those of you who follow us on twitter or
facebook might know that our very own
professor ed copeland recently won a
prestigious medal from the institute of
physics
now we're all really pleased it was a
great excuse to go and have a night out
and amazingly see professor moriarty in
a uh
bow tie something you don't see every
day professor edmund copeland of the
university of nottingham
but here at 60 symbols of course we're
especially happy for professor copeland
now his win has nothing at all to do
with 60 symbols he's won it for his own
research into three areas
cosmic strings and super strings
inflation that's not the financial type
of course we're talking on a cosmic
scale here
and dark energy so we're going to post
three videos one on each area of
research and i really let ed off the
leash a bit here so he's going to be
talking for quite a while but i know a
lot of you always say you want to hear
more from the professors so here you go
here's the first of three videos with ed
and this one
is cosmic strings and super strings
you know when they announced the nobel
prize
and
they announced it to higgs and anglair
who quite rightly received the prize
and they didn't give it to kibble
which
upset me partly because tom's a good
friend
but also i think he probably deserved it
as much as they did
and so i tweeted a few minutes later and
i said
you know congratulations to higgs
nonglei fully deserved i
feel sorry for tom and what we now need
to do is go and find cosmic strings so
he can get his own nobel prize
because tom kibble came up with the idea
of cosmic strings
back in 1976
these wonderful objects
first of all you need a real imagination
to come up with these kind of things
they're related to the higgs field they
they are made up
of what we could call the higgs field
but just at a completely different
energy
so cosmic strings are
examples of something called a
topological defect these are objects
that
formed in the ver may have formed in the
very early universe there's no evidence
yet of their existence
and
they're incredible they're amazing
objects and so i'll just try and
describe give you an idea of them
they're their strengths their thickness
is much much smaller than a proton okay
so you've no chance of seeing them but
they can be as long as the observable
universe
moreover
if you had about a kilometer of such a
string
it would have the mass of the earth
so there is much thinner than a proton
but there the the mass of the object so
the energy stored in the objects would
be of a kilometer of them would be about
that of the earth
and they could they formed um these
particular ones would have formed within
the first 10 to the minus 35 seconds
after the big bang you just need quite
an imagination to think about these
things
and they formed in the first transitions
just as we've been hearing about the
higgs field undergoes phase transitions
and as it undergoes this transition
where it changes from one state to
another state it can give masses to the
particles in this particular case what
happens is the the equivalent field but
at a much higher energy as it changes
from one high energy state to another
under a phase transition throughout the
universe this doesn't happen all
smoothly
and
there are various parts of the universe
where it where a bit of the original
high energy bit gets trapped
and these are formed the lines these
long strings so that the strings are the
original high energy bit that was before
the phase transition and the surrounded
by the new phase which is at a lower
energy and once they're formed you have
a you have a network of these long
strings crossing across the universe and
loops of string
and then they're because they're so
massive and under so much tension
they begin to flop around
and as they flop around moving at close
to the speed of light or about half the
speed of light
they begin to cross one another
so you imagine a long piece of string
like a shoelace okay imagine a shoelace
and you as it wraps back and crosses
itself well with a shoelace you can't do
anything it just can't go through itself
but with a cosmic string they can it can
chop off
at that point where where a piece of
string crosses itself
then at the junction where they've
crossed it will break these loops of
string now are under a huge tension
remember a kilometer is about the mass
of the earth
they're oscillating around they're
moving close to the of you know a good
fraction of the speed of light
and because they're moving and
oscillating they radiate they radiate
gravitational waves
just like any massive object that moves
will radiate gravitational waves
and that's its principle way of losing
energy
because the if they didn't do that what
would happen is the long strings would
just keep stretching as the universe
expands it's be like pulling an elastic
band and the energy stored in these long
strings would get bigger and bigger and
bigger
and eventually they would come to
totally dominate all the other
contributions to the energy in the
universe and it would completely change
the dynamics of the universe so that
doesn't happen we've
we've not seen any
so that either they're not there or
something else has happened which has
meant they don't dominate and the thing
that we think happens is that because
these lung strings can form loops and
these loops can then radiate their
energy in gravitational waves
then they can reach what we call a
stable scaling solution where the energy
stored in the strings becomes a constant
