# Chaplygin gas questions

#### ensabah6

Generalized Chaplygin Gas, Accelerated Expansion and Dark Energy-Matter Unification
M. C. Bento, O. Bertolami, A. A. Sen
(Submitted on 18 Feb 2002 (v1), last revised 18 Apr 2002 (this version, v2))

We consider the scenario emerging from the dynamics of a generalized $d$-brane in a $(d+1, 1)$ spacetime. The equation of state describing this system is given in terms of the energy density, $\rho$, and pressure, $p$, by the relationship $p = - A/\rho^{\alpha}$, where $A$ is a positive constant and $0 < \alpha \le 1$. We discuss the conditions under which homogeneity arises and show that this equation of state describes the evolution of a universe evolving from a phase dominated by non-relativistic matter to a phase dominated by a cosmological constant via an intermediate period where the effective equation of state is given by $p = \alpha \rho$.

Cosmology with a Variable Chaplygin Gas
Zong-Kuan Guo, Yuan-Zhong Zhang
(Submitted on 4 Jun 2005 (v1), last revised 9 Jan 2007 (this version, v3))

We consider a new generalized Chaplygin gas model that includes the original Chaplygin gas model as a special case. In such a model the generalized Chaplygin gas evolves as from dust to quiessence or phantom. We show that the background evolution for the model is equivalent to that for a coupled dark energy model with dark matter. The constraints from the current type Ia supernova data favour a phantom-like Chaplygin gas model.

Many LQC papers use "Chaplygin gas", which appears to be a model that incorporates dark matter and dark energy.

Since the recent Xenon100 results were null, (dark matter not detected)
how seriously researched is Chaplygin gas as an alternative to dark matter?
How does chaplygin gas fit in with GR and QFT?

for string theorists, how does string theory incorporate Chaplygin gas, and what are its ramifications for such ideas as SUSY, extra dimensions, etc?

for LQG, it appears there are several LQC papers that incorporates Chaplygin gas.

i.e

arXiv.org > physics > arXiv:1102.2758

Physics > General Physics
Interacting modified Chaplygin gas in loop quantum cosmology
Mubasher Jamil, Ujjal Debnath
(Submitted on 14 Feb 2011)

We investigate the background dynamics when dark energy is coupled to dark matter in the universe described by loop quantum cosmology. We consider dark energy of the form modified Chaplygin gas. The dynamical system of equations is solved numerically and a stable scaling solution is obtained. It henceforth resolves the famous cosmic coincidence problem in modern cosmology. The statefinder parameters are also calculated to classify this dark energy model.

Quintessence and (Anti-)Chaplygin Gas in Loop Quantum Cosmology
Raphael Lamon, Andreas Woehr
(Submitted on 26 Oct 2009 (v1), last revised 21 Jan 2010 (this version, v3))

The concordance model of cosmology contains several unknown components such as dark matter and dark energy. Many proposals have been made to describe them by choosing an appropriate potential for a scalar field. We study four models in the realm of loop quantum cosmology (LQC): the Chaplygin gas, an inflationary and radiation-like potential, quintessence and an anti-Chaplygin gas. For the latter we show that all trajectories start and end with a type II singularity and, depending on the inital value, may go through a bounce. On the other hand the evolution under the influence of the first three scalar fields behaves classically at times far away from the big bang singularity and bounces as the energy density approaches the critical density.

Title: CHAPLYGIN INFLATION IN LOOP QUANTUM COSMOLOGY
Author(s):
XIN ZHANG
Department of Physics, College of Sciences, Northeastern University, Shenyang 110004, P. R. China
JINGFEI ZHANG
Department of Physics, College of Sciences, Northeastern University, Shenyang 110004, P. R. China
School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, P. R. China
JINGLEI CUI
Department of Physics, College of Sciences, Northeastern University, Shenyang 110004, P. R. China
LI ZHANG
Department of Physics, College of Sciences, Northeastern University, Shenyang 110004, P. R. China
History:
Received 10 November 2008
Abstract:
In this paper we discuss the inflationary universe in the context of a Chaplygin gas equation of state within the framework of the effective theory of loop quantum cosmology. Under the slow-roll approximation, we calculate the primordial perturbations for this model. We give the general expressions of the scalar spectral index, its running, and the tensor-to-scalar ratio, etc. For the chaotic inflation with a quadratic potential, using the WMAP 5-year results, we determine the parameters of the Chaplygin inflation model in loop quantum cosmology. The results are consistent with the WMAP observations.

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