# Tag Info

1

A different angle on this that I DON'T believe is in conflict with Terry Bollinger's answer: whether you express a wavefunction in position co-ordinates, or, as its Fourier transform, i.e. in momentum co-ordindates, the two models are precisely the same. So neither the expression of a position co-ordinate wavefunction (such as you find from the solution of ...

0

A pure plane wave is not a physically realizable state for a real particle because it would require the particle's wave function to extend over infinite space. Even if the universe is open and infinite in size, it has only existed for a finite time, so no particle wave function would have had enough time to grow to infinity.

0

This is an interesting question and we'll assume that it has to do more with physics than biology. As a smart-ass side note, infinitely flat plane and "north" are mutually exclusive, but that's beside the point. Something to take note is that there is a blind spot in our eyes that is roughly $7.5^\circ$ tall and $5.5^\circ$ wide. I will be taking some ...

2

From your brief description, it sounds like you are operating a vacuum chuck. What kind of pumps are these? A very basic diaphragm or rotary vane pump will easily reach an ultimate vacuum of 100mbar or much lower. Since you are using the pump to hold an item, you probably do not need high vacuum or high pumping speed, because the atmospheric pressure outside ...

0

Yes, there is a systematic way of acquiring the line of best fit. Decide wether or not you are going to have a data point that intercepts the line. If you have an odd number of results, then the answer to this is yes. Your line will pass through one data point and evenly distribute the data points on corresponding sides. Eg with 11 data points, the line ...

0

This is, generally, difficult question. But usually, programs for fits includes already a number of predefined functions. I use free Java program called SCaVis (http://jwork.org/scavis) for data fits and it has a number of predefined functions, such as polynomial, exponential, logs, etc. I just look at my data an make the decision about what function can ...

0

Your figures seem problematic. For example, the volume of a 10m radius sphere is below 10^4m3, air density at normal conditions is, very roughly, 1kg/m3, so how do you get more than 10^8 N buoyancy force? According to calculations in US patent application 11/517915 (Akhmeteli, Gavrilin, Layered Shell Vacuum Balloons, you can find it at USPTO site or at ...

1

In the recent ion trap designs much of the emphasis is on traps that can store ions in multiple trapping zones and transport ions between them. This is crucial for the ion trap realizations of a quantum computer with many ions (qubits). In the ion traps that are intended to be used for quantum information processing, we need to transport single and multiple ...

4

Yes it can be done, and indeed it's a well established technology called active noise control. The idea is based on destructive interference. If at some point two sound waves have the same intensity and frequency and they're 180º out of phase then they will sum to zero and the sound intensity at that point will be zero. Your phrase negative sound just means ...

0

In solid hydrogen, the molecules freely rotate. See Ultrahigh-pressure transitions in solid hydrogen at page 672. So at least because the molecules are constantly rotating, even in the solid, the alignment described in the question is not possible. Also, how could one say that a particular atom of the molecule is spin up and the other down, as opposed ...

0

It would actually be neither. Percentage is always positive, so we invoke absolute value to get $$E=\frac{|A-B|}{B}\times 100$$ Actually, we can also use $$E=\frac{|B-A|}{B}\times 100$$ Percent error is always taken with respect to the known quantity because it is important to know how far off the measurement is from the known value, and not vice versa - ...

2

Typically it is the ferrite cores in inductors/transformers that resonate mechanically, or through magnetostrictive effects that produce a high pitched whine. Switching PSUs are the main culprit. It can also occur when the EM fields interact with steel components in the PSU.

0

To convert one voltage to a higher voltage one often uses a transformer or a ladder network (or a combination of these). The above from Wikipedia shows a Cockroft-Walton multiplier - commonly used to step up an alternating waveform. It acts like a bucket brigade - the charge on each capacitor is being passed on to the next capacitor, at a higher voltage, ...

0

The problem is that your analysis is all done from the perspective of the frame that measures the box to be moving at 0.1c -- in this frame, it's true that the time for the light to get from the source to the wall is different from the time for the light to get from the wall back to the source. But if these same events are measured by someone inside the box ...

2

Since John is not addressing positrons one should know that positrons are easily created once a photon has more energy than twice the mass of the electron, in electron positron pairs. This can be seen clearly in this bubble chamber picture: where the positron is shown in purple on the right. One knows they are electrons (positrons) because of the ...

1

(This is only a partial answer to one-third of your question.) I'm sure you already know this but ... Inhomogeneous broadening is what you're talking about where different Nd atoms are in different microscopic environments and therefore emit at different wavelengths. Homogeneous broadening is where even a single Nd atom can emit at some range of different ...

12

Creating anti-protons is straightforward in principle because any high energy collision produces a shower of protons, antiprotons and various types of pions. The pions decay in a few nanoseconds, so you just have to wait for the pions to decay then separate the antiprotons from the protons. At Fermilab a 120GeV proton beam was collided with a nickel target ...

0

This page has a good simple summary of the experiment, they present the following simple schematic of a delayed choice quantum eraser (the same as Figure 1 in the original paper by Kim et al.): In this case, if the entangled "idler photon" is detected by Alice at D3 or D4 then she will know whether the "signal photon" went through slit A or slit B, but if ...

