walk into unscientific

Chapter 633 History: Fly, Fly, Fly ([-]-word chapter!)
Degeneracy and vacuum?
At this moment.

The side of the operating table.

Hearing the four words that came out of Xu Yun's mouth, Zhao Zhongyao's brows, which were already very happy, were raised again very obviously.

Degenerate vacuum.

It is not difficult to see literally that this concept can be divided into two parts:

degeneracy, and vacuum.

Well known.

The word vacuum is somewhat similar to the second-level page, and it can also be divided into two third-level pages, that is, two scenarios:
One is the vacuum in the macroscopic physics.

The second is microscopic or vacuum in the quantum concept.

Among them, the former is easy to understand, referring to the empty space or someone not wearing underwear.

But the vacuum in the quantum concept is much more complicated.

The concept of quantum vacuum can be traced back to 20 years ago, around 1940.

At that time, the world war was in full swing, and the world of physics was developing quietly and rapidly under the flames of the war.

At that time, Dirac used the Dirac equation to establish a model of the hydrogen atom. The model consisted of a Coulomb potential in which a proton and an electron attract each other.

mentioned earlier.

The Dirac equation describes the behavior of fermions, of which protons and electrons are also two typical representatives.

The so-called typical naturally means that their research has been very in-depth and transparent.

Therefore, physicists also think that the energy level of hydrogen atoms can be well understood through the Dirac equation. After all, there are no secrets about the particles that make it up.

At that time, the physicists in Milan were even opening champagne while cheering the emergence of a new model - the three round things of protons, electrons, and hydrogen atoms added up to three to zero. How could this be a loss?

until
A man named Willis Lamb from across the sea conducted an experiment at the University of Liverpool, which broke all the peace of time without warning.

1947 years.

When Lamb was doing research on the fine structure of the hydrogen spectrum, an abnormal result appeared in the experiment:
氢谱在2S1/2和2P1/2两个量子能级有着轻微的能量差异。

According to the Dirac equation prediction, the energy of these two quantum states should theoretically be the same.

However, the energy difference discovered by Lamb was approximately around 1028MHz, and after repeated confirmation, the possibility of experimental error was ruled out.

Lamb later named this difference the Lamb shift, and he also won the 1955 Nobel Prize in Physics for this discovery.

The Lamb shift shows that the Dirac equation is not perfect under delicate conditions, and the subtle energy level difference implies that physicists still have something to add.

And this content is.
Quantum vacuum – or vacuum fluctuations.

That is to say, there is not nothing in the category of quantum vacuum, but there is an inestimable field, that is, energy.

It is a collection of different virtual and real particles that appear and disappear continuously. Such extremely short-lived particles go unnoticed 99.99999% of the time, but in some cases the vacuum force may have measurable effects.

For bosons, this energy is positive.

For fermions, this energy is negative.

That is, the quantum vacuum is empty but not empty. This is an important conclusion of quantum field theory, and the so-called Casimir force is also the category of this part.

Of course.

The above is Xu Yun's understanding when he traveled through time, which is the year 2023 in later generations. It is much deeper and clearer than today.

For example, later generations also defined another related concept called vacuum decay.

Its content is this:

Everything in the universe will spontaneously tend to the state of the lowest energy, similar to water flowing down.

So if the cosmic vacuum is not in the lowest energy state, then under certain conditions, the cosmic vacuum will "fall" to a lower energy state.

Assuming that the vacuum of the universe is not in the lowest energy state, then we can call it a "pseudo-vacuum".

Corresponding to this is the cosmic vacuum in the lowest energy state, which can be called "real vacuum".

for example.

There is an iron ball halfway up a mountain.

Although it has a tendency to continue to fall, it will not continue to fall because of the terrain blocking it halfway up the mountain.

But if you use a certain force to push the iron ball over the terrain that blocks it, it will inevitably continue to fall.

The same is true.

If enough energy is injected into the pseudo vacuum.

Then the false vacuum can break through the energy barrier, and then fall to the real vacuum, so the vacuum decay takes place.

To know.

The energy released by vacuum decay is actually very, very large, enough to make the pseudo-vacuum around it break through the energy barrier.

under these circumstances.

