In the last 20 years of his life, Albert Einstein became a special figure in the physics community, with this beloved eccentric man’s favorite subjects of controversy attracting puzzled looks in the community. While quantum theory – the theory of infinitely small objects – was measured with unprecedented precision, Einstein did not consider it a fundamental theory. During the last years of his life, he sought to unify his theory of gravitational relativity with quantum descriptions of the world. However, he failed and died without being able to see his most fervent dream come true.

Scientist Albert Einstein. Photo: Time

More than 40 years later, as Einstein expected, the persistent problem of contradictions between **general relativity** and quantum theory is about to be unified, although the answer is still elusive. If the theories of certain physicists on “**superstring theory**” (or string theory for short) is true, so we live in a weirder world than we imagined.

It is a world with 10 spatial dimensions, some of which are wrapped in a microscopic dimension and the others are of large perceptible dimensions. It is a world where the space-time distinction is relative (in the sense of general relativity), or in fact known notions of space-time have almost disappeared. According to Brian Greene – a professor at Columbia University and author of a book on the subject – “*If String Theory Is Correct, The Fabric Of Our Universe Might Astonish Even Einstein*”.

In string theory, there are no elementary particles (like electrons or quarks) but rather vibrating string elements. Source: The Laughing Squid

The figure above is an illustration of a closed string, characteristic of a massless graviton with a spin of 2 (which is the middle particle of gravity). This is one of the most interesting features of string theory. It is natural and inevitable to include gravity among the inevitable interactions. Photo: John Stone

In string theory, there are no elementary particles (like electrons or quarks) but rather vibrating string elements. Each vibration pattern corresponds to a different type of particle and determines the charge and mass of that particle. According to the current understanding of this theory, strings have no intrinsic structure, they are the most basic components of matter. The consequences of replacing point particles with vibrating strings are considerable. The only suitable mechanism to describe these strings is a space with 10, even 11 dimensions, of which 6 or 7 have been contracted. These additional dimensions define the properties of the world in which we live. The remaining dimensions with larger dimensions are the ordinary spacetime that we can perceive.

Of the 10 dimensions of spacetime in superstring theory, only four are observed. Somehow we have to relate them if we want to use this theory to describe our universe. To do this, we roll the 6 dimensions of the subspace into a very small cube. If the size of this block of space is equal to the scale of the string (10^-33 cm), their presence cannot be detected directly – they are too small. The end result is that we are back to the familiar (3+1) dimensional space, but there is still an infinitely small 6 spatial dimensional “ball” that exists attached to every point in our 4 dimensional universe. .

As a “unification” theory, string theory tries to describe the four forces of nature, and indeed one of the solutions to the string equations is to describe a force like gravity. It’s a testament to the power and beauty of string theory, that physicists choose to ignore notions of spacetime in favor of a 10-dimensional world, rather than questioning the way in which the search for a unified theory led them.

Ảnh: World Science Festival

String theory can successfully explain gravity and predict supersymmetric particles. However, until recent years there was little connection between this theory and other pieces of the physics puzzle. No definitive results or predictions were found. It’s still nothing more than a nice mathematical structure.

That all changed in 1996 when Andrew Armstrong of the Institute for Theoretical Physics in Santa Barbara and Cum-run Vafa of Harvard University used string theory to construct a similar type of black hole. of quantum mechanics, which describe an electron bound to a proton.

Armstrong and Vafa confirmed a result drawn up by Jacob Bekenstein and Stephen Hawking in the late 1970s. Bekenstein and Hawking discovered that there is some degree of disorder (or ‘entropy’) in a type of dense black hole, in very large particular. This is a surprising result because no one has been able to understand (even calculations show no understanding) how a simple object like a black hole (which can be simply described by its mass and rotation) has such a high degree of chaos.

Illustration of a black hole. Picture; Large courses more

By using string theory to construct this particular type of black hole, Strominger and Vafa were able to derive the exact value of chaos predicted by Bekenstein and Hawking. This result shocked the physics community. For the first time a result of classical physics has been obtained thanks to string theory. Although the resulting black holes have little in common with those thought to exist at the center of galaxies, these new calculations point to a link between string theory and gravity. In addition, the calculations provide insight into the physical aspects of the response.

Nobody knows yet if this is the fundamental theory – the theory of all things, if such a theoryactually exists there. Yet the elegance and potential of string theory make it a prime candidate for explaining the internal structures of the universe.

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