scholarly journals The Effect of de-Sitter Like Background on Increasing the Zero Point Budget of Dark Energy

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Haidar Sheikhahmadi ◽  
Ali Aghamohammadi ◽  
Khaled Saaidi
Keyword(s):  
Scalar Field ◽  
Energy Density ◽  
Quantum Fluctuations ◽  
Zero Point ◽  
Scalar Fields ◽  
Massless Scalar Field ◽  
De Sitter ◽  
Data Set ◽  
Massive Scalar Field ◽  
The Universe

During this work, using subtraction renormalization mechanism, zero point quantum fluctuations for bosonic scalar fields in a de-Sitter like background are investigated. By virtue of the observed value for spectral index,ns(k), for massive scalar field the best value for the first slow roll parameter,ϵ, is achieved. In addition, the energy density of vacuum quantum fluctuations for massless scalar field is obtained. The effects of these fluctuations on other components of the universe are studied. By solving the conservation equation, for some different examples, the energy density for different components of the universe is obtained. In the case which all components of the universe are in an interaction, the different dissipation functions,Q~i, are considered. The time evolution ofρDE(z)/ρcri(z)shows thatQ~=3γH(t)ρmhas the best agreement in comparison to observational data including CMB, BAO, and SNeIa data set.

scholarly journals ZERO-POINT ENERGY OF MASSLESS SCALAR FIELDS IN THE PRESENCE OF SOFT AND SEMIHARD BOUNDARIES IN D DIMENSIONS

1999 ◽  
Vol 14 (13) ◽  
pp. 2077-2089 ◽  
Author(s):  
F. CARUSO ◽  
R. DE PAOLA ◽  
N. F. SVAITER
Keyword(s):  
Scalar Field ◽  
Energy Density ◽  
Zero Point ◽  
Scalar Fields ◽  
Flat Space ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Zero Point Energy ◽  
Point Energy ◽  
Renormalized Energy

The renormalized energy density of a massless scalar field defined in a D-dimensional flat space–time is computed in the presence of "soft" and "semihard" boundaries, modeled by some smoothly increasing potential functions. The sign of the renormalized energy densities for these different confining situations is investigated. The dependence of this energy on D for the cases of "hard" and "soft/semihard" boundaries are compared.

scholarly journals Condensation of a scalar field non-minimally coupled to gravity in a cosmological context

2020 ◽  
Vol 35 (32) ◽  
pp. 2050270
Author(s):  
Amir Ghalee
Keyword(s):  
Scalar Field ◽  
Energy Density ◽  
Condensed Phase ◽  
Condensed State ◽  
De Sitter ◽  
Cosmological Perturbations ◽  
Cosmological Context ◽  
Background Density ◽  
The Universe ◽  
Bonnet Term

We present a new mechanism to condense a scalar field coupled to the Gauss–Bonnet term. We propose a scenario in which the condensed state will emerge from the background energy density in the late-Universe. During the radiation and dust-dominated eras, the energy density of the scalar field, [Formula: see text], decreases at a slower rate than the background density. Eventually, [Formula: see text] dominates over the energy density of dust and the scalar field could be condensed. In the condensed phase, we have the de Sitter phase for the universe with [Formula: see text]. Moreover, we study the cosmological perturbations of the model and explore predictions of the model.

Some interactions of spherically symmetric massive scalar field with Brans–Dicke scalar field in Robertson–Walker universe

2019 ◽  
Vol 16 (04) ◽  
pp. 1950066 ◽  
Author(s):  
Kangujam Priyokumar Singh ◽  
Rajshekhar Roy Baruah
Keyword(s):  
Scalar Field ◽  
Cosmic Time ◽  
Scalar Fields ◽  
Cosmological Term ◽  
Physical Parameters ◽  
Spherically Symmetric ◽  
Massive Scalar ◽  
Field Equations ◽  
Massive Scalar Field ◽  
The Universe

