Meanwhile, at the Department of Physics @ Sapienza....

Random snapshots taken at the Department of Physics these days...love this place!

1) Perci & the Ciclofficina
Roberto Perciballi used to work as the priceless "factotum" of the Physics Department. He was in charge of essentially any repair, construction, moving, removal in the institute. Besides being a celebrity among students, he was also so on the stage as the frontman and singer of Bloody Riot, one of the first italian hardcore-punk bands. "Perci" suddenly died last March, leaving behind two daughters and the sorrow of many fans and friends.

The members of the student association "Ciclofficina" (named after Perciballi earlier this year) paid homage to him with this emotional and spectacular painting, showing a younger (and possibly punker) Roberto Perciballi. The painting features the end of a hallway (below on the right) that is offered by the Department to the student association. The poles have been installed after the recent earthquake in Central Italy which, although mild in Rome, also left some damage to the building.





2) Fidel & Majorana
These days, many all over the world are paying homage to the controversial figure of Fidel Castro. In fact, the whole Sapienza campus is upholstered with the poster below. However, how many can show off Fidel right next to Ettore Majorana's statue in front of the classroom named after him (below on the right)?




3) < Yes | No > & the Italian Constitutional Referendum
Tomorrow, Full Professors of Theoretical Physics Giovanni Bachelet and Giorgio Parisi will lead a discussion on the hottest topic in Italian politics nowadays: the Constitutional Referendum to be held next Sunday.

Prof. Bachelet is a former member of the Parliament and supporter of the constitutional reform. Prof. Parisi is the founder of the recent initiative "Salviamo la Ricerca" (see his recent letter to the Nature) and will defend his criticisms on the reform. I am looking forward to seeing how the physics community of our Department will react and will definitely attend the debate.

Recommended by us: IPN on Joe Weber

Segnialiamo un interessante articolo di Matteo Serra su International Physicists Network riguardo ai pionieri della ricerca delle onde gravitazionali:

Joe Weber e il suo rivelatore risonante di onde gravitazionali, leggi l'articolo completo
"Joe Weber: il pioniere della caccia alle onde gravitazionali" su IPN

International Physicists Network is born!

Great news! A new network of young physics researchers is born!

International Physicists Network (IPN) is a new italian no-profit organisation with the aim of building a national and international network of young physics researchers, and with the goal to create fruitful collaborations within different physics areas.

IPN has been founded by 11 researchers and professionals with a general background but multidisciplinary specialisation in physics: Davide Pietrobon (president), Marina Migliaccio (vice-president), Giordano Cattani (treasurer), Emanuela Pusceddu (secretary), Fabio Agostini, Claudia Antolini, Marco Di Stefano, Giacomo Fragione, Lorenzo Pagnanini, Matteo Serra and Francesco Stellato.

The main projects of IPN are the organisation of the Young Researcher Meeting, an yearly multidisciplinary conference aimed at students and young researcher in physics, with the goal to foster discussions and exchange of ideas in an informal atmosphere, and the Dandelion project (in collaboration with Find your doctor), a platform which allows to complement the traditional top-down approach to the job-market with an innovative bottom-up mechanism.

Laura and Nicola are Masters!

This week, my first two master students, Nicola Franchini and Laura Sberna, have defended their theses, and obtained a master degree (MSc in Astrophysics and in Physics, respectively) at Sapienza with maximum marks!

Nicola's thesis is entitled "Constraining Black Holes with Light Bosonic Hair Using Quasi-periodic Oscillations", whereas Laura's thesis is entitled "Early-Universe Cosmology in Einstein-scalar-Gauss-Bonnet Gravity"

Little time to celebrate for them: Laura is moving to the Perimeter Institute to start a PhD with Neil Turok, whereas Nicola is already at the University of Nottingham and just started a PhD with Thomas Sotiriou.
Kudos to them and good luck!

Celebrating Laura's "laurea" in front of the Physics Building "Edificio Marconi" at Sapienza. 
Elisa (on the left) is next on the line to finish her thesis.

NASA to rejoin forces with ESA to launch gravitational-wave space detector!

