### Seminari

### Prossimi Seminari

**Coupled problems in Environmental and medical applications**

Hiroshi Suito, Mathematical Science Group, Advanced Institute for Materials Research, Tohoku University, Japan

martedì 18 settembre 2018 alle ore 14:00, Aula Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANO**Computational Prediction of Blood Damage**

Marek Behr, Chair for Computational Analysis of Technical Systems Faculty of Mechanical Engineering, RWTH Aachen

lunedì 1 ottobre 2018 alle ore 14:00, Aula Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANO**Elastic waves in soft tissues: inverse analysis, experiments, simulations, validation**

Michel Destrade, Chair of Applied Mathematics at NUI Galway

giovedì 18 ottobre 2018 alle ore 14:00, Aula Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANO**BIRATIONAL EQUIVALENCE OF ALGEBRAIC VARIETIES**

Shigefumi Mori, Kyoto University Institute of Advanced Study

lunedì 26 novembre 2018 alle ore 16:30, Aula Chisini, Diparimento di Matematica, Via C. Saldini 50

### Seminari Passati

**A new paradigm for geometric modeling: Pythagorean Hodograph (PH) B-Spline curves**

Gudrun Albrecht, National University of Colombia

martedì 31 luglio 2018 alle ore 14:00, Aula Seminari ‘Saleri’ VI Piano MOX-Dipartimento di Matematica, Politecnico di Milano – Edificio 14ABSTRACTWe introduce the new class of planar Pythagorean-Hodograph (PH) B–Spline curves. They can be seen as a generalization of the well-known class of planar Pythagorean-Hodograph (PH) Bézier curves, presented by R. Farouki and T. Sakkalis in 1990, including the latter ones as special cases. Pythagorean-Hodograph B–Spline curves are nonuniform parametric B–Spline curves whose arc-length is a B–Spline function as well. An important consequence of this special property is that the offsets of Pythagorean-Hodograph B–Spline curves are non-uniform rational B–Spline (NURBS) curves. Thus, although Pythagorean-Hodograph B–Spline curves have fewer degrees of freedom than general B–Spline curves of the same degree, they offer unique advantages for computer-aided design and manufacturing, robotics, motion control, path planning, computer graphics, animation, and related fields. After providing a general definition for this new class of planar parametric curves, we !

present useful formulae for their construction and discuss their remarkable attractive properties. Then we provide a method to determine within the set of all PH B–Splines the one that is closest to a given reference spline having the same degree and knot partition.

Contact franca.calio@polimi.it

**Optimal control of treatment time in a diffuse interface model of tumor growth and related issues**

Elisabetta Rocca, Università di Pavia

giovedì 28 giugno 2018 alle ore 11:15, Aula Seminari ‘Saleri’ VI Piano MOX-Dipartimento di Matematica, Politecnico di Milano – Edificio 14ABSTRACTWe consider an optimal control problem for a diffuse interface model of tumor growth. The state equations couples a Cahn-Hilliard equation and a reaction-diffusion equation, which models the growth of a tumor in the presence of a nutrient and surrounded by host tissue. The introduction of cytotoxic drugs into the system serves to eliminate the tumor cells and in this setting the concentration of the cytotoxic drugs will act as the control variable. Furthermore, we allow the objective functional to depend on a free time variable, which represents the unknown treatment time to be optimized. As a result, we obtain first order necessary optimality conditions for both the cytotoxic concentration and the treatment time

Contact: pasquale.ciarletta@polimi.it

**VAPORIZING AND FREEZING THE RIEMANN ZETA FUNCTION**

Terence Tao, University of California, Los Angeles

venerdì 22 giugno 2018 alle ore 14:30, Edificio U4, P.zza della Scienza, 4, Aula Luisella SironiABSTRACTIn 1950, de Bruijn studied the effect of evolving the Riemann zeta function (or more precisely, a closely related function known as the Riemann xi function) by the (backwards) heat equation. His analysis, together with later work by Newman, showed that there existed a finite constant Lambda, at most 1/2 in value, such that the Riemann hypothesis for this evolved function was true at times greater than or equal to Lambda, and false below that threshold. Thus the Riemann hypothesis for the zeta function is equivalent to Lambda being non-positive. Recently, in joint work with Brad Rodgers, I was able to establish the complementary estimate that Lambda is non-negative, confirming a conjecture of Newman; thus, the Riemann hypothesis for zeta, if true, is only “barely so”. The proof relies on an analysis of the dynamics of zeroes of entire functions under heat flow; it turns out that as one evolves forward in time, the zeroes “freeze” into approximate arithmetic progressions, while if one evolves backwards, the zeroes “vaporize” to leave the critical line. In followup work in an online collaborative “Polymath” project, the upper bound on Lambda has also been improved. We describe these results and their proofs in this talk.

**Approximating the true time weighted return**

Marco Guzzetti, Politecnico di Milano

mercoledì 20 giugno 2018 alle ore 12:15 precise, Aula seminari del Terzo piano**Bridgeland stability and the genus of space curves**

Emanuele Macrì, Northeastern University, Department of Mathematics

martedì 19 giugno 2018 alle ore 14:30 precise, Aula seminari del terzo pianoABSTRACTI will give an introduction to various notions of stability in the bounded derived category of coherent sheaves on the three-dimensional projective space. As application I will show how to possibly use these techniques towards the study of space curves. This is joint work with Benjamin Schmidt.**Linear and nonlinear equations for beams and degenerate plates with double piers**

Maurizio Garrione, Politecnico di Milano

martedì 19 giugno 2018 alle ore 15:45, Aula seminari 6° pianoABSTRACTMotivated by the phenomena observed on the occasion of the famous Tacoma Narrows Bridge collapse in 1940, we deal with some nonlinear fourth-order differential equations related to the analysis of the dynamics of suspension bridges. Following a “structural” approach, we discuss the role of the position of intermediate piers in the stability of a hinged beam, making a comparison between different notions of stability. The analysis is carried out analytically, with some help from numerics. (Joint work with Filippo Gazzola)**Joint and Individual Variation Explained**

Steve Marron, Department of Statistics and O.R., University of North Carolina

lunedì 18 giugno 2018 alle ore 14:00, Aula Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANOABSTRACTA major challenge in the age of Big Data is the integration of disparate data types into a data analysis. That is tackled here in the context of data blocks measured on a common set of experimental subjects. This data structure motivates the simultaneous exploration of the joint and individual variation within each data block. This is done here in a way that scales well to large data sets (with blocks of wildly disparate size), using principal angle analysis, careful formulation of the underlying linear algebra, and differing outputs depending on the analytical goals. Ideas are illustrated using mortality, cancer and neuroimaging data sets.

Contact: piercesare.secchi@polimi.it**Learning the Optimal Risk – Advanced Risk-Based Portfolio Management with Global Optimization Algorithms**

Marco Scaringi, Intesa Sanpaolo

martedì 12 giugno 2018 alle ore 13:45 precise, Aula Seminari Terzo Piano