Monday, June 22, 2020

Guest Post: “Who Needs a Giant New Collider?” by Alessandro Strumia

Size of 100km tunnel for CERN's planned new collider, the FCC. [Image:CERN]

For the first time in the history of particle physics the scientific program at a collider is mostly in the past light cone and there is no new collider in view. I would like to share my thoughts about this exceptional situation, knowing that many colleagues have negative options of those of us who publicly discuss problems, such as Peter Woit, Sabine Hossenfelder and even Adam Falkowski.

To understand present problems, let’s start from stone age. Something that happens only once in history happened about a century ago: physicists understood what matter is. During this golden period, progress in fundamental physics had huge practical relevance: new discoveries made people richer, countries stronger, and could be used for new experiments that gave new discoveries.

This virtuous cycle attracted the best people and allowed to recognise deep beautiful principles like relativity, quantum mechanics, gauge invariance. After 1945 nuclear physics got huge funds that allowed to explore energies higher than those of ordinary matter building bigger experiments.

This lead to discoveries of new forms of matter, but at energies so high that the new particles had little practical applications, not even for building new experiments. What practical use can have a particle that decays in a zeptosecond? As a result, colliders still use ordinary matter and got bigger because physics demands that the radius of a circular collider grows linearly with energy: R ≈ (4π/α)3 (energy)/(electron mass)2 in natural units. This equation means that HEP (High Energy Physics) can explore energies much above the electron mass by becoming HEP (High Expenses Physics). Some people get impressed by big stuff, but it got bigger because we could not make it better.

For decades bigger and bigger colliders got funded thanks to past prestige, but prestige fades away while costs grew until hitting human resources and time-scales. European physicists saw this problem 60 years ago and joined national resources forming CERN. This choice paid: a few decades after WW2 Europe was again the center of high-energy physics. But energy and costs kept growing, and the number of research institutions that push the energy frontier declined as 6, 5, 4, 3, 2, 1.

How CERN began.
Some institutions gave up, others tried. Around 2000 German physicists proposed a new collider, but the answer was nein. Around 2010 Americans tried, but the answer was no. Next Japanese tried, but the answer was “we express interest” which in Japanese probably means no. Europeans waited hoping that new technology will be developed while the Large Hadron Collider will discover new physics and motivate a dedicated new collider to be financed once the economic crisis is over. Instead of new technology and new physics we got a new virus and a possible new crisis.

The responsibility of being the last dinosaur does not help survival. Innovative colliders would need taking risks, but unexplored energies got so high that the cost of a failure is no longer affordable. But this leads to stagnation. CERN now choose a non-innovative strategy based on reliability. First, get time by running LHC ad nauseam. Second, be or appear so nice and reliable that politics might give the needed ≈30 billions. Third, make again ee and pp circular colliders but greater, 100 km instead of 27.

As a theorist I would enjoy a 100 TeV pp collider for my 100th birthday.

But would it be good for society? No discovery is warranted, but anyhow recent discoveries at colliders had no direct practical applications. Despite this, giving resources to best scientists often leads to indirect innovations. The problem is that building a 100 km phonograph seems not a project that can give a technology leap towards a small gadget with the same memory. Rather, collider physics got so gigantic that when somebody has a new idea, the typical answer no longer is “let’s do it” but “let’s discuss at the next committee”. Committees are filled by people who like discussing, while creative minds seem more attracted by different environments. I see many smart physicists voting with their feet.

But would it be good for physics? So far physics is a serious science. This happened because physics had objective data and no school or center ever dominated physics. But now getting more high-energy data needs concentrating most resources in one center that struggles for its survival. Putting all eggs in one basket seems to me a danger. Maybe I am too much sensitive because some time ago CERN removed sociological data that I presented (now accepted for publication) and warned me that its code of conduct restricts free speech if “prejudicial to the Organization”. Happily I am no longer subject to it, and I say what I think.

Extract from rules that CERN claims Strumia violated.


Even if CERN gets the billions, its 100 TeV pp collider is too far away in time: high-energy physics will fade away earlier. Good physicists cannot wait decades fitting Higgs couplings and pretending it’s interesting enough. The only hope is that China decides that their similar collider project is worthwhile and builds it faster and cheaper. This would force CERN to learn how to make a more innovative muon collider in the LHC tunnel or disappear.

53 comments:

  1. To maintain public support, high energy physics needs to generate new headlines. But you can only "discover the God particle" once.

