اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدComparing parametric and non-parametric velocity-dependent one-scale models for domain wall evolution
230
0
0.0
(
0
)
تأليف
P. P. Avelino
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We perform a detailed comparison between a recently proposed parameter-free velocity-dependent one-scale model and the standard parametric model for the cosmological evolution of domain wall networks. We find that the latter overestimates the damping of the wall motion due to the Hubble expansion and neglects the direct impact of wall decay on the evolution of the root-mean-square velocity of the network. We show that these effects are significant but may be absorbed into a redefinition of the momentum parameter. We also discuss the implications of these findings for cosmic strings. We compute the energy loss and momentum parameters of the standard parametric model for cosmological domain wall evolution using our non-parametric velocity-dependent one-scale model in the context of cosmological models having a power law evolution of the scale factor $a$ with the cosmic time $t$ ($a propto t^lambda$, $0 < lambda < 1$), and compare with the results obtained from numerical field theory simulations. We further provide simple linear functions which roughly approximate the dependence of the energy loss and momentum parameters on $lambda$.
قيم البحث
اقرأ أيضاً
We develop a parameter-free velocity-dependent one-scale model for the evolution of the characteristic length $L$ and root-mean-square velocity $sigma_v$ of standard domain wall networks in homogeneous and isotropic cosmologies. We compare the fricti
onless scaling solutions predicted by our model, in the context of cosmological models having a power law evolution of the scale factor $a$ as a function of the cosmic time $t$ ($a propto t^lambda$, $0< lambda < 1$), with the corresponding results obtained using field theory numerical simulations. We show that they agree well (within a few $%$) for root-mean-square velocities $sigma_v$ smaller than $0.2 , c$ ($lambda ge 0.9$), where $c$ is the speed of light in vacuum, but significant discrepancies occur for larger values of $sigma_v$ (smaller values of $lambda$). We identify problems with the determination of $L$ and $sigma_v$ from numerical field theory simulations which might potentially be responsible for these discrepancies.
Perturbative quantities, such as the growth rate ($f$) and index ($gamma$), are powerful tools to distinguish different dark energy models or modified gravity theories even if they produce the same cosmic expansion history. In this work, without any
assumption about the dynamics of the Universe, we apply a non-parametric method to current measurements of the expansion rate $H(z)$ from cosmic chronometers and high-$z$ quasar data and reconstruct the growth factor and rate of linearised density perturbations in the non-relativistic matter component. Assuming realistic values for the matter density parameter $Omega_{m0}$, as provided by current CMB experiments, we also reconstruct the evolution of the growth index $gamma$ with redshift. We show that the reconstruction of current $H(z)$ data constrains the growth index to $gamma=0.56 pm 0.12$ (2$sigma$) at $z = 0.09$, which is in full agreement with the prediction of the $Lambda$CDM model and some of its extensions.
The tomographic Alcock-Paczynski (AP) method can result in tight cosmological constraints by using small and intermediate clustering scales of the large scale structure (LSS) of the galaxy distribution. By focusing on the redshift dependence, the AP
distortion can be distinguished from the distortions produced by the redshift space distortions (RSD). In this work, we combine the tomographic AP method with other recent observational datasets of SNIa+BAO+CMB+$H_0$ to reconstruct the dark energy equation-of-state $w$ in a non-parametric form. The result favors a dynamical DE at $zlesssim1$, and shows a mild deviation ($lesssim2sigma$) from $w=-1$ at $z=0.5-0.7$. We find the addition of the AP method improves the low redshift ($zlesssim0.7$) constraint by $sim50%$.
The cosmological jerk parameter $j$ is reconstructed in a non-parametric way from observational data independent of a fiducial cosmological model. From this kinematical quantity, the equation of state parameter for composite matter distribution is al
so found out. The result shows that there is a deviation from the $Lambda$CDM model close to $z=1.5$, at the $3sigma$ confidence level.
Inferring high-fidelity constraints on the spatial curvature parameter, $Omega_{rm K}$, under as few assumptions as possible, is of fundamental importance in cosmology. We propose a method to non-parametrically infer $Omega_{rm K}$ from late-Universe
probes alone. Using Gaussian Processes (GP) to reconstruct the expansion history, we combine Cosmic Chronometers (CC) and Type Ia Supernovae (SNe~Ia) data to infer constraints on curvature, marginalized over the expansion history, calibration of the CC and SNe~Ia data, and the GP hyper-parameters. The obtained constraints on $Omega_{rm K}$ are free from parametric model assumptions for the expansion history, and are insensitive to the overall calibration of both the CC and SNe~Ia data (being sensitive only to relative distances and expansion rates). Applying this method to textit{Pantheon} SNe~Ia and the latest compilation of CCs, we find $Omega_{rm K} = -0.03 pm 0.26$, consistent with spatial flatness at the $mathcal{O}(10^{-1})$ level, and independent of any early-Universe probes. Applying our methodology to future Baryon Acoustic Oscillations and SNe~Ia data from upcoming Stage IV surveys, we forecast the ability to constrain $Omega_{rm K}$ at the $mathcal{O}(10^{-2})$ level.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
