scholarly journals Nonsingular cosmological models with strong gravity in the past

2021 ◽  
Vol 104 (6) ◽  
Author(s):  
Y. Ageeva ◽  
P. Petrov ◽  
V. Rubakov
Keyword(s):  
Cosmological Models ◽  
Strong Gravity ◽  
The Past

scholarly journals The anthropic argument against infinite past and the Eddington-Lemaitre universe

2000 ◽  
pp. 33-37 ◽  
Author(s):  
M.M. Cirkovic
Keyword(s):  
Steady State ◽  
Large Scale ◽  
Cosmological Models ◽  
State Model ◽  
The Past ◽  
Philosophy Of Cosmology ◽  
Ongoing Effort ◽  
Steady State Model ◽  
Nature Of Time ◽  
Additional Constraints

This study in the philosophy of cosmology is a part of an ongoing effort to investigate and reassess the importance of the anthropic (Davies-Tipler) argument against cosmologies containing the past temporal infinity. Obviously the prime targets of this argument are cosmological models stationary on sufficiently large scale, the classical steady state model of Bondi, Gold and Hoyle being the best example. Here we investigate the extension of application of this argument to infinitely old non-stationary models and discuss additional constraints necessary to be imposed on such models for the edge of the anthropic argument to be preserved. An illustrative counterexample is the classical Eddington-Lemaitre model, in the analysis of which major such constraints are presented. Consequences of such an approach for our understanding of the nature of time are briefly discussed.

scholarly journals Simulation of a rotating strong gravity that reverses time

2021 ◽  
pp. 7-16
Author(s):  
Yoshio Matsuki ◽  
Petro Bidyuk
Keyword(s):  
Angular Momentum ◽  
Gravitational Field ◽  
Momentum Density ◽  
Polar Coordinates ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
Strong Gravity ◽  
The Past ◽  
Stress Energy ◽  
The Future

In this research we simulated how time can be reversed with a rotating strong gravity. At first, we assumed that the time and the space can be distorted with the presence of a strong gravity, and then we calculated the angular momentum density of the rotating gravitational field. For this simulation we used Einstein’s field equation with spherical polar coordinates and the Euler’s transformation matrix to simulate the rotation. We also assumed that the stress-energy tensor that is placed at the end of the strong gravitational field reflects the intensities of the angular momentum, which is the normal (perpendicular) vector to the rotating axis. The result of the simulation shows that the angular momentum of the rotating strong gravity changes its directions from plus (the future) to minus (the past) and from minus (the past) to plus (the future), depending on the frequency of the rotation.

scholarly journals CONDITIONS FOR SPONTANEOUS HOMOGENIZATION OF THE UNIVERSE

2010 ◽  
Vol 19 (14) ◽  
pp. 2405-2412 ◽  
Author(s):  
KRZYSZTOF BOLEJKO ◽  
WILLIAM R. STOEGER
Keyword(s):  
Early Universe ◽  
Measure Zero ◽  
Initial Conditions ◽  
Cosmological Models ◽  
Dynamical Processes ◽  
The Past ◽  
Nonzero Measure ◽  
Current Paradigm ◽  
The Universe

The present-day universe appears to be homogeneous on very-large scales. Yet when the casual structure of the early universe is considered, it becomes apparent that the early universe must have been highly inhomogeneous. The current paradigm attempts to answer this problem by postulating the inflation mechanism. However, inflation in order to start requires a homogeneous patch of at least the horizon size. This paper examines if dynamical processes of the early universe could lead to homogenization. In the past similar studies seem to imply that the set of initial conditions that leads to homogenization is of measure zero. This essay proves the contrary: a set of initial conditions for spontaneous homogenization of cosmological models can form a set of nonzero measure.

Neutrinos and the arrow of time in cosmology

1962 ◽  
Vol 270 (1343) ◽  
pp. 553-561 ◽  
Keyword(s):  
Steady State ◽  
Cosmological Models ◽  
Arrow Of Time ◽  
De Sitter ◽  
The Past ◽  
The Future ◽  
State Models

Hogarth’s approach to the time-symmetric electrodynamics of Wheeler & Feynman is extended to apply to the neutrinos. It is shown that in some cosmological models neutrinos travelling both into the past and the future exist whereas in others only those going into the the future can exist. The Einstein-de Sitter and the steady-state models are the respective examples of the two cases. An interesting way of testing the various cosmologies by means of neutrino emitters and receivers is suggested.