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    1. See, this One God nonsense is no good. There are the gods particles, the Aesir and the Vanir. Enough to keep generations employed.

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    2. I prefer Tolkien's cosmology. But is there a Melkor particle - and what role does it play?

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  2. Try again. This sounds filled with doubt. This is a hard call. The 19-100Tev range is enticing. Maybe supersymmetry lies there, though I suspect it is associated with quantum gravity, or there is sphaleron physics etc.

    It is a tough decision.

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    1. This is the Let's Just Look and See argument and it *will* win the day.

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  3. I am a phD student in mesoscopic physics. I think the experiments are much more revealing in this field then in particle physics, where people are not sure of anything. And here we do not have a well defined theory for non-linear physics that we see in our experiments(which is a motivation).

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  4. Sabine, can you clarify your position,

    you are against CERN building a large 100km collider with $24 billion price tag, but not China

    also, what do you think of doubling LHC energies via magnet upgrades?

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    Replies
    1. This is a guest post by Alessandro Strumia. I did not write it.

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    2. Doubling LHC energy would require new magnets; basically in means rebuilding LHC. About China, they could build similar colliders cheaper (tunnels in China plain cost less in Alps) and faster (they don't have to run LHC until 2030-2040). Faster is important because this field cannot survive to ≈30 years without significant progress. Already now many good authors moved to something else

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  5. Given the budget problems caused by C19, CERN will be lucky to have continuing research funded, never mind construction of a new collider.
    Public support is only likely if new research can address the issues that the physics community has publicized - such as missing matter, missing energy, missing anti-particles. That would generate new headlines and prestige for the countries involved.

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    1. There is no reason to think a bigger collider will be able to shed light on any of these questions.

      Having said that, it's not a matter of public support, because funding decisions for big projects like this are made behind closed doors.

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    2. Advertisements tend to be optimistic. In this case no discovery is guaranteed. Dark matter is not impossible. The true reason why higher-energy colliders are interesting is that we don't know what they might find. It's like exploring new territory.

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    3. I don't know how the European budgeting process works, but it hard to believe those making decisions behind closed doors are not affected by public opinion, or at least the opinion of the knowledgeable part of the public. The USA super collider got turned down after substantial public debate. There were many newspaper stories about it.
      I don't think that general speculation about the unknown can compete for funding against the many smaller projects looking for missing matter and energy.
      The desire for scientific advancement and national prestige behind a collider cuts both ways. If a bigger collider produces little of interest, the countries funding it will be embarrassed and may have less interest in funding any future speculative research, big or small.

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    4. In our E&M courses we learn about resonance cavities, where particle accelerators are a chain of these so charged particles in a sense "surf" EM fields. Instead of the RF field could be that of light or IR radiation and these cavities could be instead of large boxes small laser cavities. Some ideas along these lines are in the works, such as plasma wake acceleration by lasers.

      I suspect maybe too little attention has been given to alternative methods.

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    5. This has been attempted. Something has been achieved. But at low energies and low cost. To reach the high energies considered interesting today one needs billions of this possible new technology. This makes difficult to develop it.

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  6. Making debris from debris from the Big Bang, followed by making debris from debris from debris from the Big Bang? Is there a MOAP, a Mother Of All Particles?

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  7. " Something that happens only once in history happened about a century ago: physicists understood what matter is."

    I didn't hear about this!

    What is matter?

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    Replies
    1. you are using internet, one of the many technology made possible after understanding matter

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    2. There is no shame in saying "I don't know!"

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    3. About 90% of present GDP is due to scientific discoveries made possible by the fact that ≈150 years ago people understood that matter is electrons, nucleons and photons. While heavier particles discovered at colliders, such as the Z boson, contribute to 0% of GDP.

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    4. "matter is electrons, nucleons and photons."

      Hello,

      I agree with you, completely !

      I thought you would have had a more 'modern' view.

      Greg

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  8. Reading the essay, I ask: what does "good physicists" mean ?
    How does one define a "good" physicist ? Reading the essay, I ask: what does "good for society" mean ? Who decides what is "good" for society ? How and when does the "good" of theoretical research materialize for society at large ? The arguments against the CERN proposal are as opinionated ("un-scientific") as the arguments for the proposal. Research is open-ended and I fail to see that "high-energy physics will fade away..." Recalling 1980, I chuckled while reading Stephen Hawking's essay "Is The End In Sight For Theoretical Physics," because theoretical physicists are terrible at predicting the future of their subject.
    June 19th, 2020, I read Sabine's Scientific American opinion-piece: "The World Doesn’t Need a New Gigantic Particle Collider." The only part of that piece that resonated with me is this: "Yes, one can hope."
    By the way, were it not for "public support" many scientists would hardly be in a position to "do" their research.
    A quote: "We dedicate this book to our fellow citizens Who, for love of truth, Take from their own wants by taxes and gifts, And now and then send forth one of themselves as dedicated servant to forward the search into the mysteries and marvelous simplicities of this strange and beautiful Universe, our home."
    (1973, Gravitation by Misner, Thorne and Wheeler).

