100 Matching Annotations
  1. Last 7 days
    1. I think there is some interesting physics here. In particular, there is something curious about the difference between static and kinetic friction. First, let me make some observations and assumptions.
  2. Sep 2020
  3. Jul 2020
  4. Jun 2020
    1. tunnel splitting

      What exactly is tunnel splitting? The essay mentions this various times without clearly explaining what it is, and whenever I search it up online multiple things are said about it.

      From what I could understand, quantum spin tunnel splitting makes it so that the magnetization of a system can "switch between states with opposite magnetization that are separated by an energy barrier much larger than thermal energy". But what exactly happens during tunnel splitting? And why are there different ones mentioned in the article? [magnetization tunneling, zero-field tunnel splitting, ground-state tunnel splitting]

      I also understand that this phenomenon "defies classical physics" because of magnetization switching. How is that possible?

  5. May 2020
  6. Apr 2020
  7. Mar 2020
    1. Sempre ricordando che quando si parla di sfericità, l’elettrone non deve essere pensato come una pallina: si tratta di una particella elementare, dunque non strutturata e indivisibile, e per forma si intende in realtà la simmetria delle sue interazioni con i campi esterni, con altre cariche.
  8. Jan 2020
    1. Since water is denser than air, and the reflection is diffuse. A lot of light is internally reflected, thereof, increasing the probability of absorption at surface.

      The light is reflected back inside the water, because of the total internal reflection:

      • water is denser than air
      • angle of incidence is greater than the so-called critical angle

    2. This is because the light now has a layer of water to go through. And due to the reflectance of water, not all light at the air-liquid-interface (border between air and water) goes through the water. Some of it is reflected.

      Wet things become darker, because of the water consistency, reflectance that doesn't let all the light to transmit through it.

      The probability of light getting transmitted is: 1 - R1 (reflectance at the air-liquid interface)

    3. There are two types of reflection (two ways the wave can be thrown back). Specular Diffuse

      Two types of reflection:

      1. specular - light leaves the surface at the same angle it hits it
      2. diffuse - hitting light is scattered into all angles when reflected
  9. Dec 2019
    1. is 100%,

      It is definitely NOT 100%. However, it is safe to say "... is very close to 100% ..." or " .... is nearly 100% ..."

    2. to face the very

      "... were required to be robust against the high-multiplicity environment..."

    3. lead ion nuclei

      "Lead ion nuclei" is a little redundant. Stick to just "Lead ions" or "Lead nuclei".

    4. B-hadron

      "B" is usually reserved for the meson states of the b-quark. Since this is general, including potential baryonic states, I believe this should be "b-hadron".

    5. removing

      We're not removing overlapping regions, right? Rather, we are merging overlapping ROIs into one single ROI so as to incorporate the reality that they overlap. The image illustrates that, and not a removal of the intersection of two ROIs (which is what this language implies).

    6. selected

      "selected" or "produced"? Not sure what the intent is here for the underlying verb. ROIs would normally result (be produced) from the L1 trigger, then be used in the HLT. So is "produced" the right word?

    7. Expand the trigger description for the paper draft.

      This is needed.

    8. that combines the outputs of IP3D and SV1,

      MV2 doesn't use the output of SV1; it uses inputs employed by SV1 to make decisions, but makes them instead using the BDT architecture.

  10. Nov 2019
    1. Quantum Realism: A virtual reality would be subject to virtual time, where each processing cycle is one "tick." Every gamer knows that when the computer is busy the screen lags—game time slows down under load. Likewise, time in our world slows down with speed or near massive bodies, suggesting that it is virtual. So the rocket twin only aged a year because that was all the processing cycles the system busy moving him could spare. What changed was his virtual time.

      Thought exercise. Modern "Zen koan".

  11. Aug 2019
    1. This is, I thought, little more than an analogy with Boyle’s Law, one of the most striking early successes of the scientific revolution, which holds that the pressure and volume of a fixed amount of gas are inversely proportional.  Release the contents from a steel cylinder into a balloon and the container expands.  But it still contains no more gas than before.  Something like that must have been in the mind of the first person who first spoke of “inflating” the currency. From there it was a short jump to the way that classical quantity theory relies on the principle of plenitude – the age-old assumption, inherited from Plato, that there can be nothing truly new under the sun, that the collection of goods of “general price level” were somehow fixed.
  12. Jul 2019
    1. unitary operator is a surjective bounded operator

      Why must unitary operator only be surjective? Why not bijective?