Here in this work, we investigated the possible cosmological consequences of the interaction of Brans–Dicke scalar field and massive scalar field by considering spherically symmetric Robertson–Walker metric. The present problem can also be treated as an extension work of [K. Priyokumar et al., Interaction of gravitational field and Brans–Dicke field, Res. Astron. Astrophys. 16(4) (2016) 64; K. Priyokumar and M. Dewri, Interaction of electromagnetic field and Brans–Dicke field, Chinease J. Phys. 54 (2016) 845]. The exact solutions of the field equations are obtained with seven different cases. The behavior of the model and their contribution to the process of the evolution are examined in detail from some explicit and reasonable values of free parameter. We also presented the variations of certain physical parameters versus cosmic time graphically to compare our solutions with the present observational findings. When we studied further, it is found that the cosmological term [Formula: see text] takes a great role in the accelerating expansion of our universe when both scalar fields are exponentially increasing functions of time, while the cosmological term will not appear in the case when both the scalar fields are exponentially decreasing functions of time. Also, the scalar field is seen to have a tendency to increase the expansion of the universe, thereby flattening the universe.

scholarly journals QUANTUM FLUCTUATIONS FOR A SCALAR FIELD IN THE SPACE–TIME OF GRAVITATIONAL IMPLUSIVE WAVE

1998 ◽  
Vol 13 (08) ◽  
pp. 1201-1211 ◽  
Author(s):  
Y. ENGINER ◽  
M. HORTAÇSU ◽  
N. ÖZDEMIR
Keyword(s):  
Scalar Field ◽  
Gravitational Waves ◽  
Quantum Fluctuations ◽  
De Sitter Space ◽  
Space Time ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
De Sitter

Quantum fluctuations for a massless scalar field in the background metric of spherical implusive gravitational waves propagating through Minkowski and de Sitter spaces are investigated. It is shown that there exist finite fluctuations for de Sitter space.

scholarly journals LATE-TIME TAIL OF A COUPLED SCALAR FIELD IN THE BACKGROUND OF A BLACK HOLE WITH A GLOBAL MONOPOLE

2008 ◽  
Vol 23 (05) ◽  
pp. 359-369 ◽  
Author(s):  
SONGBAI CHEN ◽  
JILIANG JING
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Late Time ◽  
Massless Scalar Field ◽  
Global Monopole ◽  
Massive Scalar Field ◽  
Gravitational Fields ◽  
Field Decay

Using the technique of spectral decomposition, we investigated the late-time tails of massless and massive coupled scalar fields in the background of a black hole with a global monopole. We found that due to the existence of the coupling between the scalar and gravitational fields, the massless scalar field decay faster at timelike infinity i+, and so does the massive one in the intermediate late time. But the asymptotically late-time tail for the massive scalar field is not affected and its decay rate is still t-5/6.

scholarly journals Unruh-DeWitt detector responses for complex scalar fields in de Sitter spacetime

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Md Sabir Ali ◽  
Sourav Bhattacharya ◽  
Kinjalk Lochan
Keyword(s):  
Scalar Field ◽  
Response Function ◽  
Scalar Fields ◽  
Detector Response ◽  
Massless Scalar Field ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Complex Scalar ◽  
Sitter Spacetime ◽  
Complex Scalar Field

Abstract We derive the response function for a comoving, pointlike Unruh-DeWitt particle detector coupled to a complex scalar field ϕ, in the (3 + 1)-dimensional cosmological de Sitter spacetime. The field-detector coupling is taken to be proportional to ϕ†ϕ. We address both conformally invariant and massless minimally coupled scalar field theories, respectively in the conformal and the Bunch-Davies vacuum. The response function integral for the massless minimal complex scalar, not surprisingly, shows divergences and accordingly we use suitable regularisation scheme to find out well behaved results. The regularised result also contains a de Sitter symmetry breaking logarithm, growing with the cosmological time. Possibility of extension of these results with the so called de Sitter α-vacua is discussed. While we find no apparent problem in computing the response function for a real scalar in these vacua, a complex scalar field is shown to contain some possible ambiguities in the detector response. The case of the minimal and nearly massless scalar field theory is also briefly discussed.

scholarly journals Quasinormal modes and their anomalous behavior for black holes in f(R) gravity

2021 ◽  
Vol 81 (5) ◽  
Author(s):  
Almendra Aragón ◽  
P. A. González ◽  
Eleftherios Papantonopoulos ◽  
Yerko Vásquez
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Critical Mass ◽  
Quasinormal Modes ◽  
Scalar Fields ◽  
Critical Value ◽  
Anomalous Behavior ◽  
Modified Theories Of Gravity ◽  
De Sitter ◽  
Massive Scalar Field

