scholarly journals A New Mechanism for Generating Particle Number Asymmetry through Interactions

2019 ◽  
Vol 2019 ◽  
pp. 1-28
Author(s):  
Takuya Morozumi ◽  
Keiko I. Nagao ◽  
Apriadi Salim Adam ◽  
Hiroyuki Takata
Keyword(s):  
Scalar Field ◽  
Particle Number ◽  
Initial Conditions ◽  
Particle Energy ◽  
Expansion Rate ◽  
Initial Time ◽  
Initial Condition ◽  
Complex Scalar ◽  
Neutral Scalar ◽  
The Universe

A new mechanism for generating particle number asymmetry (PNA) has been developed. This mechanism is realized with a Lagrangian including a complex scalar field and a neutral scalar field. The complex scalar carries U(1) charge which is associated with the PNA. It is written in terms of the condensation and Green’s function, which is obtained with two-particle irreducible (2PI) closed time path (CTP) effective action (EA). In the spatially flat universe with a time-dependent scale factor, the time evolution of the PNA is computed. We start with an initial condition where only the condensation of the neutral scalar is nonzero. The initial condition for the fields is specified by a density operator parameterized by the temperature of the universe. With the above initial conditions, the PNA vanishes at the initial time and later it is generated through the interaction between the complex scalar and the condensation of the neutral scalar. We investigate the case that both the interaction and the expansion rate of the universe are small and include their effects up to the first order of the perturbation. The expanding universe causes the effects of the dilution of the PNA, freezing interaction, and the redshift of the particle energy. As for the time dependence of the PNA, we found that PNA oscillates at the early time and it begins to dump at the later time. The period and the amplitude of the oscillation depend on the mass spectrum of the model, the temperature, and the expansion rate of the universe.

scholarly journals Higher-order Lagrangian perturbative theory for the Cosmic Web

2014 ◽  
Vol 11 (S308) ◽  
pp. 119-120
Author(s):  
Takayuki Tatekawa ◽  
Shuntaro Mizuno
Keyword(s):  
Perturbation Theory ◽  
Fourth Order ◽  
Initial Conditions ◽  
Higher Order ◽  
Order Perturbation ◽  
Initial Condition ◽  
The Difference ◽  
Fifth Order ◽  
The Universe ◽  
Higher Order Lagrangian

AbstractZel'dovich proposed Lagrangian perturbation theory (LPT) for structure formation in the Universe. After this, higher-order perturbative equations have been derived. Recently fourth-order LPT (4LPT) have been derived by two group. We have shown fifth-order LPT (5LPT) In this conference, we notice fourth- and more higher-order perturbative equations. In fourth-order perturbation, because of the difference in handling of spatial derivative, there are two groups of equations. Then we consider the initial conditions for cosmological N-body simulations. Crocce, Pueblas, and Scoccimarro (2007) noticed that second-order perturbation theory (2LPT) is required for accuracy of several percents. We verify the effect of 3LPT initial condition for the simulations. Finally we discuss the way of further improving approach and future applications of LPTs.

Exact solutions for scalar field cosmology in f(R) gravity

2017 ◽  
Vol 32 (30) ◽  
pp. 1750164 ◽  
Author(s):  
S. D. Maharaj ◽  
R. Goswami ◽  
S. V. Chervon ◽  
A. V. Nikolaev
Keyword(s):  
Scalar Field ◽  
Exact Solutions ◽  
Scalar Curvature ◽  
Evolution Equations ◽  
Initial Conditions ◽  
De Sitter ◽  
Airy Functions ◽  
Special Cases ◽  
The Universe ◽  
Current Stage

We study scalar field FLRW cosmology in the content of f(R) gravity. Our consideration is restricted to the spatially flat Friedmann universe. We derived the general evolution equations of the model, and showed that the scalar field equation is automatically satisfied for any form of the f(R) function. We also derived representations for kinetic and potential energies, as well as for the acceleration in terms of the Hubble parameter and the form of the f(R) function. Next we found the exact cosmological solutions in modified gravity without specifying the f(R) function. With negligible acceleration of the scalar curvature, we found that the de Sitter inflationary solution is always attained. Also we obtained new solutions with special restrictions on the integration constants. These solutions contain oscillating, accelerating, decelerating and even contracting universes. For further investigation, we selected special cases which can be applied with early or late inflation. We also found exact solutions for the general case for the model with negligible acceleration of the scalar curvature in terms of special Airy functions. Using initial conditions which represent the universe at the present epoch, we determined the constants of integration. This allows for the comparison of the scale factor in the new solutions with that for current stage of the universe evolution in the [Formula: see text]CDM model.