  13. Feb 2019
    1. Deep learning approach based on dimensionality reduction for designing electromagnetic nanostructures


  14. Dec 2018
    1. Physics-guided Neural Networks (PGNNs)

      曹老师推来让我读读的 paper

  15. Nov 2018
    1. Opening the black box of deep learning

      上海大学的这个文有水文的倾向,没有提出任何实际数学的理论构想,整体还是太过唯象,企图给出DL 的物理理论解释。。。~ 扫了一眼,论点论证都比较牵强 ~

    2. Using Machine Learning to Predict the Evolution of Physics Research


    3. DeepSphere: Efficient spherical Convolutional Neural Network with HEALPix sampling for cosmological applications

      对具有方位信息的数据做卷积,实现了所谓的 3D 卷积,这对天文上的微博背景辐射(CMB)数据的应用很有意义。

    4. Toward an AI Physicist for Unsupervised Learning

      提出了 AI Physicist 这样的概念(paradigm),这也算是我的某种终极目标吧。


  16. Sep 2018
    1. The establishing of this mutual relationship between technology and physics is correct. But it remains a merely historiological establishing of facts and says nothing about that in which this mutual relationship is grounded. The decisive question still remains: Of what essence is modern technology that it thinks of putting exact science to use?

      It seems that the author is establishing a relationship between modern physics and technology as a circular relationship in that modern physics would not be possible if technology did not allow us to study it nor would technology advance should modern physics not be studied. So, essentially, modern technology is a method to reveal modern physics to us? Therefore, modern technology is also a revealing just as modern physics is a revealing, but that they mutually allow each other to do so?

  17. Jul 2018
    1. My conclusion from this long line of null results is that when physics tries to rectify a perceived lack of beauty, we waste time on problems that aren’t really problems. Physicists must rethink their methods, now – before we start discussing whether the world needs a next larger particle collider or yet another dark matter search.

      $$Insert LaTeX$$

    2. History has a second lesson. Even though beauty was arguably a strong personal motivator for many physicists, the problems that led to breakthroughs were not merely aesthetic misgivings – they were mathematical contradictions. Einstein, for example, abolished absolute time because it was in contradiction with Maxwell’s electromagnetism, thereby creating special relativity. He then resolved the conflict between special relativity and Newtonian gravity, which gave him general relativity. Dirac later removed the disagreement between special relativity and quantum mechanics, which led to the development of the quantum field theories which we still use in particle physics today.
    3. I think it’s time we take a lesson from the history of science. Beauty does not have a good track record as a guide for theory-development.
    4. Nevertheless, physicists continue to select theories based on the same three criteria of beauty: simplicity, naturalness, and elegance.
  18. Jun 2018
    1. Come on, harvest me! I’ll just change your world some more.

      I wonder a bit here about the idea of what in a meme might have a substrate type of effect to decrease the overall energy of the process to help it take off.

    1. In some sense, by studying one model deeply enough, we can study them all.

      This may be where math like category theory is particularly powerful as a map between these different areas which are really the same (isomorphic).

  19. Apr 2018
    1. we found advanced math and science courses advertised but not actually offered and specialized STEM programs eroded or discontinued within a few years of inception.

      Some interesting data points in this article.

    1. Yet, across the country, 2 in 5 high schools don't offer physics, according to an Education Week Research Center analysis of data from the U.S. Department of Education's office for civil rights.

      How widely known is this figure?

  20. Mar 2018
  21. Oct 2017
    1. You have probably heard about the hunt for dark matter, a mysterious substance thought to permeate the universe, the effects of which we can see through its gravitational pull. But our models of the universe also say there should be about twice as much ordinary matter out there, compared with what we have observed so far.

      Two separate teams found the missing matter – made of particles called baryons rather than dark matter – linking galaxies together through filaments of hot, diffuse gas.

