… my current vision can change,
and be different in 2 weeks…
We are in a quantum Universe
and in quantum mechanics
observers disrupt the measurements,
so we live in a quantum Universe,
at one point we make observations,
this is today, and then we observe
a classical Universe. We can define
all things in this classical Universe
as if they had a history,
this is the Big Bang model; but unlike
the usual point of view of people,
we somehow reveal this classical Universe.
I am Pierre Binétruy, a particle theorist,
interested in the application of theories
of the infinitely small to the physics
of the infinitely large and the cosmos;
I am Director of the APC Laboratory,
which works precisely on this interface and
I am teaching at Paris Diderot University.
The vacuum, it is a whole
that doesn't look like much
Already from an early age
I must have been 10 years old
and he was 13,
and we spoke about this our entire life.
We were in our small bedroom
in Fontenay aux Rose,
and I must have upset him,
I don't remember why,
then I got upset too…
I grabbed a slipper and threw it
with full force; he caught it in the face.
I thought,  “Oops! This is bad,
he never gets angry but…”
Then he picked up the slipper,
threw it violently at me … I stooped…
and he broke the window.
My parents arrived:
“What is going on here?
Who broke this window?”
So, I did not say anything, since I stood
against the window it could not be me.
They looked at Pierre “Pierre! You?!!!”
He had all his education
at Lakanal and I followed
3 years later, and he was
consistently good in all academic
disciplines. And from there,
he integrated, almost quietly,
in Saint Cloud; quietly, yes and no,
because he has at least one bad memory.
He doesn't look like it but
he is extremely obstinate. In an interview,
you are supposed to solve
a given problem and to try being nice
with the educator grading you.
But Pierre was not like that.
The teacher told him “Ah Binétruy,
it is ending with a Y, you are Basque”.
Pierre answered “not at all!
My family is from the Jura department”.
The jousting lasted almost 20 mn
and ended with a 3/20
or 4/20 grade, I think.
A constant mental surge
My oldest memories with
Pierre, Louis and I, are from
the school year 1973-1974
we spent in Saint Louis
in Math Spé P' as it was called,
so with courses specialized
in Physics and Chemistry
with M. Fleury. I recall Pierre then,
with his quite remarkable hairstyle,
which we could qualify as “Afro”,
spherical as we can see on past pictures.
Summer 1975, we went together,
I was driving… to take part in protests
in Larzac, against the Fontevraud
military camp. There were plenty of
well-known people, like Mouna.
We were looking for Cabu
who was also protesting there,
but we could not find him.
Everything accelerates
Being accepted at CERN
opened up many unsuspected horizons.
Being at Normale Sup and taking classes
in Orsay, he knew well what to expect
as a researcher in a large French laboratory,
but he had no clue that he would face
all the superstars in particle physics.
At CERN he met Mary K. Gaillard
who later directed his thesis,
and who pushed him a lot.
This is how he went to Berkeley
for a while and made connections
with American and international
researchers. Indeed, CERN
was an environment in which
he felt comfortable. He was facing
different cultures and scientists
who were thinking differently
about physics, watching all those people
with blissful eyes.
But it is where he started being
really attracted and what kept him
moving forward in all his explorations.
Value doesn't wait for the number of years
At the end of 1970's he came to me
at CERN to get a project.
I did not understand exactly what it was,
and I thought I had to give him
a doctoral thesis. Actually, it should have been
something smaller, but I gave him the thesis topic
and he did it without knowing what it was
and we wrote our first paper together.
Then I accepted him for a State Doctorate.
Ecole Normale had proposed someone else
to me, but I thought Pierre
was better, and the whole story…
His thesis, he essentially did it alone.
It was on the effects of the renormalization
group on strong interactions and based
on works he had done himself and also
with a student from Geneva University.
We wrote about 20 papers together
on primordial Universe physics,
supersymmetry, supergravity,
and then string theory phenomenology.
We found a way to stabilize the dilaton
with interesting consequences
for particle physics and cosmology.
