arXiv subjects

Yi-Long Luo

Publications and source records attributed to Yi-Long Luo.

At least 19 recordsLinked to original sources

arXiv2026

Compressible Navier-Stokes-Landau-Lifshitz-Gilbert system: derivations and well-posedness

In this paper, we first derive the compressible Navier-Stokes/Landau-Lifshitz-Gilbert (NS-LLG) model for magnetoelastic materials via the energetic variational approach (EnVarA). It is important to emphasize that the manner in which the evolution of magnetoelastic materials is influenced by the fluid motion--specifically through the deformation gradient--determines the kinematics of the magnetization and consequently leads to distinct governing equations. Subsequently, we establish the local-in-time existence of solutions to the compressible NS-LLG system under finite initial energy. Finally, near the constant equilibrium for magnetoelasticity in the absence of an external magnetic field, we reformulate the evolutionary model, which allows an additional dissipative term to be identified from the elastic stress. Based on this reformulation, we justify the global well-posedness of the evolutionary magnetoelasticity system with zero external magnetic field, provided the initial data are sufficiently small. In particular, when the magnetic field $M$ vanishes, this model reduces to the viscoelastic model. Our results significantly relax the previous initial data requirements, only assume the most basic structural condition $\rho_{0} \operatorname{det} F_{0} = 1$.

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arXiv2026

Global renormalized solutions for hard potential non-cutoff Boltzmann equation without defect measure

The existence of global renormalized solutions to the Boltzmann equation with long-range interactions without angular cutoff was first established by Alexandre and Villani [Comm. Pure Appl. Math., 55(1), 30-70, 2002]. Their result relies on a definition of renormalized solutions involving a non-negative defect measure. In this paper, we address this issue for the inverse power law model in the case of hard potentials ($0 \leq \gamma \leq 1$). By exploiting the stronger coercivity estimates provided by hard potentials, we prove that the defect measure actually vanishes. Consequently, we establish the global existence of renormalized solutions for the non-cutoff Boltzmann equation with hard potentials in the standard sense, without any defect measure. Finally, we construct a counterexample showing that the approach developed for the hard potential case fails for soft potential model ($-3 < \gamma < 0$).

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arXiv2026

Global renormalized solutions to Boltzmann systems modeling mixture gases of monatomic and polyatomic species

Inspired by DiPerna-Lions' work \cite{Diperna-Lions}, we study the renormalized solutions to the large-data Cauchy problem of the Boltzmann systems modeling mixture gases of monatomic and polyatomic species, in which the distribution functions $f_\alpha$ characterized the polyatomic species contain the continuous internal energy variable $I \in \mathbb{R}_+$. We first construct the smooth approximated problem and establish the corresponding uniform and physically natural bounds. Then, by employing the averaged velocity (-internal energy) lemma, we can show that the weak $L^1$ limit of the approximated solution is exactly a renormalized solution what we required. Moreover, we also justify that the constructed renormalized solution subjects to the entropy inequality.

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arXiv2025

The non-isothermal Maxwell-Stefan asymptotics of the multi-species Boltzmann equations

We study the convergence from the multi-species Boltzmann equations to the non-isothermal Maxwell-Stefan system. The global-in-time well-posedness of the Maxwell-Stefan system is first established. The solution is utilized as the fluid quantities to construct a local Maxwellian vector. The Maxwell-Stefan system can be derived from the multi-species Boltzmann equations under diffusive scaling by adding a relation on the total concentration. Different with the classical hydrodynamic limits of the Boltzmann equations, the Maxwellian based on the Maxwell-Stefan system is not a local equilibrium for the mixtures due to cross-interactions. A local coercivity property for the operator linearized around the local Maxwellian is established, based on the explicit spectral gap of the operator linearized around the global equilibrium. The global-in-time solution to the multi-species Boltzmann equations uniform in Knudsen number $\varepsilon$ is established in this scaling, thus the first non-isothermal Maxwell-Stefan asymptotics is rigorously justified. This generalizes Bondesan and Briant's work \cite{briant2021stability} from isothermal to non-isothermal case.