fraction of the total energy so it never
comes to dominate the energy in the
strings doesn't disappear it doesn't
grow and become too big it just becomes
like the goldilocks amount of energy is
just right
and that was what got people very
excited when tom kibble first came up
with this amazing idea of the formation
of these objects
he demonstrated that when they evolve
under the expansion of the universe that
they would chop off these loops and they
would radiate away their energy in just
the right amount so that the overall
energy of this network of strings
would be
some fixed fraction of the background
energy
now it turns out you can work out what
that fixed fraction is
and it and you you find that for for um
phase transitions which correspond to
what we call the grand unified phase
transition that's where we unify
the strong the electro weak and the
electromagnetic forces this is about 10
to the minus 35 seconds after the big
bang
that the energy scale associated with
that which determines the masses of
these strings
that is just sufficient
to lead to the fluctuations in the
matter that produces
the cosmic microwave background
radiation
and the distribution of galaxies this
was what
it seemed to be the case back in the
1970s and early 1980s that cosmic
strings provided the seeds from which
structures would form
so people so now we had
a theory which was rivaling another
theory called the inflationary universe
but they were competing with one another
unfortunately
about the time i started working on
these theories
um
they the
evidence from the cosmic microwave
background was coming in and it was
getting better and better more accurate
you could you could see the fluctuations
in the temperature of the microwave
background and all different sizes
across the across the the universe the
observable universe
and you could begin to fit your
predictions from cosmic strings with
what you observed in terms of what this
distribution should be
and you found cos and it was found that
cosmic strings just weren't working they
were not matching the observed cosmic
microwave background on isotropics
and so people began to lose interest
these wonderful objects that could well
have formed in the early universe and i
should say
that the analog objects that have been
observed in condensed matter systems
they're observed in liquid helium
systems they're observed in systems with
pneumatic liquid crystals the scaling
properties are all seen and match what
you might expect from cosmology it's
just that they've not been seen yet in
cosmology
so back in the at the turn of the at the
end of the 1990s beginning of 2000s
people began to lose interest in these
objects because
they were not doing what they were it
said on the tin in particular when you
look at the observed map
and look at the
power in the map as a function if you
like of the of the angle of the sky that
you're looking at it's got a very
distinctive set of peaks and troughs
they're called the doppler peaks and
troughs when you compare that with what
the prediction is from cosmic strings
basically the cosmic strings would give
you one peak
and and not the secondary peaks not the
secondary doppler peaks
i carried on because i was interested in
some other features um
there are some
as i mentioned just a few few minutes
ago the they're there are condensed
matter systems which demonstrate these
and and in fact there are a number of
condensed matter systems which are
driven by loops or vertices loops
um of effectively of strings and and
there's a
particular thing called the vinyn
equation which which is used a lot in
helium and no one's really been able to
derive that equation from first
principles and i think there's a way of
doing it from the work we did and so
that was something i carried on working
on and still am thinking about with tom
and danny steer um
but basically the idea of using strings
in cosmology yeah we i stopped thinking
about that for a little while and it
wasn't until about 2002
when i was uh in fact early 2003 i went
to a
a meeting in santa barbara
one of the perks of working in this
field
and when i was there i got chatting to a
few people who who were thinking about a
different type of string they were
thinking about what we might call
fundamental strings or the super strings
of string theory
back in the 1980s
people were working on that and in fact
probably the most brilliant theoretical
physicist alive today ed whitton had had
asked the obvious question if you have
cosmic strings and if you have these
fundamental strings maybe they're the
same thing
and he'd come to the conclusion they
couldn't be
basically um the fundamental string
turned out to be very unstable if you if
so if you formed a string that was you
know the size of a galaxy then a
fundamental string would just want to
chop up incredibly quickly
um he also discovered that if you
if you looked at what the natural value
was for this mass of the fundamental
string it was way too big compared to
what observations were telling you the
cosmic string could be
and so there were these reasons why you
know the instability the fact that the
masses didn't work out which meant the
the feeling was they weren't going to
work
but in the early 90s there was a kind of
a string revolution a second string
revolution in which it was realized
there was a new class of objects could
form
and these new class of objects in those
new class of objects these strings could
actually be stable these are the these
are these cosmic strings or normal
