### Abstract

Original language | English |
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Pages (from-to) | 70-93 |

Number of pages | 24 |

Journal | SIAM Journal on Control and Optimization |

Volume | 55 |

Issue number | 1 |

DOIs | |

Publication status | Published - 2017 |

Externally published | Yes |

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*SIAM Journal on Control and Optimization*, vol. 55, no. 1, pp. 70-93. https://doi.org/10.1137/16m105575x

**A new type of identification problems: Optimizing the fractional order in a nonlocal evolution equation.** / Sprekels, J.; Valdinoci, E.

Research output: Contribution to journal › Article

TY - JOUR

T1 - A new type of identification problems: Optimizing the fractional order in a nonlocal evolution equation

AU - Sprekels, J.

AU - Valdinoci, E.

PY - 2017

Y1 - 2017

N2 - In this paper, we consider a rather general linear evolution equation of fractional type, namely, a diffusion type problem in which the diffusion operator is the sth power of a positive definite operator having a discrete spectrum in R+. We prove existence, uniqueness, and differentiability properties with respect to the fractional parameter s. These results are then employed to derive existence as well as first-order necessary and second-order suffcient optimality conditions for a minimization problem, which is inspired by considerations in mathematical biology. In this problem, the fractional parameter s serves as the \control parameter" that needs to be chosen in such a way as to minimize a given cost functional. This problem constitutes a new class of identiffcation problems: while usually in identification problems the type of the differential operator is prescribed and one or several of its coeffcient functions need to be identified, in the present case one has to determine the type of the differential operator itself. This problem exhibits the inherent analytical diffculty that with changing fractional parameter s also the domain of deffnition, and thus the underlying function space, of the fractional operator changes.

AB - In this paper, we consider a rather general linear evolution equation of fractional type, namely, a diffusion type problem in which the diffusion operator is the sth power of a positive definite operator having a discrete spectrum in R+. We prove existence, uniqueness, and differentiability properties with respect to the fractional parameter s. These results are then employed to derive existence as well as first-order necessary and second-order suffcient optimality conditions for a minimization problem, which is inspired by considerations in mathematical biology. In this problem, the fractional parameter s serves as the \control parameter" that needs to be chosen in such a way as to minimize a given cost functional. This problem constitutes a new class of identiffcation problems: while usually in identification problems the type of the differential operator is prescribed and one or several of its coeffcient functions need to be identified, in the present case one has to determine the type of the differential operator itself. This problem exhibits the inherent analytical diffculty that with changing fractional parameter s also the domain of deffnition, and thus the underlying function space, of the fractional operator changes.

UR - https://www.scopus.com/inward/record.uri?eid=2-s2.0-85014343183&doi=10.1137%2f16M105575X&partnerID=40&md5=c3b58625c8911d0f6c38b47d13ff6db2

U2 - 10.1137/16m105575x

DO - 10.1137/16m105575x

M3 - Article

VL - 55

SP - 70

EP - 93

JO - SIAM Journal on Control and Optimization

JF - SIAM Journal on Control and Optimization

SN - 0363-0129

IS - 1

ER -