46 | New Scientist | 1 June 2019A
t first, we thought it was absurd,”
Asimina Arvanitaki tells me when
we meet in her office at the Perimeter
Institute for Theoretical Physics in Waterloo,
Canada. I’m not surprised. How else could you
respond to the idea that black holes generate
swirling clouds of planet-sized particles that
could be the dark matter thought to hold
galaxies together?
But this sort of thing is Arvanitaki’s
speciality. The first woman to hold a
professorship at the institute, she is making
a name for herself by taking neglected ideas,
however far out they might sound, and then
devising ingenious, inexpensive experiments
to test them out.
At a time when many seem to find it
increasingly hard to matchmake ideas in
theoretical physics and experiments, her
knack for that, allied to her tendency to stray
from the beaten path, sets Arvanitaki apart.
“I get bored easily,” she says. “I want to see
stuff. Otherwise, what’s the point?”
She can’t recall a moment she decided to
spend her life grappling with the mysteries
of the universe, but she does remember the
time, as a child in mainland Greece, when
she found out the value for the speed of light.
“I calculated that it takes 8 minutes for light
to get from the sun to Earth,” she says. “And
I realised then that we always see the past
of things, we can never see the present.”
She liked space, but she also liked cars,
and at high school had to decide between
engineering and physics. “I realised I was
more interested in understanding why
things work rather than how.”These days, her goal is to spot something
truly exotic. Although our best picture of
matter and its workings is a magnificent
achievement, describing as it does all known
particles and three of the four fundamental
forces in a neat set of equations, it is far from
perfect. We call this picture the standard
model, but it says nothing about gravity
or dark matter. Nor does it explain why
gravity is so weak that you overcome the
pull of an entire planet every time you pick
up a glass of water.Smashing physics
Hints to these mysteries were meant to have
come from the flagship experiment of physics,
the Large Hadron Collider (LHC) near Geneva,
Switzerland. Historically, building machines
that smash particles together at ever higher
energies has always led to discoveries. Many
in the field were convinced the LHC would
follow suit by turning up evidence for
supersymmetry, an elegant idea that would
solve pretty much everything, including
the mystery of dark matter, by introducing a
heavy twin for every known particle. It hasn’t
worked out that way, leading some to question
the way we craft such conjectures – and others
to demand an even bigger collider.
But even back when the LHC promised the
universe, Arvanitaki had other ideas. “We kind
of knew, as young people, that most of the
good ideas about what it might find were
already worked out,” she says. “We didn’t want
to just regurgitate stuff.” So Arvanitaki, then
a graduate student at Stanford University inCalifornia, started sniffing around entities
proposed by physics that couldn’t possibly
be revealed at a collider.
She was drawn to axions, hypothetical
particles suggested in the 1970s to solve a
mystery known as the charge-parity problem.
Ultralight, they have no electrical charge but
generate an entirely new force. They are a
good candidate for dark matter. The trouble
was, the force they carry would interact so
weakly with other particles that they would
never show up at the LHC. That might explain
why axions fell out of favour – that and the fact
that heavyweight particles emerged naturally
from supersymmetry, encouraging everyone
to build elaborate underground detectors to
try to flush them out.
In 2010, however, Arvanitaki and her
colleagues found a way to resurrect axions
by throwing string theory into the mix.
Some versions of this complete – albeit
completely untested – theory of natureThe black hole
whisperer
Asimina Arvanitaki is in pursuit of planet-sized
particles and a gigantic dark-matter beacon.
Daniel Cossins meets her
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