scholarly journals Spinning guest fields during inflation: leftover signatures

2021 ◽  
Vol 2021 (11) ◽  
pp. 047
Author(s):  
Emanuela Dimastrogiovanni ◽  
Matteo Fasiello ◽  
A. Emir Gümrükçüoğlu
Keyword(s):  
Wave Spectrum ◽  
Linear Formulation ◽  
Stability Conditions ◽  
Late Time ◽  
Point Function ◽  
Time Dynamics ◽  
Local Type ◽  
Cosmic Evolution ◽  
Sensitivity Range ◽  
Function Finding

Abstract We consider the possibility of extra spinning particles during inflation, focussing on the spin-2 case. Our analysis relies on the well-known fully non-linear formulation of interacting spin-2 theories. We explore the parameter space of the corresponding inflationary Lagrangian and identify regions therein exhibiting signatures within reach of upcoming CMB probes. We provide a thorough study of the early and late-time dynamics ensuring that stability conditions are met throughout the cosmic evolution. We characterise in particular the gravitational wave spectrum and three-point function finding a local-type non-Gaussianity whose amplitude may be within the sensitivity range of both the LiteBIRD and CMB-S4 experiments.

scholarly journals Impact of Collisional Matter on the Late-Time Dynamics of f(R,T) Gravity

Symmetry ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 463 ◽  
Author(s):  
M. Zubair ◽  
Muhammad Zeeshan ◽  
Syed Hasan ◽  
V. Oikonomou
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
State Parameter ◽  
Gravity Models ◽  
Physical Parameters ◽  
Late Time ◽  
Time Behavior ◽  
Effective Equation ◽  
Time Dynamics ◽  
Cosmic Evolution

We study the cosmic evolution of non-minimally coupled f ( R , T ) gravity in the presence of matter fluids consisting of collisional self-interacting dark matter and radiation. We study the cosmic evolution in the presence of collisional matter, and we compare the results with those corresponding to non-collisional matter and the Λ -cold-dark-matter ( Λ CDM) model. Particularly, for a flat Friedmann–Lema i ^ tre–Robertson–Walker Universe, we study two non-minimally coupled f ( R , T ) gravity models and we focus our study on the late-time dynamical evolution of the model. Our study is focused on the late-time behavior of the effective equation of the state parameter ω e f f and of the deceleration parameter q as functions of the redshift for a Universe containing collisional and non-collisional dark matter fluids, and we compare both models with the Λ CDM model. As we demonstrate, the resulting picture is well accommodated to the latest observational data on the basis of physical parameters.

scholarly journals Averaging generalized scalar field cosmologies II: locally rotationally symmetric Bianchi I and flat Friedmann–Lemaître–Robertson–Walker models

2021 ◽  
Vol 81 (6) ◽  
Author(s):  
Genly Leon ◽  
Sebastián Cuéllar ◽  
Esteban González ◽  
Samuel Lepe ◽  
Claudio Michea ◽  
...  
Keyword(s):  
Scalar Field ◽  
Nonlinear Dynamical Systems ◽  
Perturbation Parameter ◽  
Time Dependent ◽  
Late Time ◽  
De Sitter ◽  
Time Dynamics ◽  
Locally Rotationally Symmetric ◽  
Bianchi I ◽  
Rotationally Symmetric

AbstractScalar field cosmologies with a generalized harmonic potential and a matter fluid with a barotropic equation of state (EoS) with barotropic index $$\gamma $$ γ for the locally rotationally symmetric (LRS) Bianchi I and flat Friedmann–Lemaître–Robertson–Walker (FLRW) metrics are investigated. Methods from the theory of averaging of nonlinear dynamical systems are used to prove that time-dependent systems and their corresponding time-averaged versions have the same late-time dynamics. Therefore, the simplest time-averaged system determines the future asymptotic behavior. Depending on the values of $$\gamma $$ γ , the late-time attractors of physical interests are flat quintessence dominated FLRW universe and Einstein-de Sitter solution. With this approach, the oscillations entering the system through the Klein–Gordon (KG) equation can be controlled and smoothed out as the Hubble parameter H – acting as time-dependent perturbation parameter – tends monotonically to zero. Numerical simulations are presented as evidence of such behavior.