    ReplyDelete
    Replies
    1. Try smelling a physics paper. Some smell good, others stink.

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    2. How could it be otherwise ? After all, physicists are people. As Abraham Pais wrote, back in 1986: "As to the community of high-energy physicists, in many respects it is not all that different from the rest of humanity. One encounters some noble characters, some bastards, also some who are like poets..." (page 4, Inward Bound).

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    3. So ... bad papers, by bad physicists are published in respeted, prestigious, peer reviewed journals.

      There are no good physicists or competent physicists or theoretical physicists anymore. Just people who manage to pass their exams.

      Delete
    4. Greg Feild
      "Just people who manage to pass their exams" implies the current (and upcoming)generation of physicists is unable to extend the subject - their knowledge and ability being limited to that of their examiners. In essence then physics is dead.
      This seems to me to be a false premise. Of course there's always a chance that the stream of papers, periodicals and blog posts crossing my desk on a daily basis are not the serious technical reports they purport to be but just so much fake news and spam mail concocted by the writers of the Big Bang Theory. And all those I take to be serious physicists pushing the bounds of their subject are really stand up comedians and con artists.
      Yes, you can take your extreme pessimistic view that physics has reached the end of the road. But I prefer to be more optimistic. It's just that at this stage there are things we don't understand well enough to explain to our grandmothers (as Einstein is reported to have, sort of, said).

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    5. Hi rgt,

      I don't think physics is at a dead end.

      I think students should be encouraged to be skeptical of the current models and to 'deconstruct' them rather than trying to extend them.

      Greg

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    6. SG recently posted a brilliant list of Isssues -

      "Lost in Math or Lost in Philosophy?

      Quantum philosophy/quantum epistemology (common agreed/disagreed understanding of QM) is built on many partial interpretations cumulated during the long and complicated journey from Planck to Born (energy packages, wave-particle photon, electron jumping among orbits, particle-wave electron, matrix mechanics non-commutativity, wave equation, uncertainty principle, probability wave interpretation, complementarity, measurement, entanglement, decoherence).

      However “shut up and calculate” stuff based on existence of intrizic spin, Dirac equation and its extensions -- abelian QED U(1) and non-abelian EW SU(2) and QCD SU(3) covering all mathemathical technicalities (plus hyper-charges and iso-spins) -- is not manifesting itself in general understanding/epistemology despite its phenomenal success in explanation of experiments/quantum ontology (interaction by exchange of particles, matter particles, field particles, virtual particles (in Feynman diagrams), hyper-charges, iso-spins, color charge, internal degrees of freedom, fiber bundles, internal geometrization, holograms, susy, quark mixing, neutrino oscilations, gauge, groups, abelian/non-abelian, non-linearities, renormalization, running constants, isolated quark non-observability/observability, 2-colored gluons, asymptotic freedom, confinement, charged and neutral weak current, EM charge of W bosons, hadronization/non-hadronization of heavy quarks, mass (lepton masses, hadron masses), 3 generations, …).

      The fact that “quantum” means exactly and just “quantum of spin” (angular momentum) all the time since Planck remained and remains mostly unnoticed. Instead one boldly tries to to unify SM with gravity based on personal perception of beauty/ugliness.

      There is no clear, comprehensive, logical, consistent understanding of geometry of spinors (Dirac equation) beyond that they are just used as the weird tool to work with matter particles/fermions available. This situation is here already 90 years since Weyl discovered neutrinos in Dirac equation. Weyl also invented gauge field from which our current understanding of SM was later developed however this part of story – the successfully one – ended in 70s as you already mentioned. Till 90s many thinkable and unthinkable GUTs based on the group theoretical arguments were developed and studied. Later development is almost completely lacking any groundings/connection with physical reality. Surprisingly evident non-linearities residing in electro-weak model and quantum chromodynamics and their relation to non-linearity in gravity did not attract significant attention.

