0
votes
1answer
9 views
how to move an object to another moving object
Ok, let's think in Cartesian coordinates. Say you have an object moving increasing on the y axis, lets say 10 points per second to keep it simple. Then you want to have another object on x axis move ...
0
votes
0answers
8 views
Clarification of Landauer approach
I am trying to understand the Landauer approach. Consider the setup: (left contact)-(conductor)-(right contact). For simplicity, the conductor is a 1d wire (the transverse part is not relevant for ...
0
votes
0answers
7 views
What is the optimal weight ratio of a two-stage rocket?
I've been researching this for some time now and I got stuck.
The best resource I've found is this book. The "optimising a multistage rocket" part talks about a three stage rocket but it seems ...
0
votes
2answers
24 views
What force is responsible of anti-gravity?
I've seen several video which claims that is anti-gravity. I am sure at least one of them, use a kind of electricity to lift an object! (triangle lifter), I would guess electricity lift that object by ...
3
votes
1answer
30 views
The quickest 6-3 play in baseball: to bounce or not to bounce?
What's the quickest way the get the ball (say from shortstop) into the first-baseman's glove, given some fixed initial (throwing) speed? Directly or with one bounce?
I'm fairly sure that the answer ...
0
votes
0answers
14 views
Limits on stable charged particles
Are there generic model-independent limits on massive stable charged particles (say 10-500GeV)? I mean SU(2)/color singlets with just a hypercharge.
For example the LEP search (CERN-EP/99-075) was ...
1
vote
0answers
24 views
What happens when a ball stops bouncing?
If I were to drop a bouncy ball onto a surface, each successive bounce will be lower in height as energy is dissipated. Eventually, however, the ball will cease to bounce and will remain in contact ...
0
votes
0answers
9 views
What gives atoms their chemical properties [migrated]
What makes Hydrogen flammable? What makes Oxygen support burning? What makes water behave unlike either components? What gives an element its chemical properties and what makes the compounds behave ...
0
votes
0answers
6 views
In structural vibration, does energy get transferred between different types of waves in the same body?
I'm beginning to study structural vibration (and statistical energy analysis). While writing out all coupling loss factors (usually denoted by eta) for parts of a built-up structure, this question ...
-2
votes
0answers
30 views
electrostatic repulsion that is troubling me
Consider a homogeneous ring of radius $R$ made of a thin wire of cross section $A (R^2\gg A)$. A Charge $Q_1=10\mu \mathrm{C}$, uniformly distributed over the ring, broke it apart due to electrostatic ...
0
votes
0answers
28 views
What really are exotic supersymmetric black holes?
I have just read (in the black holes chapter 14 on p244 of this book) that when one adds an (electric?) charge $Q$ to a static black hole, one can arrive at an exotic supersymmetric black hole.
This ...
2
votes
1answer
40 views
Why we call the ground state of Kitaev model a Spin Liquid?
Now we always talk about the so-called Kitaev spin liquid. One important property of spin liquid is global spin rotation symmetry. Let $\Psi$ represents a spin ground state, if $\Psi$ has global spin ...
0
votes
1answer
17 views
Fitting a circuit scheme to a simpler model
I have to simulate the electric field within a gas filled discharge gap generated by a radio frequency voltage generator. The circuit, provided to me by the experimenters somewhat far away, is given ...
1
vote
1answer
28 views
Type I' String theory as M-theory compactified on a line segment?
I was considering the S-dual of the Type I' String theory (the solitonic Type I string theory).
That is the same as the S-dual of the T-Dual of Type I String theory. Then, that means both length ...
-7
votes
0answers
51 views
Newton's law paradox [closed]
With reference to these 3 questions . Kindly read all the questions,answers and comments in these 3 links . I wish to get a more detailed and canonical answer that addresses every issue discussed .
...
3
votes
1answer
54 views
Huge buildings affect earth's rotation?
Does constructing huge buildings affect the rotation of the earth, similar to skater whose angular rotation increases when her arms are closed comparatively than open.
2
votes
1answer
51 views
If time stops at the speed of light is a photon 'everywhere' at once? [duplicate]
I am not a physicist so excuse my question if it's paticularly stupid. As a particle gets closer to the speed of light time slows down as for that particle as compared to a reference from the ...
