Zheng Fan's mathematical life is anchored in the Indonesian tsunami more than a decade ago.
On December 26, 2004, the Indonesian tsunami broke out, killing or missing at least 300,000 people. Zheng Fan, a 12-year-old junior high school student in Shanghai at the time, happened to be reading an extracurricular book on how the sea moves, which talked about using mathematical knowledge to predict and analyze tsunamis.
It was this tsunami that gave him more motivation to learn mathematics.
Figure | The catastrophe brought by the tsunami to mankind (Source: Oriental IC)
After many years, at the award ceremony of the Alibaba Global Mathematics Competition in 2020, Zheng Fan, who won the gold medal, specifically mentioned the impact of the Indonesian tsunami on himself in his award speech.
Figure | Zheng Fan spoke at the award ceremony (Source: Alibaba Dharma Academy)
Today he studies fluid mechanics at the Spanish Institute for Advanced Sciences, including using mathematical knowledge to predict tsunamis.
Seawater itself is fluid, so to study tsunamis you must understand fluid mechanics. When describing the motion of fluid mechanics, some people may think that some physical equations should be used, but mathematicians have already written these equations.
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From a mathematical point of view, a tsunami is a wave with a large fluctuation amplitude and a catastrophic wave. Previously, experts in the field mostly did research when the sea was calm.
However, there are sometimes huge waves on the surface of the sea, and the cause of such waves is not yet known to humans. Some ships sail on the surface of the sea, and suddenly there is a capsizing accident, most likely because of this huge wave.
Satellite observations have found that the amplitude of these unknown waves is far beyond human imagination, which indicates that there may be some mathematical difficulties that humans have not yet mastered.
In general, earthquakes can cause tsunamis or waves. Previous research in this field has also been mostly around the spread of tsunamis or waves. However, the pain point currently faced by human beings is that tsunamis are usually caused by submarine earthquakes whose source is within 50 kilometers of the seafloor and have a magnitude of 6.5 or more on the Richter scale.
Earthquakes are usually accompanied by aftershocks, and the aftershock epicenter may be far away from the main epicenter, so Zheng Fan's research topic is: if an earthquake occurs in two places at the same time, and tsunamis occur in both places at the same time, then how big the two tsunamis are and whether there will be interaction between them.
In his specific research, the first thing he did was to penetrate an important model in fluid mechanics: the Gravity wave model. The model has a long history, in 1959, The University of Cambridge, Paul M. Professor Paul A.M. Dirac mathematically proved the existence of gravitational waves.
Figure | Zheng Fan's research
In fluid mechanics, a gravitational wave is a wave within a liquid medium, or between the interfaces of two media, such as between the atmosphere and the ocean.
When a small blob of liquid leaves the liquid level or enters a different density area of the same liquid, due to gravity, the blob of liquid will swing in the form of fluctuations. The waves generated by this oscillation are the cause of the tsunami.
After more than a year of research, Zheng Fan wrote a paper called "Long-term regularity of 3D gravity water waves."
The paper concludes that incompressible fluids, which occupy half a three-dimensional space, flow under their own gravity. In simple terms, gravitational wave models still have considerable accuracy in predicting tsunamis caused by multiple earthquakes.
He plans to really push this research into tsunami prediction. According to Zheng Fan, using the research results, a more accurate tsunami model can be constructed, supplemented by numerical simulations by computers, and the propagation law of the tsunami can be predicted more accurately, so that the potentially affected areas can make more adequate response plans.
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The growth experience of this "post-wave" guy who studies the waves is also quite thorny. When Zheng Fan was a few years old, when his parents took him for a walk in the community, he found that he liked to stare at the license plate and could quickly recite the license plate number.
The parents judged that this was a child with mathematical talent, and planned to train him to learn mathematics. Therefore, a lot of zheng fan's student time was spent in mathematical popular science books, mathematical games and mathematical competitions.
In elementary school, Zheng Fan's school had an Olympiad interest class every Saturday, and although the curriculum was difficult, he learned it well. It just so happened that the math teacher said that there were some competitions to participate in, so since elementary school, he has been a regular in the math arena.
A few years later, Zheng Fan was admitted to the well-known Shibei Junior High School in Shanghai, which also had many competitions, comprehensive competition results and usual results, and he entered Shanghai Middle School to study high school.
At Shanghai Middle School, Zheng Fan began to participate in the Shanghai High School Mathematics League and ranked among the best. With this result, he qualified to participate in the National Mathematics Winter Camp for Secondary School Students.
In the winter camp, Zheng Fan's results ranked in the top six. He then represented the national team in the International Mathematical Olympiad, along with other outstanding players. In the end, six students, including Zheng Fan, won the gold medal.
Figure | Zheng Fan won the gold medal in the International Olympiad (Source: Interviewee)
Based on his results in the competition and his usual results, he was escorted to the School of Mathematics of Peking University, transferred to the Massachusetts Institute of Technology to study basic mathematics in his sophomore year, and was later admitted to Princeton University to pursue a direct doctorate, with a doctorate in mathematics partial differential equations.
Figure | Zheng Fan at Peking University (Source: Interviewee)
It is worth mentioning that the four gold medal winners of the Alibaba Global Mathematics Competition, including Zheng Fan, have studied in the School of Mathematics of Peking University during their undergraduate studies.
Now Zheng Fan is doing postdoctoral research at the Spanish Academy of Mathematical Sciences, and his main research direction is fluid mechanics.
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Zheng Fan was born in 1992, and among the gold medalists in this competition, he is slightly older, and he is more mature in his award speech and shows a higher vision. This is also related to his relative rich experience.
This is his second participation in the Alibaba Global Mathematics Competition, the first of which he also participated and won the bronze medal. After two years, he competed again to win the gold medal, which he believes is mainly due to the choice of the track "Analysis and Equations", which is also the direction he is working on.
Talking about the original intention of participating in the competition for the second time, he said that this is because many of the topics in the Alibaba Global Mathematics Competition are closely related to life. For example, some math tests are to plan the route for the takeaway brother, and some are to analyze how to use Taobao coupons. The grounded mathematical problems also made Zheng Fan decide to "go out for the second time".
Although the title seems to be popular, but it is hidden mysterious, it is difficult to pass the customs without a certain mathematical foundation, and some netizens commented that "the words are understood, but they will not do it."
It is understood that more than 50,000 people around the world signed up for this competition, more than 15,000 people submitted answer sheets, and finally more than 500 players entered the final competition, while Zheng Fan's results ranked in the top four and won gold awards.
Since the probability of winning is only 0.15%, this competition has also been named "the most difficult math competition in history" by netizens. After participating in the competition, Zheng Fan's biggest feeling is that mathematics is everywhere. Alibaba Damo Academy also said that mathematics is the foundation of all natural sciences, and many cutting-edge technology research is inseparable from mathematics.
Since the beginning of 2020, when China has fought the epidemic, it has used cloud computing, AI, big data and other technologies to build a strong "technological immune system", and the emergence and development of these technologies are based on the strong support of basic mathematics.
Tian Gang, an academician of the Chinese Academy of Sciences, an academician of the American Academy of Arts and Sciences, and the director of the Beijing International Mathematical Research Center, who served as the director of the proposition committee and the steering committee of the competition, also said at the award ceremony that China needs to cultivate a group of outstanding young mathematicians to make China truly a mathematical power.
What is a young mathematician? The first must be young, and the second must be smart, that is, the excellent "back wave". And Zheng Fan's "back wave" happens to study the waves. When the "back wave" goes to conquer the waves, it must be able to ride the wind and break the waves.