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This book provides a comprehensive, self-contained introduction to one of the most exciting frontiers in astrophysics today: the quest to understand how the oldest and most distant galaxies in our universe first formed. Until now, most research on this question has been theoretical, but the next few years will bring about a new generation of large telescopes that promise to supply a flood of data about the infant universe during its first billion years after the big bang. This book bridges the gap between theory and observation. It is an invaluable reference for students and researchers on early galaxies. The First Galaxies in the Universestarts from basic physical principles before moving on to more advanced material. Topics include the gravitational growth of structure, the intergalactic medium, the formation and evolution of the first stars and black holes, feedback and galaxy evolution, reionization, 21-cm cosmology, and more. Provides a comprehensive introduction to this exciting frontier in astrophysicsBegins from first principlesCovers advanced topics such as the first stars and 21-cm cosmologyPrepares students for research using the next generation of large telescopesDiscusses many open questions to be explored in the coming decade

The visible mass of the observable universe agrees with that needed for a flat cosmos, and the reason for this is not known. It is shown that this can be explained by modelling the Hubble volume as a black hole that emits Hawking radiation inwards, disallowing wavelengths that do not fit exactly into the Hubble diameter, since partial waves would allow an inference of what lies outside the horizon. This model of “horizon wave censorship” is equivalent to a Hubble-scale Casimir effect. This incomplete toy model is presented to stimulate discussion. It predicts a minimum mass and acceleration for the observable universe which are in agreement with the observed mass and acceleration, and predicts that the observable universe gains mass as it expands and was hotter in the past. It also predicts a suppression of variation on the largest cosmic scales that agrees with the low-l cosmic microwave background anomaly seen by the Planck satellite.

Based on the assumption that some apparent properties of the observable universe are accurate at a reasonable level of approximation, a tentative is made to independently derive the values of the baryon density parameter, the Hubble constant, the cosmic microwave background temperature and the helium mass fraction. The obtained values are in excellent agreement with those given by the most recent observational data.

The objective of this paper is to draw attention to the close similarity between the observable universe and the photon mean free path sphere. It is hoped that by analyzing in depth this apparent connection one will be able to explain why our present epoch appears to have special properties. It is shown that some theoretical arguments point to an equality between the number of particles in the observable universe and the number of particles in the largest self-gravitating photon mean free path sphere ( MxPhMFPS .) This equality, supported by observational data, leads to a series of equations that relate in simple manner characteristics of the observable universe with characteristics of the MxPhMFPS , and allows a more precise approximation of the values of the main cosmological parameters. It is also shown that by replacing the protons in the MxPhMFPS with positrons, the radiation resulted by their interaction with the existing electrons has an energy equal to the energy of the electromagnetic radiation in the observable universe.

Humanity's ongoing quest to unlock the secrets of dark matter and dark energyHeart of Darkness describes the incredible saga of humankind's quest to unravel the deepest secrets of the universe. Over the past thirty years, scientists have learned that two little-understood components—dark matter and dark energy—comprise most of the known cosmos, explain the growth of all cosmic structure and hold the key to the universe's fate. The story of how evidence for the so-called \"Lambda-Cold Dark Matter\" model of cosmology has been gathered by generations of scientists throughout the world is told here by one of the pioneers of the field, Jeremiah Ostriker, and his coauthor Simon Mitton.From humankind's early attempts to comprehend Earth's place in the solar system, to astronomers' exploration of the Milky Way galaxy and the realm of the nebulae beyond, to the detection of the primordial fluctuations of energy from which all subsequent structure developed, this book explains the physics and the history of how the current model of our universe arose and has passed every test hurled at it by the skeptics. Throughout this rich story, an essential theme is emphasized: how three aspects of rational inquiry—the application of direct measurement and observation, the introduction of mathematical modeling, and the requirement that hypotheses should be testable and verifiable—guide scientific progress and underpin our modern cosmological paradigm.This monumental puzzle is far from complete, however, as scientists confront the mysteries of the ultimate causes of cosmic structure formation and the real nature and origin of dark matter and dark energy.

I have two contradictory reasons for being so happy to have the opportunity to write this summation of the evolution of my thoughts on education and compulsory schooling (two very distinct things) to this point in my life. The first is tied to a conversation that I had with my friend, Professor Madhu Suri Prakash one afternoon in the fall of 1984 during my post-doctoral studies at Penn State University.

In the context of the current lack of compatibility of the classical and quantum approaches to gravity, exactly solvable elementary pseudo-Hermitian quantum models are analyzed, supporting the acceptability of a point-like form of the Big Bang. The purpose is served by a hypothetical (non-covariant) identification of the “time of the Big Bang” with Kato’s exceptional-point parameter t=0. The consequences (including the ambiguity of the patterns of unfolding the singularity after the Big Bang) are studied in detail. In particular, singular values of the observables are shown to be useful in the analysis.

We review the neutrino science, focusing on its impact on cosmology along with the latest constraints on its mass and number of species. We also discuss its status as a possible solution to some of the recent cosmological tensions, such as the Hubble constant or the matter fluctuation parameter. We end by showing forecasts from next-generation planned or candidate surveys, highlighting their constraining power, alone or in combination, but also the limitations in determining neutrino mass distribution among its species.

In this work, we provide an algorithm to compute efficiently and accurately the full outgoing modal Green's kernel for the scalar wave equation in local helioseismology under spherical symmetry. Due to the high computational cost of a full Green's function, current helioseismic studies rely on single-source computations. However, a more realistic modelization of the helioseismic products (cross-covariance and power spectrum) requires the full Green's kernel. In the classical approach, the Dirac source is discretized and one simulation gives the Green's function on a line. Here, we propose a two-step algorithm which, with two simulations, provides the full kernel on the domain. Moreover, our method is more accurate, as the singularity of the solution due to the Dirac source is described exactly. In addition, it is coupled with the exact Dirichlet-to-Neumann boundary condition, providing optimal accuracy in approximating the outgoing Green's kernel, which we demonstrate in our experiments. In addition, we show that high-frequency approximations of the nonlocal radiation boundary conditions can represent accurately the helioseismic products.

Science and practical life strive to identify the generating or constraining conditions for the existence and character of whatever states of affairs concern them. Yet some conditions for phenomena within nature or for nature itself may be unidentifiable because there are no empirical data testing hypotheses about them or because relevant data are inaccessible. Three conditions external to nature are considered: God, eternal possibilities, and events priori to or consequent on the Big Bang. Empirical data confirming the existence and character of the first two are lacking; evidence relevant to the inception and effects of the third is inaccessible. Nature has conditions that will likely remain unknowable; the world is likely to be more complicated than we can know. Speculations about the existence and character of its silent conditions won't be deterred, though the absence of justifying empirical data entails that speculation doesn't justify belief.