3

It is hard to prove something experimentally that is actually an equivalence of two theories on a mathematical level. The AdS/CFT correspondence is supposed to be an exact correspondence between a quantum field theory and a string theory. However, it is in principle possible to find support for the correspondence in the following way: construct the ...

0

No. Friction is a force that does not act normal to the surface, but rather perpendicular to the surface. Trains do not derail when travelling on high speeds across turns simply because the train tracks are slightly inclined.

2

The following has ben found via Wikipedia page “Gravitational interaction of antimatter”. Another experimental test has been provided by the supernova SN1987a (anti)neutrinos, and this has been published in two brief reports in Phys. Rev. D in 1988 [1] and 1989 [2]. After the explosion of this supernova, 19 antineutrinos have been detected at IMB and ...

4

As well as the antihydrogen experiments, ALPHA, AEGIS and GBAR that were mentioned in other answers, there are a couple of other experiments, though they haven't had any results. In the 60's, they tried the obvious thing of dropping positrons down a metal tube (paper), but it didn't work, for the subtle reason that the electrons in the metal sag under ...

1

There are, by my count, 33 other official weather observation stations within Sydney. Here's a map: With regard to the Sydney - Observation Hills (Station ID 066062) station -- That freeway didn't exist when the station was built. How could it? That station dates back to 1858. The station was moved 150 meters to its current location in 1917. That tiny ...

2

There are different layers of reconstruction, at each step the amount of data is reduced with the goal of inferring the momenta, type and direction of the particles produced first in the collision: pulse shape reconstruction: the electronic signals caused by particles interacting with the detector cells are digitized at a rate of 40 MHz at LHC. Some ...

0

It no doubt does. Solar radiation will heat surfaces, and the rate at which a black surface absorbs that heat is greater than for other colors. That heat is then partly lost by radiation, partly by conduction, and partly by convection. If you assume the last two terms will be the same regardless of the color, then you can see why a black surface will become ...

19

The only experiment I know of was done by the ALPHA team at CERN. The results are published in this paper. The error bounds are huge - all the team were able to say is that the upper limit for the gravitational mass of antihydrogen is no greater than 75 times its inertial mass! However I believe an updated version of the experiment, ALPHA2, is in progress ...

2

The paper you point to describes the experimental test by Rowe et al., in Wineland’s group in 2001. This experiment was performed in an ion trap, where Alice and Bob are separated by 3 µm, and therefore it is impossible in practice to close the locality loophole. As they say in the methods section, even though all known interactions would cause ...

0

I am curious about the following line in your derivation: Our quadcopter measures 47cm motor-to-motor, so r = 0.235m. Let’s calculate the torque. Presumably to pitch the copter without changing the over all lift, you need one pair of rotors to slow down and the other pair to speed up. It was not clear to me that the factor of two that this results in ...

0

You just have to make sure you hit the center of mass to give it a velocity you need, irrespective of the position of the pivot, whether it is at the end of the rod or 0.1m away from it. If you hit the center of mass of the rod and make it move with a velocity that is just enough for it to reach the vertical position above the pivot, that velocity will be ...

1

The statement is not true, because there are counter examples. A U(1) spin liquid is gapless, but it is insulating. An $s$-wave superconductor is fully gapped, but it is (super)conducting.

1

the cooling process depends on many factors: - convection, radiation and conduction inside the body. Exponential decay is good only if the lumped capacitance model is appropiate and if the relation with radiation is linear. I would say that in your case you also had convection inside the fluid. And ontop of that the relation with radiation is not linear it ...

1

It is not generally true that a gapped system is insulating. Or more precisely, this statement is not detailed enough to be said true or false generically. One case where this is true is for non-interacting particles (say, free electron in a lattice). For interacting particles, it is much more subtle. In particular, just stating "gapped system" is not ...

1

Your understanding is basically correct. Some materials, intrinsic semiconductors, have small band gaps so that at room temperature (for example) there is enough thermal energy around to promote some electrons to the conduction band, and some holes to the valence band. These materials have the kind of gap that you describe, but are not insulators. Another ...

0

http://qudev.ethz.ch/content/courses/QSIT08/pdfs/Rowe01.pdf The experiment is repeated Ntot 20 000 times at each of the four sets of phases So it's about 80 000 to achieve $2,25 \pm 0,03$

5

You do exactly the same thing: you "rotate" the state and then measure along whatever axis your measurement apparatus happens to measure. The only difference here is that the "rotation" does not necessarily correspond to a rotation in space like it does for a true spin. What follows is a detailed description of how we do rotations of a generic 2 level ...

0

You could try PEBBLES which is freeware AFAIK

0

The human eye, in dark-adapted conditions, has been shown to be capable of detecting a single photon (which is to say, the retina reacts, the signal gets to the brain, and [magic happens] to generate a response in the conscious parts of the brain. Since what you're asking about is the release of one photon, it doesn't matter what the source is. So long ...

Top 50 recent answers are included