If vacuum decay occurs in a certain region of the universe, the energy released will cause vacuum decay in the surrounding space.

And the vacuum decay occurs in the surrounding space, which will cause more space to also undergo vacuum decay, infinite nesting dolls.
Eventually, this will form an unstoppable chain reaction, and the result will be a spherical space composed of "real vacuum" that expands rapidly in the universe.

And in theory.

The expansion speed of this spherical space is actually the speed of light.

At the same time, the "surface" of this spherical space is filled with huge energy.

Therefore, wherever it passes, many celestial bodies in the universe will fall apart, and the physical constants will change greatly.

See here.

Do some students feel that this description is somewhat familiar?

Does it feel like a black hole is similar to this?
It's a pity that you are familiar with it early-black holes are not actually a model of vacuum decay.

But
The ending of a certain fisherman's next book has something to do with vacuum decay. I can still see you at the end)
All right.

The line of sight returns to reality.

And except for the vacuum.

Another concept of degeneracy is relatively simple.

The eigenvalue of a Hermitian operator has multiple eigenstates, which is degeneracy.

For example, the orbital of the hydrogen atom mentioned above has two degeneracy of angular momentum and spin.

Give another example.

Students who have read online novels should all know this.

An internet author may have several books under his pseudonym.

Although the grades, word counts, and content of these books are different, they are all created by the same author on the same website. These books are degenerate pen names.

Therefore, degenerate vacuum refers to the vacuum prototype of an eigenstate, that is, another state transformed when the vacuum is non-invariant to the system group G.

This state undergoes a transformation of the cylindrically symmetric ground state, which eventually leads to the appearance of a scalar boson.

If the sentence above is still incomprehensible, let’s still use online novels as an example:
He is also a writer named Daily Geng Thirty Thousand Fishing Guy. There are two books under this pseudonym:

One is called "Handbook of Conquest of Different Worlds".

The other is called "Technology Empire Begins with Elimination of Cockroaches".

The protagonist of the previous book is called Wu Fan, and the protagonist of the latter book is called Donkey.

When you talk about the vacuum state of "Handbook for the Conquest of Another World", the characters you think of must be Wu Fan, Cao Yi, and Lin Ziming, that is, gauge bosons with vectors.

And if you are talking about the degenerate vacuum of "The Empire of Technology Begins with Cockroaches", then the characters discussed will naturally become scalar bosons such as donkey, axe, and Lao Su.

That is to say, the role corresponding book=gauge/scalar boson is corresponding to the degenerate states.

As for the different characters in the book, they are different types of gauge bosons, such as photon gluons and so on.

"."

Then Zhao Zhongyao was silent for a while, picked up the ballpoint pen and turned it around in his hand for a while, and said to Xu Yun:
"Xiao Han, I have a question. If a degenerate vacuum is established, what will its system look like?"

"After all, a degenerate vacuum is just a state, and the principle supporting the existence of this model is the real core."

"It's like we said that after the invention of the perpetual motion machine, we can travel across the stars. Compared with the following behaviors, how to come up with the design model of the perpetual motion machine is the key point - for the existing framework system, the perpetual motion machine is not a good idea at all. Things that might come up.”

Xu Yun smiled understandingly when he heard the words, he naturally knew this truth very well:

"Director Zhao, you are right. Compared with the degenerate vacuum model, the deeper principles are obviously the key."

"As for this principle, Director Zhao, have you ever heard of spontaneous symmetry breaking?"

"Spontaneous symmetry breaking?"

Zhao Zhongyao blinked, and soon thought of something:
"Is that the theory of superconductivity? It seems that some kind of material properties are spontaneously changing from a symmetrical state to an asymmetrical state?"

Xu Yun nodded vigorously:

"Yes."

Spontaneous symmetry breaking.

Its English name is called Spontaneous symmetry breaking, and the abbreviation is somewhat subtle SSB.

This is a very common phenomenon in physics. Its mathematical principle is based on the gauge theory of the continuous group SU(2). The concept was jointly proposed by Yang Lao and Mills 7 years ago.

This concept is actually quite easy to understand. Have you eaten or seen the copper hot pot in Yanjing?