AbstractWe study the propagation of scalar fields in the background of an asymptotically de Sitter black hole solution in f(R) gravity. The aim of this work is to analyze in modified theories of gravity the existence of an anomalous decay rate of the quasinormal modes (QNMs) of a massive scalar field which was recently reported in Schwarzschild black hole backgrounds, in which the longest-lived modes are the ones with higher angular number, for a scalar field mass smaller than a critical value, while that beyond this value the behavior is inverted. We study the QNMs for various overtone numbers and they depend on a parameter $$\beta $$ β which appears in the metric and characterizes the f(R) gravity. For small $$\beta $$ β , i.e. small deviations from the Schwarzschild–dS black hole the anomalous behavior in the QNMs is present for the photon sphere modes, and the critical value of the mass of the scalar field depends on the parameter $$\beta $$ β while for large $$\beta $$ β , i.e. large deviations, the anomalous behavior and the critical mass does not appear. Also, the critical mass of the scalar field increases when the overtone number increases until the f(R) gravity parameter $$\beta $$ β approaches the near extremal limit at which the critical mass of the scalar field does not depend anymore on the overtone number. The imaginary part of the quasinormal frequencies is always negative leading to a stable propagation of the scalar fields in this background.

Scalar fields in f(G) gravity

2020 ◽  
Vol 17 (09) ◽  
pp. 2050132
Author(s):  
Dog̃ukan Taṣer ◽  
Melis Ulu Dog̃ru
Keyword(s):  
Scalar Field ◽  
Bianchi Type ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Type I ◽  
Massless Scalar Field ◽  
Field Equations ◽  
Massive Scalar Field ◽  
Scalar Field Models ◽  
Bianchi Type I Universe

In this study, we investigated scalar field in [Formula: see text]-gravity by using LRS Bianchi type-I universe. Massless and massive scalar field models are separately constructed in [Formula: see text]-gravity. Massless scalar field models are examined in the cases of constant and exponential potential fields. For all models, solutions of field equations are obtained under the consideration of [Formula: see text]. [Formula: see text] functions for each model are separately attained in theory. It is shown that constructed models in the presence of massless scalar field permit quintessence scalar field. Also, it is observed that each model indicates expanding universe with deceleration. Also, kinematical quantities are analyzed in the light of obtained solutions. All models are concluded with a geometric and physical perspective.

scholarly journals THE CASIMIR FORCE OF QUANTUM SPRING IN THE (D+1)-DIMENSIONAL SPACETIME

2011 ◽  
Vol 26 (09) ◽  
pp. 669-679 ◽  
Author(s):  
XIANG-HUA ZHAI ◽  
XIN-ZHOU LI ◽  
CHAO-JUN FENG
Keyword(s):  
Scalar Field ◽  
Casimir Force ◽  
Casimir Effect ◽  
Dimensional Space ◽  
Scalar Fields ◽  
Casimir Energy ◽  
Massless Scalar Field ◽  
Massive Scalar ◽  
Massive Scalar Field ◽  
Dimensional Spacetime

The Casimir effect for a massless scalar field on the helix boundary condition which is named as quantum spring is studied in our recent paper.27 Here, the Casimir effect of the quantum spring is investigated in (D+1)-dimensional spacetime for the massless and massive scalar fields by using the zeta function techniques. We obtain the exact results of the Casimir energy and Casimir force for any D, which indicate a Z2 symmetry of the two space dimensions. The Casimir energy and Casimir force have different expressions for odd and even dimensional space in the massless case but in both cases the force is attractive. In the case of odd-dimensional space, the Casimir energy density can be expressed by the Bernoulli numbers, while in the even case it can be expressed by the ζ-function. And we also show that the Casimir force has a maximum value which depends on the spacetime dimensions. In particular, for a massive scalar field, we found that the Casimir force varies as the mass of the field changes.

scholarly journals CASIMIR PISTONS FOR MASSIVE SCALAR FIELDS

2009 ◽  
Vol 24 (05) ◽  
pp. 393-400 ◽  
Author(s):  
XIANG-HUA ZHAI ◽  
YAN-YAN ZHANG ◽  
XIN-ZHOU LI
Keyword(s):  
Scalar Field ◽  
Casimir Force ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Two Dimensional ◽  
Massive Scalar ◽  
Regularization Technique ◽  
Massive Scalar Field ◽  
Physical Result

The Casimir force on two-dimensional pistons for massive scalar fields with both Dirichlet and hybrid boundary conditions is computed. The physical result is obtained by making use of generalized ζ-function regularization technique. The influence of the mass and the position of the piston in the force is studied graphically. The Casimir force for massive scalar field is compared to that for massless scalar field.

Sign in / Sign up

Export Citation Format

Share Document