# The fuzzy world of the quantum black hole

## Alice down the black hole

‘Imagine an elephant in a room, surrounded by a bunch of blindfolded people. These people have to rely on touch to determine what is in the room with them. One person describes a rough piece of rope (the tail), another a tree (one of the legs), and the third a flexible tube (the trunk). It sounds like they’re each describing different objects, when in fact they’re just describing different parts of the same object.’

This thought experiment is relevant to various theories in physics, such as the theory of relativity, quantum theory, black holes, and string theory. They are all pieces of the same puzzle that aims to determine how laws of nature work. Mazumdar is helping to solve that puzzle.

‘I’m trying to find if and where all these theories overlap. If they are all pieces of a larger puzzle, we have to find the connections where those pieces match.’

## Newton

Ever since Newton came up with his theory of gravity, physicists have been trying to improve upon it. ‘His theories work well in the everyday world, but they don’t hold up if you try to apply them on either a really large scale or a really small one’, Mazumdar explains.

‘That is why Einstein came up with the theory of relativity and Stephen Hawking developed a quantum theory for black holes.’ Their aim wasn’t to prove Newton wrong, but to improve the accuracy of his theories.

But these newer theories are turning out to have limitations as well. Mazumdar has no issue with this. ‘Nature is superior to us. It’s much more complicated than we could ever hope to understand. By using our reasoning skills and simplifying things we can make models to try and understand it.’

But each model reveals new theoretical situations and observations, either over short distances or in a very short time, that these theories can’t explain. When these mathematical models fail, it’s called a singularity. Singularities are present in both the black hole and Big Bang theories. ‘Physicists are always coming up with new theories to try and solve these singularities. We’ll keep going until we finally find a theory that applies to every single situation.’

## New theory

Mazumbar uses different approaches to try and solve the puzzle. ‘The problem is that it looks like this only works if I abandon a basic principle of physics. The existence of gravity, for example, or the fact that everything takes place at a certain place and time.’

He has decided to abandon time and space for now. But our lives take place in time and space, which means we can’t imagine a reality without those dimensions. You are currently reading this article, and you can’t be in two places at once. And you’re here at this particular time, and not one hundred years later.

If you try to imagine a location without a specific time and place, you live without clocks or rulers. You can be everywhere at once, and you can be here right now, while simultaneously existing a hundred years ago. These are incomprehensible, staggering ideas.

Try to see it as Alice’s Wonderland

By abandoning the basic principle of time and space, Mazumdar was able to develop a new theory. He describes Hawking’s concept of black holes slightly differently: they are places where time and space don’t exist.

## Rabbit hole

‘Try to see it as Alice’s Wonderland. When she’s falling through the rabbit hole, she is visiting all these different places in different times. But all of that could never fit into a rabbit hole. And when she comes out of it again, no time has passed at all. That means she was in various places simultaneously.’ These quantum holes – ‘I prefer to call them non-local compact objects’ – solve several issues that black holes present.

So how do physicists come up with these theories? ‘Some of it is just doing a lot of thinking and asking the right questions’, says Mazumdar. ‘There’s a lot of philosophy involved in physics. You have to think about certain questions a lot. But there is also quite a bit of maths. We calculate everything that we do, to find out whether our theories are even possible and whether they match our observations.’

### A vacuum with no time and space

The theory of black holes posits that there are locations in space that nothing can escape from, not even light. That is because the compact mass in these holes has enormous gravity, which causes an extreme distortion of the space-time dimension. But measurements have shown that this theory cannot be applied on a very small scale. It’s as though the structure of space-time becomes increasingly vague as we zoom in.

In Mazumdar’s non-structured compact objects – or quantum black holes – these space-time singularities simply don’t exist. The space-time in a quantum black hole becomes part of that vague world, in which only quantum superpositions of particles exist: they are everywhere at once. They can exist in every single hallway, every single room.

The particles can exit these, but only very slowly; even slower than Hawking had calculated on the basis of their mass. This means that particles can escape the holes, but we can never know where or when. The radiation leaving the quantum black holes should be detectable by LIGO and Virgo, says Mazumdar.

Finding real proof is difficult. He hopes to receive positive measuring results from LIGO and Virgo. These gravity detectors in Italy and the United States detect gravitational waves in space. ‘If these quantum black holes exist, we should be able to see this in the wave patterns they detect.’

My work is for future generations. I don’t care about the impact today

Mazumdar has to wait for these patterns to emerge to see if he is right. And it’s not like physicists all over the world are jumping for joy at his theory. ‘Some of them do think it could be a real possibility, but others are sceptical’, Mazumdar acknowledges. ‘But I don’t care. My work is for future generations. I don’t care about the impact today.’

## Recognition

Laughing, he adds: ‘There are so many great physicists who didn’t get recognition for their work until after their death.’

To be honest, he doesn’t really care his theory is right. ‘I’m just curious. I want to know how things work. If this theory doesn’t solve the singularities, we’ll have to look elsewhere.’

His curiosity is perhaps his defining characteristic. ‘I’m not a brilliant mathematician; I have colleagues who are much better at that. But I’m curious and I ask a lot of questions. I like to play with ideas, enjoy rebelliously going in a completely different direction, coming up with daring hypotheses. We shouldn’t run away from the singularities we find. We should see them as challenges to look further, to learn, and to discover new things.’