Shulou(Shulou.com)11/24 Report--

This article comes from the official account of Wechat: back to Park (ID:fanpu2019). The authors: Liu Yuanxing (Ph.D. in the School of Humanities, University of the Chinese Academy of Sciences) and Guo Rongzhen (Ph.D. in the Institute of theoretical Physics, CAS)

The 2022 Nobel Prize in Physics was awarded to three physicists engaged in experiments related to quantum entanglement. The "Bell inequality" was directly mentioned in the reasons for the award, which brought Northern Ireland physicist John Bell back to people's vision. Bell is famous for his research on the basis of quantum mechanics, especially the Bell theorem and Bell inequality, which tells us that the microscopic world of matter follows unimaginable laws, which has become the basis of the field of quantum information. In fact, these achievements that made him go down in history are "amateur". He has worked at CERN for a long time all his life, made outstanding contributions to accelerators, nuclear physics and elementary particles, and is also known as the "saint of CERN". In the year when Bell's inequality won the Nobel Prize, we would like to commemorate Bell's extraordinary life.

The 2022 Nobel Prize in Physics was awarded to three physicists, Alain Aspect, John F. Krause and Anton Zeilinger, for their achievements in entangled photon experiments and Bell inequality experiments. Among them, Bell inequality is undoubtedly one of the most important foundations in the work of these scientists, but who is Bell? He is not the father of the telephone as we know him, or Alexander Graham Bell, known as Bell Labs, but John Stewart Bell.

Photo 1 John Bell (John Stewart Bell,1928.7.28-1990.10.1) Photo Source: Wikipedia's turbulent and happy childhood in 1928, Bell was born in Belfast, the capital of Northern Ireland, a city with a long history and a glorious past. Belfast benefited from the rise of the Industrial Revolution in England in the 1860s and became the world's largest producer of flax products by the early 19th century. It also has the world's leading Wolf shipyard (Harland and Wolff Shipyard), where the famous Titanic was forged. But after World War II, the city began to go downhill, and because of the ownership of Northern Ireland, the city was plunged into great chaos, dealing a blow to both economy and politics. Bell was born in such an era.

Bell is the eldest son of the family. He has a sister and two younger brothers (figure 2). His father, Jackie, is an ordinary worker, and his mother, Annie, is a shop clerk. Both of Bell's parents received only a very basic education. Bell's father came from a mediocre family, and his mother came from a prominent family-Bell's grandfather was a very successful businessman. Her grandfather deeply influenced Bell's mother. Anne was a good housekeeper. Even though she was living in poverty, she was always able to increase income and cut expenditure, making the family full and happy. She once bought a used bike for her children and recalled: they ride as fun as new [1]. Through this incident, the author speculates that the reason why Bell liked riding motorcycles very much in his youth was influenced by the environment where he lived at that time (where young boys loved to ride motorcycles [2]). It is also affected by the "bicycle incident" of childhood. Since then, Bell has been growing a beard, it is said that because of a serious motorcycle accident, he left a deep cut near his mouth, which was covered with a thick beard.

Bell has been different from other people since he was a child. his family is Anglican and there are many Catholics around him, but Bell insists on his pursuit of truth, even though religion can bring real benefits (for example, in school, children who believe in Ireland are more likely to join the football team [4]) and do not believe in any religion. But he is a staunch vegetarian. According to Bell's wife, he became a vegetarian under the influence of the famous Irish playwright George Bernard Shaw. Bell's mother Annie also recalled such a story: one Christmas, Bell smelled roast turkey and commented, "I smelled a dead body burning." Perhaps this compassion for animals is another reason why Bell became a vegetarian.

Figure 2 A family outing: in the top row from the left are Mrs Brownlee's grandmother, sister Ruby Bell and mother Annie Bell, and the next row from the left are brothers David, Bell and brother Robert Photo Source: reference [6] Bell has been intelligent since childhood, proficient in cards and chess, and likes to show what he has learned He always talks about his knowledge to his family and even strangers. Although not everyone liked his personality, his parents were pleased with Bell's ability to express himself. In addition, Bell's hands-on ability is very strong. He used to make a pinhole camera from a mustard can blackened inside with a small hole in the top of the lid, a piece of photographic paper, in a dim red room (bathroom).