strings normal strings that the normal
strings which we thought were unstable
could be stable
or at least live
way longer than the age of the universe
and that they could have a tension or a
mass per unit length much lower than
whitton had thought
and it opened up the possibility that
actually maybe these strings could be
like the cosmic strings
and what we and they became known as
cosmic super strings and so i i was
involved in some work uh looking at that
and that was one of the papers which
sort of
rejuvenated the subject in that a lot of
the string theory people began to get it
excited
not least because it had some unusual
properties these cosmic super strings it
they could come in different flavors
so that now when
let's call it an orange flavor and a
yellow flavor if they came together they
wouldn't simply pass through one another
they couldn't because they they had
their various colors and they couldn't
simply chop
and go and
connect the orange with the yellow you
they'd have to form a composite in
between so you you ended up with the
position where these strings would no
longer form simple loops but they'd form
what you call junctions three-way
junctions
so two strings would come in
and they'd they'd hit each other and at
the point where they'd hit each other
they'd have to be a new bridge would
evolve out and so this led to these more
complicated networks which i and others
have begu have been have been analyzing
and thinking about and we're and we're
looking at the possibility that these
objects could actually be seen
not both in the microwave background
but also
if you remember i said the primary decay
route of strings is through
gravitational waves
these strings and cosmic strings
have some wonderful properties on them
for example when you have a loop of
string and i'm getting to the decay of
the strings now and how we might find
them
so if you have a looper string that's
oscillating and backwards and forwards
then
every now and again once in an
oscillation usually it will there'll be
a part of the string which forms what's
known as a cusp
this cusp is a very kind of a sharp
region
which goes at the speed of light
instantaneously goes at the speed of
light and because it's so sharp it's got
so much
energy packed into this region it can
emit bursts of gravitational waves
and so there are detectors out there
there's the ligo detector and then
they're upgrading it to the advanced
ligo detector
which are searching for these
so these you would get these beaming
events coming out from the strings
and a number of us have been working on
the properties of these beaming events
and you know so that to see whether or
not they could be detected by the these
gravitational wave detectors and it's
one of the main things these
gravitational wave detectors will be
looking for the beams of gravity beams
of gravity yeah shooting out from these
objects and they because they're they're
they are so sharp they don't just beam
gravitational waves they can beam other
things they can beam particles out and
so they're just it's just like the
ultimate laser this can boom
and the the neat thing is it's not doing
it all the time it's it's doing it once
a cycle you know it just goes beaming
and beams and beams and so you have this
sort of pulsing effect that you can
begin to look for it's a distinctive
signature so you have those and then you
have other features on these strings
which are called kinks so every time a
string
chops
chops off and chops a loop off it leaves
this discontinuity where one string has
come in and it's met the other string
and where they've met and a loop has has
gone off you're left with this sort of
discontinuity the string one string here
and the other string there and that then
begins to propagate around
the configuration and you just get a
build up of these kinks which also
radiate
and so you get these extra beaming
effects from these objects as well we're
just making this stuff up it's just
great isn't it so one of the things
you're trying to do is understand the
distribution of these things and then
the amount of radiation the rate at
which they'll come off
and of course we've not seen it
so this could be the bit that's totally
made up but
one way of interpreting something that
you don't see isn't that the object's
not there it's telling you about what
that mass scale can be you know if the
it's just getting lower and lower and
lower
if if the mass scale of the strings was
high enough the tension in the strings
was high enough they'd beam more
energetically and we would have seen
them so the fact we haven't seen them
one interpretation is the mass scale is
dropping down and that is so in fact
they're dropping down so that they're
getting difficult to reconcile with
grand unified theories the typical grand
unified theories but then
they are consistent with some of these
cosmic super string models those are
still perfectly plausible
if the cosmic micro background
isn't helping the cause at the moment it
isn't matching
they're not finding these gravity lasers
these these waves you're not finding any
of the evidence and in fact some of the
evidence is going against the idea
what makes you keep the faith
well no the first thing is it's such a
beautiful idea
the idea of a first transition is is
well accepted in in particle physics
the higgs mechanism is a phase
transition
and and and
the breaking of a symmetry which is what
is going on here
is is well accepted and and so the
the
