A zero index metamaterial (ZIM) can be utilized to block wave (super-reflection) or conceal objects completely (cloaking). The super-reflection device is realized by a ZIM with a perfect electric (magnetic) conductor inclusion of arbitrary shape and
size for a transverse electric (magnetic) incident wave. In contrast, a ZIM with a perfect magnetic (electric) conductor inclusion for a transverse electric (magnetic) incident wave can be used to conceal objects of arbitrary shape. The underlying physics here is determined by the intrinsic properties of the ZIM.
The current accelerated expansion of our universe could be due to an unknown energy component (dark energy) or a modification to general relativity (modified gravity). In the literature, it has been proposed that combining the probes of the cosmic ex
pansion history and growth history can distinguish between dark energy and modified gravity. In this work, without invoking non-trivial dark energy clustering, we show that the possible interaction between dark energy and dark matter could make the interacting dark energy model and the modified gravity model indistinguishable. An explicit example is also given. Therefore, it is required to seek some complementary probes beyond the ones of cosmic expansion history and growth history.
