اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدSlow-roll, acceleration, the Big Rip and WKB approximation in NLS-type formulation of scalar field cosmology
483
0
0.0
(
0
)
تأليف
Burin Gumjudpai
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Aspects of non-linear Schr{o}dinger-type (NLS) formulation of scalar (phantom) field cosmology on slow-roll, acceleration, WKB approximation and Big Rip singularity are presented. Slow-roll parameters for the curvature and barotropic density terms are introduced. We reexpress all slow-roll parameters, slow-roll conditions and acceleration condition in NLS form. WKB approximation in the NLS formulation is also discussed when simplifying to linear case. Most of the Schr{o}dinger potentials in NLS formulation are very slowly-varying, hence WKB approximation is valid in the ranges. In the NLS form of Big Rip singularity, two quantities are infinity in stead of three. We also found that approaching the Big Rip, $w_{rm eff}to -1 + {2}/{3q}$, $(q<0)$ which is the same as effective phantom equation of state in the flat case.
قيم البحث
اقرأ أيضاً
In this work, we develop and apply the WKB approximation to several examples of noncommutative quantum cosmology, obtaining the time evolution of the noncommutative universe, this is done starting from a noncommutative quantum formulation of cosmolog
y where the noncommutativity is introduced by a deformation on the minisuperspace variables. This procedure gives a straightforward algorithm to incorporate noncommutativity to cosmology and inflation.
We describe non-flat standard Friedmann cosmology of canonical scalar field with barotropic fluid in form of non-linear Schr{o}dinger-type (NLS) formulation in which all cosmological dynamical quantities are expressed in term of Schr{o}dinger quant
ities as similar to those in time-independent quantum mechanics. We assume the expansion to be superfast, i.e. phantom expansion. We report all Schr{o}dinger-analogous quantities to scalar field cosmology. Effective equation of state coefficient is analyzed and illustrated. We show that in a non-flat universe, there is no fixed $w_{rm eff}$ value for the phantom divide. In a non-flat universe, even $w_{rm eff} > -1$, the expansion can be phantom. Moreover, in open universe, phantom expansion can happen even with $w_{rm eff} > 0$. We also report scalar field exact solutions within frameworks of the Friedmann formulation and the NLS formulation in non-flat universe cases.
We study a relation between the cosmological singularities in classical and quantum theory, comparing the classical and quantum dynamics in some models possessing the Big Brake singularity - the model based on a scalar field and two models based on a
tachyon-pseudo-tachyon field . It is shown that the effect of quantum avoidance is absent for the soft singularities of the Big Brake type while it is present for the Big Bang and Big Crunch singularities. Thus, there is some kind of a classical - quantum correspondence, because soft singularities are traversable in classical cosmology, while the strong Big Bang and Big Crunch singularities are not traversable.
We investigate the complete universe evolution in the framework of $f(T)$ cosmology. We first study the requirements at the kinematic level and we introduce a simple scale factor with the necessary features. Performing a detailed analysis of the phas
e portrait we show that the universe begins in the infinite past from a phase where the scale factor goes to zero but the Hubble parameter goes to a constant, and its derivative to zero. Since these features resemble those of the Pseudo-Rip fate but in a reverted way, we call this initial phase as Pseudo-Bang. Then the universe evolves in a first inflationary phase, a cosmological turnaround and a bounce, after which we have a second inflationary regime with a successful exit. Subsequently we obtain the standard thermal history and the sequence of radiation, matter and late-time acceleration epochs, showing that the universe will result in an everlasting Pseudo-Rip phase. Finally, taking advantage of the fact that the field equations of $f(T)$ gravity are of second order, and therefore the corresponding autonomous dynamical system is one dimensional, we incorporate the aforementioned kinematic features and we reconstruct the specific $f(T)$ form that can dynamically generate the Pseudo-Bang cosmological scenario. Lastly, we examine the evolution of the primordial fluctuations showing that they are initially sub-horizon, and we show that the total fluid does not exhibit any singular behaviour at the phantom crossing points, while the torsional fluid experiences them as Type II singular phases.
We present a complete formulation of the scalar bispectrum in the unified effective field theory (EFT) of inflation, which includes the Horndeski and beyond-Horndeski Gleyzes-Langlois-Piazza-Vernizzi classes, in terms of a set of simple one-dimension
al integrals. These generalized slow-roll expressions remain valid even when slow-roll is transiently violated and encompass all configurations of the bispectrum. We show analytically that our expressions explicitly preserve the squeezed-limit consistency relation beyond slow-roll. As an example application of our results, we compute the scalar bispectrum in a model in which potential-driven G-inflation at early times transitions to chaotic inflation at late times, showing that our expressions accurately track the bispectrum when slow-roll is violated and conventional slow-roll approximations fail.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