Bell has been among the best in his grades since he went to school, and when he was 11 years old, he expressed his desire to become a scientist. But for children in Belfast, free and compulsory education ends at the age of 14, and then education has to pay a lot of tuition fees. Bell's father came out to help the family earn money when he was only 6 years old, but his family was not well-off all the time. Coupled with the influence of education policy, he naturally thought that Bell should have left school at the age of 14 to find another way to make a living. But his mother encouraged Bell to continue his studies. Bell wanted to go to a self-financed high school several times before, but the tuition fees were in the way, and he finally got a scholarship offered by the Technical High School of Belfast (Belfast Technical High School). Bell's sister Ruby was not so lucky. although she also got a scholarship to the school, she was unable to continue her studies because of her preference for sons. Bell's other two brothers, David and Robert, also dropped out of school early at the age of 14 to make money.

At the beginning of the middle school of study, job search and courtship, Bell became interested in ancient Greek philosophy. After reading a large number of philosophical books, he was disappointed to find that the definition of so-called "good philosophers" was that they could refute other philosophers, and that philosophy had to solve very big problems. For Bell, no progress has been made in the answers to these questions [10]. When he first came into contact with physics, he was pleasantly surprised to find that the progress of physics was obviously better than that of philosophy. From then on, Bell picked up his old dream and gradually planted the seeds of becoming a physicist in his heart. But he is not very satisfied with the rigid teaching of physics in school. Bell was a straight A student in high school, but he didn't show any outstanding talent other than that.

Bell, who graduated from high school at the age of 16, was unable to enter the university because he was not old enough to enter the university and could not afford the tuition. During this time, he began to look for a job that could support himself temporarily. He interviewed for many jobs, such as handyman in a small factory and entry-level job at the BBC, but failed in the end. Because the employers of these jobs think that Bell's conditions are too good, and when he goes to work, Bell confides in his body language that he doesn't want to do the job [11]. Fortunately, many of the practical skills Bell learned at the technical high school in Belfast helped him find a job as a technical assistant in the physics department at Queen's University (Queen's University) in Belfast and stay under the dean of the department, Karl George George é us [12]. In the meantime, he was also allowed to sit in on physics classes. After having a certain foundation in physics and saving enough tuition, he officially enrolled at Queen's University in 1945.

Bell still liked to express himself when he was in college and liked to argue with others. He often participates in group activities at school. Bell is not only concerned with physics, but also participates in philosophical, political and other discussion activities.

In the early days of college, Bell studied with Amelius and Robert Robert Harbinson Sloane. In the first year of admission, Bell directly passed the first-year subject examination and entered the second grade. Later, he studied quantum mechanics and related philosophical problems, and was deeply influenced by the great German physicist Max Born's Natural philosophy of causality and opportunity (Natural Philosophy of Cause and Chance) [13]. He was deeply attracted by quantum mechanics, especially the strange collapse of wave functions in quantum mechanics, which made him infatuated, which became one of the research directions that accompanied him all his life. Bell and the two teachers get along very well most of the time, but whenever Bell asks the teacher questions about quantum mechanics, they are always tit-for-tat and can't convince each other. Bell thought that the teacher's explanation could not help him understand quantum mechanics better, and the teachers became impatient under Bell's questioning [14].

In his last year at Queen's University, Bell had the privilege of studying with Paul Ewald (Paul Ewald), a physicist who came to Ireland because of Germany's political disaster. He was president of Stuttgart University of Technology and one of the founders of X-ray crystallography. This is also Ewald's last year in Belfast. There was a subtle chemical reaction between Bell and Ewald, who said everything to each other, and Bell impressed Elwald [15]. Bell finally began to study the quantum mechanics of long-chain molecules in the last year before he graduated. When Bell was working on his graduation thesis, Ewald suggested that he visit Rudolf Rudolf Peierls, a top theoretical physicist who is also in exile in Germany. But Bell was restricted by the family situation at that time and wanted to go to work directly, but failed to follow the advice of his mentor. However, the fate of Bell and Rudolf Pells has not been done, and the two still have an intersection in the future. Bell received a first-class degree in experimental physics in 1947 and a first-class degree in mathematical physics a year later.

