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  2. Dedekind's "different": sources, definition, original name

    math.stackexchange.com/.../dedekinds-different-sources-definition-original-name

    See : Nicolas Bourbaki, Elements of the History of Mathematics, (French ed, 1984), page 102 : in 1882, Dedekind completes the theory [of ideals] by introducing the different, which gives him a new definition of the discriminant and allows him to specify the exponents of the prime ideal factors in the decomposition of the latter.

  3. I wrote my definition just from the top of my head, and it works nicely whenever the usual divergence at a point is nonzero, at least :) $\endgroup$ – user79482 Commented Aug 17, 2020 at 14:30

  4. optics - Brightness of light sources - Physics Stack Exchange

    physics.stackexchange.com/questions/191678/brightness-of-light-sources

    1. You have correctly observed that "brightness" has two components, a physical one that is a measure of the actual physical photon flux and a physiological, which represents the human eye's response to that flux. The latter is usually characterized by a "standard eye sensitivity" which is derived from averages of many physiological measurements.

  5. definition - What exactly is the "coherence" between waves? -...

    physics.stackexchange.com/questions/144334

    4. Coherence means a constant phase relationship; the phase difference could be anything, such as π π or 7π/4 7 π / 4. Naively, that means that two waves are coherent if and only if they have the same frequency, which makes the idea of coherence sound silly. However, it actually stands in for a lot of real world effects that can destroy ...

  6. Graph terminology: Are there terms for "a source or a sink" and...

    math.stackexchange.com/questions/3881024/graph-terminology-are-there-terms-for...

    There is some prior art, but nothing that will be universally recognized. In the context of series-parallel digraphs, the source and sink are called the terminals of the graph.

  7. Citations in Math Papers - Mathematics Stack Exchange

    math.stackexchange.com/questions/91645

    1. Part of "what deems something cite-worthy" is: the author. You might think the reader is well-served by being made aware of a particular paper, and cite it. – Michael Hardy. Dec 15, 2011 at 4:38.

  8. What actually is white light? - Physics Stack Exchange

    physics.stackexchange.com/questions/605951/what-actually-is-white-light

    17. At first glance, the question has a trivial answer: white light is light that contains a roughly uniform mixture of photons of all visible wavelengths. Light can white when it has a non-uniform mixture of wavelengths that excite the three color receptors in the human retina the same way a uniform mixture does.

  9. What is difference between homogeneous and isotropic material?

    physics.stackexchange.com/questions/153008

    With your notation although is not clear. For example, if we take your definition and ask if a system is homogeneous with respect to refractive index then it doesn't make sense to apply your first definition. Maybe for density it makes sense, but not for all properties. $\endgroup$ –

  10. What is a heat source and heat sink in relation to thermodynamics...

    physics.stackexchange.com/questions/151285/what-is-a-heat-source-and-heat-sink...

    As mentioned above, but important to stress, the temperature of the reservoir does not change when heat is added or extracted because of the infinite heat capacity. As it can act as a source and sink of heat, it is often also referred to as a heat reservoir or heat bath. And in the context of a thermodynamic cycle, a heat source and a heat sink.

  11. While irradiance refers to incoming power, the radiance is used for two cases: angle-dependent diffuse reflection (BRDF) emission from light sources. E.g. radiance in direction of the optical axis of a LED is higher, than its radiance at an angle of 15°. Optical simulations / ray tracing calculate the irradiance on surfaces.