      We all know that Newton’s absolute space and time are nonse but unitarity with necessary background dependence of QM is not just ok, it is the central dogma to which we resort. Where is the courage and imagination? What about the possibility that ‘diffeomorphism-invariant’ QM is kind of “self-dual” view/question and is going to offer us answers to all open problems at once (SM+gravity unification, DM, DE).

      Dark matter is despairedly searched ether of our times but how can one know which of plentitude of empty-handed experiments is to be recognized as modern version of Michelson-Morley? What about to think of physics resulting in MOND? Or about of connection between the SM properties of matter (that constitutes and fills the universe), their relation to gravity and the properties of observed universe itself?

      Dark energy is the measure of our ignorance of both macro- and micro- cosmos. How do we even dare to think of explanations when we lowly know just about the 5 % of all mystery? Or? Is there missing something? Like a bit critical view to the current cosmology, which sees our cosmos as 13.8 bilion years old and expanding in very complicated way from the initial singularity to its observed size without any reliable (and model independent) direct evidence? "

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  9. Thank you Alessandro for sharing your thoughts!

    I'm actually disappointed by the recent update of the European particle physics strategy, also for reasons other than the FCC-push. When I read in the preamble "Further, through the exploration of a new realm of energies, discoveries will be made
    and the answers to existing mysteries, such as the nature of dark matter, may be found.", I would not believe I just read such a naive discovery-promise. Even if you were to stretch the definition of "discovery" a bit, this seems incompatible with the usual "5-sigma-standard" for finding something new.

    I'm also disappointed that the input of the early-career-researchers got chunked together with environmental aspects in a final block of statements. As if we are a nuisance like CO2...

    Sabine's blog gives me solace in these times :)

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    Replies
    1. This blunt lie just proves their fear that their discipline is dying.

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  10. How about around the moon? I'm entirely serious. The moon has no atmosphere and the moon's gravity could replace the magnets used to curve the particles.

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    Replies
    1. gravity is too weak, and making a good enough vacuum here is cheaper than going over the atmosphere

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    2. Maybe a much larger collider, say 500 km of radius, but with much cheaper superconductors, say HTC, would be cheaper overall. And instead of digging a tunnel, make it on open air, in a very dry place, like Atacama. The weather is extremely stable, it rearely rains, like few days every decades or less.

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  11. This is the essence of the problem: "Rather, collider physics got so gigantic that when somebody has a new idea, the typical answer no longer is “let’s do it” but “let’s discuss at the next committee”". And bigger means taking longer to build using current technology that ends up outdated by the time it's built.

    Compare this with the XENON1T experiment that is relatively cheap, yet cutting edge in the search for new physics.

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  12. I think I can safely say I am the dumbest person commenting in here, but even I can see just how seriously astray the physics community is right now. I sincerely hope there is no new collider. How can HEP be so interesting to so many people? Specially when there are so many basic things that are still not comprehended. Can anybody explain what entanglement is? No. Does anybody understand what a quantum superposition is? No. Does anybody even know what the wavefunction is? No. Does anyone know what QFTs are? No. Does anyone know how or why quantum mechanics gives rise to classical mechanics? No. Does anybody know how to use quantum theory to 'make people richer and countries stronger'? Sure. I can't believe that you would consider this blatant turbo pragmatic instrumentalism as a 'golden age' of science. Excuse me for being so cynical, but it seems to me that physics went off the rails in the 20th century after the 'shut up and calculate' mantra of extreme positivists took over the field. By the way, it's no wonder we still lack a theory of 'quantum gravity', since we don't even know what quantum theory is yet!!. I bet Descartes is surely rolling in grave (from laughter), looking at physicists fail miserably at applying the synthetic method, without first having succesfully gone through the (necessary) analytical step! Having said that, Sabine, I think you are a wonderful corageous woman and scientist. I read 'Lost in Math' and I loved it. I hope people like you keep trying to bring reason BACK into science.

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    1. A fair number of your cases you site as not understood are understood.

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    2. ol casi darkkii,

      There are others (dead philosophers and scientists) metaphorically rolling over and over even more, but what you wrote is right on target: No one understands *what* their models (which may be replaced 100 years from now) model.

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    3. Lawrence Crowell,

      do explain please.

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    4. Most of what you say with respect to quantum mechanics as not understood is in fact understood. Please look this up.

      Delete
  13. Ethan Siegel gas weighed in on this.

    https://www.forbes.com/sites/startswithabang/2020/06/23/will-the-lhc-be-humanitys-last-gasp-for-particle-physics/

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    Replies
    1. That guy is a True Believer.
      I find his blog sad and disheartening.
      Unreadable, really.

