorov limit rk. This defines a critical concentration, which depends on both polymer and flow parameters.
227 citations
TL;DR: A general formulation allows for an exploration of some basic issues in learning theory and two learning schemes are constructed, which avoid the overloading deterioration and keep learning and forgetting, with a stationary capacity.
Abstract: One characteristic behaviour of the Hopfield model of neural networks, namely the catastrophic deterioration of the memory due to overloading, is interpreted in simple physical terms. A general formulation allows for an exploration of some basic issues in learning theory. Two learning schemes are constructed, which avoid the overloading deterioration and keep learning and forgetting, with a stationary capacity.
203 citations
TL;DR: In this paper, the authors performed scanning-tunneling-microscopy (STM) experiments on cleaved graphite surfaces, and obtained a lateral resolution of better than 2 A.
Abstract: We performed scanning-tunneling-microscopy (STM) experiments on cleaved graphite surfaces. STM clearly distinguishes between the inequivalent carbon sites, and yields an energy selective density-of-states corrugation in qualitative agreement with recent theory. A lateral resolution of better than 2 A was achieved. The experiments further confirm directly the atomic flatness of some thousand angstrom size areas of cleaved graphite.
197 citations
TL;DR: This work considers the random Boolean networks suggested by Kauffman mostly on a square lattice with nearest-neighbour interactions, and finds the phase transition observed in the overlap of configurations differing in the initial conditions is related to directed percolation on the body-centred cubic lattice.
Abstract: In the random Boolean networks suggested by Kauffman, each site is changed to random rules depending on neighbours of this site. One can define two kinds of models, the annealed for which the random rules are changed at each time step, and the quenched for which the random rules remain fixed. We consider this model mostly on a square lattice with nearest-neighbour interactions. In the annealed case the phase transition observed in the overlap of configurations differing in the initial conditions is related to directed percolation on the body-centred cubic lattice; in the quenched case, the original Kauffman model, the phase transition is seen in the variation of this final overlap with the initial overlap.
180 citations
TL;DR: The random sequence of pulses given by a photodetector recording the fluorescence light emitted by a single atom can exhibit periods of darkness if two transitions, one weak and one strong, are simultaneously driven (Dehmelt's electron shelving scheme) as discussed by the authors.
Abstract: The random sequence of pulses given by a photodetector recording the fluorescence light emitted by a single atom can exhibit periods of darkness if two transitions, one weak and one strong, are simultaneously driven (Dehmelt's electron shelving scheme). We introduce new statistical functions for characterizing these periods of darkness (average length, repetition rate) and we show how to extract spectroscopic information from this type of signals.
172 citations
TL;DR: A new method is introduced, which does not use replicas, from which all the results of the replica symmetry-breaking solution of the Sherrington-Kirkpatrick model are recovered.
Abstract: We introduce a new method, which does not use replicas, from which we recover all the results of the replica symmetry-breaking solution of the Sherrington-Kirkpatrick model.
TL;DR: In this paper, it was shown that a solution of f-armed star polymers develops a peak in its scattering structure function S(q), whose height scales as f3/2.
Abstract: We show that a solution of f-armed star polymers develops a peak in its scattering structure function S(q), whose height scales as f3/2. The peak is largest when the separation between neighboring stars is about equal to the radius of a star. Our results follow from general scaling properties of polymers in a good solvent. We predict crystalline ordering of the polymers when the functionality f exceeds a universal threshold fc.
TL;DR: In this article, the matching problem and the travelling salesman problem are investigated in very high dimensions using mean-field equations valid for one given sample, and the same results of the replica approach are consistently found.
Abstract: The matching problem and the travelling salesman problem are investigated in very high dimensions using mean-field equations valid for one given sample. The same results of the replica approach are consistently found. Some applications of these results to the two-dimensional case are briefly discussed.
TL;DR: In this article, the integro-differential equation giving the shape of steady dendrites growing from a weakly undercooled melt in two spatial dimensions has been analyzed and a generalized WKB method has been used to show that solutions at small velocities can exist with anisotropic surface tension only.
Abstract: We analyse the integro-differential equation giving the shape of steady dendrites growing from a weakly undercooled melt in two spatial dimensions. A generalized WKB method shows that solutions at small velocities can exist with anisotropic surface tension only, a result completely out of reach of regular perturbation theory.
TL;DR: In this paper, a WKB formalism is presented to describe the quantum dynamics, including tunnelling, of a single spin with large spin quantum number, which is of particular relevance to the treatment of Hamiltonians with large anisotropy.
Abstract: A WKB formalism is presented to describe the quantum dynamics, including tunnelling, of a single spin with large spin quantum number. This is of particular relevance to the treatment of Hamiltonians with a large anisotropy. For a wide class of Hamiltonians we obtain the eigenstates and tunnelling rates and show the universal dependence of the latter upon the spin quantum number, anisotropy and transverse fields.
TL;DR: In this paper, a scaling analysis of the ageing process has been applied and the curves obtained for different waiting times could be superimposed on a unique master curve, which defines the response function of the system for a given age.