0
votes
0answers
35 views
Why does heat solidify cake batter? [migrated]
Increased vibration causes the atoms in an object to spread out farther away. Thus, with added heat, and object goes form a solid to a liquid to a gas (and then to plasma, with enough heat). Why is it ...
2
votes
1answer
28 views
Diagonalizing/eigenvalues of the infinite dimensional matrix of N harmonic oscillators on a ring
I have trying to show that the continuum limit of N quantum harmonic oscillators gives rise the the klein-gordon field. However, instead of a usual finite string, I want to do it on a ring. Hence, my ...
-2
votes
1answer
47 views
Question on friction [closed]
Please look at the figure carefully. The question is written, and one has to match the two columns 1 and 2 given under "choices and explanation". Please tell me if I am really wrong, i.e. would you ...
3
votes
2answers
335 views
Why is a degree Celsius exactly the same as a Kelvin?
How on earth is it possible that the difference between two temperatures in Celsius and Kelvin is exactly the same. Given the historical definition of Celsius, I find it hard to believe that this is ...
1
vote
1answer
39 views
How (why!?) does one introduce an UV cut-off in dimensional regularization?
This question is in reference to the confusing equation 3.7 (page 14) of this paper.
One sees the 1-loop answers in their theory as given in their A.7 and A.8 on page 20. Each of the terms is a ...
1
vote
2answers
83 views
Was TP Singh right to say that a theory of quantum gravity necessitates the Copenhagen Interpretation?
http://iopscience.iop.org/1742-6596/174/1/012024
In the above link we see TP Singh arguing that only Copenhagen will work for a theory of quantum gravity.
Some of his key points are "quantum theory ...
3
votes
0answers
38 views
Quantization as a functor
Can anyone give an mathematical elaboration of the following statement:
Quantization is a functor carrying the category of Hilbert space and linear maps to that of Symplectic manifolds satisfying ...
3
votes
2answers
33 views
How to draw a ray diagram from focal length, object and image heights?
Q. An object of height 8 cm is placed in front of a lens. It's inverted image of height 4.8 cm is formed on the screen. If the focal length of the lens is 12 cm then by drawing at scale calculate the ...
4
votes
1answer
54 views
Quantum master equation in the Batalin-Vilkovisky formalism
I am reading the Section 15.9 of Weinberg's book "The Quantum Theory of Fields, vol. 2". Under a shift $\delta\Psi[\chi]$ in $\Psi[\chi]$, we have
$$
\begin{split}
\delta ...
1
vote
1answer
40 views
Why do single particle states furnish a rep. of the inhomogeneous Lorentz group?
Following up on this question: Weinberg says
In general, it may be possible by using suitable linear combinations of the $\psi_{p,\sigma}$ to choose the $\sigma$ labels in such a way that ...
0
votes
0answers
34 views
Physical Interpretation of Lorentz-transformed Single Particle states being linear
As in this question, let $\psi_{p,\sigma}$ be a single-particle 4-momentum eigenstate, with $\sigma$ being a discrete label of other degrees of freedom.
Weinberg discusses the effect of a homogenous ...
1
vote
0answers
20 views
Why are non-momentum DoFs of single-particle states discretely labeled?
Following the treatment of Weinberg, chapter 2, we consider $\psi_{p,\sigma}$ as single-particle eigenstates of the 4-momentum. Weinberg says that $\sigma$ labels all other degrees of freedom and we ...
4
votes
0answers
29 views
What is energy in $z \neq 1 $ theories?
In a critical theory with dynamical critical exponent $z \neq 1 $, which amongst frequency, $\omega$, and dispersion, $E(\vec{k})$, may be referred to as ''energy''? I'm confused about this since in ...
0
votes
1answer
23 views
Is there a term for the argument of the sine function outside of geometry?
Are there similar terms in other areas for the idea the "angle" conveys in geometry? I find that functions for abstract things such as pressure, electrical currents (nothing geometric there) on AC ...
0
votes
1answer
42 views
How far to the 'edge' of the galaxy?
Wikipedia lists the average thickness of the milky-way to be about 1,000 LY - but where (roughly) within that is the sun currently? In asking this, I'm fully aware that there's no well-defined edge - ...
2
votes
1answer
37 views
Why are the magnetic moment and the angular moment related?
