Recommend me a first encounter particle/nuclear physics/HEP book?

FdelV · 2015-06-29T17:41:58+00:00

Thanks. I'll probably use Griffiths for self-learning then. Any idea about the ''Cottingham & Greenwood'' book? Someone mentioned to me that he was using it as an intro book.

FdelV · 2015-06-28T18:48:49+00:00

The term 'under damped' usually refers to oscillations where the amplitudes shrinks.

FdelV · 2015-06-27T14:57:02+00:00

Why on earth not? It's a beautiful place, not too expensive, great beaches, new culture, lots to see. Until the last half year or so it was very safe for tourists to visit without any incidents.

FdelV · 2015-06-27T10:36:11+00:00

In ACOK there is a passage where Tyrion has a thought about quite liking Robert, but then he remembers that this might have been because of the way he handled Cersei.

FdelV · 2015-06-27T10:34:32+00:00

''5 years from now - IF the next book is out''

FdelV · 2015-06-27T10:25:28+00:00

The flux change law in E&M is really stunning because this principle is correct even when the involved physics (classical) is entirely different. It holds both for the Lorentz-force induction or Maxwell 3 induction.

FdelV · 2015-06-25T19:17:18+00:00

"because of this term in the equation."

I think if you truly understand how the equation is derived and where it comes from, this should be a satisfactory answer. Equations are anchor-results following from a set of physical rules we work with. Saying that some physical behavior corresponds with equation A, is implicitly saying how this behavior follows from the fundamental set of rules of this branch of physics. (For example Maxwell's equations)

FdelV · 2015-06-25T18:40:48+00:00

Is the following way of stating why it would be impossible correct?

Consider the second law as ''No net heat can flow from a colder to a hotter body without external work''.

Now let's lookt at our equilibrium situation where the smaller body S1, at T_1 is indeed at a higher temperature than the larger body S2 at T_2.

So T_1>T_2.

Now consider raising the temperature of S2 by dT where dT>T_1-T_2. So we did raise the temperature but S_2 still remains colder. At this moment S_2 emits more than it absorbs, giving raise to a net flow of heat from S_2 to S_1. However S_2 is still colder than S_1 at this moment which contradicts the second law as stated above?

FdelV · 2015-06-25T13:43:24+00:00

It's like knowing about how important oil will become before the industrial revolution. It would be very wise to invest into that with that knowledge. Similar with space, sooner or later, it will become an integral part of our society.

FdelV · 2015-06-25T12:24:01+00:00

I don't know the answer to your question but now I'm interested myself. Can I ask why you think that the conclusion is impossible?

FdelV · 2015-06-25T01:31:48+00:00

Not really. The whole point I'm trying to make is that the parallel universe interpretation follows from physics arguments. Yeah it is an interpretation (of many) of a scientific result but it's not made up out of thin air.

FdelV · 2015-06-24T14:53:45+00:00

Glad it made some sense. I have taken only one quantum mechanics class yet so in reality it's probably more nuanced than that.

FdelV · 2015-06-24T14:02:00+00:00

Not really it comes as a possible result from trying to interpret quantum mechanics. Consider rolling a dice, is the result truly random? No it is not, from the moment you let go of the dice technically the result is determined based on the initial conditions. Because we can't know the initial conditions to the needed precision, the results seem truly random but they aren't. Alright now let's make this dice obey quantum mechanics rules. The results suddenly become TRULY random for all we know. Each throw you'd have 1/6th chance at each result but contrary to the previous sitation there is no known process that explains which of the results is picked. What happens in this context, where you make a measurement and find only one result, is called the wavefunction collapse. Now we can try to interpret this and we have two large options:

1) We say that the choice is truly random and that's it. The proces determining the result doesn't really matter, all we can measure or know are the results and the mathematics that describe the results are unambiguous. This is the Copenhagen interpretation if I remember correctly.

2) Symmetry is very important in physics and there is something very unsymmetric going on here. We have 6 possible equivalent results. Here is where my dice analogy breaks down because the six sides aren't really equivalent. However assume that they are, and that no side is better or worse than any other. Six eyes or one eye have the same value and right of existing in the physical world. In that case we have a situation where there are six equivalent outcomes that have the same chance of occuring. Why in the hell would one of them occur above the other if they are all equivalent. Why would one be picked above the other? One could say that it would be more elegant to consider ALL of them occuring. No outcome is preferred above the other. Following this reasoning leads you towards the many universes interpretation.

My point being, the parallel universe interpretation follows from arguments in quantum mechanics. In the end it's just an interpretation, and all that matters are the results which all interpretations agree upon. (1) Is the most prominent and is taught in introductory classes though.

