scholarly journals Dynamical vacuum energy, holographic quintom, and the reconstruction of scalar-field dark energy

2006 ◽  
Vol 74 (10) ◽  
Author(s):  
Xin Zhang
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Vacuum Energy

scholarly journals PHANTOM UNIVERSE FROM CPT SYMMETRIC QFT

2006 ◽  
Vol 15 (08) ◽  
pp. 1299-1310 ◽  
Author(s):  
ALEXANDER A. ANDRIANOV ◽  
FRANCESCO CANNATA ◽  
ALEXANDER Y. KAMENSHCHIK
Keyword(s):  
Field Theory ◽  
Dark Energy ◽  
Scalar Field ◽  
Complex Potential ◽  
Vacuum Energy ◽  
Scalar Fields ◽  
Smooth Transition ◽  
Cpt Symmetry ◽  
Energy Equivalence ◽  
Cosmological Scalar

We develop a generalization of semiclassical field theory for the case of non-Hermitian Hamiltonians with CPT symmetry and construct a classical cosmological, scalar-field based model describing a smooth transition from ordinary dark energy to the phantom one. Our model arises from a Lagrangian with a complex potential leading to a non-trivial vacuum with real vacuum energy. Equivalence with models involving two scalar fields one of which is phantom-like is discussed.

scholarly journals SELF-TUNING DARK ENERGY IN BRANE WORLD COSMOLOGY

2001 ◽  
Vol 16 (17) ◽  
pp. 1089-1099 ◽  
Author(s):  
KUNIHITO UZAWA ◽  
JIRO SODA
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Vacuum Energy ◽  
Friedmann Equation ◽  
Brane World ◽  
Tuning Mechanism ◽  
Enormous Amount ◽  
Self Tuning ◽  
Bulk Scalar Field

In this letter, the self-tuning mechanism of dark energy is proposed by considering the cosmological matter in the brane world. In the first part of this letter, the effective four-dimensional Friedmann equation in the presence of the bulk scalar field is derived. In our model, the bulk scalar field takes the role of the dark energy and its value is slowly varying in time. The claim is that, even if the enormous amount of vacuum energy exists on the brane, the present value of the dark energy is self-tuned to be consistent with the current observations. This result will open the possibility to discuss the dark energy in the brane world in the context of the anthropic principle or quantum cosmology.

Effective masses in a dense fermion background — Applied to neutrinos, dark matter and dark energy

2014 ◽  
Vol 29 (21) ◽  
pp. 1444010
Author(s):  
Bruce H. J. McKellar ◽  
T. J. Goldman ◽  
G. J. Stephenson
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Effective Mass ◽  
Negative Pressure ◽  
Expectation Value ◽  
Effective Masses ◽  
Neutrino Astrophysics

If fermions interact with a scalar field, and there are many fermions present the scalar field may develop an expectation value and generate an effective mass for the fermions. This can lead to the formation of fermion clusters, which could be relevant for neutrino astrophysics and for dark matter astrophysics. Because this system may exhibit negative pressure, it also leads to a model of dark energy.

scholarly journals RECONSTRUCTING A STRING-INSPIRED NONMINIMALLY COUPLED QUINTOM MODEL

2009 ◽  
Vol 18 (08) ◽  
pp. 1291-1301 ◽  
Author(s):  
M. R. SETARE ◽  
J. SADEGHI ◽  
A. R. AMANI
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
String Theory ◽  
Scalar Curvature ◽  
Recent Work ◽  
Nonminimal Coupling ◽  
Tachyon Field ◽  
Dynamical Dark Energy

Motivated by the recent work of Zhang and Chen,1we generalize their work to the nonminimally coupled case. We consider a quintom model of dark energy with a single scalar field T given by a Lagrangian inspired by a tachyonic Lagrangian in string theory. We consider nonminimal coupling of the tachyon field to the scalar curvature, and then we reconstruct this model in the light of three forms of parametrization for dynamical dark energy.

scholarly journals Perturbed dark energy: Classical scalar field versus tachyon

2009 ◽  
Vol 80 (8) ◽  
Author(s):  
Olga Sergijenko ◽  
Bohdan Novosyadlyj
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Field Versus

scholarly journals FERMIONIC AND SCALAR FIELDS AS SOURCES OF INTERACTING DARK MATTER–DARK ENERGY

2011 ◽  
Vol 20 (13) ◽  
pp. 2543-2558 ◽  
Author(s):  
SAMUEL LEPE ◽  
JAVIER LORCA ◽  
FRANCISCO PEÑA ◽  
YERKO VÁSQUEZ
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Analytical Solution ◽  
Scalar Fields ◽  
Nonminimal Coupling ◽  
Field Equations ◽  
Fermionic Field ◽  
Minimal Coupling ◽  
Constant Type