For postwar scientists, there is no doubt that more "practical" physics can earn more than theoretical physics. Even though Bell loves quantum mechanics very much, he knows it can only be used as a hobby, not as a full-time job. Against this background, Bell chose to look for a job at the British Atomic Energy Research Agency (AERE) in Harwell in 1949. Bell's resume is inconspicuous. He neither has a doctorate nor graduated from a prestigious university. He is very uncompetitive compared with others. Fortunately, he met his own Klaus Fuchs here, and he placed Belian in the research reactor of the theoretical Physics Department [16]. A few months later, when Fuchs was arrested for espionage, Bell followed another man who admired and cared about him very much, Bill Walkinshaw, to Malvern College College, 80 miles from Harwell, to help design the linear accelerator. Bell began his research on medical linear accelerators. Here, Bell's deep understanding of basic physics and his strong mathematical talent played a vital role in his accelerator theory research. Warkinshaw once said of Bell:

"there used to be a young man with a very high quality who could quickly choose the project he wanted to study independently and had a special hobby for particle dynamics. his mathematical talent is superb and extraordinary." [17]

Bell's talent finally came into play here. He has published many articles in the fields of accelerator physics and high-energy physics, and even pointed out the great mistakes made by scientists many years later. Bell pointed out a long time ago [18]. We'll talk about it later.

For Bell, another major event of his life came. Here he met his work partner and future wife, Mary Rose. Mary was born in Scotland and her father is a clerk. Her mother is a primary school teacher. Besides Mary, she has two sisters at home, all of whom are vegetarians. Mary showed great interest in math and physics when she was a child, and her parents were very supportive of her reading. After receiving a scholarship, she chose to study mathematics and physics at the University of Glasgow (University of Glasgow), and in 1944 she was seconded to the Institute of Telecommunications (Telecommunications Research Establishment) in Malvern to do radar-related research because of the war. After earning her doctorate in physics and mathematics, she returned to Harwell in 1947 and returned to work in Marvin in 1950. Whether it is because they are attracted by each other's talent and rigorous work attitude at work, or because they are both vegetarians, there is a spark of love between them. At that time, Bell was asked which one was Mary, "the fat one, the tall one", and Bell replied, "No, the beautiful one" [21]. Bell also wrote in the preface to his book "the unspeakable and unspeakable in Quantum Mechanics" ("Speakable and Unspeakable in Quantum Mechanics"), "when I look back at these articles, Mary is everywhere" [22]. They are not only bosom friends in life, but also partners in scientific research (figure 3).

Fig. 3 Mary and John Bell's "hobby" at Stonehenge [23]

In 1952, thanks to the influence of AERE's policy of supporting young people to get higher degrees, Bell decided to further study himself-- studying for a PhD. At first Bell wanted to study field theory and he set his sights on the University of Glasgow and the University of Birmingham. He finally chose to come to Birmingham to learn from Rudolph Pells, who had never been able to visit. Although Pells explicitly opposed Bell's research on the basic theory of quantum mechanics, Bell was always obsessed with the problems that plagued him in quantum theory, so he chose quantum field theory as his research direction. Finally, he received his doctorate from the University of Birmingham in 1956.

In Bell's mind, quantum mechanics has always been an unbreakable knot. He kept tracking and thinking about the development of quantum mechanics as he did when he was a student. Bell has long been dissatisfied with the interpretation of quantum mechanics he was exposed to.

The first to bear the brunt is the teaching method of "Shut up and calculate". Bell was deeply puzzled by the fact that his lecture on quantum mechanics was a highly instrumental course-giving Schrodinger equations, solving wave functions, solving energy levels, and solving spectra. These mathematical operations are good, but doesn't quantum theory need philosophy? What is our actual perception of the material world? What is behind these equations [24]?

Then, the principle of uncertainty became the source of Bell's confusion about quantum mechanics. Bell's biggest confusion about the principle of uncertainty is: in real physics, what determines how accurate the existence of momentum and position is before the observer makes any measurements? With this question in mind, Bell went to read one quantum mechanics monograph after another, but neither born's Atomic Physics nor Paul Dirac's The Principles of Quantum Mechanics failed to answer his confusion.

