Researchers
studying a strange state of matter have discovered that it acts similarly to
the accelerated expansion of the early universe, which could allow astrophysicists
to test new models in laboratory settings.
The research,
published in Physical Review X, looked at a Bose-Einstein condensate (BEC), a
state of matter where a diluted gas of particles is cooled to nearly absolute
zero. The researchers were observing the expansion of such a state by escalating
a cloud of atoms in a donut shape. This escalation was so fast that it left all
the gas vibrating, in what the researchers call humming.
So how
does this humming link to the astronomy? The universe is thought to have
experienced a same period of rapid expansion in the first moments after the Big
Bang. This time, known as cosmic inflation, is still not well understood but,
using a BEC it might be possible to clear some uncertainties.
"From
the atomic physics viewpoint, the experiment is beautifully defined by existing
theory, but even more prominent is how that theory links with cosmology," told
lead author Stephen Eckel, from the National Institute of Standards and
Technology, in a statement.
"Maybe
this will one day update future models of cosmology. Or vice versa. Maybe there
will be a model of cosmology that's hard to solve but that you could pretend
using a cold atomic gas."
BECs are
systems where quantum processes become apparent and since the particles in a
BEC have very slight free energy (as they are so cold) it is probable to use
them for simulating some difficult and at times extreme physical phenomena.
BECs have been effectively used to simulate black holes.
The researchers
planned two experiments. In the first, they looked at how waves transmit in an
expanding medium. They put a sound wave in the primary BEC and studied how it transformed
as the condensate expanded. The sound wave ended up stretched and scattered,
and the diminishing effect looked like the cosmological parameter called Hubble
friction, which plays a significant role in cosmic inflation. Scientists also
let the gas expand without any sound waves, and they still observed vibrations
in the gas simulating what’s found in cosmological theories.
While exciting,
this is not a direct assessment between the whole universe and the BEC. An
important point of difference is the energy transfer. In cosmic inflation, some
of the surplus energy ends up converting into matter and light, but nothing alike
was seen in the BEC. Quantum effects become dominant there generating vortices,
making the ring rotate, and shifting the properties of the atoms.
The team
hopes to better understand these energy transfers and continue looking for
cosmological analogies in BECs.
References:
https://www.iflscience.com/physics/expanding-universe-recreated-in-the-lab-thanks-to-humming-atoms/
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