Cosmic String Universes Embedded with Viscosity

Either in societies or economic cycles, the benefits of a group can be affected by various unpredictable factors. We study effects of additive spatiotemporal random variations on the evolution of cooperation by introducing them to the enhancement level of the spatial public goods game. Players are located on the sites of a two-dimensional lattice and gain their payoffs from games with their neighbors by choosing cooperation or defection. We observe that a moderate intensity of variations can best favor cooperation at low enhancement levels, which resembles classical coherence resonance. Whereas for high enhancement levels, we find that the random variations cannot increase the cooperation level, but hamper cooperation instead. This discrepancy is attributed to the different roles the additive variations played in the early and late stages of evolution. In the early stage of evolution, the additive variations increase the survival probability of the players with lower average payoffs. However, in the late stage of evolution, the additive variations can promote defectors to destroy the cooperative clusters that have been formed. Our results indicate that additive spatiotemporal noise may not be as universally beneficial for cooperation as the spatial prisoner's dilemma game.

Context. Ultra-deep imaging of small parts of the sky has revealed many populations of distant galaxies, providing insight into the early stages of galaxy evolution. Spectroscopic follow-up has mostly targeted galaxies with strong emission lines at z > 2 or concentrated on galaxies at z < 1. Aims. The populations of both quiescent and actively star-forming galaxies at 1 < z < 2 are still under-represented in our general census of galaxies throughout the history of the Universe. In the light of galaxy formation models, however, the evolution of galaxies at these redshifts is of pivotal importance and merits further investigation. In addition, photometry provides only limited clues about the nature and evolutionary status of these galaxies.We therefore designed a spectroscopic observing campaign of a sample of both massive, quiescent and star-forming galaxies at z > 1.4. Methods. To determine redshifts and physical properties, such as metallicity, dust content, dynamical masses, and star formation history, we performed ultra-deep spectroscopy with the red-sensitive optical spectrograph FORS2 at the Very Large Telescope. We first constructed a sample of objects, within the CDFS/GOODS area, detected at 4.5 m, to be sensitive to stellar mass rather than star formation intensity. The spectroscopic targets were selected with a photometric redshift constraint (z > 1.4) and magnitude constraints (B AB < 26, I AB < 26.5), which should ensure that these are faint, distant, and fairly massive galaxies. Results. We present the sample selection, survey design, observations, data reduction, and spectroscopic redshifts. Up to 30 h of spectroscopy of 174 spectroscopic targets and 70 additional objects enabled us to determine 210 redshifts, of which 145 are at z > 1.4. The redshift distribution is clearly inhomogeneous with several pronounced redshift peaks. From the redshifts and photometry, we deduce that the BzK selection criteria are efficient (82%) and suffer low contamination (11%). Several papers based on the GMASS survey show its value for studies of galaxy formation and evolution. We publicly release the redshifts and reduced spectra. In combination with existing and on-going additional observations in CDFS/GOODS, this data set provides a legacy for future studies of distant galaxies.

A string cosmological models with magnetic field along X and Z-axis are investigated in the context of Ruban’s space time. To obtain a determinant solution, equation of state for string model and relation between metric potential is considered. The physical and geometrical aspects are also discussed.

We review the notion of the Higgs effect in the context of string theory. We find that by including this effect in time dependent backgrounds, one is led to a natural mechanism for stabilizing moduli at points of enhanced gauge symmetry. We consider this mechanism for the case of the radion (size of the extra dimensions) and find that as decompactification of the large spatial dimensions takes place the radion will remain stabilized at the self-dual radius. We discuss how this mechanism can be incorporated into models of string cosmology and brane inflation to resolve some outstanding problems. We also address some issues regarding which string states should be included when constructing low energy actions in string cosmology.

Five-dimensional space-time string cosmological models generated by a cloud of strings with particles attached to them are studied in the Brans-Dicke theory. We obtain two types of interesting models by taking up the cases of geometric strings (or Nambu strings) and p-strings (Takabayasi strings), and study their different physical and dynamical properties. The roles of the scalar field in getting different phases, such as the inflationary phase and the string-dominated phase, are discussed. An interesting feature obtained here is that in one of the models there is a “bounce" at a particular instant of its evolution.

The effect of tidal torques on rotational mixing in close binaries is investigated. It is found that spin angular momentum can attain a high value due to a strong tidal torque. Nitrogen and helium enrichment occurs early in the binary system that is triggered by tides. The stellar radius can reach a high value in the single star model with high initial velocities at the early stage of the evolution, but efficient rotational mixing can inhibit stellar expanding at the subsequent evolution. Central compactness is increased by the centrifugal force at the early stage of evolution but is reduced by rotational mixing induced by strong tides. The binary models with weak tides have high values of central temperature and stellar radius. Rotational mixing in single stars can slow down the shrinkage of convective cores, while convective cores can be expanded by strong tides in the binary system. Efficient rotational mixing induced by tides can cause the star to evolve towards high temperature and luminosity.