Bell is also deeply disturbed by the special status of measurement in the Copenhagen interpretation. He certainly realized that in science, the role of measurement is the most important. In order to understand a particular physical quantity, we must measure it. But Bell's view is that when we measure a physical quantity in a scientific sense, we must be trying to get a value that exists before the measurement. He believes that the subject of science should not be limited to the results of measurements-it should study what exists without measurements. As a result, Bell declared himself a "follower of Einstein"-a staunch realist [25].

Finally, Bell was completely uninterested in Niels Bohr's ingenious "parables" that often appeared in the fundamental problems of quantum mechanics. Bell is more concerned with solid mathematical and factual evidence than speculative words [26].

Dissatisfaction with the interpretation of Copenhagen spurred Bell's mind. Finally, in 1952, the opportunity appeared. He read David Bohm's article on hidden variables in 1952, when he gradually focused on John von Neumann (John von Neumann) and the EPR paradox.

In fact, the EPR problem at that time was not as eye-catching as we would like to see today. Although this is a paper led by Einstein, Bohr responded quickly. At this time, the common understanding in the academic circle is that the Copenhagen School has solved the thorny conceptual problem in quantum mechanics, and Einstein's blame in the EPR problem can only be regarded as that he has not adjusted his own cognition to embrace the brand-new theory. According to Leslie Kerr, a good friend of Bell, Bell first came into contact with the EPR problem not directly through EPR's original paper, but through Bohm's masterpiece Quantum Theory (Quantum Theory).

Bell himself was fascinated by this question [27]-Bohm's account in the book takes into account the discussion of physical reality and discusses the technical details in a concise way. At the same time, Bohm himself has made a lot of useful progress in the theory of hidden variables. From this point of view, Bohm can be regarded as a leader of Bell in the study of quantum mechanics.

Bell himself was excited after reading Bohm's paper in 1952. As Mary said, "in his own words, 'this article is like an apocalypse to me'." [28] he digested Bohm's article carefully and asked him positive questions when he came to give a lecture. The attendees recalled that Bell's question clearly showed that he had studied Bohm's paper in great detail. This also leads him to an in-depth understanding of Von Neumann's work, because Bohm's essays have always shown doubts about the existence of false hidden variables in Von Neumann's books, but Bohm himself has failed to find a way to strictly prove his point. This was done by Bell a few years later.

In 1960, Bell and Mary joined the European Center for Nuclear Research (CERN). They had a lot of overlap with CERN when they worked in Malvern, and Bell was attracted by particle physics, so they officially joined CERN. Bell is in the theory department, while Mary joined the accelerator research group [29]. Bell's main work is particle physics and accelerators, but he never stops thinking about his "hobby"-the basic theory of quantum mechanics. In 1963, when Bell and his wife were given a vacation, he devoted himself to the study of quantum mechanics and visited Stanford University, the University of Wisconsin and the University of Brandez. As a short-term visiting scholar at Stanford University, Bell completed his first phased paper, on the problem of hidden variables in quantum mechanics (On the problem of Hidden Variables in Quantum Mechanics). In this article, Bell sharply points out that there are loopholes in the mathematical assumptions used to prove the existence of false hidden variables in Von Neumann's classic Mathematical basis of Quantum Mechanics (Mathematical Foundations of Quantum Mechanics).

"the real linear combination of any two Hermitian operators is an observable measure, and the expectation of the real linear combination of any two Hermitian operators is the real linear combination expected by each of the two Hermitian operators."

Bell's argument for this is also very simple. He uses a particle with a spin of-1max 2 and considers the construction of the most general Hermitian operator in its state space. It is found that at least some of the theories of hidden variables that can be simply constructed do not satisfy the hypothesis of Von Neumann, thus providing a simple and powerful counterexample. And the paper jointly published by Josef- Maria Jauch and Constantin Piron is similar to that of Andrew Gleason [30]. Because of the problem with the editor of the magazine, Bell's paper was not published until 1966, and he also pointed out in the article that his thinking on this issue can actually be traced back to 1952 [31]. Bell succeeded in proving that the hidden variable explanation was not completely refuted.

