Test of Lorentz Invariance at the South Pole

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Lorentz symmetry, the feature of nature that makes experimental results independent of the orientation or the boost velocity of the laboratory through space, lies at the foundation of both the quantum field theory and the theory of general relativity. Their unification is regarded as one of the biggest, but yet unmet, challenges in physics. Special relativity postulates that all laws of physics are invariant under Lorentz transformations, which include ordinary rotations and changes in the velocity of a reference frame. Subsequently, quantum field theories all incorporated Lorentz Invariance in their basic structure. The force of gravity, unlike other fundamental forces, is characterized by a dimensionful coupling constant that introduces a characteristic energy of the Plank scale. However, the existence of such fixed high energy scale is not Lorentz-invariant; hence, tests of Lorentz symmetry attract a lot of interest as one of the most promising ways for searching experimental effects of the quantum gravity. Respective high-sensitivity experimental techniques were developed to search for a spatial anisotropy caused by Lorentz-violating spin interaction. Spatial anisotropy of an Earth laboratory is mainly defined by three effects: gravity, magnetic fields, and Earth rotation. Spin measurements are particularly sensitive to rotations which mimic Lorentz violating effects, while gravity affects the mechanical stability of the apparatus. In contrast, magnetic fields can be relatively easily shielded. Therefore, the most isotropic location for such experiments is at one of the geographic poles, where Earth rotation vector is parallel to the gravity vector. This award is to test Lorentz Invariance with unprecedented precision by deploying a very sensitive atomic spin sensor at the South Pole Station in Antarctica, where it is unaffected by the Earth's rotation. The experiment will constrain several possible forms of Lorentz violation in the sensitivity range where the effects of quantum gravity can be expected, improving existing limits by a factor of thousand. The project will attract wide attention as a simple test of the spatial isotropy of the Universe, and observation of any finite effects would certainly have a tremendous impact on the understanding of space-time shedding light on one of the most challenging problems in physics ? origin of gravity. The project will also involve training for the postdocs and students at the graduate and undergraduate levels.