0
votes
2answers
361 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 ?
-2
votes
1answer
99 views

Didactics question (“teams and times”) [closed]

In sports it is commonplace to distinguish a "team" (as characterized by the players who took part in a match, playing together against another team), from the "score" (such as the final score of ...
3
votes
1answer
124 views

Could tidal effects make matter hot enough for nuclear fusion?

There was a recent question about cosmological firewalls. Putting aside questions of entanglement and information and looking at the problem from a pure mechanical viewpoint, we know that although ...
0
votes
3answers
227 views

Accelerating expansion of the universe and cyclic model

So I've heard that recent observations indicated that the rate of expansion of the universe is accelerating. Does this indicate that the universe can NOT be cyclical, with an infinite series of big ...
2
votes
2answers
179 views

How can we claim something violates some physical law, when so many physical laws have been postulated?

For example, Einstein postulated that the speed of light, c, is constant in all inertial frames of reference. Bohr postulated that electrons go around the atom in ...
2
votes
2answers
467 views

Can anyone analyze this perpetual machine that a Norwegian built?

Take a look at this video: http://www.youtube.com/watch?v=tlx2PgESXhs It shows a machine that a Norwegian artist built. It seemingly keeps going forever. They filmed it over 3 days and it kept going ...
2
votes
1answer
329 views

Killing vectors for SO(3) (rotational) symmetry

I am reading a paper$^1$ by Manton and Gibbons on the dynamics of BPS monopoles. In this, they write the Atiyah-Hitchin metric for a two-monopole system. The first part is for the one monopole moduli ...
1
vote
1answer
684 views

ratio between work and heat [closed]

I am really stuck on a problem in my textbook: Water is heated in an open pan where the air pressure is one atmosphere. The water remains a liquid, which expands by a small amount as it is heated. ...
2
votes
1answer
93 views

Explanation for self-rupture glass is needed

I witnessed a phenomenon that I couldn't conclude its cause. Please bear with me for the length of the recall, for I merely want to include any details that might help us to investigate. I had a ...
3
votes
2answers
3k views

Walter Lewin Lectures in HD [closed]

I like the lectures by Walter Lewin 8.0x. However the quality of the videos is pretty bad. Is there any way (DVD, web,...) to get the lecture videos in a good quality, best in HD?
0
votes
1answer
187 views

what to use for mass in a 2D FEM simulation

I am trying to find the energy of a wave travelling through a solid material in a 2D Finite Element Method (FEM) - Simulation. As a general approach I would try to use $E_{kin}=\frac{1}{2}mv^2$ at ...
11
votes
4answers
2k views

What happens when we cut objects?

What is the role of the molecular bonds in the process of cutting something? What is the role of the Pauli exclusion principle, responsible for the "hardness" of matter? Moreover, is all the energy ...
3
votes
1answer
1k views

Conservation Laws and Symmetries

Usually, in Quantum Mechanics, an observable is an operator on the space of the possible quantum states (labelled as $|\psi\rangle$). If this quantity is conserved, in the meaning that the associated ...
1
vote
4answers
514 views

Matrix mechanics for those with wave mechanics background

Just curious: Is there any book or resource that teaches matrix mechanics (quantum mechanics) only without wave mechanics stuff - meaning that the book assumes wave mechanics background.
-6
votes
2answers
487 views

Cramer's rule, Origin of Quarks Fractional electric charge? [closed]

In linear algebra, Cramer's rule is an explicit formula for the solution of a system of linear equations with as many equations as unknowns. 2u+1d=1 1u+2d=0 $$a_1d+b_1u=c_1$$ $$a_2d+b_2u=c_2$$ ...
-2
votes
1answer
469 views

Pion Decay and Fractional electric Charge disappeared, why?

Since the charged pions decay into two particles, a muon and a muon neutrino Fractional electric Charge disappeared, why? The decay proceeds by the weak interaction $W^{+}$ and can be visualized in ...
2
votes
1answer
302 views

How 'Faster Than Light' Neutrino Was Product of Loose Cable at CERN?

A "faster than light" neutrino discovery was actually the result of a loose cable. A fiber-optic cable in a GPS receiver at the European Center for Particle Physics ( CERN) near Geneva Can someone ...
10
votes
7answers
2k views

What are cosmological “firewalls”?