the fact that these objects are seen in
equivalent systems
terrestrial systems is sort of evidence
that the the ideas work
now
there's no reason why that i'm aware of
that this
shouldn't be allowed to happen in the
early universe but we don't know if it
did happen
we know phase transitions happened or we
believe that they occurred whether or
not they occurred in such a way that
they produce these objects and there are
two more three more types of defects by
the way i should just give them
a name check which is monopoles
domain walls and textures
these could have all formed and in fact
the monopoles is one of the reasons why
people came up with the idea of
inflation
which we'll maybe touch on in a
different video so it's the fact i think
that these things are so so natural in
the sense of face transitions are
expected to have played a major role in
the universe early universe that makes
me think we should be looking for them
and the fact that we don't see them yet
i still interpret as more of a bound on
the strings rather than hell this is
clearly evidence this didn't happen it
may not have happened and eventually
when it becomes clear that the detectors
just have no chance of seeing these
objects then i think it's time probably
to to move on but that's not at that
stage yet and in fact planck
is currently looking at its second
year of data and one of the things that
it will be looking for are what is known
as polarization effect that's where the
the the radiation emitted gets polarized
by the presence of objects and cosmic
strings
can do that it can polarize the light
and so
um there are things called b modes which
is a particular type of polarized light
to do with magnetic fields
that cosmic strings
will pre they'll produce a particular
signal and that's something that i'm
working on
with regard to both cosmic strings and
cosmic superstrings and with people here
at nottingham
trying to make a prediction of what that
signal should be so that we can see if
it's there in the planck
data or not it probably won't be but you
never know how abundant are they are
they are they one of those things where
there's a million of them in the room or
there are they like these great ribbons
in space that you wouldn't want to cut
through because they'll chop you in so
that's a really important question and
and so the long strings that there are
two types right there's there's the
strings which stretch across the
observable universe
there will be of order
a dozen maybe 20 30 that kind of figure
for the the density of them
and but the but the loops of string
there are billions
there are billions in fact the majority
of the energy in the strings
are in loops because these long strings
chop themselves up into into loops these
loops then gradually decay but the
majority of loops that are formed
are chopped off you know around the size
of the observable universe at that time
and then so they take a long time to
decay and they're being chopped off all
the time so you've constantly
replenishing these loops they'll a whole
group will have decayed but there'll be
a whole group still decaying and then a
new group beginning and where are the
new ones being chopped off from from the
big giant 30
uh yeah from the from from those and
then from the big loops themselves which
are chopping themselves up and uh from
all of the you know all the other loops
will be chopping themselves up all the
time it's not a case of it's not
the majority of the loops
are self-intersecting in other words
they as they evolve they'll move in such
a way so if this is a loop
um it will it will move in such a
weather at some point in its evolution
it will chop and off will come two more
loops
and
most of the loops do that there's a
small subclass of them which are called
non-self-intersecting which are able to
evolve so as not to
chop themselves up and somehow come back
out again and then go back and come back
out without
without um
breaking up in fact in the early this
this is research and this is how
research goes when when strings were
first thought of as serious candidates
for structures one of the nicest results
that someone came up with in fact a guy
called neil churock came up with was he
he looked at the class of
non-self-intersecting loops and he he
realized that they kind of could could
match the distribution of clusters of
galaxies and he got this kind of nice
one-to-one map between the distribution
of these big loops and the distribution
of clusters and that was a very exciting
time because people thought oh wow these
you've clearly got evidence here of this
but then we began to realize that
actually the string dynamics worked
didn't work quite like that and that
that was a kind of a fluke and actually
the majority of the loops don't do that
at all they just break up very rapidly
if i was to
encounter one of these strings
especially one of these big 30 that
you've got me really intrigued by what
would happen i was thinking about that
today and
it
wouldn't be a great idea
i think is a fair thing to say because
one of the one of the things that
strings have they're so massive so
they've got this large string tension
and if they're moving
they will they affect mata moving around
it
in fact if you were to walk around a
straight string
um
then you might think you go from
zero degrees you walk all the way around
and you come back to 360 degrees with a
straight string that's not quite right
the string sort of
cuts out a bit of space so when you walk
around it it makes your space conical
