2
votes
0answers
136 views

Warped AdS${}_3$ and symmetry breaking

In this article it is explained how on can (in suitable coordinate basis) get a so called warped AdS${}_3$ black hole, by introducing a warping factor. The original metric in 'Euler coordinates' for ...
6
votes
5answers
623 views

Does Gravity / curved space cause rotation?

Does Gravity / curved space cause rotation? Meaning, if a spaceship is heading not directly toward Earth, but slightly off to one side, and when finally being close to the Earth it falls into earth ...
3
votes
1answer
894 views

Example of application of creation/annihilation operators in matrix form

I was wondering how it would sound like the creation/annihilation of particles that we usually do in the context of Dirac formalism, with matrices and vectors. As a reminder we know that: ...
0
votes
1answer
121 views

Why does angle deviation of a satellite not captured my Mars decreases as the Velocity of the satellite increases?

When a satellite is not captured by a planet, it is moving sufficiently fast. so why is it that the angle deviation of the satellite decreases as its initial velocity increases?
-1
votes
1answer
95 views

How can a fly be in the space of a roofless car, get out of the car space and get back in while the car is driving at the speed of 80mph? [closed]

I was driving in a cabriolet car at the speed of 80mph, while a fly flew in and out of the frame of the car. My question is, How can the fly leave the frame and get back in? Is it possible that it ...
-1
votes
1answer
127 views

Why polarization vector $= (0,1,i,0)$?

I know from CED that one has e.g. polarization $$\vec{E}(z,t) = \begin{bmatrix} e_{x} \\ e_{y} \\ 0 \end{bmatrix} \; e^{i(kz - 2 \pi f t)}. $$ Why do Peskin&Schroeder define a polarization ...
3
votes
3answers
116 views

Simple Experimental Laser Characterization Parameters Ideas?

I have 2 months to do a project on characterization of a laser parameter. We have typical optics lab equipment (DFB Lasers, oscilloscopes, random number generator, etc.). I was told to choose a laser ...
2
votes
1answer
352 views

Parity transformation for spinors (pinors) in odd spacetime dimensions

What is the transformation law for spinors (pinors) under parity in an odd number of spacetime dimensions? I know how to derive the transformation properties of spinors (pinors) under parity in an ...
6
votes
3answers
326 views

Propagator of Chern-Simons Abelian gauge theory

I need to compute the "topologically massive photon" propagator. I've started with : $$ \mathcal{L}=-\frac{1}{4}F_{\mu\nu}F^{\mu\nu} + \frac{\mu}{4}\epsilon^{\mu\nu\lambda}A_\mu\partial_\nu ...
0
votes
0answers
36 views

Is there a generic term for orbital groups such as $e_g$ and $t_{2g}$?

I am looking for a generic term for sets of atomic orbitals (viz. spherical harmonics) which are grouped by crystal symmetry. The most familiar examples would be $e_g$ and $t_{2g}$ (in cubic ...
0
votes
2answers
8k views

Why does the windshield of my car freeze even if the outside temperature is above freezing? [duplicate]

Under what conditions does the windshield of a car freeze even if the outside temperature is above freezing? It is not clear whether this is related to the question why bridges freeze with ...
1
vote
0answers
76 views

Does all electrical insulator can be electrostatically charged?

Does all electrical insulator can be electrostatically charged, or insulator with only dielectric property can? Thank you.
0
votes
1answer
30 views

Microscopic origin of optical transmission

When light interacts with matter, it is abosrbed, reflected and transmitted. With repect to the UV-Vis range, electronic abosrptions occur, where if the incident photon mode matches the energy ...
3
votes
0answers
120 views

A question about spontaneous symmetry breaking at macroscopic limit

The question relates to this post. Spontaneous symmetry breaking is somehow a volume effect, that in-principle only happens at infinity large system. Weinberg in the second volume of his QFT used a ...
3
votes
1answer
551 views

What is the universe 'expanding' into? [duplicate]

We say the universe is expanding, and by expanding we mean the distance between objects gets larger over time. We call that "Metric Expansion of the Universe". So far so good. I kind of get the idea ...
1
vote
1answer
88 views

Have the values of constants ever changed before?

Example sub-questions: Was the speed of light always that value? Was the acceleration due to gravity always been 9.8m/s/s? Etc By "change" I mean both actual change in the physical world because ...
5
votes
0answers
206 views

What is the point of path integral for boson and fermion?

