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  1. Matterwave

    Finding the sine of the angle between 2 rays

    Hello, say you are on the unit sphere and you have 2 rays intersecting it from the origin. You know the spherical coordinates of where these 2 rays intersect the sphere ##(\theta_1,\phi_1),(\theta_2,\phi_2)##. Now, because we know the dot product of two vectors, it is simple to get that the...
  2. Matterwave

    Fortran [Fortran] Quick question about complex exponentials

    Hey, so I just have a quick question. I am trying to set a complex variable (in an array) as ##e^{i\alpha_1}## and the line I used in my code looks like this: hmajphasemix(2,2)=(cos(alpha1),sin(alpha1)) But the compiler is telling me that it "expects a right parenthesis" at this line. I'm...
  3. Matterwave

    Fortran [FORTRAN] How did I screw up my code?

    Hi guys, there's a bug in my code which I've been trying to get rid of for the last 2 weeks. I'm completely out of ideas now on what it is so I have to turn to you guys for help. The code is here: module helectron use params use parallel !* electron density parameters integer ...
  4. Matterwave

    Fortran [FORTRAN] Code misassigning values

    Hi guys, I can't figure this one out. Here I am working with a piece of code which should read in a grid of 2 arrays, a radius array and an electron fraction array. The code looks like this: subroutine varelec_init(varelecfrac,elecprofile,effilename,elecfracname) integer ...
  5. Matterwave

    Are Jacobi fields defined at intersection points?

    I have some questions with regards to conjugate points on a congruence of time-like geodesics (will be referring to Wald 9.3 throughout). First, we define ##\gamma## to be a time-like geodesic with tangent ##\xi^a## parametrized by ##\tau## and with ##p\in\gamma##. We consider the "congruence of...
  6. Matterwave

    Remind me why FLRW curvature can't switch between cases

    Hi, as we all know, the FLRW metric has 3 types of spatial curvatures, spherical, flat, and hyperbolic. I understand that of course due to homogeneity, this curvature must be spatially everywhere the same and so can not depend on the spatial coordinates. However, I can't recall what is the...
  7. Matterwave

    Proper mass vs Schwarzschild Mass

    Hello guys, I am reading through Wald chapter 6 section 2 on the interior Schwarzschild solution. In it he states that matching the interior solution to the exterior (Schwarzschild) solution gives a Schwarzschild mass of $$M=4\pi\int_0^R \rho(r)r^2 d$$ This would presumably be the same mass...
  8. Matterwave

    PMNS Matrix parameterization

    Hi guys, The wikipedia page on the PMNS matrix talks about there being a way to parametrize any 3x3 (special) unitary matrix by 4 parameters: However, I am quite sure SU(3) has...
  9. Matterwave

    MSW Hamiltonian

    Hi guys, I was wondering if anyone knows of a good source/paper that I can find online that details how to derive the MSW Hamiltonian from a field-theoretic approach, or from an effective field theory approach or anything like that? Every time I study the MSW effect, the Hamiltonian...
  10. Matterwave

    Fortran [FORTRAN] Runtime error

    Hi guys, I've been tinkering with this code for a while now, as you probably have seen from my other threads. Right now I am working on changing the code around so that it actually writes out the correct output instead of the old output. I am getting this runtime error: At line 2057 of file...
  11. Matterwave

    Fortran [FORTRAN] Assigning bad values in arrays

    Hi, I just realized that I have been making bad array assignments in my code. Specifically, I think I have been assigning to slots that the array does not have. For example, I might declare an array: int,parameter :: nflavor=3 int,parameter :: nflavor2=nflavor*2 real,dimension(nflavor)::x...
  12. Matterwave

    Fortran [FORTRAN]Compiler if statements

    Hi guys, I'm not really sure what these are called, so I just made a title to the best of my knowledge. I have some questions on some if-statements that I see in some code I'm working with. I will see if-statements like this: #ifdef mpi ... #endif I know that this tells the compiler that if...
  13. Matterwave

    Fortran [Fortran] something very peculiar

    Hello guys, As, you probably know by now, I've been trying to run this piece of code for a while now. I finally got it to run and then I realized something very weird is happening! So in my code, which simulates neutrino evolution, I have made 3 conditional statements in the evolution stage of...
  14. Matterwave

    Hard to read code

    Hi, is it possible to make the text that is wrapped in [code[ wrappers darker and easier to read? It's so light right now: test Look at this text! It's hard to read! Oh noes!
  15. Matterwave

