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This Question is Beyond the Scope of This Site This subject takes much, much more room to precisely answer than a single post can do here. People get degrees to answer this question. A single post here will not answer your question with exactness. A few years studying physics and then going on to study material science- that will answer your question as ...


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Silicon is interesting because it is a semi-conductor. That is, it can be used to build transistors and other devices. Moreover, with the appropriate techniques the same silicon wafer can be used to build transistors, diodes, resistances, capacitors and electrical connections. Now, transistors, diodes and resistances can be connected to build logical gates. ...


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This is just a convention and nothing more. We treat the $\mathrm{dm}$ as a single symbol. Note that there are much stranger notations of powers, such as squared sines: $$ \sin^2(x) = \big(\sin(x)\big)^2 $$ You can not treat this formally as written - it's not a square of the sine, but the square of the value it returned.


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In your example, ab is implied to be a multiplication - a*b; but dm is a single indivisible token. Imagine second2 - that doesn't imply that the last letter should be squared, and it's the same with decimeters. Mathematical notation is often ambiguous, and leaves many things implied and underspecified with the expection that the reader will fill the gaps ...


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$1\text{ dm}^3$ can be seen as a shorthand way to write $1\text{ dm}\cdot 1\text{ dm}\cdot1\text{ dm}$. The motivation behind this is that the quantity $1\text{ dm}^3$ represents the volume of a cube with each side of length $1\text{ dm}$, and the way to find the volume is to multiply the three sides: $LWH=(1\text{ dm})\cdot(1\text{ dm})\cdot(1\text{ ...


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The thing is that $\mathrm{dm}$ is a single symbol, not a combination of two symbols. Yes, it can be understood in terms of a prefix and a base indicator, but it is still a single symbol. An analogy to the concatenation of variable is inappropriate. Reference to an authoritative statement: The grouping formed by a prefix symbol attached to a unit ...


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They're not used because it's ugly to read such texts with parentheses and it's time-consuming to write it down. A decimeter is indeed a "product" of "deci" and a meter, so the origin is analogous to the product of two real numbers $ab$. But once we define the new derived unit ${\rm dm}$, we treat it as a single object, so it really means what you would ...


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If only the cyclic coordinate $q(t)$ varies with time (if it doesn't, $q$ is superfluous), the Lagrangian, or the essential physical situation, doesn't vary. Hence the initial value of $q$ doesn't determine the path, which is only possible if the path is closed.


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I believe it was Xiao-Gang Wen in 1989, see also this 1994 paper by him and his collaborators http://dao.mit.edu/~wen/pub/ednab.pdf He's at MIT. I was once hosting a seminar by him, he is one of the most creative and playful folks in this segment of condensed matter physics. The paper above contains some other relevant references, including a paper by ...


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A clear case of "abusing dimensional analysis". Perhaps not the first time that a physics stack-exchange question is answered by xkcd:


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This is a really interesting question, and I've no precise answer... So let me just tell you a few random things. First, I'd like to say that mesoscopic physics emerges simply because it was technologically available, as most of the emerging field actually. It is indeed a big field, also because of its potential industrial interests (the famous nanoscale = ...


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I recommend reading this first: P. Cotta-Ramusino, E. Guadagnini, M. Martellini, and M. Mintchev. Quantum Field Theory and Link Invariants. Nuclear Physics B, B330:557, 1990. Also Guadagnini has a nice book("The Link Invariants of the Chern-Simons Field Theory") on the subject but it is hard to find.


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I think the shaking action causes the batteries to move slightly, thus 'scraping' the contact area on the batteries and the contact elements in the remote. This improves the conductivity, and so on. Certainly I've had success opening the battery compartment and physically rotating the batteries and/or scraping the contacts gently. I think it's unlikely ...


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Batteries contain various liquids that are important for the voltage to be produced. Sometimes, the liquid – even water – may turn to gas and it is permanently lost, along with the capacity. Sometimes, the liquid just moves to one side of the battery which is also bad. Shaking a weak battery may homogenize the concentration of the liquid across the battery. ...


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This answer is just my opinion, but I think that if ever there were to be a Theory Of Everything, it would probably be radically different from any of the mainstream theories we currently have. As such it would have to incorporate all the experimental results of the mainstream, and that would be too big a task for one person. So collaboration is the obvious ...


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Quantum Mechanics and Path Integrals: This is a book every physicist, or student of physics, should study. Here the author describes the principle of action in quantum physics. It is not a minimum action principle, like in classical mechanics: you can, however, derive the classical minimum principle from it, in the classical limit. Why is this important? ...


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I suspect that the reprint was withdrawn, rather than the original article; probably, for copyright reasons.


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To study the precise mathematical formulation of path integrals, you actually need probabilistic tools. The path integral is a stochastic integral with suitable measures, such as the Wiener measure associated with brownian motion. The ideas used by physicists are very useful, but not always mathematically accurate, and rely more or less on justification by ...


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I recommend two resources: Feynman's original book called Quantum Mechanics and Path Integrals. This contains most of the prerequisites in the first two chapters, but you will need some maturity to get through them. A. Zee's quantum field theory book Quantum Field Theory in a Nutshell for its friendly chapter on them.


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Feynman's path integral formulation is closely related to the action principle of classical mechanics, which relies heavily on the calculus of variations. You need to learn, essentially, how to minimize a functional. Prerequisites are pretty much just calculus (multivariable, hopefully), as well some classical mechanics to understand the motivation behind ...


