Source: Rev. Mat. Iberoamericana Volume 26, Number 3
(2010), 891-913.
We consider the Keller-Segel system of degenerate type (KS)$_m$ with $m > 1$
below. We establish a uniform estimate of $\partial_x^2 u^{m-1}$ from below.
The corresponding estimate to the porous medium equation is well-known
as an Aronson-Bénilan type. We apply our estimate to prove
the optimal Hölder continuity of weak solutions of (KS)$_m$.
In addition, we find that the set $D(t):=\{ x \in \mathbb{R}; u(x,t) > 0\}$
of positive region to the solution $u$ is monotonically non-decreasing with respect to $t$.
References
Aronson, D.G.: The porous medium equation. In Nonlinear diffusion problems (Montecatini Terme, 1985), 1-46. Lecture Notes in Math. 1224. Springer, Berlin, 1986.
Mathematical Reviews (MathSciNet):
MR877986
Aronson, D.G.: Regularity properties of flows through porous media: A counterexample. SIAM J. Appl. Math. 19 (1970), 299-307.
Mathematical Reviews (MathSciNet):
MR265774
Aronson, D.G.: Regularity properties of flows through porous media: The interface. Arch. Rational Mech. Anal. 37 (1970), 1-10.
Mathematical Reviews (MathSciNet):
MR255996
Aronson, D.G. and Bénilan, P.: Régularité des solutions de l'équation des milieux poreux dans $\mathbbR^N$. C. R. Acad. Sci. Paris Sér. A-B 288 (1979), A103-A105.
Aronson, D.G. and Caffarelli, L.A.: Optimal regularity for one dimensional porous medium flow. Rev. Mat. Iberoamericana 2 (1986), no. 4, 357-366.
Mathematical Reviews (MathSciNet):
MR913692
Bénilan, Ph.: A strong regularity $L^p$ for solutions of the porous media equation. In Contributions to nonlinear partial differential equations (Madrid, 1981), 39-58. Res. Notes in Math. 89. Pitman, Boston, MA, 1983.
Mathematical Reviews (MathSciNet):
MR730795
Caffarelli, L.A. and Friedman, A.: Continuity of the density of a gas flow in a porous medium. Trans. Amer. Math. Soc. 252 (1979), 99-113.
Mathematical Reviews (MathSciNet):
MR534112
Childress, S. and Percus, J.K.: Nonlinear aspects of chemotaxis. Math. Biosci. 56 (1981), 217-237.
Mathematical Reviews (MathSciNet):
MR632161
Dahlberg, B.E.J. and Kenig, C.E.: Nonnegative solutions of the porous medium equations. Comm. Partial Differential Equations 9 (1984), 409-437.
Mathematical Reviews (MathSciNet):
MR741215
DiBenedetto, E.: Regularity results for the porous medium equation. Ann. Mat. Pura Appl. (4) 121 (1979), 249-262.
Mathematical Reviews (MathSciNet):
MR554779
DiBenedetto, E. and Friedman, A.: Hölder estimates for nonlinear degenerate parabolic systems. J. Reine Angew. Math. 357 (1985), 1-22.
Mathematical Reviews (MathSciNet):
MR783531
Friedman, A.: Partial differential equations of parabolic type. Prentice-Hall, Englewood Cliffs, NJ, 1964.
Mathematical Reviews (MathSciNet):
MR181836
Gilding, B.H.: Hölder continuity of solutions of parabolic equations. J. London Math. Soc. (2) 13 (1976), 103-106.
Mathematical Reviews (MathSciNet):
MR399658
Gilding, B.H. and Peletier, L.A.: On a class of similarity solutions of the porous medium equation. J. Math. Anal. Appl. 55 (1976), 351-364; J. Math. Anal. Appl. 57 (1977), 522-538.
Keller, E.F. and Segel, L.A.: Initiation of slime mold aggregation viewed as an instability. J. Theor. Biol. 26, (1970), 399-415.
Knerr, B.: The porous medium equation in one dimension. Trans. Amer. Math. Soc. 234 (1977), no. 2, 381-415.
Mathematical Reviews (MathSciNet):
MR492856
Kruzhkov, S.N.: Results on the character of the regularity of solutions of parabolic equations and some of their applications. Math. Notes 6 (1969), 517-523.
Lieberman, G.L.: Second order parabolic differential equations. World Scientific Publishing, River Edge, NJ, 1996.
Luckhaus, S. and Sugiyama, Y.: Asymptotic profile with the optimal convergence rate for a parabolic equation of chemotaxis in super-critical cases. Indiana Univ. Math. J. 56 (2007), 1279-1297.
Sugiyama, Y.: Time global existence and asymptotic behavior of solutions to degenerate quasi-linear parabolic systems of chemotaxis. Differential Integral Equations 20 (2007), 133-180.
Sugiyama, Y.: Application of the best constant of the Sobolev inequality to degenerate Keller-Segel models. Adv. Differential Equations 12 (2007), 121-144.
Sugiyama, Y. and Kunii, H.: Global existence and decay properties for a degenerate Keller-Segel model with a power factor in drift term. J. Differential Equations 227 (2006), 333-364.
Sugiyama, Y.: Finite speed of propagation in 1-D degenerate Keller-Segel system. To appear in Math. Nachr.
Sugiyama, Y.: Interfaces for 1-D degenerate Keller-Segel systems. J. Evol. Equ. 9 (2009), no. 1, 123-142.
Sugiyama, Y. and Velázquez, J.J.L.: Self-similar aggregation with different masses for the Keller-Segel system with porous medium diffusion. Submitted.
Vázquez, J.L.: The porous medium equation. Mathematical Theory. Oxford Mathematical Monographs. The Clarendon Press, Oxford University Press, Oxford, 2007.