Benedetto Manca (University of Cagliari) 

will give a presentation on : 

Random Projections for Mathematical Programming. 

Abstract : 

Random projections are random linear maps which approximately preserve geometrical quantities. The Johson-Lindenstrauss Lemma states that there exist random projections with a relatively small number of rows which preserve the pairwise Euclidean distances among a set of points. 
In the past years several results on the application of random projections to Mathematical Programming instances are being obtained, showing that it is possible to obtain an approximate formulation with less decision variables and constraints and therefore easier to solve. 
In this talk I will introduce the generic framework of random projections for Mathematical Programming formulations and I will present more in details some results in the case of Linear Programming, Quadratic Programming and the Minimum Sum of Squares problem. 

Yukihiro Nishimura (Osaka University) 

will give a presentation on : 

Tax Reform on Monopoly Platformer in Borderless Economy: The Incidence on Prices and Efficiency Consequences. 

Abstract : 

As development of online market brings ongoing concerns that foreign app suppliers avoid value-added tax (VAT) in a domestic country, some countries design a tax reform which makes platform pay VAT instead of app suppliers (platform taxation). In the market where the monopoly platformer determines the prices of the network good and the commission fee of the platform services (with online apps as a representative example), this study investigates whether the prevention of tax leaks by platform tax improves the welfare of the host country, as well as the extent of the cross-market incidence of the two-sided market. We find that the tax reform reduces foreign app suppliers and consumption of a network good such as smartphones, with substantial extent of cross-market pass-through. The effect of the tax reform on home app suppliers crucially depends on the responsiveness of the app supplies from the number of users, which we call entry elasticity. Platform tax also increases the tax burden laid on the network product, but the monopoly seller let the increase of the tax burden born entirely by consumers. We also show that digitalization reduces the loss of welfare as well as tax planning by the platformer.

Exceptionally, this seminar will be accessible online via Teams

Vali Asimit (Bayes Business School) 

give a presentation on : 

Risk Budgeting under General Risk Measures. 

Abstract : 

We provide an ample characterization for Risk Budgeting/Parity portfolios with general convex and homogeneous risk preferences for long-only portfolios, as well as for long-short portfolios. We propose a more general novel definition of Risk Budgeting/ Parity portfolios that is less restrictive than the classical definition, and it guarantees their existence and uniqueness, at least for the long-only case. This case is shown to always be less risky than the Equal Weighted portfolio and a thorough mathematical characterization of Risk Budgeting/Parity portfolios is also provided. Equivalent properties are concluded for long-short risk budgeting portfolios under some additional conditions. We provide new insights about the Risk Budgeting/Parity portfolios, including that those portfolios are a rich subset of the newly coined set of Generalized Weighted Mean Constrained portfolios that, according to our knowledge, is defined for the first time in this paper. This new class of portfolios contains other portfolios with good performance, e.g., norm constrained and shortsale-constrained portfolios.