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arXiv2025

Knudsen boundary layer equations with incoming boundary condition: full range of cutoff collision kernels and Mach numbers of the far field

This paper establishes tahe existence and uniqueness of the nonlinear Knudsen layer equation with incoming boundary conditions. It is well-known that the solvability conditions of the problem vary with the Mach number of the far Maxwellian $\mathcal{M}^\infty$. We consider full ranges of cutoff collision kernels (i.e., $- 3 < \gamma \leq 1$) and all the Mach numbers of the far field in the $L^\infty_{x,v}$ framework. Additionally, the solution exhibits exponential decay $\exp \{- c x^\frac{2}{3 - \gamma} - c |v|^2 \}$ for some $c > 0$. To address the general angular cutoff collision kernel, we introduce a $(x,v)$-mixed weight $\sigma$. The proof is essentially bsed on adding an artificial damping term.

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arXiv2024

Knudsen boundary layer equations for full ranges of cutoff collision kernels: Maxwell reflection boundary with all accommodation coefficients in [0,1]

In this paper, we prove the existence and uniqueness of the Knudsen layer equation imposed on Maxwell reflection boundary condition with full ranges of cutoff collision kernels and accommodation coefficients (i.e., $- 3 < \gamma \leq 1$ and $0 \leq \alpha_* \leq 1$, respectively) in the $L^\infty_{x,v}$ framework. Moreover, the solution enjoys the exponential decay $\exp \{- c x^\frac{2}{3 - \gamma} - c |v|^2 \}$ for some $c > 0$. In order to study the general angular cutoff collision kernel $-3 < \gamma \leq 1$, we should introduce a $(x,v)$-mixed weight $\sigma$. The biggest difficulty in this paper is the nondissipative boundary condition, hence, the boundary temperature and velocity $(T_w, u_w)$ on $\{ x = 0 \}$ and $(T, \mathfrak{u})$ on $\{ x = + \infty \}$ do not guarantee the nonnegativity of the $L^2$ boundary energy. We also do not assume that $(T_w, u_w)$ and $(T, \mathfrak{u})$ are very closed to each other. We first derive the Nondissipative boundary lemma to pull the boundary energy to the interior weighted $L^2$ norms with higher power of $x$-polynomial weights. Then a so-called spatial-velocity indices iteration approach is developed to shift the higher power $x$-polynomial weights to $|v|$-polynomial weights. Finally, we construct an interleaved iteration process such that the boundary energy is successfully dominated.

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arXiv2023

Hydrodynamic limits from the self-organized kinetic system for body attitude coordination

The self-organized kinetic system for body attitude coordination (SOKB) was recently derived by Degond et al. (Math. Models Methods Appl. Sci. 27(6), 1005-1049, 2017). This system describe a new collective motion for multi-agents dynamics, where each agent is described by its position and body attitude: agents travel at a constant speed in a given direction and their body can rotate round it adopting different configurations (representing by rotation matrix in $\mathrm{SO(3)}$). In this paper, we study the hydrodynamic limit of the scaled SOKB system with the constant intensity of coordination by employing the Generalized Collision Invariants (GCI)-based Hilbert expansion approach. The limit is the self-organized hydrodynamic model for body attitude coordination (SOHB). In spherical coordinates, the SOHB system is singular. To avoid this coordinate singularity, we transfer SOHB system into a non-singular form by stereographic projection. This work provides the first analytically rigorous justification of the modeling and asymptotic analysis in Degond et al. (Math. Models Methods Appl. Sci. 27(6), 1005-1049, 2017).

