Ginestra Bianconi: The Physicist Who (Unexpectedly) Derived Gravity From Entropy

**SPEAKER_1** (0:00)
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**Ginestra Bianconi** (0:30)
Gravity from Entropy is a new theory that quantifies the information content of the universe. It somehow challenged the reductionist approach.

**Curt Jaimungal** (0:42)
This is Ginestra Bianconi, Professor of Applied Mathematics at Queen Mary University of London, an architect of modern network science. Over the past few years, she went into the continuum despite coming from the discrete sector and published the radical paper Gravity from Entropy.
On this channel, I, Curt Jaimungal, interview researchers regarding their theories of reality with rigor and technical depth. Today, Bianconi's case that gravity can be derived from entropy, how dark energy emerges from her equations on its own, always positive, not anti-deceder. And we close with the advice she gives her PhD students.

**Ginestra Bianconi** (1:21)
What keeps me awake at night is the second quantization of this theory. Maybe there is no single static solution of the black hole in gravity from entropy. And maybe this singularity is avoided.

**Curt Jaimungal** (1:36)
What is gravity?

**Ginestra Bianconi** (1:38)
Well, I think we know that gravity is a fundamental force. And we know this since Newton. But it is a particular fundamental force, because it somehow, from my perspective, challenged the reductionist approach. Because it is about geometry. And this is what we learn from Einstein.
And geometry is what allow all the other fundamental force to occur in nature.
So somehow, I think that gravity is about geometry, and how geometry interacts with matter fields. And this is a general question. I mean, from my perspective, this question goes also behind gravity itself. Because it is a problem of the interplay between, generally speaking, structure and dynamics, that is at the fundamental mathematical level, common to many different other fields.

**Curt Jaimungal** (2:43)
How did a network topologist like yourself get interested in gravity?

**Ginestra Bianconi** (2:47)
Yeah. So this is a nice question. In my career, I started doing research in this discrete structure that are networks from northern links. Then I moved from networks to simplexial complex, which allows to capture a discrete geometry and topology of a lot of system, and also real data that can be described with this system. I cannot maybe overstate that maybe in most of my research since now, I have always focused on the interplay between structure and dynamics. This is very central, for instance, in network theory as well. But there are important results in network science. For instance, how the topology of the network, so the presence of big hub, can affect epidemic spreading or things like that. But recently, it is becoming clear that topology and geometry also play a fundamental role in shaping the interplay between structure and dynamics. I've been working a lot on how topology shapes dynamics in network, and this is an important mathematical problem that has implications for machine learning up to brain research.
But if you want to build this theory, that is a theory that includes topology, geometry and dynamics, there are two aspects. One aspect is that you want to write a theory that captures this interplay using information theory, because ultimately you want to study, to describe the system in term of their information content. And maybe we can go back to that.
But on the other side, you don't have enough mathematics in the discrete, so also the notion of curvature is not well defined in the discrete setting. It's a very important proposal. I was giving a seminar at ICTP in Trieste in Italy, and somebody told me, but if you are doing this, why don't you do that in the continuum?
And I answered, no, I will never go in the continuum. And then I reflected on this. And yes, so the continuum of this theory has to do a lot with gravity. And then why don't pacing the real challenging problem and that is quantum gravity and gravity. Because somehow I think maybe a bit controversial to understand the brain is more difficult to understand quantum gravity.