Eur Phys Research Articles

Influence of Initial Conditions on Propagation, Growth and Decay of Saturation Overshoot

A sequence of drainage and imbibition shocks within the traditional theory of two-phase immiscible displacement can give rise to shallow non-monotone saturation profiles as shown in Hilfer and Steinle (Eur Phys J Spec Top 223:2323, 2014). This phenomenon depends sensitively on model parameters and initial conditions. The dependence of saturation overshoot on initial conditions is investigated more systematically in this article. The results allow to determine regions in the parameter space for the observation of saturation overshoot and to explore limitations of the underlying idealized hysteresis model. Numerical solutions of the nonlinear partial differential equations of motion reveal a strong dependence of the overshoot phenomenon on the boundary and initial conditions. Overshoot solutions with experimentally detectable height are shown to exist numerically. Extensive parameter studies reveal different classes of initial conditions for which the width of the overshoot region can decrease, increase or remain constant.

Renormalization scheme dependence of the two-loop QCD corrections to the neutral Higgs-boson masses in the MSSM.

Reaching a theoretical accuracy in the prediction of the lightest MSSM Higgs-boson mass, M_h, at the level of the current experimental precision requires the inclusion of momentum-dependent contributions at the two-loop level. Recently two groups presented the two-loop QCD momentum-dependent corrections to M_h (Borowka et al., Eur Phys J C 74(8):2994, 2014; Degrassi et al., Eur Phys J C 75(2):61, 2015), using a hybrid on-shell-overline{mathrm {DR}} scheme, with apparently different results. We show that the differences can be traced back to a different renormalization of the top-quark mass, and that the claim in Ref. Degrassi et al. (Eur Phys J C 75(2):61, 2015) of an inconsistency in Ref. Borowka et al. (Eur Phys J C 74(8):2994, 2014) is incorrect. We furthermore compare consistently the results for M_h obtained with the top-quark mass renormalized on-shell and overline{mathrm {DR}}. The latter calculation has been added to the FeynHiggs package and can be used to estimate missing higher-order corrections beyond the two-loop level.

Well-posedness of a two-scale model for liquid phase epitaxy with elasticity

Epitaxy, a special form of crystal growth, is a technically relevant process for the production of thin films and layers. It can generate microstructures of different morphologies, such as steps, spirals or pyramids. These microstructures are influenced by elastic effects in the epitaxial layer. There are different epitaxial techniques, one being liquid phase epitaxy. Thereby, single particles are deposited out of a supersaturated liquid solution on a substrate where they contribute to the growth process. This article studies a two-scale model including elasticity, introduced in Eck et al. (Eur Phys J Special Topics 177:5–21, 2009) and extended in Eck et al. (2006). It consists of a macroscopic Navier–Stokes system and a macroscopic convection–diffusion equation for the transport of matter in the liquid, and a microscopic problem that combines a phase field approximation of a Burton–Cabrera–Frank model for the evolution of the epitaxial layer, a Stokes system for the fluid flow near the layer and an elasticity system for the elastic deformation of the solid film. Suitable conditions couple the single parts of the model. As the main result, existence and uniqueness of a solution are proven in suitable function spaces. Furthermore, an iterative solving procedure is proposed, which reflects, on the one hand, the strategy of the proof of the main result via fixed point arguments and, on the other hand, can be the basis for a numerical algorithm.

CGC/saturation approach for soft interactions at high energy: a two channel model

In this paper we continue the development of a model for strong interactions at high energy, based on two ingredients: the CGC/saturation approach and the BFKL Pomeron. In our approach, the unknown mechanism of confinement of quarks and gluons is characterized by several numerical parameters, which are extracted from the experimental data. We demonstrate that the two channel model successfully describes the experimental data, including both the value of the elastic slope and the energy behavior of the single diffraction cross section. We show that the disagreement with the experimental data of our previous single channel eikonal model (Gotsman et al., Eur Phys J C 75:1–18, 2015) stems from the simplified approach used for the hadron structure and is not related to our principal theoretical input, based on the CGC/saturation approach.

On generalized logarithmic electrodynamics

The generalized logarithmic electrodynamics with two parameters \(\beta \) and \(\gamma \) is considered. The indexes of refraction of light in the external magnetic field are calculated. In the case \(\beta =\gamma \) we come to results obtained by Gaete and Helayël-Neto (Eur Phys J C 74:2816, 2014). The bound on the values of \(\beta \), \(\gamma \) was obtained from the Biréfringence Magnétique du Vide (BMV) experiment. The symmetrical Belinfante energy-momentum tensor and dilatation current are found.