Suppose a small ball rests on the top of the copper hot pot, then the small ball must be unstable, and will fall into the pot along the furnace core when disturbed.

before the ball falls.

Any position in a circle of the copper pot is equal, and the system has rotational invariance, that is, it is the same and symmetrical no matter how it is rotated.

But
It's different when the ball falls.

In the end, the ball will only be stable at a certain position. At this time, including the ball, the system is no longer invariant to rotation.

This is the occurrence of spontaneous symmetry breaking - the ball falling is "spontaneous", and the lack of rotation invariance is breaking.

Zhao Zhongyao was not unfamiliar with this concept, so he quickly made a guess:
"Spontaneous symmetry breaking. Xiaohan, could it be that there is a term in the pull density that obviously breaks some kind of symmetry, such as the mass term of the Dirac field, thus breaking the positive symmetry?"

Xu Yun:

"?!"

Then he didn't wait for Xu Yun to answer.

Zhao Zhongyao touched his chin again, picked up a pen and calculated on paper:

"I remember that the expression for superconductivity should be. If it is introduced into particle physics, this should be a spontaneous breaking of local symmetry."

"Consider the particles in a one-dimensional space, then L=12(μσ)212m2(σ)2"

After a few minutes.

Zhao Zhongyao suddenly let out a light surprise:
".Um, isn't that right?"

"There is no column symmetry in the stable vacuum state, so there are infinitely many degenerate ground states under transformation, or there is a non-zero mass field?"

After hearing Zhao Zhongyao's words, Lu Guangda, Zhu Hongyuan and others on the side couldn't help but quickly walked to him.

Seeing this, Li Jue glanced at the empty surroundings, and followed suit.

"There really is a non-zero mass field."

Hu Ning looked at the results for a while with the arithmetic paper, and as always, he considered his own problems first:
"Old Zhao, could it be that you made a mistake in your calculation?"

Zhao Zhongyao immediately shook his head, pointed at the paper and explained:
"It's impossible, not to mention how complicated the commutation process of Lie algebra structural constants is. You should look here first."

"You see, there is an independent supplementary term with the square root of 2 in front of this non-zero mass field, and this alone is enough to prove the existence of the non-zero field."

"Even if my calculation is wrong, it can only be the specific expression of the non-zero field, not its existence."

"Speaking of Lao Hu, your pessimistic personality should also be changed. At least you should be more confident. Why do you always doubt yourself first?"

Hu Ning shrugged and said nothing.

no way.

It's not that he's not confident, it's just his personality.

When he encounters an abnormality when solving problems or doing experiments, he will first consider whether there is something wrong with him. Only after eliminating his own fault will he be able to think about the next step.

This kind of mentality cannot be considered pessimistic. It should be said that it is somewhat stable?

Seeing that these big guys encountered another problem during the discussion, Xu Yun couldn't help but cough lightly and prepared to give a specific answer:
"Several comrades, I have a message, please listen carefully"

As a result, before he finished speaking, Zhao Zhongyao and others turned their heads at the same time, and Qi Qi interrupted him:
"Xiao Han, hold your tongue! Let us think for ourselves!"

Lao Guo even handed Xu Yun a cattail leaf fan, with an obvious meaning - just stay where you need to cool off.

Xu Yun:

"?????"

Unload the mill and kill the donkey, this.
Then under Xu Yun's confused expression, many big guys turned their heads again and discussed the issue again.

Lu Guangda pondered for a moment, then took the initiative to say:

"Director Zhao, if it's not a miscalculation, then it's something that happened in group theory."

"In that case, I have an idea. Can we manually add an obvious defect to deform the vacuum?" He said.

Lu Guangda also picked up the pen and drew a figure on the paper again.

how to say
Let's take an example that isn't very elegant.

The original image drawn by Zhao Zhongyao is a butt, the left and right sides are symmetrical, and the buttocks on the left and right sides are the lowest points of energy.

However, the image drawn by Lu Guangda is much "crooked", and the two sides are obviously not equal - the right side is obviously bigger than the left side.

But soon.

Zhu Hongyuan shook his head and denied Lu Guangda's guess:

"It's unlikely, Comrade Guangda, the artificial correction is still too obvious, and this discrete model should not be able to generate a continuous field."