  22. Sep 2017
    1. similarities between the two

      It would be interesting to discuss these similarities. From my non-chemist brain, I see more pattern and regularity in the chemical than in the social. Reminds me of NDTyson quote that physics is easy and sociology is hard because of the nonlinearity of human behavior.

  23. Apr 2017
    1. In 2013, François Englert and Peter Higgs were awarded the Nobel Prize in Physics for the development of the Higgs mechanism.

      'The Nobel Prize in Physics 2013 was awarded jointly to François Englert and Peter W. Higgs "for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN's Large Hadron Collider"'


    2. It is encoded in a compact description, the so-called 'Lagrangian', which even fits on t-shirts and coffee mugs.

      And, although the Standard Model may not be written in stone, the compact description certainly is: https://home.cern/cern-people/updates/2013/03/standard-model-set-stone

    3. Actually, the addition of \text{h}.\text{c}. is not required for term 2, since term 2 is self-adjoint.
    4. we recommend using the term 'transformation' instead of 'decay', as this more accurately describes the physical process

      OH MY GOD YES! <3

      The term "decay" when applied to non-macro phenomena is terribly misleading for anyone who isn't a physicist.

      "Decay" has several meanings (see the Wikipedia page), but it would not be foolish to assume that the term is commonly associated with things like decomposition or biological decays. Even in physics, an orbital decay is a gradual process.

      "Transformation" is much more applicable, and is a term I've used myself over the last few years instead of "decay" in this context.

    5. where μ and ν are Lorentz indices representing the spacetime components
    6. Feynman diagrams

      "Let’s draw Feynman diagrams!" and more, on the Quantum Diaries blog: http://www.quantumdiaries.org/2010/02/14/lets-draw-feynman-diagams/

      EDIT: This is already referenced in the article, but I'll leave this link up as a pointer anyway.

    7. quantum field theory

      Here's a beautiful (if long) explanation of QFT, on the Stanford Encyclopedia of Philosophy: https://plato.stanford.edu/entries/quantum-field-theory/

    8. The latest success was the verification of the Brout–Englert–Higgs field by ATLAS and CMS at CERN's Large Hadron Collider in 2012. Both experiments successfully detected the quantised excitation of the BEH field—the so-called Higgs boson.
    9. the Brout–Englert–Higgs field interacts with particles that have mass (all particles except the gluon and the photon)

      Or is it that all particles that interact with the BEH field have mass? ;)

    10. Matter particles can be divided into three groups: quarks (q) and antiquarks (\bar{q}); electrically charged leptons (\ell) and antileptons (\bar{\ell}); neutrinos (ν) and antineutrinos (\bar{\nu}). Gluons (g) couple to colour charge, which only quarks, antiquarks, and gluons themselves, have.

      Typically, though, the matter particles (fermions) are grouped into two, depending on whether they interact with the colour charge (quarks) or not (leptons, which include both the electrically charged leptons and neutrinos).

      However, the division into three groups, as shown here, is helpful!

  24. Feb 2017
    1. Their findings indicate that the set of all quantum field theories forms a unique mathematical structure, one that does indeed pull itself up by its own bootstraps, which means it can be understood on its own terms.

      What kind of structure? Group? Ring? Other?

    1. Goel’s specialty is “nanobiophysics” — she studies how physics and nanotechnology can effect biology and medicine.

      Wow, this is a specialty!

    1. The following is a statement of the laws of physics, not just my own personal opinion. "When power is Variable, Power controls airspeed." "When power is fixed, Pitch controls airspeed." In general, airplanes go where you point them, and go as fast as the power dictates. This is the easiest way to fly, and it works in all airplanes.
  25. Jan 2017
  26. Nov 2016
    1. The technologies in learning the physics are:- To bring improvements in the students’ physics ability. To bring improvements in the negative reactions of students towards physics.

  27. Oct 2016
    1. “What’s the world resting on now, without the tortoise to hold it up?”

      It's turtles all the way down

  28. Jul 2016
    1. Page 187 On hyper authorship

      "hyper authorship” is an indicator of "collective cognition" in which the specific contributions of individuals no longer can be identified. Physics has among the highest rates of coauthorship in the sciences and the highest rates of self archiving documents via a repository. Whether the relationship between research collaborators (as indicated by the rates of coauthorship) and sharing publications (as reflected in self archiving) holds in other fields is a question worth exploring empirically.

