Black technology starts from the steel suit

Chapter 242 242 Solving the Quality Gap
Wang Feng, who doesn't need to work on projects, is temporarily free. He now has a lot of time to give lessons to the students, or to spend time with his wife.

When I got married, I vowed to accompany her well, but I didn't expect to get busy again after the vacation, so that I couldn't complete the agreement with the other party.

Although Lily didn't say anything, Wang Feng still felt a little embarrassed in his heart.

He remembered what his father once said to him: You must never take it for granted just because others understand you. You must be able to empathize, so that the relationship can last long.

This is the same whether it is friendship or love, even teacher-student relationship.

I still remember that I seemed to promise the students that I would give them 4-6 classes in a semester, but after I got busy, I had to hand them over to the teaching assistants. Now that I think about it, I feel sorry for them.

that's embarrassing
"Ahem, I'm sorry students, the course of this semester is already over half, but because I was too busy with my previous work, I couldn't give you a normal class."

"Now I announce that from this week onwards, I will be the one to teach you normally, and you can inform each other."

After Wang Feng edited the announcement, he sent it out, and then he began to ask the teaching assistant where the course was going, and the completion of the homework he had reserved before.

Yes, although it is only an elective course, it still has homework. There are even more homework than a main course, and the requirements are very strict, but just like that, a large number of people come to the class.

Even the School of Chemistry has included this course in the ranks of professional elective courses, requiring students to take it.

【Harry Road】? ? ?
Boss, are you done?

Actually edited an announcement and sent it to us?
【Call me Dad】Σ(⊙▽⊙“a
I thought it was impossible to see the boss this semester, but I didn't expect to hear the boss in class. I am so happy!
Are classes starting this week? I'll let my boys know!

[All roommates want to be sons] Dad is here, no need to notify.

But if the boss is going to have class, it's best for us to go and get a seat the night before, otherwise we'll have to listen outside the door.

[I can’t hold it anymore] It’s uncomfortable, why is it that even though it’s a class in our school, sometimes we can’t get a seat?

I can tolerate students from other departments in the school coming to rub classes, but students from other schools also come to rub classes.
Can't it be limited?

【Revitalize China】Student, what are you thinking? Instead of rushing to grab a seat earlier, you are complaining here why people from other schools come to our school to take classes?

Are you a little too selfish?
Your own desire to make progress is not strong, but instead blame others for pursuing progress?
Seeing that the topic in the group began to develop in an unpredictable direction, the administrator came out at this time.

[Teaching Assistant] The day after tomorrow is class time. Remember to bring your homework, and remind students who haven't seen it.

(O_o)??
The group suddenly became quiet.

Not to mention their quarrels in the group, although everyone's age may not be much, but everyone is no longer at the same level in terms of thought and realm.

While they were still worrying about homework problems, Wang Feng was already thinking about how to complete the unification of strong interaction and electromagnetic interaction.

In the mid-70s, people further proposed the grand unified theory of the unity of strong, weak and electromagnetic effects.One of the conclusions of the grand unified theory is to predict that the proton will decay, which is contradictory to the experimental results.

gravitational relationship
The reason gravity is so difficult to fit into this picture is because gravity is extremely weak compared to the other three forces of nature.In a sense, though, gravity is equally simple and tractable as electromagnetism, since it requires only one carrier particle, the massless graviton.

A passage in John Malone's "Mysteries of Science" makes it very clear: "At the level of elementary particles, gravity basically has no effect.

A hydrogen atom composed of an electron and a proton does not rely on gravity, but a stronger electromagnetic force.How big is it?10^40 times larger.As the French physicist and writer Tiana said: "If there is no electromagnetic force, only under the action of gravity, one hydrogen atom will fill the whole world."Gravity is very weak, it is impossible to combine electrons and protons so tightly
Unless gravity can be unified with the other three forces, there will be no 'theory of everything', or the holy grail of modern science such as grand unified theories.