Abstract: The time decay of the thermoremanent magnetization has been measured in Ag:Mn (2.6%) below Tg for a wide range of waiting and observation times. A scaling analysis of the ageing process has been applied and the curves obtained for different waiting times could be superimposed on a unique master curve. At each temperature, the master curve defines the response function of the system for a given age. At very small fields, this response function is well represented by the product of a power law and a stretched exponential.
TL;DR: In this paper, the authors correct an earlier theory of polymer diffusion for a mixture of long (L) and short (S) chains in a melt, all chains being chemically identical, and they find that the overall density of the mixture remains constant everywhere, and the process has nothing to do with an uneven distribution of vacancies.
Abstract: We correct an earlier theory of polymer diffusion for a mixture of long (L) and short (S) chains in a melt, all chains being chemically identical. The mixing can be understood by analogy with the kinetics of polymer dissolution: up to a time τL (the reptation time of the L component) the L chains behave like a gel, progressively swollen by the S chains. Marker particles cannot move with respect to the gel, and follow its boundary displacement x(t). We find x(t) ~ (DSt)1/2 in agreement with a number of recent data. But the overall density of the mixture remains constant everywhere, and the process has nothing to do with an uneven distribution of vacancies.
TL;DR: In this article, the free energy and spectrum of the transfer matrix are modified in a specific way for nonunitary conformal invariant 2D systems with the Lee-Yang edge singularity.
Abstract: Finite-size effects for the free energy as well as the spectrum of the transfer matrix are modified in a specific way for nonunitary conformal invariant 2d-systems. We illustrate this behaviour in the case of the Lee-Yang edge singularity.
TL;DR: The Hopfield model of a neural network is studied for p = αN, where p is the number of memorized patterns and N thenumber of neurons, and it is shown that the critical value of α increases from 0.138 to 0.144, in excellent agreement with simulation results.
Abstract: The Hopfield model of a neural network is studied for p = αN, where p is the number of memorized patterns and N the number of neurons. The averaging over the quenched randomness is performed with the replica method, with replica symmetry broken once. It is shown that the critical value of α increases from 0.138 to 0.144, in excellent agreement with simulation results. For 0.138 < α ≤ 0.144 retrieval states exist only with replica symmetry breaking. Wherever the difference between the replica symmetric solution and the broken symmetry solution is numerically detectable, symmetry breaking improves the retrieval. At αc the number of errors decreases from 1.5% to 0.9%.
IBM1
TL;DR: In this article, a simple decoration of the Penrose tiling is used to produce a two-dimensional quasi-crystalline model, which undergoes a first-order transition to the liquid phase.
Abstract: We propose a simple decoration of the Penrose tiling to produce a two-dimensional quasi-crystalline model. We have used molecular dynamics simulation to invesigate the stability and the phase transitions of this system. Stable with pair potentials, it undergoes a first-order transition to the liquid phase. Its enthalpy is below the enthalpy of the quenched glassy state.
TL;DR: In this paper, Giaever-type superconducting tunnelling junctions are shown to be sensitive to the ionization energy of low-energy X-ray photons.
Abstract: Giaever-type superconducting tunnelling junctions are shown to be sensitive to the ionization energy of low-energy X-ray photons. The Mn Kα and Mn Kβ photons from a 55Fe source were detected with an energy resolution of 90 eV (FWHM) at an energy of 5.89 keV. The operating temperature of the detector (Sn/Sn-oxide/Sn junctions on a quartz substrate) was 0.32 K. At a fixed bias voltage, pulses from both film of the junction were observed to have the same sign. With a silicon substrate, most of the pulses originate, via phonon back scattering, from X-ray photons interacting in the substrate. Quasi-particle diffusion is essential in explaining the observed data. The main features of this detector are well described by dynamical Cooper-pair breaking and the relaxation mechanisms of nonequilibrium superconductivity.
TL;DR: In this article, the authors show that the Hall effect is primarily due to skew scattering, and that at low temperature the Hall constant increases rapidly above its residual value and is associated with the development of skew scattering by fluctuations about the coherent state.
Abstract: Hall-effect measurements are presented on four heavy-fermion systems: UPt3, UAl2, CeAl3, CeRu2Si2. We show that the Hall effect is primarily due to skew scattering. At low temperature the Hall constant increases rapidly above its residual value and is associated with the development of skew scattering by fluctuations about the coherent state. At high temperatures, in the regime of incoherent resonant scattering, the Hall effect is accounted for properly by single-impurity models of skew scattering.
TL;DR: In this article, thin-film superconducting tunnel junctions (Sn/SnOx/Sn) operated at a temperature of 0.3 K were irradiated by a 55Fe X-ray source.
Abstract: Thin-film superconducting tunnel junctions (Sn/SnOx/Sn) operated at a temperature of 0.3 K were irradiated by a 55Fe X-ray source. Pulses due to photo-absorption in the devices were observed and the Mn Kα, Kβ lines at 5.89 keV and 6.49 keV, respectively, could clearly be resolved by pulse-height analysis. An energy resolution of ΔE(FWHM) = 250 eV was obtained in the first tests reported here. Improvements may be possible by straightforward techniques.