Reading the funny title of this talk, Black Holes and Firewalls, just made me LOL because I have no idea what it is about but a lively imagination :-P (Sorry Raphael Bousso but the title is just too ...
0
votes
3answers
255 views

Interaction between a Pair of Particles

We consider a particle, A receiving energy from a second one,particle B in a one dimensional collision. $$E^2=p^2+m_0^2$$ $$EdE=pdp$$ For particle A: $$E_AdE_A=p_Adp_A{\;\;\;\;\;\;}(1)$$ For ...
-8
votes
2answers
1k views

Could the fractional model of Quarks electric charge turn out to be false? [closed]

The delta baryons (also called delta resonances) are a family of subatomic hadron particles which have the symbols $\Delta^{++}$, $\Delta^{+}$, $\Delta^{0}$, and $\Delta^{−}$ and electric charges +2, ...
9
votes
2answers
1k views

Deriving the action and the Lagrangian for a free point particle in Special Relativity

My question relates to Landau & Lifshitz, Classical Theory of Field, Chapter 2: Relativistic Mechanics, Paragraph 8: The principle of least action. As stated there, to determine the action ...
0
votes
0answers
352 views

Connection between first and second quantization

This is my question: In a book on many body quantum theory I came across equality between antisymmetrized many-particle state vector which, as you know, includes sum over permutations of product ...
3
votes
3answers
5k views

Will two magnets lose magnetism if they stick to each other for infinitely long time?

Here we have two magnets and they are sticking to each other. What I've learned that could possibly explain it is one magnet holds positive charge and the other one holds negative. But when the ...
0
votes
3answers
604 views

Is there a way to save electricity from lightning? [duplicate]

Possible Duplicate: Can the lightning be captured and used as power source? Each lightning contains several kilo volts of electricity. Saving them could be a boon to soaring need of it. Is ...
5
votes
1answer
753 views

simple explanation of chiral anomaly?

Can somebody provide a fairly brief explanation of what the chiral anomaly is? I have been unable to find a concise reference for this. I know QFT at the P&S level so don't be afraid to use math.
1
vote
2answers
306 views

Pulsed Spherical Wave

Can somebody help show me how a pulsed spherical wave has a wavefunction of the form U(r,t) = (1/r)a(t-r/c), where a(t) is an arbitrary function, r is the radius of the spherical wave, t is time, and ...
5
votes
2answers
366 views

do Higgs Bosons happen in nature all the time? Rarely? Or do they only happen when the Higgs field is excited in a particle accelerator?

I'm trying to reconcile an apparent contradiction between explanations given by Dr. Cox in 2009 and 2012, and those given by a panel of Berkeley professors. I'm not a physicist, and so I realize this ...
6
votes
1answer
1k views

What is the essence of BCFW recursion techniques?

I have recently briefly read about new methods as the Britto-Cachazo-Feng-Witten (BCFW) on-shell recursion method. Can anybody please tell me about the essence of it? What does it mean for the ...
3
votes
2answers
715 views

Centrifugal Force and Polar Coordinates

In Classical Mechanics, both Goldstein and Taylor (authors of different books with the same title) talk about the centrifugal force term when solving the Euler-Lagrange equation for the two body ...
2
votes
0answers
125 views

Reaching the speed of light, rockets [duplicate]

Possible Duplicate: Double light speed Someting almost faster than light traveling on something else almost faster than light Well I've been wondering quite a long time about this ...
1
vote
2answers
131 views

Mechanics Energy (Calculus)

A particle moves with force $$F(x) = -kx +\frac{kx^3}{A^2}$$ Where k and A are positive constants. if $KE_o$ at x = 0 is $T_0$ what is the total energy of the system? $$ \Delta\ KE(x) + \Delta\ ...
0
votes
2answers
611 views

How to correctly solve density tolerance

I want to know if my solution to a textbook problem has any major problems with it. Here is the problem: Ethanol has a given density of 0.789 g/mL at 20 degrees Celsius and isopropanol has a given ...
3
votes
1answer
432 views

Total momentum of the Universe

What is the total momentum of the whole Universe in reference to the point in space where the Big Bang took place? According to my reasoning (and a bit elementary knowledge) it should be exactly ...
1
vote
3answers
3k views

If the earth would stop spinning, what would happen?

