scholarly journals Inflationary limits on the size of compact extra space

2019 ◽  
Vol 28 (13) ◽  
pp. 1941004 ◽  
Author(s):  
V. V. Nikulin ◽  
Sergey G. Rubin
Keyword(s):  
Scalar Field ◽  
Planck Mass ◽  
Extra Space ◽  
Inflationary Models ◽  
Kaluza Klein

We study restrictions imposed on the parameters of the Kaluza–Klein extra space supplied by the standard inflationary models. It is shown that the size of the extra space cannot be larger than [Formula: see text][Formula: see text]cm and the [Formula: see text]-dimensional Planck mass should be larger than [Formula: see text][Formula: see text]GeV. The validity of these estimates is discussed. We also study creation of stable excitations of scalar field as the result of the extra metric evolution.

scholarly journals SPECTRA OF RELIC GRAVITONS AND BRANS–DICKE THEORY

2005 ◽  
Vol 20 (02) ◽  
pp. 127-134 ◽  
Author(s):  
B. K. SAHOO
Keyword(s):  
Scalar Field ◽  
Energy Density ◽  
Time Dependence ◽  
Gravitational Waves ◽  
Hubble Parameter ◽  
Frequency Dependent ◽  
Cosmological Expansion ◽  
Relic Gravitational Waves ◽  
Matter Energy ◽  
Inflationary Models

The spectra of relic gravitational waves produced as a result of cosmological expansion of the inflationary models are derived in Brans–Dicke (BD) theory of gravity. The time dependence of the very early Hubble parameter and matter energy density are derived from frequency-dependent spectrum of relic gravitational waves. Also it is found that Brans–Dicke scalar field contributes to the energy density of relic gravitons.

scholarly journals Nonlinear Schrödinger-type formulation of scalar field cosmology: Two barotropic fluids and exact solutions

2020 ◽  
Vol 35 (19) ◽  
pp. 2050157
Author(s):  
Chonticha Kritpetch ◽  
Jarunee Sanongkhun ◽  
Pichet Vanichchapongjaroen ◽  
Burin Gumjudpai
Keyword(s):  
Scalar Field ◽  
Exact Solutions ◽  
Time Dependent ◽  
Frw Cosmology ◽  
Dependent Case ◽  
Nonlinear Schrödinger ◽  
Barotropic Fluids ◽  
Scalar Field Cosmology ◽  
Formulation Variables ◽  
Canonical Scalar Field

Time-independent nonlinear Schrödinger-type (NLS) formulation of FRW cosmology with canonical scalar field is considered in the case of two barotropic fluids. We derived Friedmann formulation variables in terms of NLS variables. Seven exact solutions found by D’Ambroise [Ph.D. thesis, arXiv:1005.1410 ] and one new found solution are explored and tested in cosmology. The result suggests that time-independent NLS formulation of cosmology case should be upgraded to the time-dependent case.

scholarly journals Canonical scalar field inflation with string and R2-corrections

2021 ◽  
Vol 424 ◽  
pp. 168359
Author(s):  
S.D. Odintsov ◽  
V.K. Oikonomou ◽  
F.P. Fronimos
Keyword(s):  
Scalar Field ◽  
Canonical Scalar Field

scholarly journals α-Attractors and reheating in a nonminimal inflationary model

2020 ◽  
Vol 29 (10) ◽  
pp. 2050077
Author(s):  
R. Shojaee ◽  
K. Nozari ◽  
F. Darabi
Keyword(s):  
Scalar Field ◽  
Spectral Index ◽  
Parameter Space ◽  
Model Potential ◽  
Index Formula ◽  
Inflationary Model ◽  
Scalar Spectral Index ◽  
Canonical Scalar Field

We study [Formula: see text]-attractor models with both E-model and T-model potential in an extended Nonminimal Derivative (NMD) inflation where a canonical scalar field and its derivatives are nonminimally coupled to gravity. We calculate the evolution of perturbations during this regime. Then by adopting inflation potentials of the model we show that in the large [Formula: see text] and small [Formula: see text] limit, the value of the scalar spectral index [Formula: see text] and tensor-to-scalar ratio [Formula: see text] are universal. Next, we study reheating after inflation in this formalism. We obtain some constraints on the model’s parameter space by adopting the results with Planck 2018.

scholarly journals THE PHYSICS OF 2D STRINGY SPACETIMES

1992 ◽  
Vol 01 (02) ◽  
pp. 335-354 ◽  
Author(s):  
G.W. GIBBONS ◽  
MALCOLM J. PERRY
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
String Theory ◽  
Nontrivial Solution ◽  
Heterotic String ◽  
Two Dimensional ◽  
Dilaton Field ◽  
Black Hole Spacetime ◽  
Canonical Scalar Field

We examine the two-dimensional spacetimes that emerge from string theory. We find all of the solutions with no tachyons, and show that the only nontrivial solution is the black-hole spacetime. We examine the role of duality in this picture. We then explore the thermodynamics of these solutions which is complicated by the fact that only in two spacetime dimensions is it impossible to redefine the dilaton field in terms of a canonical scalar field. Finally, we extend our analysis to the heterotic string, and briefly comment on exact, as opposed to perturbative, solutions.

Scalar field potential in inflationary models: Reconstruction and further constraints

1995 ◽  
Vol 51 (12) ◽  
pp. 6722-6735 ◽  
Author(s):  
Fred C. Adams ◽  
Katherine Freese
Keyword(s):  
Scalar Field ◽  
Field Potential ◽  
Inflationary Models

scholarly journals EVOLUTION OF NON-GAUSSIANITY IN MULTI-SCALAR FIELD MODELS

2011 ◽  
Vol 03 ◽  
pp. 203-214 ◽  
Author(s):  
JOSEPH ELLISTON ◽  
DAVID MULRYNE ◽  
DAVID SEERY ◽  
REZA TAVAKOL
Keyword(s):  
Scalar Field ◽  
Inflection Point ◽  
Adiabatic Limit ◽  
Point Model ◽  
Curvature Perturbation ◽  
Peak Magnitude ◽  
Scalar Field Models ◽  
Multiple Field ◽  
Inflationary Models

We study the evolution of non-Gaussianity in multiple-field inflationary models, focusing on three fundamental questions: (a) How is the sign and peak magnitude of the non-linearity parameter f NL related to generic features in the inflationary potential? (b) How sensitive is f NL to the process by which an adiabatic limit is reached, where the curvature perturbation becomes conserved? (c) For a given model, what is the appropriate tool – analytic or numerical – to calculate f NL at the adiabatic limit? We summarise recent results obtained by the authors and further elucidate them by considering an inflection point model.

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