Lu Guangda thought for a few seconds, then nodded himself.

Also.

His idea has obvious optimization intentions, and the behavior of particles is obviously unlikely to be changed according to this idea.

This is like you want to buy a 500 million house, but there is only 2 yuan in the bank card.

As a result, you use P-map software to change it to 500 million, which seems to be enough to buy a house, but in fact it is of no use at all.

Unless you are so lucky that there is a bug in the banking system when you transfer the money, there is no way this house will fall into your hands.

Not to mention that this discrete model really cannot deduce a continuous field. It is better to use Feynman's path integral quantization.
However, Lu Guangda was not discouraged by this. The spontaneous symmetry breaking was related to his friend Yang Zhenning, so this big guy seemed particularly active at this time.

I saw him staring at the formula for a while, and then came up with another idea:
"Since manually adding obvious breaking terms does not work, is it possible that the combination of gauge symmetry and spontaneous breaking caused this mass field to be 'eaten' by the zero-mass gauge field?"

"For example, the gauge symmetry of the electroweak interaction is SU(2)L×U(1). The Yukawa coupling is introduced on the premise that the gauge symmetry of the Lagrangian quantity is not broken, so that the mass of the meson conforms to the derivation."

This time.

Zhao Zhongyao and others no longer refuted Lu Guangda, but fell into deep thought at the same time.

Yukawa coupling.

It refers to the yukawa coupling, proposed by Yukawa Hideki of Neon.

This person is one of the founders of modern neon physics and is an unignorable figure in the entire history of particle physics:

He was the first neon man to win the Nobel Prize. He proposed the famous Yuchuan coupling and Yuchuan coupling potential, and also predicted the existence of π mesons.

However, due to this person's right-wing political leanings, Xu Yun has always been disgusted with this person's open attitude, and he has to diss him once to write a book.

To what extent is this person right?
for example.

At the awarding ceremony of the Nobel Prize, he grandly called a certain war a "war of loyalty", saying [There are still newly-established unstable regimes around the neon, and this unstable trend should be contained for the sake of peace. trend】.

By the way.

The time when Hideki Yukawa said this was December 1949, 12, and it is self-evident who he was referring to.

Compared with his contemporary Sakata Shoichi, a true pacifist and friend of China, Yukawa Hideki is on a par with heaven and earth - even though Sakata Shoichi did not win the Nobel Prize academically.

Later, Yukawa Hideki also became a toilet seat brand, and the manufacturer was a domestic company in Pengcheng. It can be regarded as some kind of retribution.
Of course.

Just like Song Huizong was also a master of calligraphy.

No matter how bad Yukawa Hideki's character is, his academic achievements cannot be ignored.

For example, Lu Guangda's idea at this time is really impossible without the introduction of Tangchuan coupling or the concept of meson.

Because it is analyzed according to normal theory.

Mesons in atoms should not have mass, otherwise the inertial motion of the meson mass will break up the atomic structure and cause the collapse of the physical building.

It is the existence of Yukawa coupling that allows this situation of mesons to be explained:
When the meson is inside the atom, it will move along the structure of the eight-dimensional atom as a point space, and it can obtain mass independently after leaving.

thought here.

Zhao Zhongyao also had an idea.

Yes
The gauge field belongs to the gaugeable field theory.

According to mathematical definition.

As long as a certain concept is a field theory, its Lagrangian is invariant under certain types of group transformations.

Therefore, if gauge symmetry and spontaneous breaking are combined.
Then there may be some changes in the longitudinal degree of freedom or transverse degree of freedom of the gauge field
Think about it.

Zhao Zhongyao picked up the pen again.

This time, he was going to deduce from the simplest field.

That is.
Electromagnetic field of SU(1).

Same as before.

Zhao Zhongyao first wrote down a Lagrangian, which is the standard first step in almost all particle physics derivation processes:
L=1/2()mmλ3λ44+m24λ。

Next consider a scalar field with two components:
=[1/2].

Then,
拉格朗日量就变成了L=1/2()+1/2m2λ4(2)——这样的势看起来就和之前提到的铜火锅一样了。

And because O(2) and U(1) are local isomorphisms, the symmetry of U(1) is also continuous symmetry.

