Theories Beyond Einstein

Theories beyond Einstein

Modified theories of gravity have been proposed to explain some anomalies in the observation of astrophysical phenomena. The rotation curves of galaxies suggest the presence of dark matter in galaxies, but the latter can be both interpreted as a new weakly interacting particle, such as an axion, or as a modification to Einstein's theory at large scales. Similarly, the late-time acceleration of the universe can be interpreted as a non-vanishing (yet extremely small) cosmological constant, as a "strange" fluid with repulsive gravitational properties, or as a modification to Einstein's theory.

Professor Yunes' group studies some of these beyond Einstein theories in an effort to contrast them to all data available, from that obtained in the Solar System, to that from binary pulsars and using gravitational waves. The philosophy behind this is that any modification to Einstein's theory need not only "solve" a particular problem in fundamental physics, but it ought to also pass the plethora of tests performed in the gravitational sector. Such comparisons of theory and data require a deep understanding of the physics involved in these modified theories, the calculation and modeling of observables and the use of data to discern between models. These efforts can then allow us to constrain the parameter space of beyond Einstein theories to determine whether the space allowed can still solve the problems these theories were designed to address.

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