FeynOnium: Using FeynCalc for automatic calculations in Nonrelativistic Effective Field Theories

We present new results on FeynOnium, an ongoing project to develop a general purpose software toolkit for semi-automatic symbolic calculations in nonrelativistic Effective Field Theories (EFTs). Building upon FeynCalc, an existing Mathematica package for symbolic evaluation of Feynman diagrams, we have created a powerful framework for automatizing calculations in nonrelativistic EFTs (NREFTs) at tree- and 1-loop level. This is achieved by exploiting the novel features of FeynCalc that support manipulations of Cartesian tensors, Pauli matrices and nonstandard loop integrals. Additional operations that are common in nonrelativistic EFT calculations are implemented in a dedicated add-on called FeynOnium. While our current focus is on EFTs for strong interactions of heavy quarks, extensions to other systems that admit a nonrelativistic EFT description are planned for the future. All our codes are open-source and publicly available. Furthermore, we provide several example calculations that demonstrate how FeynOnium can be employed to reproduce known results from the literature.Comment: 61 pages, no figures, matches the version accepted in JHEP. To obtain the programs, see https://github.com/FeynCal

Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Essays on coordination, conflict and networks

(ECGE - Sciences économiques et de gestion) -- UCL, 201

Exploiting social influence in networks

We study binary action network games with strategic complementarities. An agent acts if the aggregate social influence of her friends exceeds a transfer levied on the agent by a principal. The principal seeks to maximize her revenue while inducing everyone to act in a unique equilibrium. We characterize optimal transfers showing that agents who are more popular than their friends receive preferential treatment. Our main result is that under mild conditions complete core‐periphery networks deliver the highest revenue to the principal. Furthermore, we show that the revenue is higher in networks where links are allocated unequally across agents. Hence, the principal benefits from creating “influentials” by linking well‐connected hubs to less popular periphery

Saddle functions and robust sets of equilibria

We provide a new sufficient condition for the robustness of sets of equilibria to incomplete information in the sense of Kajii and Morris (1997), Morris and Ui (2005). The condition is formulated for games with a saddle function. A saddle function is a real-valued function on the set of action profiles such that there is a single player for whom minimizing the function implies choosing her best response, and for the other players maximizing the function implies choosing their best responses. In a game with a saddle function the set of correlated equilibria that induce an expectation of the saddle function greater or equal to its maximin value is robust to incomplete information