By finding a loophole in Von Neumann's rigorous mathematical derivation, Bell gained full confidence to impact the non-locality of quantum mechanics. Bell's second phased paper is his most famous paper, on EPR Paradox (On the Einstein-Podolsky-Rosen paradox). In this article, Bell focuses on Bohm's version of the EPR paradox.

Unlike the well-known EPR paradox based on particle spin, the entangled quantum states in Einstein's original paper are the positional states of two particles. Later, Bohm converted it into the entanglement of the spin state that we are now familiar with. This kind of treatment has a lot to do with the initial confrontation between the two. Einstein's original idea was that the measurement of two-particle entanglement could imply that particles could have a definite position and momentum at the same time, so Bohr's response was to reaffirm the uncertain relationship that was almost consensus under the Copenhagen School. However, the real crux of the EPR problem does not lie in this, but in the fact that when the observer knows the state of one of the entangled particle pairs, the state of the other particle is immediately determined, that is, the problem of locality. Einstein himself clarified his view again later, but Bohr didn't seem to notice it. Bohm's transformation points out the original EPR problem in a clearer and more operational way.

In the view of Bell at that time, although Bohm's hidden variable theory could reproduce many predictions of traditional quantum mechanics, it had very distinct non-local characteristics. While the EPR paradox refers directly to the locality problem, Bohm believes that the non-locality problem of quantum mechanics pointed out by EPR will be overcome by the interpretation of hidden variables. The combination of the two seems to imply that there is a local hidden variable theory, which can not only reproduce the important predictions of quantum mechanics, but also overcome the disturbing non-locality in the EPR paradox. But Bell proved that no local hidden variable theory could reproduce all the statistical predictions of quantum mechanics, which became known as the Bell Theorem [32].

Bell's theorem shows that the difference between local hidden variable theory and quantum mechanics is not only purely speculative, but also measurable-people can rely on specific experiments to make the final decision for both. Relying on the original EPR experiment and the revision of Bohm's version, Bell soon found a specific means of operation. Bell found that in Bohm's modified EPR experiment, the spin components of the two particles were always measured perpendicular to each other. This comes from the original EPR paper, because Einstein considered that the position-momentum relationship and the spin perpendicular to each other have the same algebraic origin of quantum mechanics. Previous work has indeed proved that if the measurements discussed are always limited to spin components in the same direction or perpendicular to each other, the measurement results of quantum mechanics are no different from those of local hidden variables. However, once the spin measurement in any direction is introduced, the difference between the two can no longer be hidden. The Bell inequality derived by Bell precisely describes the commonness of this kind of measurement results under the theory of arbitrary local hidden variables, but the measurement results of traditional quantum mechanics will not satisfy this inequality. Therefore, by designing experiments to test whether the Bell inequality is true or not, it becomes a fair judgment to adjudicate two theories, even two kinds of world outlook.

Although Bell's original intention in writing the Bell inequality was to prove Einstein right, it was used to prove Einstein wrong. In the era of successful interpretation of numerous micro-phenomena in Copenhagen, it would be impossible to do such a work without unease about the extension of its philosophy. However, when Aspe's experiment was successful, Bell commented fairly, "this experiment shows that Einstein's worldview is untenable." [33]

One of the interesting points is that during the contribution process, it is natural for Bell at Stanford University to choose "Physical Review", but the physical review charges a high page fee, and Bell thinks it is very impolite to charge Stanford University for this fee as a visiting scholar [34] So Bell chose to submit this article to Physics, an obscure magazine published only until 1968.

Although Bell is well known for his research on quantum mechanics, quantum mechanics is only his hobby, and accelerator physics and high energy physics are his main business.

Most of Bell's accelerator research in the 1950s was done in AERE, which mainly provided mathematical methods for the construction of linear accelerators, and these methods can still be used as the starting point of a large-scale computer program [35].

