ISBN: 9783896853813

[ED: Softcover], [PU: Wissenschaft & Technik Verlag, Inhaber Dr. Jrgen Groá / Wissenschaft + Technik Ve], The abundance of several elements can be measured in the intergalactic medium (IG… More...

[ED: Softcover], [PU: Wissenschaft & Technik Verlag, Inhaber Dr. Jrgen Groá / Wissenschaft + Technik Ve], The abundance of several elements can be measured in the intergalactic medium (IGM) by the absorption lines in quasar spectra. A milestone was the determination of the deuterium abundance. Using the most trustworthy deuterium determination, however, the prediction of the cosmic baryon density exceeds roughly by a factor of two those predictions derived by observations within our galaxy, e.g. evaluating the Spite plateau of lithium. As a consequence, the measured light element abundances which are supposed to be primordial, are not consistent with the predictions of the standard Big Bang nucleosynthesis (BBN) model. We discuss the standard BBN model and review briefly the current status of light element observations. There are several extensions to the standard model. We discuss briefly the inhomogeneous BBN, neutrino-degeneracy, and post-BBN processes. All these models fail to explain the observed abundances, unless a rather peculiar set of neutrino degeneracy parameters is assumed. The discrepancies can be removed by assuming that the reaction network which serves to calculate the element abundances is incomplete. We discuss the approximation of quasi-static equilibrium in the framework of the BBN model since it can serve to assess the impact of a given reaction. We investigate the 10B + d reaction in the incident particle EdCMS from 100 to 260 keV and determine the S-factors and the angular distributions of the protonand the a-channels. The particle-telescope technique is applied to measure the three a-particle break-up. The measured energy range is sufficient to determine the impact of this reaction on the primordial abundances of light elements. 10B he rates of the 10B(d,p)11B and the 10B(d, a)8 Be reactions are calculated. The rates of other deuteron-induces reactions which are also related to the production and destruction of beryllium, and carbon are estimated. We apply the approximation of quasi-static equilibrium to assess the impact of deuteron-induced reactions. Comparison with a complete integration of the reaction network reveals that this approximation is valid even at the freeze-out of the BBN reactions. The considered reactions have no impact on the primordial abundances exept for the 10B(d,n)11C reaction. It changes the 11B abundance at a 10% level. If standard BBN model predicts the actual primordial abundances the deuterium abundances in the IGM must have been changed. The chemical evolution of the IGM reducing the deuterium abundance could explain the discrepancies in the observations. The deuterium can be diluted by the feedback of processed hydrogen from galaxies. Simulations can serve to determine the probability for observing a certain deuterium abundance. We discuss briefly the formation of cosmological structures. The formation of the IGM can be investigated by cosmological N-body simulations. We implemente a P3M code using particle numbers up to 2563. To simulate the chemical evolution of the IGM a prescription for star formation is necessary. We argue that star formation occurs mainly as aftermath of the formation of the cosmological structures. That energy which is transformed from gravitational to kinetic energy at large scales is gradually transferred towards small scales and can finally force the baryonic matter into a turbulent state. We investigate the transfer of energy from large-scale towards small-scale modes. We introduce an algorithm developed by Lomb to determine the velocity spectrum of the dark matter in our simulations. The obtained velocity spectra are similar to the density spectra: They reproduce the linear growth at scales larger than 50 Mpc and exhibit a non-linear regime with a fast increase of power. In contrast to the density spectra the velocity spectra exhibit a common behavior towards small scales.This is reproduced independently from the box size of the simulation. The velocity power spectrum decreases with k-4 towards small scales. The velocity spectra show that mode coupling in the non-linear regime results almost exclusively in a transfer from large to small scales the inverse transfer is negligible. We estimate the dispersion-scale relation of the dark matter and show that it reproduces the scaling relation observed in the baryonic structures. Moreover, it reproduces roughly the amount of dispersion measured, e.g., in clouds. We deduce an expression to calculate the local increase in kinetic energy due to the transfer of energy between different modes in Fourier space. For that purpose we introduce an ansatz for the cumulative energy if the considered medium is compressible and verify that the ansatz results in a consistent scale-by-scale energy budget relation. Recently it has been shown that the density and the velocity field of both the internal structure and the distribution of molecular clouds is turbulent-like. We argue that the structure formation may be a source of the necessary energy input and calculate the local increase in kinetic energy using our P3M simulations. The mean energy release exhibits a behavior similar to that of the merging rate of dark matter halos. We conclude that the energy transfer due to the mode coupling traces the merging of halos. The local energy release per mass unit can be interpreted as a heating rate which can explain an additional heating demanded for the warm ionized medium in the halo of the Milky Way. The content of kinetic energy of both dark and baryonic matter can drastically increase when merger or minor-merger events occur. In contrast to the dark matter the baryonic matter can be forced into a turbulent state. Turbulence is a requirement for star formation. Consequently, the star formation is related to the energy release due to the structure formation. We argue that the logarithmic derivative of the specific flux is suitable for giving locally the efficiency of star formation. The product of it and the local density reproduces the global star formation history reasonably well. This prescription for star formation can be used to simulate the feed-back of galaxies to the IGM without incorporating semi-analytic models for galaxy evolution. 114 Seiten - 21 x 15 cm Sofort lieferbar, DE, [SC: 0.00], Neuware, gewerbliches Angebot, Offene Rechnung (Vorkasse vorbehalten)<

