%0 Book Section %B Model Reduction of Parametrized Systems %D 2017 %T Reduced-order semi-implicit schemes for fluid-structure interaction problems %A F. Ballarin %A Gianluigi Rozza %A Yvon Maday %E Peter Benner %E Mario Ohlberger %E Anthony Patera %E Gianluigi Rozza %E Karsten Urban %X

POD–Galerkin reduced-order models (ROMs) for fluid-structure interaction problems (incompressible fluid and thin structure) are proposed in this paper. Both the high-fidelity and reduced-order methods are based on a Chorin-Temam operator-splitting approach. Two different reduced-order methods are proposed, which differ on velocity continuity condition, imposed weakly or strongly, respectively. The resulting ROMs are tested and compared on a representative haemodynamics test case characterized by wave propagation, in order to assess the capabilities of the proposed strategies.

%B Model Reduction of Parametrized Systems %I Springer International Publishing %P 149–167 %G eng %& Reduced-order semi-implicit schemes for fluid-structure interaction problems %R 10.1007/978-3-319-58786-8_10 %0 Journal Article %J Phys. Rev. D %D 2016 %T Towards a gauge theory interpretation of the real topological string %A Hayashi, Hirotaka %A Nicolò Piazzalunga %A Uranga, Angel M. %X

We consider the real topological string on certain noncompact toric Calabi-Yau three-folds $\mathbb{X}$, in its physical realization describing an orientifold of type IIA on $\mathbb{X}$ with an O4-plane and a single D4-brane stuck on top. The orientifold can be regarded as a new kind of surface operator on the gauge theory with 8 supercharges arising from the singular geometry. We use the M-theory lift of this system to compute the real Gopakumar-Vafa invariants (describing wrapped M2-brane Bogomol’nyi-Prasad-Sommerfield (BPS) states) for diverse geometries. We show that the real topological string amplitudes pick up certain signs across flop transitions, in a well-defined pattern consistent with continuity of the real BPS invariants. We further give some preliminary proposals of an intrinsically gauge theoretical description of the effect of the surface operator in the gauge theory partition function.

%B Phys. Rev. D %I American Physical Society %V 93 %P 066001 %8 Mar %G eng %U https://link.aps.org/doi/10.1103/PhysRevD.93.066001 %R 10.1103/PhysRevD.93.066001 %0 Journal Article %J Advances in Computational Mathematics %D 2015 %T Model order reduction of parameterized systems (MoRePaS): Preface to the special issue of advances in computational mathematics %A Peter Benner %A Mario Ohlberger %A Anthony Patera %A Gianluigi Rozza %A Sorensen, D.C. %A Karsten Urban %B Advances in Computational Mathematics %V 41 %P 955–960 %G eng %R 10.1007/s10444-015-9443-y %0 Journal Article %J Journal of High Energy Physics %D 2014 %T M-theory interpretation of the real topological string %A Nicolò Piazzalunga %A Uranga, Angel M. %X

We describe the type IIA physical realization of the unoriented topological string introduced by Walcher, describe its M-theory lift, and show that it allows to compute the open and unoriented topological amplitude in terms of one-loop diagram of BPS M2-brane states. This confirms and allows to generalize the conjectured BPS integer expansion of the topological amplitude. The M-theory lift of the orientifold is freely acting on the M-theory circle, so that integer multiplicities are a weighted version of the (equivariant subsector of the) original closed oriented Gopakumar-Vafa invariants. The M-theory lift also provides new perspective on the topological tadpole cancellation conditions. We finally comment on the M-theory version of other unoriented topological strings, and clarify certain misidentifications in earlier discussions in the literature.

%B Journal of High Energy Physics %V 2014 %P 54 %8 Aug %G eng %U https://doi.org/10.1007/JHEP08(2014)054 %R 10.1007/JHEP08(2014)054