Archive ouverte UNIGE | last documents for author 'Hillary Adrienne Sanctuary'https://archive-ouverte.unige.ch/Latest objects deposited in the Archive ouverte UNIGE for author 'Hillary Adrienne Sanctuary'engEffective field theory analysis of the self-interacting chameleonhttps://archive-ouverte.unige.ch/unige:115910https://archive-ouverte.unige.ch/unige:115910We analyse the phenomenology of a self-interacting scalar field in the context of the chameleon scenario originally proposed by Khoury and Weltman. In the absence of self-interactions, this type of scalar field can mediate long range interactions and simultaneously evade constraints from violation of the weak equivalence principle. By applying to such a scalar field the effective field theory method proposed for Einstein gravity by Goldberger and Rothstein, we give a thorough perturbative evaluation of the importance of non-derivative self-interactions in determining the strength of the chameleon mediated force in the case of orbital motion. The self-interactions are potentially dangerous as they can change the long range behaviour of the field. Nevertheless, we show that they do not lead to any dramatic phenomenological consequence with respect to the linear case and solar system constraints are fulfilled.Tue, 09 Apr 2019 11:17:19 +0200Extracting the three- and four-graviton vertices from binary pulsars and coalescing binarieshttps://archive-ouverte.unige.ch/unige:35672https://archive-ouverte.unige.ch/unige:35672Using a formulation of the post-Newtonian expansion in terms of Feynman graphs, we discuss how various tests of general relativity (GR) can be translated into measurement of the three- and four-graviton vertices. In problems involving only the conservative dynamics of a system, a deviation of the three-graviton vertex from the GR prediction is equivalent, to lowest order, to the introduction of the parameter βPPN in the parametrized post-Newtonian formalism, and its strongest bound comes from lunar laser ranging, which measures it at the 0.02% level. Deviation of the three-graviton vertex from the GR prediction, however, also affects the radiative sector of the theory. We show that the timing of the Hulse-Taylor binary pulsar provides a bound on the deviation of the three-graviton vertex from the GR prediction at the 0.1% level. For coalescing binaries at interferometers we find that, because of degeneracies with other parameters in the template such as mass and spin, the effects of modified three- and four-graviton vertices is just to induce an error in the determination of these parameters and, at least in the restricted PN approximation, it is not possible to use coalescing binaries for constraining deviations of the vertices from the GR predictionMon, 14 Apr 2014 15:59:55 +0200On Testing Modified Gravity : with Solar System Experiments and Gravitational Radiationhttps://archive-ouverte.unige.ch/unige:28935https://archive-ouverte.unige.ch/unige:28935Three theories of gravitation – general relativity, the chameleon and Horava gravity - are confronted with experiment, using standard and adapted post-Newtonian (PN) tools. The laboratory is provided by the Solar System, binary pulsars and future detections at gravitational wave observatories. We test Horava gravity by studying emission of gravitational radiation in the weak-field limit for PN sources using techniques that take full advantage of the parametrized post-Newtonian (PPN) formalism. In particular, we provide a generalization of Einstein's quadrupole formula and show that a monopole persists even in the limit in which the PPN parameters are identical to those of General Relativity. Based on a technique called non-relativistic General Relativity, we propose a phenomenological way to measure deviations from General Relativity coming from an unknown UV completion. Finally, we systematically show that the self-interacting chameleon at orders three and higher do not jeopardize the chameleon theory for Solar System type objects.Fri, 19 Jul 2013 09:52:55 +0200