Bulletin of the American Physical Society
APS April Meeting 2016
Volume 61, Number 6
Saturday–Tuesday, April 16–19, 2016; Salt Lake City, Utah
Session B6: Laboratory Searches for Dark Energy Scalar FieldsInvited
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Sponsoring Units: GPMFC Room: 150ABC |
Saturday, April 16, 2016 10:45AM - 11:21AM |
B6.00001: Chameleons and Their Phenomenology Invited Speaker: Justin Khoury If dark energy consists of a light scalar field, it might be detectable as a “fifth force” between ordinary-matter objects, in potential conflict with precision tests of gravity. Chameleon fields and other theories with screening mechanisms, however, can evade these tests by suppressing the forces in regions of high density, such as the laboratory. The manifestation of chameleons therefore depends sensitively on their environment, which in turn leads to striking experimental signatures. I will review chameleon field theories, their phenomenology, and recent experimental constraints using atom interferometry. [Preview Abstract] |
Saturday, April 16, 2016 11:21AM - 11:57AM |
B6.00002: Atom-Interferometry Constraints on Dark Energy Invited Speaker: Holger Mueller If dark energy is a light scalar field, it might interact with normal matter. The interactions, however, are suppressed in some leading models, which are thus compatible with current cosmological observations as well as solar-system and laboratory studies. Such suppression typically relies on the scalar's interaction with macroscopic amounts of ordinary matter, but can be bypassed by studying the interaction with individual particles. Using an atom interferometer, we have placed tight constraints on so-called chameleon models, ruling out interaction parameters $\beta_M > 4\times 10^4$. This limit is improved by 2.5 orders of magnitude relative to previous experiments. We have already increased the sensitivity of our interferometer hundredfold and are expecting a new constraint soon. Purpose-built experiments in the lab or on the international space station will completely close the gap and rule out out chameleons and other theories, such as axions, dark photons, symmetrons or $f(R)$ gravity. [Preview Abstract] |
Saturday, April 16, 2016 11:57AM - 12:33PM |
B6.00003: Neutron Limit on the Strongly-Coupled Chameleon Field Invited Speaker: Dmitry Pushin One of the major open questions of cosmology is the physical origin of the dark energy. There are a few sets of theories which might explain this origin that could be tested experimentally. The chameleon dark energy theory postulates self-interacting scalar field that couples to matter. This coupling induces a screening mechanism chosen so that the field amplitude is nonzero in empty space but is greatly suppressed in regions of terrestrial matter density. On behalf of the INDEX collaboration, I will report the most stringent upper bound on the free neutron-chameleon coupling in the strongly-coupled limit of the chameleon theory using neutron interferometric techniques. In our experiment we measure neutron phase induced by chameleon field. We report a $95\%$ confidence level upper bound on the neutron-chameleon coupling ranging from $\beta<4.7\times 10^6$ for a Ratra-Peebles index of $n = 1$ in the nonlinear scalar field potential to $\beta < 2.4\times 10^7$ for $n = 6$, one order of magnitude more sensitive than the most recent free neutron limit for intermediate n. [Preview Abstract] |
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