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A cosmological constant fits all current dark energy data, but requires two extreme fine tunings, both of which are currently explained by anthropic arguments. Here we discuss anti-anthropic solutions to one of these problems: the cosmic…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-17 Joseph M. Fedrow , Kim Griest

We review the status of bouncing cosmologies as alternatives to cosmological inflation for providing a description of the very early universe, and a source for the cosmological perturbations which are observed today. We focus on the…

High Energy Physics - Theory · Physics 2017-03-08 Robert Brandenberger , Patrick Peter

The issue of the cosmological constant is discussed in details and a solution to the problem is suggested.

Astrophysics · Physics 2009-11-07 Moshe Carmeli

In this work we review briefly the origin and history of the cosmological constant and its recent reincarnation in the form of the dark energy component of the universe. We also comment on the fundamental problems associated to its…

Astrophysics · Physics 2009-06-23 Antonio Dobado , Antonio L. Maroto

We propose a scenario in which the dark components of the Universe are manifestations of a single bulk viscous fluid. Using dynamical system methods, a qualitative study of the homogeneous, isotropic background scenario is performed in…

Astrophysics · Physics 2008-12-18 R. Colistete , J. C. Fabris , J. Tossa , W. Zimdahl

A cosmological model is formulated in the context of a scalar-tensor theory of gravity in which the entire cosmic background evolution is due to a complex scalar field evolving in Minkowski spacetime, such that its (dimensional) modulus is…

General Physics · Physics 2019-09-24 Meir Shimon

This whitepaper focuses on the astrophysical systematics which are encountered in dark matter searches. Oftentimes in indirect and also in direct dark matter searches, astrophysical systematics are a major limiting factor to sensitivity to…

The presence of spinor fields is considered in the framework of some extensions of teleparallel gravity, where the Weitzenb\"ock connection is assumed. Some well known models as the Chaplygin gas and its generalizations are reconstructed in…

General Relativity and Quantum Cosmology · Physics 2013-11-22 Ratbay Myrzakulov , Diego Saez-Gomez , Petr Tsyba

We review an information-theoretic approach to quantum cosmology, summarising the key results obtained to date, including a suggestion that an accelerating universe will eventually turn around.

General Relativity and Quantum Cosmology · Physics 2012-03-30 Rajesh R. Parwani

We study the cosmology of bimetric theory with a composite matter coupling. We find two possible branches of background evolution. We investigate the question of stability of cosmological perturbations. For the tensor and vector…

High Energy Physics - Theory · Physics 2015-06-23 A. Emir Gumrukcuoglu , Lavinia Heisenberg , Shinji Mukohyama , Norihiro Tanahashi

The general k-essence Lagrangian for the existence of cosmological scaling solutions is derived in the presence of multiple scalar fields coupled to a barotropic perfect fluid. In addition to the scaling fixed point associated with the…

General Relativity and Quantum Cosmology · Physics 2014-07-14 Takeshi Chiba , Antonio De Felice , Shinji Tsujikawa

Cosmography represents an important branch of cosmology which aims to describe the universe without the need of postulating \emph{a priori} any particular cosmological model. All quantities of interest are expanded as a Taylor series around…

General Relativity and Quantum Cosmology · Physics 2016-03-23 Peter K. S. Dunsby , Orlando Luongo

Theoretical and observational challenges to standard cosmology such as the cosmological constant problem and tensions between cosmological model parameters inferred from different observations motivate the development and search of new…

Cosmology and Nongalactic Astrophysics · Physics 2023-06-30 Lucas Lombriser

We consider a model where both dark energy and dark matter originate from the coupling of a scalar field with a non-conventional kinetic term to, both, a metric measure and a non-metric measure. An interacting dark energy/dark matter…

General Relativity and Quantum Cosmology · Physics 2015-06-11 Stefano Ansoldi , Eduardo I. Guendelman

Cosmology is entering a very exciting time in its history, when a wealth of cutting-edge experiments are all starting to collect data, or about to. These experiments aim at addressing some of the most intriguing questions in fundamental…

Cosmology and Nongalactic Astrophysics · Physics 2024-11-07 N. Palanque-Delabrouille

Major advances in the observation and theory of cosmic microwave background anisotropies have opened up a new era in cosmology. This has encouraged the hope that the fundamental parameters of cosmology will be determined to high accuracy in…

Astrophysics · Physics 2015-06-24 Roy Maartens

We investigate cosmological models with a linear inhomogeneous time-dependent equation of state for the dark energy, coupled with dark matter, leading to a bounce cosmology. Equivalent descriptions in terms of the equation-of-state…

General Relativity and Quantum Cosmology · Physics 2014-05-07 I. Brevik , V. V. Obukhov , A. V. Timoshkin

The good agreement between large-scale observations and the predictions of the now-standard $\Lambda$CDM theory gives us hope that this will become a lasting foundation for cosmology. After briefly reviewing the current status of the key…

Astrophysics · Physics 2011-08-23 Joel R. Primack

The discovery of universe's late-time acceleration and dark energy has overseen a great deal of research into cosmological singularities and in this brief review, we discuss all the prominent developments in this field for the best part of…

General Relativity and Quantum Cosmology · Physics 2024-08-02 Oem Trivedi

The semiclassical backreaction equations are solved in closed Robertson-Walker spacetimes containing a positive cosmological constant and a conformally coupled massive scalar field. Renormalization of the stress-energy tensor results in…

General Relativity and Quantum Cosmology · Physics 2023-08-23 Leda Gao , Paul R. Anderson , Robert S. Link