“接着令=12(1+i2)，则有=12(12+22)，拉格朗日量变为：(6)L=+m2λ()2，它在 U(1)变换→eiα下不变，因此具有连续的 U(1)对称性.”

“在通过极坐标的方式把分成=ρeiθ.拉格朗日量为L=(ρ)2+ρ2(θ)2+m2ρ2λρ4，真空期望是ρ=ν=m22λ，θ=0做变换ρ→χ+ν”

“拉格朗日量变成L=[(χ)22m2χ24mλ2χ3λχ4]+m22λ(θ)2+(χ2+m2λχ)(θ)2”

"The first part is the kinetic energy term of χ, the mass term, and self-coupling, and the third part is the interaction of the two fields."

"And the second term is just the kinetic energy term of θ and has no mass, so it is a massless boson produced by the spontaneous breaking of U(1) symmetry"

"Then the next step is to consider a vector boson that has no mass, and its Lagrangian L=14FμνFμν"

"Coupling it with the scalar field above, replacing the ordinary derivative μ with a covariant derivative Dμ=μiqAμ, where Aμ is the gauge potential of the original massless vector boson."

"And then so and so and so and so"

Looking at Zhao Zhongyao writing quickly on the paper, Xu Yun's face looked a little dull.

Poor god.

This time his idea was just to let Zhao Zhongyao discover Goldstone's theorem.
The result was unexpected.

Seeing that Xu Yun kicked Shi Shi not hard enough, Zhao Zhongyao and the others grabbed Xu Yun by the collar and threw him back, then went up and kicked him hard.

Now the fun will be big
Even in a sense, this jio is even more outrageous than dark matter.

mentioned earlier.

In the early days of particle physics there was a model called the Southern model.

It was proposed by Yoichiro Nambu, the neon man, who was considered one of the top 1 living physicist contenders when he was alive.

Although objectively speaking, he was half a stature behind Yang Lao Weinberg and the others, but his ability can be seen from this.

Just like the Huaxia people have blessings to Mr. Yang, many Nihong people also firmly believe that Nambu Yoichiro can be ranked first in the world when he is alive.

Of course.

There are also many people in Yoichiro Kuro Nanbu, which is the same in any country.

In this day and age.

The concept of spontaneous symmetry breaking is popular in the field of superconductivity, and Nambu Yoichiro took the lead in introducing it into particle physics at the end of this year, which allowed him to discover the phenomenon of spontaneous symmetry breaking in strong interactions—accurately speaking is the spontaneous breaking of chiral symmetry.

At the same time.

A year later, Geoffrey Goldstone of the United Kingdom studied the connection between steady-state solutions through U(1) phase transformation and proposed the massless Goldstone mode.

Finally, the combination of the two leads to the South-Goldstone theorem.

The content of the South-Goldstone theorem is very simple, that is, the zero-mass boson particle must exist after the continuous symmetry is broken spontaneously.

This particle is called a Goldstone boson. For example, Hideki Yukawa's π meson corresponds to a Goldstone boson with approximate chiral symmetry breaking.

But there is a fatal problem with the South-Goldstone theorem, that is
The mass of gauge particles is a property that is not allowed by symmetry.

Because in the spontaneous symmetry breaking + Southern-Goldstone theorem, the gauge field still exists.

This also means that local gauge symmetry is preserved—different gauges can be related by a Lie group transformation.

It’s just that the overall gauge symmetry of the Lagrange quantity is due to the non-zero expectation of the field in the vacuum (the second sentence of Zhao Zhongyao’s calculation), and the quantum field theory does not choose the linear superposition of degenerate states as the ground state, which leads to the Lagrangian density The gauge symmetry is broken after selecting a specific ground state. That is, the new Lagrangian density obtained by perturbing around the ground state does not have the overall gauge symmetry.

But due to the local gauge symmetry, the gauge field still exists.

Give another example.

Room temperature superconductivity is very popular recently.

It is precisely because of the violation of U1 caused by Bose condensation that superconductors will change the Maxwell equations of photons, thus showing the Meissner effect.

Of course.

The South-Goldstone theorem, while problematic, is a good primer for rabbits.

According to Xu Yun's plan.