Mary K. Gaillard, his adviser that I knew
for a long time, taught him essentially
what we call phenomenology
but directly applied from fundamental data.
It was his main strength.
 He did not like pure theoretical or
phenomenological physics, he was in between.
He understood actually that
from a scientific point of view,
cosmology and astrophysics
were becoming increasingly important.
I first met Pierre in 1997 during my DEA
as he was my quantum field theory teacher;
he taught me that through each
mathematical equation there is
a fundamental principle that we must
uncover in order to progress
and his pedagogy was exceptional.
I also worked with him between 2001
and 2003 in Paris 11 & Paris 7 Universities.
We worked on dark matter in
supergravity models and he showed me
the model building and how from fundamental
principles we can build coherent particle
physics models. As well as during my career,
I also knew Pierre during my private life.
Each time I noticed that there was
a dynamic in his life, which was his passion
for physics; physics and fundamental laws.
Fundamental laws of physics that are
driven by four interactions: gravity,
electromagnetism, weak nuclear force
and strong nuclear force.
The vacuum, the denied nothingness
If dark energy is vacuum energy,
we are at the crossroad between
the two large theories developed
by physicists during the 20st century.
On one side, the theory of the infinitely
small, quantum theory, and on the other,
the theory of the infinitely large,
the Universe in its largest dimensions,
Einstein's theory, general relativity theory.
So dark energy, vacuum energy,
would bridge those two theories,
and give precious information
on the ultimate unifying theory
which is the dream of every physicist.
I know that it is a complex notion,
particularly for occidental people.
In oriental philosophies,
 vacuum is a more elaborated notion.
I will take the example of the Zen garden.
A dry Zen garden with a layer of raked gravel
and few standing structures.
So you can imagine the structures
as the states above the vacuum and
the gravel layer with its fluctuations
created by the rake, this would represent
the quantum vacuum.
Pierre, if I tell you General Relativity?
Einstein Theory
Black Hole horizon? The no-return point
Vacuum energy?
We are the children of the vacuum energy!
Yes, Marie Odile, you are the offspring
of vacuum energy! This is great news!
Great news, indeed!
I didn't give the correct answer???
I remember very well
when I saw the first hands
Everyone remembers seeing his first hands
It was rue Charlemagne, on the wall of the
Philip August's rampart
A couple was standing in front of it, still,
And this immobility caught my attention
On the wall, some chalk drawings
One needed a few moments
to identify a hand
Perhaps because this hand
called on all hands
At the same time young and worn,
Restless and detached,
offering and rejecting,
Prayer and scream, worried and nonchalant,
I remained for a long moment contemplating this hand
The couple was gone
How strange that few chalk lines
drawn on an old wall
Could stir emotions hidden deep within
As an ancient music or a forgotten flavour
A primitive magma was agitated
releasing sensitivity bubbles
Alternatively comforting, inebriating,
disturbing or soothing,
The world reality reduced
in this draft of hands
A kind of primordial matrix
Symmetry is to space what rhythm is to time
Pierre had remarkable publications
with many citations in Cosmology.
He started with what was a scientific urgency
for everyone, supersymmetry,
the presence of dark matter,
and then he went, as everybody and I,
to cosmology and astroparticles.
There again, Pierre combined
"spirit and courage"; this means that
not only you need to have scientific visions
but also to organize the community to do it.
I think that when you look at his career,
what is quite remarkable is that he managed
to change research topics. He started
on formal fields like supersymmetry,
then cosmology, phenomenology and
later gravitation, astroparticles.
It is not easy to change like that
even though they are related fields,
this requires a significant investment,
and he did it.
I first met Pierre when I was in full
research activity and he was creating
the GDR SUSY, mingling astroparticles
physicist, astronomers, cosmologists,
and experimentalists, to share information
on supersymmetry. I discovered all facets
of this field regarding dark matter but also
the unification of forces, and I learnt
a lot with Pierre in a very convivial
ambiance, very rich on a scientific aspect,
animated and pleasant.