News was in the air since the LIGO discovery, but the 11th LISA symposium in Zürich made it official: after its dropout in 2011, NASA is ready to rejoin ESA in the effort to build the first gravitational-wave observatory on space. The effect of this dropout was not only to change the mission's name (from the original "LISA" to "eLISA") but also to drastically reduce its budget, resulting in a smaller apparatus and reduced science case.

The recent GW discovery has boosted this field and, after the announcement in February, it was immediately clear that the plan was to anticipate eLISA flight (initially tentatively scheduled around 2034). Now, it seems that eLISA could fly some years earlier (around 2030) and, most importantly, it will probably be build in its original LISA design, thanks to the joint effort of ESA and NASA.

eLISA is a triangular laser interferometer that will search for gravitational waves in space

After the LIGO/Virgo discovery, after the amazing success of the LISA Pathfinder, this is yet another great news for gravitational physics and science in general. Year 2016 will definitely be remembered as marking the birth of a new discipline.

Lectures on Gravitational Waves

This and next week I will be giving a series of lectures on "Gravitational Waves" at the Escola de Astrofísica e Gravitação (EAG8) at IST (Lisbon) and at the international school Invisible16 at SISSA (Trieste), respectively. The lectures at SISSA will be also recorded.

Some material related to the lectures (references, problems and notebooks) can be found here (this is still work in progress, since I am still preparing the problems and the Mathematica notebooks...)

The poster of EAG8

The poster of Invisible16

GR21 @ Columbia + Workshop @ Caltech

In academia, summer is the period to attend conferences and workshops, since the term is over (typically between May and June, depending on the country) and researchers do not have teaching duties at this time. 

This year I attended the GR21 Conference at Columbia University in NYC, the biggest event (organized every 3 years) that brings together scientists working in all aspects of General Relativity. 

I was not super happy with attending this conference, since the conference fee (~$600) and the cost of staying in NYC were much higher than usual (GR20 was held in Warsaw and conference fee was about half the price). However, in this very special and exciting year for General Relativity, I couldn't miss this conference. Attending it, in fact, turned out to be a very good choice: the conference was great, I had the chance to discuss with a lot of colleagues and I've particularly enjoyed the talks at the parallel sessions. I gave two talks, one presenting the recent work discussed here at the Special Gravitational Wave Session, and another on tidal deformations at the Parallel Session on Perturbation Theory in General Relativity. 

The slides of my talks are available here and here, respectively, whereas some nice pics from the event can be found here; I'm not in any of them, though, so I took this one myself:

Heading to the morning plenary session (hence the sleepy face) at Columbia campus

The GR conferences are organized by The International Society on General Relativity and Gravitation, ISGRG. During the GR21 conference, Prof. Eric Poisson was elected new President of ISGRG and the venue for GR22 in 2019 was decided (it's going to be in Valencia).

After the conference, I went to Boston for a short visit and then flew to LA to attend the workshop "Unifying Tests of General Relativity", organized by Leo Stein and other members of the Caltech in Pasadena, CA.

After a conference like GR21 (where one passes most of the time scattering off the 600+ participants, chatting and discussing projects for which one usually doesn't even have the time to sit down and think about) attending a small workshop (~40 participants, most of which friends and long-standing colleagues) like the one at Caltech was really a relief. I've never been on the West Coast and Pasadena is a lovely town, everyone seems relaxed and I had time to sit down and talk to collaborators I usually see in person just a few times per year. Science-wise, the workshop was excellent in many aspects, and I left Caltech really excited and looking forwards to working again on some new projects (if any, this is probably the best outcome of a successful workshop!) Some pictures of the event can be found here and below:

Group photo next to the Keck Center at Caltech

Me discussing with Nico Yunes and Vitor Cardoso about our recent work on GW ringdown

I managed to break my glasses on the very first day of the workshop. The secretary was a a DIY-type lady and helped me fixing them. 
This was the result.... [pic taken by Thomas Sotiriou]

Richard Brito's got a PhD!