The difficulty of including gravity in the TOE can be understood by examining how the four fundamental forces 'split' from a unified interaction, which physicists believe should have occurred when the universe was created by the Big Bang when it was first born.

One of the essential differences between photon and intermediate vector boson and gluon is that photon has no mass, but other particles have mass.Photons are easy to create because they have no mass, and can (in principle) travel throughout the universe.Bosons, which convey the weak and strong forces, cannot do this.In an interaction, the mass required to 'create' a particular set of bosons is borrowed from the vacuum according to the uncertainty principle of quantum mechanics.

But the uncertainty principle states that these so-called 'virtual' particles can appear and disappear from time to time, provided they don't survive long enough to avoid being 'noticed' by the universe.The more massive such a particle is, the more energy it will have to borrow during its brief lifetime, and the sooner it will have to repay the debt.This limits how far the boson can travel before completing its task and disappearing.

short-range particles confined to the nucleus
But when the universe was young, it was soaked in a sea of ​​energy from a primordial fireball.As long as this energy density is high enough, even gluons and intermediate vector bosons can extract enough energy from the fireball to become real particles and wander around in the fireball.At that point, they are truly equivalent to photons, not just similar; all fundamental interactions are equally strong and long-range effects.As the universe expanded and cooled, they gradually lost some of their energy, becoming what we see as short-range particles confined inside atomic nuclei.

Gravity remains on its own.According to the best theories, gravity is as strong as all other forces when the temperature of the universe as a whole is .As the universe began to slowly expand and cool, the other three forces remained unified.Seconds after the beginning, when the temperature was reached, the universe cooled to the point where it could no longer support the carrier of the strong force, so the strong force was limited to the distance we can see.

When the second is reached, the temperature is , the universe is cooled down to be unable to maintain the intermediate vector boson, and then, the weak force is also changed into the short-range force.This happened at a time when the temperature of the entire universe was comparable to the highest energies hitherto achieved by particle accelerators on Earth—one of the reasons why the electroweak theory is far more robust than QCD (because of the ability to compare with experiments).

The difficulty of including gravity in a unified theory is easy to see from the above picture.Interestingly, however, gravity and electromagnetism were included in a unified theory even before the strong and weak types of interactions were discovered!This search for a unified theory, largely forgotten for many years after the discovery of the two 'additional' forces, was a frontrunner in the long quest for a Theory of Everything.

General relativity uses curvature to describe gravity.Shortly after Albert Einstein proposed this concept, he found that when the five-dimensional curvature was described by equations equivalent to Einstein's general relativity equations, he obtained the well-known Einstein equations that are parallel to Maxwell's electromagnetic field equations Field equations in theory.

A few years later, in the 1920s, this five-dimensional unification of gravity and electromagnetic fields was extended even to include quantum effects, which became known as the Kaluza-Klein theory after the two pioneering scientists who pioneered the research.

All theories that involve adding extra dimensions to calculations are known as Kaluza-Klein theories, but this treatment has long been neglected because, in order to make the discovery after Kaluza-Klein's initial The more complex weak and strong interaction effects are included, which require not one but several 'extra' dimensions.

If photons are ripples in the fifth dimension, then (roughly speaking) Z particles can be seen as ripples in the sixth dimension, and so on.

There are two reasons why this type of theory became popular again in the 1980s.First, attempts to construct grand unified theories have been tiresomely complicated, some of which seem to require the addition of extra dimensions anyway.

Since a lot of extra dimensions are needed anyway, why not the Kaluza-Klein approach?Second, mathematical physicists became interested in string theory, in which entities traditionally thought of as point-like particles can be described as tiny pieces of one-dimensional 'strings' (much smaller than protons).

String theory can only 'work' in many dimensions, and it gives us an extremely rich reward - gravity.

Theorists amused themselves by deriving various equations to describe this kind of multidimensional string interaction, and they found that the closed string loops described by some equations had exactly the properties required for the gravitational description—the string loops were actually gravitons.

