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  1. S

    Can modern physics be understood qualitatively?

    I see you implicitly assuming a radical opposition between being mathematical (accurate) and being described in words without equations. I disagree with the idea of such an opposition. Indeed some of the math needs equations hard to understand for the majority, but I still see possibilities to...
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    Redesigning Mathematics Curriculum, thoughts?

    I also have a plan to redesign the math and physics curriculum. For this the way I found best was most often to just rewrite everything from scratch rather than collect external references, as in most cases I don't know good enough references compared to what I can make myself. My work remains...
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    Interesting articles online on academia and the PhD problem

    Moreover, my contribution was NOT off-topic. There are many ideas in my speech that are on-topic. But you need to actually take the time to read or hear it to notice this.
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    Interesting articles online on academia and the PhD problem

    Sorry but I see no legitimate right to pretend that I should shut up and let you conclude by such an awful and completely mad personal attack that you are making against me. I think I was clear about the problem. Not only my intelligence, my shyness, my natural temptation to respect and trust...
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    Interesting articles online on academia and the PhD problem

    Yes absolutely I was forced. Especially by my mother, who behaved as a tyrant, under the influence of some authoritative voices around (teachers, etc). I'm very tired of all those people who can't believe that this could happen. As I wrote here :
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    Interesting articles online on academia and the PhD problem

    I agree that, unfortunately, academic degrees are nonsense, and I'm very angry at people around who forced me to "study" up to PhD, following all that academic nonsense after I had already managed to rediscover a mathematical expression of General Relativity when I was 16. I just posted my...
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    An interesting way to get an interference pattern

    I think you made the right guess at the end of your video already : it's the pixels, the dense periodic succession of vertical lines in the structure of the screen. You can find more detailed explanations in the wikipedia article "Diffraction grating". An interference from 2 slits, alternates...
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    Definition of the Einstein Tensor

    I provide an answer this question in my page General Relativity : the Einstein field equation. I just wrote this page in the last days; see also the cosmology page linked there for a more intuitive, less formal description. This explanation is quite brief and assumes some familiarity with tensor...
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    The axiom of choice one a finite family of sets.

    It depends. Only if you have an explicitly finite family of nonempty sets, that you can list : E1,...En then you can use a proof whose length is proportional to n : Let x1 in E1, Let x2 in E2, .... Let xn in En then (x1,...,xn) is in the product, which is thus nonempty. But for the mathematical...
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    Simple exposition of universal expansion law in General Relativity

    Hello. For all those to whom the concepts of general relativity, big bang and universal expansion are not clear, I just updated my page of cosmology. There I presented a rather simple proof of the Friedmann equations, that are the particular case of the Einstein's equation of General Relativity...
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    What counts as an observation in QM?

    Why post links to articles that cannot be read online for free ? and the title does not sound like a consensual position. The concept of observation in QM indeed first appears as fuzzy and undefined. But it is only so as long as you keep applying the equations to a small isolated system. In...
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    A simple derivation of cosmological formulas

    Hello. I just added to my site a simple reasoning that quickly justifies the basic formulas of cosmology in General Relativity (Friedmann differential equations, assuming homogeneity and so on, including the role of the cosmological constant), without any heavy formalism (only assuming basic...
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    EPR thought experiment.

    According to John Baez's page of Open questions in Physics, I would describe things like this : QM does not predict anything like a preference for [either "horizontal" or "vertical"] polarization over diagonal polarization, because there is not such a thing as a possible measurement whose...
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    How is Entanglement Created?

    If you look for a process that can produced entangled particles, a natural one is to take a pair of electrons and separate them passively in a spatial manner without using a magnetic field. Then their spins are entangled (opposite to each other in any direction of measurement). Still it is not...
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    Energy in GR - side question

    Energy in GR can no more be described as a precise quantity simply obtained by integrating some explicit field along the space-like 3D surface we consider. This does not mean that there is no conservation of energy. But it takes a more subtle, complex form. In particular we can roughly define...
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    Conceptual underpinning(s) of the QM projection postulate

    In my opinion the only reasonable interpretation is the "Mind makes collapse" interpretation. I explained this starting with introductions of metaphysics, noting that purely mathematical laws of physics can only describe a mathematical universe, with a merely mathematical existence. There...
  17. S

    How does light lose energy as it travels over distance?

    I already answered this question in this other thread.
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    Introduction to Tensor Calculus and Continuum Mechanics

    I wrote a short introduction to tensors with a more abstract approach (not the usual approach of mathematicians either that complicates things and forgets the means to build complex formulas with the tensors they define) : I define an abstract and general concept of "tensorial expression"...
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    Online Quantum Physics courses

    I have written a simple but rigorous introduction to quantum physics expressing the core concepts of quantum states and measurements and their paradoxical aspects in a geometric language (making the mathematical consistency of the theory seem rather intuitive despite the paradoxes). This does...
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    Working on a movie and have a question on observer and double slit experiment

    What we can say may depend on some specific aspects of the experiment considered. If you consider just one closed physical system then we can say yes, physically, the observation of its state requires to physically interact with it, and thus affect it. For example if you have one electron and...
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    Tensor fields and multiplication

    To understand how the symmetric and the antisymmetric part are not all for tensors of rank k>2 : just notice that there are k! permutations that can send a tensor (such as those made of a product of linearly independent vectors) into k! linearly independent tensors. But the symmetric and...
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    Quotient set of equivalence class in de Rham cohomology

    Quotients of vector spaces can be written E/F = {x+F | x∈E} as the group law involved in such quotients is the law of vector addition. Any problem ?
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    Details of Stress-Energy-Momentum Tensor

    These descriptions are all true, so that a logical consequence of them is that the energy flux happens to equal the momentum density (*c2), while these are 2 different concepts. Usual conventions on tensors assume c=1 so that "mass" and energy are the same. If we don't put c=1, as the...
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    Charge distribution inside the electron ?

    This assumption is made out of the author's fancy. He visibly does not have a clue about quantum physics and how fundamentally different it is from classical mechanics. Quantum physics defines the electron as a fundamental particle. Thus it has no "internal structure" except for the cloudiness...
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    Are there two types of mass?

    The mass m and the energy E are two parameters related by In any given Galilean frame (for which the particle may be moving), E = γ mc2 where γ = 1/ √(1-v2/c2)) Thus m = (what would E appear to be relatively to the particle itself) / c2. The law of conservation of energy is that...
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    Many worlds interpretation, probability distribution

    I think the only effective meaning one can give to the many worlds interpretation is this : There is no such thing as probability. Probabilities would only be an appearance for the situation where existence is divided into several "possibilities" with their respective weights, that turn out...
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    Is this a good way to explain Skolem's Paradox?

    After this explanation by Hurkyl (that is rigorously correct), we may ask further questions : how is it possible that a function between given sets in the model, may exist outside the model but not inside it ? The theory gives a name to the set of all functions between given sets (say the set of...
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    Force = mass x acceleration

    Indeed the scientific quest does not systematically focus on the "why" questions, and does not worry if no absolute "why" can be found, however it did succeed quite well to find intermediate causes to phenomena, that is going some steps forwards in the chain of explanations : explain the laws...
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