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The global geometry of the universe is in principle as observable an attribute as local curvature. Previous studies have established that if the universe is wrapped into a flat hypertorus, the simplest compact space, then the fundamental…

Astrophysics · Physics 2009-10-30 Janna Levin , Evan Scannapieco , Joseph Silk

The quest to understand better the nature of the initial cosmological singularity is with us since the discovery of the expanding universe. Here, we propose several non-flat models, among them the standard cosmological scenario with a…

General Relativity and Quantum Cosmology · Physics 2021-12-28 Andres Felipe Estupinan Salamanca , Sergio Bravo Medina , Marek Nowakowski , Davide Batic

Our Milky Way Galaxy is a typical large spiral galaxy, representative of the most common morphological type in the local Universe. We can determine the properties of individual stars in unusual detail, and use the characteristics of the…

Astrophysics · Physics 2007-05-23 Rosemary F. G. Wyse

The presently accelerating universe may keep accelerating forever, eventually run into the event horizon problem, and thus be in conflict with the superstring idea. In the other way around, the current accelerating phase as well as the fate…

Astrophysics · Physics 2009-11-06 Je-An Gu , W-Y. P. Hwang

Matter collapsing to a singularity in a gravitational field is still an intriguing question. Similar situation arises when discussing the very early universe or a universe recollapsing to a singularity. It is suggested that inclusion of…

Astrophysics · Physics 2011-07-04 C Sivaram , Kenath Arun , Venkata Manohara Reddy A

For two decades the hot big-bang model as been referred to as the standard cosmology -- and for good reason. For just as long cosmologists have known that there are fundamental questions that are not answered by the standard cosmology and…

Astrophysics · Physics 2007-05-23 Michael S. Turner

Cosmological observations are beginning to reach a level of precision that allow us to test some of the most fundamental assumptions in our working model of the Universe. One such an assumption is that gravity is governed by the General…

Cosmology and Nongalactic Astrophysics · Physics 2019-09-11 Pedro G. Ferreira

We search for a direction in the sky that exhibits parity symmetry under reflections through a plane. We use the natural estimator, which compares the power in even and odd $\ell+m$ multipoles, and apply minimal blind masking of outliers to…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-30 Assaf Ben-David , Ely D. Kovetz , Nissan Itzhaki

Whether the spiral structure of galaxies is trailing or leading has been a subject of debate. We present a new spin parity catalog of 146 spiral galaxies that lists the following three pieces of information: whether the spiral structure…

Astrophysics of Galaxies · Physics 2020-01-08 Masanori Iye , Kenichi Tadaki , Hideya Fukumoto

How is the universe organized on large scales? How did this structure evolve from the unknown initial conditions to the present time? The answers to these questions will shed light on the cosmology we live in, the amount, composition and…

Astrophysics · Physics 2009-09-25 Neta A. Bahcall

Problems with uniform probabilities on an infinite support show up in contemporary cosmology. This paper focuses on the context of inflation theory, where it complicates the assignment of a probability measure over pocket universes. The…

History and Philosophy of Physics · Physics 2023-09-11 Sylvia Wenmackers

Under the assumption that General Relativity (GR) correctly describes the phenomenology of our Universe, astronomical observations provide compelling evidence that (1) the dynamics of cosmic structure is dominated by dark matter (DM), an…

Astrophysics · Physics 2008-02-19 A. Diaferio

We study some collective phenomena that may happen in a multiverse scenario. First, it is posed an interaction scheme between universes whose evolution is dominated by a cosmological constant. As a result of the interaction, the value of…

General Relativity and Quantum Cosmology · Physics 2017-08-04 A. Alonso-Serrano , C. Bastos , O. Bertolami , S. Robles-Perez

We define a universe as the contents of a spacetime box with comoving walls, large enough to contain essentially all phenomena that can be conceivably measured. The initial time is taken as the epoch when the lowest CMB modes undergo…

Astrophysics · Physics 2007-05-23 James D. Bjorken

We explore a model in which the cosmological constant $\Lambda$ and the density contrast at the time of recombination $\sigma_{rec}$ are random variables, whose range and {\it a priori} probabilities are determined by the laws of physics.…

Astrophysics · Physics 2016-08-25 Jaume Garriga , Mario Livio , Alexander Vilenkin

Although the cosmological constant has primarily cosmological consequences, its smallness poses one of the basic problems in particle physics. Various attempts have been made to explain this mystery, but no satisfactory solution has been…

High Energy Physics - Phenomenology · Physics 2007-05-23 Hans Peter Nilles

In a room with five cosmologists there there may easily be ten theories of cosmogenesis. Cosmogenesis is a popular topic for speculation because it is philosophically deep and because such speculations are unlikely to be proven wrong in the…

General Relativity and Quantum Cosmology · Physics 2011-07-27 Ronald J. Adler

Recent late-Universe observations suggest an open Universe. If confirmed, such a departure from spatial flatness would carry profound implications for our understanding of cosmic inflation and the ultimate fate of the Universe. Motivated by…

Cosmology and Nongalactic Astrophysics · Physics 2026-04-28 Peng-Ju Wu

The expansion of the universe is often viewed as a uniform stretching of space that would affect compact objects, atoms and stars, as well as the separation of galaxies. One usually hears that bound systems do not take part in the general…

General Relativity and Quantum Cosmology · Physics 2012-01-10 Richard H. Price , Joseph D. Romano

We have critically compared different approaches to the cosmological constant problem, which is at the edge of elementary particle physics and cosmology. This problem is deeply connected with the difficulties formulating a theory of quantum…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Stefan Nobbenhuis