The mathematical method referred to here establishes a general theory for the motion of the particle beam under the strong focusing system, which is an important part of the accelerator principle. The so-called strong focusing system relies on two different types of magnets-focusing magnets and defocusing magnets. Under the specific arrangement and combination of focusing magnet and defocusing magnetic field, charged particles can make the particle beam more and more concentrated while maintaining the stability of the particle beam, just as the beam behaves under the convex lens and concave lens group. At first, when dealing with the problem of strong focusing, we naturally use the traditional method, that is, to analyze the trajectory of the particle beam based on the equation of motion. But for the most general design, the analysis based on differential equation is too cumbersome and cumbersome, and the most convenient way is to use matrix to deal with it. Bell wrote the article "basic Algebra of strongly focused Systems" (Basic Algebra of the Strong Focusing System) in 1953, and introduced the matrix processing method under strongly focusing problems in detail, and introduced the important invariants in this system, which is now generally known as Coulomb-Schneider invariants (Courant-Snyder invariance). It should be emphasized that Bell's work was carried out independently of Ernest D. Courant. Phil Burke and Percival wrote in their biographies and memoirs that Bell's article was "very influential... all accelerator designers had read it at that time" [36].

Another important work of Bell during this period was the article "Phase Vibration of Linear Accelerator" (Linear accelerator phase oscillations) published in the AERE report in 1954. This article is also a masterpiece carefully selected for his research in this period when Bell's wife Mary participated in the compilation of Bell's essays, showing his admiration for Bell's work. The main "rivals" of this article are two heavyweights in accelerator physics, Robert Serber and 'Pief' Panofsky. (incidentally, the quoted name was given to him by Panofsky's friends and relatives because they found his original name too difficult to pronounce. )

In the linear accelerator, the acceleration of the electron beam is carried out in the waveguide tube by means of a periodically varying electric field. Based on the simple electrodynamics, we know that the electric field in the waveguide is composed of several different Fourier modes. So when studying the acceleration of this kind of electron beam, do we only need to consider the influence of the mode of a certain basic frequency, or the contribution of all modes? John C. Slater's article in 1948 supports the former, while the studies of Cyber and Panofsky in 1948 and 1951 respectively believe that the influence depends on the specific form of accelerated electric field. Bell's article supports the view of the former.

Bell's calculation is carried out directly for any acceleration field. The mistake of the two experts was that they made inappropriate approximations in their specific calculations. How to make a good approximation in physics is an extremely profound problem, and the ability of physicists can be seen by dealing with the approximation. As Mary said, Bell's article is based on the Hamiltonian form of relativistic particle dynamics in an arbitrary acceleration field in a linear accelerator. More deeply, the analysis of Bell's article is still based on the use of Kurant-Schneider invariants, and the original Hamiltonian form protects important dynamic invariants, thus protecting dynamic evolution. This also confirms Bell's deep understanding of the basic theory.

However, this article was not published in a magazine, but as an internal report of the Institute. Mary said that later scientists still made the mistakes Bell pointed out in this article [37].

In the 1980s, Bell's interest returned to the field of accelerator physics. With the increase of the energy and brightness of the accelerator, the influence of quantum fluctuation on the particle beam in the accelerator will become more and more significant. In the 1950s, an accelerator designer was able to work just by virtue of his familiarity with classical theory-- as Bell did earlier-- but in the 1980s, people have to take quantum effects systematically and seriously in traditional accelerator research. At the same time, CERN in the 1980s is also working on a number of accelerator-related projects, such as the initial cooling experiment (Initial Cooling Experiment,ICE) and the large Electron Positron Collider (Large Electron-Positron Collider,LEP, which was dismantled at the end of 2000). Both his interest in physics and the research needs of his unit finally prompted Bell to return to his main research career in the 1950s.

In the aspect of ICE, Bell's research mainly focuses on the particle beam refrigeration technology. There is an important physical concept in the study of particle beam, which is called emittance, which refers to the area occupied by particle beam in phase space. The lower emittance means that the corresponding particle beam has a more concentrated spatial distribution, but also has a more consistent momentum distribution, which means that the particle beam has better quality. The cooling of particle beam refers to the technology of suppressing the emittance of particle beam. Bell has made in-depth research on several important technical directions of this technology, such as electronic refrigeration (Electron Cooling), random refrigeration (Stochastic Cooling) and radiation damping. It is particularly worth emphasizing that when studying radiation damping as a particle beam cooling technique, Bell once again-- as in the case of strong focusing-- developed a general formal theory based on his deep knowledge in physics. This time his theoretical tools are Lagrangian parentheses and Lagrange invariants.

