Although it is a pity that the technology on the Wukong dark matter detection satellite has not been applied to the Large Strong Particle Collider, Academician Chang Jin's words have given Xu Chuan enough reminders to remind him of something else.

In his previous life, when he was doing experiments at CERN, the data information he found was incomplete for the discovery and detection of inert neutrinos.

Of course, this incompleteness is not insufficient to verify the existence of inert neutrinos and dark matter.

Rather, the information of these particles is still as much as the discovery of inert neutrinos in this lifetime, and a small part of it cannot be determined.

If we say that the discovery of inert neutrinos on the side of Euratom a few years ago only found the properties of the particles in their regular state, and the remaining properties of dark matter were not detected at all;

Then in the previous life, I saw some of the dark matter properties, and I was able to judge that it belonged to dark matter, but it was not comprehensive.

It's just that at that time, he and many physicists were so excited by this great new world and new century that they didn't pay much attention to these details.

Now that you think about it, this probably has something to do with the detector technology of CERN's upgraded high-brightness LH-LHC collider.

As Academician Chang Jin said, the observation of dark matter and dark energy by the collider detector is mainly to search for the energy and momentum loss signals generated by the dark matter during the annihilation and decay.

Perhaps this is the route taken by CERN in the previous life when it upgraded and optimized the detector.

That's why when he discovered the search for dark matter, he could only confirm a part of the information.

Theoretically, charged particles (mainly positive and negative electron pairs, neutrinos, photons, and charged particles, etc.) are produced by the annihilation of dark matter.

The signals produced by these particles cover the entire electromagnetic band, and there are two main types of signals.

One is the synchrotron radiation of charged particles in the local magnetic field, which is in the radio observation band;

The other is the inverse Compton scattering of high-energy electrons and CMB photons, and the scattered photons are generally in the X-ray band.

Due to uncertainties such as dark matter particles, dark matter density profiles, and the magnetic environment, dark matter

Indirect detection requires a combination of multi-band features to give further limits to dark matter.

Therefore, by searching for the energy and momentum loss signals generated by dark matter during its annihilation and decay, it is theoretically impossible to see the full picture of dark matter.

And dark matter does not participate in electromagnetic interactions, does not participate in strong interactions, or does not carry electric and color charges.

So its main component cannot be any kind of particle in the Standard Model, nor can it be a black hole formed by the collapse of a star, it is a substance that has never been discovered.

However, dark matter requires stable, uncharged, and weak interactions, so most of the elementary particles in the Standard Model of particle physics cannot constitute dark matter.

If possible, the only possible neutrinos among conventional particles.

However, since neutrinos can only constitute so-called hot dark matter, which is inconsistent with the observation of the large-scale structure of the universe, conventional neutrinos are also excluded.

The particles that make up dark matter in this way are necessarily new particles that are beyond the Standard Model.

The inert neutrino he discovered does not belong to the regular neutrino form, so it belongs to one of the warm dark matter.

However, even if an inert neutrino is not a conventional neutrino, it still has some material properties in the normal state.

Using this, he could theoretically use the collision control of the high-energy collider to forcibly annihilate the inert neutrinos to form two other particles, and thus observe various information such as their mass.

Perhaps, he knows where to reconstruct the collider detector.

Thinking of this, Xu Chuan's eyes suddenly brightened.

He knows what to do!

On the other side, when Xu Chuan was deep in thought, Academician Chang Jin took a small sip of a teacup.

In the state of Xu Chuan on the other side, it was obvious that he had some thoughts to think about, so he didn't bother, and waited quietly until he came back to his senses.

Looking at Xu Chuan with an excited look on his face, Chang Jin smiled and asked curiously, "Academician Xu, does this have an idea?" ”

Xu Chuan nodded and said with a smile: "I do have some theoretical ideas, but they still need to be refined, as for whether they are useful, we may need to wait for the collider and the detector to be prepared." ”

For unestablished scientific research theories, even if he is sure, he will not say it too surely.

