Thursday, November 6, 2014, 16:00
WHGA/Auditorium
René Sedmik, Vrije Universiteit Amsterdam
Abstract:
Obviously, Casimir (van der Waals) forces and dark energy have nothing
in common.
While the primer one is acting in a (mostly) attractive way on the
micrometer scale, the other one is thought to be connected with
repulsive interactions over the vast void spaces between galaxies.
Vacuum fluctuations as sources for Casimir interactions are fairly well
understood while the mechanisms underlying dark energy are completely
unknown. Yet, there exist some approaches aiming to shed light on this
problem. A recently proposed theory suggests that hypothetical Yukawa
interactions, which vary their coupling constants with the local energy
density, could explain the observed expansion of the universe. Being
dubbed `Chameleon' forces for their adaptivity, these interactions would
be strong on cosmological scales but weak near massive objects for which
reason they could elude discovery - until now.
In the Casimir and non-Newtonian force experiment (Cannex) we attempt to
detect minuscule predicted deviations in the forces between two
macroscopic parallel plates due to Chameleon interactions. Aiming at a
sensitivity of 0.1 pN we may, however, not only be able to give new
upper limits to the the strength of Chameleon forces but also to measure
Casimir interactions at unprecedented accuracy under very well defined
conditions. The latter forces not only have practical relevance, as they
represent a serious obstacle to the miniaturization of
micro-electromechanical systems, but are also interesting in terms of
fundamental physics. Our results will potentially lead to new insights
and answer long-standing questions regarding the actual nature of
dielectric functions being at the heart of our understanding of Casimir
interactions.
However, The required force sensitivity comes at the price of
several technical hurdles. Perfectly flat and parallel macroscopic
plates, a novel type of force transducer, custom-built vibration and
sound isolation systems, and an eight digit capacitive readout had to be
designed and built. Cannex is an ongoing project, which is currently in
the testing and debugging phase. In this talk, besides giving an
overview of the theories and open questions in Casimir and Chameleon
physics, the experiment, its status, and some preliminary results will
be presented.