For LEP, Bell deeply studied the problems of radiation damping and quantum Bremsstrahlung in the accelerator. Because of his experience in the linear accelerator [38], Bell was able to calculate the radiation damping of the storage ring orbit in the accelerator directly through a very simple formula, while the traditional method is realized by complex orbit calculation [39]. In Bell's research on LEP, another kind of eye-catching work is related to the very important effect in the quantum field theory of curved space-time-the Amrou effect (Unruh Effect). The Amru effect is the effect that accelerated observers will find that their vacuum is filled with thermal radiation, which is closely related to the famous Hawking radiation. However, the thermal background temperature produced by the Anlu effect is so low that up to now, how to detect the Amru effect is also a controversial topic in the academic circle. On this issue, Bell gave his own detection idea-observing the characteristics of the accelerated electron beam in the accelerator. In the title of Bell's own article, "the electron is an accelerated thermometer." Bell systematically studied the effects of the Amru effect on many observable effects of the electron beam. This is also a microcosm of Bell's dual identity as an outstanding theoretical physicist and experimental physicist.

In addition, Bell's deep understanding of classical mechanics and classical field theory led the author to catch another interesting "little thing" in Bell's academic career: Lev Landau's famous Ten volumes of Landau, the series of books on theoretical Physics, published by E. M. Lifshitz, was translated by Bell. Bell participated in the translation of "Mechanics", "Quantum Mechanics: non-Relativistic Theory", "Continuum Electrodynamics" and "Quantum Electrodynamics" (the earliest version is entitled "Relativistic Quantum Theory"). It corresponds to Hubert's best research field.

The most important research direction of the versatile Bell in his life is high energy physics. In terms of research means, it includes not only the study of phenomenology of particle physics, but also the study of quantum field theory. From the point of view of the research object, Bell's research breadth almost covers a series of studies that have influenced high energy physics in history: CPT theorem, beta decay, phenomenological model of nuclear physics, neutrino physics, Parton model, quantum chromodynamics, K meson and CP destruction, flow algebra, light hadronic spectroscopy and light hadronic structure. Hadron spectroscopy including heavy quark hadrons, gauge field theory, unstable particles in quantum field theory, σ-models, solitons in quantum field theory, quantum anomalies. We are unable to introduce Bell's achievements in each direction, so we only choose a few of them to introduce them.

The first is Bell's outstanding contribution to CPT's theorem. CPT theorem is one of the most important theorems in quantum field theory. It points out that for any local quantum field theory which satisfies Lorentz invariance and its Hamiltonian has Hermite property, the theory after three different discrete transformations-charge conjugation (C), space inversion (P) and time inversion (T)-is the same as before. With the help of CPT theorem, many important inferences can be obtained, such as positive and negative particles must have equal mass and so on. Bell's paper on the proof of CPT Theorem, time reversal in Field Theory (Time Reversal in Field Theory), appeared in the Proceedings of the Royal Society (Proceedings of the Royal Society, A) in 1955. But Bell's luck was a little worse. In completing this paper, Gerhard L ü ders and Wolfgang Pauli's work reached the same conclusion at about the same time as Bell (Bell's doctoral thesis, published in 1954, actually included the proof of CPT's theorem). But Bell's paper gives a more general proof [40]. Not only that, but Bell's proof is simpler and clearer, which is quite different from that of Luders. This is the fundamental reason why Bell's article can still be published in the Proceedings of the Royal Society after receiving Luders' paper. And today, Bell's work, as Martinus J. G. Veltman said, may be more meaningful than the argument of axiomatic field theory developed by Luders [41]. In fact, the problem of time reversal invariance has always attracted him, and it can even be regarded as one of the topics in his life. Therefore, he then went to study the problem of CP destruction in K-meson decay.

