4
votes
2answers
11k views

Equations for an object moving linearly but with air resistance taken into account?

I know (from Kinematics) that for an object moving linearly with an acceleration and without air resistance the following equations can be used to determine v(velocity) or x(position of the object) at ...
4
votes
2answers
452 views

2D Ghost CFT and two-point functions

For some reason I am suddenly confused over something which should be quit elementary. In two-dimensional CFT's the two-point functions of quasi-primary fields are fixed by global $SL(2,\mathbb ...
4
votes
1answer
547 views

Interpretation of field operator

Consider a real scalar field operator $\varphi$. It can be written in terms of creation and anihilation operators as $$\varphi(\textbf{x})=\int \tilde{dk}[ ...
1
vote
1answer
288 views

Importance of phase in probability amplitude in QFT

I have started teaching myself QFT from the textbook by A. Zee. From reading that book, my idea of a path integral in field theory is the probability amplitude to go from a given field configuration ...
0
votes
2answers
8k views

Fundamental frequency , wavelength and the length?

What is the concept behind when it is said that for the first fundamental f=c/λ , λ should be equal to 2L . I have read the page http://en.wikipedia.org/wiki/Fundamental_frequency but I am still ...
0
votes
1answer
2k views

Salt and boiling speed

When we add a compound (salt) to a solvent, the boiling points rises. But, what could we say about the speed the solvent reaches the boiling point? It's better to add salt before or after boiling ...
3
votes
1answer
132 views

Quantum computers and algorithm performance

I have a question. Gradually quantum computers will emerge someday. So, nowadays making algorithm efficient is important; I mean, making it optimal to run as fast as possible. But once quantum PC ...
1
vote
1answer
505 views

Hamiltonian Flow Map

I'm reading this article and am struggling with some of the terminology. What is the flow map for a Hamiltonian system? I'm looking for a rigorous definition really! Many thanks in advance.
2
votes
1answer
283 views

Why is physical space equivalent to $\mathbb{R}^3$?

Why is physical space equivalent to $\mathbb{R}^3$, as opposed to e.g. $\mathbb{Q}^3$? I am trying to understand what would be the logical reasons behind our assumption that our physical space is ...
3
votes
3answers
2k views

Can we have discontinuous wavefunctions in the Infinite Square well?

The energy eigenstates of the infinite square well problem look like the Fourier basis of L2 on the interval of the well. So then we should be able to for example make square waves that are an ...
2
votes
2answers
167 views

knowledge of an internal observer

I would like to discuss the consequences of the concept of an internal observer in quantum theory. If we assume that we have a universe that evolves unitarily at a global scale and an observer is ...
1
vote
1answer
262 views

Lorentz transformations for sine wave in random direction

Hello i have been struggling to derive Lorentz transformations for a sine wave, which is traveling at random direction. I started by prooving that phase $\phi$ is invariant for relativity and that ...
1
vote
0answers
135 views

How far is the horizon, if a 2m tall man watches to the sea?

How far is the horizon, if a $r=2 m$ tall man watches to the sea? I have calculated that it would be even just about 6 km. if R = radius of earth( $6370 \cdot10^3$ m ). By pythagorean theorem we ...
1
vote
1answer
93 views

Linear rising potential from a Gribov propagator

It is common wisdom that a gluon propagator (Gribov-)like $$ G(p^2)=\frac{a+bp^2}{cp^4+dp^2+e} $$ should give rise to a linear rising potential. So far, I have not seen a proof of this and I would ...
3
votes
1answer
933 views

What is the longest distance that can be jumped after swinging from a rope?

In the movie Mission Impossible 3, the main character Ethan Hunt tries to enter a building in Shanghai by swing through the sky, as shown below: The jump consists of 2 sections, the red part, which ...
1
vote
3answers
4k views

When an object moves downward, is its height negative?

The question is: A ball is thrown directly downward with an initial speed of 8.00m/s from a height of 30.0m. After what time interval does it strike the ground. So I went through the problem ...
0
votes
1answer
90 views

Non-conversion of mass & energy?