I've always read everywhere that they are related but found nowhere a satisfactory explanation of the cause
4
votes
0answers
61 views
What goes wrong when one tries to quantize a scalar field with Fermi statistics?
At the end of section 9 on page 49 of Dirac's 1966 "Lectures on Quantum Field Theory" he says that if we quantize a real scalar field according to Fermi statistics, the quantum Hamiltonian is no ...
0
votes
1answer
23 views
Comparison search with repeated elements
I am study the Grover algorithm. I want know what's the computational complexity of the best classical algorithm that finds an element in set $M$ with probability $p\geq 1/2$?. I know in the quantum ...
5
votes
2answers
71 views
Conceptually, what is negative work?
I'm having some trouble understanding the concept of negative work. For example, my book says that if I lower a box to the ground, the box does positive work on my hands and my hands do negative work ...
9
votes
3answers
94 views
Why do prisms work (why is refraction frequency dependent)?
It is well known that a prism can "split light" by separating different frequencies of light:
Many sources state that the reason this happens is that the index of refraction is different for ...
3
votes
1answer
39 views
Can convection cells evolve in stably stratified fluid?
Assume stably stratified fluid but not in equilibrium, e.g. with non-constant temperature gradient for example. Can convection cells be present? Typical example of convection cells is Rayleigh–Bénard ...
1
vote
1answer
25 views
How to calculate air resistance of penny dropped from Empire State Building?
If a penny is dropped from the Empire State Building, then its speed, without taking air resistance into consideration, is
$\sqrt{\left(32\frac{\textrm{ft}}{\textrm{s}^2}\right)(1454\textrm{ ...
3
votes
1answer
46 views
Does a lightning rod prevent lightning strikes?
I was always under the impression that a Lightning rod worked to protect a building by being the tallest part of the building and having a low path of resistance to the ground, thus being a good ...
4
votes
1answer
67 views
Explicit form of $\gamma^\mu \partial_\mu$ in the Dirac equation
I'm in an introductory particle physics class, and in performing manipulations on the Dirac equation, my instructor expands the $\gamma^\mu \partial_\mu$ term as:
$$\gamma^\mu \partial_\mu = \gamma^0 ...
0
votes
0answers
14 views
Problem in angle measurement [migrated]
From the above picture we can prove easily $ CF = XF$ because CFX is a isosceles triangle. Now if we move the point X more near near P, it will give the same results(I mean we will get again $ CF = ...
1
vote
1answer
41 views
Anti-particle problem for Dirac sea
According to the Dirac hole theory we know that Dirac sea is completely filled with negative energy, called vacuum. We will need $2mc^2$ or greater to get electron and a positron by incident photon.
...
-4
votes
0answers
26 views
What formula is used to determine weight distribution using two people to lift 100 lbs over their head? [closed]
Trying to determine actual weight and force required to perform a two man deadlift of an container weighing 100lbs
3
votes
3answers
155 views
Meaning of inner product $\langle \vec{r} | \psi(t)\rangle $
I have come across the equation which comes out of the nothing in Zettili's book Quantum mechanics concepts and applications p. 167:
$$\psi(\vec{r},t) ~=~ \langle \vec{r} \,|\, \psi(t) \rangle.$$
...
5
votes
1answer
95 views
Unitary quantum field theory
What do physicists mean when they refer to a quantum field theory being unitary? Does this mean that all the symmetry groups of the theory act via unitary representations? I would appreciate if one ...
0
votes
0answers
16 views
Spring constant problem [closed]
Say, a spring AB is hung from the ceiling, a block of mass m is attached to B. Another spring CD making angle A with the vertical is attached to side B. What will happen next? Can the system stay in ...
0
votes
1answer
50 views
What is the wave length of the entire universe?
In quantum physics, particles are also waves. Larger particles have shorter wave lengths, and macroscopic objects have extremely short wave lengths so that the wave aspect can be ignored, and ...
3
votes
4answers
73 views
How can particles travel in a straight line?
Particles can be set off in a certain direction by giving them momentum. Momentum is a vector, so the particle head off in a specific direction. But the wave function of the particle allows it to ...
6
votes
3answers
141 views
Origin of Ladder Operator methods
Ladder operators are found in various contexts (such as calculating the spectra of the harmonic oscillator and angular momentum) in almost all introductory Quantum Mechanics textbooks. And every book ...