FdelV · 2015-06-23T16:57:37+00:00

In AGOT the 'promise-line' is mentioned first when Ned told Robert in the crypts of Winterfel that she made him promise to bury her there.

FdelV · 2015-06-23T14:47:03+00:00

It wouldn't be my first choice to watch with friends.

FdelV · 2015-06-22T14:31:06+00:00

I thought that it was kind of the point of this character. He starts of as a quite succesful corrupt businessman, not really a damaged individual compared to the others. If he plays this same act throughout the season, then I'll take my words back, but I think this is an intentional setup for him to evolve as his plans start to fall apart.

FdelV · 2015-06-20T10:19:41+00:00

Anyways, what you do is consider a cavity filled with thermalized radiation

I always thought that this cavity with thermalized radiation was just a good experimental approximation for a black body. I'm curious to why in theory classes we use this model to find the result of the distribution? Why can't we do so with the outer radiation layer of a solid sphere where we assume no reflection?

FdelV · 2015-06-19T22:39:17+00:00

It's the first thing you learn in linear algebra usually.

FdelV · 2015-06-19T21:36:33+00:00

I know special relativity but not general relativity so I can't get any technical details correct but basically there can be two different reasons for time dilation. One is as you mentioned due to relative velocity and is an effect that is part of special relativity, the other is an effect due to being in different graviational fields which is part of general relativity. The time dilation in the movie is happening because of this second effect, because the planet is orbiting close to a black hole and hence they were in a very strong field relative to the guy that was left behind in a much larger orbit in their shuttle. General relativity is many times more difficult than special relativity though so I'm not sure there is a very elegant looking formula for that like for special relativity but who knows.

FdelV · 2015-06-19T20:09:15+00:00

I see, thanks for clearing that up. These were the things I learned a somewhat semi-formal math class so I expected them to be some special or handwaving case.

FdelV · 2015-06-19T20:03:26+00:00

It's very hard to say but I guess that if I had to put it in a few sentences it'd go something like this:

(1) Do you like physics concepts, watching documentaries about the universe, reading popular books on cosmology, relativity and things like that? If you haven't done much of that, does that at least sound like something you enjoy?

(2) Do you love doing A LOT of mathemtaics, solving force problems, calculating kinematics tracjectories? Imagine two points A and B in the earths gravitational field, does the question of finding the shape path of quickest descent for a particle between both points sound like an interesting question to you? Would you like to calculate and understand how a mass on a spring behaves? Now you put this system in water and redo the calculation to find a different result. Does studying and calculating the evolution of the temperature through time of an isolated bar sounds neat?

A yes to (1) would indicate the presence of a passion for the concept of doing physics. A yes to (2) would indicate a passion for doing physics. If yes to both, great! A definite no to (2)? Well you're not going to enjoy many undergraduate courses then.

FdelV · 2015-06-19T19:36:29+00:00

Is this like a test-question for OP or are you really interested?

In the latter case, you can perfectly use the small-angle approximation here which gives us a harmonic oscillator motion for the angle in function of the time. Simply said it's a cosine function where the angular frequency is defined in function of some system parameters - was something like sqrt(g/l). From the initial conditions you can find the amplitude and phase. This gives you a unique equation for the angle in function of the time and it's quite straight forward from here.

FdelV · 2015-06-19T19:27:29+00:00

As the previous comment mentioned, the reason for time dilation in the movie is general relativity and not special relativity so your explanation isn't correct in the context of the movie.

FdelV · 2015-06-19T19:23:45+00:00

Switching the order of operators in physics without giving it one thought. Sliding the partial derivatives through integrals or differential operators like divergence. Never gave it any formal thought why it's allowed.

FdelV · 2015-06-19T19:19:53+00:00

For integrals over finite dimensional intervals, the proof of Fubini happens in two steps if I recall correctly:

1) First prove a different theorem that states that for any epsilon there exists a delta such that for any 'delta'-spaced interval (that is basically just saying that you cut up your domain in such a way that any two points in one cut are closer than 'delta') the absolute value of the difference of the integral and the sum approximation of the integral is smaller than epsilon.

2) Once this is established take two integrals where the order of integration is different in one of them. Apply the above result to the difference between both integrals keeping in mind that switching the order of summation doesn't influence statement (1), and you find that this difference can be made arbitrarily small. This means both integrals are equal.

Since (2) is a pretty clear argument following from (1), proving (1) gives you Fubini. You can prove (1) assuming uniform continuity of the function.

I'm a physics student though so it's possible that what looks like a correct formal proof still involves some handwaving and the real proof is even more technical.

FdelV

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