4
votes
3answers
858 views

Incompressible quantum liquid

In condensed matter physics, what does the term incompressible in incompressible quantum liquid mean?
7
votes
1answer
912 views

CP Violation of the CKM Matrix

Considering the relation between the $SU(2)_{WEAK}$ partners of the $|u \rangle$, $|c \rangle$, and $|t \rangle$ mass eigenstates and the corrseponding downtype eigenstates $ \left( ...
13
votes
1answer
907 views

What is a general definition of the spin of a particle?

In quantum field theory, one defines a particle as a unitary irreducible representations of the Poincaré group. The study of these representations allows to define the mass and the spin of the ...
4
votes
4answers
2k views

Increasing mass' effect on the balance between centripetal force and centrifugal force

Okay, this is nothing more than a thought experiment which popped into my head while driving home from work today. Take the case of a single body orbiting another, larger body, as in a planet and a ...
7
votes
3answers
375 views

Where does the light of the Big Bang come from?

I'm wondering whether the residual light of the Big Bang comes from one particular direction and what possibilities do we have to detect its position?
5
votes
2answers
158 views

Is there any scientific evidence that demonstrates why time passes?

Is there any scientific evidence that demonstrates why time passes? Or is it just an opened question?
4
votes
2answers
246 views

Are we going to be able to travel trough space deforming the space-time?

I'm not talking about the speed of the spaceship. If we can deform space-time we needn't any type of propulsion. And how can the travel affect to it's pilots? Can they survive?
4
votes
2answers
693 views

Implementing simple atom model using density functional theory (DFT)

I am trying to write computer code which will find the energy and density function for an atom with $Z$ protons and $N$ electrons. I am working in 1D for simplicity and would like to make the overall ...
4
votes
1answer
201 views

What does the appearance of a classical particle fundamentally reduce to?

I've been reading an article that describes what seems to be a classical particle as a regularity in the global wavefunction over a quantum configuration space: When you actually see an electron ...
3
votes
2answers
148 views

How does gravity behave outside the geoid?

I was watching a program about the geoid recently and the relative "height" of the Himalayan plateau gave me an idea. It makes sense for the geoid to be "highest" (is that the correct term?) there as ...
-3
votes
2answers
371 views

About change in velocity of a light wave as it enters a different medium [closed]

$\dfrac {sin\theta1}{sin\theta2}=\dfrac {v1}{v2}=\dfrac {n2}{n1}$ I understand this equation, but what is the velocity of a light wave going through air and what is the velocity/change in velocity as ...
2
votes
1answer
483 views

Equations of motion in 2D [closed]

I'm struggling with a seemingly simple problem in 2D motion. Basically, the question is, given accelerations in $x$ and $y$ ($a_x$ and $a_y$) as well as the angular velocity ($\omega$), how can we ...
7
votes
2answers
958 views

Einstein's Gedanken Experiment that lead to the Special Theory of Relativity

Once, I read that Einstein founded the special relativity theory by imagining how an observer moves at the speed of light. How does this thought experiment work? How to reach from this imagination to ...
9
votes
1answer
18 views

Ring height stats?

I'm working on a basic simulation system which will include planets with rings, I want to create dust and asteroids within a 3D ring but I'm struggling to find any stats on the sort of height ranges a ...
6
votes
3answers
869 views

Can we prove that the universe is finite or infinite? [duplicate]

If I say that the universe is finite, how can you say with certain that I am wrong?
10
votes
3answers
2k views

A book on quantum mechanics supported by the high-level mathematics

I'm interested in quantum mechanics book that uses high level mathematics (not only the usual functional analysis and the theory of generalised functions but the theory of pseudodifferential operators ...
3
votes
2answers
4k views

Will the hole on a metal disc expand or contract upon heating? [duplicate]

Possible Duplicate: Will a hole cut into a metal disk expand or shrink when the disc is heated? The metal disc of diameter D1 has a hole in it and the diameter of the hole is D2 (D2 Now, ...
6
votes
2answers
201 views

