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.