Supermodular mechanism design

This paper introduces a mechanism design approach that allows dealing with the multiple equilibrium problem, using mechanisms that are robust to bounded rationality. This approach is a tool for constructing supermodular mechanisms, i.e. mechanisms that induce games with strategic complementarities. In quasilinear environments, I prove that if a social choice function can be implemented by a mechanism that generates bounded strategic substitutes - as opposed to strategic complementarities - then this mechanism can be converted into a supermodular mechanism that implements the social choice function. If the social choice function also satisfies some efficiency criterion, then it admits a supermodular mechanism that balances the budget. Building on these results, I address the multiple equilibrium problem. I provide sufficient conditions for a social choice function to be implementable with a supermodular mechanism whose equilibria are contained in the smallest interval among all supermodular mechanisms. This is followed by conditions for supermodular implementability in unique equilibrium. Finally, I provide a revelation principle for supermodular implementation in environments with general preferences.Implementation, mechanisms, learning, strategic complementarities, supermodular games

Microcavity-like exciton-polaritons can be the primary photoexcitation in bare organic semiconductors.

Strong-coupling between excitons and confined photonic modes can lead to the formation of new quasi-particles termed exciton-polaritons which can display a range of interesting properties such as super-fluidity, ultrafast transport and Bose-Einstein condensation. Strong-coupling typically occurs when an excitonic material is confided in a dielectric or plasmonic microcavity. Here, we show polaritons can form at room temperature in a range of chemically diverse, organic semiconductor thin films, despite the absence of an external cavity. We find evidence of strong light-matter coupling via angle-dependent peak splittings in the reflectivity spectra of the materials and emission from collective polariton states. We additionally show exciton-polaritons are the primary photoexcitation in these organic materials by directly imaging their ultrafast (5 × 106 m s-1), ultralong (~270 nm) transport. These results open-up new fundamental physics and could enable a new generation of organic optoelectronic and light harvesting devices based on cavity-free exciton-polaritons.EPSRC (EP/R025517/1), EPSRC (EP/M025330/1), ERC Horizon 2020 (grant agreements No 670405 and No 758826), ERC (ERC-2014-STG H2020 639088), Netherlands Organisation for Scientific Research, Swedish Research Council (VR, 2014-06948), Knut and Alice Wallenberg Foundation 3DEM-NATUR (no. 2012.0112), Royal Commission for the Exhibition of 1851, CNRS (France), US Department of Energy, Office of Science, Basic Energy Sciences, CPIMS Program, Early Career Research Program (DE-SC0019188)

Supermodular mechanism design

[This item is a preserved copy. To view the original, visit http://econtheory.org/] This paper introduces a mechanism design approach that allows dealing with the multiple equilibrium problem, using mechanisms that are robust to bounded rationality. This approach is a tool for constructing supermodular mechanisms, i.e. mechanisms that induce games with strategic complementarities. In quasilinear environments, I prove that if a social choice function can be implemented by a mechanism that generates bounded strategic substitutes - as opposed to strategic complementarities - then this mechanism can be converted into a supermodular mechanism that implements the social choice function. If the social choice function also satisfies some efficiency criterion, then it admits a supermodular mechanism that balances the budget. Building on these results, I address the multiple equilibrium problem. I provide sufficient conditions for a social choice function to be implementable with a supermodular mechanism whose equilibria are contained in the smallest interval among all supermodular mechanisms. This is followed by conditions for supermodular implementability in unique equilibrium. Finally, I provide a revelation principle for supermodular implementation in environments with general preferences

Impact of preoperative brachytherapy followed by radical hysterectomy in stage IB2 (FIGO 2018) cervical cancer: An analysis of SENTICOL I-II trials

International audienceIntroduction: The goal of this study was to compare the outcomes of preoperative brachytherapy followed by radical surgery versus radical surgery alone in cervical cancer with tumor between 2 and 4 cm (FIGO 2018 IB2). Material and methods: SENTICOL I and SENTICOL II were two French prospective multicentric trials evaluating sentinel node biopsy in early-stage cervical cancer between 2005 and 2012. Preoperative brachytherapy (low-dose rate or pulse-dose rate at the dose of 60Gy) could be performed 6 to 8 weeks prior to the radical hysterectomy, at the discretion of each center. SENTICOL I and SENTICOL II cohorts were retrospectively analysed to compare the outcomes of preoperative brachytherapy or upfront surgery in patients with IB2 cervical tumor. Results: A total of 104 patients were included: 55 underwent upfront radical hysterectomy and 49 underwent preoperative brachytherapy followed by radical hysterectomy. Patients with preoperative brachytherapy were more likely to have no residual disease (71.4% vs. 25.5%, p < 0.0001) and to be defined as low risk according to Sedlis criteria (83.3% vs. 51.2%, p < 0.0001). Adjuvant treatments were required less frequently in case of preoperative brachytherapy (14.3% vs. 54.5%, p < 0.0001). Patients with preoperative brachytherapy experienced more postoperative complications grade ≥ 3 (24.5% vs. 9.1%, p = 0.03). Patients with preoperative brachytherapy had better 5-year disease-free survival compared to patients who underwent surgery alone, 93.6% and 74.4% respectively (p = 0.04). Conclusion: Although preoperative brachytherapy was significantly associated with more severe postoperative complications, better pathologic features were obtained on surgical specimens and led to a better 5-year disease-free survival in IB2 cervical cancer