Richard Brito (IST, Lisbon) successfully defended his PhD thesis, entitled "Fundamental fields around compact objects: Massive spin-2 fields, Superradiant instabilities and Stars with dark matter cores" with Vitor Cardoso and myself as supervisor and co-supervisor, respectively.

Richard was awarded a PhD with Distinction and Honours (the jury members were Eugeny Babichev, Carlos Herdeiro, José Lemos and José Natário) and is now moving to the Albert Einstein Institute in Potsdam as a postdoctoral fellow. Kudos Richard!

Richard Brito right after his PhD thesis defense, with supervisor Vitor Cardoso and jury members (from the left: Carlos Herdeiro, Eugeny Babichev, Vitor, Richard, Jose' Lemos, Jose' Natario)

First results from Sardinia Radio Telescope

Are you going to visit Sardinia this summer?
If you arrive at the Airport of Cagliari from NE, probably you will see a strange 64-meter diameter white instrument
in the middle of (almost) nothing.

What it is that?  Keep calm: aliens are not arrived yet. Your holidays are probably save. 
This is the Sardinia Radio Telescope,
a major radio astronomical facility almost ready for outstanding scientific observations. 
Its science goals spread from Radio Astronomy, Geodynamical studies and Space science.

You do not trust me?
Here the  first scientific result from observations  with this extraordinary facility, published on
Monthly Notices of the Royal Astronomical Society:

https://arxiv.org/abs/1607.03636 

They observed a supermassive black hole 
moving at high velocity to a nearby galaxy cluster  3C129.
Here also a brief description of the obtained results from Matteo Murgia (in italian). 

Waiting for other exciting news from the SRT team! 

Second detection of gravitational waves from a binary coalescence

Breaking news are all around the globe after yesterday's press conference by the LIGO/Virgo collaboration, which announced a second very solid gravitational-wave event on Boxing Day, Dec 26 2015, dubbed GW151226.

The waveforms of the 3 events detected by LIGO during O1 (the first observation run). GW150914 and GW151226 are events which are very solidly detected (at more than 5 sigma), whereas LVT151012 has a (small) probability of being a statistical fluctuation. From this page. The inspiral phase of the new event GW151226 lasted much longer than the original GW150914 (about 80 cycles in total)

I warmly suggest you to check this beautiful multimedia page, made by Marc Favata and his group.

As the LIGO/Virgo collaboration put it, the era of gravitational-wave astrophysics is officially started!

Angela Merkel visits ESA

More pics here

German Chancellor Angela Merkel has visited the European Space Agency (ESA) today, in order to promote Germany's participation in ESA's projects.

One cannot get rich with fundamental physics, they said...

..unless you make a landmark discovery such as the first detection of gravitational waves. In such case, you might win a $3 million Breakthrough Prize in Fundamental Physics!

The three funding fathers of LIGO, Ronald P. Drever and Kip. S. Thorne and Rainer Weiss, are going to share $1 million, and the other other $2 million will be split among 1,012 scientists who authored the milestone article in Physical Review Letters and a list of key contributors to the theoretical and experimental understanding of gravitational waves (Luc Blanchet, Thibault Damour, Lawrence Kidder, Frans Pretorius,
Mark Scheel, Saul A. Teukolsky, Rochus E. Vogt) without which LIGO outstanding discovery would not have been possible.

As Richard Feynman brilliantly put it:

This also applies to the economical reward that might following great discoveries, and it is probably the reason why reckless and economically inconvenient science is pursed: because it is passion driven rather than money driven.

Kudos to the LIGO/Virgo Collaboration!

College is not a commodity. Stop treating it like one.

"Unlike a car, college requires the “buyer” to do most of the work to obtain its value. The value of a degree depends more on the student’s input than on the college’s curriculum."

Just came across this excellent article by Hunter Rawlings on the Washington Post, Can't agree more.

Can one hear the shape of a black hole? [*]

[Edit: see also the Synopsis in APS Magazine "Physics", the coverage and this interview (in Italian) by the Italian Institute for Astrophysics (INAF), and the stories in Physics World, NewScientist, Phys.org, Le Monde and Repubblica.]