Just as many people in the academic community think that the papers he threw on Arxiv can be regarded as official journal papers, no matter what the outside world says, he never thinks that he will not make mistakes and that all the papers he publishes are correct.

Especially at his current level, the more critical the research, the more cautious he must be in his words and deeds.

On the other side, hearing Xu Chuan say this, Chang Jin asked curiously with some interest on his face, "If it's convenient, can you talk to me?" ”

Xu Chuan smiled and said, "What's inconvenient, speaking of which, this inspiration was given by you, Academician Chang." ”

After a slight pause, he sorted out his thoughts and continued: "In the previous inert neutrino, it is obvious that similar characteristics have appeared. However, compared to theoretical dark matter, inert neutrinos have some more conventional properties. ”

"Therefore, by using this part of the property, tracking it, and then judging the properties of dark matter that can be transformed into two other particles under the condition of high-energy collision, continuous experiments can find out and deduce the 'dark' nature of dark matter little by little."

"However, theoretically speaking, it is very difficult to accurately determine the data of inert neutrino collisions during the collision of high-energy particles, which may require trillions or more collisions before we can find that trace of use."

After listening to Xu Chuan's explanation, Chang Jin thought for a while, and then said: "According to this line of thinking, enough collision data may be able to completely search for dark matter particles, at least the complete information of inert neutrino particles. ”

"This is definitely a groundbreaking discovery for the physics community."

"It's just that to do that, you have to make an inert neutrino and find a way to make it collide in the collider, and you have to eliminate the effects of other particle collisions."

"This difficulty is not ordinary."

As the chief scientist of the Dark Matter Particle Detection Satellite, he easily understands this new approach.

Theoretically, it is possible, and the data can be collected more comprehensively, but it is really not very difficult.

Whether it is to find a way to create an inert neutrino, or to guide it to collide with a collider, or to eliminate the interference of other particles, it is not easy, and it can even be said that it is a difficult task.

Xu Chuan said with a smile: "If you can observe the complete information data of inert neutrinos, no matter how much you pay, no matter how difficult the problems you encounter, it will be worth it." ”

After chatting with Academician Chang Jinchang for a while about various particle detection technologies, Xu Chuan couldn't wait to return to the office.

For the exploration of dark matter, he already has a general direction.

The next step is to improve the theory as much as possible.

It is hoped that he will be able to solve this work smoothly before the conference on high-energy physics convened by the Physical Society.

And so the days passed.

It was soon mid to late May.

These days, Xu Chuan has not gone to the Xinghai Research Institute again.

For more than half a month, he devoted himself to perfecting the theoretical basis for the detection of inert neutrinos and dark matter at NTU.

With the help of quantum field theory, the rate of change of the number density of particles in the codynamic volume a, 1/ad/dt(n1a)=∫··· ∫∏j=1(dpj/(2π)δ+（pj-mj）)（(2π)δ（p1+p2-p3-p4）∑”

"In the codynamic volume, the particle number density does not dilute with expansion, and the right side of the equation can be divided into two parts, where the dark matter particles produce the scattering cross section of the annihilation process, 1/ad/dt(n1a)=∫··· ∫∏j=1(dpj/(2π)δ+（pj-mj）)”

"P is the four momentum of the individual particles involved in the scattering process, |M|is the scattering amplitude. ”

"The second part is the equilibrium state statistical distribution of the energy of each particle."

"That is, the rate of change in the abundance of dark matter is equal to the difference between its generation section and its annihilation cross-section, and the physical meaning of the cross-section is the probability of the reaction occurring."

“.”

Lines of calculations were written down in Xu Chuan's hands.

The Boltzmann transport equation is an important part of the exploration of dark matter.

It describes the evolution of the abundance of dark matter particles Y with the "mass-temperature ratio" x, and the parameters in the equation are determined by the specific particle physical model.

However, if you want to find the data you need from the countless collision information data, it is completely impossible to do it by manpower.

