# All Questions

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### On Carnot engine and heat pollution [on hold]

Suppose a power plant uses a Carnot engine to generate electricity, using the atmosphere at 300 K as the low-temperature reservoir. Suppose the power plant produces 1 Ã— 106 J of electricity with ...
25 views

### Global Hyperbolicity in spacetime Manifold [on hold]

If space time is timelike or null geodesically incomplete but cannot be embedded in a larger spacetime then we say that it has singularity. What does incompleteness means here?
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### What is more basic thing to explain phenomenons : Energy or Force?

You know many physical happening are explained by considering forces or we can explain these phenomenon using energy (like energy conservation, etc.). so i was wondering that explaining the physical ...
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### Very precise calculation of the heliocentric position coords (X, Y, Z) the point of coordinates (N/S, W/E degrees) on Earth

I need a very precise calculation of the heliocentric position coords (X, Y, Z) the point of coordinates (N/S, W/E degrees) on Earth. Currently, thanks to the algorithm which generates the position ...
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### Books for students [duplicate]

Can any one please suggest me books for physics. I need a book for good theory and concept . And a book for practice , it should contain some solved questions. The both the books should contain ...
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### What is exactly the difference between an active and passive frequency standard?

In the case of passive atomic frequency standard, we take an atomic reference which has a resonant frequency response centered at certain particular frequency. Then we take a local oscillator and tune ...
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### What to do when the fields are arranged in a matrix?

I am dealing with a Lagrangian in which the fields are arranged in an $N\times N$ matrix and i have to find the minima of the potential. Usually i would write the Lagrangian in components and then ...
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### Mathematical formula for maximum sound pressure level [on hold]

I googled a math equation for calculating Maximum Sound Pressure Level but couldn't help myself. What is it?
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### Scattering in Schrödinger picture [on hold]

If we look at a scattering process in the SchrÃ¶dinger picture for a Hamiltonian $H = H_0(t) + V(t)$ where $H$ is independent of time (because we examine a theoretical situation after accelerating ...
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### Are pure Dirac fermions (electrons, quarks, …) allowed to have effective Majorana mass?

Charged particles such as electrons and quarks are not allowed to have a hard Majorana mass (see here). With 'hard' I mean an explicit mass term in the Lagrangian which would break the corresponding ...
I have this Lagrangian density $$\mathcal{L} = \frac{1}{2}(g^{\mu\nu}\partial_\mu\phi\partial_\nu\phi^* - \mu_0^2\phi^*\phi)$$ with $g_{\mu\nu} = g_{\mu\nu}(x^\alpha)$ and I need to get the Noether ...