An orchestra conductor can easily tell a gong from a bell just by their different sound. Can astronomers do the same and tell a black hole from another dark object just by detecting their different gravitational-wave signal? In our recent paper, Vitor Cardoso, Edgardo Franzin and I show that this might not be the case [preprint here].


Last February, the LIGO/Virgo Collaboration announced the first direct detection of gravitational waves by the two laser interferometers advanced LIGO. This historical discovery has been also welcomed as the first conclusive proof for the existence of black holes, the most extreme objects in the Universe. The detected signal --dubbed GW150914-- corresponds to the "pas de deux" of two massive objects, which inspiral around each other and eventually collide in a cosmic spacetime-quake. LIGO data firmly show that the two objects are extremely compact and way too massive to be neutron stars. While providing compelling evidence, this does not represent a bullet-proof confirmation of the existence of black holes by itself. After all, signatures of compact, dark and massive objects come routinely from electromagnetic observations with infrared and X-ray detectors.

What makes GW150914 really unique is that the gravitational-wave signal contains all the final stages of the cosmic evolution of the binary system: the two objects lose an enormous amount of energy through the emission of gravitational waves, approach each other and eventually merge to form a single compact object of about 62 solar masses. After the merger (which lasted only a few milliseconds!) the final object was highly distorted and underwent an adjustment phase known as the "ringdown", in which the object vibrates pretty much like a drum. Just like the notes of the drum depend on its properties (the shape, the size, the material), the "ringdown modes" should carry information about the very nature of the final object produced after the merger.

A comparison between the ringdown signal of a particle falling into a black hole (black dashed line) and the same particle falling into a wormhole (red line). The wormhole geometry is illustrated in the top right corner. The two signals are identical at early times and the "universal" ringdown waveform is associated to the particle reaching point "A" (the light ring). The real quasinormal modes of the wormhole appear only at late times, when the particle reaches the throat (point "B").

Black holes are snatches in the spacetime fabric and their rim ---known as the event horizon--- vibrates in a very peculiar way that was predicted after decades of restless work by using Einstein's theory of general relativity. Scientists hope that, by detecting events like GW150914, one would be able to identify the modes of vibration of the final black hole (the so-called "quasinormal modes") from the ringdown signal. Detecting the quasinormal modes will be the definitive proof that black holes are produced in a binary merger, precisely as predicted by Einstein's theory.


In our recent work (selected as an Editor's Suggestion and featuring the cover of the current issue of Physical Review Letters), we show that this paradigm is incorrect. The vibrations of very compact objects without an event horizon are dramatically different from those of black holes (their frequency is lower and they last much longer time) and, nonetheless, the ringdown signal produced by these "black-hole mimickers" is identical to that of a black hole.

Kip Thorne among the 100 most influential people...

....and the one with the best outfit on Time!

Kip Thorne, our bet for the next Nobel Laureate in Physics, more badass than Walter White.

Good news for eLISA

Some time ago, the European Space Agency appointed a Gravitational Observatory Advisory Team (GOAT) to assess the technical feasibility and effort of the space mission eLISA to build a laser interformeter for gravitational-wave detection. eLISA is the (much) bigger sister of aLIGO and aVirgo, but it operates in space and its arms are longer than 1 million km!

The GOAT reported that the mission is not only technically feasible but scientifically compelling and suggests to anticipate the proposed launch date from 2034 to 2029. It's a very exciting time for gravitational-wave science!

Read the rest of the story on BBC.

Artistic illustration of eLISA's concept

Frank Wilczek on the future of Physics

"What will the next 100 years in physics bring? I don’t know, of course, but it is a mind-expanding question to contemplate." 

This how Nobel Laureate Frank Wilczek starts his beautiful essay on the future of Physics. A must-read!

Frank Wilczek is is Herman Feshbach Professor of Physics at the MIT. In 2004, he shared with David Gross and H. David Politzer the Nobel Prize in Physics for
their discovery of asymptotic freedom in the theory of quantum chromodynamics.  

Today it's a good day to start lecturing

Today I start lecturing my first class, Thermodynamics and Electromagnetism for the degree of Geology at Sapienza.