I am a beginner to study QFT and confused about path integral for boson or fermion. I have read about the path integral for single particle, and finished some problems. But I cannot understand the ...
0
votes
2answers
96 views

Are Feynman's Hamiltonian computers unitary?

In this paper, Feynman gave the idea of creating a time-independent Hamiltonian from a quantum circuit. Is there anyway to say that these Hamiltonians will always be Hermitian? Moreover, will these ...
1
vote
0answers
32 views

Is something like cosmic refraction possible?

From what I understand, these papers postulate the speed of light is dependent upon the properties of the quantum vacuum. The quantum vacuum as the origin of the speed of light Special theory of ...
6
votes
3answers
1k views

Binary Star system with one star stationary?

Can a Binary Star system be possible where in one star is stationary and the other star revolves around it? (Just like a planet revolving a star. i.e planets in the system and the star revolving ...
3
votes
1answer
195 views

Noether Charge For Scalar Fields Under Lorentz Transformations

The conserved charge associated with the Lorentz transfomation of a scalar field is given by $Q^{\alpha\beta}=\int d^3x\frac{1}{2}(x^\alpha T^{0\beta}-x^\beta T^{0\alpha})$. The quantities $Q^{ij}$ is ...
2
votes
1answer
95 views

Do black holes have a characteristic size?

First off, I know that a black hole can theoretically exist at any size, and I know about the Schwarzschild radius, etc. Snowflakes could also exit at just about any size, and they of course vary ...
13
votes
2answers
658 views

Are Thomas Breuer's subjective decoherence and Scott Aaronson's freebits with Knightian freedom the same things in essence?

In his remarkable works (1,2 and their recent development 3) Thomas Breuer proves by diagonalization the phenomenon that the observer cannot distinguish all phase space states of a system where he is ...
0
votes
0answers
35 views

Does the time for communication between moving objects solely account for each object to perceive the other object's clock to more slowly tick? [duplicate]

In "The Elegant Universe," two individuals, George and Gracie, are noted to be moving relative to one another in space and wearing clocks. They sync their clocks upon passing each other. Each observes ...
0
votes
0answers
142 views

Finding the appropriate source term for 2D Pressure Driven Flow in a Square Channel

I'm trying to solve the equation: $$ \frac{\partial^2 v_z(x,y)}{\partial x^2} + \frac{\partial^2 v_z(x,y)}{\partial y^2} = \frac{\Delta P}{\mu \Delta X} $$ This flow is supposed to be flowing in a ...
1
vote
2answers
256 views

Many world interpretation on test

Is there any experiment conducted to prove Many world interpretation of Quantum mechanics? If it can't be proved why we should take MWI seriously? Recently I read some papers of Max Tegmark who is an ...
0
votes
0answers
161 views

How to implement wedge product and form in quantum mechanics?

For example use p-form for p identical fermion system? The Maxwell equations can be rewritten as a single function using forms plus an intrinsic equation showing the Faraday tensor is a two form. ...
2
votes
1answer
251 views

What arguments are in favour of an atomic structure to space-time?

The atomic theory as first theorised by Democritus has been successfully applied to matter and to energy (quanta). Space-time is still generally seen as a continuum. What arguments are there (if any) ...
1
vote
4answers
220 views

Are there any non-interpretational arguments in favour of Everett's Many-Worlds?

As far as I understand Everett's Many-Worlds Interpretation, he makes the case for a realist theory of QM at the enormous cost of many-worlds. Are there any arguments in favour of Everett's ...
0
votes
0answers
92 views

Modeling with First Order Equations [closed]

A ball with mass 015kg is thrown upward with initial velocity 20m/s from the roof of a building 30m high. There is air resistance of magnitude v^2/1325 directed opposite to the velocity , where the ...
0
votes
0answers
52 views

Mass of dark matter

The Alcubierre warp equation specifies that negative mass is required for said "warp drive" to function properly. Could dark matter provide the negative mass that's required?
0
votes
0answers
47 views

Heat Sink considerations for thermionic generators

I recently read an article describing thermionic generation. I am considering building a TG for a science fair experiment. I was thinking about surrounding my heat source with a spherical emitter and ...
1
vote
1answer
83 views

Convective derivative of oscillating fluid with bulk motion?

