Regular Initial Condition Research Articles

On the Energy Cascade of 3-Wave Kinetic Equations: Beyond Kolmogorov–Zakharov Solutions

In weak turbulence theory, the Kolmogorov-Zakharov spectra is a class of time-independent solutions to the kinetic wave equations. In this paper, we construct a new class of time-dependent isotropic solutions to the decaying turbulence problems (whose solutions are energy conserved), with general initial conditions. These solutions exhibit the interesting property that the energy is cascaded from small wavenumbers to large wavenumbers. We can prove that starting with a regular initial condition whose energy at the infinity wave number $|p|=\infty$ is $0$, as time evolves, the energy is gradually accumulated at $\{|p|=\infty\}$. Finally, all the energy of the system is concentrated at $\{|p|=\infty\}$ and the energy function becomes a Dirac function at infinity $E\delta_{\{|p|=\infty\}}$, where $E$ is the total energy. The existence of this class of solutions is, in some sense, {the first complete rigorous} mathematical proof based on the kinetic description for the energy cascade phenomenon for waves with quadratic nonlinearities. We only represent in this paper the analysis of the statistical description of acoustic waves (and equivalently capillary waves). However, our analysis works for other cases as well.

Stationary bubbles and their tunneling channels toward trivial geometry

In the path integral approach, one has to sum over all histories that start from the same initial condition in order to obtain the final condition as a superposition of histories. Applying this into black hole dynamics, we consider stable and unstable stationary bubbles as a reasonable and regular initial condition. We find examples where the bubble can either form a black hole or tunnel toward a trivial geometry, i.e., with no singularity nor event horizon. We investigate the dynamics and tunneling channels of true vacuum bubbles for various tensions. In particular, in line with the idea of superposition of geometries, we build a classically stable stationary thin-shell solution in a Minkowski background where its fate is probabilistically given by non-perturbative effects. Since there exists a tunneling channel toward a trivial geometry in the entire path integral, the entire information is encoded in the wave function. This demonstrates that the unitarity is preserved and there is no loss of information when viewed from the entire wave function of the universe, whereas a semi-classical observer, who can see only a definitive geometry, would find an effective loss of information. This may provide a resolution to the information loss dilemma.

Effects of Initial Symmetry on the Global Symmetry of One-Dimensional Legal Cellular Automata

To examine the development of pattern formation from the viewpoint of symmetry, we applied a two-dimensional discrete Walsh analysis to a one-dimensional cellular automata model under two types of regular initial conditions. The amount of symmetropy of cellular automata (CA) models under regular and random initial conditions corresponds to three Wolfram’s classes of CAs, identified as Classes II, III, and IV. Regular initial conditions occur in two groups. One group that makes a broken, regular pattern formation has four types of symmetry, whereas the other group that makes a higher hierarchy pattern formation has only two types. Additionally, both final pattern formations show an increased amount of symmetropy as time passes. Moreover, the final pattern formations are affected by iterations of base rules of CA models of chaos dynamical systems. The growth design formations limit possibilities: the ratio of developing final pattern formations under a regular initial condition decreases in the order of Classes III, II, and IV. This might be related to the difference in degree in reference to surrounding conditions. These findings suggest that calculations of symmetries of the structures of one-dimensional cellular automata models are useful for revealing rules of pattern generation for animal bodies.

Some controllability results for linearized compressible navier−stokes system

In this article, we study the null controllability of linearized compressible Navier-Stokes system in one and two dimension. We first study the one-dimensional compressible Navier-Stokes system for non-barotropic fluid linearized around a constant steady state. We prove that the linearized system around $(\bar \rho,0,\bar \theta)$, with $\bar \rho > 0,$ $ \bar \theta > 0$ is not null controllable by localized interior control or by boundary control. But the system is null controllable by interior controls acting everywhere in the velocity and temperature equation for regular initial condition. We also prove that the the one-dimensional compressible Navier-Stokes system for non-barotropic fluid linearized around a constant steady state $(\bar \rho,\bar v ,\bar \theta)$, with $\bar \rho > 0,$ $\bar v > 0,$ $\bar \theta > 0$ is not null controllable by localized interior control or by boundary control for small time $T.$ Next we consider two-dimensional compressible Navier-Stokes system for barotropic fluid linearized around a constant steady state $(\bar \rho, {\bf 0}).$ We prove that this system is also not null controllable by localized interior control.

Existence of globally attracting fixed points of viscous Burgers equation with constant forcing. A computer assisted proof

We present a computer assisted method for proving the existence of globally attracting fixed points of dissipative PDEs. An application to the viscous Burgers equation with periodic boundary conditions and a forcing function constant in time is presented as a case study. We establish the existence of a locally attracting fixed point by using rigorous numerics techniques. To prove that the fixed point is, in fact, globally attracting we introduce a technique relying on a construction of an absorbing set, capturing any sufficiently regular initial condition after a finite time. Then the absorbing set is rigorously integrated forward in time to verify that any sufficiently regular initial condition is in the basin of attraction of the fixed point.

Dependence of entanglement dynamics on the global classical dynamical regime

We analyze the connections between the dynamical generation of continuous variable entanglement and the underlying classical trajectories in pairs of coupled oscillators. In the quantization of a periodic cycle, we find periodic entanglement which has twice the frequency of the corresponding classical motion. Such frequency doubling continues to hold true in the entanglement dynamics for a second model that exhibits a two-frequency orbit in the classical domain. In addition, the periodicity and the quasiperiodicity of the entanglement are found to be independent of the local classical dynamical behavior. Finally, in our third model, the entanglement production rate is found to be (i) higher in the chaotic regime and (ii) insensitive toward the choice of regular or chaotic initial condition in the mixed regime. In summary, we have illustrated through our sample models that the generation of dynamical pattern of entanglement can depend completely on the global classical dynamical regime without being influenced by the local classical behavior.

REGULARITY OF SOLUTIONS TO LINEAR STOCHASTIC SCHRÖDINGER EQUATIONS

We develop linear stochastic Schrödinger equations driven by standard cylindrical Brownian motions (LSSs) that unravel quantum master equations in Lindblad form into quantum trajectories. More precisely, this paper establishes the existence and uniqueness of the smooth strong solution Xt to a LSS with regular initial condition. Moreover, we obtain that the mean value of the square norm of Xt is constant. We also treat the approximation of LSSs by ordinary stochastic differential equations. We apply our results to: (i) models of quantum measurements of position and momentum; and (ii) a system formed by fermions.

Prohibition of large inhomogeneity in the preinflationary stage.

We examine the spherically symmetric and asymptotically spatially flat inhomogenous initial data of an inflaton field to see its effect on the evolution of space-time. We search for the apparent horizon in those initial data and show the relation of the scale of inhomogeneity and the amplitude of the inflaton field to the formation of a horizon. We find that for a certain range of Hubble constant there is no regular initial condition but the bag of gold singularity appears if the inhomogeneity of the inflaton field is large enough ($\ensuremath{\delta}\ensuremath{\varphi}\ensuremath{\gtrsim}{m}_{\mathrm{Pl}}$).