ISBN: 9783896853813

[ED: Softcover], [PU: Wissenschaft & Technik Verlag, Inhaber Dr. Jrgen Groá / Wissenschaft + Technik Ve], The abundance of several elements can be measured in the intergalactic medium (IG… More...

[ED: Softcover], [PU: Wissenschaft & Technik Verlag, Inhaber Dr. Jrgen Groá / Wissenschaft + Technik Ve], The abundance of several elements can be measured in the intergalactic medium (IGM) by the absorption lines in quasar spectra. A milestone was the determination of the deuterium abundance. Using the most trustworthy deuterium determination, however, the prediction of the cosmic baryon density exceeds roughly by a factor of two those predictions derived by observations within our galaxy, e.g. evaluating the Spite plateau of lithium. As a consequence, the measured light element abundances which are supposed to be primordial, are not consistent with the predictions of the standard Big Bang nucleosynthesis (BBN) model. We discuss the standard BBN model and review briefly the current status of light element observations. There are several extensions to the standard model. We discuss briefly the inhomogeneous BBN, neutrino-degeneracy, and post-BBN processes. All these models fail to explain the observed abundances, unless a rather peculiar set of neutrino degeneracy parameters is assumed. The discrepancies can be removed by assuming that the reaction network which serves to calculate the element abundances is incomplete. We discuss the approximation of quasi-static equilibrium in the framework of the BBN model since it can serve to assess the impact of a given reaction. We investigate the 10B + d reaction in the incident particle EdCMS from 100 to 260 keV and determine the S-factors and the angular distributions of the protonand the a-channels. The particle-telescope technique is applied to measure the three a-particle break-up. The measured energy range is sufficient to determine the impact of this reaction on the primordial abundances of light elements. 10B he rates of the 10B(d,p)11B and the 10B(d, a)8 Be reactions are calculated. The rates of other deuteron-induces reactions which are also related to the production and destruction of beryllium, and carbon are estimated. We apply the approximation of quasi-static equilibrium to assess the impact of deuteron-induced reactions. Comparison with a complete integration of the reaction network reveals that this approximation is valid even at the freeze-out of the BBN reactions. The considered reactions have no impact on the primordial abundances exept for the 10B(d,n)11C reaction. It changes the 11B abundance at a 10% level. If standard BBN model predicts the actual primordial abundances the deuterium abundances in the IGM must have been changed. The chemical evolution of the IGM reducing the deuterium abundance could explain the discrepancies in the observations. The deuterium can be diluted by the feedback of processed hydrogen from galaxies. Simulations can serve to determine the probability for observing a certain deuterium abundance. We discuss briefly the formation of cosmological structures. The formation of the IGM can be investigated by cosmological N-body simulations. We implemente a P3M code using particle numbers up to 2563. To simulate the chemical evolution of the IGM a prescription for star formation is necessary. We argue that star formation occurs mainly as aftermath of the formation of the cosmological structures. That energy which is transformed from gravitational to kinetic energy at large scales is gradually transferred towards small scales and can finally force the baryonic matter into a turbulent state. We investigate the transfer of energy from large-scale towards small-scale modes. We introduce an algorithm developed by Lomb to determine the velocity spectrum of the dark matter in our simulations. The obtained velocity spectra are similar to the density spectra: They reproduce the linear growth at scales larger than 50 Mpc and exhibit a non-linear regime with a fast increase of power. In contrast to the density spectra the velocity spectra exhibit a common behavior towards small scales.This is reproduced independently from the box size of the simulation. The velocity power spectrum decreases with k-4 towards small scales. The velocity spectra show that mode coupling in the non-linear regime results almost exclusively in a transfer from large to small scales the inverse transfer is negligible. We estimate the dispersion-scale relation of the dark matter and show that it reproduces the scaling relation observed in the baryonic structures. Moreover, it reproduces roughly the amount of dispersion measured, e.g., in clouds. We deduce an expression to calculate the local increase in kinetic energy due to the transfer of energy between different modes in Fourier space. For that purpose we introduce an ansatz for the cumulative energy if the considered medium is compressible and verify that the ansatz results in a consistent scale-by-scale energy budget relation. Recently it has been shown that the density and the velocity field of both the internal structure and the distribution of molecular clouds is turbulent-like. We argue that the structure formation may be a source of the necessary energy input and calculate the local increase in kinetic energy using our P3M simulations. The mean energy release exhibits a behavior similar to that of the merging rate of dark matter halos. We conclude that the energy transfer due to the mode coupling traces the merging of halos. The local energy release per mass unit can be interpreted as a heating rate which can explain an additional heating demanded for the warm ionized medium in the halo of the Milky Way. The content of kinetic energy of both dark and baryonic matter can drastically increase when merger or minor-merger events occur. In contrast to the dark matter the baryonic matter can be forced into a turbulent state. Turbulence is a requirement for star formation. Consequently, the star formation is related to the energy release due to the structure formation. We argue that the logarithmic derivative of the specific flux is suitable for giving locally the efficiency of star formation. The product of it and the local density reproduces the global star formation history reasonably well. This prescription for star formation can be used to simulate the feed-back of galaxies to the IGM without incorporating semi-analytic models for galaxy evolution. 114 Seiten - 21 x 15 cm Sofort lieferbar, DE, Neuware, gewerbliches Angebot, Offene Rechnung (Vorkasse vorbehalten)<