Both of us started in particle physics
and we went to cosmology and astrophysics
and I think it was a good choice.
First for physics, because we felt that
particle physics would saturate a little;
it had a lot of success with
the Standard Model that was working
very well, but data from experiments
were arriving slowly and we felt
that we were reaching limits.
He started with M. K. Gaillard on
unification theory and threshold
corrections, then supesymmety,
supergravity, and string theories,
in Annecy and Orsay. On supergravity
he collaborated strongly with G. Girardi
and R. Grimm, Pierre's very good friends.
So he had already very extensive activities,
several publications in cosmology and
astrophysics, and in astroparticles with P.Salvati.
I remember speaking in Annecy with
with P. Cerbat, who told me,
« Pierre? We never know what he is doing,
he works on ten different things all at once"
He was already like that at this time,
at this time, and that was Pierre's
first scientific life in high-energy physics.
Later in 1998-99 he totally changed
to gravitation, cosmology, astroparticles.
He anticipated astroparticles very early,
when I was still a doctoral student, he spoke
about this path he would like to explore.
He already had contacts with University
Paris 7 for the creation of APC, with
Luc Valentin in Orsay.
During my doctoral thesis, he launched
the GDR SUSY, whose goal was to form
phenomenologists. They are people
performing calculations, understanding
the theory and its consequences.
They make calculations on observables,
and they need to understand theory
but also to create codes to do that.
He was the first to launch that. As soon as
1997 he said, we need computer codes,
where you enter parameters and the model
and that gives you dark matter density,
particles service life, everything.
The first code was SuSpect, the one
I worked on, and SDK, which are still
used by Atlas people in CERN, and
calculate the supersymmetric particle
spectrum, disintegration mode, and
detection possibilities in accelerators.
Then, he launched Micromegas, which
is The Code in the whole world to calculate
dark matter density. But he was really
the first to say that; we need codes
to calculate observables in the
supersymmetric domain.
He was organizing with colleagues weekly
or every two weeks workshops on cosmology,
string theory, additional space dimensions
and their consequences for cosmology.
I found this very, very interesting,
because I had also started working
on cosmology and string theory,
from another angle. It was very interesting.
It was an opportunity for me
to decide using my Chair in Orsay
because he was one of the persons
I interacted the most with.
I have a very clear memory that he did
very important things, because he was
the first using additional space dimensions
to modify equations in cosmology.
He introduced the concept of what
he called, black radiation. It is like
an additional term in the cosmological
equations deduced from additional space
dimensions, hidden ones. I think he called
that black radiation, neither the matter,
nor the energy, but the radiation.
Does it tickle or does it scratch?
He immediately started in particle physics
with things related to phenomenology of
particles, gauge theory and things like that,
and he knew to direct his research
while he evolved, providing him
with new subjects…
Let say,
we shared what I call
jubilatory anxiousness;
it is roughly what holds a researcher.
Here, there is a stressful problem;
however I will only go there if it is jubilant to do so,
somewhat to piss off everybody.
So we shared that, and he changed
research topics when he thought one
was a little exhausted, and another
was more promising. Notably, you know it,
 he finished on issues like quantum gravity,
a topic that we are far from ending
discussing about because we are far
from quantum gravity.
We are stressed out not having a solution,
but it is jubilant because working on that
will take time but it is rewarding
and brings euphoria.
So, Pierre was far-sighted; he had this ability
to convince people to work on things
that will not provide them publications,
and that they eventually will not see.
Pierre saw gravitational waves;
and sadly he will not see LISA,
but what people will do with LISA
will have a lot to his vision.
So he was a civilized man.
He had goals, he was ambitious,
but in my opinion a good way.
Some are ambitious
by jostling for position;
others are ambitious to improve things.
Delight was one of the fundamental forces of being, like gravity.
As early as supersymmetry and
the creation of APC, besides fields like
cosmology, particle physics, astronomy,
theorists and experimenters,
Pierre Binétruy added his touch,
with gravitation and gravitational waves.