The bond between Bell and CPT symmetry may be more enlightening for us. Pells, Bell's mentor, had read about particle physics experiments and said he seemed to have found a negatively charged particle that was stable and had a lighter mass than a proton. Participants in the experiment asked Pells if the particle could be an antiproton, and at the time, particle physicists generally believed that particles should have the same mass as their antiparticles. But Bell expressed doubts about it. Bell naturally hates to presuppose a point of view because it is widely held [42]-Bell wants to prove it. And this problem, as Perls said, soon became a worry for Bell. Bell took it as the research subject of his doctoral thesis.

Another thing to focus on is Bell's contribution to quantum anomalies (Quantun Anomaly). The Nott theorem in classical physics, that is, the corresponding relationship between continuous symmetry and conservation laws, can be said to be like thunder. So when a classical theory is quantized, can the symmetry of the original classical level be preserved in the quantum field theory? Although there is still a Ward-Takahashi identity (Ward-Takahashi Identity) caused by symmetry in quantum field theory, things are not that simple-quantum anomalies mark the destruction of classical symmetry at the quantum level. Bell's study of Adler-Bell-Jackiw anomaly in quantum electrodynamics (QED), which is an important example of quantum anomaly in gauge field theory, is still a classic in gauge field theory [43]. This anomaly means that after considering the single-loop correction of QED, the conservation of electron axis vector flow under classical electrodynamics can not be guaranteed. ABJ anomaly is the first quantum anomaly discovered in academic circles, and its importance is self-evident. This is of great significance to the general quantum gauge theory, whether the field theory in high energy physics or condensed matter physics [44]. In a way, in the study of high-energy physics, Bell's study of quantum anomaly may be more influential than his study of non-locality of quantum mechanics. One example is that on Inspire HEP, a popular search site for high-energy physics, there are more citations in ABJ abnormal papers than Bell's two papers on basic issues of quantum mechanics combined.

"the Sage of CERN" Bell has worked in CERN for a total of 30 years, where he is known as the "Sage of CERN" [45]. Many colleagues who know or do not know will ask Bell a variety of questions, and Bell can always reveal the crux of the problem. Bell often said that "CERN is like a railway station with many passers-by" [46]. He can meet new friends and solve new problems here every day, and his colleagues are all moved by Bell's enthusiasm for science and his dedication to the truth. Bell also maintained the old English tradition of 4 o 'clock tea in CERN, and it was also a time for him to talk with his friends, not only about physics, but also about politics, philosophy and even art.

Bell suffered from migraines all his life, which disappeared for several years. In the last time of his life, migraines occurred briefly to Bell [47], but did not attract his attention. Bell's good friend Reinhold Bertlmann also recalled that when he met Bell in Paris in 1990, he did not seem to be in good health [48]. In the same year, Bell died of a sudden cerebral hemorrhage.

Bell's life was as short as a meteor. In this short period of 62 years, he left a very rich physical legacy. All his life, he has been pursuing the deepest and most difficult questions in physics, and is willing to use it as a starting point to start his work, without fear of walking alone on the lonely road. As a highly skilled theoretical physicist, he always maintains a close relationship between theory and experiment. He is not only willing to devote himself to the solution of specific experimental problems, but also devote himself to the experimental test of the theory. It is the dual exploration of theory and experiment, the deep blending of specific problems and philosophical thinking, and the equal contest between previous wisdom and self-reflection that made him take an epoch-making step in the exploration of the basic problems of quantum mechanics.

If we regard the research of a scholar's life as a landscape, then the landscape that belongs to Bell is not a single tree into a forest, not a hundred flowers competing for beauty, not a cloud and mist, not a sea of rivers, but like an intertwined garden. Although it is not the wonder of miraculous craftsmanship, not the magnificence of epoch-making, but his human ingenuity transforms his understanding of the world into the layout of the garden. Whenever you and I walk by, we will not give out heartfelt admiration-how lucky you and I are to be able to enjoy such a scenery.

According to legend, in the year of Bell's death, he was nominated for the Nobel Prize in Physics [49]. There is no doubt that he should have a share in the 2022 Nobel Prize in Physics, which may also be a kind of compensation to Bell.

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