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arXiv2023

Incompressible limit of the Ericksen-Leslie hyperbolic liquid crystal model in compressible flow

Ericksen and Leslie proposed a hydrodynamic model for liquid crystals in the format of conservation laws in the 1960s. Their original model includes inertial and compressibility effects, which makes the model a coupled parabolic-hyperbolic system. In this paper we build up the connection between the compressible and incompressible parabolic-hyperbolic liquid crystal model in the framework of classical solutions. We first derive the scaled Ericksen-Leslie system with dimensionless numbers, including Mach, Reynolds, and Ericksen numbers. In particular, we introduce the so-called inertial constant $χ$ which characterizes the inertial effect of the liquid crystal molecular. Next, we establish the energy estimates uniform in the Mach number $ε$ for both the compressible system and its time-derivative system with small data. Then, we pass to the limit $ε\rightarrow 0$ in the compressible system, so that we establish the global classical solution of the incompressible system by the compactness arguments. Moreover, we also obtain the convergence rates associated with $L^2$-norm in the case of well-prepared initial data. This is the first result on the incompressible limit of the compressible parabolic-hyperbolic liquid crystal model and confirms the relations of different parabolic-hyperbolic liquid crystal model rigorously.

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arXiv2023

Pattern formation of a pathway-based diffusion model: linear stability analysis and an asymptotic preserving method

We investigate the linear stability analysis of a pathway-based diffusion model (PBDM), which characterizes the dynamics of the engineered Escherichia coli populations [X. Xue and C. Xue and M. Tang, P LoS Computational Biology, 14 (2018), pp. e1006178]. This stability analysis considers small perturbations of the density and chemical concentration around two non-trivial steady states, and the linearized equations are transformed into a generalized eigenvalue problem. By formal analysis, when the internal variable responds to the outside signal fast enough, the PBDM converges to an anisotropic diffusion model, for which the probability density distribution in the internal variable becomes a delta function. We introduce an asymptotic preserving (AP) scheme for the PBDM that converges to a stable limit scheme consistent with the anisotropic diffusion model. Further numerical simulations demonstrate the theoretical results of linear stability analysis, i.e., the pattern formation, and the convergence of the AP scheme.

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arXiv2023

On the initial-boundary value problem of two-phase incompressible flows with variable density in smooth bounded domain

In this work, we study the so-called Allen-Cahn-Navier-Stokes equations, a diffuse-interface model for two-phase incompressible flows with different densities. We first prove the local-in-time existence and uniqueness of classical solutions with finite initial energy over the smooth bounded domain $Ω$. The key point is to transform the boundary values of the higher order spatial derivatives to that of the higher order time derivatives by employing the well-known Agmon-Douglis-Nireberg theory in [6]. We then prove global existence near the equilibrium $(0, \pm 1)$ and justify the time exponetial decay $e^{- c_\# t}$ of the global solution. The majority is that the derivative $f'(ϕ)$ of the physical relevant energy density $f(ϕ)$ will generate an additional damping effect under the perturbation $ϕ= φ\pm 1$.

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arXiv2023

From Kinetic Flocking Model of Cucker-Smale Type to Self-Organized Hydrodynamic model

We investigate the hydrodynamic limit problem for a kinetic flocking model. We develop a GCI-based Hilbert expansion method, and establish rigorously the asymptotic regime from the kinetic Cucker-Smale model with a confining potential in a mesoscopic scale to the macroscopic limit system for self-propelled individuals, which is derived formally by Aceves-S\'anchez, Bostan, Carrillo and Degond (2019). In the traditional kinetic equation with collisions, for example, Boltzmann type equations, the key properties that connect the kinetic and fluid regimes are: the linearized collision operator (linearized collision operator around the equilibrium), denoted by $\mathcal{L}$, is symmetric, and has a nontrivial null space (its elements are called collision invariants) which include all the fluid information, i.e. the dimension of Ker($\mathcal{L}$) is equal to the number of fluid variables. Furthermore, the moments of the collision invariants with the kinetic equations give the macroscopic equations. The new feature and difficulty of the corresponding problem considered in this paper is: the linearized operator $\mathcal{L}$ is not symmetric, i.e. $\mathcal{L}\neq \mathcal{L}^*$, where $\mathcal{L}^*$ is the dual of $\mathcal{L}$. Moreover, the collision invariants lies in Ker($\mathcal{L}^*$), which is called generalized collision invariants (GCI). This is fundamentally different with classical Boltzmann type equations. This is a common feature of many collective motions of self-propelled particles with alignment in living systems, or many active particle system. Another difficulty (also common for active system) is involved by the normalization of the direction vector, which is highly nonlinear.