    Makefile confusion

    Hello guys, I am trying to run a pretty substantial piece of code, coded in Fortran. There are many many modules (~10) and the dependencies of one module/piece of code on another is quite complex. As I am not the original author of the code, I am still not intimately familiar with every single...
  16. Matterwave

    Youtube embedding in Chat (shoutbox)

    So, since the shoutbox refreshes its page every time a message is entered, an embedded youtube video will also reset when I type something into the shoutbox, making actually watching the video difficult.
  17. Matterwave

    Fortran [Fortran] A piece of code that confuses me

    Hello all, There is a subroutine in the code I'm working on that looks like this: subroutine onestep(iter,iegy,icos,jcos,iphi,rinit,rfin, & & v2,v2bar,hel,helbar,drdis, & & psib,psie,psibarb,psibare,err) use params use helectron use angles use neutrinodist use parallel...
  18. Matterwave

    Fortran [Fortran] Functions and naming conventions

    Hi guys, In the code I'm working on there are a few functions that will be used to find a Hamiltonian, which I will then use in later parts of the code to find the time evolution of my system. Right now I have it set up so that the function names are actually the names I want to give the...
  19. Matterwave

    LaTeX In-line Latex not working

    Is it just me or is in-line Latex not working here anymore? ##\mu,\nu## versus $$\mu,\nu$$
  20. Matterwave

    Avatar image compression

    Hi, is the forum compressing my avatar image? I made a 300x300 avatar, and it is very clear (the original resolution is quite high), but on PF it looks very fuzzy. Is there some compression of the file going on? How can I make it not fuzzy? It annoys me -.-
  21. Matterwave

    Icon identifying which treads i've posted in

    Is this icon now gone with this new version? I like to know which treads I've contributed in to see if the OP has follow up questions, etc. It makes things a lot easier for me.
  22. Matterwave

    Chat is not working

    All day the chat has been a blank white page for me. Is anyone else having this problem?
  23. Matterwave

    Fortran [FORTRAN] Help figuring out zheev

    Hello guys, I am in need of a subroutine that diagonalizes a nxn Hermitian matrix (really I'm just looking for the eigenvalues and eigenvectors of course). Looking online I found that LAPACK has a zheev subroutine that presumably does just this. I am a little confused on how to use this...
  24. Matterwave

    Fortran Fortran array declarations

    Hi, I'm just wondering real quick, are equations allowed in array declarations? For example: int :: y=2 int, dimension(2*y):: x ?
  25. Matterwave

    Dirac vs Majorana Neutrinos

    Hi, I recently attended several lectures on the topic of neutrino astrophysics. I wanted to verify some of the fact that I gleaned for them, specifically about the Dirac vs Majorana nature of neutrinos. 1) The most basic fact first. If a neutrino is Dirac in nature, then it has 3 flavors...
  26. Matterwave

    Log(x) do you assume base 10 or base e?

    So, out of curiosity, when you guys see log(x) do you assume base 10 or base e? Because I just wasted 2 hours of my life wondering how I got a problem wrong due to the fact that I assumed base e and the problem assumes base 10...:cry:
  27. Matterwave

    Regarding the Hawking radiation

    Hello guys. From my understanding of the Hawking radiation, it is a consequence of QFT in curved space time. The fact that a uniformly accelerated observer sees the Unruh radiation means that by the equivalence principle, a stationary observer at a distance from a black hole will see Hawking...
  28. Matterwave

    Math vs Physics

    Which is better? Opinions? I have to say MATH is better. physicS is just so dreadfully boring. most physicists abUse the math anyway. it is Clear that mathematiKS is far superior in any possible way. if all mathematicians would start doing physics, most physical problems would have been solved...
  29. Matterwave

    Particle physics J=L+S

    I've never really been...convinced...of the statement $$\bf{J}=\bf{L}+\bf{S}$$ I've always just gone along with it, but I've never seen why this is "right". So I guess now's as good a time as any to ask. Thinking about this from a "classical" perspective (which obviously is not correct, but...
  30. Matterwave

    Path integral Quantum Mechanics

    Hi guys, I have a few questions regarding Feynman's formulation of quantum mechanics. Given the propagator K(x',t';x,t), when is this propagator equal to: $$K(x',t';x,t)=Ae^{\frac{i}{\hbar}S_{cl}(x',t';x,t)}$$ Where S_cl is the classical action evaluated along the classical path of motion...