The Renormalization Group flow of unimodular f(R) gravity

Unimodular gravity is classically equivalent to General Relativity. This equivalence extends to actions which are functions of the curvature scalar. At the quantum level, the dynamics could differ. Most importantly, the cosmological constant is not a coupling in the unimodular action, providing a new vantage point from which to address the cosmological constant fine-tuning problem. Here, a quantum theory based on the asymptotic safety scenario is studied, and evidence for an interacting fixed point in unimodular f(R) gravity is found. We study the fixed point and its properties, and also discuss the compatibility of unimodular asymptotic safety with dynamical matter, finding evidence for its compatibility with the matter degrees of freedom of the Standard Model.Comment: 17 pages, 2 figures; new version with some clarifications, identical to version to appear in JHE

Four Essays on Technological and Organizational Change in Health Care

This thesis contains four essays on technological and organizational change in health care. Although each chapter can be read independently, there is a central thread resumed in each chapter. The interaction of patient, physician and insurer in the health care market is analysed in different contexts. Chapter 2 studies the physician's decision to adopt new technologies in a situation where patients have control over the amount of health care consumed. This setup of ex-post moral hazard is complemented in chapter 3 by an analysis of supplier-induced demand. Providers' technology choice and adoption of innovations here depend on the profitability of treatment and patients' willingness to consent. A conclusion which may be drawn from these sections is a call for a more integrated provision of health care in the form of managed care. Chapter 4 contains an analysis which explains why physicians, particularly in Germany, are often very much opposed to such new organizational forms of provision of care. In chapter 5, it is shown that patients may not always want to make use of the opportunities offered by technological progress. Information on one's health status which may be acquired, for instance, by genetic tests, may be declined by individuals who fear a breakdown of will. This finding has important implications for the disclosure of information by physicians and for the information acquisition policy of insurers

On the diagram of 132-avoiding permutations

The diagram of a 132-avoiding permutation can easily be characterized: it is simply the diagram of a partition. Based on this fact, we present a new bijection between 132-avoiding and 321-avoiding permutations. We will show that this bijection translates the correspondences between these permutations and Dyck paths given by Krattenthaler and by Billey-Jockusch-Stanley, respectively, to each other. Moreover, the diagram approach yields simple proofs for some enumerative results concerning forbidden patterns in 132-avoiding permutations.Comment: 20 pages; additional reference is adde

Probing hot and dense matter production in heavy ion collisions via neutral mesons and photons with the ALICE detector at the LHC

One of the key signatures of the Quark Gluon Plasma (QGP) is the modification of hadron and direct photon spectra in heavy-ion collisions as compared to proton-proton (pp) collisions. Suppression of hadron production at high transverse momenta in heavy-ion collisions can be explained by the energy loss of the partons produced in the hard scattering processes which traverse the hot and dense QCD matter. The dependence of the observed suppression on the transverse momentum (pT) of the measured hadron towards higher pT is an important input for the theoretical understanding of jet quenching effects in the QGP and the nature of energy loss. Another key observable which has helped establish the energy loss picture, is high pT direct photon production for which no suppression is expected. For low pT photon production, it is expected that thermal sources will lead to enhancement of direct photons. We report an overview of photon and neutral meson production measurements by the ALICE experiment at the LHC in heavy-ion and pp collisions.Comment: 6 pages, 10 figures, Conference Proceeding