The optimal boundary control of Navier–Stokes flow is formulated as a constrained optimization problem and a sequential quadratic programming (SQP) approach is studied for its solution. Since SQP methods treat states and controls as independent variables and do not insist on satisfying the constraints during the iterations, care must be taken to avoid a possible incompatibility of Dirichlet bou...

Let S be the left R-bialgebroid of a depth two extension with cen-tralizer R. We show that the left endomorphism ring of depth two extension, not necessarily balanced, is a left S-Galois extension of A op. Looking to examples of depth two, we establish that a Hopf subalgebra is normal if and only if it is a Hopf-Galois extension. We find a class of examples of the alternative Hopf algebroids in...

1. Relations 1 1.1. The idea of a relation 1 1.2. The formal definition of a relation 2 1.3. Basic terminology and further examples 2 1.4. Properties of relations 4 1.5. Partitions and Equivalence Relations 6 1.6. Examples of equivalence relations 7 1.7. Extra: composition of relations 8 2. Functions 9 2.1. The set of all functions from X to Y 10 2.2. Injective functions 10 2.3. Surjective func...

for X a variety and L a line bundle on X. Denoting by Kp,q(X,L) the cohomology at the middle of the sequence above, one sees immediately that the surjectivity of the map μ0 is equivalent to K0,2(C,KC) = 0, and that if this is the case, the ideal I is generated by quadrics if and only if K1,2(C,KC) = 0. On the other hand, C being non hyperelliptic is equivalent to the fact that the Clifford inde...

Making suitable generalizations of known results we prove some general facts about Gaussian maps. The above are then used, in the second part of the article, to give a set of conditions that insure the surjectivity of Gaussian maps for curves on Enriques surfaces. To do this we also solve a problem of independent interest: a tetragonal curve of genus g ≥ 7 lying on an Enriques surface and gener...

We denote by σ(F,E) the topology on F generated by the family {ω(x, ε) : x ∈ E, ε > 0} as a subbase for the neighbourhood system at 0. It is easy to show that, if F possesses the σ(F,E)-topology, F becomes a locally convex topological vector space. The σ(E,F )-topology on E is defined analogously. A subset X of E is said to be σ(E,F )-compact if X is compact related to the σ(E,F )-topology. Let...

We investigate the surjectivity of the word map defined by the n-th Engel word on the groups PSL(2, q) and SL(2, q). For SL(2, q), we show that this map is surjective onto the subset SL(2, q)\{−id} ⊂ SL(2, q) provided that q ≥ q0(n) is sufficiently large. Moreover, we give an estimate for q0(n). We also present examples demonstrating that this does not hold for all q. We conclude that the n-th ...

Surjectivity results of Fredholm alternative type are obtained for nonlinear operator equations of the form λT (x)−S(x) = f , where T is invertible, and T, S satisfy various types of homogeneity conditions. We are able to answer some questions left open by Fuč́ık, Nečas, Souček, and Souček. We employ the concept of an a-stably-solvable operator, related to nonlinear spectral theory methodology. ...

This paper uses Morse-theoretic techniques to compute the equivariant Betti numbers of the space of semistable rank two degree zero Higgs bundles over a compact Riemann surface, a method in the spirit of Atiyah and Bott’s original approach for semistable holomorphic bundles. This leads to a natural proof that the hyperkähler Kirwan map is surjective for the non-fixed determinant case. CONTENTS

We show that the iterated images of a Jacobian pair f : C 2 → C 2 stabilize; that is, all the sets f k (C 2) are equal for k sufficiently large. More generally, let X be a closed algebraic subset of C N , and f : X → X an open polynomial map with X − f (X) a finite set. We show that the sets f k (X) stabilize, and for any cofinite subset Ω ⊆ X with f (Ω) ⊆ Ω, the sets f k (Ω) stabilize. We appl...