We present a link between the theory of deep water waves and that of bubble surface perturbations. Theory correspondence is shown analytically for small wavelengths in the linear regime and investigated numerically in the nonlinear regime. To do so, we develop the second-order spatial perturbation equations for the Rayleigh-Plesset equation and solve them numerically. Our code is publicly available. Studying capillary waves on stable bubbles, we recreate the Kolmogorov-Zakharov spectrum predicted by weak turbulence theory, putting wave turbulence theory to use for bubbles. In this investigation, it seems that curvature does not affect turbulent properties. The calculated bubble surface responds qualitatively to low gravity experiments. The link demonstrated opens new possibilities for studying several bubble phenomena, including sonoluminescence and cavitation, using the extensive tools developed in the wave turbulence framework.

To describe the dynamics of social distancing during pandemics, we follow previous efforts to combine basic epidemiology models (e.g. SIR — Susceptible, Infected, and Recovered) with game and economic theory tools. We present an extension of the SIR model that predicts a series of discontinuous transitions in social distancing. Each transition resembles a phase transition of the second-order (Ginzburg–Landau instability) and, therefore, potentially a general phenomenon. The first wave of COVID-19 led to social distancing around the globe: severe lockdowns to stop the pandemic were followed by a series of lockdown lifts. Data analysis of the first wave in Austria, Israel, and Germany corroborates the soundness of the model. Furthermore, this work presents analytical tools to analyze pandemic waves, which may be extended to calculate derivatives of giant components in network percolation transitions and may also be of interest in the context of crisis formation theories.

The 1st wave of COVID-19 changed social distancing around the globe: severe lockdowns to stop pandemics at the cost of state economies preceded a series of lockdown lifts. To understand social distancing dynamics it is important to combine basic epidemiology models for viral unfold (like SIR) with game theory tools, such as a utility function that quantifies individual or government forecast for epidemic damage and economy cost as the functions of social distancing. Here we present a model that predicts a series of discontinuous transitions in social distancing after pandemics climax. Each transition resembles a phase transition and, so, maybe a general phenomenon. Data analysis of the first wave in Austria, Israel, and Germany corroborates the soundness of the model. Besides, this work presents analytical tools to analyze pandemic waves.

In an iterated two-person game, for instance prisoner's dilemma or the snowdrift game, there exist strategies that force the payoffs of the opponents to be equal. These equalizer strategies form a subset of the more general zero-determinant strategies that unilaterally set the payoff of an opponent. Achallenge in the attempts to understand the role of these strategies in the evolution of animal behavior is the lack of iterations in the fights for mating opportunities or territory control. We show that an arbitrary two-parameter strategy may possess a corresponding equalizer strategy which produces the same result: statistics of the fight outcomes in the contests with competitors are the same for each of these two strategies. Therefore, analyzing only the equalizer strategy space may be sufficient to predict animal behavior if nature, indeed, reduces (marginalizes) complex strategies to equalizer strategy space. The work's main finding is that there is a unique equalizer strategy that predicts fight outcomes without symmetric cooperation responses. The lack of symmetric cooperation responses is a common trait in conflict escalation contests that generally require a clear winner. In addition, this unique strategy does not assess information of the opponent's state. The method bypasses the standard analysis of evolutionary stability. The results fit well the observations of combat between male bowl and doily spiders and support an empirical assumption of the war of attrition model that the species use only information regarding their own state during conflict escalation.

Intending to solve the decade old problem of solar opacity, we report substantial photoabsorption uncertainty due to the effect of ion-ion correlations. By performing detailed opacity calculations of the solar mixture, we find that taking into account the ionic structure changes the Rosseland opacity near the convection zone by about 10%. We also report about 15% difference in the Rosseland opacity for iron, which was recently measured at the Sandia Z facility, where the temperature reached that prevailing in the convection zone boundary while the density is 2.5 times lower. Finally, we propose a method to measure opacities at solar temperatures and densities that were never reached in the past via laboratory radiation flow experiments, by using plastic foams doped with permilles of dominant photon absorbers in the Sun. The method is advantageous for an experimental study of solar opacities that may lead to a resolution of the solar problem.

We present opacity calculations with the newly developed STAR code, which implements the Super-Transition-Array (STA), with various improvements. The model is used to calculate and analyze local thermodynamic equilibrium opacities of mid and high Z elements and of the solar interior plasma. We briefly review the underlying computational model and present calculations for iron and neodymium over a wide range of temperature and density.

Observations of animal contests pose a question whether the decision to quit the fight depends on the own state of the player (self-assessment) or on a state of the opponent (mutual assessment). We argue that conflict escalation, e.g. the snowdrift game or war of attrition, makes possible only the evolution of self-assessment. No constraint for the evolution of mutual assessment was found for social Prisoneru0027s Dilemma. Previous studies, to the best of our knowledge, postulated self-assessment as a constraint, e.g. in the war of attrition model, due to empirical evidence of neglecting information of the opponentu0027s state during the mating combats of some species. We show that an evolutionary stable strategy of a binary game may possess an indistinguishable recently discovered coercive zero-determinant strategy. Analysis of this indistinguishable iterated strategy, under specific circumstances, reveals the evolutionary stable mechanism of assessment. The theoretical predictions of this work are verified using statistical data of mating combats between specimens of male bowl and doily spiders.