After understanding the South-Goldstone theorem for a certain period of time, about two years or so, the rabbits will crack its drawbacks and get in touch with an advanced version of the concept:
Higgs mechanism.

That's right.

Higgs mechanism.

This well-known physics framework is just an optimization of the South-Goldstone theorem.

I won’t talk about the specific derivation process of the Higgs mechanism. After introducing it, many people guess that they have to grow their brains, so let’s directly explain its physical meaning:
in the standard model.

Except for the three weakly interacting gauge bosons and other basic fermions except neutrinos, they are all directly assigned mass through the Higgs mechanism.

At the same time, if the W and Z gauge bosons directly write out the mass term, it will violate the gauge symmetry, so they also need the Higgs mechanism to be established.

If elementary particles are human beings, then the Higgs mechanism is clothing.

True.

It doesn't matter whether people wear clothes or not in primitive society, but what would it be like if everyone didn't wear clothes at the level of modern society?

It's exciting, but social order and normal production and life are definitely out of the question.

The importance of the Higgs mechanism can be seen.

It's just that in the original history, the development process of the Higgs mechanism was very complicated, and it could even be said to be a bit bumpy.

At that time, after Goldstone's theorem was proposed in 62, it was very controversial, and even encountered death threats.

Because theoretically, the case of zero-mass particles is different from the case of heavy-mass particles. Zero-mass particles are easy to make, or their existence can be inferred from the lack of energy or momentum.

But the physics community at that time could not find any zero-mass particle cases, so this theory was also opposed by Walter Gilbert, the Nobel Prize winner in chemistry.

Then five years later.

Higgs came up with the Higgs model.

He showed that linking the theory of local gauge invariance with the concept of spontaneous symmetry breaking in a particular way, gauge bosons must gain mass.

Another year.

Weinberg and Abdul Salam independently applied the Higgs mechanism to break electroweak symmetry, and believed that the Higgs mechanism could be incorporated into Glashow's electroweak theory.

However, these epoch-making papers on the spontaneous breaking of gauge symmetry did not receive the attention of the academic community at first.

Because most physicists believe that non-Abelian gauge theories are dead ends and cannot be renormalized.

This situation would not turn around until ten years later, when Gerald T. Hooft (the little old man who appeared at the original dark matter press conference) published two papers:
He proved that the Yang-Mills theory can be renormalized, both for zero-mass gauge bosons and for massed gauge bosons.

Physicists have since embraced these theories, formally bringing them into the mainstream.

So why it is said that Te Hooft indirectly made Weinberg, and Weinberg indirectly made Yang Lao, the reason is here.

As for the particle that can completely prove the Higgs mechanism, which is currently the only scalar boson, it will not be truly discovered until 2012.

Moreover, the mass of this thing is 125GeV, and the required collision capability is 300GeV or higher. No matter how European you are, you cannot collide it with 80MeV equipment.

Therefore, Xu Yun has been in a semi-entangled state with the Higgs mechanism, after all, the current history has been filled by him.
when he wanted to.

If the rabbits can think of the Higgs mechanism three to four years or even five or six years later, it may be better.

After all, Xu Yun was not sure whether the neutron bomb could explode at that time, but the atomic bomb and hydrogen bomb must have exploded successfully, and the load on various equipment should be a little easier.

Although the cost of doing so is mostly that this part of the international discourse power will be lost, and two or so awards will be missed.

But the stratoton model, that is, quarks can give rabbits the right to define at least 44 types of particles, and it is acceptable to give up the Higgs mechanism.

Unexpectedly, Zhao Zhongyao said that he could accept the eggs, I want them all!
It can only be said that reality is much bolder than Xu Yun imagined.
Just that way.

Rabbits will definitely have to put a lot of effort into the accelerator.

Based on the current domestic situation, there is a situation that must be optimized by Xu Yun again.

And if this move comes out, then the copy itself will really be involved in all directions and 360 degrees.
At the same time when Xu Yun's heart was complicated.

The capital thousands of kilometers away.

A green leather train also set off quietly.

It needs to be mentioned.

Except for some goods, the car only contains
a passenger.

Note:
Nine thousand word chapter, ask for a monthly ticket! ! !
(End of this chapter)