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Work. Potential energy exists because of some force that exists, and moving an object relative to that force causes work to be done. And by the work-energy theorem, the work done on an object is equal to the change in kinetic energy of that object.


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This is not specific to converting potential energy to kinetic, but the term you're looking for might be "transduction" or "to transduce"- the process of converting energy from one form to another.


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I believe there is no complete database that would provide you with a reference to an authoritative review on every chosen topic. There are obviously journals mentioned by user just-learning that often provide high-quality reviews from people at the frontier of their area. These journals in which the most authoritative reviews independent of the field are ...


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The ADS database contains 11 million records of publications in astronomy, physics and geophysics, as well as arXiv preprints.


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what about the arxiv? You can find a lot of papers even before the are published and also search by research area (hep-ph, th-ph,...) arxiv Google schoolar might help too.


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Try Microsoft Academic Search , it has huge section devoted to Physics and you can search by string query or authors and pay attention to review journals, where articles were published, as @just-learning suggested.


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SSC: synchrotron self-Compton BBC: Compton upscattered blackbody radiation; Compton upscattering of stellar blackbody photons XC: upscattering of photons emitted by the accretion flow; accretion flow photons From: http://arxiv.org/abs/1307.1309 and http://arxiv.org/abs/1403.4768


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We don't really understand why charge is quantized. Nor we do know if there ought to be magnetic monopoles. These two things seem linked. Dirac gave an argument for charge quantization in the early days, but this presupposed the existence of a magnetic monopole. In Maxwell's equations, it would be completely natural to imagine the existence of magnetic ...


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Based on the Wiki article, we're looking at something on the order of millions for $N$ just in our galaxy. So far, we see there to only be us. This could be the result of a failure in the theory that led to the Drake Equation, or a lack of knowledge regarding the parameters. We really don't know too much regarding the parameters, thus extensive efforts are ...


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Well, it is known that $N \geq 1$ (^o^) On a more serious note, the Kepler Space telescope is providing greatly improved estimates of the parameters $f_p$ and $n_e$.


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The Wikipedia article on the Drake equation includes a section giving the current estimates for its parameters. I won't copy and paste the text here: suffice to say that $R_*$ and $f_p$ are reasonably well known. We're beginning to get a handle on $n_e$ from the exoplanet surveys. However we have little or no experimental evidence to assign values to any of ...


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This question is a bit open-ended so I'm not sure if it's appropriate for this site, but I'll try to answer it anyway. What you're talking about most likely is developing so called 'maturity' in math and physics. This isn't really a well-defined concept, but most people have an intuitive sense of what it means; if you have maturity in physics this most ...


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I'll take a stab at each of your questions one by one: How does the research in theoretical physics differ from mathematics? Research in physics and research in mathematics are very different activities. While they both use mathematics as a tool to communicate ideas, they are doing so to accomplish very different goals. Remember that conclusions in ...


1

To my knowledge, there isn't a specific term for these types of gasses. In your question you name "substance" while you list elements. Many different molecules are gaseous at room temperature; however, only a few of the elements are. I'll look at both. They come from different parts of the periodic table but do have a couple of features in common: ...


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Just an extra thing to add: take a look at Feynman's wonderful point of view on this subject. It's very similar to what Daniel and Void answered, in my opinion- just more interesting (no offense to Daniel and Void- I think Feynman is more interesting than everyone!).


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First, you can be sure that a PhD student will almost always work on a very particular and nuanced topic in either of the fields. Even if you do a PhD in string theory, you might just ask about some very specific class of solution or about a prediction of observation of a very special measurement. It is hard to find "big" questions which haven't been asked ...


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The fundamental difference is, that the physicist can develop stuff based on heuristics and physical intuition, while the mathematician has to prove every single step he does. The work of justifying the stuff the theorist does, is again the mathematician's part, the theorist is happy as long as his theory works. For a nice example for the difference, I ...


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I think you are just being a bit too broad in your categories. Take for example classical mechanics. Yes there is a broad split between newtonian and analytical mechanics, but within each of those there is a range of pictures you can use to understand a situation. On the analytic side there is the Lagrangian and Hamiltonian formulation. On the Newtonian side ...


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The quote continues: "He knows that they are all equivalent, and that nobody is ever going to be able to decide which one is right..." So I don't think classical gravitation versus generally relativity is a good example, because they can be distinguished experimentally. Perhaps the Schrodinger versus Heisenberg formulations of quantum mechanics.


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When I studied quantum mechanics, my professor advised that I avoid the question "which is more fundamental?" and replace it with "which is more useful?". The problem is that our brains are programmed to think classically, so many concepts in QM have no classical analogue. For that reason, we usually discuss them mathematically in order to avoid ambiguity. ...


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What follows is an answer from an experimental particle physicist, i.e. one who has more knowledge of theoretical physics than the average educated person, but not in a position to teach it :). I can use theoretical results and study data and validate or falsify a theory. I would like to know that if what we conceptualize as a "field" is merely an ...


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This is a tricky question because it asks about the meaning of words. People use the word "particle" to refer to various, not always well defined, notions in physics. In the end, I think the simplest and more correct single way to categorize the terms is to interpret "particle" as "excitation of a field". For example, if someone says "There are two ...



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