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Updated: Jul 20, 2026

Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
Astronomical constraints on the cosmic evolution of the fine structure constant and possible quantum dimensions
C L Carilli1, K M Menten, J T Stocke
1National Radio Astronomy Observatory, Socorro, New Mexico 87801, USA.
Abstract:
We present measurements of absorption by the 21 cm hyperfine transition of neutral hydrogen toward radio sources at substantial look-back times. These data are used in combination with observations of rotational transitions of common interstellar molecules to set limits on the evolution of the fine structure constant: alpha/ alpha<3.5x10(-15) yr(-1), to a look-back time of 4.8 Gyr. In the context of string theory, the limit on the secular evolution of the scale factor of the compact dimensions, R, is &Rdot/ R<10(-15) yr(-1). Including terrestrial and other astronomical measurements places 2sigma limits on slow oscillations of R from the present to the epoch of cosmic nucleosynthesis, just seconds after the big bang, of DeltaR /R<10(-5).
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