There are many problems in Italian academia -- and the scientific community is standing up for fighting them -- but today I just feel proud and privileged to have the most beautiful job in one of the most beautiful cities in the world.

On my way to the classroom

Onde Gravitazionali: la musica dello spaziotempo

Dopo l'incredibile rivelazione delle onde gravitazionali, gli amici dell'Associazione Astronomiamo mi hanno ricontattato per organizzare una serata online all'interno dei loro "Incontri di Astronomia". Ho accettato molto volentieri, visto il grande impegno ed entusiasmo che questa associazione mette nella divulgazione scientifica.

Ecco il video della serata, disponibile anche sul loro sito. Buona visione (specie per mia nonna!)

Recommended by us: Time to move on?

''Cosmology and particle physics have long been dominated by theoretical paradigms: Einstein's general theory of relativity in cosmology and the Standard Model of particle physics. The time may have come for paradigm shifts. Does cosmological inflation require a modification of Einstein's gravity? Have experiments at the LHC discovered a new particle beyond the Standard Model? It is premature to answer these questions, but we theorists can dream about the possibilities.''
 

Full conference proceeding  here.

Hey Grandma look: I finally study something that exists!

So much has been already written about today's announcement of the first direct discovery of the gravitational waves from two merging black holes by the advanced LIGO detector. Some examples:

[1], [2], [3] (this beautiful piece by my friend and colleague Emanuele Berti)

In Italian press: [1], [2], [3]

Exactly 100 years ago, Albert Einstein proved that his theory of gravity, General Relativity, predicted the existence of gravitational waves.

This is nothing but one of the most outstanding historic discoveries in science. However, since you can find much deeper posts on this topic, here are some random, not-so-serious, thoughts hastily written down while watching today's live streaming announcement (sorry for typos, this is written on the wings):

1) Look Grandma: I finally study something that exists!
[Last time someone told my grandma that maybe black holes didn't exist after all.. she literally cried!]

2) Wow, my field of research has finally become mainstream! [is this good of bad? Anyway, the largest lecture hall at the Physics Department at Sapienza was full 30 mins before the live streaming..that's pretty uncommon for something related to gravity...]

3) The first direct detection of gravitational waves is really great, but what is emitting these waves is even more interesting: these are two black holes orbiting each other, loosing energy through gravitational-wave emission and finally merging to form a final big black hole. All of this is beautifully predicted by Einstein's theory of General Relativity and required several decades of theoretical, experimental and computational work.

4) Now everyone claims they have predicted that the signal from a binary black hole merger would have been detected. Truth is, just 6 months ago nobody would have bet on this particular source.

5) Related to this, isn't it amazing how physics works? It takes just a single observation to completely change the paradigm that theorists have built over decades. Just 6 months ago very few people would have predict that LIGO -even in the case of a detection- would have been able to test General Relativity or just to make some science or astrophysics out of this discovery. Well, judging from the result of the paper published today (and the companion papers to come) this expectation was completely wrong.

6) Finally, my bets for the Nobel Prize (in random order)

Rainer Weiss, one of the founders of LIGO

Roy Kerr, who discovered the unique solution of General Relativity describing a spinning black hole

Kip Thorne, one of the cofounders of LIGO, and of the fathers of modern General Relativity
(plus one of the creator of the movie Interstellar)

Visit to CERN

I am just back from CERN, where I stayed over this week to visit Diego Blas at the CERN THeory Division and to give the talk "Compact Objects as Dark-Matter Probes".

Some sparse thoughts on the visit:

1) On the first night, I checked in at a hotel in Geneva instead of staying at the CERN hostel. That was a very bad move. Everything in Geneva is unbelievable expensive and the hotel (albeit 3 star and averaged rated) turned out to be quite bad. I got bed bugs, i am still full of pinches, and i'm still trying to disinfect my clothes at home...

2) On the other hand, the hostel at CERN (where I stayed for the rest of the week) was excellent. The room was clean and cozy and equipped with a large desk. Everything at CERN seems to be designed to simply researchers' life and work.