This article is certainly an interesting alternative perspective, but is it factual or does it contain fallacies? http://www.circlon-theory.com/HTML/EmcFallacies.html Are mass and energy not ...
14
votes
3answers
7k views

Does special relativity make magnetic fields irrelevant?

I've heard that special relativity makes the concept of magnetic fields irrelevant, replacing them with relativistic effects between charges moving in different velocity frames. Is this true? If so, ...
3
votes
2answers
97 views

Can non-photon atomic particles (can/may be) stimulate photonreceptors in our eyes?

I want to ask if the human eye can see only photons particles between ultra violet and infrared wavelengths, can we see other particles (that have a wavelength between ultra violet and infrared) ...
6
votes
1answer
10k views

Optical microscope magnification limits?

Optical microscopes are quoted as having a maximum magnification of 1500x to 2000x - what is this calculated from?
6
votes
0answers
1k views

Nuclear/quantum physics simulation software

Is there any software which is able to simulate D-T interaction for example and get temperature-crosssection curve without referencing to any experimental data? Do we have quantum-level simulation ...
3
votes
2answers
1k views

Complete list of nuclear fusion reactions

Could anyone suggest good source of all fusion reactions and their cross section vs energy graphs, including ones which were ruled out for nuclear fusion reactors (i.e. including endothermic and ...
3
votes
1answer
302 views

scattering singularity

In QFT when one works out the cross section between two colliding electrons one gets a formula which is proportional to $\theta^{-4}$ where $\theta$ is the scattering angle which is due to a nearly ...
21
votes
4answers
4k views

Conformal transformation/ Weyl scaling are they two different things? Confused!

I see that the weyl transformation is $g_{ab} \to \Omega(x)g_{ab}$ under which Ricci scalar is not invariant. I am a bit puzzled when conformal transformation is defined as those coordinate ...
11
votes
2answers
665 views

What's the deepest reason why QCD bound states have integer charge?

What's the deepest reason why QCD bound states have integer electric charge, i.e. equal to an integer times the electron charge? Given that the quarks have the fractional electric charges they do, ...
1
vote
1answer
205 views

What are “cycles of anomaly” and “cycles of longitude”?

In several early (pre-1600) astronomical texts I read about "cycles of anomaly" and "cycles of longitude", but it us unclear to me what these terms mean. They were clearly familiar to authors at the ...
5
votes
1answer
414 views

What shape of track minimizes the time a ball takes between start and stop points of equal height?

I was at my son's high school "open house" and the physics teacher did a demo with two curtain rail tracks and two ball bearings. One track was straight and on a slight slope. The beginning and end ...
0
votes
1answer
440 views

What path would advanced spaceships take to move between planets? [closed]

Right now, space travel is all about carefully moving between orbits. If you want to go from Earth to Mars, you wait until the two planets are correctly aligned, and then place yourself into an ...
3
votes
2answers
1k views

Why water is not superfluid?

My question is in the title. I do not really understand why water is not a superfluid. Maybe I make a mistake but the fact that water is not suprfluid comes from the fact that the elementary ...
4
votes
2answers
1k views

What do you feel when crossing the event horizon?

I have heard the claim over and over that you won't feel anything when crossing the event horizon as the curvature is not very large. But the fundamental fact remains that information cannot pass ...
5
votes
2answers
2k views

Harold White's work on the Alcubierre warp drive

I've read a bit on Harold White's recent work. (A paper on Nasa's site) I haven't been able to find any comments by people claiming to know anything about the physics involved. Is this really serious? ...
1
vote
1answer
123 views

What star processes throw strange matter into space?

My understanding is that strange matter is stable in low pressures or vacuum, but correct me if this is wrong I'm wondering how likely is to find strange matter in empty space. What physical ...
3
votes
3answers
2k views

Does Nantenna (nano antenna) violates 2nd Law of Thermodynamics?

Does Nantenna (nano antenna) violates 2nd Law of Thermodynamics ? Nantennas absorb infrared heat and convert it in direct current. Quote from Wikipedia: He did not discuss whether or not this ...
1
vote
3answers
359 views

Length Contraction And Simultaneity

I wanted to derive length contraction from the Lorentz transformation, but I keep getting stuck on problems with simultaneity in my derivation. At some point, I came across Wikipedia's article on ...
1
vote
2answers
374 views

How did QED diverge from quantum mechanics mathematically?