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  14. That branches of science come to an end is not new; (terrestial) geography essentially ended a century ago, and no modern geographer can aspire to make discoveries that match those of Christopher Columbus or William Cook. What is different and unsatisfactory with the situation in physics is that there are still unaswered questions, e.g. why m_p/m_e = 1836 or 1/alpha = 137. Those numbers are there for theorists to explain, and additional colliders will not change that.

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    1. I fear that the answer to these questions involves anthropic selection in a multiverse, and that then these questions will not lead anywhere. About understanding Dark Matter, we are now in the pre-Colombo phase. Maybe we are a few months before discovery, or maybe a few centuries

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    2. Many you are right Alessandro. But even then, they must be consistent with each other. There is an equilibrium to find between all parameters and a physics below - like for all other `levels' that we understand from elementary particles to cosmology. It is not because a theory has free parameters
      that nature is free. Nothing to do with anthropic selection - except maybe the other way when choosing a thesis or a subject of research.

      Best,
      J.

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    3. Nobody can of course rule out anthropic selection, but mass ratios don't seem qualitatively different from charge ratios or spin ratios. We don't try to explain why q_p/q_e = -1 or S_p/S_e = 1 with multiverse arguments. It seems to me that the main difference is that the values of these ratios are easy to guess.

      And captain Cook's first name was James, of course.

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    4. Quarks and electron masses have appropriate values that allow for many elements in nuclear physics. For example neutrons become stable inside nuclei. This and other accidents suggest that anthropic selection is playing some role.

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    5. I guess that dinosauric selection is not playing any role anymore.

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  15. Alessandro: is there a plan B for Cern in case the next collider project is scrapped? I hope so. Cern is not only the LHC and there are many other interesting/promising projects that cost a tiny fraction of the LHC, such as those on antimatter (eg, Alpha collaboration). Perhaps one should rethink of Cern as the host for many smaller-scale projects in fundamental physics, instead of being mainly identified with one super-big project. After all, start-ups are always more innovative than big dinosaur companies.

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    1. We can look at those centers that in the past pursued the high-energy frontier: some of them now do medium-energy precision experiments (muon magnetic moment, neutrinos, flavour, axion-like searches). A facility that offers high-energy particles can remain useful in some cases. But some theorists are trying to invent smart low-energy experiments possibly relevant for fundamental physics, and they got interesting ideas. Small experiments can be done locally, without putting lots of resources in one center.

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  16. For the first time in the history of particle physics the scientific program at a collider is mostly in the past light cone and there is no new collider in view.

    Change your perspective and a quite different scene unfolds: the universe has bazillions of colliders, any one of which makes the LHC look like a candle next to a supernova.

    Of course, no one is going to install a super-duper ALICE near a SMBH, in an AGN, any time soon.

    But what's stopping the combined genius of a thousand HEP PhDs from working out ways to do physics using blazars and hotspots (say)?

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  17. maybe to be cliche, i started physics in high school reading pop sci books by stephen hawkings and being immediately pulled in. what attracted me to follow this path besides the cool buzzwords& flashy concepts was the fact you could explain so much of nature via some very simple mathematical principles (F=ma etc). However when I read ahead on what the "biggest" problems were in particle physics and I read about the hierachy problem it was kind of a let down. so you don't like some of these numbers, big deal. I convinced myself it was because i was too stupid to understand it at the time. then in undergrad i took my first course on quantum field theory. to be fair that was another let down, it seems to be just spamming taylor expansions all the time, with no deeper meaning than curve fitting. To be clear, it is to my (limited) understanding there are some truly deep principles behind quantum field theory, but those who work on these principles dont seem to have anything to do with reality, and those who work with reality are just evaluating feynman diagrams. disillusioned, i am now a math graduate student (if i wanted to do deep QFT stuff might as well be a mathematician anyway was my reasoning when i made the transition) and only follow particle physics loosely through this blog and woit's. Though to be fair, half the reason the mathematical field i work on exists today is because one day some 40 years ago witten had a great idea (the other half being one day gromov had a great idea)...
    this is only to offer a snapshot of the many collective reality that captures what high energy physics is today, coming from someone who, had he been born 30 earlier, would have without a doubt become a high energy theorist.

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    Replies
    1. You don't seem to be quite as clueless as your handle says ;)

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  18. Help High Energy Loss Physics?

    ReplyDelete

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