scholarly journals COSMOLOGICAL MODELS FROM A DYNAMICAL SYSTEMS PERSPECTIVE

2005 ◽  
Vol 02 (02) ◽  
pp. 437-469 ◽  
Author(s):  
J. WAINWRIGHT ◽  
W. C. LIM
Keyword(s):  
Nonlinear Dynamics ◽  
Dynamical System ◽  
Dynamical Systems ◽  
Cosmological Models ◽  
Einstein Field Equations ◽  
Normalization Factor ◽  
Field Equations ◽  
Weyl Curvature ◽  
Systems Perspective ◽  
The Past

It is useful to study the space of all cosmological models from a dynamical systems perspective, that is, by formulating the Einstein field equations as a dynamical system using appropriately normalized variables. We will discuss various aspects of this work, the choices of normalization factor, multiple representations of models, the past attractor, nonlinear dynamics in close-to-Friedmann–Lemaître models, Weyl curvature dominance, and numerical simulations.

Observations of the continuum near the galactic centre

1967 ◽  
Vol 31 ◽  
pp. 405
Author(s):  
F. J. Kerr
Keyword(s):  
Galactic Centre ◽  
The Past ◽  
Centre Region ◽  
The Continuum

A continuum survey of the galactic-centre region has been carried out at Parkes at 20 cm wavelength over the areal11= 355° to 5°,b11= -3° to +3° (Kerr and Sinclair 1966, 1967). This is a larger region than has been covered in such surveys in the past. The observations were done as declination scans.

The Origin of the Moon and its Relationship to the Origin of the Solar System

1962 ◽  
Vol 14 ◽  
pp. 133-148 ◽  
Author(s):  
Harold C. Urey
Keyword(s):  
Solar System ◽  
The Moon ◽  
The Past ◽  
The Earth ◽  
Short Period ◽  
Origin Of The Moon

During the last 10 years, the writer has presented evidence indicating that the Moon was captured by the Earth and that the large collisions with its surface occurred within a surprisingly short period of time. These observations have been a continuous preoccupation during the past years and some explanation that seemed physically possible and reasonably probable has been sought.

On The Possibility of an Autonomous History of Modern Southeast Asia

1961 ◽  
Vol 2 (2) ◽  
pp. 73-105 ◽  
Author(s):  
John R. W. Small
Keyword(s):  
Southeast Asia ◽  
Contemporary History ◽  
The Past ◽  
History Of

It is generally accepted that history is an element of culture and the historian a member of society, thus, in Croce's aphorism, that the only true history is contemporary history. It follows from this that when there occur great changes in the contemporary scene, there must also be great changes in historiography, that the vision not merely of the present but also of the past must change.

Stellar Evolution

1962 ◽  
Vol 11 (02) ◽  
pp. 137-143
Author(s):  
M. Schwarzschild
Keyword(s):  
Solar System ◽  
Stellar Evolution ◽  
Space Craft ◽  
New Techniques ◽  
Substantial Body ◽  
Individual Stars ◽  
The Past ◽  
Evolution Of Galaxies ◽  
History Of ◽  
Fast Flow

It is perhaps one of the most important characteristics of the past decade in astronomy that the evolution of some major classes of astronomical objects has become accessible to detailed research. The theory of the evolution of individual stars has developed into a substantial body of quantitative investigations. The evolution of galaxies, particularly of our own, has clearly become a subject for serious research. Even the history of the solar system, this close-by intriguing puzzle, may soon make the transition from being a subject of speculation to being a subject of detailed study in view of the fast flow of new data obtained with new techniques, including space-craft.

Novae in the Magellanic Clouds

1979 ◽  
Vol 46 ◽  
pp. 96-101
Author(s):  
J.A. Graham
Keyword(s):  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
University Of Michigan ◽  
The Past ◽  
Spectroscopic Information ◽  
Objective Prism ◽  
The University ◽  
Small Cloud ◽  
Low Dispersion

During the past several years, a systematic search for novae in the Magellanic Clouds has been carried out at Cerro Tololo Inter-American Observatory. The Curtis Schmidt telescope, on loan to CTIO from the University of Michigan is used to obtain plates every two weeks during the observing season. An objective prism is used on the telescope. This provides additional low-dispersion spectroscopic information when a nova is discovered. The plates cover an area of 5°x5°. One plate is sufficient to cover the Small Magellanic Cloud and four are taken of the Large Magellanic Cloud with an overlap so that the central bar is included on each plate. The methods used in the search have been described by Graham and Araya (1971). In the CTIO survey, 8 novae have been discovered in the Large Cloud but none in the Small Cloud. The survey was not carried out in 1974 or 1976. During 1974, one nova was discovered in the Small Cloud by MacConnell and Sanduleak (1974).

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