### Abstract

We consider the degenerate Keller-Segel system (KS)_{m} with 1 < m ≤ 2-2/N of Nagai type below. Our aim is to find the two types of conditions on the initial data which divide the situation of the solution (u, v) into the global existence and the finite time blow-up; one is the assumption on the size of the other one is the assumption on the size of ∂ u_{0}
^{N(2-m)/2} dx. Moreover, we discuss the critical case of m = 2-2/N (N ≥ 3). We find the upper bound and the lower bound on the size of the L^{1}(= L ^{N(2-m)/2} )-norm of the initial data which assures the global existence and the finite time blowup, respectively. Our results cover the well-known threshold number 8π/αχ in R^{2} for the semi-linear case, since both bounds correspond to 8π/αχ by substituting m = 1 and N = 2 formally. For our main results, we also give a proof of the mass conservation law in ℝ^{N} to (KS)_{m}.

Original language | English |
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Pages (from-to) | 121-144 |

Number of pages | 24 |

Journal | Advances in Differential Equations |

Volume | 12 |

Issue number | 2 |

Publication status | Published - Dec 1 2007 |

### All Science Journal Classification (ASJC) codes

- Analysis
- Applied Mathematics

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## Cite this

*Advances in Differential Equations*,

*12*(2), 121-144.