scholarly journals DARK ENERGY AS A RELIC OF THE VACUUM-ENERGY CANCELLATION?

2008 ◽  
Vol 17 (01) ◽  
pp. 111-133
Author(s):  
ORCHIDEA MARIA LECIAN ◽  
GIOVANNI MONTANI
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Gravitational Interaction ◽  
Friedmann Equation ◽  
Vacuum Energy Density ◽  
De Sitter ◽  
Frw Universe ◽  
First Case ◽  
Present Universe

We analyze the dynamical implications of an exponential Lagrangian density for the gravitational field, as referred to an isotropic FRW Universe. Then, we discuss the features of the generalized de Sitter phase, predicted by the new Friedmann equation. The existence of a consistent de Sitter solution arises only if the ratio between the vacuum energy density and that associated with the fundamental length of the theory acquires a tantalizing negative character. This choice allows us to explain the present Universe dark energy as a relic of the vacuum-energy cancellation due to the cosmological constant intrinsically contained in our scheme. The corresponding scalar-tensor description of the model is addressed too, and the behavior of the scalar field is analyzed for both negative and positive values of the cosmological term. In the first case, the Friedmann equation is studied both in vacuum and in the presence of external matter, while, in the second case, the quantum regime is approached in the framework of "repulsive" properties of the gravitational interaction, as described in recent issues in loop quantum cosmology. In particular, in the vacuum case, we find a pure non-Einsteinian effect, according to which a negative cosmological constant provides an accelerating de Sitter dynamics, in the region where the series expansion of the exponential term does not hold.

scholarly journals DARK ENERGY DENSITY IN MODELS WITH SPLIT SUPERSYMMETRY AND DEGENERATE VACUA

2012 ◽  
Vol 27 (11) ◽  
pp. 1250063 ◽  
Author(s):  
C. FROGGATT ◽  
R. NEVZOROV ◽  
H. B. NIELSEN
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Susy Breaking ◽  
Vacuum Energy Density ◽  
Dark Energy Density ◽  
Hidden Sector ◽  
Split Supersymmetry ◽  
Breaking Scale

In N = 1 supergravity supersymmetric and nonsupersymmetric Minkowski vacua originating in the hidden sector can be degenerate. In the supersymmetric phase in flat Minkowski space, nonperturbative supersymmetry breakdown may take place in the observable sector, inducing a nonzero and positive vacuum energy density. Assuming that such a supersymmetric phase and the phase in which we live are degenerate, we estimate the value of the cosmological constant. We argue that the observed value of the dark energy density can be reproduced in the split SUSY scenario of SUSY breaking if the SUSY breaking scale is of order of 1010 GeV.

scholarly journals ELECTROMAGNETIC DARK ENERGY

2008 ◽  
Vol 17 (01) ◽  
pp. 71-80 ◽  
Author(s):  
CHRISTIAN BECK ◽  
MICHAEL C. MACKEY
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Phase Synchronization ◽  
Active Phase ◽  
Vacuum Energy Density ◽  
Ginzburg Landau ◽  
Low Frequencies ◽  
Virtual Photons ◽  
Inactive Phase

We introduce a new model for dark energy in the Universe in which a small cosmological constant is generated by ordinary electromagnetic vacuum energy. The corresponding virtual photons exist at all frequencies but switch from a gravitationally active phase at low frequencies to a gravitationally inactive phase at higher frequencies via a Ginzburg–Landau type of phase transition. Only virtual photons in the gravitationally active state contribute to the cosmological constant. A small vacuum energy density, consistent with astronomical observations, is naturally generated in this model. We propose possible laboratory tests for such a scenario based on phase synchronization in superconductors.

scholarly journals SUPERSYMMETRIC BAROTROPIC FRW MODEL AND DARK ENERGY

2009 ◽  
Vol 24 (16) ◽  
pp. 1257-1266
Author(s):  
J. J. ROSALES ◽  
V. I. TKACH
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Perfect Fluid ◽  
Vacuum Energy ◽  
Matter Field ◽  
Vacuum Energy Density ◽  
Square Root ◽  
Frw Universe ◽  
Frw Model

Using the superfield approach we construct the n = 2 supersymmetric Lagrangian for the FRW Universe with barotropic perfect fluid as matter field. The obtained supersymmetric algebra allowed us to take the square root of the Wheeler–DeWitt equation and solve the corresponding quantum constraint. This model leads to the relation between the vacuum energy density and the energy density of the dust matter.