3) I was impressed by the low average age of people working at CERN. About 10K work at the center and most of them are young PhDs or postdocs. The comparison with the average Italian university, where most of the faculty members and staff are over 40, is impressive. I recently read an interview by CERN Director Fabiola Gianotti, who was precisely commenting on this fact. However, experiencing it directly is a different kettle of fish.

4) Although CERN is big and experiments are scattered around a 27-km underground ring, I enjoyed the fact that most offices are located in a handful of buildings which are connected among each other. This basically means that theorists can chat over a coffee with experimentalists, or that it is easy to attend the (enormous) number of talks and lectures that are organized on a daily basis. The canteen is also common for all buildings and researchers from different collaborations and experiments meet there to have lunch (and sometimes dinner) together.

5) Overall, the atmosphere is definitely suggestive, even for someone like me who's used to see so many physicists in the same place (I guess that for the numerous students who regularly visit CERN during a school trip it must be really a unique experience).

6) I had the opportunity to meet various friends with whom I went to college in Cagliari (some of them are also authors of this blog). Funny enough, the excess of physicists from Cagliari University, especially in the LHCb experiment, is beyond 5 sigma. Thus, I had the opportunity to visit the LHCb experiment and control room, as this picture testifies:

Visit to the LHCb experiment. 
From the left to the right: Andrea (aka Scrilly), Francesco (both CERN Fellows) and me.

7) BTW, I also had the opportunity to hear more rumors around the 750 GeV diphoton resonance. Every theorist I talked to was extremely excited and sometimes confident about the possibility that ATLAS and CMS experiments have detected something new. Funny enough, every experimentalist I talked to was instead extremely cautious and, most of the time, pessimistic. I should definitely write about this in a next post but, as you probably have heard, this coming week the spotlight will all be on LIGO's announcement of the first direct detection of gravitational waves (!) No doubts on the topic of my next post (after Thursday).

Vitor Cardoso's and Thomas Sotiriou's visits @Sapienza

In the last two months we had two guests at our Department:

• Vitor Cardoso, leader of the strong gravity group at IST, was a Visiting Professor at Sapienza in December and January; some weeks ago he gave a talk on "Black holes as laboratories of fundamental physics"
• Thomas Sotiriou, leader of the gravity group "Challenging General Relativity" at Nottingham University, visited our group during the last week of January and gave a talk on "Lorentz violations, causality, and black holes".

Group picture taken [1] after a goodbye social dinner in the historical center of Rome. 
From the left to the right: Leonardo, Thomas, Vitor, Paolo, Ana and Leonardo Macelloni (an old friend from the University of Mississippi who I met at the time of my first moka machine)

[1] By chance, this picture was taken by the bodyguard of President of the Senate Renato Schifani, who was passing by while we were looking for a random photographer.

Recommended by us: Science Pie - A podcast about physics, history, literature and much more

Dennis Schulz, a physics student, and Annika Brockschmidt, a history and German student, are two podcast enthusiasts based in Heidelberg (Germany).

They created the independent podcast Science Pie, focussing on the variety of subjects science can offer. Their topics range from history to physics, from literature to engineering, in particular interdisciplinary work - a range of topics hard to find in the jungle of podcasts. They often use interviews with an involved researcher or professor as a base for the episodes.
And all of this is provided in a bilingual version (English/German) and a special care for details.

Dennis and Annika’s podcast successfully meets the effort of joining science curiosities, interesting stories about people and a collection of knowledge and facts on history, literature and myths. Join them and enjoy!

AstronomiAmo

Domani saro' ospite della trasmissione web dell'Associazione AstronomiAmo  per parlare di "Stelle di neutroni e buchi neri come laboratori per la rivelazione di materia oscura".

La serata e' condotta da Stefano Capretti e sara' trasmessa in diretta sulla pagina web dell'associazione e sul canale Youtube, nel quale trovate tutte le trasmissioni precedenti e che vi invito caldamente a seguire.

Appuntamento domani, Martedi' 19 Gennaio alle 21:30.

La locandina dei prossimi eventi online organizzati dall'Associazione AstronomiAmo.

Aggiornamento: Ecco il video della serata