A note on “Electron self-energy in logarithmic electrodynamics” by P. Gaete and J. Helayël-Neto

We propose an identification of the free parameter in the model of nonlinear electrodynamics proposed in Gaete and Helayël-Neto (Eur Phys J C 74:2816, 2014) by equating the second term in the power expansion of its Lagrangian with that in the expansion of the Heiseberg–Euler Lagrangian. The resulting value of the field-energy of a point-like charge makes 0.988 of the electron mass, if the charge is that of the electron.

Ising Critical Exponents on Random Trees and Graphs

We study the critical behavior of the ferromagnetic Ising model on random trees as well as so-called locally tree-like random graphs. We pay special attention to trees and graphs with a power-law offspring or degree distribution whose tail behavior is characterized by its power-law exponent τ > 2. We show that the critical inverse temperature of the Ising model equals the hyperbolic arctangent of the reciprocal of the mean offspring or mean forward degree distribution. In particular, the critical inverse temperature equals zero when \({\tau \in (2,3]}\) where this mean equals infinity.We further study the critical exponents δ, β and γ, describing how the (root) magnetization behaves close to criticality. We rigorously identify these critical exponents and show that they take the values as predicted by Dorogovstev et al. (Phys Rev E 66:016104, 2002) and Leone et al. (Eur Phys J B 28:191–197, 2002). These values depend on the power-law exponent τ, taking the same values as the mean-field Curie-Weiss model (Exactly solved models in statistical mechanics, Academic Press, London, 1982) for τ > 5, but different values for \({\tau \in (3,5)}\) .

Translationally Invariant Calculations of Form Factors, Densities and Momentum Distributions for Finite Nuclei with Short–Range Correlations Included: A Fresh Look

The approach proposed in the 70s (Dementiji et al. in Sov J Nucl Phys 22:6–9, 1976), when describing the elastic and inelastic electron scattering off 4He, and elaborated in (Shebeko et al.in Eur Phys J A27:143–155, 2006) for calculations of the one-body, two-body and more complex density matrices of finite bound systems has been applied (Shebeko and Grigorov in Ukr J Phys 52:830–842, 2007; Shebeko et al. in Eur. Phys. J. A48:153–172, 2012) in studying a combined effect of the center-of-mass motion and nucleon–nucleon short-range correlations on the nucleon density and momentum distributions in light nuclei beyond the independent particle model. Unlike a common practice, suitable for infinite bound systems, these distributions are determined as expectation values of appropriate intrinsic operators that depend upon the relative coordinates and momenta (Jacobi variables) and act on the intrinsic ground–state wave functions (WFs). The latter are constructed in the so-called fixed center-of-mass approximation, starting with a mean–field Slater determinant modified by some correlator (e.g., after Jastrow or Villars). Our numerical calculations of the charge form factors (FCH(q)), densities and momentum distributions have been carried out for nuclei 4He and 16O choosing, respectively, the 1s and 1s−1p Slater determinants of the harmonic oscillator model as trial, nontranslationally invariant WFs.

Structure of $$1$$ 1 -RSB Asymptotic Gibbs Measures in the Diluted $$p$$ p -Spin Models

In this paper we study asymptotic Gibbs measures in the diluted \(p\)-spin models in the so called \(1\)-RSB case, when the overlap takes two values \(q_*, q^*\in [0,1].\) When the external field is not present and the overlap is not equal to zero, we prove that such asymptotic Gibbs measures are described by the Mézard–Parisi ansatz conjectured in Mézard and Parisi (Eur Phys J B 20(2):217–233 2001). When the external field is present, we prove that the overlap can not be equal to zero and all \(1\)-RSB asymptotic Gibbs measures are described by the Mézard–Parisi ansatz. Finally, we give a characterization of the exceptional case when there is no external field and the smallest overlap value \(q_*=0\), although it does not go as far as the Mézard–Parisi ansatz. Our approach is based on the cavity computations combined with the hierarchical exchangeability of pure states.

