It is well accepted that quantum theory has well adapted itself to the requirements of special relativity. Quantum field theories are perfect examples of this peaceful coexistence. However I sometimes tend to feel little uneasy about some aspects. Consider an EPR pair of particles light years apart. Suppose there are 2 observers moving relative to each other with constant relative velocity. Let us consider, there are spin detection mechanism at both end for each particle. Now suppose one of the observer is at rest w.r.t. the detector for the first particle. As soon as the detection made, the wave function of the 2 particle entangled system will collapse instantaneously and the second particle must realize a definite opposite spin value. Now due to relativity of simultaneity, the second observer may claim that the collapse of the wave function for the two particle system is not simultaneous. He may even claim that the second particle is measured first. In that case a special frame of reference will be privileged, the frame at which the wave function collapsed instantaneously. This will cause a significant strain on the core principle of special relativity.

I am sure the above reasoning is flawed. My question is where?

In all examples that I know, tachyons are described by scalar fields. I was wondering why you can't have a tachyon with spin 1. If this spinning tachyon were to condense to a vacuum, the vacuum wouldn't be Lorentz invariant---seems exotic but not a-priori inconsistent. Is there some stronger consistency requirement which rules out spinning tachyons? If someone could provide a reference that would be helpful too!

Here's another confusion: I was reading Wikipedia, which claims that tachyons should be spinless and obey Fermi-Dirac statistics(?). (They reference an original paper by G. Feinberg which unfortunately I am not wealthy enough to download). The claim about Fermi-Dirac statistics is baffling---isn't the Higgs field a boson? Does anyone understand what they're talking about?

I'm begining to study Quantization of field with the second quantization formalism. I've studied phononic field, electromagnetic field in the vacuum and a generic relativistical scalar field.

I asked to me if is possible doing the same thing with the Gravitational Field Hamiltonian.

I've heard that we can do it only in the condition of linearized Gravity and we obtain a field with spin 2, but we can't do it in the general condition because we don't have quantization conditions.

What are these conditions? And how can we obtain only in linearized gravity the quantized field? And how it has got spin 2?

This question has its origin to the reference on the Aegis experiment at CERN where they aim to produce super cooled antihydrogen and detect whether its reaction to gravity is negative.

It set me thinking that the beams in the Tevatron circulate for more than a second and everything falls about 4.9 meters in a second, so the bunches must be falling too. This of course will be compensated by the fields that keep the bunches in track among all the other corrections necessary. If though the antiprotons have a different behavior under gravity, this difference would appear in the orbits of protons and antiprotons.

The question has two points: a) since the beams are travelling equal and opposite paths through the magnetic circuit, a negative gravity effect on antiprotons would disperse the antiproton beam up with respect to the path of the proton one. Could one get a limit on the magnitude of the gravitational effect difference between protons and antiprotons from this?

I found one reference where the antiproton beam has a different behavior in chromaticity than the proton one, and it is explained away.

Now I am completely vague about beam dynamics which I have filed under "art" rather than "physics" but b) am wondering whether this observed difference could be interpreted as a gravitational field difference in a dedicated experiment.

Maybe there are beam engineers reading this list. My feeling is that if antiparticles had negative gravity interactions , beam engineers would have detected it since the first e+e- machine, but feelings can be wrong.

How do you effectively study physics? How does one read a physics book instead or just staring at it for hours?

(Apologies in advance if the question is ill-posed or too subjective in its current form to meet the requirements of the FAQ; I'd certainly appreciate any suggestions for its modification if need be.)

Assume an observer sent a beam of photons close to an event horizon, say at some distance x (a distance far enough to avoid the photons falling in.) This light would still be observable, albeit red shifted and with it's path curved appropriately. Now assume the black hole absorbs enough mass to expand it's event horizon beyond the distance x. This stream of photons would stop. Does the observer not have information about a process that occurred exactly at the event horizon, that is it's expansion? Isn't this a region that one should not be able to get any information about due to the fact that nothing could contact the event horizon and return to the observer?

Seeing this as an academic community, I hope this question is on-topic. Academia is still a long way from beta :(

I have a few questions about reading journal papers in the field of engineering/applied physics.

How do you keep and schedule a reading list?
From the more recent papers, how do you track down the one (or few) papers that started an idea or technology?
Then conversely, how do you move forward in time to trace how that technology evolved? How do you decide which is the next paper to read?
(I think being able to do the tasks of 2 and 3 could help me formulate my own research questions in the future)
How do you retain the gist of the information you read from an article?
How do you do the dirty work of the above? What software do you use, if at all? If you write it down in a notebook, what are the essential data points? Like the date you read the paper, publication date, title, author, then writing down (or illustrating) what you see with your mind's eye the information that the article presented, and... anything else?
I envision a notebook with the ideas I learned, then posing my own questions after reading each article. How do you do it?

You may (or may not) answer those questions one-by-one, but they're there to give you an idea of what I want to find out. Offers to make this community wiki are very welcome.

A proton follows the path shown in (Figure 1) . Its initial speed is v0 = 1.4

Two 11cm -long thin glass rods uniformly charged to +13nC are placed side by side, 4.0 cm apart. What are the electric field strengths E1, E2, and E3 at distances 1.0 cm, 2.0 cm, and 3.0 cm to the right of the rod on the left, along the line connecting the midpoints of the two rods?

Specify the electric field strength E1.

Specify the electric field strength E2.

Specify the electric field strength E3.

Two 11cm -long thin glass rods uniformly charged to +13nC are placed side by side, 4.0 cm apart. What are the electric field strengths E1, E2, and E3 at distances 1.0 cm, 2.0 cm, and 3.0 cm to the right of the rod on the left, along the line connecting the midpoints of the two rods?

Specify the electric field strength E1.

Specify the electric field strength E2.

Specify the electric field strength E3.

Why is electromagnets so important in our everyday lives and how is it used.

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In a two-slit interference experiment, with a light source of unknown wavelength, the following data are measured:

slit separation, d = 0.22 mm,

distance of slits from the screen, L = 2.39 m, (large enough that the small-angle approximation applies),

separation between the m =

Senior physicists constantly complain they spend too much time on administration, teaching, getting grants, serving in committees, peer-reviewing articles, supervising, etc. . Do senior physicists conduct research by getting their post-docs and graduate students to do all the intensive work for them?