All Questions

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2-to-2 vs 2-to-N with N>2 QCD processes

In high energy particle physics, what is the rough ratio of 2-to-2 hard scattered QCD processes to 2-to-N hard scattered processes with N>2. How can it be calculated? For example, in LHC, two protons ...
37 views

Can quantum entanglement work like this?

Lets say you have two entangled particles (A,B) and you already measured theirs spins and know that A has z+ and B has z- What will happen if after the measurement you will set the spin of B to z+ ...
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heating elements and arc welding?

In a water heater stove or arc welder, the most basic electric circuit is formed when one has a source (AC or DC) and 2 wires going to and from the heating element, in the case of the heater and ...
17 views

finding the unknown values of x and y in terms of base units in an equation [on hold]

express the following correct equation in terms of base unit to find the value of powers x and y ::: T=Kl(l with the power of x)g (g with the powers of y) find the values of x and y ?
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With respect to the Casimir effect, why can't the wavelengths of the virtual particles between two plates just “pass through” the plates themselves?

I've read over the years that the suppression of many of the possible wavelengths between the two plates in a Casimir experiment is what causes the phenomenon (top comment on this Askscience thread is ...
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Can anyone think of any astronomical phenomenon that could be due to engineering projects of an advanced civilzation? [on hold]

It has always seemed to me that there could very well be evidence of advanced civilizations in other parts of the galaxy/universe that are staring us in the face. Within a thousand years, heck, maybe ...
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What exactly is an integral kernel? [migrated]

I am not sure if I have seen integral transforms in the right way, but given a transform like fourier transform - its actually a basis transformation right ? $$F(y) = \int K(x,y) f(x) \text{d}x$$ ...
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Shielding of electric and gravitational force on particles inside a spherical shell

A cavity inside a conductor is shielded from outside electric influences. But, if you put charges inside the cavity, the exterior of the conductor is not shielded from the fields by the inside ...
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Using fiber optics to focus quartz tungsten halogen light

Our purpose is to make 1 mm spot size of quartz tungsten halogen light with 100 mm working distance for spectral imaging of wavelengths of 350-2000 nm. With some QTH light source and adapter on the ...
58 views

Periodicity of function as a result of superposition in Quantum Mechanics

Say we add infinitely many waves (states of definite momentum) so as to produce a function that gives a very well-defined position, does that addition(using Fourier series) make that function ...
57 views

Superposition of waves with different initial phase in Quantum Mechanics

In Quantum Mechanics, if a particle's state is a superposition of many states of definite momentum, then we say that it's position is well-defined (by the Heisenberg uncertainty principle, because ...
19 views

Dipoles in an external rotating field?

Consider a bunch of magnetic dipoles in $x-y$ plane in an external magnetic field $B(t)=B_0 \hat{z}+B_1(\cos\omega t~\hat{x}+\sin\omega t~\hat{y})$. The dipoles are rotating around $z$ axis and of ...
35 views

Manometer & pressure

I have trouble with a homework question in understanding how the manometer liquid responds to pressure changes. Any help will be much appreciated. The problem goes like this: A cylinder of diameter ...
21 views

total vorticity generation in 3D

In 2D flows, the total vorticity generation for an impulsively started plate can be found by measuring the circulation of the flow. This gives the vorticity generated per unit length. I would like ...
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How to obtain a lower mass bound for a unstable (or stable) particle from Poisson statistics?

Imagine you have a particle (stable e.g. if some R-symmetry or similar does exits) heavy or not so heavy... Question: how to guess a lower (upper bound as well) with the aid of Poisson statistics, ...
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Why does ice fall from the top of the ice tray first?

I haven't found an answer for this anywhere, so hopefully this community can help. It's not important at all that I know this but I'm curious. If you take a plastic tray of ice from the freezer and ...
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In my textbook, we calculated the rate at which an electric dipole radiates energy to be $Pwr = \frac{1}{4\pi \epsilon_0}\frac{2}{3c^3}\left(\frac{d^2 p}{dt^2} \right)^2$ where p is the dipole ...
54 views

Is time a finite resource?

I am struggling to find an answer for this question because time as we know it would end when we reach the heat death of a universe. Which would imply that is the end of time. I think I have a ...
62 views

The EFE - The 'Mother' of all equations of motion in the universe?

This question addresses the scope of general relativity. Scientists and engineers solve all sorts of physical problems in all sorts of fields and often to solve these problems a 'system' is defined ...
56 views

Electricity from vacuum

Can I generate electricity in complete vacuum without using any conventional sources? Using Casimir theory, according to him, he kept two plates nanometers apart in a vacuum. According to the law of ...
24 views

Scale-covariant decomposition of capacitance

I'm wondering if there is any good insight of how to evaluate a given capacitive geometry in such a way that it would be expressed as a function that depends only on two components: as a geometric ...
33 views

Locality defined in terms of the Lagrangian density

I've been reading through Matthew Schwartz's book "Quantum Field Theory and the Standard Model" and in chapter 24 there is a section on locality (section 24.4). In it he defines locality in terms of ...
31 views

Question about what a simultaneous measurement of entangled spins means

I was working through a problem I found online and ran into something that is confusing me. We have a system of three spin-1/2 particles, in the state  |\psi\rangle = ...
54 views

Why do people wear black in the Middle East?

I have read various dubious explanations as to why people often wear black in the heat, from cultural to somehow encouraging the evaporation of sweat (unconvincing). So, does anyone know what, if any ...
39 views

All possible photons wavelengths [duplicate]

As far as I know all photons come from electrons loosing their energy. I remember from physics and chemistry classes, that electron can loose or get only certain determined amount of energy. Also I ...
1k views

Confusion I have regarding Einstein's 1905 derivation of LT

In his 1905 paper, Einstein derives the Lorentz transformation using the two postulates of SR;constancy of $c$ for all inertial frames and the Invariance of the laws of physics for all inertial ...