# All Questions

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### Graphing measurements with uncertainties

I need to draw a graph of measurements of time for a ball to drop on an inclined plane, with error bars, along with lines of best and worst fit. The problem is that I need to do this on the computer ...
114 views

### ATLAS Higgs Interpretation

I came across this abstract, and I am curious as to what the ATLAS Team has actually discovered: Abstract Motivated by the result of the Higgs boson candidates at LEP with a mass of about ...
367 views

### Quantum mechanics + General relativity =?

I have learned (the basics) of how one can incorporate the principles of special relativity to quantum mechanics to obtain quantum field theory. Can the same be done with GR and QM to obtain a new ...
621 views

### How vacuous is intergalactic space?

You often hear intergalactic space is an example for a very good vacuum. But how vacuos is space between galaxy clusters and inside a huge void structure? Are there papers quoting a ...
299 views

### Where does the smell of electrostatic charge come from?

Everybody knows you can produce electrostatic charge rubbing two different materials together. But have you ever smelt e.g. at the plastic after charging it? There actually is a distinct ...
64 views

### What is the variable plotted on the y-axis on these Higgs exclusion graphs? [duplicate]

Possible Duplicate: Particle physics plots I have seen graphs like this in lots of talks by phenomenologists talking about the Higgs search (see for example FIG 3 in this paper or this blog ...
405 views

### Old Russian Physics Papers?

Where can one find old Russian scientific papers in physics, say, in the Proceedings of the Russian Academy of Sciences or Zhurnal Eksperimentalnoy i Teoreticheskoy Fiziki? Can they be found online ...
115 views

### Kerr Geometry, Separability and Twistors

One of the remarkable properties of the Kerr black hole geometry is that scalar field equations separate and are exactly solvable (reducible to quadrature), even though naively it does not have enough ...
8k views

### Are there planets that do not rotate on their axis?

I was reading a thread about how a pendulum would be affected if the Earth did not rotate and Larian's answer made me wonder if all planets rotate necessarily due to physics. So that's the question: ...
367 views

### How did L.H. Thomas derive his 1927 expressions for an electron with an axis?

I'm looking at the 1927 paper of Thomas, The Kinematics of an Electron with an Axis, where he shows that the instantaneous co-moving frame of an accelerating electron rotates and moves with some ...
387 views

### What percent of planets are in the position that they could be viewed edge-on from Earth? (and thus able to undergo transits)

Star number 12644769 from the Kepler Input Catalog was identified as an eclipsing binary with a 41-day period, from the detection of its mutual eclipses (9). Eclipses occur because the orbital ...
441 views

### What kind of curve would describe the rate of air coming out of a balloon?

If one graphed the volume per time of air being expelled from a common elastic balloon out of a hole of constant size relative to the balloon's surface area, would the curve of the graph be ...
469 views

### How do sunflowers rotate?

Is there a physics mechanism to explain how sunflowers rotate to always face the sun? I tried to find more information or references using google search, but no luck.
996 views

### Understanding Black hole information paradox?

I am not a physicist, I am a enthusiast trying to understand thinking behind "Holographic Principle" by Leonard Susskind. Recently I saw program on DS Through the wormhole - The riddle of the black ...
271 views

### Does 4D N = 3 supersymmetry exist?

Steven Weinberg's book "The Quantum Theory of Fields", volume 3, page 46 gives the following argument against N = 3 supersymmetry: "For global N = 4 supersymmetry there is just one supermultiplet ... ...
6k views

### Not sure of a homework solution involving average acceleration

A 50.0 g Super Ball traveling at 25.0 m/s bounces off a brick wall and rebounds at 22.0 m/s. A high-speed camera records this event. If the ball is in contact with the wall for 3.50 ms, what is the ...
5k views

### What is the electric potential at a point?

1) What does the electric potential at a point exactly mean? My teacher tells me that current flows from higher potential to lower potential but when I ask him the reason, he fails to give me a ...
273 views

### Over what distances can one send/ receive from a GPS chip implant in a dog?

I am not into all the tech details of communication via RF with implant chips (tracking chips) and so would like to ask how the known atmospheric pertubations of shortwave radio affect the distances ...
684 views

### How to calculate how many degrees the Sun is from the horizon?

Given a position on earth (latitude/longitude, and maybe also height relative to sea-level) and a time, what's the algorithm to find how many degrees the Sun is from the horizon? And the same for ...
183 views

### Axial Tilt and precession rate of exoplanets

The Earth's axis is 23.5 degrees away from othogonality to the ecliptic, and it takes about 26 000 years for it to precess fully. I have neither an intuitive sense nor the formula for precession ...
257 views

### Does entropy measure extractable work?

Entropy has two definitions, which come from two different branches of science: thermodynamics and information theory. Yet, they both are thought to agree. Is it true? Entropy, as seen from ...
92 views

### What is a quantum simulator?

What is the idea behind of quantum simulator aimed to study properties of matter, such as using quantum dots to study the exotic quantum states?
1k views

### right hand rule using left hand?

im kind of confused, the right hand rule is used to know where the direction the magnetic field created by the current is going . is there any particular reason why the right hand is used to ...
276 views

### Models of higher Chern-Simons type

It has long been clear that (the action functional of) Chern-Simons theory has various higher analogs and variations of interest. This includes of course traditional higher dimensional Chern-Simons ...
516 views