scholarly journals Universal late-time dynamics in isolated one-dimensional statistical systems with topological excitations

2020 ◽  
Vol 101 (10) ◽  
Author(s):  
Alvise Bastianello ◽  
Alessio Chiocchetta ◽  
Leticia F. Cugliandolo ◽  
Andrea Gambassi
Keyword(s):  
Late Time ◽  
One Dimensional ◽  
Topological Excitations ◽  
Time Dynamics ◽  
Statistical Systems

scholarly journals A new method for probing the late-time dynamics in the Lorentzian type IIB matrix model

2017 ◽  
Vol 2017 (8) ◽  
Author(s):  
Takehiro Azuma ◽  
Yuta Ito ◽  
Jun Nishimura ◽  
Asato Tsuchiya
Keyword(s):  
Matrix Model ◽  
New Method ◽  
Late Time ◽  
Time Dynamics

scholarly journals Dynamics of the cerebral blood flow response to brief neural activity in human visual cortex

2019 ◽  
Vol 40 (9) ◽  
pp. 1823-1837 ◽  
Author(s):  
Jung Hwan Kim ◽  
Amanda J Taylor ◽  
Danny JJ Wang ◽  
Xiaowei Zou ◽  
David Ress
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Visual Cortex ◽  
Temporal Dynamics ◽  
Oxygen Metabolism ◽  
Late Time ◽  
Neural Activation ◽  
Hemodynamic Response Function ◽  
Time Dynamics ◽  
Human Visual Cortex

The blood oxygen-level dependent (BOLD) functional magnetic resonance imaging (fMRI) signal depends on an interplay of cerebral blood flow (CBF), oxygen metabolism, and cerebral blood volume. Despite wide usage of BOLD fMRI, it is not clear how these physiological components create the BOLD signal. Here, baseline CBF and its dynamics evoked by a brief stimulus (2 s) in human visual cortex were measured at 3T. We found a stereotypical CBF response: immediate increase, rising to a peak a few second after the stimulus, followed by a significant undershoot. The BOLD hemodynamic response function (HRF) was also measured in the same session. Strong correlations between HRF and CBF peak responses indicate that the flow responses evoked by neural activation in nearby gray matter drive the early HRF. Remarkably, peak CBF and HRF were also strongly modulated by baseline perfusion. The CBF undershoot was reliable and significantly correlated with the HRF undershoot. However, late-time dynamics of the HRF and CBF suggest that oxygen metabolism can also contribute to the HRF undershoot. Combined measurement of the CBF and HRF for brief neural activation is a useful tool to understand the temporal dynamics of neurovascular and neurometabolic coupling.

scholarly journals Space–Time Wave Extremes: The Role of Metocean Forcings

2015 ◽  
Vol 45 (7) ◽  
pp. 1897-1916 ◽  
Author(s):  
Francesco Barbariol ◽  
Alvise Benetazzo ◽  
Sandro Carniel ◽  
Mauro Sclavo
Keyword(s):  
Wind Speed ◽  
Wave Spectrum ◽  
Domain Size ◽  
Space Time ◽  
Statistical Prediction ◽  
Random Wave ◽  
Spectral Parameters ◽  
Frequency Spectra ◽  
Space Domain ◽  
Time Dynamics

