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We discuss several explicitly causal hyperbolic formulations of Einstein's dynamical 3+1 equations in a coherent way, emphasizing throughout the fundamental role of the ``slicing function,'' $\alpha$---the quantity that relates the lapse…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Arlen Anderson , Yvonne Choquet-Bruhat , James W. York

A dynamic model of the Galaxy is constructed based on kinematic data for masers with trigonometric parallaxes. Maser data is used to compute the model potential in the Galactic plane. The potential is then generalized to three dimensions…

Astrophysics of Galaxies · Physics 2018-02-28 A. O. Gromov , I. I. Nikiforov , L. P. Ossipkov

We reconsider the collapse of cosmic structures in an Einstein-de Sitter Universe, using the self similar initial conditions of Fillmore & Goldreich (1984). We first derive a new approximation to describe the dark matter dynamics in…

Astrophysics · Physics 2009-10-30 Romain Teyssier , Jean-Pierre CHIEZE , Jean-Michel Alimi

We calculate the rate at which dark matter halos merge to form higher mass systems. Two complementary derivations using Press-Schechter theory are given, both of which result in the same equation for the formation rate. First, a derivation…

Astrophysics · Physics 2008-11-26 W. J. Percival , L. Miller

We promote the teaching of mass functions as an integral part of an interdisciplinary science education. Mass functions characterize the frequency distributions of objects with different masses on all cosmic scales. We intend to enhance…

Physics Education · Physics 2022-08-16 Stefan J. Kautsch , Dimitri Veras , Kyle K. Hansotia

Could one start from scratch, ignore relativity theory and quantum theory, create and expand our 3-D universe with no singularities, have the mathematical model predict correctly all of the cosmological parameters, provide the origins and…

Astrophysics · Physics 2007-05-23 Charles B. Leffert

We devise a new approach for the analysis of issues of geometric pathologies and black holes of a spacetime, based on a new mass function defined on an ideal un-physical spacetime which models time-flow or time dilation. The mass function…

Analysis of PDEs · Mathematics 2022-04-27 Jean Baptiste Patenou

The behavior of mass is well known, as described by Newton's Laws of Motion, the Lorentz Contractions, and Einstein's mass - energy equivalence. But just what mass is, how those behaviors come about, what in material reality produces the…

General Physics · Physics 2007-05-23 Roger Ellman

The emergence of macroscopic coherence in a many-body quantum system is a ubiquitous phenomenon across different physical systems and scales. This Chapter reviews key concepts characterizing such systems (correlation functions,…

Quantum Gases · Physics 2025-06-17 Nick P. Proukakis

Structure formation in the Universe has been well-studied within the Eulerian and Lagrangian perturbation theories, where the latter performs substantially better in comparison with N-body simulations. Standing out is the celebrated…

Cosmology and Nongalactic Astrophysics · Physics 2023-10-04 Niels Fardeau , Thomas Buchert , Fosca Al Roumi , Fereshteh Felegary

We will construct a theory which can explain the dynamics toward the steady state self-gravitating systems (SGSs) where many particles interact via the gravitational force. Real examples of SGS in the universe are globular clusters and…

Cosmology and Nongalactic Astrophysics · Physics 2011-08-09 Tohru Tashiro , Takayuki Tatekawa

We study the one-point probability distribution functions (PDFs) of the peculiar velocity and the density fluctuation in a cosmological fluid. Within the perturbative approach to the structure formation scenario, the effect of ``pressure''…

Astrophysics · Physics 2009-11-11 Takayuki Tatekawa

An original way of presentation of the Schwarzschild black hole in the form of a point-like mass with making the use of the Dirac $\delta$-function, including a description of a continuous collapse to such a point mass, is given. A…

General Relativity and Quantum Cosmology · Physics 2017-12-29 A. N. Petrov

We introduce a dynamical model to reduce a large cosmological constant to a sufficiently small value. The basic ingredient in this model is a distinction which has been made between the two unit systems used in cosmology and particle…

General Relativity and Quantum Cosmology · Physics 2010-05-12 Yousef Bisabr

In this study, we build upon the findings of Del Popolo et al. (2013) by further analyzing the influence of dynamical friction on the evolution of cosmological perturbations within the framework of the spherical collapse model (SCM) in a…

Cosmology and Nongalactic Astrophysics · Physics 2025-11-11 A. Del Popolo , Saeed Fakhry , Maryam Shiravand , Morgan Le Delliou

We study the spherical collapse model in the presence of quintessence with negligible speed of sound. This case is particularly motivated for w<-1 as it is required by stability. As pressure gradients are negligible, quintessence follows…

Cosmology and Nongalactic Astrophysics · Physics 2014-11-20 Paolo Creminelli , Guido D'Amico , Jorge Noreña , Leonardo Senatore , Filippo Vernizzi

In this study, a novel theory to investigate the mass oscillation of particles is proposed. It has been proven that, at high-energy conditions, the fermion field described by Dirac Lagrangian interacts with the half-integer spin tachyon…

General Physics · Physics 2018-07-24 Luca Nanni

We consider a set of macroscopic (classical) degrees of freedom coupled to an arbitrary many-particle Hamiltonian system, quantum or classical. These degrees of freedom can represent positions of objects in space, their angles, shape…

Statistical Mechanics · Physics 2015-06-17 Luca D'Alessio , Anatoli Polkovnikov

A relation connecting the {\it{rest mass}} and {\it{separation of events in space-time continuum}} is suggested and the idea of Compton scattering is used as a method for the determination of rest mass. An experiment involving collision of…

General Physics · Physics 2007-05-23 Arup Roy

One of the fundamental tasks of dynamical astronomy is to infer the distribution of mass in a stellar system from a snapshot of the positions and velocities of its stars. The usual approach to this task (e.g., Schwarzschild's method)…

Astrophysics of Galaxies · Physics 2018-05-17 Scott Tremaine