Out of thermal equilibrium, an environment imposes effective mechanical forces on nanofabricated devices as well as on microscopic chemical or biological systems. Here we address the question of how to calculate these forces together with the response of the system from first principles. We show that an ideal gaslike environment, even near thermal equilibrium, can enforce a specific steady state on the system by creating effective potentials in otherwise homogeneous space. An example of stable and unstable rectifications of thermal fluctuations is presented using a modified Feynman-Smoluchowski ratchet with two degrees of freedom. Moreover, the stability of a steady configuration depends on its chiral symmetry. The transition rate probabilities and the corresponding kinetic equations are derived for a complex mechanical system with arbitrary degrees of freedom. This work, therefore, extends the applicability of mechanical systems as a toy model playground of statistical physics for active and living matter with multiple degrees of freedom.

ABSTRACT A new opacity model has been developed based on the Super-Transition-Array (STA) method for the calculation of monochromatic opacities of plasmas in local thermodynamic equilibrium. The atomic code, named STAR (STA-Revised), is described and used to calculate spectral opacities for a solar model implementing the recent AGSS09 composition. Calculations are carried out throughout the solar radiative zone. The relative contributions of different chemical elements and atomic processes to the total Rosseland mean opacity are analyzed in detail. Monochromatic opacities and charge-state distributions are compared with the widely used Opacity Project (OP) code, for several elements near the radiation–convection interface. STAR Rosseland opacities for the solar mixture show a very good agreement with OP and the OPAL opacity code throughout the radiation zone. Finally, an explicit STA calculation was performed of the full AGSS09 photospheric mixture, including all heavy metals. It was shown that, due to their extremely low abundance, and despite being very good photon absorbers, the heavy elements do not affect the Rosseland opacity.

Human-created engines and evolutionarily optimized molecular motors exhibit sophisticated design in order to harvest chemical or thermal energy for generating unidirectional motion. The complexity of these motors makes their random emergence unlikely. Molecules capable of locomotion, however, seem to be essential to the creation of the first self-replicator and initiation of Darwinian evolution, posing a question of the physical mechanism that can facilitate emergence of directed motion in an isotropic environment. Here we show a universal thermodynamic mechanism for spontaneous emergence of motor abilities in a mechanical system. A non-equilibrium system with multiple degrees of freedom develops symmetry breaking that favors rectification of environmental thermal fluctuations. The corresponding velocities and its fluctuations are calculated. Homochirality of living matter is explained as chirality breaking resulting from the emergence of a motor. Universality of the results provides a general extension of the Onsager relations to the non-linear regime.

The calculation of line widths constitutes theoretical and computational challenges in the calculation of opacities of hot dense plasmas. Opacity models use line broadening approximations that are untested at stellar interior conditions. Moreover, calculations of atomic spectra of the sun, indicate a large discrepancy in the K-shell line widths between several atomic codes and the OP. In this work, the atomic code STAR is used to study the sensitivity of solar opacities to line-broadening. Variations in the solar opacity profile, due to an increase of the Stark widths resulting from discrepancies with OP, are compared, in light of the solar opacity problem, with the required opacity variations of the present day sun, as imposed by helioseismic and neutrino observations. The resulting variation profile, is much larger than the discrepancy between different atomic codes, agrees qualitatively with the missing opacity profile, recovers about half of the missing opacity nearby the convection boundary and has a little effect in the internal regions. Since it is hard to estimate quantitatively the uncertainty in the Stark widths, we show that an increase of all line widths by a factor of about 100 recovers quantitatively the missing opacity. These results emphasize the possibility that photoexcitation processes are not modeled properly, and more specifically, highlight the need for a better theoretical characterization of the line broadening phenomena at stellar interior conditions and of the uncertainty due to the way it is implemented by atomic codes.

Social susceptibility is defined and analyzed using data from CNN news website. The current models of opinion dynamics, voting, and herding in closed communities are extended, and the community's response to the injection of a group with predetermined and permanent opinions is calculated. A method to estimate the values of possible response in Internet communities that follow a specific developing subject is developed. The level of social influence in a community follows from the statistics of responses ("like" and "dislike" votes) to the comments written by the members of the same community. Three real cases of developing news stories are analyzed. We suggest that Internet comments may predict the level of social response similar to a barometer that predicts the intensity of a coming storm in still calm environment.

Generalized analytical expressions for the two-electron relativistic Unresolved-Transition-Array (UTA) energy variance and shift for electric and magnetic transitions of general multipole order are presented. The revised expressions are shown to agree with the exact moments calculated directly from the energy levels of two-electron configurations. We show that for electric transitions of even multipole order and for magnetic transitions, the available expressions in the literature, which are implemented in widely used atomic codes, are incorrect. We suggest an alternative method for the calculation of the UTA energy variance and shift by using the analytical expressions for the two-electron energy levels and line-strengths. The method is much more efficient and simple than the use of the traditional lengthy analytic expressions. Finally, the effect of UTA widths on Super-Transition-Array (STA) spectral opacity is shown for several examples.

