A large amount of observations have constrained cosmological parameters and the initial density fluctuation spectrum to a very high accuracy. However, cosmological parameters change with time and the power index of the power spectrum dramatically varies with mass scale in the so-called concordance ΛCDM cosmology. Thus, any successful model for its structural evolution should work well simultaneously for various cosmological models and different power spectra. We use a large set of high-resolution N-body simulations of a variety of structure formation models (scale-free, standard CDM, open CDM, and ΛCDM) to study the mass accretion histories, the mass and redshift dependence of concentrations, and the concentration evolution histories of dark matter halos. We find that there is significant disagreement between the much-used empirical models in the literature and our simulations. Based on our simulation results, we find that the mass accretion rate of a halo is tightly correlated with a simple function of its mass, the redshift, parameters of the cosmology, and of the initial density fluctuation spectrum, which correctly disentangles the effects of all these factors and halo environments. We also find that the concentration of a halo is strongly correlated with the universe age when its progenitor on the mass accretion history first reaches 4% of its current mass. According to these correlations, we develop new empirical models for both the mass accretion histories and the concentration evolution histories of dark matter halos, and the latter can also be used to predict the mass and redshift dependence of halo concentrations. These models are accurate and universal: the same set of model parameters works well for different cosmological models and for halos of different masses at different redshifts, and in the ΛCDM case the model predictions match the simulation results very well even though halo mass is traced to about 0.0005 times the final mass, when cosmological parameters and the power index of the initial density fluctuation spectrum have changed dramatically. Our model predictions also match the PINOCCHIO mass accretion histories very well, which are much independent of our numerical simulations and our definitions of halo merger trees. These models are also simple and easy to implement, making them very useful in modeling the growth and structure of dark matter halos. We provide appendices describing the step-by-step implementation of our models. A calculator which allows one to interactively generate data for any given cosmological model is provided on the Web, together with a user-friendly code to make the relevant calculations and some tables listing the expected concentration as a function of halo mass and redshift in several popular cosmological models. We explain why ΛCDM and open CDM halos on nearly all mass scales show two distinct phases in their mass growth histories. We discuss implications of the universal relations we find in connection to the formation of dark matter halos in the cosmic density field. Show
To ensure we keep this website safe, please can you confirm you are a human by ticking the box below. If you are unable to complete the above request please contact us using the below link, providing a screenshot of your experience. Chapter 8 Developing A Global Management Cadre: International Management, 9e (Deresky) 0 ratings0% found this document useful (0 votes) 57 views34 pagesDocument Informationclick to expand document informationOriginal Titlechapter 8_1 Copyright© © All Rights Reserved Share this documentShare or Embed DocumentSharing Options
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Home Books Audiobooks Documents Which of the following is true with regard to a global product structure?Which of the following is true with regard to a global product structure? The advantages of this organizational form are market concentration, innovation, and responsiveness to new opportunities in a particular environment.
Which of the following is true about the matrix structure of organizational design?Which of the following is true of a matrix organizational structure? - In a matrix organizational structure, employees are organized into departments according to their skills, and there is little interaction between employees from different departments.
Which of the following organizational structures is the best for global firms?Matrix structure
The matrix structure is typically used by large, multinational organizations and promotes sharing skills and knowledge across departments to complete goals. Benefits of this type of structure include: Enabling a flexible work environment.
Which of the following is the most common form of organizing foreign operations?The correct option is b) global geographic structure
The global geographic structure in the form of organizing structure used by foreign firms for their operations in various regions.
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Which of the following is true with regard to the structural evolution model
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