This has been a constant, as soon as
the GRD SUSY, this vision, getting involved in VIRGO
he had the vision for the future
with spatial research and especially
the LISA project in which he invested a lot.
This is a booming project with the recent
results on gravitational waves.
He even gave a scientific contribution there,
trying to connect supersymmetry and
GW detection and showing that
in many scenarios, supersymmetry
in the Universe history could have left
its imprint in the gravitational background
filling the Universe, rather like the creation
of atoms in the Universe left a background
on the electromagnetic radiations coming
from the primordial Universe.
Like as the waves make towards the pebbl'd shore
He was also interested in the models
of high-energy physics for inflation
and inflation models predict a signal
for gravitational waves for example.
He probably anticipated it in publishing
the first edition of his book on
gravitational waves, a few months before
the discovery, which is very mighty.
I think that gravity is really the engine
of the Universe in its largest dimensions,
so it is extremely important to detect the GW
and to watch the Universe through them.
As I told you, we are probably biased
because we are made of protons, neutrons
and electrons; we are sensitive to
the visible light so our conception of
the Universe constructed for thousand
of years on the luminous Universe.
We are now discovering that
the non-luminous Universe is the essential part
and that our vision of the Universe
is perhaps biased because of that.
So, it is extremely important to see,
for example, the gravitational Universe
and the best way to see it is with the GW.
He rapidly understood that for GW
we would need going into space.
In 2005, there was no interest in France
for GW into space, but he thought that
it was an opportunity. I was IN2P3 Deputy Director,
he told me that he wanted to meet
Stefano Vitale from LISA and
Bonneville from CNES to try pushing that.
 I must say that I didn't believe in it at the time,
I believed in GW but I thought that GW into space
that was a bit far. But it wasn't Pierre's idea.
And he was right.
Everybody knew that GW was a difficult
project. Indeed starting a spatial project
while we had not yet detected GW
on the ground was difficult. We headed towards
very new things and he belongs to those
who made a crucial contribution,
because he presided the Fundamental Physics
Group but he also presided the group
that built the Cosmic Vision program,
which started these projects.
The strength of Pierre was his ability
to see the opportunities with GW,
from  ground to space.
He didn't work on ground detection
but he strongly supported research
with Virgo and Ligo and he pushed research
with Lisa to get the whole range of sources,
from astrophysical sources
(Neutron stars and black holes)
up to supermassive black holes and cosmology.
It is rather like throwing a stone in water,
there are ripples forming.
These will be ripples deforming space-time
and propagating into the whole Universe.
This is what we study with GW.
The ultimate goal being to collect
information on what happened just after
the Big Bang when there was also production
of primordial GW, and then we can reach,
not just 400.000 years after the Big Bang
as we do with photons, but really just after it,
when those primordial GW were produced.
The horizon of the black hole is the surface,
a spherical surface, surrounding the black hole;
once we cross it, there is no coming back,
 it is the surface of no-return.
Inside the black hole,
there is the singularity, quantum mode, etc,
outside the black hole there is the black hole
gravitation. We are at the interface
between gravitation and the quantum mode.
I am convinced that it is at the horizon that
we will understand and see signs of what
unifies gravitation and quantum theory.
A horizon is a border between the known
and the unknown. We have difficulties
conceiving an infinite Universe,
so the horizon is what is limiting our
observable Universe within an infinite Universe.
It allows us to reconcile with the notion of infinity.
A spoon of gravitation, three pinches of relativity, a zest of quantum, blend all the ingredients!
He was a pioneer in astroparticles.
He founded the APC laboratory that
he directed for a long time, and
this laboratory unites experimentalists
and theorists, in perfect symbiosis
to discuss these questions. He was
a tireless facilitator. Notably, he was also
President and member of numerous ESA
committees, facilitator of the European
research group on supersymmetry,
French P.I. for LISA, this huge project
aimed at placing in orbit an interferometer
to detect GW into space. So he played
an important role by his contributions,
his sense of organization, and his leadership
in the field of astroparticles.