ISBN: 9783896853813

[ED: Softcover], [PU: Wissenschaft & Technik / Wissenschaft + Technik Ve], The abundance of several elements can be measured in the intergalactic medium (IGM) by the absorption lines in q… More...

[ED: Softcover], [PU: Wissenschaft & Technik / Wissenschaft + Technik Ve], The abundance of several elements can be measured in the intergalactic medium (IGM) by the absorption lines in quasar spectra. A milestone was the determination of the deuterium abundance. Using the most trustworthy deuterium determination, however, the prediction of the cosmic baryon density exceeds roughly by a factor of two those predictions derived by observations within our galaxy, e.g. evaluating the Spite plateau of lithium. As a consequence, the measured light element abundances which are supposed to be primordial, are not consistent with the predictions of the standard Big Bang nucleosynthesis (BBN) model. We discuss the standard BBN model and review briefly the current status of light element observations. There are several extensions to the standard model. We discuss briefly the inhomogeneous BBN, neutrino-degeneracy, and post-BBN processes. All these models fail to explain the observed abundances, unless a rather peculiar set of neutrino degeneracy parameters is assumed. The discrepancies can be removed by assuming that the reaction network which serves to calculate the element abundances is incomplete. We discuss the approximation of quasi-static equilibrium in the framework of the BBN model since it can serve to assess the impact of a given reaction. We investigate the 10B + d reaction in the incident particle EdCMS from 100 to 260 keV and determine the S-factors and the angular distributions of the protonand the a-channels. The particle-telescope technique is applied to measure the three a-particle break-up. The measured energy range is sufficient to determine the impact of this reaction on the primordial abundances of light elements. 10B he rates of the 10B(d,p)11B and the 10B(d, a)8 Be reactions are calculated. The rates of other deuteron-induces reactions which are also related to the production and destruction of beryllium, and carbon are estimated. We apply the approximation of quasi-static equilibrium to assess the impact of deuteron-induced reactions. Comparison with a complete integration of the reaction network reveals that this approximation is valid even at the freeze-out of the BBN reactions. The considered reactions have no impact on the primordial abundances exept for the 10B(d,n)11C reaction. It changes the 11B abundance at a 10% level. If standard BBN model predicts the actual primordial abundances the deuterium abundances in the IGM must have been changed. The chemical evolution of the IGM reducing the deuterium abundance could explain the discrepancies in the observations. The deuterium can be diluted by the feedback of processed hydrogen from galaxies. Simulations can serve to determine the probability for observing a certain deuterium abundance. We discuss briefly the formation of cosmological structures. The formation of the IGM can be investigated by cosmological N-body simulations. We implemente a P3M code using particle numbers up to 2563. To simulate the chemical evolution of the IGM a prescription for star formation is necessary. We argue that star formation occurs mainly as aftermath of the formation of the cosmological structures. That energy which is transformed from gravitational to kinetic energy at large scales is gradually transferred towards small scales and can finally force the baryonic matter into a