AbstractWave observations and modeling have recently demonstrated that wave extremes of short-crested seas are poorly predicted by statistics of time records. Indeed, the highest waves pertain to wave groups at focusing that have space–time dynamics. Therefore, the statistical prediction of extremes of short-crested sea states should rely on the multidimensional random wave fields’ assumption. To adapt wave extreme statistics to the space–time domain, theoretical models using parameters of the directional wave spectrum have been recently developed. In this paper, the influence of metocean forcings (wind conditions, ambient current, and bottom depth) on these parameters and hence on wave extremes is studied with a twofold strategy. First, parametric spectral formulations [Pierson–Moskowitz and Joint North Sea Wave Project (JONSWAP) frequency spectra with cos2 directional distribution function] are considered to represent the dependence of wave extremes upon wind speed, fetch, and space domain size. Afterward, arbitrary conditions are simulated by using the SWAN numerical model adapted to store the spectral parameters, and the effects on extremes of current- and depth-induced shoaling are investigated. Preliminarily, the space–time extremes prediction model adopted is assessed by means of numerical simulations of Gaussian random seas. Compared to the significant wave height of the sea state and for a given space domain size, results show that space–time extremes are enhanced by opposite currents, whereas they are weakened by increasing wind conditions (wind speed and fetch) and by depth-induced shoaling. In this respect, the remarkable contribution to wave extremes of the size of the space domain is substantiated.

Effect of Stationary Particles on the Phase Separation of Binary Fluids

2001 ◽  
Vol 710 ◽  
Author(s):  
Domenico Suppa ◽  
Olga Kuksenok ◽  
Anna C. Balazs ◽  
J.M. Yeomans
Keyword(s):  
Two Dimensions ◽  
Lattice Boltzmann Model ◽  
Late Time ◽  
Binary Fluids ◽  
Final Size ◽  
Time Dynamics ◽  
Simple Theoretical Model ◽  
Boltzmann Model ◽  
Fluid Interaction ◽  
Kinetics Of

ABSTRACTPhase separating binary fluids with the addition of immobile particles, which act as osmotic force centres, were simulated using a Lattice Boltzmann model in two dimensions. In the hydrodynamic over-damped limit, where the flow is entirely driven by capillary effects, the presence of particles that are preferentially wetted by one of the fluid components significantly affects the kinetics of the growth of the fluid domains. The late time dynamics is governed by the wetting interactions and the final size of the domains can be tailored by varying the strength of the particles-fluid interaction as well as the particles concentration. These features are predicted within a simple theoretical model and are amenable of experimental checks.

scholarly journals Yang-Baxter integrable Lindblad equations

2020 ◽  
Vol 8 (3) ◽  
Author(s):  
Aleksandra A. Ziolkowska ◽  
Fabian Essler
Keyword(s):  
Bethe Ansatz ◽  
Quantum Spin ◽  
Spin Chains ◽  
Integrable Models ◽  
Late Time ◽  
Quantum Spin Chains ◽  
Operator Formalism ◽  
One Dimensional ◽  
Time Dynamics

We consider Lindblad equations for one dimensional fermionic models and quantum spin chains. By employing a (graded) super-operator formalism we identify a number of Lindblad equations than can be mapped onto non-Hermitian interacting Yang-Baxter integrable models. Employing Bethe Ansatz techniques we show that the late-time dynamics of some of these models is diffusive.

scholarly journals COSMOLOGICAL DYNAMICS OF MODIFIED GRAVITY WITH A NONMINIMAL CURVATURE-MATTER COUPLING

2014 ◽  
Vol 23 (02) ◽  
pp. 1450021 ◽  
Author(s):  
TAHEREH AZIZI ◽  
EMAD YARAIE
Keyword(s):  
Modified Gravity ◽  
System Approach ◽  
Lagrangian Density ◽  
State Parameter ◽  
Late Time ◽  
Effective Equation ◽  
Matter Coupling ◽  
Cosmic Evolution ◽  
Modified Gravity Theory ◽  
Attractor Solution

We perform a phase space analysis of a nonminimally coupled modified gravity theory with the Lagrangian density of the form [Formula: see text], where f1(R) and f2(R) are arbitrary functions of the curvature scalar R and [Formula: see text] is the matter Lagrangian density. We apply the dynamical system approach to this scenario in two particular models. In the first model we assume f1(R) = 2R with a general form for f2(R) and set favorable values for effective equation of state parameter which is related to the several epochs of the cosmic evolution and study the critical points and their stability in each cosmic eras. In the second case, we allow the f1(R) to be an arbitrary function of R and set f2(R) = 2R. We find the late-time attractor solution for the model and show that this model has a late-time accelerating epoch and an acceptable matter era.

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