I met Pierre Binétruy repeatedly in the early
2000s when I joined him to create a new
revolutionary laboratory that became
the APC. We met here in Collège de France
and it is where I measured the scope
of Pierre's qualities, because he had to face
a triple challenge, particularly in the French
context. First he had astrophysicists,
particle physicists and theoreticians
working together. He also had engineers,
technicians and administrative people
operating together. And finally, he united
three French institutions that were not used
to working together, University, CEA and CNRS.
Assembling all that was an extraordinary challenge.
I worked with him for 12 to13 years.
He was very demanding, however
the benefit of having someone like him
is that we always tried to be up to
his expectancies. So I tried to meet
his expectations that were high. He was
creating a laboratory; it was gaining momentum
and starting space-based research
with high stakes.
On the international scale for example,
he presided the ESA thematic group on
fundamental physics and there, he had also
an important part. In the spatial field he had
an essential role in the ESA big project,
which is the Lisa project on GW, to get
France ready to play an important role,
particularly in the data analysis.
I think that he played a valuable role
in organising and administrating research
in France. One of his main qualities was
his ability to attract people and have them
working together. He pushed them
to do things that they wouldn't have done
if he didn't come to them. This “bonding”
dimension that expressed in varied ways
but is a very important aspect in research.
Pierre was creating the APC. So being
postdoc with Pierre was not easy because
you didn't see him a lot, but when
he is building a laboratory… I recall discussions
about bathroom pipes, heating system,
thermal isolation; he had these kinds
of problems to solve with maps …
I was fascinated by his memory.
He had a colossal memory. Had we interrupted
a work a month before, he could resume
where we stopped and remember
the exact problems we encountered.
He let me totally free on the program;
 he gave me directions;
“go there, it is the trend!”
He had prescience; he knew where
the scientific community would go.
It is the same with Randall-Sundrum
models, in 2002; he was the first to present them
to the GDR, and everybody was awed.
E. Dudas worked and published on that.
 Additional dimensions then. Pierre understood at once.
Brane cosmology, with C. Defayet, Pierre understood.
 Phenomenology of supersymmetry, he understood.
Dark matter in supergravity models, it's also him.
And lastly gravitational waves with LISA
He was always farsighted.
Art is aimed at disturbing, science at appeasing.
As he wrote it “The coherence of the artistic
approach made these striking shortcuts
possible, where a connection that
we, scientists have slowly worked out
is naturally established in an intuition of
the emotion or simply of the body.
How can the quantum vacuum be represented?
This was the question asked
by Marie-Odile Monchicourt during
Origins' preparation, a performance
focused precisely on the quantum vacuum.
We physicists had great difficulty
characterizing the quantum vacuum, and
extracting ourselves from our predefined
schemes to give a vision of this vacuum.
Meanwhile, through the rehearsals,
a metallic structure appeared on the stage
all in a breakdown of symmetries.
The dancers-acrobats took ownership
of this structure, expressing with their gestures
the domination of gravity.”
“Elena Asins' times are multiple.
Alternating times from vacuum
to wholeness. Complex and fractal rhythms
where the volume must strip off and almost
disappear to rebuild itself, as the wave
annihilates to generate the next one.
An immutable process in its diversity.”
As we say in physics he was
multi-dimensional. I saw some of them,
not all of them.
He told me this on several occasions.
When arriving to give his lecture,
and waiting for his students to come,
several students would enter and ask him
“but when is the teacher arriving?”
That happened several times.
I recall Pierre at the first lecture; the whole
class was waiting for him. I knew him since
he was my professor two years earlier.
Everybody was surprised to see such
a young person. Because he was young
but he looked even younger than he was.
He sounded almost like us, not really older.
We were 22 or 23 years old and he seemed
to be 30. It was surprising.
It's my turn to tell an anecdote. It was
the day of the press conference for the GW
discovery; there was an exhilarating spirit
in the Lab. We met later and we realized
that we finally could test general relativity.