turbulent state. We investigate the transfer of energy from large-scale towards small-scale modes. We introduce an algorithm developed by Lomb to determine the velocity spectrum of the dark matter in our simulations. The obtained velocity spectra are similar to the density spectra: They reproduce the linear growth at scales larger than 50 Mpc and exhibit a non-linear regime with a fast increase of power. In contrast to the density spectra the velocity spectra exhibit a common behavior towards small scales.This is reproduced independently from the box size of the simulation. The velocity power spectrum decreases with k-4 towards small scales. The velocity spectra show that mode coupling in the non-linear regime results almost exclusively in a transfer from large to small scales the inverse transfer is negligible. We estimate the dispersion-scale relation of the dark matter and show that it reproduces the scaling relation observed in the baryonic structures. Moreover, it reproduces roughly the amount of dispersion measured, e.g., in clouds. We deduce an expression to calculate the local increase in kinetic energy due to the transfer of energy between different modes in Fourier space. For that purpose we introduce an ansatz for the cumulative energy if the considered medium is compressible and verify that the ansatz results in a consistent scale-by-scale energy budget relation. Recently it has been shown that the density and the velocity field of both the internal structure and the distribution of molecular clouds is turbulent-like. We argue that the structure formation may be a source of the necessary energy input and calculate the local increase in kinetic energy using our P3M simulations. The mean energy release exhibits a behavior similar to that of the merging rate of dark matter halos. We conclude that the energy transfer due to the mode coupling traces the merging of halos. The local energy release per mass unit can be interpreted as a heating rate which can explain an additional heating demanded for the warm ionized medium in the halo of the Milky Way. The content of kinetic energy of both dark and baryonic matter can drastically increase when merger or minor-merger events occur. In contrast to the dark matter the baryonic matter can be forced into a turbulent state. Turbulence is a requirement for star formation. Consequently, the star formation is related to the energy release due to the structure formation. We argue that the logarithmic derivative of the specific flux is suitable for giving locally the efficiency of star formation. The product of it and the local density reproduces the global star formation history reasonably well. This prescription for star formation can be used to simulate the feed-back of galaxies to the IGM without incorporating semi-analytic models for galaxy evolution. 114 Seiten - 21 x 15 cm Sofort lieferbar, DE, [SC: 0.00], Neuware, gewerbliches Angebot, offene Rechnung (Vorkasse vorbehalten)<

2001, ISBN: 9783896853813

[ED: Taschenbuch], [PU: Wissenschaft + Technik Ve], DE, [SC: 0.00], Neuware, gewerbliches Angebot, 114, [GW: 160g], Sofortüberweisung, PayPal, Banküberweisung

ISBN: 9783896853813

[ED: Taschenbuch], [PU: Wissenschaft + Technik Ve], Neuware -, DE, [SC: 2.00], Neuware, gewerbliches Angebot, 205x147x10 mm, 114, [GW: 160g], PayPal, Offene Rechnung, Banküberweisung, Sof… More...

[ED: Taschenbuch], [PU: Wissenschaft + Technik Ve], Neuware -, DE, [SC: 2.00], Neuware, gewerbliches Angebot, 205x147x10 mm, 114, [GW: 160g], PayPal, Offene Rechnung, Banküberweisung, Sofortüberweisung, Internationaler Versand<