Io - Turned inside out

In a lot of the descriptions of the moon Io it frequently states that the moon, because of volcanic activity, has been literally "Turned inside out". What exactly is meant by "Turned inside out" and ...
16
votes
6answers
169 views

Multiqubit state tomography by performing measurement in the same basis

For a $n$-qubit state $\rho$ we perform all projective measurement consisting of one-particle measurements in the same basis, that is, $$p_{i_1i_2\ldots i_n}(\theta,\varphi) = \text{Tr}\left \{ \rho ...
3
votes
1answer
82 views

Is there an abstract notion of heat within a microscopical system?

The microstates of a system are said to be unobservable. I can introduce the entropy as a measure of the number of microstates, which lead to the same macroscopic variables. So in this detailed ...
2
votes
1answer
357 views

Rocket drive and conservation of momentum

I am currently reading through some lecture notes of Physics 1 and in a chapter about the dynamics of the mass point, there is an example covering the rocket drive. Let $v$ be the velocity of the ...
8
votes
5answers
2k views

Direction of rotation of proton in magnetic field--opposite to a dipole

Chatroom created by @pcr for discussing this: http://chat.stackexchange.com/rooms/2824/direction-of-rotation-of-proton-in-magnetic-field Here's a small paradoxical question I was asked a long ...
14
votes
1answer
167 views

Monte Carlo integration over space of quantum states

I am currently facing the problem of calculating integrals that take the general form $\int_{R} P(\sigma)d\sigma$ where $P(\sigma)$ is a probability density over the space of mixed quantum states, ...
5
votes
5answers
7k views

Would one actually find their doppleganger in a “Googolplex Universe”?

Related: Infinite universe - Jumping to pointless conclusions I've recently become a fan of Numberphile, and today I happened to watch their video regarding Googol and Googolplex. In the video, ...
10
votes
3answers
57k views

Why does wavelength change as light enters a different medium?

When light waves enter a medium of higher refractive index than the previous, why is it that: Its wavelength decreases? The frequency of it has to stay the same?
15
votes
1answer
222 views

Impact location that created the moon

I was reading an article today about the 1000th orbit of the Lunar Reconnaissance Orbiter, and as many of you know NASA created an animation that simulates the history of the moon. It is speculated ...
3
votes
3answers
164 views

Can a light beam be used as a wire for telephony?

I've heard that Edison (maybe) invented a way to talk over a light beam. Is this true and how do you modulate the light beam?
9
votes
3answers
10k views

What is exactly the density of a black hole and how can it be calculated?

How do scientists calculate that density? What data do they have to calculate that?
4
votes
3answers
615 views

Can we see a spaceship falling into a black hole and entering the event horizon?

Or it pauses in time because the spaceship reaches the speed of light, c?
3
votes
4answers
3k views

Why does change in speed of a wave make it refract?

When a light wave enters a medium with a higher refractive index (e.g. from air to standard glass) and its speed decreases, why does that make it refract/bend? I understand that wavelength decreases ...
2
votes
1answer
2k views

Feynman Path Integral Formula in Brian Cox' “A Night with the Stars” Lecture

The Youtube link keeps breaking, so here is a search on Youtube for Brian Cox' A Night with the Stars lecture. Pause the video on 40.32minutes. What you see he said is called Feynman's Path Integral. ...
4
votes
1answer
1k views

General procedure for Clebsch-Gordan expansions

I'm wondering if the Clebsch-Gordan series generalize to any orthonormal set of basis functions? If so, how would one go about deriving an expression for an arbitrary set of basis functions (perhaps ...
7
votes
2answers
4k views

How can an an ant lift 50 times its own weight and pull 30 times its weight?

According to many sites like this one, an ant can apparently lift 50 times its own weight and pull 30 times its weight. Is it true? Can it be proved using physics? Though most sites agree that an ...
12
votes
7answers
4k views

Does it take significantly more fuel to fly a heavier airplane?