    1. I always found it incredible. He would start with some problem, and fill up pages with calculations. And at the end of it, he would actually get the right answer! But he usually wasn’t satisfied with that. Once he’d gotten the answer, he’d go back and try to figure out why it was obvious. And often he’d come up with one of those classic Feynman straightforward-sounding explanations. And he’d never tell people about all the calculations behind it. Sometimes it was kind of a game for him: having people be flabbergasted by his seemingly instant physical intuition, not knowing that really it was based on some long, hard calculation he’d done.

      Straightforward intuition isn't just intuition.

  29. Jun 2016
    1. ***By which I mean, it’s even in Wikipedia

      Doesn't give reference on how the physicist detector models are known in wikipedia

    2. Actually, I didn’t need Holmesian deductions to conclude that Aad et al. aren’t using a conventional definition of authorship. It’s widely known*** that at least two groups in experimental particle physics operate under the policy that every scientist or engineer working on a particular detector is an author on every paper arising from that detector’s data. (Two such detectors at the Large Hadron Collider were used in the Aad et al paper, so the author list is the union of the “ATLAS collaboration” and the “CMS collaboration”.) The result of this authorship policy, of course, is lots of “authorships” for everyone: for the easily searchable George Aad, for instance, over 400 since 2008.

      Physicists authorship models

    1. iomedical collaborations are moreheterogeneous and socially diffuse in character and do notappear to have the same degree of multilayered, internalreview as HEP research collaborations. T

      biomedicine is a less homogeneous group and so less internal trust

    2. TheHEP research community is thus characterized by highlevels of internal scrutiny, mutual trust—witness, for in-stance, the institutionalized practice of relying upon, andciting, preprints—and peer tracking, such that it is notsusceptible to systematic fraud. Contrary

      physicists live in a very trustful, observant, world; also they do a lot of internal, pre-referee, review

    3. The answer probably has to do with the relative intensityof socialization and oral communication (Traweek, 1992,pp. 120 –123), along with the character of the organizationalstructures and value systems, which define collaborations inlarge-scale, high-energy physics and biomedical research.

      Why is there less soul-searching about hyper-authorship in HEP? disciplinary differences

    4. owever, multipleauthorship and hyperauthorship are not problematized byphysicists as they are by the biomedical community.

      Multiple authorship is not problematised in the HEP community as it has in biomedicine.

    5. Thisarticle(a)beginswithabrief,historicaloverviewofscholarlypublishing,focusingontheroleoftheauthorandtheconstitutionoftrustinscientificcommunication;(b)offersanimpressionisticsurveyandanalysisofrecentdevelop-mentsinthebiomedicalliterature;(c)explorestheextenttowhichdeviantpublishingpracticesinbiomedicalpublishingareafunctionofsociocognitiveandstructuralcharacteris-ticsofthedisciplinebycomparingbiomedicinewithhighenergyphysics,theonlyotherfieldwhichappearstoexhibitcomparablehyperauthorshiptendencies;and(d)assessestheextenttowhichcurrenttrendsinbiomedicalcommuni-cationmaybeaharbingerofdevelopmentsinotherdisci-plines

      Great overview of what is going to happen in article:

      1. History of authorship
      2. Survey of state of biomedicine
      3. "extent to which deviant publishing practices in biomedical publishing are a function of sociocognitive and structural characteris-tics of the discipline by comparing biomedicine with high energy physics, the only other field which appears to exhibit comparable hyperauthorship tendencies"
      4. Assess extent to which biomedical trends may foreshadow trends in other fields.
    1. Combined Measurement of the Higgs Boson Mass in pp<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi><mi>p</mi></math> Collisions at s√=7<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>7</mn></math> and 8 TeV with the ATLAS and CMS Experiments

      ATLAS Collaboration, CMS Collaboration, G. Aad, B. Abbott, J. Abdallah, O. Abdinov, R. Aben, et al. 2015. “Combined Measurement of the Higgs Boson Mass in $pp$ Collisions at $\sqrt{s}=7$ and 8 TeV with the ATLAS and CMS Experiments.” Physical Review Letters 114 (19): 191803. doi:10.1103/PhysRevLett.114.191803.