TL;DR: In this paper, Saffman-Taylor experiments are conducted in a circular axisymmetric Hele-Shaw cell and it is shown that when a small pre-existent isolated bubble comes into contact with the tip of a finger, this finger starts growing faster, its radius of curvature at the extremity is reduced, and it takes a parabolic shape.
Abstract: Saffman-Taylor experiments are conducted in a circular axisymmetric Hele-Shaw cell. We show that when a small pre-existent isolated bubble comes into contact with the tip of a finger, this finger starts growing faster, its radius of curvature at the extremity is reduced, and it takes a parabolic shape. When its velocity is large, this finger is affected by dendritic instabilities. Although they occur here in an isotropic system, these dendrites are directly comparable to those observed in crystallization fronts.
TL;DR: In this paper, the authors compared photon emission in nucleus-nucleus collisions at intermediate beam energies (0.3 ≤ β ≤ 0.4) with pion production in the early phase of the collision and showed that photon production corresponds to a rather sudden slowing down of the relative motion.
Abstract: Direct photon emission observed in nucleus-nucleus collisions at intermediate beam energies (0.3 ≤ β ≤ 0.4) shows some very interesting features, especially when comparing it to pion production in such collisions. Valuable information is gained through the fit of a standard black-body radiation formula to the data as well as by a comparison to classical bremsstrahlung theory. A photon production in the early phase of the collision is indicated; in the bremsstrahlung picture this corresponds to a rather sudden slowing down of the relative motion.
TL;DR: In this paper, it was shown that there is a universality of constants appearing as amplitudes in the scaling laws for the correlation length and the radius of gyration in the semi-dilute regime of polymer solutions in good solvents.
Abstract: Recent experiments suggest a universality of constants appearing as amplitudes in the scaling laws for the correlation length and the radius of gyration in the semi-dilute regime of polymer solutions in good solvents. We discuss how these amplitudes can be estimated from the direct renormalization theory of polymer solutions. The obtained values are in good agreement with recent experimental measurements.
TL;DR: In this paper, small-capacitance junctions driven by a weak external current Ix exhibit oscillations of the voltage with fundamental frequencies f2 ǫ = Ix/2e or f1ǫ= Ix /e, thus reversing the role of current and voltage in comparison to the usual a.c. Josephson effect.
Abstract: Small-capacitance junctions driven by a weak external current Ix may exhibit oscillations of the voltage with fundamental frequencies f2 = Ix/2e or f1 = Ix/e, thus reversing the role of current and voltage in comparison to the usual a.c. Josephson effect. These Bloch oscillations reflect the properties of the energy bands En(Qx), where Qx is an external charge, and thus demonstrate the macroscopic quantum-mechanical nature of the system. Cooper pair tunnelling by itself would lead to 2e-periodic energy bands and band gaps. Quasi-particle tunnelling makes the bands e-periodic, but opens no further gaps. Depending on the strength of this process, the bands are qualitatively modified, with a phase transition occurring at a critical strength. The spectrum of the voltage oscillations reflects these modifications and the phase transition.
TL;DR: In this article, a direct calculation of the properties of polymer chains near the tricritical point is presented, for space dimensions d?
Abstract: We present here the results of a direct calculation of the properties of polymer chains near the ?-tricritical point, i.e. in a poor solvent, a problem which has been the subject of contradictory studies. We have devised for this (to all orders) a direct renormalization method. We find, for space dimensions d?
TL;DR: In this article, the scaling formulae for the scattering intensity from colloidal grains carrying a diffuse adsorbed layer were constructed in the most relevant regime, where q-1 is larger than a monomer size a, but smaller than a coil size R.
Abstract: The scattering intensity, from colloidal grains carrying a diffuse adsorbed layer, contains two components: one (Ī (q)) is due to the average concentration profile, and has been considered by the British school; the other component Ī (q) is due to fluctuations in the adsorbed layer. For neutral, flexible, chains, adsorbed from a good solvent, the adsorbed layer is self-similar and should show strong fluctuations. We construct scaling formulae for Ī and Ī in the most relevant regime, where q-1 is larger than a monomer size a, but smaller than a coil size R. For matched grains (no contrast between solvent and grain) the fluctuation effects are sizeable, and scattering is not a very good probe of the inner structure of the adsorbed layer. With mismatched grains, the fluctuation effects are relatively unimportant, and the structure of the average profile should show up as a correction to the Porod law, proportional to q-8/3.
TL;DR: In this paper, a one-parameter scaling theory is proposed to reduce the continuous distribution of lengths in a many-channel disordered system of transverse length l to a single scaling length.
Abstract: Transmission through a many-channel disordered system of transverse length l is governed by a set of localization lengths which converges towards a limiting distribution when l goes to infinity. Nevertheless, this continuous distribution of lengths can be reduced to a single scaling length, in agreement with a one-parameter scaling theory.