I have a fluid $u$, which comprises a zeroth order constant motion $u_0$ as well as a first order oscillatory motion $u_1$. The convective derivative is $$\frac{\partial u}{\partial t} ...
2
votes
1answer
180 views

No valid Feynman diagram for processes

This will likely be easy for anyone experienced in particle physics, but I'm not. I'm asked to explain why it is impossible to construct a valid Feynman diagram using Standard Model vertices for the ...
1
vote
0answers
37 views

CMB radiation and holography

If in principle someone have the exact data of the CMB of our universe and unlimited computability power, to what extent it is possible to determine how the universe should look like? Does it fully ...
3
votes
1answer
236 views

2D Harmonic Oscillator Commutators

So I am given a 2-dimensional harmonic oscillator with $H=H_1+H_2$ where $$H_i=\frac{p_i^2}{2m}+\frac{1}{2}m\omega^2x_i^2$$ Additionally, $$L=x_1p_2-x_2p_1$$ If we define ...
2
votes
0answers
118 views

Are Lifshitz and Berestetskii right in this case?

In the Quantum electrodynamics book (look at the problem) its authors Lifshitz and Berestetskei claim that operator of charge conjugation $\hat {C} = -\alpha_{2}$ in Majorana basis transforms as $\hat ...
3
votes
1answer
98 views

Non-locality and topology

This is a purely speculative question: Has there been any work that describes non-locality/entanglement in QM by using exotic topologies in configuration space? The 'conceptual' picture that I have ...
2
votes
1answer
60 views

Implementing a transformation as $UaU$ and not $UaU^{-1}$?

I know one associates to each symmetry transformation a unitary/antiunitary operater...etc. But equation 3.123 in Peskin and Schroeder (PS) says that parity is implemented as $(\mathbf{p}$ is the ...
3
votes
2answers
304 views

Why do canvas water bags and doors expanded when wet?

I recently asked a question on a canvas water bag and I realized that there was something really interesting that I didn’t understand. When a dry water bag gets filled, it leaks a lot of water; ...
17
votes
2answers
291 views

Branching lemon drop “smoke rings”

This might be hard to ask, but here goes nothing. I recently poured a cup of water into a black coffee cup. There was a light source--not very bright--above the cup. Anyways, I was squeezing a ...
0
votes
2answers
1k views

How do I combine three resistors which are in parallel with each other?

For this circuit (a and b are connected by a battery), Will I be able to find the total resistance of the circuit by adding resistors that are in series and combining resistors that are in ...
1
vote
0answers
2k views

Find initial velocity when given max height of 100m [closed]

A ball is thrown straight up. The height of the ball above the ground in (m) is given by the function: $$h(t)=-5t^2 + vt + c$$ What is the initial velocity if you want the ball to reach a max height ...
9
votes
1answer
232 views

The difference between $\mathcal{N}=2$ short multiplets and BPS states

I have some questions about the construction of $\mathcal{N}=2$ supermultiplets for chiral matter. I know that the supermultiplet should not include spin one states since they are always in the ...
7
votes
3answers
4k views

How does a canvas water bag cool water?

I was reading about this water bottle by Botl that behaves like a canvas water bags to keep water cool. I found out that this idea is an old idea and cars would drive with water bags in front as shown ...
0
votes
2answers
336 views

How to estimate a person's mass from a sensor? [closed]

I'm trying to estimate the person's weight from some available sensors and I have an accelerometer, a gyrometer and a magnetometer. The triaxial accelerometer is fixed in a band in the person's ...
1
vote
0answers
150 views

Bloch states at the zone boundary

How do I show that in 1D the Bloch states at the zone boundary $\left(k=\pm\frac{\pi}{a}\right)$ form standing waves? How is it clear, that there is a high- and a low energy state for a finite ...
3
votes
2answers
1k views

What happens when electron degeneracy pressure is being overcome (right before an object turns into a black hole)?

I was wondering about hydrostatic equilibrium (the balance of radially inward and outward forces) in large (i.e. above the Chandrasekhar limit) stars. It is often said that when the gravitational ...
4
votes
2answers
581 views

Is there a better approximation of drag (other than quadratic drag)?

This is a student inquiry sparked by sheer curiosity. Wikipedia states the drag equation, $F = 1/2v^2pC_dA_c$. (p = mass density of fluid/gas, v = velocity, c_d = drag coefficient, a_c = cross ...
5
votes
0answers
91 views

Why is it difficult to construct the Ramond-Ramond sector in Berkovits' SFT?

I've been trying to get familiar with string field theory (SFT) and I've stumbled upon the statement that the Ramond-Ramond (RR) sector of Nathan's SFT has not been constructed yet. Why is that?

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