scholarly journals Complex Inflaton Field in Quantum Cosmology

1997 ◽  
Vol 06 (06) ◽  
pp. 649-671 ◽  
Author(s):  
A. Yu. Kamenshchik ◽  
I. M. Khalatnikov ◽  
A. V. Toporensky
Keyword(s):  
Scalar Field ◽  
Cosmological Model ◽  
Equations Of Motion ◽  
Inflationary Cosmology ◽  
Complex Scalar ◽  
Inflaton Field ◽  
Absolute Value ◽  
Forbidden Regions ◽  
Complex Scalar Field ◽  
The Universe

We investigate the cosmological model with the complex scalar self-interacting inflaton field non-minimally coupled to gravity. The different geometries of the Euclidean classically forbidden regions are represented. The instanton solutions of the corresponding Euclidean equations of motion are found by numerical calculations supplemented by the qualitative analysis of Lorentzian and Euclidean trajectories. The applications of these solutions to the no-boundary and tunneling proposals for the wave function of the Universe are studied. Possible interpretation of obtained results and their connection with inflationary cosmology is discussed. The restrictions on the possible values of the new quasifundamental constant of the theory — non-zero classical charge — are obtained. The equations of motion for the generalized cosmological model with complex scalar field are written down and investigated. The conditions of the existence of instanton solutions corresponding to permanent values of an absolute value of scalar field are obtained.

scholarly journals ON THE TRANSITION FROM COMPLEX TO REAL SCALAR FIELDS IN MODERN COSMOLOGY

2011 ◽  
Vol 08 (08) ◽  
pp. 1815-1832 ◽  
Author(s):  
GIAMPIERO ESPOSITO ◽  
RAJU ROYCHOWDHURY ◽  
CLAUDIO RUBANO ◽  
PAOLO SCUDELLARO
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Scalar Fields ◽  
Complex Nature ◽  
Complex Scalar ◽  
Real Scalar ◽  
Symmetry Approach ◽  
Modern Cosmology ◽  
Complex Scalar Field ◽  
The Universe

We study some problems arising from the introduction of a complex scalar field in cosmology, modeling its possible behaviors in both the inflationary and dark energy stages of the universe. Such examples contribute to show that, while the complex nature of the scalar field can be indeed important during inflation, it loses its meaning in the later dark-energy dominated era of cosmology, when the phase of the complex field is practically constant, and there is indeed a transition from complex to real scalar field. In our considerations, the Noether symmetry approach turns out to be a useful tool once again. We arrive eventually at a potential containing the sixth and fourth powers of the scalar field, and the resulting semiclassical quantum cosmology is studied to gain a better understanding of the inflationary stage.

scholarly journals NON-MARKOVIAN SOURCE TERM FOR PARTICLE PRODUCTION BY A SELF-INTERACTING SCALAR FIELD IN THE LARGE-N APPROXIMATION

2005 ◽  
Vol 20 (14) ◽  
pp. 1087-1101
Author(s):  
FUAD M. SARADZHEV
Keyword(s):  
Scalar Field ◽  
Particle Production ◽  
Particle Number ◽  
Source Term ◽  
Particle Number Density ◽  
Back Reaction ◽  
Number Density ◽  
Complex Scalar ◽  
Large N ◽  
Complex Scalar Field

The particle production in the self-interacting N-component complex scalar field theory is studied at large N. A non-Markovian source term that includes all higher order back-reaction and collision effects is derived. The kinetic amplitudes accounting for the change in the particle number density caused by collisions are obtained. It is shown that the production of particles is symmetric in the momentum space. The problem of renormalization is briefly discussed.

scholarly journals THE GENERALITY OF INFLATION IN SOME CLOSED FRW MODELS WITH A SCALAR FIELD

2002 ◽  
Vol 11 (06) ◽  
pp. 805-816 ◽  
Author(s):  
S. A. PAVLUCHENKO ◽  
A. V. TOPORENSKY ◽  
N. YU. SAVCHENKO
Keyword(s):  
Scalar Field ◽  
Perfect Fluid ◽  
Initial Condition ◽  
Frw Universe ◽  
Complex Scalar ◽  
Complex Scalar Field ◽  
Frw Models

The generality of inflation in closed FRW Universe is studied for the models with a scalar field on a brane and with a complex scalar field. The results obtained are compared with the previously known results for the model with a scalar field and a perfect fluid. The influence of the measure chosen in the initial condition space on the ratio of inflationary solution is described.

