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Nikolaos Roidos

Publications and source records attributed to Nikolaos Roidos.

At least 19 recordsLinked to original sources
arXiv2026

Strip-type operators and abstract Cauchy problems

We consider the non-homogeneous abstract linear Schrödinger and wave equations with zero initial conditions, defined by operators of strip-type and parabola-type in Banach spaces, respectively, and establish the well-posedness of classical solutions in appropriate vector-valued Sobolev-Slobodetskii spaces. We obtain analogous results for two extensions of these equations by replacing the previously mentioned boundedness properties of the associated operators with $R$-boundedness. As an application, we consider an abstract semilinear wave equation and establish the existence and uniqueness of classical solutions to this problem for short times.

math.FA↗
arXiv2026

Maximal $L^{q}$-regularity for the Laplacian on manifolds with edges

We introduce an $R$-sectoriality perturbation technique for non-commuting operators defined in Bochner spaces. Based on this and on bounded $H^{\infty}$-functional calculus results for the Laplacian on manifolds with conical singularities, we show maximal $L^{q}$-regularity for the Laplacian on manifolds with edge type singularities in appropriate weighted Sobolev spaces. As an application, we consider the porous medium equation on manifolds with edges and show short time existence, uniqueness and maximal regularity for the solution. We also provide space asymptotics near the singularities in terms of the local geometry.

math.AP↗
arXiv2024

The spectrum of the Laplacian on closed manifolds and the heat asymptotics near conical points

Let $\mathcal{M}$ be a smooth, closed and connected manifold of dimension $n\in\mathbb{N}$, endowed with a Riemannian metric $g$. Moreover, let $\mathcal{B}$ be an $(n+1)$-dimensional compact manifold with boundary equal to $\mathcal{M}$. Endow $\mathcal{B}$ with a Riemannian metric $h$ such that, in local coordinates $(x,y)\in [0,1)\times \mathcal{M}$ on the collar part of the boundary, it admits the warped product form $h=dx^{2}+x^{2}g(y)$. We consider the homogeneous heat equation on $(\mathcal{B},h)$ and find an arbitrary long asymptotic expansion of the solutions with respect to $x$ near $0$. It turns out that the spectrum of the Laplacian on $(\mathcal{M},g)$ determines explicitly the above asymptotic expansion and vice versa.

math.AP↗
arXiv2024

Curve shortening flow on Riemann surfaces with conical singularities

We study the curve shortening flow on Riemann surfaces with finitely many conformal conical singularities. If the initial curve is passing through the singular points, then the evolution is governed by a degenerate quasilinear parabolic equation. In this case, we establish short time existence, uniqueness, and regularity of the flow. We also show that the evolving curves stay fixed at the singular points of the surface and obtain some collapsing and convergence results.

math.DG↗
arXiv2023

Existence of global attractors and convergence of solutions for the Cahn-Hilliard equation on manifolds with conical singularities

We consider the Cahn-Hilliard equation on manifolds with conical singularities and prove existence of global attractors in higher order Mellin-Sobolev spaces with asymptotics. We also show convergence of solutions in the same spaces to an equilibrium point and provide asymptotic behavior of the equilibrium near the conical tips in terms of the local geometry.

math.AP↗
arXiv2022

The fractional porous medium equation on manifolds with conical singularities II

This is the second of a series of two papers which studies the fractional porous medium equation, $\partial_t u +(-Δ)^σ(|u|^{m-1}u )=0 $ with $m>0$ and $σ\in (0,1]$, posed on a Riemannian manifold with isolated conical singularities. The first aim of the article is to derive some useful properties for the Mellin-Sobolev spaces including the Rellich-Kondrachov Theorem and Sobolev-Poincaré, Nash and Super Poincaré type inequalities. The second part of the article is devoted to the study the Markovian extensions of the conical Laplacian operator and its fractional powers. Then based on the obtained results, we establish existence and uniqueness of a global strong solution for $L_\infty-$initial data and all $m>0$. We further investigate a number of properties of the solutions, including comparison principle, $L_p-$contraction and conservation of mass. Our approach is quite general and thus is applicable to a variety of similar problems on manifolds with more general singularities.