IMPORTANT REMARKS ON (ANTI) de SITTER SPACES AND THE COSMOLOGICAL CONSTANT

2006 ◽  
Vol 21 (35) ◽  
pp. 2685-2701 ◽  
Author(s):  
CARLOS CASTRO
Keyword(s):  
Energy Density ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Radial Function ◽  
Vacuum Energy Density ◽  
De Sitter ◽  
Cosmological Constant Problem ◽  
Natural Explanation ◽  
Observable Universe ◽  
Weyl Geometry

A class of proper and novel generalizations of the (anti) de Sitter solutions (parametrized by a family of radial functions R(r)) are presented that could provide a very plausible resolution of the cosmological constant problem along with a natural explanation of the ultraviolet/infrared (uv/ir) entanglement required to solve this problem. A nonvanishing value of the vacuum energy density of the order of [Formula: see text] is derived in agreement with the experimental observations. The presence of the radial function R(r) is instrumental to understand why the cosmological constant is not zero and why it is so tiny. The correct lower estimate of the mass of the observable universe related to the Dirac–Eddington's large number N = 1080 is also obtained. Finally we present our most recent findings of how Weyl Geometry via a Brans–Dicke scalar field solves the riddle of dark energy in addition to providing another derivation of the vacuum energy density.

scholarly journals Evaluation of the Cosmological Constant in Inflation with a Massive Nonminimal Scalar Field

2015 ◽  
Vol 2015 ◽  
pp. 1-7
Author(s):  
Jung-Jeng Huang
Keyword(s):  
Scalar Field ◽  
Dispersion Relation ◽  
Energy Density ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Vacuum State ◽  
Energy Scale ◽  
Quantum Evolution ◽  
Vacuum Energy Density ◽  
De Sitter

In Schrödinger picture we study the possible effects of trans-Planckian physics on the quantum evolution of massive nonminimally coupled scalar field in de Sitter space. For the nonlinear Corley-Jacobson type dispersion relations with quartic or sextic correction, we obtain the time evolution of the vacuum state wave functional during slow-roll inflation and calculate explicitly the corresponding expectation value of vacuum energy density. We find that the vacuum energy density is finite. For the usual dispersion parameter choice, the vacuum energy density for quartic correction to the dispersion relation is larger than for sextic correction, while for some other parameter choices, the vacuum energy density for quartic correction is smaller than for sextic correction. We also use the backreaction to constrain the magnitude of parameters in nonlinear dispersion relation and show how the cosmological constant depends on the parameters and the energy scale during the inflation at the grand unification phase transition.

The quantum Higgs field and the resolution of the cosmological constant paradox in the Weyl-geometrical Universe

2017 ◽  
Vol 15 (08) ◽  
pp. 1740025
Author(s):  
Francesco De Martini
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Vacuum Energy Density ◽  
Universal Theory ◽  
Recent Experimental Data ◽  
Electroweak Theory ◽  
Mass Reduction ◽  
Parallel Displacement ◽  
The Universe

The nature of the scalar field responsible for the cosmological inflation is found to be rooted in the most fundamental concept of the Weyl’s differential geometry: the parallel displacement of vectors in curved spacetime. Within this novel geometrical scenario, the standard electroweak theory of leptons based on the [Formula: see text] as well as on the conformal groups of spacetime Weyl’s transformations is analyzed within the framework of a general-relativistic, conformally-covariant scalar–tensor theory that includes the electromagnetic and the Yang–Mills fields. A Higgs mechanism within a spontaneous symmetry breaking process is identified and this offers formal connections between some relevant properties of the elementary particles and the dark energy content of the Universe. An “effective cosmological potential”: [Formula: see text] is expressed in terms of the dark energy potential: [Formula: see text] via the “mass reduction parameter”: [Formula: see text], a general property of the Universe. The mass of the Higgs boson, which is considered a “free parameter” by the standard electroweak theory, by our theory is found to be proportional to the mass [Formula: see text] which contributes to the measured Cosmological Constant, i.e. the measured content of vacuum-energy in the Universe. The nonintegrable application of the Weyl’s geometry leads to a Proca equation accounting for the dynamics of a [Formula: see text]-particle, a vector-meson proposed as an optimum candidate for Dark Matter. The peculiar mathematical structure of [Formula: see text] offers a clue towards a very general resolution in 4-D of a most intriguing puzzle of modern quantum field theory, the “cosmological constant paradox”(here referred to as: “[Formula: see text]-paradox”). Indeed, our “universal” theory offers a resolution of the “[Formula: see text]-paradox” for all exponential inflationary potentials: [Formula: see text], and for all linear superpositions of these potentials, where [Formula: see text] belongs to the mathematical set of the “real numbers”. An explicit solution of the [Formula: see text]-Paradox is reported for [Formula: see text]. The results of the theory are analyzed in the framework of the recent experimental data of the PLANCK Mission. The average vacuum-energy density in the Universe is found: [Formula: see text], the mass-reduction parameter: [Formula: see text] and the value of the “cosmological constant”: [Formula: see text](eV/c[Formula: see text]. A quite remarkable result of the theory consists of the complete formulation of the Einstein equation including in its structure the “cosmological constant”, [Formula: see text]. This was the term that Einstein added “by hand” to his famous equation. The critical stability of the Universe is also discussed.

