 I'm happy to be a part of this important event. My name is Vasilisa. And I represent today a physics part of IHS. And I will tell you about a very mysterious thing, which is gravity. Sorry, it is not easy to talk about such an impressive thing. I'm impressed since I entered the university. So I study generalized Einstein-Carton theory. If we talk about, oh, it doesn't work. Sorry. Yeah, it works. But by the way, if you have any problems with sound, please don't hesitate to tell me. If we talk about gravity, we should start from general relativity, which is a geometrical theory. The main idea is that gravity is geometry. And the geometry of the world around us is defined by the material content of the world around us, which means that these processes that we see, something falls down. All this is defined by the objects of the world around us, the earth, the sun, everything. And the main equation of general relativity is here, before your eyes. On the left-hand side, we have geometry, which is the curvature of spacetime. And on the right-hand side, we have material content of the universe, of the world. And so this is a very elegant idea. And this theory, Einstein's general relativity, agrees for now with all experimental data, such as various solar system tests and direct observation of gravitational waves and direct observations of black holes surrounding, which you can see here. By the way, if you don't know what to look at, you should look at this small black circle in the center. And on this part of the picture, which is brighter than another part, these are the main confirmations of general relativity. So everything looks fine, but there are two dark clouds on the perfect blue sky of general relativity. And the first dark cloud is related to the fact that if we look at some galaxy, it can be our galaxy or it can be any other galaxy. We can see that the stars, which are far away from the galactic center, which is supposed to move slowly because they are far away. They don't care about what happens in the galactic center. Actually, these stars are moving very fast. They are rotating very fast around the galactic center. They should not rotate that fast. And the only way to explain this phenomenon within general relativity is to admit that all the galaxies are put in some large, enormously large hollow of invisible matter, which is called dark matter. And these hollows are 10 times larger than the side of the galaxy. So it means that there is a huge amount of dark matter, which surrounds the galaxies. There are a huge amount of dark matter in the universe. This is one dark cloud, and another dark cloud is the fact that in the end of 90s, the accelerated expansion of the universe was discovered. And again, the only way to explain this accelerated expansion within the general relativity is to admit that our universe consists of not only matter, but also some unclear and known new type of energy, which is called dark energy. And this dark energy amount, 70% of the universe content. So it means that in the universe, who have 70% of dark energy and 30% of matter, it's risen to 25. I'm sorry, I forgot how to add numbers. But only five persons of this 30 persons of matter is actually a real, visible matter, which means that if general relativity is absolutely right and correct everywhere, we live in the universe which is full of matter and energy with nothing about. And I say now, 70% and I remember how 15 years ago, my professor gave a talk, and he also said, 70%, which means that 15 years passed and nothing changed. These dark clouds, these two dark clouds remain. And scientists still don't know how to correctly explain them. Experimentalists try to find dark matter particles already for 30 years, and they did not yet succeed. And this is why the following question arises. Is a general relativity 100% right or not? Because look, these two phenomena I was talking about here, they are large scale phenomena. These are cosmological phenomena, something which happens on the large scale. So maybe there exists some other theory which coincides with general relativity on the small scales like solar system, but which differs from general relativity on the large scales. Does there exist another gravitational theory which explains these two dark clouds, these two large scale phenomena, better than general relativity? And many theories actually were proposed. And I will talk about the one theory, which as exactly as a general relativity, this theory has a geometric origin. Because soon after Einstein's general relativity was proposed, mathematician Ely Cartan realized that the geometry used by general relativity can be actually generalized. It is very interesting to see how it happens, so I will explain you. Let us take some curved manifold, some, for example, curved surface. Let's take a point at this surface and let's introduce a vector. Of course, vectors cannot exist on the curved surface, so we have to introduce a plane, which is called a fine space. And now I would like to move this vector along some close circuit. Of course, I will move it together with this plane in some way. For example, I can roll this plane on this surface and after I will do it, I will see some closed trajectory on the surface and also I will see some trajectory on the plane like this. And generally speaking, the trajectory which I will see on the plane will be not closed. And the fact that this trajectory is not closed is expressed through the new geometrical notion, which is called torsion. And also the initial vector and the final vector will have a different orientation, which is expressed by curvature and this was already known from geometry of general relativity. So as a conclusion, one can see that Einstein's general relativity is based on curvature. While in the theory of Kaftan, there are two actors, curvature, the same as in general relativity and also torsion. And if you remember my first slide, curvature interacts with matter and torsion should also interact with something and it's supposed to interact with spin of particles. So we see that geometry interacts with some properties of matter. And so Kaftan asked, could there be a theory of gravity based on this generalized geometry? And he proposed one model which had no experimental consequences. But after that, people still asked again and again the same question because this idea, this beautiful mathematical idea is attractive. And at some stage, people came to the theory which is called torsion by gravity. I must say, so the term torsion by gravity was introduced by me and Thibaut Damou. Actually, many other authors worked on this theory. But me, I concentrated on the real observational consequences of this theory and I work on it. Why it is by gravity? Because roughly speaking, we have two gravitons in this theory. We have usual massless graviton and we also have massive graviton with mass kappa, which is here. So I did some studies of this theory and my last studies, me and the professor Thibaut Damou, my last studies are about black holes in torsion by gravity. Namely, we found recently that there are two types of black holes in this model. The first type is a usual black holes, exactly the same as in general relativity. Maybe not exactly the same, but it's another story, roughly speaking, exactly the same. And another interesting type of black holes also exist. Exist in the limit when mass of the second graviton is small. This second type of black hole which is called torsion hair, which means that outside the black hole there exists some additional field, additional to matrix, which is torsion. And the impressive part of this study is related to the recent Nobel Prize of this year, Nobel Prize, which was given for the study of supermassive, compact object in the center of our galaxy, which is admitted by most of the scientists to be a black hole. So, somewhere here, there is a black hole and on this picture here, if you can see my mouse, you can see the orbits, the trajectories of the stars which rotate around this black hole, really close to this black hole. And these stars are the object of particular interest of astronomers, especially one star which was observed very accurately. This star, which is called S2, among other characteristics of this star, there is a thing which is called periastron precession, which this is an effect, a phenomenon of precession of the orbit, which means that orbit is not just an ellipse, a constant ellipse, but this ellipse moves exactly as you can see on this picture. This ellipse slowly, slightly rotates each time. And the periastron precession of S2 star was measured very well to compare the predictions of general relativity and of other theories of gravity with reality. And I asked myself, what if this black hole, which is in the center of our galaxy, is not a usual black hole of general relativity, but this second type of black hole, this second type of black hole, which I have in my model, what if this black hole is my black hole? What we see in this case, what are the observational consequences? And one can calculate the periastron precession of the star S2 around my black hole. And actually, surprisingly, I found that if this black hole is my black hole, the periastron precession would be enormous. It would be much, much bigger than the periastron precession in general relativity, which means that if the object in the galactic center is my black hole, it means that the torsion by gravity is restricted. Namely, if you remember the Lagrangian, which is here, I have here the parameter eta, which is a coupling constant of torsion. So, this test, this periastron precession test, gave a huge restriction on the coupling constant. If I assume that the central object is my black hole, of course, it is not necessary. Maybe it is not my black hole. Maybe it is a black hole of a GR type. So, this is what I do, and this is what I will continue to do. So, I will continue to look at the observational consequences of this interesting theory of gravity, because, again, this geometrical idea on which my model-based is very attractive. The question which I would like to answer is, is this model viable? Can this model be really... Sorry for the English word. Does this model describe the reality better than general relativity or not? We'll see. This is what I wanted to say.