scholarly journals QUANTIZATION OF THE BIANCHI TYPE IX MODEL IN N=1 SUPERGRAVITY IN THE PRESENCE OF SUPERMATTER

1996 ◽  
Vol 11 (10) ◽  
pp. 1763-1795 ◽  
Author(s):  
P.V. MONIZ
Keyword(s):  
Wave Function ◽  
Scalar Field ◽  
General Theory ◽  
Bianchi Type ◽  
Two Dimensional ◽  
Kahler Geometry ◽  
Complex Scalar ◽  
Analytical Potential ◽  
Complex Scalar Field ◽  
The Universe

The general theory of N=1 supergravity with supermatter is applied to a Bianchi type IX diagonal model. The supermatter is constituted by a complex scalar field and its [Formula: see text] fermionic partners. The Kähler geometry is chosen to be a two-dimensional flat one. The Lorentz-invariant ansatz for the wave function of the universe is taken to be as simple as possible in order to obtain new solutions. The set of differential equations derived from the quantum constraints are analyzed in two different cases: if the supermatter terms include an analytical potential or not. In the latter the wave function is found to have a simple form.

scholarly journals QUANTUM REMNANT AS DARK ENERGY AND DARK MATTER

2011 ◽  
Vol 01 ◽  
pp. 277-284
Author(s):  
SANG PYO KIM ◽  
SEOKTAE KOH
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Uncertainty Principle ◽  
Dark Energy Model ◽  
Quantum Fluctuations ◽  
Complex Scalar ◽  
Linear Perturbations ◽  
Complex Scalar Field ◽  
The Universe

We study the quantum remnant of a scalar field protected by the uncertainty principle. The quantum remnant that survived the later stage of evolution of the universe may provide dark energy and dark matter depending on the potential. Though the quantum remnant shares some useful property of complex scalar field (spintessence) dark energy model, quantum fluctuations are still unstable to the linear perturbations for V ~ ϕq with q < 1 as in the spintessence model.

scholarly journals ACCELERATION IN WEYL INTEGRABLE SPACETIME

2013 ◽  
Vol 22 (05) ◽  
pp. 1350019 ◽  
Author(s):  
JOHN MIRITZIS
Keyword(s):  
Scalar Field ◽  
Initial Conditions ◽  
Accelerated Expansion ◽  
Phantom Field ◽  
Wide Range ◽  
Expansion Of The Universe ◽  
The Universe

We study homogeneous and isotropic cosmologies in a Weyl spacetime. It is shown that in Weyl integrable spacetime, the corresponding scalar field may act as a phantom field. In this circumstance the Weyl field gives rise to a late accelerated expansion of the universe for all initial conditions and for a wide range of the parameters.

scholarly journals Consistent Initial Conditions for the Saint-Venant Equations in River Network Modeling

2017 ◽  
Author(s):  
Cheng-Wei Yu ◽  
Frank Liu ◽  
Ben R. Hodges
Keyword(s):  
Steady State ◽  
Initial Conditions ◽  
River Network ◽  
Initial Time ◽  
Initial Condition ◽  
Cross Sectional ◽  
Data Set ◽  
Initial Flow ◽  
Saint Venant Equations ◽  
Time Marching

Abstract. Initial conditions for flows and depths (cross-sectional areas) throughout a river network are required for any time-marching (unsteady) solution of the one-dimensional (1D) hydrodynamic Saint-Venant equations. For a river network modeled with several Strahler orders of tributaries, comprehensive and consistent synoptic data are typically lacking and synthetic starting conditions are needed. Because of underlying nonlinearity, poorly-defined or inconsistent initial conditions can lead to convergence problems and long spin-up times in an unsteady solver. Two new approaches are defined and demonstrated herein for computing flows and cross-sectional areas (or depths). These methods can produce an initial condition data set that is consistent with modeled landscape runoff and river geometry boundary conditions at the initial time. These new methods are: (1) the Pseudo-Time-Marching Method (PTM) that iterates toward a steady-state initial condition using an unsteady Saint-Venant solver, and (2) the Steady-Solution Method (SSM) that makes use of graph theory for initial flow rates and solution of a steady-state 1D momentum equation for the channel cross-sectional areas. The PTM is shown to be adequate for short river reaches, but is significantly slower and has occasional non-convergent behavior for large river networks. The SSM approach is shown to provide rapid solution of consistent initial conditions for both small and large networks, albeit with the requirement that additional code must be written rather than applying an existing unsteady Saint-Venant solver.

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