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arXiv2022

Grad-Caflisch pointwise decay estimates revisited

In the influential paper \cite{Caflish-1980-CPAM} which was the starting point of the employment of Hilbert expansion method to the rigorous justifications of the fluid limits of the Boltzmann equation, Caflisch discovered an elegant and crucial estimate on each expansion term (Proposition 3.1 in \cite{Caflish-1980-CPAM}). The proof essentially relied on an estimate of Grad \cite{Grad-1963}, which was on the pointwise decay properties of $\mathcal{L}^{-1}$, the pseudo-inverse operator of the linearized Boltzmann collision operator $\mathcal{L}$, for the hard potential collision kernel, i.e. the power $0\leq \gamma\leq 1$. Caflisch's arguments need the exponential version of Grad's estimate. However, Grad's original paper was only on the polynomial decay. In this paper, we revisit and provide a full proof of the Caflisch-Grad type decay estimates and the corresponding applications in the compressible Euler limit of the Boltzmann equaiton. The main novelty is that for the case collision kernel power $-\frac{3}{2}<\gamma\leq 1$, the proof of the pointwise estimate does not use any derivatives. So the potential applications of this estimate could be wider than in the Hilbert expansion. For the completeness of the result, we also prove the almost everywhere pointwise estimate using derivatives for the case $-3<\gamma\leq -\frac{3}{2}$. Furthermore, in the application to fluid limits, $\mathcal{L}^{-1}$ and the derivatives with respect to the parameters (for example, $(t,x)$, this must happen when $\mathcal{L}$ is linearized around local Maxwellian which depends on $(t,x)$) are not commutative. We detailed analyze the estimate of commutators, which was missing in previous literatures of fluid limits of the Boltzmann equation. This estimate is needed in all compressible fluid limits from Boltzmann equation.

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arXiv2022

Hydrodynamic limit of the incompressible Navier-Stokes-Fourier-Maxwell System with Ohm's Law from the Vlasov-Maxwell-Boltzmann system: Hilbert expansion approach

We prove a global-in-time limit from the two-species Vlasov-Maxwell-Boltzmann system to the two-fluid incompressible Navier-Stokes-Fourier-Maxwell system with Ohm's law. Besides the techniques developed for the classical solutions to the Vlasov-Maxwell-Boltzmann equations in the past years, such as the nonlinear energy method and micro-macro decomposition are employed, key roles are played by the decay properties of both the electric field and the wave equation with linear damping of the divergence free magnetic field. This is a companion paper of [N. Jiang and Y.-L. Luo, \emph{Ann. PDE} 8 (2022), no. 1, Paper No. 4, 126 pp] in which Hilbert expansion is not employed.

math.AP↗

arXiv2021

On kinetic and macroscopic models for the stripe formation in engineered bacterial populations

We study the well-posedness of the biological models with AHL-dependent cell mobility on engineered Escherichia coli populations. For the kinetic model proposed by Xue-Xue-Tang recently, the local existence for large initial data is proved first. Furthermore, the positivity and local conservation laws for density $ρ(t,x,z)$ and nutrient $n(t,x)$ with initial assumptions are justified. Based on these properties, it can be extended globally in time near the equilibrium $(0,0,0)$. Considering the asymptotic behaviors of faster response CheZ turnover rate (i.e.,$\varepsilon\rightarrow 0$), one formally derives an anisotropic diffusion engineered Escherichia coli populations model (in short, AD-EECP) for which we find a key extra a priori estimate to overcome the difficulties coming from the nonlinearity of the diffusion structure. The local well-posedness and the positivity and local conservation laws for density and nutrient of the AD-EECP are justified. Furthermore, the global existence around the steady state $(\varrho_a, h_a, 0)$ with $\varrho_a \in [0, Λ_b)$ is obtained.