      This is the 5000+ author physics paper

      Note a) that they actually credit the authorship to the collaborations on the byline; and b) that they have two plus pages of secondary affiliations!

    1. The four new synthetic elements have been named.<br> 113 nihonium (Nh)<br> 115 moscovium (Mc)<br> 117 tennessine (Ts)<br> 118 oganesson (Og)

  30. Apr 2016
    1. The notion that counting more shapes in the sky will reveal more details of the Big Bang is implied in a central principle of quantum physics known as “unitarity.” Unitarity dictates that the probabilities of all possible quantum states of the universe must add up to one, now and forever; thus, information, which is stored in quantum states, can never be lost — only scrambled. This means that all information about the birth of the cosmos remains encoded in its present state, and the more precisely cosmologists know the latter, the more they can learn about the former.
  31. Feb 2016
    1. Sabrina Gonzalez Pasterski is a 22-year-old MIT graduate and Harvard PhD candidate in physics whose talents have gained a lot of attention.


    1. An all-star international team of astrophysicists used an exquisitely sensitive, $1.1 billion set of twin instruments known as the Laser Interferometer Gravitational-wave Observatory, or LIGO, to detect a gravitational wave generated by the collision of two black holes 1.3 billion light-years from Earth.
  32. Jan 2016
    1. Ultimately,the theory has been shown to be incorrect, and has been epistemically replaced by the theory of General Relativity. Nevertheless, the theory is able to make exceptionally good approximations of gravitational forces –so good that NASA’s moon missions have relied upon them.

      General Relativity may also turn out to be a "dumb model". https://twitter.com/worrydream/status/672957979545571329

  33. Dec 2015
    1. Pronunciations for hexadecimal numbers:<br> 0xB3 "bibbity-three"<br> 0xF5 "fleventy-five"<br> 0xDB "dickety-bee"

      BZARG is the work of Tim Babb, who lives in the San Francisco Bay Area, and is Lighting Optimization Lead for Pixar Animation Studios.

      This blog focuses primarily on graphics, physics, programming, and probably some philosophy and fiction

  34. Oct 2015
    1. In a landmark study, scientists at Delft University of Technology in the Netherlands reported that they had conducted an experiment that they say proved one of the most fundamental claims of quantum theory — that objects separated by great distance can instantaneously affect each other’s behavior.

      The researchers describe their experiment as a “loophole-free Bell test” in a reference to an experiment proposed in 1964 by the physicist John Stewart Bell as a way of proving that “spooky action at a distance” is real.

    2. the strongest evidence yet to support the most fundamental claims of the theory of quantum mechanics about the existence of an odd world formed by a fabric of subatomic particles, where matter does not take form until it is observed and time runs backward as well as forward.
    1. "It's intriguing that you've got general relativity predicting these paradoxes, but then you consider them in quantum mechanical terms and the paradoxes go away," says University of Queensland physicist Tim Ralph. "It makes you wonder whether this is important in terms of formulating a theory that unifies general relativity with quantum mechanics."
  35. Jun 2015
    1. Schrödinger thought that the Greeks had a kind of hold over us—they saw that the only way to make progress in thinking about the world was to talk about it without the “knowing subject” in it. QBism goes against that strain by saying that quantum mechanics is not about how the world is without us; instead it’s precisely about us in the world. The subject matter of the theory is not the world or us but us-within-the-world, the interface between the two.
  36. Oct 2014
    1. The discovery of the Higgs Boson has been a testament to the co- herence of the Standard Model of Physics, but the way in which this boson interacts with a fundamental class of particles known as leptons has yet to be explored, due to the rarity with which the Higgs Boson decays into leptons and the event's similarity to the decay of other particles such as the Z Boson. By creating a machine learning model to accurately determine whether a Higgs Boson is decaying into tau particles (a type of lepton) within a particle accelerator, physicists will be able to explore the nature of the Higgs's interaction with lep- tons. Our model serves to contribute to the work of others involved in the Higgs Boson Machine Learning Challenge, a crowdsourced e ort to generate a satisfactory classi cation model to be used at CERN's facilities, where the Higgs Boson is studied.

      Really interesting abstract.