What would happen if the earth would stop spinning? How much heavier would we be? I mean absolutely stop spinning. How much does the centrifugal force affect us? If you give technical answers (please ...
0
votes
1answer
480 views

Does the Earth's revolution around the Sun affect radioactive decay?

Premises: The radioactivity is either hastened or slowed inside a fast moving aircraft. Speed of fastest aircraft: 3,529.6 km/h. The earth's revolution is: 107278.87 km/h. The earth's ...
2
votes
2answers
144 views

Stroboscope-and-telegraph problem

Narrative: Consider, in a suitably flat region, two straight lines which don't necessarily intersect. Let vector $\mathbf{x}$ point along one line, and vector $\mathbf{y}$ point along the other. Let ...
5
votes
0answers
161 views

Implications of Unruh-inertia to theories of gravity

If it turns out to be true that the galaxy rotation curves can be explained away by Unruh modes that become greater than the Hubble scale at accelerations around $10^{-10} m/s^2$ as proposed in here, ...
1
vote
1answer
114 views

Why is my speed imaginary?

A particle is released from a dense atmosphere free planet of radius r at a distance R (R >> r ). find the speed on impact. $$F = \frac{GmM}{(r + R)^2} = m \frac{dv}{dt} = mv\frac{dv}{dR}$$ ...
2
votes
1answer
343 views

Classical scalar field correlation function

How should I interpret the left-hand side of this expression $$ \langle \phi(k)\phi(-k) \rangle ~=~ \frac{\mathrm{i}}{k^2 -m^2},$$ which appears on pg. 3 of Matt Strassler's TASI 2001 notes: ...
4
votes
1answer
281 views

Quantum $n$-body problem

Is the quantum $n$-body problem as difficult as the classical $n$-body problem? Or quantum mechanics allows to get a simpler exact solution? Suppose there are 3 particles with uniform potential ...
1
vote
1answer
121 views

Is more energy required to magnetize based on its distance to other objects?

I have had this question since I was in college physics, but never could figure out how to express it. Well, now I think I have it. Let's imagine two scenarios A and B. Both scenarios start with two ...
9
votes
1answer
183 views

Why are topological solitons present in some phases for lattice models?

Over a spatial continuum, it is easy to see why some topological solitons like vortices and monopoles have to be stable. For similar reasons, Skyrmions also have to be stable, with a conserved ...
2
votes
1answer
1k views

Will adding cold water to a hot iron pan harm it? Why/why not?

Adding cold water to a aluminum pan can be harmful. Is this same with iron pan too? How can it be explained?
1
vote
1answer
829 views

What makes water-droplet/dew stick to spider's web and what keeps them there?

How water-droplet/dew stick to spider's web? What keeps them there?
2
votes
1answer
465 views

Einstein's Explanation for gravity vs. Newtonian

I was trying to understand the Einstein's explanation for gravity (gravitational force), and while I am able to understand why two moving masses will be attracted, due to the curving of the space, I ...
1
vote
2answers
7k views

Do magnets work in outer space?

Is there any media where magnet lose its property?
5
votes
5answers
2k views

Show the Lorentz Transformation Matrices Have an Inverse

Assume the Lorentz transformations obey the relationship $$g_{uv}\Lambda^u_{p}\Lambda^v_\sigma = g_{p\sigma},$$ where $g_{uv}$ is the metric tensor of special relativity. How can one show, under that ...
1
vote
1answer
444 views

Matrix element in quantum mechanics

This is about a matrix element of a second quantized operator. Consider the operator $$ U=\sum_{\alpha\beta}U_{\alpha\beta}c^{+}_{\alpha}c_{\beta} $$ Something strange emerges if we calculate again ...
12
votes
6answers
1k views

What is the easiest way to stop a star?

On long enough cosmological time scales, hydrogen and helium nucleii will become scarce in the Universe. It seems to me that any advanced civilisations that might exist in that epoch would have the ...
7
votes
4answers
366 views

Are probabilities really tangible physical real numbers?

Probabilities are usually considered to be a real number between 0 and 1. A real number has an infinite decimal expansion. Are probabilities really real numbers? Is the infinite decimal expansion ...

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