A Clifford-gravity-based cosmology, dark matter and dark energy

2015 ◽  
Vol 12 (03) ◽  
pp. 1550037 ◽  
Author(s):  
Carlos Castro
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Degrees Of Freedom ◽  
Vacuum Energy ◽  
Vacuum Energy Density ◽  
De Sitter ◽  
Four Dimensions ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Universe

A Clifford-gravity-based model is exploited to build a generalized action (beyond the current ones used in the literature) and arrive at relevant numerical results which are consistent with the presently-observed de Sitter accelerating expansion of the universe driven by a very small vacuum energy density ρ obs ~ 10-120(MP)4 (MP is the Planck mass) and provide promising dark energy/matter candidates in terms of the 16 scalars corresponding to the degrees of freedom associated with a Cl (3, 1)-algebra-valued scalar field Φ in four dimensions.

ON NONCOMMUTATIVE MINISUPERSPACE, COSMOLOGY AND Λ

2009 ◽  
Vol 24 (24) ◽  
pp. 1907-1914 ◽  
Author(s):  
O. OBREGÓN ◽  
M. SABIDO ◽  
E. MENA
Keyword(s):  
Simple Model ◽  
Energy Density ◽  
Cosmological Constant ◽  
Degrees Of Freedom ◽  
Vacuum Energy ◽  
Vacuum Energy Density ◽  
Frw Universe

In this letter we study the effects of a noncommutative minisuperspace, including matter degrees of freedom on a toy model for FRW universe with cosmological constant. In this simple model the vacuum energy density is modified by the presence of the noncommutative minisuperspace parameter, from which we conjecture on the discrepancy between the calculated and observed vacuum energy density associated to Λ.

scholarly journals Decaying vacuum and evolution from early inflation to late acceleration

2021 ◽  
pp. 2150160
Author(s):  
N. Sarath ◽  
Titus K. Mathew
Keyword(s):  
Energy Density ◽  
Vacuum Energy ◽  
Friedmann Equation ◽  
Time Dependent ◽  
Vacuum Energy Density ◽  
De Sitter ◽  
Unified Framework ◽  
Number Formula ◽  
Hubble Radius ◽  
The Universe

Decaying vacuum models are a class of models that incorporate a time-dependent vacuum energy density that can explain the entire evolution of the universe in a unified framework. A general solution to the Friedmann equation is obtained by considering vacuum energy density as a function of the Hubble parameter. We have obtained the asymptotic solution by choosing the equation of state for matter, [Formula: see text] and radiation, [Formula: see text]. Finite boundaries in the early and late de Sitter epoch are defined by considering the evolution of primordial perturbation wavelength. An epoch invariant number [Formula: see text] determines the number of primordial perturbation modes that cross the Hubble radius during each epoch.

scholarly journals Explaining Dark Energy, Small Cosmological Constant and Inflation Without New Physics?

2020 ◽  
Author(s):  
Stephane Maes
Keyword(s):  
Dark Energy ◽  
Random Walk ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
New Physics ◽  
Vacuum Energy Density ◽  
Beyond The Standard Model ◽  
Exponential Expansion ◽  
Acceleration Of The Universe ◽  
The Universe

In a multi-fold universe, gravity emerges from entanglement and spacetime is discrete, with a fractal structure based on random walk and a non-commutative geometry. When random walk is combined with maximal particle generations, exponential expansion can automatically takes place. Away from maximal generation or in an already concretized spacetime, random walk accounts for a constant or slowing down expansion. Meanwhile, the multi-fold mechanisms also implies a constant expansion potential, adding a force to the expansion of the universe, thanks to uncertainties. It explain the constant acceleration of the universe expansion with a cosmological constant that is not the vacuum energy density but can be way smaller.It may contribute to addressing problems like the absence of any explanation of dark energy, the embarrassing orders of magnitude of discrepancies between vacuum energy and the cosmological constant predicted by conventional Physics; issues that are among Today’s biggest mysteries of the universe. These explanations do not require New Physics beyond the Standard Model and the Standard Cosmology Model.

Sign in / Sign up

Export Citation Format

Share Document