Rheological properties of suspensions of the green microalga Chlorella vulgaris at various volume fractions

A systematic study of the rheological properties of solutions of non-motile microalgae (Chlorella vulgaris CCAP 211-19) in a wide range of volume fractions is presented. As the volume fraction is gradually increased, several rheological regimes are observed. At low volume fractions (but yet beyond the Einstein diluted limit), the sus- pensions display a Newtonian rheological behaviour and the volume fraction dependence of the viscosity can be well described by the Quemada model (Quemada, Eur Phys J Appl Phys 1:119-127, 1997). For intermediate values of the volume fraction, a shear thinning behaviour is observed and the volume fraction dependence of the viscosity can

Floating lipid bilayers: models for physics and biology

Progress in the determination of structure and fluctuation spectrum of a floating bilayer system, as well as potential applications for biological studies, is reviewed. The system described here was first introduced by Charitat et al. (Eur Phys J B 8:583-593, 1999) and consists of a planar bilayer floating at 2-3nm away from an adsorbed one on a solid surface in contact with bulk water. This model has been widely used for surface scattering studies using both neutrons and synchrotron radiation and its use in studies of relevance for physics and biology research areas will be described, together with the progress towards the production of complex biomimetic samples for use with scattering techniques.

Heterogeneity in the resistance to learning

In this paper we analyze the effect of heterogeneity in the recently introduced “resistance to learning” (Jimenez et al. in Eur Phys J B 71:273–280, 2009a). In the context of the spatial Continuous Prisoner’s Dilemma, the resistance to learning has become a key mechanism for the emergence and maintenance of cooperation in a wide range of cost regimes. We extend the model to the case in which different individuals may have different levels of resistance. From non-cooperative initial states, the existence of heterogeneity in the resistance affects the cooperative behavior of unconditional imitators. These unconditional imitators, i.e., fast learners or individuals without resistance can achieve due to their interactions with gradual learners significant levels of cooperation. Our results confirm in one of its form the impact of heterogeneity and its role as a fundamental mechanism in promoting the emergence of cooperation.

Neutral kaon production in p $+$ p and p $+$ Nb collisions

The kaon nucleus (KN) interaction in dense nuclear matter is predicted to be repulsive and increasing with density. However, determined values for this potential are not yet consistent with each other (Benabderrahmane et al., Phys Rev Lett 102:182501, 2009; Agakishiev et al., Phys Rev C 82:044907, 2010; Buscher et al., Eur Phys J A 22:301–317, 2004). We analyze \(K^0_S\) mesons identified with the HADES detector in p+p and p+ 93Nb reactions at 3.5 GeV kinetic beam energy. To determine the KN potential at normal nuclear density we propose to compare the \(K^0_S\) differential distributions in p+ 93Nb and p+p collisions. High statistics of low p t -kaons (p t < 100 MeV/c) ensure the sensitivity of our measurements to the nuclear matter effects. We present the data analysis method and first results.

Precursors of failure and weakening in a biaxial test

We study numerical simulations of large (\({N{\approx}10^4}\)) two-dimensional quasi-static granular assemblies subjected to a slowly increasing deviator stress. We report some peculiarities in the behavior of these packings that have not yet been addressed. The number of sliding contacts is not necessarily related to stability: first the number of sliding contacts rises linearly and smoothly with the applied stress. Then, at approximately half the peak stress, the increase slows down, a plateau develops, and a decrease follows. The spatial organization of sliding contacts also changes: during the first half of the simulation, sliding contacts are uniformly distributed throughout the packing, but in the second half, they become concentrated in certain regions. This suggests that the loss of homogeneity occurs well before the appearance of shear bands. During the second half events appear where the number of sliding contacts drops suddenly, and then rapidly recovers. We show that these events are in fact local instabilities in the packing. These events become more frequent as failure is approached. For these two reasons, we call these events precursors, since they are similar to the precursors recently observed in both numerical (Staron et al. Phys Rev Lett 89:204302, 2002; Nerone et al. Phys Rev E 67:011302, 2003) and experimental (Gibiat et al. J Acoust Soc Am 123:3142, 2009; Scheller et al. Phys Rev E 74:031311, 2006; Zaitsev et al. Eur Phys Lett 83:64003, 2008; Aguirre et al. Phys Rev E 73:041307, 2006) studies of avalanches.

The Power of Choice in the Construction of Recursive Trees

The power of choice is known to change the character of random structures and produce desirable optimization effects. We discuss generalizations of random recursive trees, grown under the choice to meet optimization criteria. Specifically, we discuss the random k-minimal (k-maximal) label recursive tree, where a set of k candidate parents, instead of one as in the usual recursive tree, is selected and the node with minimal (maximal) label among them is assigned as parent for the next node. These models are proposed as alternatives for D’Souza et al. (Eur Phys J B59:535–543, 2007) minimal and maximal depth models. The advantage of the label models is that they are tractable and at the same time provide approximations and bounds for the depth models. For the depth of nodes in label models we give the average behavior and exact distributions involving Stirling’s numbers and derive Gaussian limit laws.

