As of May 31, 2023, we have updated our Code of Conduct.


A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.

The axion is a hypothetical spinless particle. It underlies a conjectured solution of the "strong CP problem" of the standard model and makes for a good dark matter candidate.
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Baryon Acoustic Oscillations (BAO) are periodic density fluctuations in the density of matter in the universe. BAO is observed in the large-scale structure of the universe (e.g. distribution of clust…
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Baryons are hadrons (particles composed of quarks) with an odd number, at least 3, of valence quarks. The term is also often used in astrophysics, e.g. "baryonic matter", with a much looser definition…
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Devices to store chemical energy and convert it to electrical energy.
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Bell's inequality is a no-go theorem contrasting crucial correlations of physical observables in QM to those of the world as described by classical mechanics, essentially local hidden variables theori…
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for questions relating to Bernoulli equation [named after its discoverer, the Swiss scientist Daniel Bernoulli (1700–1782)], an equation governing fluid flow for an incompressible steady f…
The phase difference acquired over the course of a closed loop which results from the geometrical properties of the parameter space of the Hamiltonian.
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for questions beyond the standard laws of physics (General Relativity and the Standard Model) if a more specific tag, like "string-theory", "loop-quantum-gravity", "supersymmetry", etc.…
According to the current cosmological theories, it's the model that explains the early life of the universe, starting from a rapid expansion of hot and dense matter.
applied to list-like questions which have no single answer. A few of these were asked early in the site's history, but they are no longer allowed.
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Binary stars are a system of two stars rotating around their center of mass, as opposed to single stellar systems such as our solar system.
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Please use binding energy in the context of the atomic scale and/or atomic systems. This can be used in nuclear reactions.
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Questions about biology are OFF TOPIC and should be asked on the Biology Stack Exchange. However, questions about biology in the context of physics (e.g., biophysics) can be on topic here if the prima…
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The use of methods from the physical sciences to aid in the study of biological systems. Note that biophysics questions are only allowed if they are mainly about physics.
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A black body is an object that absorbs all electromagnetic radiation regardless of frequency, and emits black body radiation. Such an object is just theoretical, but nevertheless, it is a useful model…
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A firewall is a proposed solution to the black hole information paradox that resolves an apparent issue with black hole complementarity. The firewall hypothesis predicts a "wall" of energy at the eve…
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A black hole is a region of spacetime from which nothing can escape. More formally, the future light cone of any observer within the black hole is completely contained in the black hole, and the blac…
A geometrical representation of the pure state space of a two-level quantum mechanical system (qubit), used in quantum mechanics and computing.
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