We had the masses of the coalescing black
hole, so we could test the Hawking's area
theorem. So each of us on our computer
we calculated using squared masses,
and we realized that it was working.
So Pierre, delighted, took his phone
and shouted “Stephen! We verified your theorem, it's fine!”.
About the paper I published alone,
he told me that I had done most of the work
so it would be good for me to publish it alone.
That shows what kind of person he has been.
Very generous and honest.
Some teachers would add their name on
papers even if they didn't do anything;
in his case, he effectively did some work
but told me to publish it alone.
The last time we met was in December just
before I left. We had a leaving drink and
I thanked everyone and also Pierre for
the time we spent together, his teaching and
his patience with me even when
I talked nonsense at first.
And he just replied with a question
“will you remember that with your own students?”
As Pierre's PhD student I can tell that
he was always patient, but also demanding
and rigorous. He was never in a rush;
he never validated something before
taking time to verify. He was patient and
never patronizing, never.
It was sometimes difficult to find him.
But when he was there, he was very
focused on the project, asking exactly
the right questions. Yes, sometimes,
it is not answering a problem that is
important, and Pierre knew exactly
how to ask questions.
My most vivid souvenirs with Pierre are
unplanned appointments that we had.
He would come in this office, late in the day,
saying, “right now I have time,
anything we could discuss about?”
He introduced me to some of his students,
starting with Emilian and Stéphane.
I noticed that his students were part
of his family. They were always invited,
we always spoke together and it was
very friendly. The “Binétruy Group”
was very relaxed. But when we talked about
physics it wasn't so relaxed! Which is right.
Plant a tree; write a book; you will be a man
I learned a lot from his book on
supersymmetry. I received the schema
of this book from Oxford University Press
editors, who wanted my opinion.
I long sought for a good book on
Supersymmetry that would suit my teaching,
and Pierre's book seemed perfect.
However it took him many years to finish it.
So I was teaching from his manuscript,
he would send me chapters time to time,
and I was returning him corrections.
To this day, the first task I give
to my PhD students is to read Pierre's book
because I think it is exceptional.
For example, Pierre's book on
supersymmetry is full of theoretical boxes.
It is a book for informed people
but it presents a lot of possibilities,
it is very encyclopaedic,
which is exactly as Pierre was.
This search for gravitational waves
that was animating him,
he wrote it in a book for general public,
that is in my view an excellent one,
because we get simultaneously
Pierre's rigor and scientific refinement
and his ability to reach broad public
with his own way to communicate.
Many people certainly said that, but what
personally struck me was his intelligence,
coming from his entire being, his way
of speaking, and his quickness of mind.
It is why I liked very much working for him.
But it was also a form of modesty
that he had, kindness. After all that time,
he is the researcher who impressed me
 the most during my CNRS career.
Today, science is certainly missing him a lot,
 but research institutes are also missing
people like him. Men with such vision
are missing a lot. And I miss him.
I think that he always kept some
childishness. Occasionally he would
become enthusiastic about something,
then he had a large smile and we could see
his juvenile euphoria emerging.
I always found this very moving;
and I am moved.
We met because he had mentioned an idea.
I think he defined it himself, as slightly
crazy and he wanted to test it on me.
I think indeed it was a wild idea.
In this last discussion, I felt that he had
less than usual both feet on the ground.
As if he were trying to fly very high.
The first sounds of space
Were retrospectively given
The name « mother ».
Ma, also known as « the radio ».
Now I can no longer
Listen to you, the radio switches on
Inside me.
Fear of a form
Of silence
I fill like a voice of arabesques
Training myself
In other languages, my own language.
Like the kids who cover
Walls with drawings and fill them up
Completely with colours / twitterings,
That pass themselves off as figuration
when what they are is
Illustrations of saturation
In which you can search for the point, the tiny hole,
The breach you can pass through
To the other side like a player in a game
To wherever your desire takes you.
And I think of my friend Pierre.