and
so walking around a string you might
walk around maybe 350 degrees and you've
come back to where you've started and
what that effectively means is the
trajectories of objects going past the
string get bent
so this is one of the ways people think
about looking for looking for strings
you you look i'm coming to answer your
question by the way
um you get light coming by the strings
and will get bent and then when you
trace back that light it looks like
you've got double images and in fact one
of the distinctive signatures of strings
would be not that you get a pair of
double images because that happens all
the time but actually you'd get a line
of them because the string is a line
object and so if you're lucky you'll get
lots of these lensing and there have
been attempts to to find
such consecutive lensed events and
they've been found but they've turned
out not to be from strings but just to
be pure chance see these things are so
massive right and so mata when it goes
by it gets gets perturbed it gets shoved
in and that's why people thought that's
a scientific word shove it shoved in
that's why people thought strings would
be very good for structures because they
knew that as a string went past say a
distribution of matter
such would be the gravitational
pull around the string that the matter
would clump together
and then you've got your initial seeds
that you've got your initial
fluctuations which would allow other
matter to form around it and you get
wakes what i think will happen uh is so
when one of if one of these strings was
to say go through the earth which is the
light you're going through you
um
what it because it's you know you're not
going to see it first of all because
it's so infinite it's infinitesimally
thin it's about
weight i think it's about a trillion
times smaller than the size of a
hydrogen atom
so it will go straight through but it's
going through about point three or four
of the speed of light it's going through
pretty
going straight through but it will do
this effect right the matter the dense
material that the earth is made of will
get shoved in
it'll sort of get attracted behind the
string as a string as if it performing a
wake behind it
and the argument is
that i was and i was looking at the
calculations that what will actually
happen and in fact they're using this to
try and say maybe some of the
earthquakes on the earth is due to this
okay
this is the kind of imagination you need
um so the string goes through
the dense matter that's making up the
earth gets um attracted in behind the
string so and then it begins to bounce
it gets oscillates like this and they're
saying it could it could cause these the
ripples that you see as surface waves
that lead to earthquakes for you and i
it would probably be a bit more maybe
what i can't
figure out is whether i know it's going
to sort of tear us apart or whether
we're just going to sort of feel
you know pretty unpleasant for a few
minutes and then we carry on you talk
about them like they're real
yeah i do a bit that's that's a bit
sound in your head yeah in my head i i
happily will um think about them
evolving um chopping up i'll happily
think about how they might form
how i might test for them i spend a lot
of time trying to
because they're fanta if they're there
the goal at the end is fantastic right
if they're there
either as cosmic strings or as cosmic
super strings i mean you have a probe a
unique probe of the very earliest
moments of the universe that we just
can't get to without this kind of thing
so i think the goal at the end of it's
worth it and the the theory behind it is
so beautiful i mean what i don't know
how kibble did it i mean he's he is one
hell of a guy he just
he comes up with a higgs mechanism and
then he just thinks oh well now i'll
move on and i'll just discover
topological defects it
it it's just remarkable that he was able
to do this and and
they have driven so much research the
whole idea of these defects and and if
we do see them
then it really will be an amazing result
for the understanding the early universe
i think i'd be disappointed if we don't
see them but i you know certainly not
the end of the world
if they're not there and it's it's you
know
there's no evidence for them um yeah i'm
very happy to think about them and
work on them
i'll feel i've done some really fun
stuff just trying to understand objects
that had every right to be there there
was no reason why they shouldn't be
there in the sense of the dynamics
with which we think of them forming that
the process which we think of them
forming makes complete sense
it's it's just that the the the
particulars by which they would have
formed didn't happen that's just unlucky
and and yet the mathematics that we've
developed in understanding them and
um the the physical intuition we've
we've developed i think will has
probably played a role in other things
that i've been working on and other
people have been working on
no i'm if they're not there they're not
there and i'm not going to lose sleep
the very first thing i worked on was for
my phd were called kaluza klein theories
i worked on a subject called candelas
weinberg
which everyone got very excited about as
being a way of unifying the forces and
it didn't work
so
maybe people should take note of what
i'm working on and then move on to
something else quickly
just a reminder those other two
interviews with ed about inflation and
dark energy will be coming very soon
and congratulations again on the medal
brilliant