In the late stage of the population evolution of the RNA genetic algorithm, mutation may destroy the individual genes with higher fitness, resulting in slower convergence or no optimal solution. Therefore, this paper proposes an RNA genetic algorithm that does not add mutation operations in the late stage of evolution (Referred to as nmlsRNA-GA), in the early stage of evolution, the goal is to find the approximate location of the optimal solution. The two-point crossover and fixed-probability mutation operations are performed in the crossover pool composed of individuals with high fitness and individuals with low fitness to increase the diversity of the population. In order to improve the global search ability of the algorithm. In the later stage of the evolution, the goal is to improve the local search ability to determine the optimal solution, and use individuals with high adaptability to cross over individuals with high adaptability to generate individuals with higher adaptability, thereby improving search Accuracy, no mutation operation is added at this stage to prevent mutation from destroying excellent genes. By optimizing five typical high-dimensional test functions, and comparing them with the RNA genetic algorithm that uses mutation throughout the process, the analysis results show that the algorithm has better performance.

Dark matter axions in models of string cosmology

Within the scope of isotropic FRW cosmological model the role of nonlinear spinor field in the evolution of the Universe is studied. It is found that unlike in anisotropic cosmological models in the present case the spinor field does not possess nontrivial non-diagonal components of energy-momentum tensor, consequently does not impose any additional restrictions on the components of the spinor field or metric function. The spinor description of different matter was given and evolution of the Universe corresponding to these sources is illustrated. In the framework of a three fluid system the utility of spinor description of matter is established.

String cosmology models predict a relic background of gravitational wave produced during the dilaton-driven inflation. It's spectrum is most likely to be detected by ground gravitational wave laser interferometers (IFOs), like LIGO, Virgo, GEO, as the energy density grows rapidly with frequency. We show the certain ranges of the parameters that underlying string cosmology model using two approaches, associated with 5% false alarm and 95% detection rate. The result presents that the approach of combining multiple pairs of IFOs is better than the approach of directly combining the outputs of multiple IFOs for LIGOH, LIGOL, Virgo and GEO.

Purpose Artificial intelligence is gradually penetrating into human society. In the network era, the interaction between human and artificial intelligence, even between artificial intelligence, becomes more and more complex. Therefore, it is necessary to describe and intervene the evolution of crowd intelligence network dynamically. This paper aims to detect the abnormal agents at the early stage of intelligent evolution. Design/methodology/approach In this paper, differential evolution (DE) and K-means clustering are used to detect the crowd intelligence with abnormal evolutionary trend. Findings This study abstracts the evolution process of crowd intelligence into the solution process of DE and use K-means clustering to identify individuals who are not conducive to evolution in the early stage of intelligent evolution. Practical implications Experiments show that the method we proposed are able to find out individual intelligence without evolutionary trend as early as possible, even in the complex crowd intelligent interactive environment of practical application. As a result, it can avoid the waste of time and computing resources. Originality/value In this paper, DE and K-means clustering are combined to analyze the evolution of crowd intelligent interaction.

Petrology of Precambrian metaultramafites of the Gridino high-pressure complex ( Karelia)

In this paper, the phase separation of A, B, and C ternary mixtures coupled with the chemical reaction of A + B C is investigated numerically on the basis of the modified time-dependent Ginzburg−Landau (TDGL) equation. The simulation results showed that, depending on the rate constant of chemical reaction and the compatibility between the components, very complicated phase patterns could be obtained. It is found that when the compatibility of A and B is poor and C has good compatibility with A/B, in the early stage of phase evolution, the phase separation between A and B pushes C to the interface between A- and B-rich domains. However, when A and B are compatible while C and A/B are incompatible, in the early stage of phase evolution, C-rich spherical droplets are immersed in the A/B continuous phase. As evolution goes on, the phase separation of A and B takes place and pushes C droplets to the interface between A- and B-rich domains. It is also found that the phase evolution depends on the competition be...

Cosmic strings are generic cosmological predictions of many extensions of the standard model of particle physics, such as a $U(1{)}^{\ensuremath{'}}$ symmetry-breaking phase transition in the early Universe or remnants of superstring theory. Unlike other topological defects, cosmic strings can reach a scaling regime that maintains a small fixed fraction of the total energy density of the Universe from a very early epoch until today. If present, they will oscillate and generate gravitational waves with a frequency spectrum that imprints the dominant sources of total cosmic energy density throughout the history of the Universe. We demonstrate that current and future gravitational wave detectors, such as LIGO and LISA, could be capable of measuring the frequency spectrum of gravitational waves from cosmic strings and discerning the energy composition of the Universe at times well before primordial nucleosynthesis and the cosmic microwave background where standard cosmology has yet to be tested. This work establishes a benchmark case that gravitational waves may provide an unprecedented, powerful tool for probing the evolutionary history of the very early Universe.

The constrained multi-objective optimization problems (CMOPs) are always hard to handle when the constraints are too stringent. In this paper, a two-stage differential evolution algorithm (TSCMODE) is proposed to solve CMOPs, and non-dominated sorting is used to select offspring individuals. Firstly, in the early stage of evolution, a efficient constraint handing technique is proposed to generate more feasible solutions, and differential mutation is used to generate high quality offspring individuals. Then, at a later stage in evolution, the feasibility conditions are used to divide the population into upper and lower sub-populations, the good genes from the upper sub-population are passed to the lower offspring individuals by differential evolution. Besides, the objective values of the lower sub-population are adjusted self-adaptively to avoid the potential infeasibility being discarded. Finally, the proposed algorithm is executed on some recent benchmark functions and compared with four state-of-the art constrained multi-objective evolutionary algorithms. The experimental results show that TSCMODE can solve the CMOPs as well as.