String theory is a theory in theoretical physics.A fundamental point of string theory is that the fundamental units of nature are not particles like electrons, photons, neutrinos, and quarks.

These things that look like particles are actually very small closed circles of strings (called closed strings or closed strings). The different vibrations and movements of the closed strings produce a variety of different elementary particles.String theory is the most promising theory to unify nature's fundamental particles and four interacting forces.

Superstring theory is the most natural consequence of physicists' quest for a unified theory.After Einstein established the theory of relativity, he naturally thought of unifying the two known interactions at that time - gravitation and electromagnetism.He spent nearly 40 years of his main energy in the second half of his life to seek and establish a unified theory, but without success.

Looking back at history, Einstein's failure is not surprising.In fact, there are two other interacting forces in nature - the weak force and the strong force.It is already known that three of the four interacting forces in nature, except gravity, can be described by quantum theory. The formation of electromagnetic, weak and strong interacting forces is explained by the assumption of mutual exchange of "quanta".

However, the formation of gravity is another matter entirely. Einstein's general theory of relativity explains gravity in terms of the geometric properties of matter affecting space.In this picture, the matter that pervades space bends space, and the curved space determines the motion of particles.

People can also explain gravitation by imitating the method of explaining electromagnetic force. At this time, the "quantum" of matter exchange is called graviton, but this attempt has encountered difficulties in principle—the quantized general relativity is not renormalizable , therefore, quantization and general relativity are inconsistent with each other.

Superstring theory is the most eye-catching, and it is still quite far from a unified theory of supersymmetry.An important direction of exploration in particle theory is the study of supersymmetric unified theory. The first goal is to expand the grand unified theory to include gravity, so as to unify the four basic interactions; the second is to explore quarks and leptons. The internal structure of the "subquark" model is proposed, so that the fermions whose spin is a half-integer and the bosons whose spin is an integer are unified.

Superstring theory is a self-consistent theory established by people abandoning the assumption that elementary particles are point particles and replacing them with the assumption that elementary particles are one-dimensional strings. Various particles in nature are different vibrations of one-dimensional strings model.Unlike previous quantum field theories and gauge theories, superstring theory requires the existence of gravity, as well as gauge principles and supersymmetry.

Undoubtedly, the natural unification of gravity and other interacting forces induced by gauge fields is one of the most fascinating features of superstring theory.Therefore, starting from the end of 1984, when people realized that superstring theory could provide a unified theory that encompasses the Standard Model, a large number of talented young people naturally devoted themselves to the research of superstring theory.

At present, we have completed the unification of weak interaction and electromagnetic interaction, and even developed its usage. That is to say, if strong interaction and electromagnetic interaction can be unified, it is very likely to become a solution to a certain key to nuclear technology.

The mass gap problem is the theoretical key to understanding strong interactions in quantum chromodynamics and is related to the mathematical foundation of theoretical physics. Its solution will mean the emergence of a mathematically complete quantum gauge field theory.Physicists generally believe in the existence of a mass gap, but have yet to find conclusive mathematical and physical proof.

Young's theory is a gauge theory based on the SU(N) group, or more generally, a compact, semi-simple Lie group.Chenning Yang, Mills theory aims to describe the behavior of elementary particles using these non-Abelian Lie groups and the unified core of electromagnetic and weak forces (i.e., U(1)×SU(2)) and the strong force of quantum chromodynamic theory (based on SU(3)).Thus forming the basis of our understanding of the Standard Model of particle physics.

The Yang-Mills field is the generalization of the electromagnetic field.It is nonlinear, which is the same as Einstein's field equations, which are nonlinear partial differential equations.The contribution of Yang Zhenning and Mills in 1954 was to extend the gauge field and apply it to the interaction of elementary particles, which resulted in the idea of ​​unifying the strong force and the weak force.

Therefore, solving the mass gap problem is one of the keys to solving the grand unified theory.

(End of this chapter)