yevgeny

And what if he is still waiting that someone will answer the questions he posed here? :whistle:

They are observables. You can measure anyone of them.

Hi! Unfortunately, I don't know much about physics programs in the US. Maybe you can use this to get some information: http://www.phds.org/rankings/getWeights.php?d=25 Yevgeny

I applied to Harvard, Princeton, Stanford, MIT, Caltech, and Cornell. I have been admitted to all of them. I decided to go to Harvard. ;)

I have been admitted to all places which I applied to :)

This is OK. In the limit of dq -> 0, k' becomes INFINITE. We all know this: take a long spring (1 m) so that you can easily stretch it by 10 cm. Then take a small piece of that spring (1 cm). It will be 100 times harder to stretch it by 10 cm. This is wrong. Which body are you considering? If you are considering the spring as a whole, then you shouldn't take into account the force applied by the string itself. Rather you should take into account the force applied by the roof, which you should somehow calculate. This is also wrong. The mass is not distributed uniformly along the stretched spring: the sping is stretched more at the top than at the bottom, so that the center of mass is lower than half the length.

It does not depend on the problem. By specifying that Sx = S, a full quantum-mechanical description of the spin is given. The calculation is correct even if the environment is different along y and z axes.

Energy per particle: u® = A/R^n + (kq^2/R)*sum[(-1)^n / n] where the summation is from 1 to infinity. The sum equals -ln2. Why specifically are you worried about it?

Doesn't the ENERGY of the electromagnetic field affect g?

Two of my friends gave me an answer to the original question. Moshe G. answered that looking at the time-reversed picture shows that the magnetization in both directions MUST BE THE SAME (when the direction of time is reversed, the directions of the magnetic field and the magnetization are reversed, while the crystal remains unchanged; and it is known that the relevant laws of physics are symmetric in time). Vadim K. answered that looking at the mirror reflection, with the mirror perpendicular to the line of atoms, also shows that the magnetization in both directions MUST BE THE SAME (in the mirror, the direction of the crystal is reversed, but the magnetic field and the magnetization keep their directions; and it is known that the relevant laws of physics are symmetric under mirror reflection). I added then that if the mirror is parallel to the line of atoms, it also proves this statement in a similar way. So simple! [banana]

Help - I think this is the right place for it. David Bohm - what exactly? I haven't read the "The Physics of tao"... What are your plans in physics, by the way? And what are you doing now? Yevgeny.

Dear Maria/Mihaela/Licorna (why so many names? :shy:) , What happened on my real GRE (including the results) is described in the topic "My GRE": http://www.TestMagic.com/forum/topic.asp?TOPIC_ID=8875 In 3 words: it was OK! As to the admission decisions, it's too early yet for most of them, but I have first signs of success. Hope you study well and answer all my questions here... :) Best regards Yevgeny

In empty space, there is a system of coordinates (t,x,y,z) in which the fundamental tensor equals: g = diag(1,-1,-1,-1) How will it be modified if a uniform electric field E in the direction of the x axis is added?

The official one is here: ftp://ftp.ets.org/pub/gre/Physics.pdf :drunk:

I found out that ecm was right about this (which is not really surprising about ecm :D). See here: http://curious.astro.cornell.edu/question.php?number=575

Hi John, First you need to learn Hebrew, and only then you will be able to solve Israeli tests. :D I am doing condensed matter, but I am thinking about particle physics as an interesting option for me. :) Yevgeny.

Hi John, I think the answer to the question of how to prepare is very personal. So I can tell you only what I myself did. I didn't see a need (and I didn't have time) to read books which cover all the material in the GRE, not even books which cover the main topics. I did read about some specific topics in which I felt myself weak. I did summarize all the laws one needs to know. After they were organized on the paper, I didn't need to learn them, because most of them were already in my mind. It is important to note that in order to succeed in the GRE you don't need to know all the topics covered there because on the exam itself you barely have time to read all the questions, even if you are very good. It is usually enough to answer (correctly) only about 70% of the questions in order to get the MAXIMAL score. (But you need more correct answers if some of your answers are wrong.) I think one should skip difficult questions in the exam - there are many easy questions ahead. Try this when solving the sample test. It is also important to train yourself solving simple problems fast. A set of Israeli high school final exams in physics served this purpose for me. Actually, I think most of the GRE topics were there. I wish you success! Yevgeny :)

When looking at a galaxy which moves from us at half the speed of light due to the universe expansion: Will we see time dilation? Will we see Lorentz contraction?

Do any galaxies move faster than the speed of light, due to expansion of the universe?

Excellent! :)

I mean some arrangement of nucleons. For example, "-" is proton, "X" is neutron. The scheme shows their arrangement is space.

I agree that the effect of magnetic field in the opposite direction is the same. What I mean is the following. You think: Field applied up: spin rotating clockwise, particles emitted up. Let's call this (A). Reflection of (A): spin rotating counter-clockwise, particles emitted up. Let's call this (B). (B) is the same as: spin rotating clockwise, particles emitted down. Let's call this ©. But © does not happen, therefore the symmetry under mirror reflection breaks down. I suggest (just an example): Field applied up: spin rotating clockwise nucleons arranged like this: -X- XXX particles emitted up This is (A). Reflection of (A): spin rotating counter-clockwise nucleons arranged like this: -X- XXX particles emitted up This is (B). (B) is same as: spin rotating clockwise nucleons arranged like this: XXX -X- particles emitted down This is ©. But © is never tested in the experiment described above! It is different from the original experiment.

As known, radiation intensity decreases with the distance from the source as 1/R^2. When light was emitted from a far star, the star was at a distance D1 from Earth, and had a velocity according to the Hubble formula. When the light arrived to Earth the star was at a distance D2 from the Earth. What value should we use to calculate the intensity of the radiation: D1, D2, or something in between? (No significant forces act on the star or the Earth during this period. You may also assume that the universe is flat and that the rate of expansion of the universe is essentially constant during the relevant period of time.)

But how about the electroweak force? :D

In general, the magnetic field can affect many things through the spin-orbit coupling. But I don't have anything specific against the cobalt nuclei experiment. As to the tau-theta particle, I have opened a discussion on this topic here: http://www.TestMagic.com/forum/topic.asp?TOPIC_ID=10017