We have either Heisenberg or Schrodinger picture of quantum mechanics world. So, how did quantum electrodynamics come from mathematical formulations of quantum mechanics? Also, QED seems to have ...
3
votes
2answers
100 views

possible values of quantity in matrix mechanics

Suppose that there is a quantity described by the matrix as the following: $M = \begin{bmatrix} 3 & 0 & -i \\ 0 & 1 & 0 \\ i & 0 &3\end{bmatrix}$ How we determine possible ...
0
votes
2answers
240 views

Task with three metal plates [closed]

There are three parallel metal plates. Two boundary plates are fixed and connected with a galvanic battery, maintained a constant potential difference $\Delta \varphi$. Middle plate was initially in ...
0
votes
1answer
1k views

Capacitance and Light Bulb And Dielectric Slab [closed]

An electric lamp having coil of negligible inductance connected in series with a capacitor and an AC source is glowing with certain brightness. How does the brightness of the lamp change on reducing ...
1
vote
0answers
201 views

Eigen modes in a room

In a rectangular room 10*8*5 how can the eigen modes belonging to octave and third octave bands centered at 50Hz be found ? I have the formula to calculate the number of modes but don't have the idea ...
1
vote
2answers
854 views

Quark compositions in $\pi^+$ to $\pi^0$ pion decay

Pions can undergo a rare beta-like decay into leptons: Pion beta decay (with probability of about $10^{−8}$) into a neutral pion plus an electron and electron antineutrino (or for positive ...
2
votes
1answer
238 views

Is Fractional quantum Hall effect proof that leptons are composite particles?

The fractional quantum Hall effect (FQHE) is a physical phenomenon in which the Hall conductance of 2D electrons shows precisely quantised plateaus at fractional values. Should this be considered ...
4
votes
2answers
320 views

Entanglement measure to classify topological ordered states

I know long-range entanglement is the essence of nontrivial topological ordered states. (Trivial refers to short range entangled and nontrivial refers to long range.) So, entanglement measure at large ...
3
votes
5answers
3k views

Is Heisenberg's matrix mechanics or Schrödinger's wave mechanics more preferred?

Which quantum mechanics formulation is popular: Schrödinger's wave mechanics or Heisenberg's matrix mechanics? I find this extremely confusing: Some post-quantum mechanics textbooks seem to prefer ...
3
votes
1answer
857 views

Different colors in LED/LCD display when viewed from different angle?

I want to know why different colours appear when viewed with a different angle. Can anyone tell me why?
1
vote
3answers
503 views

Is it possible to hear the past?

From this Stack Exchange Physics Post, I am certain that it is possible to view the past. But then this interesting question came to me. Is it possible to hear the past? Ok, you might say, "Well, ...
2
votes
1answer
4k views

Magnetic field lines can be entirely confined within the core of a toroid, but not within a straight solenoid. Why?

I need a full explantation for this concept. Magnetic field lines can be entirely confined within the core of a toroid, but not within a straight solenoid.
1
vote
1answer
137 views

Difference between using displacement and current configuration as unknown?

We could use either the current configuration $x$ or the displacement $u$ as unknown while solving for the deformation, for example, of a solid object. I want to know what's the difference between ...
7
votes
6answers
1k views

Maxim Raykin's “solution to the measurement problem” using infinitely many derivatives

Recently I was made aware of the following arXiv preprint by Maxim Raykin: Analytical Quantum Dynamics in Infinite Phase Space. As far as I understand it, Raykin's idea is to reinterpret quantum ...
1
vote
0answers
176 views

Folded and/or compacted dimensions in M-theory?

I've on many occasions that there are various numbers of 'extra' dimensions above the 4th. However, I've heard that they are 'compacted' or 'folded' tightly and unimaginably small. Now, as I ...
0
votes
2answers
458 views

When differential equation like Schrodinger is separable in some coordinate system?

When differential equation like Schrodinger is separable in some coordinate system? What needs to satisfy the potential ?

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