At this time, the importance of mathematical tools is vividly reflected.

As long as the lowest calculation formula can be made, then mathematics can use computers and software to establish a mathematical model, and use the mathematical model to find the required data from trillions of pieces of information.

The last symbol fell from the signature pen in his hand, Xu Chuan put down the pen, stretched out with a long sigh of relief.

It took him more than half a month to finally refine the ideas in his mind, and formed a set of logical self-consistent theories, as well as a set of mathematical model basic formulas for calculating the transformation particles after the annihilation of inert neutrino collisions from a large number of parameters.

All that's left is to turn these theories into actual devices and mathematical models.

Looking at the manuscript paper in his hand, the corners of Xu Chuan's mouth hooked a magnification.

It looks like I'm going to have to trouble the senior sister again.

At the foot of the Purple Mountain, not far from the Chuanhai Materials Research Institute, under the building of Chuanhai Network Technology Co., Ltd., Xu Chuan found Liu Jiaxin, who was busy with his work in the office.

With a smile on his face, he knocked on the door.

In the office, the senior sister who was studying something was awakened by a knock on the door, and when she looked up and saw him, she was obviously stunned for a moment, and then a smile appeared on her face.

"Why are you here?"

Xu Chuan stepped forward and said with a smile, "Come and see you." ”

Hearing this, Liu Jiaxin's earlobes suddenly turned red, Xu Chuan didn't notice it, and his eyes fell on the desk with a smile.

On it, there were dense calculation formulas on the scattered manuscript paper, and his good eyesight allowed him to clearly see some of the mathematical formulas on it, which looked somewhat familiar.

Glancing at the manuscript paper, he asked curiously, "Are you studying mathematics?" ”

Liu Jiaxin nodded, pulled a strand of hanging green silk behind her ear, and replied: "Well, about some mathematical problems in artificial intelligence, I want to see if I can solve them." ”

For artificial intelligence, the underlying logic algorithm is undoubtedly inseparable from mathematics.

Although Princeton's computer science discipline is not among the top ones, the field of mathematics is something that no other school can keep up with.

Hearing this, Xu Chuan immediately became interested: "Let me take a look?" ”

Liu Jiaxin nodded, sorted out the manuscript paper on the table and handed it over.

Xu Chuan took the manuscript paper and flipped through it.

"Large integer factorization algorithm based on decomposition basis."

The title on the manuscript paper caught his eye, and he was stunned.

This title?

After thinking for a while, Xu Chuan raised his head violently, his eyes fell on the face of the senior sister, and he couldn't help but swallow his saliva and asked, "Are you studying the NP=P conjecture?" ”

It's no wonder that when he glanced at it before, he always felt that the formula on the manuscript paper was very familiar.

The big positive integer factorization problem is part of the NP=P conjecture of the seven millennial problems.

To be honest, he really didn't expect Liu Jiaxin to be researching this kind of thing.

Because for the mathematical community, there are many things related to the field of artificial intelligence.

Whether it's linear algebra, calculus, probability theory and statistics, or discrete mathematics, they all influence the logical algorithms at the lowest level of computers.

However, if we want to say that the most critical and influential is definitely the NP=P conjecture.

It is the only one of the seven millennial puzzles related to computer science, and its status in the mathematical community and computer science naturally goes without saying.

Of course, the difficulty goes without saying.

Being watched by Xu Chuan's blazing gaze, Liu Jiaxin nodded a little embarrassed.

After a few years at Princeton, she learned not only computer science, but also a lot of mathematics. It's just that she hasn't shown much of her math ability all this time.

Especially after taking over Chuanhai Network Technology Co., Ltd., in order to build a security protection platform, there is little time to study mathematics.

It wasn't until last year that she split her time and energy into math.

The NP=P problem was one of the mathematical directions she studied when she was a PhD student at Princeton, and now she picks it up again, with the ultimate goal of studying artificial intelligence.

(End of chapter)