I was reading in the papers how some-airline-or-the-other increased their prices for extra luggage, citing increased fuel costs. Now I'm a bit skeptical. Using the (wrong) Bernoulli-effect ...
5
votes
1answer
661 views

The nature of time, according to quantum field theory

I will try my best to ask the question that best fits something I have been pondering on for a few days. Are virtual particles really constantly popping in and out of existence? Or are they ...
11
votes
1answer
716 views

Falling into Saturn or Jupiter, would we pass through it until we hit the nucleus?

If we fall into Saturn or Jupiter, would we pass through it until we hit the nucleus? Or would we hit the surface and stop there?
1
vote
2answers
928 views

Boundary conditions for static electric field

Consider a surface that carries surface charge density. In electrostatics, boundary conditions are studied by showing that there is a discontinuity in the normal component of the electric field across ...
4
votes
4answers
5k views

Why the shape of rainbow is semicircular after rain why not the whole atmosphere is colorful?

I have a very simple question. Everyone must have seen the rainbow after rain. According to the theory the rainbow is created due to the passing of sunlight from small drops of water in the ...
5
votes
3answers
2k views

Can the technology behind Particle accelerators can be used for space propulsion?

As I understand, the kinetic energy of the proton beam in a hadron collider is quite large. Can you build a space propulsion system that is based on accelerating a proton bean to relativistic speeds ...
4
votes
2answers
962 views

At what distance could you see andromeda with the naked eye?

We've all seen the telescope photographs of andromeda galaxy: I'm wondering if it were possible to travel close enough to the andromeda galaxy could you achieve a same perspective with the naked ...
11
votes
2answers
758 views

Equivalence of definitions of ADM Mass

ADM Mass is a useful measure of a system. It is often defined (Wald 293) $$M_{ADM}=\frac{1}{16\pi} \lim_{r \to \infty} \oint_{s_r} (h_{\mu\nu,\mu}-h_{\mu\mu,\nu})N^{\nu} dA$$ Where $s_r$ is two ...
4
votes
4answers
325 views

How do I go from exponents to a formula?

This is a continuation of this question. http://ocw.mit.edu/courses/physics/8-01-physics-i-classical-mechanics-fall-1999/video-lectures/lecture-1/ skip this lecture to around 25:50. After doing ...
2
votes
1answer
666 views

What is the pressure drop in a venturi with a compressible fluid?

I would like to know if there is an equation to predict the pressure drop in a venturi device using a compressible fluid as the working medium. In particular, I'd like to use this equation to predict ...
3
votes
1answer
415 views

Current formula and form factor

I am currently struggling with the formula for an exact current in QFT, a fermion with an upcoming momentum $p$ and an outgoing momentum $p'$. My problem is to show whether or not a term of the ...
2
votes
0answers
231 views

Centrifugal Compressor Flow Rate

For a centrifugal compressor, as found in most turbochargers on internal combustion engines, is there a noticeable change in flow rate versus a naturally aspirated flow rate? In other words, does the ...
3
votes
2answers
141 views

How Safe Are Heat Ray Guns?

Could a little meddling with the frequencies of the Heat Ray Gun beam result in frying crowds rather than dispersing them?
2
votes
1answer
198 views

How To Stop A Heat Ray Gun?

What material would be best suited to create a shield to protect from the new heat ray gun?
3
votes
1answer
366 views

Unknown isotope

Problem description: The most common isotope of a single nucleus stripped of its electrons is accelerated through a potential difference of 1225V and fired horizontally into a B-field directed ...
3
votes
2answers
117 views

Figuring out which moons of Jupiter I saw through my telescope

Three days ago (Sunday 11st March) in London using my new telescope I was able to see Jupiter and three of its moons. It was very clear and easy to spot. How can I determine the names of the moons I ...
1
vote
1answer
540 views

Common Variables in Quantum Mechanics

I am an eighth grader (please remember this!!!) in need of some guidance in my school project on Quantum Mechanics, Theory, and Logic. I am attempting the create a graph of the Schrödinger Equation ...

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