math.AP↗
arXiv2022

The fractional porous medium equation on manifolds with conical singularities I

This is the first of a series of two papers which studies the fractional porous medium equation on a Riemannian manifold with isolated conical singularities. In this article, we show $R$-sectoriality for the fractional powers of possibly non-invertible $R$-sectorial operators. Applications concern existence, uniqueness and maximal $L^{q}$-regularity results for solutions of the fractional porous medium equation on manifolds with conical singularities. Space asymptotic behavior of the solutions close to the singularities is provided and its relation to the local geometry is established. Our method extends the freezing-of-coefficients method to the case of non-local operators that are expressed as linear combinations of terms in the form of a product of a function and a fractional power of a local operator.

math.AP↗
arXiv2022

Smoothness and long time existence for solutions of the Cahn-Hilliard equation on manifolds with conical singularities

We consider the Cahn-Hilliard equation on manifolds with conical singularities. For appropriate initial data, we show that the solution exists in the maximal $L^q$-regularity space for all times and becomes instantaneously smooth in space and time, where the maximal $L^q$-regularity is obtained in the sense of Mellin-Sobolev spaces. Moreover, we provide precise information concerning the asymptotic behavior of the solution close to the conical tips in terms of the local geometry.

math.AP↗
arXiv2021

Functional Inequalities involving Nonlocal Operators on Complete Riemannian Manifolds and Their Applications to The Fractional Porous Medium Equation

The objective of this paper is twofold. First, we conduct a careful study of various functional inequalities involving the fractional Laplacian operators, including nonlocal Sobolev-Poincaré, Nash, Super Poincaré and logarithmic Sobolev type inequalities, on complete Riemannian manifolds satisfying some mild geometric assumptions. Second, based on the derived nonlocal functional inequalities, we analyze the asymptotic behavior of the solution to the fractional porous medium equation, $\partial_t u +(-Δ)^σ(|u|^{m-1}u )=0 $ with $m>0$ and $σ\in (0,1)$. In addition, we establish the global well-posedness of the equation on an arbitrary complete Riemannian manifold.

math.AP↗
arXiv2021

Expanding solutions of quasilinear parabolic equations

By using the theory of maximal $L^{q}$-regularity and methods of singular analysis, we show a Taylor's type expansion--with respect to the geodesic distance around an arbitrary point--for solutions of quasilinear parabolic equations on closed manifolds. The powers of the expansion are determined explicitly by the local geometry, whose reflection to the solutions is established through the local space asymptotics.

math.AP↗
arXiv2019

Existence and maximal $L^{p}$-regularity of solutions for the porous medium equation on manifolds with conical singularities

We consider the porous medium equation on manifolds with conical singularities and show existence, uniqueness and maximal $L^{p}$-regularity of a short time solution. In particular, we obtain information on the short time asymptotics of the solution near the conical point. Our method is based on bounded imaginary powers results for cone differential operators on Mellin-Sobolev spaces and $R$-sectoriality perturbation techniques.

math.AP↗
arXiv2019

The Swift-Hohenberg equation on conic manifolds

We consider the Swift-Hohenberg equation on manifolds with conical singularities and show existence, uniqueness and maximal regularity of the short time solution in terms of Mellin-Sobolev spaces. Moreover, we give a necessary and sufficient condition so that the above solution exists for all times. Space asymptotic expansion of the solution near the singularity is also provided and its relation to the local geometry is shown. The same problem is considered on closed manifolds and similar results are obtained by using the above singular analysis theory.

math.AP↗
arXiv2019

Conic manifolds under the Yamabe flow

We consider the unnormalized Yamabe flow on manifolds with conical singularities. Under certain geometric assumption on the initial cross-section we show well posedness of the short time solution in the $L^q$-setting. Moreover, we give a picture of the deformation of the conical tips under the flow by providing an asymptotic expansion of the evolving metric close to the boundary in terms of the initial local geometry. Due to the blow up of the scalar curvature close to the singularities we use maximal $L^q$-regularity theory for conically degenerate operators.

math.AP↗
arXiv2019

Smoothness and long time existence for solutions of the porous medium equation on manifolds with conical singularities

We study the porous medium equation on manifolds with conical singularities. Given strictly positive initial values, we show that the solution exists in the maximal $L^{q}$-regularity space for all times and is instantaneously smooth in space and time, where the maximal $L^{q}$-regularity is obtained in the sense of Mellin-Sobolev spaces. Moreover, we obtain precise information concerning the asymptotic behavior of the solution close to the singularity. Finally, we show the existence of generalized solutions for non-negative initial data.

math.AP↗