Modified version of revised Deutsch–Märk model for electron impact K‐shell ionization cross‐sections of atoms at relativistic energies

AbstractA simple modification of the revised Deutsch–Märk model (RDM) [Deutsch et al., Int J Mass Spectrom 2004, 233, 13] incorporating both the ionic and relativistic corrections is proposed to investigate the K‐shell ionization of 30 atomic targets with atomic numbers Z = 1–92 for incident energies up to 2 GeV. We also revisit our earlier models: modified Bell (MBELL) (Haque et al., Phys Rev A 2006, 73, 012708) and modified Kolbenstvedt (MKLV) (Uddin et al., Eur Phys J D 2006, 37, 361), for the K‐shell ionization cross sections at these ultra‐relativistic energies. The results from the modified version of RDM (MRDM), MBELL, and MKLV models agree well with the available experimental data and quantum mechanical calculations. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009

Electron impact K‐shell ionization cross sections of atoms at relativistic energies

AbstractWe propose an extension of the modified simplified‐improved‐binary‐encounter dipole (MRIBED) model (Uddin et al., Phys Rev A 2005, 72, 032715), incorporating both the ionic and relativistic corrections, to investigate the K‐shell ionization of atomic targets with atomic numbers Z = 1 − 92 for incident energies up to 2 GeV. We also revisit our earlier models, MBELL (Haque et al. Phys Rev A 2006, 73, 012708) and MKLV (Uddin et al. Eur Phys J D 2006, 37, 361), for the K‐shell ionization at these ultra‐relativistic energies. The results from our extended version of MRIBED, MBELL, and MKLV models agree well with the experimental findings. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008

Effect of noise on fractal structure

In this paper, I investigate the effect of dynamical noise on the estimation of the Hurst exponent and the fractal dimension of time series. Recently, Serletis et al. [Serletis, Apostolos, Asghar Shahmoradi, Demitre Serletis. Effect of noise on estimation of Lyapunov exponents from a time series. Chaos, Solitons & Fractals, forthcoming] have shown that dynamical noise can make the detection of chaotic dynamics very difficult, and Serletis et al. [Serletis, Apostolos, Asghar Shahmoradi, Demitre Serletis. Effect of noise on the bifurcation behavior of dynamical systems. Chaos, Solitons & Fractals, forthcoming] have shown that dynamical noise can also shift bifurcation points and produce noise-induced transitions, making the determination of bifurcation boundaries difficult. Here I apply the detrending moving average (DMA) method, recently developed by Alessio et al. [Alessio E, Carbone A, Castelli G, Frappietro V. Second-order moving average and scaling of stochastic time series. The Eur Phys J B 2002;27:197–200] and Carbone et al. [Carbone A, Castelli G, Stanley HE. Time-dependent Hurst exponent in financial time series. Physica A 2004;344:267–71; Carbone A, Castelli G, Stanley HE. Analysis of clusters formed by the moving average of a long-range correlated time series. Phys Rev E 2004;69:026105], to estimate the Hurst exponent of a Brownian walk with a Hurst exponent of 0.5, coupled with low and high intensity noise, and show that dynamical noise has no effect on fractal structure.

Glass‐transition temperature behavior of alumina/PMMA nanocomposites

AbstractAlumina/poly(methyl methacrylate) (PMMA) nanocomposites were synthesized by an in situ free‐radical polymerization process with 38 and 17 nm diameter γ‐alumina nanoparticles. At extremely low filler weight fractions (&lt;1.0 wt % of 38 nm fillers or &lt; 0.5 wt % of 17 nm fillers) the glass‐transition temperature (Tg) of the nanocomposites drops by 25 °C when compared to the neat polymer. Further additions of filler (up to 10 wt %) do not lead to additional Tg reductions. The thermal behavior is shown to vary with particle size, but this dependence can be normalized with respect to a specific surface area. The nanocomposite Tg phenomenon is hypothesized to be because of nonadhering nanoparticles that serve as templates for a porous system with many internal interfaces that break up the percolating structure of dynamically heterogeneous domains recently suggested by Long, D.; and Lequeux, F. Eur Phys J E 2001, 4, 371 to be responsible for the Tg reductions in polymer ultrathin films. The results also point to a far field effect of the nanoparticle surface on the bulk matrix. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4371–4383, 2004