From a variational action with nonminimal coupling with a scalar field and classical scalar and fermionic interaction, cosmological field equations can be obtained. Imposing a Friedmann–Lemaître–Robertson–Walker (FLRW) metric, the equations lead directly to a cosmological model consisting of two interacting fluids, where the scalar field fluid is interpreted as dark energy and the fermionic field fluid is interpreted as dark matter. Several cases were studied analytically and numerically. An important feature of the non-minimal coupling is that it allows crossing the barrier from a quintessence to phantom behavior. The insensitivity of the solutions to one of the parameters of the model permits it to find an almost analytical solution for the cosmological constant type of universe.

scholarly journals Emergent Universe as an interaction in the dark sector

2017 ◽  
Vol 32 (28) ◽  
pp. 1750152
Author(s):  
Emiliano Marachlian ◽  
I. E. Sánchez G. ◽  
Osvaldo P. Santillán
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Equation Of State ◽  
Linear Equation ◽  
Vacuum Energy ◽  
Cosmological Parameters ◽  
Emergent Universe ◽  
Dark Sector ◽  
Cosmological Scenario ◽  
Friedmann Robertson Walker

A cosmological scenario where dark matter interacts with a variable vacuum energy for a spatially flat Friedmann–Robertson–Walker (FRW) spacetime is proposed and analyzed to show that with a linear equation of state and a particular interaction in the dark sector it is possible to get a model of an Emergent Universe. In addition, the viability of two particular models is studied by taking into account the recent observations. The updated observational Hubble data and the JLA supernovae data are used in order to constraint the cosmological parameters of the models and estimate the amount of dark energy in the radiation era. It is shown that the two models fulfil the severe bounds of [Formula: see text] at the 2[Formula: see text] level of Planck.

scholarly journals On The Symmetry of The Universe

2020 ◽  
Author(s):  
Engel Roza
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Thermodynamic Equilibrium ◽  
Vacuum Energy ◽  
Quantum Mechanical ◽  
Baryonic Matter ◽  
Time Uncertainty ◽  
Matter Effect ◽  
Mechanical Interpretation ◽  
The Universe

It is shown that the Lambda component in the cosmological Lambda-CDM model can be conceived as vacuum energy, consisting of gravitational particles subject to Heisenberg’s energy-time uncertainty. These particles can be modelled as elementary polarisable Dirac-type dipoles (“darks”) in a fluidal space at thermodynamic equilibrium, with spins that are subject to the Bekenstein-Hawking entropy. Around the baryonic kernels, uniformly distributed in the universe, the spins are polarized, thereby invoking an increase of the effective gravitational strength of the kernels. It explains the dark matter effect to the extent that the numerical value of Milgrom’s acceleration constant can be assessed by theory. Non-polarized vacuum particles beyond the baryonic kernels compose the dark energy. The result is a quantum mechanical interpretation of gravity in terms of quantitatively established shares in baryonic matter, dark matter and dark energy, which correspond with the values of the Lambda-CDM model..

scholarly journals A NOTE ON THE CASIMIR ENERGY OF A MASSIVE SCALAR FIELD IN POSITIVE CURVATURE SPACE

2004 ◽  
Vol 19 (02) ◽  
pp. 111-116 ◽  
Author(s):  
E. ELIZALDE ◽  
A. C. TORT
Keyword(s):  
High Temperature ◽  
Scalar Field ◽  
Zeta Function ◽  
Vacuum Energy ◽  
Positive Curvature ◽  
Zero Point ◽  
Casimir Energy ◽  
Massive Scalar ◽  
Zero Temperature ◽  
Massive Scalar Field

We re-evaluate the zero point Casimir energy for the case of a massive scalar field in R1×S3 space, allowing also for deviations from the standard conformal value ξ=1/6, by means of zero temperature zeta function techniques. We show that for the problem at hand this approach is equivalent to the high temperature regularization of the vacuum energy, as conjectured in a previous publication. The analytic continuation can be performed in two ways, which are seen to be equivalent.

scholarly journals Scalar field dark energy and cosmic microwave background

2003 ◽  
Vol 124 ◽  
pp. 68-71 ◽  
Author(s):  
C. Baccigalupi ◽  
A. Balbi ◽  
S. Matarrese ◽  
F. Perrotta ◽  
N. Vittorio
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Cosmic Microwave Background ◽  
Microwave Background
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