We have recently completed developing a new super transition array (STA) code for calculating absorption and emission spectra of LTE plasmas. The code follows the theory of Bar-Shalom et al. with various improvements. In this work we focus on the first order correction for the Boltzmann populations for which traditional calculations can be very costly. We present here a method faster by an order of magnitude than the traditional method. We then investigate the effect of this correction on the opacity spectra of several elements. Finally we interpret results of a recent opacity experiment on gold plasma. A good agreement is reached.

We have recently completed developing a new super transition array (STA) code for calculating absorption and emission spectra of LTE plasmas. The code follows the theory of Bar-Shalom et al. with various improvements. In this work we focus on the first order correction for the Boltzmann populations for which traditional calculations can be very costly. We present here a method faster by an order of magnitude than the traditional method. We then investigate the effect of this correction on the opacity spectra of several elements. Finally we interpret results of a recent opacity experiment on gold plasma. A good agreement is reached.

The dynamics of market prices is described as the evolution of opinions in the trading community regarding future market behavior. The price then is a function of the voting process of the market players in favor to raise or reduce the value of a stock. The model presented in this paper is suited for pricing of options and was verified against real market data. The model allows deriving the parameters of market players from available real market data, especially maximum possible correlation (herding) and anti-correlation between the players' opinions. The deviations of market prices from those predicted by the Black-Scholes model, such as smile and skew implied volatilities, are interpreted as the current values and limits of social influence of the market players, respectively. To the best of our knowledge, this is the first work that discriminates skew and smile phenomena. Our approach unifies and develops a further connection between trading, voters' model, and statistical physics analogies of opinion dynamics.

Emergence, optimization and stability of a motor-like motion in a fluctuating environment are analyzed. The emergence of motion is shown to be a general phenomenon. A motor converges to the state with the minimum of effective temperature and with the corresponding minimum in the rate of conformation changes similarly as some stochastic processes converge to the states with minimum diffusion activity. This mechanism is important to bacterial foraging (chemotaxis). This work, therefore, raises an analogy between chemotaxis and the emergence of living-like systems. The implications include the deviation of stable natural or artificial machines from the minimum entropy production principle, with a novel self-assembly mechanism for the emergence of the first molecular motors and for mass fabrication of the future nanodevices.

Introduction: EphB4, a receptor tyrosine kinase, is a marker of venous identity in adult veins that also controls wall thickness during vein graft adaptation to the arterial environment. Since the role of endothelial nitric oxide synthase (eNOS) in vein graft adaptation is not well understood, we evaluated whether eNOS is a downstream effector of EphB4 mediated signaling that controls vein graft thickness. Methods: Intrathoracic inferior vena cava was harvested from wild-type (WT) or eNOS knockout (KO) mice and placed as an interposition vein graft into the infrarenal aorta of WT mice. Vein graft thickness was assessed weekly by ultrasound. After 3 weeks, vein grafts were harvested and analyzed by histology. EphB4 was activated in WT or Akt-KO mouse lung endothelial cells (MLEC) in vitro using the bivalent ligand Ephrin-B2/Fc in a time course fashion for up to 60 minutes. Cell lysates were examined via Western blotting for differences in eNOS-phosphorylation. in some experiments WT MLECs were pre-treated with Wortmannin for 60 minutes prior to Ephrin-B2/Fc stimulation. EphB4 colocalization with phospho-eNOS in WT MLECs was assessed by immunofluorescence microscopy following 30 and 60 minutes of Ephrin-B2/Fc stimulation. Nitric oxide (NO) production was assessed using a NO-specific chemiluminescence analyzer. Results: Vein grafts derived from eNOS-KO mice showed significantly less wall thickening compared with WT vein grafts (n=7, p=0.04). EphB4 activation resulted in increased NO production from WT MLECs (176.0pmol vs 111.7pmol; p=<0.001; n=3) and co-localization of EphB4 with phosphorylated eNOS. Interestingly, EphB4 activation stimulated eNOS phosphorylation in a novel bimodal distribution, with maximal increases in eNOS phosphorylation at both 1 and 60 minutes (n=5; p<0.005). the initial, but not the late peak of eNOS phosphorylation was inhibited by wortmannin (n=2). Similarly, Akt-KO MLECs showed an early but not a late peak of eNOS phosphorylation (n=2). Conclusions: Eph-B4 stimulates eNOS phosphorylation in adult venous cells via a novel intracellular signaling pathway dependent on Akt. Both EphB4 and eNOS are critical for normal vein graft adaptation to the arterial circulation, and eNOS may be the mechanism by which EphB4 mediates vein graft adaptation. Selective promoters of eNOS phosphorylation may also promote normal vein graft adaptation and reduce vein graft failure.