### Formula for polarized “light” transmission through close filters?

I'm still trying to understand photons (or polarized electromagnetic radiation). This question is similar to one of my previous questions, but different: Consider the famous demonstration of crossed ...
155 views

### Behaviour of liquid in vaccume

Is it possible for a liquid to exist in a high quality vacuume? For example, a few Torr. If so what are the methods for doing this?
425 views

### How can one localize the massless fermions in Dirac materials?

I noticed that finite electric potential cannot localize the low energy excitations in a graphene sheet. Is it possible to localize the massless fermions in the surface band of topological insulators ...
194 views

### Schottky and shot noise

I am looking for a little history on shot noise: when was it first predicted and first measured? In particular, what was the role of Schottky? His 1918 paper "Über spontane Stromschwankungen in ...
600 views

### Paramagnet: Negative specific heat?

for a simple paramagnet ($N$ magnetic moments with values $-\mu m_i$ and $m_i = -s, ..., s$) in an external magnetic field $B$, I have computed the Gibbs partition function and thus the Gibbs free ...
2k views

### How Fundamental is Spin-Orbit Coupling to Topological Insulators?

I'm well aware this is a very active area of research so the best answer one can give to this question may be incomplete. Topological states in condensed matter are well-known, even if not always ...
2k views

### Is visible light and radio waves made of the same thing?

I understand that there is such a thing as the electro magnetic spectrum, and that light and RF are both on it, so dose that mean that they are made of the same thing? Just at different frequencies.
70 views

### Phases of the moon video

I am an educator, and I am looking for a specific video. In the video, they ask some middle school students and some college graduates about why the moon has phases. Most of the students in both the ...
15 views

### Is it easier to learn more about the seasonal changes in an exoplanet's atmosphere when the exoplanet orbits a binary star system?

From a recent ScienceDaily article, we have this... Scientists detected the new planet in the Kepler-16 system, a pair of orbiting stars that eclipse each other from our vantage point on ...
488 views

### Physical interpretation of different selfadjoint extensions

Given a symmetric (densely defined) operator in a Hilbert space, there might be quite a lot of selfadjoint extensions to it. This might be the case for a Schrödinger operator with a "bad" potential. ...
4k views

### The Time That 2 Masses Will Collide Due To Newtonian Gravity

My friend and I have been wracking our heads with this one for the past 3 hours... We have 2 point masses, $m$ and $M$ in a perfect world separated by radius r. Starting from rest, they both begin to ...
357 views

### Interference of EM Waves with Orbital Angular Momentum

If you have two coherent collinear e-m beams of same frequency and polarization, but 180 degrees out of phase, they will destructively interfere. If you introduce orbital angular momentum of L=3 ...
177 views

### Trying to understand the weak gravitational field metric (3)

I've worked through Carroll's explanation of the Newtonian limit as far as $h_{00}=-2\phi$ (page 106 - Lecture Notes on General Relativity). As he's previously stated that ...
217 views

### Why do galaxies collide? Reconciling dark energy and an expanding universe with the fact that some galaxies are on a collision course

My layman understanding of cosmology is: galaxies are uniformly (more or less) spread throughout the universe, per the Big Bang and the fact that in a central explosion, all dispersed points are ...
576 views

### Why does the fundamental mode of a recorder disappear when you blow harder?

I have a simple recorder, like this: When I cover all the holes and blow gently, it blows at about 550 Hz, but when I blow more forcefully, it jumps an octave and blows 1100 Hz. What's the ...
5k views

### Focal Point vs where you see the images

I am trying to figure out where is the focal point and where is the image. I read some information online about the point where you see the image is the focal point, but however, my supervisor ...
263 views

### Quantum computing and quantum control

In 2009, Bernard Chazelle published a famous algorithms paper, "Natural Algorithms," in which he applied computational complexity techniques to a control theory model of bird flocking. Control theory ...
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### Significance of the hyperfinite $III_1$ factor for axiomatic quantum field theory

Using a form of the Haag-Kastler axioms for quantum field theory (see AQFT on the nLab for more details), it is possible in quite general contexts to prove that all local algebras are isomorphic to ...
159 views

### Can symmetry generators be used for quantization?

Take the Poincaré group for example. The conservation of rest-mass $m_0$ is generated by the invariance with respect to $p^2 = -\partial_\mu\partial^\mu$. Now if one simply claims The state where ...
566 views

### Why does the density of states in a solid scale as $\sqrt{E}$?

In three dimensions, the density of states of a free electron is the square root of the energy of the electron. Can somebody explain the relationship between this dependence and the shape/formation of ...
83 views

### Computing period, semi-major axis of binary

I have mass, $g$, and luminosity of each of the stars in a binary system, extracted from a model. I calculated the individual radii from $g$ and the mass. I am trying to compute $a$, but I seem to be ...
4k views

### Pressure at a given altitude?

I am trying to find out the pressure at a given altitude but have been disappointed to find the following equation does not work at all: (h = height in meters) Where sea level standard ...
I mean the Majorana representation of symmetric states, i.e., states of $n$ qubits invariant under a permutation of the qudits. See, for example, D. Markham, "Entanglement and symmetry in permutation ...