math.AP↗

arXiv2021

Compressible Euler limit from Boltzmann equation with Maxwell reflection boundary condition in half-space

Starting from the local-in-time classical solution to the compressible Euler system with impermeable boundary condition in half-space, by employing the coupled weak viscous layers (governed by linearized compressible Prandtl equations with Robin boundary condition) and linear kinetic boundary layers, and the analytical tools in \cite{Guo-Jang-Jiang-2010-CPAM} and some new boundary estimates both for Prandtl and Knudsen layers, we proved the local-in-time existence of Hilbert expansion type classical solutions to the scaled Boltzmann equation with Maxwell reflection boundary condition with accommodation coefficient $α_\varepsilon=O(\sqrt{\varepsilon})$ when the Knudsen number $\varepsilon$ small enough. As a consequence, this justifies the corresponding case of formal analysis in Sone's books \cite{Sone-2002book, Sone-2007-Book}. This also extends the results in \cite{GHW-2020} from specular to Maxwell reflection boundary condition. Both of this paper and \cite{GHW-2020} can be viewed as generalizations of Caflisch's classic work \cite{Caflish-1980-CPAM} to the cases with boundary.

math.AP↗

arXiv2021

Compressible Euler limit from Boltzmann equation with complete diffusive boundary condition in half-space

In this paper, we prove the compressible Euler limit from the Boltzmann equation with hard sphere collisional kernel and complete diffusive boundary condition in half-space by employing the Hilbert expansion which includes interior and Knudsen layers. This rigorously justifies the corresponding formal analysis in Sone's book \cite{Sone-2007-Book} in the context of short time smooth solutions, and also generalizes the classic Caflisch's result \cite{Caflish-1980-CPAM} to initial-boundary problem case.

math.AP↗

arXiv2021

Stability of equilibria to the model for non-isothermal electrokinetics

Recently, energetic variational approach was employed to derive models for non-isothermal electrokinetics by Liu et. al \cite{Liu-Wu-Liu-CMS2018}. In particular, the Poisson-Nernst-Planck-Fourier (PNPF) system for the dynamics of $N$-ionic species in a solvent was derived. In this paper we first reformulate PNPF ($4N+6$ equations) into an evolutional system with $N+1$ equations, and define a new total electrical charge. We then prove the constant states are stable provided that they are such that the perturbed systems around them are dissipative. However, not all positive constant solutions of PNPF are such that the corresponding perturbed systems are dissipative. We characterize a set of equilibria $\mathcal{S}_{eq}$ whose elements satisfy the conditions {(A1)} and {(A2)}, and prove it is nonempty. After then, we prove the stability of these equilibria, thus the global well-posedness of PNPF near them.

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arXiv2020

Entropy inequality and energy dissipation of inertial Qian-Sheng model for nematic liquid crystals

For the inertial Qian-Sheng model of nematic liquid crystals in the $Q$-tensor framework, we illustrate the roles played by the entropy inequality and energy dissipation in the well-posedness of smooth solutions when we employ energy method. We first derive the coefficients requirements from the entropy inequality, and point out the entropy inequality is insufficient to guarantee energy dissipation. We then introduce a novel Condition (H) which ensures the energy dissipation. We prove that when both the entropy inequality and Condition (H) are obeyed, the local in time smooth solutions exist for large initial data. Otherwise, we can only obtain small data local solutions. Furthermore, to extend the solutions globally in time and obtain the decay of solutions, we require at least one of the two conditions: entropy inequality, or $\tildeμ_2= μ_2$, which significantly enlarge the range of the coefficients in previous works.

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